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Carbon Quantum Dots from Amino Acids Revisited: Survey of Renewable Precursors toward High Quantum-Yield Blue and Green Fluorescence
從氨基酸重新探討碳量子點：可再生前驅體的調查以實現高量子產率的藍色和綠色螢光

Anna Kolanowska,* Grzegorz Dzido, Maciej Krzywiecki, Mateusz M. Tomczyk, Dariusz Łukowiec,
安娜·科拉諾夫斯卡，格熱戈日·季多，馬切伊·克日維茨基，馬特烏什·M·湯奇克，達里烏什·盧科維茨Szymon Ruczka, and Sławomir Boncel*
西門·魯茨卡，斯瓦沃米爾·邦策爾*

Cite This: ACS Omega 2022, 7, 41165-41176
引用此文：ACS Omega 2022, 7, 41165-41176
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Abstract 摘要

Carbon quantum dots (CQDs) were synthesized via a green, one-step hydrothermal method. As CQD precursors, nine amino acids of different structural descriptors (negatively/ positively charged in water, polar, hydrophobic, sulfur-containing, and other/complex ones) were surveyed: Asp, Cys, Gly, His, Leu, Lys, Phe, Pro, and Ser. The reactions were performed in an autoclave in the presence of citric acid at 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C} for 24 h and yielded core-shell CQDs. CQDs were comprehensively characterized by transmission electron microscopy, dynamic light scattering, Raman, UV/Vis, infrared, X-ray photoelectron spectroscopy, and fluorescence spectroscopy. At the excitation wavelength of λ ex = 350 nm λ ex = 350 nm lambda_(ex)=350nm\lambda_{\mathrm{ex}}=350 \mathrm{~nm}, Cys-, Phe-, Leu-, and Lys-based CQDs displayed the highest quantum yield blue fluorescence- 90 ± 5 , 90 ± 4 , 87 ± 5 ± 5 , 90 ± 4 , 87 ± 5 +-5,90+-4,87+-5\pm 5,90 \pm 4,87 \pm 5, and 67 ± 3 % 67 ± 3 % 67+-3%67 \pm 3 \%, respectively-superior to the conventional fluorescent dyes. Strikingly, for Lys- and Phe-CQDs, dissimilar trends in the excitation-emission wavelength relationships were identified, that is, constantly strong red shifts versus excitation wavelength-independent emission. Cys- and Lys-CQDs were water-dispersible toward the narrow unimodal distribution of hydrodynamic diameters- 0.6 and 2.5 nm , respectively. Additionally, Lys- and Cys-CQDs, with high absolute zeta potential values, formed stable aqueous colloids in a broad range of pH ( 2 , 7 pH ( 2 , 7 pH(2,7\mathrm{pH}(2,7, and 12). The results constitute important premises for water-based applications of CQDs, such as bioimaging or photocatalysis.
碳量子點（CQDs）是通過一種綠色的一步水熱法合成的。作為 CQD 前驅體，調查了九種具有不同結構描述符的氨基酸（在水中帶負/正電、極性、疏水性、含硫及其他/複雜的）：天冬氨酸、半胱氨酸、甘氨酸、組氨酸、亮氨酸、賴氨酸、苯丙氨酸、脯氨酸和絲氨酸。反應在自壓釜中進行，並在檸檬酸的存在下於 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C} 下進行 24 小時，產生了核殼 CQDs。CQDs 通過透射電子顯微鏡、動態光散射、拉曼光譜、紫外/可見光、紅外線、X 射線光電子能譜和螢光光譜進行了全面表徵。在激發波長為 λ ex = 350 nm λ ex = 350 nm lambda_(ex)=350nm\lambda_{\mathrm{ex}}=350 \mathrm{~nm} 時，基於半胱氨酸、苯丙氨酸、亮氨酸和賴氨酸的 CQDs 顯示出最高的量子產率藍色螢光-90 ± 5 , 90 ± 4 , 87 ± 5 ± 5 , 90 ± 4 , 87 ± 5 +-5,90+-4,87+-5\pm 5,90 \pm 4,87 \pm 5 和 67 ± 3 % 67 ± 3 % 67+-3%67 \pm 3 \% ，優於傳統螢光染料。值得注意的是，對於賴氨酸和苯丙氨酸 CQDs，發現了激發-發射波長關係的不同趨勢，即持續強烈的紅移與激發波長無關的發射。半胱氨酸和賴氨酸 CQDs 在水中可分散，具有狹窄的單峰水動力直徑分佈-0.6 和 2。5 奈米，分別。此外，具有高絕對電位值的賴氨酸和半胱氨酸量子點，在廣泛的 pH ( 2 , 7 pH ( 2 , 7 pH(2,7\mathrm{pH}(2,7 和 12）範圍內形成了穩定的水性膠體。這些結果為量子點的水基應用，如生物成像或光催化，提供了重要的前提。

■ INTRODUCTION ■ 介紹

Carbon quantum dots (CQDs) are fluorescent nanomolecules or nanoparticles smaller than 10 nm . 1 , 2 10 nm . 1 , 2 10nm.^(1,2)10 \mathrm{~nm} .^{1,2} The most studied 0 D CQDs consist of a more graphitized, sp 2 sp 2 sp^(2)\mathrm{sp}^{2}-carbon rich core surrounded with a 5-50 wt % amorphous shell of polar functional groups. 3 − 6 3 − 6 ^(3-6){ }^{3-6} The structure of CQDs results in their excellent solubility in water, negligible cytotoxicity, and biocompatibility, 7 7 ^(7){ }^{7} and while bearing carboxylic groups, CQDs are conveniently functionalizable. 8 8 ^(8){ }^{8} CQDs combine the unique optical properties of quantum dots (QDs) with the electronic properties of carbon (nano)materials. Importantly, CQDs display a quantum limitation effect, translating into tunable absorption and emission. 9 9 ^(9){ }^{9} It means that after excitation, the energy of the emitted photons depends on the CQD size and its molecular structure. Hence, small CQDs fluoresce in blue while the emission wavelengths increase, with the CQD diameter spanning the entire range of visible light up to infrared (IR). 10 10 ^(10){ }^{10} Theoretical calculations of the emission wavelength of pristine zigzag-edged CQDs showed that CQDs of diameters 0.5 and 2.31 nm fluoresced at 235.2 to 999.5 nm wavelengths, respectively. 11 11 ^(11){ }^{11} At the same time, altering the core-shell CQD composition by N -, S-, P-, or B-doping enhances the fluorescence quantum yield (QY). Such doping alters the energy between the lowest unoccupied (LUMO) and the highest occupied molecular orbitals (HOMO). 12 12 ^(12){ }^{12} By the interplay of CQD chemistry and morphology, it is possible to obtain fluorescence in the full spectral range from ultraviolet (UV) to near-IR (NIR). With the above characteristics, CQDs emerge as promising biosensors, 13 13 ^(13){ }^{13} imaging agents, 14 14 ^(14){ }^{14} and drug delivery systems, 15 15 ^(15){ }^{15} along with multi-modality. Due to their high electron mobility, long hot-electron lifetimes, ultrafast electron extraction, tunable band gaps, excellent electron donor/acceptor properties, and strong stable fluorescence, CQDs are considered as photocatalysts 16 , 17 16 , 17 ^(16,17){ }^{16,17} and working elements in optoelectronic devices. 18 18 ^(18){ }^{18}
碳量子點（CQDs）是小於 10 nm . 1 , 2 10 nm . 1 , 2 10nm.^(1,2)10 \mathrm{~nm} .^{1,2} 的螢光納米分子或納米顆粒。最常研究的 0D CQDs 由一個更石墨化的、 sp 2 sp 2 sp^(2)\mathrm{sp}^{2} 富碳核心組成，周圍包裹著 5-50 wt%的無定形極性官能團外殼。 3 − 6 3 − 6 ^(3-6){ }^{3-6} CQDs 的結構使其在水中的優異溶解性、微不足道的細胞毒性和生物相容性得以實現， 7 7 ^(7){ }^{7} 而且由於含有羧基，CQDs 也方便進行功能化。 8 8 ^(8){ }^{8} CQDs 結合了量子點（QDs）的獨特光學特性和碳（納米）材料的電子特性。重要的是，CQDs 顯示出量子限制效應，轉化為可調的吸收和發射。 9 9 ^(9){ }^{9} 這意味著在激發後，發射光子的能量取決於 CQD 的大小及其分子結構。因此，小型 CQDs 在藍色範圍內螢光，而隨著 CQD 直徑的增加，發射波長也隨之增加，涵蓋了可見光的整個範圍直至紅外線（IR）。 10 10 ^(10){ }^{10} 對原始鋸齒邊 CQDs 的發射波長的理論計算顯示，直徑為 0.5 和 2.31 納米的 CQDs 分別在 235.2 至 999.5 納米的波長範圍內螢光。 11 11 ^(11){ }^{11} 同時，通過 N、S、P 或 B 掺雜改變核心-殼 CQD 的組成可以增強螢光量子產率 (QY)。這種掺雜改變了最低未佔有分子軌道 (LUMO) 和最高佔有分子軌道 (HOMO) 之間的能量。 12 12 ^(12){ }^{12} 通過 CQD 化學和形態的相互作用，可以在從紫外線 (UV) 到近紅外線 (NIR) 的全光譜範圍內獲得螢光。憑藉上述特性，CQD 成為有前景的生物傳感器， 13 13 ^(13){ }^{13} 成像劑， 14 14 ^(14){ }^{14} 和藥物傳遞系統， 15 15 ^(15){ }^{15} 以及多模態。由於其高電子遷移率、長熱電子壽命、超快電子提取、可調帶隙、優秀的電子供體/受體特性和強穩定的螢光，CQD 被視為光催化劑 16 , 17 16 , 17 ^(16,17){ }^{16,17} 和光電設備中的工作元件。 18 18 ^(18){ }^{18}
CQDs can be synthesized via a bottom-up approach from renewable sources such as fruit and vegetable peels, 19 − 22 19 − 22 ^(19-22){ }^{19-22} nuts, 23 − 25 23 − 25 ^(23-25){ }^{23-25} wastes, 26 , 27 26 , 27 ^(26,27){ }^{26,27} or larger carbon (nano) materials in the top-down methods. 28 , 29 28 , 29 ^(28,29){ }^{28,29} CQDs containing mainly carbon and oxygen (and hydrogen) suffer from low QY, while N -doping is the most frequently applied strategy to improve fluorescence. This modification introduces structural defects and new energy states and increases the number of electrons in the conduction band. Therefore, well-defined, small-molecule amino acids (AAs) emerge as promising candidates for the synthetic precursors of CQDs. AAs are renewable, abundant (global volume of the AA market reached 10.3 MT in 2021), relatively inexpensive ( 110 − 1300 110 − 1300 110-1300110-1300 USD kg − 1 − 1 ^(-1){ }^{-1} ), and non-toxic. 30 30 ^(30){ }^{30} Zwitterionic and polyfunctional AAs can be variously charged depending on pH and equipped with hydrophilic (hydroxy -OH or mercapto -SH groups) or hydrophobic (aliphatic and/or aromatic) moieties, which, in turn, provides tunability of the optical properties of CQDs. 31 , 32 31 , 32 ^(31,32){ }^{31,32}
CQDs 可以通過自下而上的方法從可再生資源合成，例如水果和蔬菜的皮、 19 − 22 19 − 22 ^(19-22){ }^{19-22} 堅果、 23 − 25 23 − 25 ^(23-25){ }^{23-25} 廢料、 26 , 27 26 , 27 ^(26,27){ }^{26,27} 或者在自上而下的方法中使用較大的碳（納米）材料。 28 , 29 28 , 29 ^(28,29){ }^{28,29} 主要由碳和氧（以及氫）組成的 CQDs 受到低量子產率（QY）的影響，而氮摻雜是改善螢光的最常用策略。這種改性引入了結構缺陷和新的能量狀態，並增加了導電帶中的電子數量。因此，明確定義的小分子氨基酸（AAs）成為 CQDs 合成前驅體的有前景候選者。AAs 是可再生的，豐富的（2021 年全球氨基酸市場達到 10.3 百萬噸），相對便宜（ 110 − 1300 110 − 1300 110-1300110-1300 美元/公斤 − 1 − 1 ^(-1){ }^{-1} ），且無毒。 30 30 ^(30){ }^{30} 兩性離子和多功能的 AAs 可以根據 pH 值而帶有不同的電荷，並配備親水性（羥基 -OH 或巰基 -SH 基團）或疏水性（脂肪族和/或芳香族）基團，這反過來又提供了 CQDs 光學性質的可調性。 31 , 32 31 , 32 ^(31,32){ }^{31,32}
Here, we propose a facile and sustainable one-step hydrothermal synthesis of CQDs from various AAs (hydrophilic, hydrophobic, aromatic, and aliphatic) and citric acid (CA) as the precursors of the core and shell, respectively. Our method covers a fully controlled four-stage synthesis, that is, dehydration, polymerization, passivation, and carbonization. The as-synthesized CQDs exhibit blue to green fluorescenceexhibiting red-shifts depending on the synthetic precursorwith merits of narrow size distribution and excellent water solubility, while the excitation wavelength falls in the range of 300 to 480 nm . Importantly, using cystein, phenylalanine, and leucine-as the synthetic precursors under the optimized conditions-we show that it is possible to obtain CQDs with high QYs superior to the conventional fluorescent dyes. LysCQDs emerged as also forming stable aqueous dispersions in a broad range of pH . The overall characteristics allow us to address the key prerequisites for numerous applications.
在此，我們提出了一種簡便且可持續的一步水熱合成方法，利用各種氨基酸（親水性、疏水性、芳香性和脂肪族）和檸檬酸作為核心和外殼的前驅物。我們的方法涵蓋了完全控制的四階段合成，即脫水、聚合、鈍化和碳化。合成的碳量子點顯示出從藍色到綠色的螢光，根據合成前驅物的不同而呈現紅移，具有狹窄的尺寸分佈和優異的水溶性，激發波長範圍在 300 至 480 納米之間。重要的是，使用半胱氨酸、苯丙氨酸和亮氨酸作為在優化條件下的合成前驅物，我們展示了獲得高量子產率的碳量子點的可能性，優於傳統螢光染料。LysCQDs 也在廣泛的 pH 範圍內形成穩定的水性分散體。整體特性使我們能夠滿足多種應用的關鍵前提條件。

- MATERIALS AND METHODS - 材料與方法

Materials. Synthesis of CQDs. CA, quinine sulfate (QS), 7diethylamino-4-methylcoumarin (Coumarin 1), and AAs were purchased from Sigma-Aldrich. CQDs were synthesized using a one-step hydrothermal method. CA ( 1.5 mmol ) and AA (aspartic acid, cysteine, glycine, histidine, leucine, lysine, phenylalanine, proline, and serine) ( 1.5 mmol ) were dissolved in distilled water ( 10 mL ) ( 10 mL ) (10mL)(10 \mathrm{~mL}). The amount of water was adjusted to dissolve CA and AA at room temperature. The solution was heated in a Teflon-coated autoclave at 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C} for 24 h in a laboratory dryer. The autoclave was allowed to cool down to room temperature, and the post-reaction mixture was centrifuged at 5500 rpm for 15 min to separate the larger particles. The resulting supernatant was filtered through a 0.22 μ μ mu\mu m-syringe filter (Minisart NY hydrophilic polyamide, 25 mm ). Following purification, the solution was frozen in liquid nitrogen and lyophilized until dried.
材料。CQDs 的合成。CA、奎寧硫酸鹽（QS）、7-二乙氨基-4-甲基香豆素（香豆素 1）和氨基酸（AAs）均購自 Sigma-Aldrich。CQDs 是使用一步水熱法合成的。CA（1.5 毫摩爾）和氨基酸（天冬氨酸、半胱氨酸、甘氨酸、組氨酸、亮氨酸、賴氨酸、苯丙氨酸、脯氨酸和絲氨酸）（1.5 毫摩爾）溶解在蒸餾水中 ( 10 mL ) ( 10 mL ) (10mL)(10 \mathrm{~mL}) 。調整水的量以在室溫下溶解 CA 和氨基酸。將溶液在 Teflon 塗層的高壓鍋中加熱至 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C} ，在實驗室乾燥器中保持 24 小時。高壓鍋冷卻至室溫後，將反應後的混合物以 5500 轉/分鐘離心 15 分鐘，以分離較大的顆粒。得到的上清液通過 0.22 μ μ mu\mu 微米注射器過濾器（Minisart NY 親水性聚酰胺，25 毫米）過濾。經過純化後，將溶液在液氮中冷凍並凍乾至乾燥。
Instrumentation. The characterization of CQDs was performed by transmission electron microscopy (TEM) (S/ TEM Titan 80-300 operated at 300 kV , Field Electron and Ion Company), combustional elemental analysis (PerkinElmer 2400 Series II CHNS/O, PerkinElmer), thermogravimetric analysis (TGA) (TGA 8000, PerkinElmer), Raman (inVia Confocal Raman microscope, Renishaw), UV-Vis (HP 8452A UV-Vis Diode Array Spectrophotometer, Hewlett Packard), fluorescence spectroscopy (SpectraMax i3x, Molecular Devices and FluoroMax Plus, Horiba Scientific), Fourier-transform IR
儀器。CQDs 的特徵化是通過透射電子顯微鏡（TEM）（S/TEM Titan 80-300，操作電壓 300 kV，Field Electron and Ion Company）、燃燒元素分析（PerkinElmer 2400 系列 II CHNS/O，PerkinElmer）、熱重分析（TGA）（TGA 8000，PerkinElmer）、拉曼光譜（inVia 共焦拉曼顯微鏡，Renishaw）、紫外-可見光（HP 8452A 紫外-可見光二極管陣列分光光度計，Hewlett Packard）、螢光光譜（SpectraMax i3x，Molecular Devices 和 FluoroMax Plus，Horiba Scientific）、傅立葉變換紅外光譜。
(FT-IR) (Nicolet 6700 FT-IR, Thermo Fischer Scientific), and X-ray photoelectron spectroscopy (XPS) (PreVac EA15, PreVac). Additionally, by applying dynamic light scattering (DLS), nanoparticle size and zeta-potential were determined (Zetasizer Nano S90, Malvern Panalytical).
(FT-IR) (Nicolet 6700 FT-IR, Thermo Fischer Scientific) 和 X 射線光電子能譜 (XPS) (PreVac EA15, PreVac)。此外，通過應用動態光散射 (DLS)，確定了納米顆粒的大小和 ζ 電位 (Zetasizer Nano S90, Malvern Panalytical)。
Transmission Electron Microscopy. The nanomorphology of CQDs was determined based on TEM images collected using a transmission electron microscope S/TEM TITAN 80300. The samples were prepared by dispersion and ultrasonication of CQDs in ultrapure ethanol and then placed on a copper TEM grid with lacey carbon films ( 200 mesh).
透射電子顯微鏡。CQDs 的納米形態是根據使用透射電子顯微鏡 S/TEM TITAN 80300 收集的 TEM 影像來確定的。樣品是通過在超純乙醇中分散和超聲處理 CQDs 來製備的，然後放置在帶有蕾絲碳膜的銅 TEM 網格上（200 目）。
Combustional Elemental Analysis. A sample of CQDs (ca. 2 − 10 mg 2 − 10 mg 2-10mg2-10 \mathrm{mg} ) was accurately weighed into small tin capsules. At elevated temperatures, in the presence of excess oxygen, the organic materials combusted into CO 2 , H 2 O , SO 2 CO 2 , H 2 O , SO 2 CO_(2),H_(2)O,SO_(2)\mathrm{CO}_{2}, \mathrm{H}_{2} \mathrm{O}, \mathrm{SO}_{2}, and N x O y N x O y N_(x)O_(y)\mathrm{N}_{x} \mathrm{O}_{y} compounds (next reduced by fine copper particles in the reduction tube to N 2 N 2 N_(2)\mathrm{N}_{2} ). For quantitative analysis, CO 2 , H 2 O CO 2 , H 2 O CO_(2),H_(2)O\mathrm{CO}_{2}, \mathrm{H}_{2} \mathrm{O}, SO 2 SO 2 SO_(2)\mathrm{SO}_{2}, and N 2 N 2 N_(2)\mathrm{N}_{2} content represent carbon, hydrogen, sulfur, and nitrogen content, respectively. Oxygen content was calculated indirectly from the difference between the sample weight and the sum of the other element contents.
燃燒元素分析。將一樣 CQDs（約 2 − 10 mg 2 − 10 mg 2-10mg2-10 \mathrm{mg} ）準確稱量到小錫膠囊中。在高溫下，在過量氧氣的存在下，這些有機材料燃燒成 CO 2 , H 2 O , SO 2 CO 2 , H 2 O , SO 2 CO_(2),H_(2)O,SO_(2)\mathrm{CO}_{2}, \mathrm{H}_{2} \mathrm{O}, \mathrm{SO}_{2} 和 N x O y N x O y N_(x)O_(y)\mathrm{N}_{x} \mathrm{O}_{y} 化合物（接著在還原管中被細銅顆粒還原為 N 2 N 2 N_(2)\mathrm{N}_{2} ）。對於定量分析， CO 2 , H 2 O CO 2 , H 2 O CO_(2),H_(2)O\mathrm{CO}_{2}, \mathrm{H}_{2} \mathrm{O} 、 SO 2 SO 2 SO_(2)\mathrm{SO}_{2} 和 N 2 N 2 N_(2)\mathrm{N}_{2} 的含量分別代表碳、氫、硫和氮的含量。氧含量則是通過樣品重量與其他元素含量總和之間的差異間接計算得出的。
TGA Analysis. TGA curves were acquired under nitrogen (flow rate of 40 mL min − 1 40 mL min − 1 40mLmin^(-1)40 \mathrm{~mL} \mathrm{~min}^{-1} ). The samples ( 1 − 5 mg 1 − 5 mg 1-5mg1-5 \mathrm{mg} ) were heated in alumina crucibles up to 800 ∘ C 800 ∘ C 800^(@)C800^{\circ} \mathrm{C} at a heating rate of 20 ∘ C min − 1 ∘ C min − 1   ^(@)Cmin-1{ }^{\circ} \mathrm{C} \min ^{-1}.
TGA 分析。TGA 曲線是在氮氣下獲得的（流速為 40 mL min − 1 40 mL min − 1 40mLmin^(-1)40 \mathrm{~mL} \mathrm{~min}^{-1} ）。樣品（ 1 − 5 mg 1 − 5 mg 1-5mg1-5 \mathrm{mg} ）在鋁土礦坩埚中加熱至 800 ∘ C 800 ∘ C 800^(@)C800^{\circ} \mathrm{C} ，加熱速率為 20 ∘ C min − 1 ∘ C min − 1   ^(@)Cmin-1{ }^{\circ} \mathrm{C} \min ^{-1} 。
Raman Spectroscopy. Raman spectra were obtained at 514 nm (a green laser) with a laser power of 5 % 5 % 5%5 \%, a 2400 line per mm grating, 20 × 20 × 20 xx20 \times magnification, and an exposure time of 15 s. For each material, three accumulations were collected in three locations within the sample. The spectra were averaged and normalized to the G-band.
拉曼光譜學。拉曼光譜是在 514 納米（綠色激光）下獲得的，激光功率為 5 % 5 % 5%5 \% ，2400 條/mm 的光柵， 20 × 20 × 20 xx20 \times 倍放大，曝光時間為 15 秒。對於每種材料，在樣品的三個位置收集了三次累積數據。光譜被平均並標準化到 G 帶。
FT-IR Spectroscopy. Spectra were collected in the range of 400 − 4000 cm − 1 400 − 4000 cm − 1 400-4000cm^(-1)400-4000 \mathrm{~cm}^{-1}, with 16 scans for each sample with a resolution of 4 cm − 1 4 cm − 1 4cm^(-1)4 \mathrm{~cm}^{-1}. Lyophilized CQDs were mixed with dry KBr in an agate mortar and then pressed in an evacuable slot to form a pellet under 40 MPa pressure for 2 min using a hydraulic press.
FT-IR 光譜學。光譜在 400 − 4000 cm − 1 400 − 4000 cm − 1 400-4000cm^(-1)400-4000 \mathrm{~cm}^{-1} 範圍內收集，每個樣本進行 16 次掃描，解析度為 4 cm − 1 4 cm − 1 4cm^(-1)4 \mathrm{~cm}^{-1} 。冷凍乾燥的量子點與乾燥的 KBr 在瑪瑙研缽中混合，然後在可抽氣的槽中以 40 MPa 的壓力壓制 2 分鐘，形成顆粒。
X-ray Photoelectron Spectroscopy. XPS measurements were performed in a UHV multi-chamber experimental setup with a PreVac EA15 hemispherical electron energy analyzer fitted with a 2D multi-channel plate detector. The system base pressure was equal to 9 × 10 − 9 Pa 9 × 10 − 9 Pa 9xx10^(-9)Pa9 \times 10^{-9} \mathrm{~Pa}. An Mg − K α Mg − K α Mg-Kalpha\mathrm{Mg}-\mathrm{K} \alpha X-ray source (PreVac dual-anode XR-40B source, excitation energy of 1253.60 eV ) was used to excite the sample. Pass energy was set to 200 eV for the survey spectra collection (scanning step of 0.9 eV ) and to 100 eV for high-accuracy energy regions (scanning step of 0.06 eV ). All measurements were done with a normal take-off angle and the curved analyzer exit slit ( 0.8 × 0.8 × 0.8 xx0.8 \times 25 mm ) choice for the highest energy resolution. The binding energy scale of the analyzer was calibrated to the Au 4 f 7 / 2 Au 4 f 7 / 2 Au_(4)f_(7//2)\mathrm{Au}_{4} \mathrm{f}_{7 / 2} (84.0 eV ) region of the gold-covered sample placed at the same sample stage. 33 33 ^(33){ }^{33} The acquired spectra were fitted using CasaXPS software. The components were fitted with the sum of Gauss (30%) and Lorenz (70%) functions, while the Shirley function was applied for background subtraction.
X 射線光電子能譜。XPS 測量是在一個超高真空多腔體實驗設置中進行的，配備有 PreVac EA15 半球形電子能量分析儀和 2D 多通道板檢測器。系統的基準壓力為 9 × 10 − 9 Pa 9 × 10 − 9 Pa 9xx10^(-9)Pa9 \times 10^{-9} \mathrm{~Pa} 。使用 Mg − K α Mg − K α Mg-Kalpha\mathrm{Mg}-\mathrm{K} \alpha X 射線源（PreVac 雙陽極 XR-40B 源，激發能量為 1253.60 eV）來激發樣品。通過能量設置為 200 eV 以收集調查光譜（掃描步長為 0.9 eV），高精度能量區域設置為 100 eV（掃描步長為 0.06 eV）。所有測量均以正常的起飛角度進行，並選擇了曲面分析儀的出口狹縫（ 0.8 × 0.8 × 0.8 xx0.8 \times 25 mm）以獲得最高的能量分辨率。分析儀的束縛能量刻度已校準至 Au 4 f 7 / 2 Au 4 f 7 / 2 Au_(4)f_(7//2)\mathrm{Au}_{4} \mathrm{f}_{7 / 2} （84.0 eV）區域，該區域的金覆蓋樣品放置在同一樣品台上。 33 33 ^(33){ }^{33} 獲得的光譜使用 CasaXPS 軟件進行擬合。組件使用高斯（30%）和洛倫茲（70%）函數的總和進行擬合，同時應用 Shirley 函數進行背景扣除。
UV-Vis Spectroscopy. UV-Vis spectra were obtained in quartz cuvettes ( 2 mL ) with a 10 mm optical path at a scanning rate of 1.0 nm from 250 to 800 nm .
紫外-可見光光譜。紫外-可見光光譜是在石英比色皿（2 mL）中以 10 mm 的光路，在 250 至 800 nm 範圍內以 1.0 nm 的掃描速率獲得的。
Fluorescence Spectroscopy. The fluorescence spectra were measured under different excitation wavelengths (from 250 to 480 nm ) for 200 μ L 200 μ L 200 muL200 \mu \mathrm{~L} of the sample transferred to a clear bottom 96 -well plate (scan speed 20 nm min − 1 20 nm min − 1   20nmmin-120 \mathrm{~nm} \min ^{-1} ).
螢光光譜學。螢光光譜在不同的激發波長（從 250 到 480 納米）下測量，樣本轉移到透明底部的 96 孔板中（掃描速度 20 nm min − 1 20 nm min − 1   20nmmin-120 \mathrm{~nm} \min ^{-1} ）。
Figure 1. Skeletal molecular formulae of AAs with different structural descriptors as the CQD precursors, including the net charge in water (a) and the general synthetic pathway toward CQDs-here illustrated by the hydrothermal transformation of Asp via the four-stage decomposition (b).
圖 1. 具有不同結構描述符的氨基酸的骨架分子式，作為量子點前驅物，包括在水中的淨電荷(a)以及通往量子點的一般合成途徑-這裡通過天冬氨酸的四階段分解的水熱轉化來說明(b)。
The QY ( φ ) ( φ ) (varphi)(\varphi) of CQDs was calculated using QS ( φ = 54 % ) ( φ = 54 % ) (varphi=54%)(\varphi=54 \%) in 0.1 M H 2 SO 4 ( aq ) 0.1 M H 2 SO 4 ( aq ) 0.1MH_(2)SO_(4(aq))0.1 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4(\mathrm{aq})} and Coumarin 1 ( φ = 59 % ) 1 ( φ = 59 % ) 1(varphi=59%)1(\varphi=59 \%) in ethanol as the references by comparing the integrated photoluminescence intensity and absorbance. 34 , 35 34 , 35 ^(34,35){ }^{34,35} Samples of aqueous CQD suspensions of different concentrations were prepared by keeping the absorbance values less than 0.1 at their excitation wavelengths (similar to different CQD concentrations). Next, the integrated photoluminescence intensities for all samples were measured. The integrated photoluminescence intensity was plotted against absorbance, and the slope values of the obtained linear plots were measured. The QY was calculated using the below equation
QY ( φ ) ( φ ) (varphi)(\varphi) 的 CQDs 是通過比較整合的光致發光強度和吸收度，使用 QS ( φ = 54 % ) ( φ = 54 % ) (varphi=54%)(\varphi=54 \%) 在 0.1 M H 2 SO 4 ( aq ) 0.1 M H 2 SO 4 ( aq ) 0.1MH_(2)SO_(4(aq))0.1 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4(\mathrm{aq})} 和乙醇中的香豆素 1 ( φ = 59 % ) 1 ( φ = 59 % ) 1(varphi=59%)1(\varphi=59 \%) 作為參考來計算的。 34 , 35 34 , 35 ^(34,35){ }^{34,35} 以保持其激發波長下的吸收值低於 0.1（類似於不同的 CQD 濃度），準備了不同濃度的水相 CQD 懸浮液樣品。接下來，測量了所有樣品的整合光致發光強度。將整合的光致發光強度與吸收度繪製成圖，並測量所獲得的線性圖的斜率值。QY 是使用以下方程計算的。
φ x = φ QS ⋅ S x S QS ⋅ I QS I x ⋅ η x 2 η QS 2 φ x = φ QS ⋅ S x S QS ⋅ I QS I x ⋅ η x 2 η QS 2 varphi_(x)=varphi_(QS)*(S_(x))/(S_(QS))*(I_(QS))/(I_(x))*(eta_(x)^(2))/(eta_(QS)^(2))\varphi_{x}=\varphi_{\mathrm{QS}} \cdot \frac{S_{x}}{S_{\mathrm{QS}}} \cdot \frac{I_{\mathrm{QS}}}{I_{x}} \cdot \frac{\eta_{x}^{2}}{\eta_{\mathrm{QS}}^{2}}
where: φ φ varphi\varphi-QY; S-integrated fluorescence intensity (area under spectrum); I I II-fluorescence intensity; η η eta\eta-refractive index; and x x xx-CQD sample.
在哪裡： φ φ varphi\varphi -QY；S-綜合螢光強度（光譜下的面積）； I I II -螢光強度； η η eta\eta -折射率；以及 x x xx -CQD 樣本。
DLS Measurement. The hydrodynamic diameter and zeta potential of CQDs were measured by DLS using a monochromatic coherent He − Ne He − Ne He-Ne\mathrm{He}-\mathrm{Ne} laser with a fixed wavelength of 633 nm . The measurements were performed in triplicate for 2 mL of sample ( 1 mg mL − 1 1 mg mL − 1 1mgmL^(-1)1 \mathrm{mg} \mathrm{mL}^{-1} ) in distilled water. The zeta potential for each sample was measured for three pH values: 2.0, 7.0, and 12.0. The pH of the suspension was adjusted by adding HCl ( aq ) HCl ( aq ) HCl_((aq))\mathrm{HCl}_{(\mathrm{aq})} or NaOH ( aq ) NaOH ( aq ) NaOH_((aq))\mathrm{NaOH}_{(\mathrm{aq})}.
DLS 測量。CQDs 的水動力直徑和 ζ 電位是使用波長為 633 nm 的單色相干 He − Ne He − Ne He-Ne\mathrm{He}-\mathrm{Ne} 激光進行 DLS 測量的。對於 2 mL 的樣本 ( 1 mg mL − 1 1 mg mL − 1 1mgmL^(-1)1 \mathrm{mg} \mathrm{mL}^{-1} ) 在蒸餾水中進行了三次重複測量。每個樣本的 ζ 電位在三個 pH 值下測量：2.0、7.0 和 12.0。通過添加 HCl ( aq ) HCl ( aq ) HCl_((aq))\mathrm{HCl}_{(\mathrm{aq})} 或 NaOH ( aq ) NaOH ( aq ) NaOH_((aq))\mathrm{NaOH}_{(\mathrm{aq})} 調整懸浮液的 pH 值。

RESULTS AND DISCUSSION 結果與討論

The molecular structure of the AA substrates and the conditions represent the most important variables in the properties-by-design synthesis of CQDs. As optimized, white to yellowish mat CQD powders were synthesized via the hydrothermal method, lasting 24 h at 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C}-employing as substrates nine different AAs and CAs (as the main carbon core precursor) (Figure 1). Our synthetic protocol was inspired by numerous earlier studies. For instance, Chahal et al. proved that the application of both CA and AAs is necessary for higher yields in the CQD synthesis, displaying high QYs. 36 36 ^(36){ }^{36} Indeed, in the absence of CA, the synthesis of CQDs proceeds at low yields. The authors claimed that CA played two roles in the CQD preparation. First, CA emerged as a multifunctional compound bearing three carboxyl groups and one hydroxyl group, indicating several sites to react with AAs and also with other CA molecules. Second, CA served as a Brønsted acidic catalyst in the addition-elimination reactions.
AA 基質的分子結構和條件是 CQDs 設計合成中最重要的變數。經過優化，白色至淡黃色的 CQD 粉末是通過水熱法合成的，持續 24 小時，使用九種不同的 AA 和 CA 作為基質（作為主要碳核心前驅物）（圖 1）。我們的合成方案受到許多早期研究的啟發。例如，Chahal 等人證明了同時應用 CA 和 AA 對於提高 CQD 合成的產量是必要的，顯示出高的量子產率（QY）。事實上，在缺乏 CA 的情況下，CQDs 的合成產量較低。作者聲稱 CA 在 CQD 製備中扮演了兩個角色。首先，CA 作為一種多功能化合物，具有三個羧基和一個羥基，顯示出多個與 AA 和其他 CA 分子反應的位點。其次，CA 在加成-消除反應中作為布朗斯特酸催化劑。
Here, the rationale behind the selection of AAs was to cover their most important structural descriptors (Figure 1a). The CQD products of the synthesis from the particular AA (in the form of three-letter international codes) are denoted as AACQDs such as, for example, Phe-CQD, representing Lphenylalanine-derived CQDs. The unique colors of molecular formulae of AAs are consequently applied in the analyses and spectra throughout the entire work for the sake of clarity and unambiguity.
在這裡，選擇氨基酸的理由是涵蓋它們最重要的結構描述符（圖 1a）。來自特定氨基酸的合成產物（以三個字母的國際代碼形式）被稱為 AACQDs，例如 Phe-CQD，代表 L-苯丙氨酸衍生的 CQDs。因此，氨基酸的分子式獨特顏色在整個工作中被應用於分析和光譜，以便於清晰和明確。
AAs bear amino and carboxylic acid groups, enabling the formation of a variety of nitrogen and oxygen functionalities
氨基酸具有氨基和羧酸基團，使得能夠形成多種氮和氧的官能團
Figure 2. Structural features of the as-synthesized CQDs. TEM images of Phe-CQDs; top inset shows the particle size distribution estimated from 100 individual CQDs, and the bottom inset presents a higher magnification image showing isolated Phe-CQDs (a); combustion elemental analysis of CQDs (b); TGA curves of CQDs ©; analysis of the corresponding step-wise thermal degradation of CQDs (d); Raman spectra of CQDs at the critical regions: D-, G-, and 2D-bands (e); summary of the key Raman spectra parameters for all CQDs (f). FWHM-full width at half maximumfor D-, G-, and 2D-peaks.
圖 2. 合成的 CQDs 的結構特徵。Phe-CQDs 的透射電子顯微鏡（TEM）圖像；上方插圖顯示從 100 個單獨 CQDs 估算的粒徑分佈，下方插圖呈現更高放大倍率的圖像，顯示孤立的 Phe-CQDs（a）；CQDs 的燃燒元素分析（b）；CQDs 的熱重分析（TGA）曲線（c）；CQDs 的相應逐步熱降解分析（d）；CQDs 在關鍵區域的拉曼光譜：D、G 和 2D 帶（e）；所有 CQDs 的關鍵拉曼光譜參數摘要（f）。FWHM-全寬半最大值，針對 D、G 和 2D 峰。
within the CQD shell, while Cys also provides sulfur moieties. Upon hydrothermal synthesis, the AA molecules first assemble as a result of hydrogen bonding. Next, upon heating and subsequent dehydration, polymerization occurs, leading to a short single burst of nucleation. The resulting nuclei grow by the diffusion of solutes toward CQD surfaces. 37 37 ^(37){ }^{37} Such a mechanism describing the synthetic route for the “bottom-up” methods has been proposed by many researchers. Accordingly, synthesis of CQDs includes polymerization (polycondensation via dehydration), nucleation, carbonization, and growth. In our attempt, the polymer carbon skeleton is proposed as a crosslinking agent after dehydration, whereas upon carbonization, a
在 CQD 殼內，半胱氨酸也提供硫基團。在水熱合成過程中，AA 分子首先因氫鍵作用而組裝。接著，在加熱和隨後的脫水過程中，發生聚合，導致短暫的成核爆發。生成的核通過溶質向 CQD 表面的擴散而增長。 37 37 ^(37){ }^{37} 許多研究人員提出了這種描述“自下而上”方法合成路徑的機制。因此，CQD 的合成包括聚合（通過脫水的聚縮），成核，碳化和生長。在我們的嘗試中，聚合碳骨架被提議作為脫水後的交聯劑，而在碳化過程中，
Figure 3. XPS spectra of CQDs. Signals and their deconvolution for Asp-CQDs in the C 1s (a), O 1s (b), and N 1s BE regions ©. Signals and their deconvolution for Leu-CQDs in the C 1 s ( d ) , O 1 s ( e ) C 1 s ( d ) , O 1 s ( e ) C1s(d),O1s(e)\mathrm{C} 1 \mathrm{~s}(\mathrm{~d}), \mathrm{O} 1 \mathrm{~s}(\mathrm{e}), and N 1 s BE regions (f). Signals and their deconvolution for Cys-CQDs in the C 1 s (g), O 1s (h), N 1s (i), and S 2p BE regions (inset in i).
圖 3. CQDs 的 XPS 光譜。Asp-CQDs 在 C 1s (a)、O 1s (b)和 N 1s BE 區域(c)的信號及其解卷積。Leu-CQDs 在 C 1 s ( d ) , O 1 s ( e ) C 1 s ( d ) , O 1 s ( e ) C1s(d),O1s(e)\mathrm{C} 1 \mathrm{~s}(\mathrm{~d}), \mathrm{O} 1 \mathrm{~s}(\mathrm{e}) 和 N 1s BE 區域(f)的信號及其解卷積。Cys-CQDs 在 C 1s (g)、O 1s (h)、N 1s (i)和 S 2p BE 區域(i 的插圖)的信號及其解卷積。
fraction of the precursors is consumed to further modify the carbon core. 38 38 ^(38){ }^{38}
前驅物的部分被消耗以進一步改變碳核心。 38 38 ^(38){ }^{38}
The general morphological, compositional, and structural features of the as-synthesized CQDs were analyzed (Figure 2). The morphology and size distribution of the as-synthesized CQDs were analyzed by TEM (Figure S1). The imaging showed that CQDs were composed predominantly of quasispherical and amorphous shells (revealing a “halo-effect” at the CQD edges that are less graphitized and hence rich in sp 3 sp 3 sp^(3)\mathrm{sp}^{3} carbon atoms). The size distribution of Phe-CQDs, further selected as one of the most perspective ones in terms of high QY, was narrow, that is, in the range of 1 − 5 nm 1 − 5 nm 1-5nm1-5 \mathrm{~nm} with the abundance peak at 3 nm (as determined from the population of 100 CQDs) (Figure 2a and the insets). TEM images of other CQDs frequently showed nanoparticle agglomerates larger than 10 nm , presumably formed upon lyofilization. The selected area electron diffraction (SAED) patterns of CQDs were primarily composed of diffused rings (Figure S2). This behavior stayed in good agreement with the literature dataCQDs prepared using hydrothermal methods were generally found to be amorphous. 39 39 ^(39){ }^{39} Nevertheless, SAED analysis also revealed diffraction spots assignable to the polycrystalline graphitic areas (Figure S2). Furthermore, we have performed combustion elemental analysis of CQDs (Figure 2b), which were found to be composed mainly of carbon (from 39 wt % 39 wt % 39wt%39 \mathrm{wt} \% for Cys-CQDs to 59 wt % for the more graphitized PheCQDs). For all CQDs, the shell surface was rich in oxygen and nitrogen functional groups. The elemental oxygen content varied from 30 wt % 30 wt % 30wt%30 \mathrm{wt} \% for Phe-CQDs to 44 wt % 44 wt % 44wt%44 \mathrm{wt} \% for Asp-CQDs. In turn, the highest nitrogen content was observed for HisCQDs ( 15 wt % 15 wt % 15wt%15 \mathrm{wt} \% ) with the lowest one for Pro-CQDs ( 4.5 wt % % %\% ), which corresponds to the less pronounced gasification of the aromatic moieties for His-CQDs upon the synthesis. As predicted, in the case of Cys-CQDs, apart from carbon, oxygen, and nitrogen atoms, CQDs contained sulfur, although at as high as 10 wt % 10 wt % 10wt%10 \mathrm{wt} \% content.
合成的量子點（CQDs）的一般形態、組成和結構特徵進行了分析（圖 2）。合成的 CQDs 的形態和尺寸分佈通過透射電子顯微鏡（TEM）進行了分析（圖 S1）。成像顯示，CQDs 主要由準球形和非晶殼組成（顯示出 CQD 邊緣的“光暈效應”，這些邊緣的石墨化程度較低，因此富含 sp 3 sp 3 sp^(3)\mathrm{sp}^{3} 碳原子）。Phe-CQDs 的尺寸分佈進一步被選為在高量子產率（QY）方面最具潛力的之一，其分佈較窄，即在 1 − 5 nm 1 − 5 nm 1-5nm1-5 \mathrm{~nm} 範圍內，豐度峰值在 3 納米（根據 100 個 CQDs 的數量確定）（圖 2a 及插圖）。其他 CQDs 的 TEM 圖像經常顯示出大於 10 納米的納米顆粒聚集體，這可能是在冷凍乾燥過程中形成的。CQDs 的選區電子衍射（SAED）圖樣主要由擴散環組成（圖 S2）。這一行為與文獻數據保持良好一致，使用水熱法製備的 CQDs 通常被發現是非晶的。 39 39 ^(39){ }^{39} 然而，SAED 分析也顯示出可歸因於多晶石墨區域的衍射點（圖 S2）。 此外，我們對 CQDs 進行了燃燒元素分析（圖 2b），發現其主要成分為碳（從 39 wt % 39 wt % 39wt%39 \mathrm{wt} \% 的 Cys-CQDs 到 59 wt %的更石墨化的 PheCQDs）。所有 CQDs 的外殼表面富含氧和氮功能團。元素氧含量從 Phe-CQDs 的 30 wt % 30 wt % 30wt%30 \mathrm{wt} \% 到 Asp-CQDs 的 44 wt % 44 wt % 44wt%44 \mathrm{wt} \% 不等。反過來，HisCQDs 的氮含量最高（ 15 wt % 15 wt % 15wt%15 \mathrm{wt} \% ），而 Pro-CQDs 的氮含量最低（4.5 wt % % %\% ），這與 His-CQDs 在合成過程中芳香基團的氣化程度較低相對應。如預測的那樣，在 Cys-CQDs 的情況下，除了碳、氧和氮原子外，CQDs 還含有硫，儘管其含量高達 10 wt % 10 wt % 10wt%10 \mathrm{wt} \% 。
TGA was applied to indirectly trace the chemical nature of CQDs via thermal degradation under pyrolytic conditions (Figure 2c). Depending on the precursor, CQDs are decomposed in two or three steps (Figure 2d). The weight loss below 200 ∘ C 200 ∘ C 200^(@)C200{ }^{\circ} \mathrm{C} corresponds to the moisture evaporation, dehydration (including constitutional water), and the evolution of pyrogases ( CO 2 , CO CO 2 , CO (CO_(2),CO:}\left(\mathrm{CO}_{2}, \mathrm{CO}\right., etc.) from the CQD surface. The losses in the range of 200 − 350 ∘ C 200 − 350 ∘ C 200-350^(@)C200-350^{\circ} \mathrm{C} match the evolution of gasification products from different functional groups (hydroxyl, carboxyl, carbonyl, amide, and amine groups) from the exteriors (cores) of CQDs. 40 40 ^(40){ }^{40} The decomposition of the carbonaceous material occurred in the
TGA 被應用於通過熱降解在熱解條件下間接追蹤 CQDs 的化學性質（圖 2c）。根據前驅物的不同，CQDs 的分解分為兩步或三步（圖 2d）。低於 200 ∘ C 200 ∘ C 200^(@)C200{ }^{\circ} \mathrm{C} 的重量損失對應於水分蒸發、脫水（包括結構水）以及從 CQD 表面釋放的熱氣體 ( CO 2 , CO CO 2 , CO (CO_(2),CO:}\left(\mathrm{CO}_{2}, \mathrm{CO}\right. 等。範圍在 200 − 350 ∘ C 200 − 350 ∘ C 200-350^(@)C200-350^{\circ} \mathrm{C} 的損失與來自 CQDs 外部（核心）不同官能團（羥基、羧基、碳基、酰胺和胺基）釋放的氣化產物相匹配。 40 40 ^(40){ }^{40} 碳質材料的分解發生在
Figure 4. FT-IR spectra of Ser- (left) and Cys-CQDs (right).
圖 4. Ser-（左）和 Cys-CQDs（右）的 FT-IR 光譜。
range of 300 − 450 ∘ C 300 − 450 ∘ C 300-450^(@)C300-450^{\circ} \mathrm{C}, while scission of the aromatic nitrogen functionalities began with a plateau-like run above 550 ∘ C 550 ∘ C 550^(@)C550{ }^{\circ} \mathrm{C}; 41 41 ^(41){ }^{41} indeed, no further degradation was observed onward. The brownish to black residue content corresponded to the highly carbonized, polyaromatic core with the highest weight percentages for His- ( ∼ 40 ∼ 40 ∼40\sim 40 wt %), Lys-, Ser-, and Gly-derived CQDs (all ∼ 20 wt % ∼ 20 wt % ∼20wt%\sim 20 \mathrm{wt} \% ).
300 − 450 ∘ C 300 − 450 ∘ C 300-450^(@)C300-450^{\circ} \mathrm{C} 的範圍，而芳香氮功能的分裂在 550 ∘ C 550 ∘ C 550^(@)C550{ }^{\circ} \mathrm{C} 以上開始呈現平臺狀的運行； 41 41 ^(41){ }^{41} 確實，隨後未觀察到進一步的降解。棕色至黑色的殘留物含量對應於高度碳化的多芳香核心，His-（ ∼ 40 ∼ 40 ∼40\sim 40 wt %）、Lys-、Ser-和 Gly 衍生的 CQDs 的重量百分比最高（均為 ∼ 20 wt % ∼ 20 wt % ∼20wt%\sim 20 \mathrm{wt} \% ）。
To gain further insights into the chemistry of CQDs, Raman spectra were acquired and divided into two distinctly different regions (Figure 2e,f). The spectra showed typical graphitic features: (a) D-mode (disorder) (1350-1364 cm − 1 cm − 1 cm^(-1)\mathrm{cm}^{-1} ) activated by symmetry breaking at defects and edges, (b) G-band (graphitic) ( 1580 − 1594 cm − 1 ) 1580 − 1594 cm − 1 (1580-1594cm^(-1))\left(1580-1594 \mathrm{~cm}^{-1}\right) arising from the in-plane C − C C − C C-C\mathrm{C}-\mathrm{C} deformations, and © the second order features corresponding to 2 D , D + G 2 D , D + G 2D,D+G2 \mathrm{D}, \mathrm{D}+\mathrm{G}, and 2 G combination modes. 42 42 ^(42){ }^{42} In all cases, the intensity of the G-band was higher than that of the D-band, indicating the dominating abundance of sp 2 sp 2 sp^(2)\mathrm{sp}^{2}-, with an addition of sp 3 sp 3 sp^(3)\mathrm{sp}^{3}-carbon atoms. CQDs can thus be considered as composed of sp 2 sp 2 sp^(2)\mathrm{sp}^{2}-graphitic and sp 2 C = O sp 2 C = O sp^(2)C=O\mathrm{sp}^{2} \mathrm{C}=\mathrm{O} carbon atoms ( COOH , COO , CONH COOH , COO , CONH (COOH,COO,CONH:}\left(\mathrm{COOH}, \mathrm{COO}, \mathrm{CONH}\right., etc.), with the admixture of sp 3 sp 3 sp^(3)\mathrm{sp}^{3} carbon defects, including sp 3 sp 3 sp^(3)\mathrm{sp}^{3}-carbon-based functionalities ( > CHOH , > CHO − , > CHNH − > CHOH , > CHO − , > CHNH − ( > CHOH, > CHO-, > CHNH-:}\left(>\mathrm{CHOH},>\mathrm{CHO}-,>\mathrm{CHNH}-\right., etc.). The I D / I G I D / I G I_(D)//I_(G)I_{\mathrm{D}} / I_{\mathrm{G}} ratio identifies the nature of carbon atoms in CQDs and is typically used to determine the average size of the sp 2 sp 2 sp^(2)\mathrm{sp}^{2}-graphitic domains in carbon (nano)materials. The highest I D / I G I D / I G I_(D)//I_(G)\mathrm{I}_{\mathrm{D}} / \mathrm{I}_{\mathrm{G}} ratio, and as a consequence, the highest functionalization degrees/structural disorders and high N - and S -doping levels were observed for Cys- (0.97), Leu- (0.95), and His-CQDs (0.91). In turn, the lowest I D / I G I D / I G I_(D)//I_(G)I_{\mathrm{D}} / I_{\mathrm{G}} values were observed for Pro- (0.19) and PheCQDs ( 0.51 ) as the most ordered, that is, the least defective, hence resulting in a more aromatic/conjugated structure. Raman spectra were dependent on the measurement nanoscale position on the sample, indicating that the samples were a mixture of CQDs with different sizes and functionalization degrees. Indeed, for all CQDs, both D- and G-band frequencies have shown size-dependent trends, each one redshifted with the CQD size. The lowest G-frequency was observed for Pro-CQDs; however, it was not connected with the lowest D-frequency. This behavior may again correspond to the inhomogeneous distribution of CQD sizes. The lowest D-frequencies were observed for Lys- and His-CQDs. The differences between D - and G -frequencies were found to be higher than for Pro-CQD, which could prove that the homogeneity of size distribution for the latter one is lower. The highest D- and G-frequencies were observed for LeuCQDs, which suggests the presence of the smallest CQDs. 2DBand, which is the second-order D-band, is broader and blueshifted with the CQD size. This feature is more sensitive to the carbon core size, while the shift in D- and G-frequencies is the effect of not only the carbon core size but is also connected with higher functionalizations at the CQD core. 43 43 ^(43){ }^{43} Therefore, we can speculate that the Leu-CQD samplefeaturing high D -, G -, and 2 D frequencies - is composed of the medium size core and low molecular-weight dangling functional groups. In turn, the Phe-CQD sample with low D-, G-, and 2D frequencies contains CQDs with a small core and functional groups of higher molecular weight. 43 , 44 43 , 44 ^(43,44){ }^{43,44}
為了進一步了解量子點的化學特性，獲取了拉曼光譜並將其分為兩個明顯不同的區域（圖 2e,f）。光譜顯示出典型的石墨特徵：（a）D 模式（無序）（1350-1364 cm − 1 cm − 1 cm^(-1)\mathrm{cm}^{-1} ），由於缺陷和邊緣的對稱破壞而激活，（b）G 帶（石墨） ( 1580 − 1594 cm − 1 ) 1580 − 1594 cm − 1 (1580-1594cm^(-1))\left(1580-1594 \mathrm{~cm}^{-1}\right) ，源自平面 C − C C − C C-C\mathrm{C}-\mathrm{C} 變形，以及（c）對應於 2 D , D + G 2 D , D + G 2D,D+G2 \mathrm{D}, \mathrm{D}+\mathrm{G} 的二次特徵和 2G 組合模式。 42 42 ^(42){ }^{42} 在所有情況下，G 帶的強度高於 D 帶，表明 sp 2 sp 2 sp^(2)\mathrm{sp}^{2} -的佔主導地位，並附加了 sp 3 sp 3 sp^(3)\mathrm{sp}^{3} -碳原子。因此，量子點可以被視為由 sp 2 sp 2 sp^(2)\mathrm{sp}^{2} -石墨和 sp 2 C = O sp 2 C = O sp^(2)C=O\mathrm{sp}^{2} \mathrm{C}=\mathrm{O} 碳原子 ( COOH , COO , CONH COOH , COO , CONH (COOH,COO,CONH:}\left(\mathrm{COOH}, \mathrm{COO}, \mathrm{CONH}\right. 等組成，並混合了 sp 3 sp 3 sp^(3)\mathrm{sp}^{3} 碳缺陷，包括 sp 3 sp 3 sp^(3)\mathrm{sp}^{3} -基於碳的功能性 ( > CHOH , > CHO − , > CHNH − > CHOH , > CHO − , > CHNH − ( > CHOH, > CHO-, > CHNH-:}\left(>\mathrm{CHOH},>\mathrm{CHO}-,>\mathrm{CHNH}-\right. 等。 I D / I G I D / I G I_(D)//I_(G)I_{\mathrm{D}} / I_{\mathrm{G}} 比率識別了量子點中碳原子的性質，通常用於確定碳（納米）材料中 sp 2 sp 2 sp^(2)\mathrm{sp}^{2} -石墨域的平均大小。觀察到 Cys-（0.97）、Leu-（0.95）和 His-CQDs（0）的最高 I D / I G I D / I G I_(D)//I_(G)\mathrm{I}_{\mathrm{D}} / \mathrm{I}_{\mathrm{G}} 比率，因此，功能化程度/結構無序度和高 N-及 S-摻雜水平。91). 反過來，Pro-（0.19）和 PheCQDs（0.51）的最低 I D / I G I D / I G I_(D)//I_(G)I_{\mathrm{D}} / I_{\mathrm{G}} 值被觀察到，這是最有序的，即缺陷最少，因此導致了更具芳香性/共軛結構。拉曼光譜依賴於樣品的測量納米尺度位置，表明樣品是不同大小和功能化程度的 CQDs 的混合物。事實上，對於所有 CQDs，D 帶和 G 帶頻率均顯示出與大小相關的趨勢，每個頻率隨著 CQD 大小而紅移。Pro-CQDs 的 G 頻率最低；然而，這與最低的 D 頻率並無關聯。這種行為可能再次對應於 CQD 大小的不均勻分佈。Lys-和 His-CQDs 的 D 頻率最低。D 頻率和 G 頻率之間的差異被發現高於 Pro-CQD，這可能證明後者的大小分佈均勻性較低。LeuCQDs 的 D 頻率和 G 頻率最高，這表明存在最小的 CQDs。2DBand，即二階 D 帶，隨著 CQD 大小變寬並藍移。 此特徵對碳核心大小更為敏感，而 D 頻率和 G 頻率的變化不僅受到碳核心大小的影響，還與 CQD 核心的高功能化有關。因此，我們可以推測，具有高 D、G 和 2D 頻率的 Leu-CQD 樣品是由中等大小的核心和低分子量的懸掛功能團組成。反之，D、G 和 2D 頻率較低的 Phe-CQD 樣品則包含具有小核心和高分子量功能團的 CQD。 43 , 44 43 , 44 ^(43,44){ }^{43,44}
Figure 3 shows the decomposed XPS spectra of CQDs, most potentially from the applicability point-of-view. Figure 3a-c display XPS spectra of Asp-CQDs. Figure 3a shows the peak of photoemission for C 1 s with the main peak for the carbon atoms located at a bonding energy (BE) of ca. 285 eV . Due to the presence of sp 2 + ε sp 2 + ε sp^(2+epsi)\mathrm{sp}^{2+\varepsilon}-carbon atoms, the peak is broad with a long asymmetric tail toward higher BE values. 45 45 ^(45){ }^{45} With the effect of functionalization, the concentration of sp 3 sp 3 sp^(3)\mathrm{sp}^{3}-carbon atoms increased, which resulted in the symmetric peak at 285.5 eV . The peaks corresponding to C − N / C − C = O / CONH 2 ( 286.5 C − N / C − C = O / CONH 2 ( 286.5 C-N//C-C=O//CONH_(2)(286.5\mathrm{C}-\mathrm{N} / \mathrm{C}-\mathrm{C}=\mathrm{O} / \mathrm{CONH}_{2}(286.5 eV ) , C = O ( 287.5 eV ) eV ) , C = O ( 287.5 eV ) eV),C=O(287.5eV)\mathrm{eV}), \mathrm{C}=\mathrm{O}(287.5 \mathrm{eV}), and COOH ( 288.5 eV ) COOH ( 288.5 eV ) COOH(288.5eV)\mathrm{COOH}(288.5 \mathrm{eV}) bonds/ moieties could be assigned to the CQD surface functionalities. 45 , 46 45 , 46 ^(45,46){ }^{45,46} Figure 3b shows XPS spectra obtained in the O 1s BE region with three key peaks at 531 , 532.5 531 , 532.5 531,532.5531,532.5, and 534 eV . The peak related to the COOH and OH is observed at a BE of 534 eV , while the one attributable to CO and CONH bonds appears at 532.5 nm . The strong peak at 531 eV can be assigned to C = O C = O C=O\mathrm{C}=\mathrm{O} bonds. 45 , 47 45 , 47 ^(45,47){ }^{45,47} Figure 3 c shows the XPS in the N 1s BE region. The occurrence of the N 1s peak at 400 eV indicated the presence of CN / CONH 2 CN / CONH 2 CN//CONH_(2)\mathrm{CN} / \mathrm{CONH}_{2} groups, 45 , 47 45 , 47 ^(45,47){ }^{45,47} while the presence of C − N C − N C-N\mathrm{C}-\mathrm{N} bonds was demonstrated in the region of C 1s peak at 286.5 eV . The weak peak at 401.5 eV can be assigned to N − H N − H N-H\mathrm{N}-\mathrm{H} bonds present in the cationic moieties. 45 45 ^(45){ }^{45} Similarly, Figure 3d-f show XPS spectra for Leu-CQDs. The C 1 s spectrum (Figure 3d) consists of four contributions: 284.5, 285.5, 287.0, and 288.5 eV . The first and main contribution at 284.5 eV can be assigned to the graphitic carbon atoms. The contributions at 285.5 , 287 285.5 , 287 285.5,287285.5,287, and 288.5 eV are due to the presence of C − N / O = C − C / CONH 2 , C = O C − N / O = C − C / CONH 2 , C = O C-N//O=C-C//CONH_(2),C=O\mathrm{C}-\mathrm{N} / \mathrm{O}=\mathrm{C}-\mathrm{C} / \mathrm{CONH}_{2}, \mathrm{C}=\mathrm{O}, and COOH moieties, respectively. 4 , 47 4 , 47 ^(4,47){ }^{4,47} Figure 3e shows the peak of photoemission for O 1 s with three key peaks at 531 , 532 , and 533.5 eV . The peak related to the COOH and OH is observed at a BE of 534 eV , while the one attributable to O − C O − C O-C\mathrm{O}-\mathrm{C} and CONH 2 CONH 2 CONH_(2)\mathrm{CONH}_{2} bonds appears at 532 eV . The weak peak at 531.0 eV can be assigned to C = O C = O C=O\mathrm{C}=\mathrm{O} bonds. 45 45 ^(45){ }^{45} Figure 3f shows the XPS in the N 1s BE region, with the peaks at 400.0 and 401.5 eV belonging to N − C / CONH 2 N − C / CONH 2 N-C//CONH_(2)\mathrm{N}-\mathrm{C} / \mathrm{CONH}_{2} and N − H N − H N-H\mathrm{N}-\mathrm{H} moieties, respec-
圖 3 顯示了 CQDs 的分解 XPS 光譜，從應用的角度來看最具潛力。圖 3a-c 顯示了 Asp-CQDs 的 XPS 光譜。圖 3a 顯示了 C 1s 的光發射峰，碳原子的主要峰位於約 285 eV 的鍵能（BE）處。由於存在 sp 2 + ε sp 2 + ε sp^(2+epsi)\mathrm{sp}^{2+\varepsilon} -碳原子，該峰較寬，並且在較高 BE 值方向有一個長的非對稱尾部。 45 45 ^(45){ }^{45} 隨著功能化的影響， sp 3 sp 3 sp^(3)\mathrm{sp}^{3} -碳原子的濃度增加，這導致在 285.5 eV 處出現對稱峰。與 C − N / C − C = O / CONH 2 ( 286.5 C − N / C − C = O / CONH 2 ( 286.5 C-N//C-C=O//CONH_(2)(286.5\mathrm{C}-\mathrm{N} / \mathrm{C}-\mathrm{C}=\mathrm{O} / \mathrm{CONH}_{2}(286.5 eV ) , C = O ( 287.5 eV ) eV ) , C = O ( 287.5 eV ) eV),C=O(287.5eV)\mathrm{eV}), \mathrm{C}=\mathrm{O}(287.5 \mathrm{eV}) 和 COOH ( 288.5 eV ) COOH ( 288.5 eV ) COOH(288.5eV)\mathrm{COOH}(288.5 \mathrm{eV}) 鍵/基團相對應的峰可歸因於 CQD 表面功能性。 45 , 46 45 , 46 ^(45,46){ }^{45,46} 圖 3b 顯示了在 O 1s BE 區域獲得的 XPS 光譜，具有三個關鍵峰，分別位於 531 , 532.5 531 , 532.5 531,532.5531,532.5 和 534 eV。與 COOH 和 OH 相關的峰在 534 eV 處被觀察到，而歸因於 CO 和 CONH 鍵的峰出現在 532.5 nm。531 eV 處的強峰可歸因於 C = O C = O C=O\mathrm{C}=\mathrm{O} 鍵。 45 , 47 45 , 47 ^(45,47){ }^{45,47} 圖 3c 顯示了 N 1s BE 區域的 XPS。 N 1s 峰出現在 400 eV 表明存在 CN / CONH 2 CN / CONH 2 CN//CONH_(2)\mathrm{CN} / \mathrm{CONH}_{2} 基團， 45 , 47 45 , 47 ^(45,47){ }^{45,47} ，而 C − N C − N C-N\mathrm{C}-\mathrm{N} 鍵的存在則在 C 1s 峰的 286.5 eV 區域中顯示出來。401.5 eV 的弱峰可歸因於存在於陽離子部分的 N − H N − H N-H\mathrm{N}-\mathrm{H} 鍵。 45 45 ^(45){ }^{45} 同樣，圖 3d-f 顯示了 Leu-CQDs 的 XPS 光譜。C 1s 光譜（圖 3d）由四個貢獻組成：284.5、285.5、287.0 和 288.5 eV。284.5 eV 的第一個主要貢獻可歸因於石墨碳原子。 285.5 , 287 285.5 , 287 285.5,287285.5,287 和 288.5 eV 的貢獻分別是由於 C − N / O = C − C / CONH 2 , C = O C − N / O = C − C / CONH 2 , C = O C-N//O=C-C//CONH_(2),C=O\mathrm{C}-\mathrm{N} / \mathrm{O}=\mathrm{C}-\mathrm{C} / \mathrm{CONH}_{2}, \mathrm{C}=\mathrm{O} 和 COOH 基團的存在。 4 , 47 4 , 47 ^(4,47){ }^{4,47} 圖 3e 顯示了 O 1s 的光發射峰，具有三個關鍵峰值，分別為 531、532 和 533.5 eV。與 COOH 和 OH 相關的峰在 534 eV 的束縛能（BE）處被觀察到，而可歸因於 O − C O − C O-C\mathrm{O}-\mathrm{C} 和 CONH 2 CONH 2 CONH_(2)\mathrm{CONH}_{2} 鍵的峰出現在 532 eV。531.0 eV 的弱峰可歸因於 C = O C = O C=O\mathrm{C}=\mathrm{O} 鍵。 45 45 ^(45){ }^{45} 圖 3f 顯示了 N 1s BE 區域的 XPS，峰值在 400.0 和 401。5 eV 屬於 N − C / CONH 2 N − C / CONH 2 N-C//CONH_(2)\mathrm{N}-\mathrm{C} / \mathrm{CONH}_{2} 和 N − H N − H N-H\mathrm{N}-\mathrm{H} 基團，分別-
Figure 5. Fluorescence emission spectra of Lys- (left) with its exemplary ( λ ex = 400 nm λ ex = 400 nm lambda_(ex)=400nm\lambda_{\mathrm{ex}}=400 \mathrm{~nm} ) deconvolution (middle) and Phe-CQDs (right) at different excitation wavelengths (ranging from 300 to 480 nm ).
圖 5. 在不同激發波長（範圍從 300 到 480 納米）下，Lys-（左）及其示例性（ λ ex = 400 nm λ ex = 400 nm lambda_(ex)=400nm\lambda_{\mathrm{ex}}=400 \mathrm{~nm} ）去卷積（中）和 Phe-CQDs（右）的螢光發射光譜。
tively. 45 , 47 45 , 47 ^(45,47){ }^{45,47} XPS spectra shown in Figure 3g-i clearly revealed that carbon, nitrogen, sulfur, and oxygen are present at the Cys-CQD surface. In the decomposed XPS spectra, the C 1s peaks at 284, 285, 285.5, 286.5, and 288.5 eV shown in Figure 3 g can be assigned to carbon in the form of C − C / C − H , C − S C − C / C − H , C − S C-C//C-H,C-S\mathrm{C}-\mathrm{C} / \mathrm{C}-\mathrm{H}, \mathrm{C}-\mathrm{S}, C − N / O = C − C / CONH 2 C = O C − N / O = C − C / CONH 2 C = O C-N//O=C-C//CONH_(2)C=O\mathrm{C}-\mathrm{N} / \mathrm{O}=\mathrm{C}-\mathrm{C} / \mathrm{CONH}_{2} \mathrm{C}=\mathrm{O}, and COOH 45 , 47 COOH 45 , 47 COOH^(45,47)\mathrm{COOH}^{45,47} The O 1 s peaks (Figure 3h) at 531.0 , 532.5 531.0 , 532.5 531.0,532.5531.0,532.5, and 534.0 eV are associated with oxygen in the states of O = C , O − C / CONH 2 O = C , O − C / CONH 2 O=C,O-C//CONH_(2)\mathrm{O}=\mathrm{C}, \mathrm{O}-\mathrm{C} / \mathrm{CONH}_{2}, and COOH / OH COOH / OH COOH//OH\mathrm{COOH} / \mathrm{OH}, respectively. 45 45 ^(45){ }^{45} The N 1s peaks at 400 and 402 eV shown in Figure 3i indicate that nitrogen occurs mostly in the form of N − C / CONH 2 N − C / CONH 2 N-C//CONH_(2)\mathrm{N}-\mathrm{C} / \mathrm{CONH}_{2} and N − H N − H N-H\mathrm{N}-\mathrm{H}. The S 2 p spectrum in Figure 3i (inset) shows a broad peak at ∼ 164 eV ∼ 164 eV ∼164eV\sim 164 \mathrm{eV}, originating from C − S C − S C-S\mathrm{C}-\mathrm{S} and S − H S − H S-H\mathrm{S}-\mathrm{H} bonds with their spin-orbit splitting (separation of 1.18 eV ) counterparts. 48 , 49 48 , 49 ^(48,49){ }^{48,49}
XPS 光譜如圖 3g-i 所示，清楚顯示出碳、氮、硫和氧存在於 Cys-CQD 表面。在分解的 XPS 光譜中，圖 3g 中的 C 1s 峰值在 284、285、285.5、286.5 和 288.5 eV 可歸因於以 C − C / C − H , C − S C − C / C − H , C − S C-C//C-H,C-S\mathrm{C}-\mathrm{C} / \mathrm{C}-\mathrm{H}, \mathrm{C}-\mathrm{S} 、 C − N / O = C − C / CONH 2 C = O C − N / O = C − C / CONH 2 C = O C-N//O=C-C//CONH_(2)C=O\mathrm{C}-\mathrm{N} / \mathrm{O}=\mathrm{C}-\mathrm{C} / \mathrm{CONH}_{2} \mathrm{C}=\mathrm{O} 和 COOH 45 , 47 COOH 45 , 47 COOH^(45,47)\mathrm{COOH}^{45,47} 形式存在的碳。圖 3h 中的 O 1s 峰值在 531.0 , 532.5 531.0 , 532.5 531.0,532.5531.0,532.5 和 534.0 eV 與氧在 O = C , O − C / CONH 2 O = C , O − C / CONH 2 O=C,O-C//CONH_(2)\mathrm{O}=\mathrm{C}, \mathrm{O}-\mathrm{C} / \mathrm{CONH}_{2} 和 COOH / OH COOH / OH COOH//OH\mathrm{COOH} / \mathrm{OH} 狀態下相關。圖 3i 中的 N 1s 峰值在 400 和 402 eV 顯示氮主要以 N − C / CONH 2 N − C / CONH 2 N-C//CONH_(2)\mathrm{N}-\mathrm{C} / \mathrm{CONH}_{2} 和 N − H N − H N-H\mathrm{N}-\mathrm{H} 形式存在。圖 3i（插圖）中的 S 2p 光譜顯示在 ∼ 164 eV ∼ 164 eV ∼164eV\sim 164 \mathrm{eV} 處有一個寬峰，源自 C − S C − S C-S\mathrm{C}-\mathrm{S} 和 S − H S − H S-H\mathrm{S}-\mathrm{H} 鍵及其自旋-軌道分裂（1.18 eV 的分離）對應物。
FT-IR spectra (Figure 4) were used to further identify the functionalities in CQDs. The broad band in the range 3000 3500 cm − 1 3500 cm − 1 3500cm^(-1)3500 \mathrm{~cm}^{-1} can be attributed to stretching vibrations of O − H 50 O − H 50 O-H^(50)\mathrm{O}-\mathrm{H}^{50} and N − H 51 N − H 51 N-H^(51)\mathrm{N}-\mathrm{H}^{51} groups. The band at 3042 cm − 1 3042 cm − 1 3042cm^(-1)3042 \mathrm{~cm}^{-1} corresponds to the stretching vibrations of C − H C − H C-H\mathrm{C}-\mathrm{H} in the aromatic species 52 52 ^(52){ }^{52} while at 2966 cm − 1 2966 cm − 1 2966cm^(-1)2966 \mathrm{~cm}^{-1} in the aliphatic species. 53 53 ^(53){ }^{53} The strong absorption band at 1636 cm − 1 1636 cm − 1 1636cm^(-1)1636 \mathrm{~cm}^{-1} corresponds to the stretching vibrations of carbonyl ( C = O ) ( C = O ) (C=O)(\mathrm{C}=\mathrm{O}) groups. 54 54 ^(54){ }^{54} The absorption peak at 1591 cm − 1 1591 cm − 1 1591cm^(-1)1591 \mathrm{~cm}^{-1} belongs to the C − N C − N C-N\mathrm{C}-\mathrm{N} stretching vibration, 55 55 ^(55){ }^{55} while the peaks at 1570,1467 , and 1494 and 1340 cm − 1 1340 cm − 1 1340cm^(-1)1340 \mathrm{~cm}^{-1} can be assigned to the stretching vibrations of C = C C = C C=C\mathrm{C}=\mathrm{C} and bending vibrations of C − H . 54 C − H . 54 C-H.^(54)\mathrm{C}-\mathrm{H} .{ }^{54} The bands appear at 1314, 1255, and 1143 cm − 1 1143 cm − 1 1143cm^(-1)1143 \mathrm{~cm}^{-1}, indicating the presence of the C − O C − O C-O\mathrm{C}-\mathrm{O} stretching mode and the bending vibrations of NH 2 ⋅ 53 , 56 , 57 NH 2 ⋅ 53 , 56 , 57 NH_(2)*^(53,56,57)\mathrm{NH}_{2} \cdot{ }^{53,56,57} Those bands (with only small shifts) are observed for all CQD samples (Figure S3). The presence of the C = C C = C C=C\mathrm{C}=\mathrm{C} peak indicates that CQDs could also be composed of a fraction of the polycrystalline graphitic domains (referring back to SAED, Figure S2), whereas the other signals were assignable to -OH , C = O , C − N , N − H C = O , C − N , N − H C=O,C-N,N-H\mathrm{C}=\mathrm{O}, \mathrm{C}-\mathrm{N}, \mathrm{N}-\mathrm{H}, and C − H C − H C-H\mathrm{C}-\mathrm{H} functionalities. Many different vibrations were also found in the fingerprint regions, including C − O , C − N , C − C C − O , C − N , C − C C-O,C-N,C-C\mathrm{C}-\mathrm{O}, \mathrm{C}-\mathrm{N}, \mathrm{C}-\mathrm{C} bond stretches, and C − H C − H C-H\mathrm{C}-\mathrm{H} deformation vibrations. For Cys-CQDs, a specific but relatively weak band at 2551 cm − 1 2551 cm − 1 2551cm^(-1)2551 \mathrm{~cm}^{-1} appears, conforming to the stretching vibrations of S − H S − H S-H\mathrm{S}-\mathrm{H} bonds. 58 58 ^(58){ }^{58} Importantly, the concentration of the functional groups affects the fluorescence properties. Moieties like -CO and -COOH can reduce the energy gap and, therefore, red-shift the emission wavelength and reduce the QY . On the other hand, -OH groups can stabilize the surface sites, hence increasing the QY. Amino groups act as donors, transferring the electrons to the carbon core and stabilizing the emissive energy traps, increasing the QY. 59 59 ^(59){ }^{59}
FT-IR 光譜（圖 4）被用來進一步識別 CQDs 中的功能性。範圍在 3000 3500 cm − 1 3500 cm − 1 3500cm^(-1)3500 \mathrm{~cm}^{-1} 的寬帶可歸因於 O − H 50 O − H 50 O-H^(50)\mathrm{O}-\mathrm{H}^{50} 和 N − H 51 N − H 51 N-H^(51)\mathrm{N}-\mathrm{H}^{51} 基團的伸縮振動。位於 3042 cm − 1 3042 cm − 1 3042cm^(-1)3042 \mathrm{~cm}^{-1} 的帶對應於芳香物種 52 52 ^(52){ }^{52} 中 C − H C − H C-H\mathrm{C}-\mathrm{H} 的伸縮振動，而在脂肪物種的 2966 cm − 1 2966 cm − 1 2966cm^(-1)2966 \mathrm{~cm}^{-1} 中。 53 53 ^(53){ }^{53} 在 1636 cm − 1 1636 cm − 1 1636cm^(-1)1636 \mathrm{~cm}^{-1} 的強吸收帶對應於羰基 ( C = O ) ( C = O ) (C=O)(\mathrm{C}=\mathrm{O}) 基團的伸縮振動。 54 54 ^(54){ }^{54} 在 1591 cm − 1 1591 cm − 1 1591cm^(-1)1591 \mathrm{~cm}^{-1} 的吸收峰屬於 C − N C − N C-N\mathrm{C}-\mathrm{N} 的伸縮振動， 55 55 ^(55){ }^{55} ，而在 1570、1467 和 1494 及 1340 cm − 1 1340 cm − 1 1340cm^(-1)1340 \mathrm{~cm}^{-1} 的峰可歸因於 C = C C = C C=C\mathrm{C}=\mathrm{C} 的伸縮振動和 C − H . 54 C − H . 54 C-H.^(54)\mathrm{C}-\mathrm{H} .{ }^{54} 的彎曲振動。帶出現在 1314、1255 和 1143 cm − 1 1143 cm − 1 1143cm^(-1)1143 \mathrm{~cm}^{-1} ，顯示出 C − O C − O C-O\mathrm{C}-\mathrm{O} 的伸縮模式和 NH 2 ⋅ 53 , 56 , 57 NH 2 ⋅ 53 , 56 , 57 NH_(2)*^(53,56,57)\mathrm{NH}_{2} \cdot{ }^{53,56,57} 的彎曲振動的存在。這些帶（僅有小的位移）在所有 CQD 樣本中均有觀察到（圖 S3）。 C = C C = C C=C\mathrm{C}=\mathrm{C} 峰的存在表明 CQDs 也可能由一部分多晶石墨域組成（參考 SAED，圖 S2），而其他信號可歸因於 -OH、 C = O , C − N , N − H C = O , C − N , N − H C=O,C-N,N-H\mathrm{C}=\mathrm{O}, \mathrm{C}-\mathrm{N}, \mathrm{N}-\mathrm{H} 和 C − H C − H C-H\mathrm{C}-\mathrm{H} 功能性。 在指紋區域中也發現了許多不同的振動，包括 C − O , C − N , C − C C − O , C − N , C − C C-O,C-N,C-C\mathrm{C}-\mathrm{O}, \mathrm{C}-\mathrm{N}, \mathrm{C}-\mathrm{C} 鍵伸縮和 C − H C − H C-H\mathrm{C}-\mathrm{H} 變形振動。對於 Cys-CQDs，出現了一個特定但相對較弱的帶在 2551 cm − 1 2551 cm − 1 2551cm^(-1)2551 \mathrm{~cm}^{-1} ，符合 S − H S − H S-H\mathrm{S}-\mathrm{H} 鍵的伸縮振動。 58 58 ^(58){ }^{58} 重要的是，官能團的濃度影響螢光特性。像-CO 和-COOH 這樣的基團可以降低能隙，因此使發射波長紅移並降低量子產率（QY）。另一方面，-OH 基團可以穩定表面位點，從而增加 QY。氨基作為供體，將電子轉移到碳核心並穩定發光能量陷阱，增加 QY。 59 59 ^(59){ }^{59}
The optical properties of CQDs were evaluated by UV-Vis and fluorescence spectroscopy. All CQDs exhibited a strong absorption shoulder at 220 − 230 nm 220 − 230 nm 220-230nm220-230 \mathrm{~nm} attributed to π − π ∗ π − π ∗ pi-pi^(**)\pi-\pi^{*} electron transition of the aromatic domains in the C = C C = C C=C\mathrm{C}=\mathrm{C} and C = N C = N C=N\mathrm{C}=\mathrm{N} bonds. In addition, the peaks at 300 nm are due to the n − π ∗ n − π ∗ n-pi^(**)\mathrm{n}-\pi^{*} transition in the π π pi\pi-conjugated structure. As all types of CQDs displayed a slight absorption at 350 nm due to the n − π ∗ n − π ∗ n-pi^(**)\mathrm{n}-\pi^{*} electron transition of the C = O C = O C=O\mathrm{C}=\mathrm{O} groups, the fluorescence spectra were recorded for different excitation wavelengths. Upon UV irradiation ( λ = 365 nm ) ( λ = 365 nm ) (lambda=365nm)(\lambda=365 \mathrm{~nm}), bright fluorescence was observed for all CQDs, and the color of the CQD dispersions changed from yellowish to bright blue. Depending on the CQD precursor, the excitation-emission spectra typically showed a strong red-shift due to differences in the degree of surface oxidation and also an increase in the number of surface defects (Figure S4). 60 60 ^(60){ }^{60} Along with a change in the AA precursor, the photoluminescence peak of CQDs shifted from approximately 420 nm for Leu-CQDs to 450 nm for Phe-CQDs (for the excitation wavelength of 350 nm ); yet, FWHM is rather high.
CQDs 的光學性質通過紫外-可見光和螢光光譜進行評估。所有 CQDs 在 220 − 230 nm 220 − 230 nm 220-230nm220-230 \mathrm{~nm} 處顯示出強烈的吸收肩峰，這歸因於 π − π ∗ π − π ∗ pi-pi^(**)\pi-\pi^{*} 芳香域中的電子躍遷，涉及 C = C C = C C=C\mathrm{C}=\mathrm{C} 和 C = N C = N C=N\mathrm{C}=\mathrm{N} 鍵。此外，300 nm 處的峰值是由於 n − π ∗ n − π ∗ n-pi^(**)\mathrm{n}-\pi^{*} 在 π π pi\pi -共軛結構中的躍遷。由於所有類型的 CQDs 在 350 nm 處顯示出輕微的吸收，這是由於 n − π ∗ n − π ∗ n-pi^(**)\mathrm{n}-\pi^{*} 的電子躍遷，涉及 C = O C = O C=O\mathrm{C}=\mathrm{O} 基團，因此對不同激發波長記錄了螢光光譜。在紫外線照射下 ( λ = 365 nm ) ( λ = 365 nm ) (lambda=365nm)(\lambda=365 \mathrm{~nm}) ，所有 CQDs 均顯示出明亮的螢光，且 CQD 分散液的顏色從淡黃色變為明亮的藍色。根據 CQD 前驅體，激發-發射光譜通常顯示出強烈的紅移，這是由於表面氧化程度的差異以及表面缺陷數量的增加（圖 S4）。 60 60 ^(60){ }^{60} 隨著 AA 前驅體的變化，CQDs 的光致發光峰從 Leu-CQDs 的約 420 nm 移至 Phe-CQDs 的 450 nm（激發波長為 350 nm）；然而，FWHM 相對較高。
For most samples, for example, Lys-CQDs (Figure 5, left), the emission wavelength could be related to the excitation wavelength; that is, along with the changed excitation wavelength from 300 to 480 nm . The photoluminescence peak of the Lys-CQDs was constantly red-shifted.
對於大多數樣本，例如 Lys-CQDs（圖 5，左側），發射波長可以與激發波長相關；也就是說，隨著激發波長從 300 nm 變化到 480 nm，Lys-CQDs 的光致發光峰不斷紅移。
This excitation-dependent photoluminescence behavior has been extensively reported in fluorescent carbon-based nanomaterials, which might be due to the optical selection of differently sized CQDs and the interactions between the surface functionalities and the C -sp 2 2 ^(2){ }^{2}-core. 61 61 ^(61){ }^{61} A completely different scenario was observed for Phe-CQDs (Figure 5, right), which showed changes in the fluorescence intensity when the excitation wavelength was increased, while the position of the fluorescence peak was redshifted, but to a constant position. Moreover, the spectra for excitationdependent Lys-CQDs exhibited a broader emission peak than for the excitation-wavelength-independent Phe-CQDs. Deconvolution of the fluorescence spectra of Lys-CQDs (Figure 5, middle) revealed that the broad bands could actually be the combination of two or more bands with different fluorescence maxima. This phenomenon again confirms that one deals with a mixture of CQDs, and there are more types of excitation energies trapped on the surface of CQDs.
這種依賴於激發的光致發光行為在螢光碳基納米材料中已被廣泛報導，這可能是由於不同大小的碳量子點（CQDs）的光學選擇以及表面功能性與 C -sp 2 2 ^(2){ }^{2} -核心之間的相互作用。對於 Phe-CQDs（圖 5，右側），觀察到完全不同的情況，當激發波長增加時，螢光強度發生變化，而螢光峰的位置則紅移，但保持在一個恆定的位置。此外，依賴於激發的 Lys-CQDs 的光譜顯示出比不依賴於激發波長的 Phe-CQDs 更寬的發射峰。對 Lys-CQDs 的螢光光譜進行解卷積（圖 5，中間）顯示，這些寬帶實際上可能是兩個或更多具有不同螢光最大值的帶的組合。這一現象再次證實了我們處理的是一種 CQDs 的混合物，並且有更多類型的激發能量被困在 CQDs 的表面。
QY has been measured following the reported protocols using QS as the reference (Table 1). QY can be correlated with
QY 已按照報告的協議進行測量，並以 QS 作為參考（表 1）。QY 可以與...相關聯。
Table 1. Fluorescence ( λ ex = 350 nm λ ex = 350 nm lambda_(ex)=350nm\lambda_{\mathrm{ex}}=350 \mathrm{~nm} ) of CQDs versus References
表 1. CQDs 的螢光 ( λ ex = 350 nm λ ex = 350 nm lambda_(ex)=350nm\lambda_{\mathrm{ex}}=350 \mathrm{~nm} ) 與參考文獻的比較
compound/AA-CQD 化合物/AA-CQD λ em , nm λ em  , nm lambda_("em "),nm\lambda_{\text {em }}, \mathrm{nm} QY, % a % a %^(a)\%^{a} QY， % a % a %^(a)\%^{a} QY, b b ^(b){ }^{b} QY， b b ^(b){ }^{b}
Cys 419 90 ± 5 90 ± 5 90+-590 \pm 5 86 ± 7 86 ± 7 86+-786 \pm 7
Lys 莉絲 420 67 ± 3 67 ± 3 67+-367 \pm 3 63 ± 1 63 ± 1 63+-163 \pm 1
His 他的 410 50 ± 3 50 ± 3 50+-350 \pm 3 48 ± 5 48 ± 5 48+-548 \pm 5
Ser 是 430 32 ± 2 32 ± 2 32+-232 \pm 2 30 ± 4 30 ± 4 30+-430 \pm 4
Gly 甘露糖 418 55 ± 4 55 ± 4 55+-455 \pm 4 52 ± 2 52 ± 2 52+-252 \pm 2
Pro 專業 418 14 ± 1 14 ± 1 14+-114 \pm 1 13 ± 1 13 ± 1 13+-113 \pm 1
Phe 菲 425 90 ± 4 90 ± 4 90+-490 \pm 4 85 ± 6 85 ± 6 85+-685 \pm 6
Asp 蛇毒 413 20 ± 2 20 ± 2 20+-220 \pm 2 19 ± 1 19 ± 1 19+-119 \pm 1
Leu 409 87 ± 5 87 ± 5 87+-587 \pm 5 83 ± 4 83 ± 4 83+-483 \pm 4
compound/AA-CQD lambda_("em "),nm QY, %^(a) QY, ^(b) Cys 419 90+-5 86+-7 Lys 420 67+-3 63+-1 His 410 50+-3 48+-5 Ser 430 32+-2 30+-4 Gly 418 55+-4 52+-2 Pro 418 14+-1 13+-1 Phe 425 90+-4 85+-6 Asp 413 20+-2 19+-1 Leu 409 87+-5 83+-4| compound/AA-CQD | $\lambda_{\text {em }}, \mathrm{nm}$ | QY, $\%^{a}$ | QY, ${ }^{b}$ | | :---: | :---: | :---: | :---: | | Cys | 419 | $90 \pm 5$ | $86 \pm 7$ | | Lys | 420 | $67 \pm 3$ | $63 \pm 1$ | | His | 410 | $50 \pm 3$ | $48 \pm 5$ | | Ser | 430 | $32 \pm 2$ | $30 \pm 4$ | | Gly | 418 | $55 \pm 4$ | $52 \pm 2$ | | Pro | 418 | $14 \pm 1$ | $13 \pm 1$ | | Phe | 425 | $90 \pm 4$ | $85 \pm 6$ | | Asp | 413 | $20 \pm 2$ | $19 \pm 1$ | | Leu | 409 | $87 \pm 5$ | $83 \pm 4$ |
a QS a QS ^(a)QS{ }^{a} \mathrm{QS} as a standard ( QY = 54 % , λ em = 439 nm ) . b QY = 54 % , λ em = 439 nm . b (QY=54%,lambda_(em)=439(nm)).^(b)\left(\mathrm{QY}=54 \%, \lambda_{\mathrm{em}}=439 \mathrm{~nm}\right) .{ }^{b} Coumarin 1 as a standard ( QY = 59 % ; λ em = 445 nm ) QY = 59 % ; λ em = 445 nm (QY=59%;lambda_(em)=445(nm))\left(\mathrm{QY}=59 \% ; \lambda_{\mathrm{em}}=445 \mathrm{~nm}\right).
a QS a QS ^(a)QS{ }^{a} \mathrm{QS} 作為標準 ( QY = 54 % , λ em = 439 nm ) . b QY = 54 % , λ em = 439 nm . b (QY=54%,lambda_(em)=439(nm)).^(b)\left(\mathrm{QY}=54 \%, \lambda_{\mathrm{em}}=439 \mathrm{~nm}\right) .{ }^{b} 香豆素 1 作為標準 ( QY = 59 % ; λ em = 445 nm ) QY = 59 % ; λ em = 445 nm (QY=59%;lambda_(em)=445(nm))\left(\mathrm{QY}=59 \% ; \lambda_{\mathrm{em}}=445 \mathrm{~nm}\right) 。
the chemical character of AAs. Hydrophobic AA precursors like Cys, Phe, and Leu yielded CQDs of the highest QY. The lowest QY was found for hydrophilic Ser- and Asp-CQDs. Interestingly, a QY similar to that of Ser-CQDs and Asp-CQDs was determined for hydrophobic Pro-CQDs. The lower QYvalue in this case can be connected to the smaller volume of the side chain. This is probably also the reason why the CQD derived from Leu containing a branched chain displayed a higher QY than the Gly-CQD.
氨基酸的化學特性。疏水性氨基酸前體如半胱氨酸、苯丙氨酸和亮氨酸產生的量子產率最高。親水性絲氨酸和天冬氨酸的量子產率最低。有趣的是，疏水性脯氨酸的量子產率與絲氨酸和天冬氨酸的量子產率相似。在這種情況下，較低的量子產率可以與側鏈的較小體積相關聯。這也可能是為什麼來自含有支鏈的亮氨酸的量子點顯示出比甘氨酸量子點更高的量子產率的原因。
For Cys-CQD, one can observe a higher QY due to the presence of sulfur as the doping heteroatom. The existence of sulfur could introduce defect sites, which alters the energy states and creates additional transition ways for electrons in the band structure of CQDs; or due to the similar electronegativity of carbon and sulfur, sulfur atoms could replace some of the carbon atoms in the core, resulting in high QYs. 62 62 ^(62){ }^{62} Those results agree with the literature data (Table 2). The hydrophobic character and larger volume of the side chains generally enhance the QY. The aromatic moiety hinders the interactions with polar solvents and, as a consequence, simplifies the electronic transition from HOMO to LUMO within. Similarly, hydrophilic side chains increase the interaction strength, with polar solvents reducing the extent of electronic transitions and hence QY.
對於 Cys-CQD，可以觀察到由於硫作為摻雜異質原子的存在，導致較高的量子產率（QY）。硫的存在可能引入缺陷位點，改變能量狀態並為 CQDs 的能帶結構中的電子創造額外的躍遷途徑；或者由於碳和硫的電負性相似，硫原子可能取代核心中的一些碳原子，從而導致高 QY。這些結果與文獻數據（表 2）一致。側鏈的疏水性特徵和較大體積通常增強 QY。芳香基團阻礙了與極性溶劑的相互作用，因此簡化了從 HOMO 到 LUMO 的電子躍遷。同樣，親水性側鏈增強了相互作用強度，極性溶劑減少了電子躍遷的程度，從而降低了 QY。
Table 2 shows that AAs were frequently used as the synthetic precursors of CQDs. Nevertheless, most of the studies focused on the applications of CQDs (antibacterial agents, 66 66 ^(66){ }^{66} sensors of toxic metal ions 67 67 ^(67){ }^{67} or rutin, 69 69 ^(69){ }^{69} and cellular imaging agents 70 70 ^(70){ }^{70} ) rather than on the structural differences between CQDs and their origins. The role of the functional group was studied by Hsu and Chang, 37 37 ^(37){ }^{37} while Gly was used as the only AA CQD synthetic precursor. Despite this, they found that AAs were promising candidates for the synthesis of watersoluble and photoluminescent CQDs. These results became an inspiration for other researchers. Similar trends were indicated by Jiang et al. 68 68 ^(68){ }^{68} Sahiner et al. prepared CQDs using a microwave assisted method. For the synthesis of CQDs, they used two types of AAs: those with positively charged side chains (Arg, Lys, and His) and those containing sulfur (Cys and Met). Cys-CQDs displayed the highest QY; however, no prospective results were achieved for Met-CQDs. This is probably a consequence of the insufficient incorporation of - SH groups into the CQD structure. For Cys-CQDs, the zeta potential was negative because of the presence of thiols of the lowest isoelectric point. For Met-CQDs, this value was positive, which may suggest a lower functionalization with -SH groups. This, in turn, can be connected with the lower S/ C mass ratio and a higher thermal stability for Met. 63 63 ^(63){ }^{63} Yan et al. designed CQDs exhibiting three excitation peaks and excitation-independent emission. Apart from Trp and Gly, glucose was used as the precursor, and CQDs were tested toward the selective detection of Al 3 + Al 3 + Al^(3+)\mathrm{Al}^{3+}. 64 64 ^(64){ }^{64} The most comprehensive studies of CQDs synthesized using AAs were performed by Pandit et al., 65 65 ^(65){ }^{65} where CQDs were synthesized via a hydrothermal method in the presence of CA. Nonetheless, it should be emphasized that the QY for the so-obtained CQDs is far from the results presented in our work. The differences in QY could be the consequence of the proposed mechanism of
表 2 顯示，氨基酸（AAs）經常被用作碳量子點（CQDs）的合成前驅體。然而，大多數研究集中在 CQDs 的應用（抗菌劑、毒性金屬離子的傳感器或芦丁，以及細胞成像劑）上，而不是 CQDs 及其來源之間的結構差異。Hsu 和 Chang 研究了功能團的作用，而甘氨酸（Gly）被用作唯一的氨基酸 CQD 合成前驅體。儘管如此，他們發現氨基酸是合成水溶性和光致發光 CQDs 的有前景的候選者。這些結果成為其他研究者的靈感。江等人也顯示出類似的趨勢。Sahiner 等人使用微波輔助方法製備 CQDs。為了合成 CQDs，他們使用了兩種類型的氨基酸：帶有正電荷側鏈的氨基酸（精氨酸、賴氨酸和組氨酸）和含硫的氨基酸（半胱氨酸和蛋氨酸）。半胱氨酸-CQDs 顯示出最高的量子產率；然而，蛋氨酸-CQDs 未能取得預期的結果。這可能是由於- SH 基團在 CQD 結構中的不充分掺入所致。 對於 Cys-CQDs，因為存在最低等電點的硫醇，ζ電位為負。對於 Met-CQDs，這個值為正，這可能表明其-SH 基團的功能化程度較低。這反過來可以與較低的 S/C 質量比和 Met 的較高熱穩定性相關聯。 63 63 ^(63){ }^{63} Yan 等人設計了顯示三個激發峰和激發無關發射的 CQDs。除了 Trp 和 Gly 外，還使用了葡萄糖作為前驅體，並對 CQDs 進行了選擇性檢測的測試 Al 3 + Al 3 + Al^(3+)\mathrm{Al}^{3+} 。 64 64 ^(64){ }^{64} Pandit 等人進行了使用氨基酸合成 CQDs 的最全面研究， 65 65 ^(65){ }^{65} 其中 CQDs 是在 CA 存在下通過水熱法合成的。然而，應強調的是，所獲得 CQDs 的量子產率遠低於我們工作的結果。QY 的差異可能是所提出機制的結果
Table 2. Comparison of CQDs Prepared from Various AAs a a ^(a){ }^{a}
表 2. 不同氨基酸製備的量子點比較 a a ^(a){ }^{a}
AAs conditions 條件
 粒子大小，納米
particle
size, nm
particle size, nm| particle | | :--- | | size, nm |
 ζ電位，毫伏 (mV)
zeta potential,
mV
zeta potential, mV| zeta potential, | | :--- | | mV |

激發波長，納米
excitation
wavelength, nm
excitation wavelength, nm| excitation | | :--- | | wavelength, nm |
 QY, % QY，%
 發射波長，納米
emission wavelength,
nm
emission wavelength, nm| emission wavelength, | | :--- | | nm |
 ref 參考
Arg, Lys, His, Cys, Met
阿根廷，賴氨酸，組氨酸，半胱氨酸，甲硫氨酸

微波法，700 瓦， 1 − 4 min , + CA 1 − 4 min , + CA 1-4min,+CA1-4 \mathrm{~min},+\mathrm{CA}
Microwave method, 700 W ,
1 − 4 min , + CA 1 − 4 min , + CA 1-4min,+CA1-4 \mathrm{~min},+\mathrm{CA}
Microwave method, 700 W , 1-4min,+CA| Microwave method, 700 W , | | :--- | | $1-4 \mathrm{~min},+\mathrm{CA}$ |
 6 − 17 6 − 17 6-176-17 -7.45 to 4.1 -7.45 到 4.1 313 12.9 − 75 12.9 − 75 12.9-7512.9-75
407 − 433 407 − 433 407-433407-433
( λ ex = 330 nm ) λ ex = 330 nm (lambda_(ex)=330(nm))\left(\lambda_{\mathrm{ex}}=330 \mathrm{~nm}\right)
407-433 (lambda_(ex)=330(nm))| $407-433$ | | :--- | | $\left(\lambda_{\mathrm{ex}}=330 \mathrm{~nm}\right)$ |
407-433,(lambda_(ex)=330(nm))| $407-433$ <br> $\left(\lambda_{\mathrm{ex}}=330 \mathrm{~nm}\right)$ | | :--- |
 63
345 2.5 − 89.5 2.5 − 89.5 2.5-89.52.5-89.5
Gly, Trp 甘氨酸, 色氨酸

水熱法， 200 ∘ C 200 ∘ C 200^(@)C200{ }^{\circ} \mathrm{C} ， 8 − 12 h , + 8 − 12 h , + 8-12h,+8-12 \mathrm{~h},+ 葡萄糖
Hydrothermal method, 200 ∘ C 200 ∘ C 200^(@)C200{ }^{\circ} \mathrm{C},
8 − 12 h , + 8 − 12 h , + 8-12h,+8-12 \mathrm{~h},+ glucose
Hydrothermal method, 200^(@)C, 8-12h,+ glucose| Hydrothermal method, $200{ }^{\circ} \mathrm{C}$, | | :--- | | $8-12 \mathrm{~h},+$ glucose |
 2 − 5.4 2 − 5.4 2-5.42-5.4 -19 to 21 -19 到 21 n.d. 22.7 − 24.2 22.7 − 24.2 22.7-24.222.7-24.2
( λ ex = 220 − 400 nm ) 447 λ ex = 220 − 400 nm 447 (lambda_(ex)=220-400(nm))^(447)\stackrel{447}{\left(\lambda_{\mathrm{ex}}=220-400 \mathrm{~nm}\right)}
(lambda_(ex)=220-400(nm))^(447)| $\stackrel{447}{\left(\lambda_{\mathrm{ex}}=220-400 \mathrm{~nm}\right)}$ | | :--- |
 64

Phe, Tyr, Trp, His, Leu, Glu, Arg, Cys, Gly
Phe, Tyr, Trp, His, Leu, Glu,
Arg, Cys, Gly
Phe, Tyr, Trp, His, Leu, Glu, Arg, Cys, Gly| Phe, Tyr, Trp, His, Leu, Glu, | | :--- | | Arg, Cys, Gly |

水熱法， 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C}, 12 h , + CA 12 h , + CA 12h,+CA12 \mathrm{~h},+\mathrm{CA}
Hydrothermal method, 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C},
12 h , + CA 12 h , + CA 12h,+CA12 \mathrm{~h},+\mathrm{CA}
Hydrothermal method, 180^(@)C, 12h,+CA| Hydrothermal method, $180^{\circ} \mathrm{C}$, | | :--- | | $12 \mathrm{~h},+\mathrm{CA}$ |
Hydrothermal method, 180^(@)C,,12h,+CA| Hydrothermal method, $180^{\circ} \mathrm{C}$, <br> $12 \mathrm{~h},+\mathrm{CA}$ | | :--- |
 1.5 − 7.5 1.5 − 7.5 1.5-7.51.5-7.5 -54.8 to 1.5 -54.8 到 1.5 350 − 380 350 − 380 350-380350-380 25.5 − 62.1 25.5 − 62.1 25.5-62.125.5-62.1
440 − 463 440 − 463 440-463440-463
( λ ex = 350 − 380 nm ) λ ex  = 350 − 380 nm (lambda_("ex ")=350-380(nm))\left(\lambda_{\text {ex }}=350-380 \mathrm{~nm}\right)
440-463 (lambda_("ex ")=350-380(nm))| $440-463$ | | :--- | | $\left(\lambda_{\text {ex }}=350-380 \mathrm{~nm}\right)$ |
440-463,(lambda_("ex ")=350-380(nm))| $440-463$ <br> $\left(\lambda_{\text {ex }}=350-380 \mathrm{~nm}\right)$ | | :--- |
 65
Arg 阿根廷

微波法，1000 瓦， 2 min , + CA 2 min , + CA 2min,+CA2 \mathrm{~min},+\mathrm{CA}
Microwave method, 1000 W ,
2 min , + CA 2 min , + CA 2min,+CA2 \mathrm{~min},+\mathrm{CA}
Microwave method, 1000 W , 2min,+CA| Microwave method, 1000 W , | | :--- | | $2 \mathrm{~min},+\mathrm{CA}$ |
 1 − 10 1 − 10 1-101-10 -10 n.d. n.d.
( λ ex 425 = 310 − 350 nm ) λ ex 425 = 310 − 350 nm {:((lambda_(ex):}^(425))=310-350(nm))\left.\stackrel{425}{\left(\lambda_{\mathrm{ex}}\right.}=310-350 \mathrm{~nm}\right)
{:((lambda_(ex):}^(425))=310-350(nm))| $\left.\stackrel{425}{\left(\lambda_{\mathrm{ex}}\right.}=310-350 \mathrm{~nm}\right)$ | | :--- |
 66
Gly, Lys, Ser 甘氨酸、賴氨酸、絲氨酸

水熱法， 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C}, 6 h , + CA 6 h , + CA 6h,+CA6 \mathrm{~h},+\mathrm{CA}
Hydrothermal method, 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C},
6 h , + CA 6 h , + CA 6h,+CA6 \mathrm{~h},+\mathrm{CA}
Hydrothermal method, 180^(@)C, 6h,+CA| Hydrothermal method, $180^{\circ} \mathrm{C}$, | | :--- | | $6 \mathrm{~h},+\mathrm{CA}$ |
 2.3 − 14.5 2.3 − 14.5 2.3-14.52.3-14.5 n.d. 360 10.6 − 12.3 10.6 − 12.3 10.6-12.310.6-12.3
410 − 450 410 − 450 410-450410-450
( λ ex = 340 − 380 nm ) λ ex = 340 − 380 nm (lambda_(ex)=340-380(nm))\left(\lambda_{\mathrm{ex}}=340-380 \mathrm{~nm}\right)
410-450 (lambda_(ex)=340-380(nm))| $410-450$ | | :--- | | $\left(\lambda_{\mathrm{ex}}=340-380 \mathrm{~nm}\right)$ |
410-450,(lambda_(ex)=340-380(nm))| $410-450$ <br> $\left(\lambda_{\mathrm{ex}}=340-380 \mathrm{~nm}\right)$ | | :--- |
 67
His 他的

微波法，700 瓦， 2.7 min , + H 3 PO 4 2.7 min , + H 3 PO 4 2.7min,+H_(3)PO_(4)2.7 \mathrm{~min},+\mathrm{H}_{3} \mathrm{PO}_{4}
Microwave method, 700 W ,
2.7 min , + H 3 PO 4 2.7 min , + H 3 PO 4 2.7min,+H_(3)PO_(4)2.7 \mathrm{~min},+\mathrm{H}_{3} \mathrm{PO}_{4}
Microwave method, 700 W , 2.7min,+H_(3)PO_(4)| Microwave method, 700 W , | | :--- | | $2.7 \mathrm{~min},+\mathrm{H}_{3} \mathrm{PO}_{4}$ |
 1 − 4 1 − 4 1-41-4 n.d. 360 44.9 440 ( λ ex = 360 nm ) 440 λ ex  = 360 nm 440(lambda_("ex ")=360(nm))440\left(\lambda_{\text {ex }}=360 \mathrm{~nm}\right) 68
Asn Pyrolysis method 熱解法 2.9 n.d. n.d. n.d. 441 ( λ ex = 348 nm ) 441 λ ex  = 348 nm 441(lambda_("ex ")=348(nm))441\left(\lambda_{\text {ex }}=348 \mathrm{~nm}\right) 69
Cys

微波法，4 分鐘，+ CA
Microwave method, 4 min, +
CA
Microwave method, 4 min, + CA| Microwave method, 4 min, + | | :--- | | CA |
 2 − 4 2 − 4 2-42-4 n.d. 355 81 − 85 81 − 85 81-8581-85
435 − 460 435 − 460 435-460435-460
( λ ex = 300 − 400 nm ) λ ex = 300 − 400 nm (lambda_(ex)=300-400(nm))\left(\lambda_{\mathrm{ex}}=300-400 \mathrm{~nm}\right)
435-460 (lambda_(ex)=300-400(nm))| $435-460$ | | :--- | | $\left(\lambda_{\mathrm{ex}}=300-400 \mathrm{~nm}\right)$ |
435-460,(lambda_(ex)=300-400(nm))| $435-460$ <br> $\left(\lambda_{\mathrm{ex}}=300-400 \mathrm{~nm}\right)$ | | :--- |
 70
Gly 甘露糖

水熱法， 300 ∘ C 300 ∘ C 300^(@)C300^{\circ} \mathrm{C}，2 小時
Hydrothermal method, 300 ∘ C 300 ∘ C 300^(@)C300^{\circ} \mathrm{C},
2 h
Hydrothermal method, 300^(@)C, 2 h| Hydrothermal method, $300^{\circ} \mathrm{C}$, | | :--- | | 2 h |
 2.1 − 3.1 2.1 − 3.1 2.1-3.12.1-3.1 n.d. 365 30.6
410 − 580 410 − 580 410-580410-580
( λ ex = 365 − 465 nm ) λ ex = 365 − 465 nm (lambda_(ex)=365-465(nm))\left(\lambda_{\mathrm{ex}}=365-465 \mathrm{~nm}\right)
410-580 (lambda_(ex)=365-465(nm))| $410-580$ | | :--- | | $\left(\lambda_{\mathrm{ex}}=365-465 \mathrm{~nm}\right)$ |
410-580,(lambda_(ex)=365-465(nm))| $410-580$ <br> $\left(\lambda_{\mathrm{ex}}=365-465 \mathrm{~nm}\right)$ | | :--- |
 37

半胱氨酸, lysine, 組氨酸, serine, 甘氨酸, 脯氨酸, 苯丙氨酸, 天冬氨酸, 白氨酸
Cys, Lys, His, Ser, Gly, Pro,
Phe, Asp, Leu
Cys, Lys, His, Ser, Gly, Pro, Phe, Asp, Leu| Cys, Lys, His, Ser, Gly, Pro, | | :--- | | Phe, Asp, Leu |

水熱法， 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C}, 24 h , + CA 24 h , + CA 24h,+CA24 \mathrm{~h},+\mathrm{CA}
Hydrothermal method, 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C},
24 h , + CA 24 h , + CA 24h,+CA24 \mathrm{~h},+\mathrm{CA}
Hydrothermal method, 180^(@)C, 24h,+CA| Hydrothermal method, $180^{\circ} \mathrm{C}$, | | :--- | | $24 \mathrm{~h},+\mathrm{CA}$ |
 0.2 − 100 0.2 − 100 0.2-1000.2-100 -18.5 to 7 -18.5 到 7 350 14 − 90 14 − 90 14-9014-90
409 − 439 409 − 439 409-439409-439
( λ ex = 350 nm ) λ ex = 350 nm (lambda_(ex)=350(nm))\left(\lambda_{\mathrm{ex}}=350 \mathrm{~nm}\right)
409-439 (lambda_(ex)=350(nm))| $409-439$ | | :--- | | $\left(\lambda_{\mathrm{ex}}=350 \mathrm{~nm}\right)$ |
409-439,(lambda_(ex)=350(nm))| $409-439$ <br> $\left(\lambda_{\mathrm{ex}}=350 \mathrm{~nm}\right)$ | | :--- |
 這項工作
this
work
this work| this | | :--- | | work |
AAs conditions "particle size, nm" "zeta potential, mV" "excitation wavelength, nm" QY, % "emission wavelength, nm" ref Arg, Lys, His, Cys, Met "Microwave method, 700 W , 1-4min,+CA" 6-17 -7.45 to 4.1 313 12.9-75 "407-433,(lambda_(ex)=330(nm))" 63 345 2.5-89.5 Gly, Trp "Hydrothermal method, 200^(@)C, 8-12h,+ glucose" 2-5.4 -19 to 21 n.d. 22.7-24.2 "(lambda_(ex)=220-400(nm))^(447)" 64 "Phe, Tyr, Trp, His, Leu, Glu, Arg, Cys, Gly" "Hydrothermal method, 180^(@)C,,12h,+CA" 1.5-7.5 -54.8 to 1.5 350-380 25.5-62.1 "440-463,(lambda_("ex ")=350-380(nm))" 65 Arg "Microwave method, 1000 W , 2min,+CA" 1-10 -10 n.d. n.d. "{:((lambda_(ex):}^(425))=310-350(nm))" 66 Gly, Lys, Ser "Hydrothermal method, 180^(@)C, 6h,+CA" 2.3-14.5 n.d. 360 10.6-12.3 "410-450,(lambda_(ex)=340-380(nm))" 67 His "Microwave method, 700 W , 2.7min,+H_(3)PO_(4)" 1-4 n.d. 360 44.9 440(lambda_("ex ")=360(nm)) 68 Asn Pyrolysis method 2.9 n.d. n.d. n.d. 441(lambda_("ex ")=348(nm)) 69 Cys "Microwave method, 4 min, + CA" 2-4 n.d. 355 81-85 "435-460,(lambda_(ex)=300-400(nm))" 70 Gly "Hydrothermal method, 300^(@)C, 2 h" 2.1-3.1 n.d. 365 30.6 "410-580,(lambda_(ex)=365-465(nm))" 37 "Cys, Lys, His, Ser, Gly, Pro, Phe, Asp, Leu" "Hydrothermal method, 180^(@)C, 24h,+CA" 0.2-100 -18.5 to 7 350 14-90 "409-439,(lambda_(ex)=350(nm))" "this work"| AAs | conditions | particle <br> size, nm | zeta potential, <br> mV | excitation <br> wavelength, nm | QY, % | emission wavelength, <br> nm | ref | | :---: | :---: | :---: | :---: | :---: | :---: | :---: | :---: | | Arg, Lys, His, Cys, Met | Microwave method, 700 W , <br> $1-4 \mathrm{~min},+\mathrm{CA}$ | $6-17$ | -7.45 to 4.1 | 313 | $12.9-75$ | $407-433$ <br> $\left(\lambda_{\mathrm{ex}}=330 \mathrm{~nm}\right)$ | 63 | | | | | | 345 | $2.5-89.5$ | | | | Gly, Trp | Hydrothermal method, $200{ }^{\circ} \mathrm{C}$, <br> $8-12 \mathrm{~h},+$ glucose | $2-5.4$ | -19 to 21 | n.d. | $22.7-24.2$ | $\stackrel{447}{\left(\lambda_{\mathrm{ex}}=220-400 \mathrm{~nm}\right)}$ | 64 | | Phe, Tyr, Trp, His, Leu, Glu, <br> Arg, Cys, Gly | Hydrothermal method, $180^{\circ} \mathrm{C}$, <br> $12 \mathrm{~h},+\mathrm{CA}$ | $1.5-7.5$ | -54.8 to 1.5 | $350-380$ | $25.5-62.1$ | $440-463$ <br> $\left(\lambda_{\text {ex }}=350-380 \mathrm{~nm}\right)$ | 65 | | Arg | Microwave method, 1000 W , <br> $2 \mathrm{~min},+\mathrm{CA}$ | $1-10$ | -10 | n.d. | n.d. | $\left.\stackrel{425}{\left(\lambda_{\mathrm{ex}}\right.}=310-350 \mathrm{~nm}\right)$ | 66 | | Gly, Lys, Ser | Hydrothermal method, $180^{\circ} \mathrm{C}$, <br> $6 \mathrm{~h},+\mathrm{CA}$ | $2.3-14.5$ | n.d. | 360 | $10.6-12.3$ | $410-450$ <br> $\left(\lambda_{\mathrm{ex}}=340-380 \mathrm{~nm}\right)$ | 67 | | His | Microwave method, 700 W , <br> $2.7 \mathrm{~min},+\mathrm{H}_{3} \mathrm{PO}_{4}$ | $1-4$ | n.d. | 360 | 44.9 | $440\left(\lambda_{\text {ex }}=360 \mathrm{~nm}\right)$ | 68 | | Asn | Pyrolysis method | 2.9 | n.d. | n.d. | n.d. | $441\left(\lambda_{\text {ex }}=348 \mathrm{~nm}\right)$ | 69 | | Cys | Microwave method, 4 min, + <br> CA | $2-4$ | n.d. | 355 | $81-85$ | $435-460$ <br> $\left(\lambda_{\mathrm{ex}}=300-400 \mathrm{~nm}\right)$ | 70 | | Gly | Hydrothermal method, $300^{\circ} \mathrm{C}$, <br> 2 h | $2.1-3.1$ | n.d. | 365 | 30.6 | $410-580$ <br> $\left(\lambda_{\mathrm{ex}}=365-465 \mathrm{~nm}\right)$ | 37 | | Cys, Lys, His, Ser, Gly, Pro, <br> Phe, Asp, Leu | Hydrothermal method, $180^{\circ} \mathrm{C}$, <br> $24 \mathrm{~h},+\mathrm{CA}$ | $0.2-100$ | -18.5 to 7 | 350 | $14-90$ | $409-439$ <br> $\left(\lambda_{\mathrm{ex}}=350 \mathrm{~nm}\right)$ | this <br> work |
a a ^(a){ }^{a} Arg—arginine, Lys—lysine, His—histidine, Cys—cysteine, Met—methionine, CA—citric acid, Gly—glycine, Trp—tryptophan, Asp—aspartic acid, Glu-glutamic acid, Tyr-tyrosine, Gln-glutamine, Phe-phenylalanine, Leu-leucine, Ser-serine, Asn-asparagine, and Pro-proline; n.d. - no data.
a a ^(a){ }^{a} Arg—精氨酸, Lys—賴氨酸, His—組氨酸, Cys—半胱氨酸, Met—蛋氨酸, CA—檸檬酸, Gly—甘氨酸, Trp—色氨酸, Asp—天冬氨酸, Glu—谷氨酸, Tyr—酪氨酸, Gln—谷氨酰胺, Phe—苯丙氨酸, Leu—亮氨酸, Ser—絲氨酸, Asn—天冬酰胺, Pro—脯氨酸; n.d. - 無數據。
Figure 6. DLS data of the CQD volume-size distribution in the aqueous suspension under neutral pH ; solid lines represent unimodal distribution curves.
圖 6. 在中性 pH 下水性懸浮液中 CQD 體積-大小分佈的 DLS 數據；實線表示單峰分佈曲線。
the polymerization-carbonization process during hydrothermal synthesis. The growth of CQDs could be described by a competing generation of oligomers and carbonization. Hence, the composition of CQD depends on the reaction temperature and time because those parameters affect the number of polymeric structures, the appearance of microcrystalline regions or lattices, and the consumption of the polymer for core building. Zeng et al. showed that for the same substrates, one could obtain polymer chains/carbon structures or highly carbonized CQDs and spherical particles with an amorphous core or graphitic carbogenic particles. 71 71 ^(71){ }^{71} In summary, the differences in temperature and time influence the carbonization degree and, as a consequence, the optical CQD properties.
在水熱合成過程中的聚合-碳化過程。CQDs 的生長可以用寡聚物和碳化的競爭生成來描述。因此，CQD 的組成取決於反應的溫度和時間，因為這些參數影響聚合物結構的數量、微晶區域或晶格的出現，以及聚合物在核心建設中的消耗。曾等人顯示，對於相同的基材，可以獲得聚合物鏈/碳結構或高度碳化的 CQDs 和具有非晶核心或石墨碳顆粒的球形粒子。總之，溫度和時間的差異影響碳化程度，從而影響光學 CQD 的特性。
Last but not least, for water-based applicabilities, DLS analysis was performed to determine the average size of CQDs and the stability of CQD aqueous dispersions (Figure 6). The diameters were found in the range of 0.2 to 100 nm . The dispersion containing the smallest CQD s, also with the lowest size distribution, was prepared from Cys-CQDs. Ser-, His-, and Asp-CQD dispersions also contained a small amount of larger particles. The lowest content of particles smaller than 10 nm was observed for Gly (only 21 vol %).
最後但同樣重要的是，針對水性應用，進行了 DLS 分析以確定 CQDs 的平均大小和 CQD 水性分散液的穩定性（圖 6）。直徑範圍為 0.2 至 100 納米。含有最小 CQDs 的分散液，且尺寸分佈最小，是由 Cys-CQDs 製備的。Ser-、His-和 Asp-CQD 分散液也含有少量較大顆粒。Gly 的 10 納米以下顆粒含量最低（僅 21 體積百分比）。
In colloids, the zeta potential is the difference between the potential of the outer mobile and the inner stationary layer attached to the particle dispersed in the continuous phase and can be considered as an indicator of dispersion stability. Samples with a high absolute value of zeta potential are electrically stabilized by repulsion, while those with low zeta potential tend to coagulate or flocculate. In the case of CQDs, multiple surface functional groups can improve the dispersion of CQDs in aqueous or, generally, polar solvents. And so, practically all CQDs had a negative zeta potential at neutral pH (Figure S5). This fact indicates that the CQD surfaces were rich in ionizable, negatively charged moieties like carboxylic (or thiol, etc.) groups, which fully corresponds to the previous analyses. The highest absolute values of the zeta potential in the broadest pH scale were found for Lys- and Cys-CQDs, providing excellent dispersibility and stability in water. At pH = pH = pH=\mathrm{pH}= 7, for His-, Leu-, Asp-, and Phe-CQDs, zeta potential values were almost neutral, while for Pro-CQDs, the zeta potential was positive. At pH = 2 pH = 2 pH=2\mathrm{pH}=2, most of the amine groups were
在膠體中，ζ電位是分散在連續相中的粒子所附著的外部可移動層和內部靜止層之間的電位差，可以被視為分散穩定性的指標。具有高絕對值的ζ電位的樣品通過排斥作用進行電氣穩定，而低ζ電位的樣品則傾向於凝聚或絮凝。在量子點的情況下，多種表面官能團可以改善量子點在水性或一般極性溶劑中的分散性。因此，幾乎所有的量子點在中性 pH 下都具有負的ζ電位（圖 S5）。這一事實表明，量子點的表面富含可離子化的負電荷基團，如羧基（或硫醇等）基團，這與之前的分析完全一致。在最廣泛的 pH 範圍內，Lys-和 Cys-量子點的ζ電位絕對值最高，提供了優異的水中分散性和穩定性。在 pH 7 時，His-、Leu-、Asp-和 Phe-量子點的ζ電位值幾乎為中性，而 Pro-量子點的ζ電位則為正值。在 pH 1 時，大多數胺基團都已經...
protonated, giving the overall higher positive surface charge. At alkaline suspension, the zeta potential remains highly negative to reflect the presence of stable anions for all CQDs.
質子化，導致整體表面電荷較高的正值。在鹼性懸浮液中，zeta 電位保持高度負值，以反映所有 CQDs 中穩定陰離子的存在。

- CONCLUSIONS - 結論

CQDs obtained from sustainable sources such as AAs and via a green hydrothermal method represent an excellent class of application-tunable carbon nanomaterials. Here, the structural characterization and spectral properties of CQDs have been studied. The blue (and green) fluorescent CQDs were obtained without a purification step, while Cys-, Phe-, Leu-, and Lys-CQDs showed high QYs, conquering the conventional dyes. It was found that the structure of AAs had a great impact on the optical properties of CQDs, such as emission wavelength, excitation wavelength-dependent fluorescence, and QY. Moreover, the water stability of Lys-CQDs (and to a lesser extent, Cys-CQDs) was not compromised by extreme pH environments.
從可持續來源如氨基酸（AAs）獲得的量子點（CQDs）以及通過綠色水熱法製備的量子點，代表了一類優秀的可調應用碳納米材料。在此，對 CQDs 的結構特徵和光譜性質進行了研究。藍色（和綠色）螢光 CQDs 在未經純化的情況下獲得，而半胱氨酸（Cys）、苯丙氨酸（Phe）、亮氨酸（Leu）和賴氨酸（Lys）CQDs 顯示出高量子產率（QYs），超越了傳統染料。研究發現，氨基酸的結構對 CQDs 的光學性質有很大影響，例如發射波長、激發波長依賴的螢光和量子產率。此外，賴氨酸 CQDs（以及在較小程度上，半胱氨酸 CQDs）的水穩定性在極端 pH 環境下並未受到損害。
Despite the promising results listed above, it must be emphasized that future research must address, if synthesized in a versatile and economic approach from sustainable sources, the separation of CQDs by size. The separation step and covalent functionalization with a well-defined linker via, for example, carboxylic groups, should lead not only to a narrower size distribution of water-soluble and water-stable CQDs but also, first of all, allow for full-color fluorescence without changing the excitation wavelength as the most pressing requirement toward programmable fluorescent probes and catalysts-only to mention the most ready-to-scaleup applications.
儘管上述結果令人鼓舞，但必須強調的是，未來的研究必須解決從可持續來源以多功能和經濟的方法合成的 CQDs 按大小分離的問題。這一步驟的分離和通過例如羧基的明確連接劑進行的共價功能化，不僅應該導致水溶性和水穩定 CQDs 的尺寸分佈更窄，而且首先應該實現全色螢光，而不改變激發波長，這是朝向可編程螢光探針和催化劑的最迫切需求——僅提及最容易擴展的應用。

- ASSOCIATED CONTENT - 相關內容

(s) Supporting Information
（s）支持信息

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.2c04751.
支持信息可免費獲得，請訪問 https://pubs.acs.org/doi/10.1021/acsomega.2c04751。
Representative TEM and SAED images of CQDs, fluorescence spectra of CQDs as a function of the exciting wavelength from 200 to 480 nm , and zeta potential of CQD dispersions at various pH values for zeta potential distribution(PDF)
代表性的碳量子點（CQDs）透射電子顯微鏡（TEM）和選擇性電子衍射（SAED）影像，CQDs 在 200 至 480 納米激發波長下的螢光光譜，以及不同 pH 值下 CQD 分散液的ζ電位分佈（PDF）

AUTHOR INFORMATION 作者資訊

Corresponding Authors 通訊作者

Anna Kolanowska - Faculty of Chemistry, Department of Organic Chemistry, Bioorganic Chemistry and Biotechnology, Silesian University of Technology, 44-100 Gliwice, Poland; Faculty of Chemistry, Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, 44-100 Gliwice, Poland; Biotechnology Centre, Silesian University of Technology, 44-100 Gliwice, Poland; - orcid.org/0000-0002-2073-4808; Email: anna.kolanowska@polsl.pl
安娜·科拉諾夫斯卡 - 西里西亞科技大學化學系，有機化學、生物有機化學與生物技術系，波蘭格利維采 44-100；西里西亞科技大學化學系，物理化學與聚合物技術系，波蘭格利維采 44-100；西里西亞科技大學生物技術中心，波蘭格利維采 44-100； - orcid.org/0000-0002-2073-4808; 電子郵件：anna.kolanowska@polsl.pl
Slawomir Boncel - Faculty of Chemistry, Department of Organic Chemistry, Bioorganic Chemistry and Biotechnology, Silesian University of Technology, 44-100 Gliwice, Poland; Centre for Organic and Nanohybrid Electronics, Silesian University of Technology, 44-100 Gliwice, Poland; © orcid.org/0000-0002-0787-5243; Email: slawomir.boncel@polsl.pl
斯瓦沃米爾·邦策爾 - 斯利基安科技大學化學系有機化學、生物有機化學與生物技術系，波蘭格利維采 44-100；斯利基安科技大學有機與納米混合電子中心，波蘭格利維采 44-100；© orcid.org/0000-0002-0787-5243; 電子郵件：slawomir.boncel@polsl.pl

Authors 作者

Grzegorz Dzido - Faculty of Chemistry, Department of Chemical Engineering and Process Design, Silesian University of Technology, 44-100 Gliwice, Poland
格熱戈日·季多 - 化學系，化學工程與工藝設計系，西里西亞科技大學，44-100 格利維采，波蘭
Maciej Krzywiecki - Institute of Physics-CSE, Silesian University of Technology, 44-100 Gliwice, Poland; (1) orcid.org/0000-0002-6151-8810
Maciej Krzywiecki - 物理學研究所-CSE，西里西亞科技大學，44-100 格利維采，波蘭； (1) orcid.org/0000-0002-6151-8810
Mateusz M. Tomczyk - Faculty of Chemistry, Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, 44-100 Gliwice, Poland; (1) orcid.org/0000-0002-9594-4535
Mateusz M. Tomczyk - 化學系，物理化學與聚合物技術系，西里西亞科技大學，44-100 格利維采，波蘭； (1) orcid.org/0000-0002-9594-4535
Dariusz Lukowiec - Materials Research Laboratory, Faculty of Mechanical Engineering, Silesian University of Technology, 44-100 Gliwice, Poland; ©orcid.org/0000-0002-20789980
達里烏什·盧科維茨 - 材料研究實驗室，機械工程系，西里西亞科技大學，44-100 格利維采，波蘭； ©orcid.org/0000-0002-20789980
Szymon Ruczka - Faculty of Chemistry, Department of Organic Chemistry, Bioorganic Chemistry and Biotechnology, Silesian University of Technology, 44-100 Gliwice, Poland; Centre for Organic and Nanohybrid Electronics, Silesian University of Technology, 44-100 Gliwice, Poland
Szymon Ruczka - 化學系，有機化學、生物有機化學與生物技術系，西里西亞科技大學，44-100 格利維采，波蘭；有機與納米混合電子中心，西里西亞科技大學，44-100 格利維采，波蘭
Complete contact information is available at:
完整的聯絡資訊可在以下查詢：
https://pubs.acs.org/10.1021/acsomega.2c04751

Notes 筆記

The authors declare no competing financial interest.
作者聲明沒有競爭性的財務利益。

ACKNOWLEDGMENTS 致謝

This work was supported by the National Science Centre grant PRELUDIUM-18 (UMO-2019/35/N/ST5/02563). S.B. is also very grateful for the financial support from the National Science Centre (Poland) grant no. 2019/33/B/ST5/01412 in the framework of the OPUS program.
本研究得到了國家科學中心 PRELUDIUM-18（UMO-2019/35/N/ST5/02563）資助。S.B. 也非常感謝國家科學中心（波蘭）在 OPUS 計劃框架下的資助，資助號碼為 2019/33/B/ST5/01412。

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  1. Received: July 27, 2022 收到：2022 年 7 月 27 日
    Accepted: October 21, 2022
    接受日期：2022 年 10 月 21 日
    Published: November 1, 2022
    發佈日期：2022 年 11 月 1 日