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CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-GO nanocomposites for boosting photocatalytic degradation performance
用于提高光催化降解性能的 CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} -GO 纳米复合材料

Hongmei Ju, Tingsen Fang, Yun Zhou, Xianbin Feng, Tinghui Song, Feng Lu, Wenchao Liu
鞠红梅、方廷森、周云、冯显斌、宋廷辉、卢锋、刘文超Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), Nanjing, China
南京理工大学柔性电子学重点实验室（KLOFE）和先进材料研究院（IAM），江苏先进材料国家协同创新中心（SICAM），南京，中国

ARTICLE INFO  文章信息

Keywords:  关键词：

Perovskite
Nanocomposites  纳米复合材料
CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3}
Photocatalytic  光催化
Degradation  退化

Abstract  摘要

In order to address the main challenge of weak photocatalytic performance of pure metal halide perovskite materials, we innovatively introduced MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}-graphene oxide (GO) composite structure and synthesized CsPbBr 3 − CsPbBr 3 − CsPbBr_(3)^(-)\mathrm{CsPbBr}_{3}{ }^{-} MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}-GO nanocomposites by a two-step method. XRD and Raman results show that the three components are well combined to form a new CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-GO nanocomposite. TEM results show that MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} nanoribbons and CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} quantum dots (QDs) are uniformly dispersed on the GO sheet. The photocatalytic activity of nanocomposites was evaluated by studying the photodegradation of Sudan Red III under xenon lamp irradiation. Benefiting from abundant active interfaces, the nanocomposites show much excellent photocatalytic degradation performance compared with pure CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs. The degradation rate of Sudan Red III by CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites is 3.1 times of that of pure perovskite QDs. Sudan Red III was completely photocatalytic degraded in 100 min . We believe that GO, with suitable band structure, high conductivity and good dispersibility, can bridge well MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} and CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3}, act as a good electron transport channel, reduce carrier recombination and ultimately boost photocatalytic performance.
针对纯金属卤化物包晶材料光催化性能弱的主要难题，我们创新性地引入了 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} -氧化石墨烯（GO）复合结构，并通过两步法合成了 CsPbBr 3 − CsPbBr 3 − CsPbBr_(3)^(-)\mathrm{CsPbBr}_{3}{ }^{-} MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} -GO纳米复合材料。XRD 和拉曼结果表明，三种组分很好地结合在一起，形成了一种新的 CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} -GO 纳米复合材料。TEM结果表明， MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 纳米带和 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} 量子点（QDs）均匀地分散在GO片上。通过研究氙灯照射下苏丹红 III 的光降解，评估了纳米复合材料的光催化活性。与纯 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs 相比，纳米复合材料得益于丰富的活性界面，表现出更为优异的光催化降解性能。 CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} 纳米复合材料对苏丹红 III 的降解率是纯包晶体 QDs 的 3.1 倍。苏丹红 III 在 100 分钟内被完全光催化降解。我们认为，GO 具有合适的能带结构、高导电性和良好的分散性，可以很好地桥接 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 和 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} ，成为良好的电子传输通道，减少载流子重组，最终提高光催化性能。

1. Introduction  1.导言

With the rapid development of industry, the pollution caused by organic substances is becoming increasingly serious. Nonionic organic dyes, such as Sudan Red, are widely used in textile, leather, coating and plastic industries, causing serious environmental hazards. Some criminals add them into food. Their metabolites are classified as grade II or III carcinogens. What’s more, Sudan Red dyes are a kind of azo compounds, compared to some widely used photocatalytic degradation dyes such as methyl orange, their chemical structure is extremely stable and difficult to remove. Therefore, most countries prohibit the use of Sudan Red dyes. It is urgent to seek an effective method to solve these problems. Photocatalytic degradation technology is an efficient and clean technology to convert organic pollutants to CO 2 CO 2 CO_(2)\mathrm{CO}_{2}, water, and other small molecules under the help of renewable solar energy [1-4]. The traditional photocatalysts, for example, TiO 2 TiO 2 TiO_(2)\mathrm{TiO}_{2} has a wide band-gap ( 3.2 eV ) and can only absorb the ultraviolet light which has only about 5 % 5 % 5%5 \% of the whole sunlight energy. All-inorganic halide perovskite nanocrystal quantum dots ( CsPbX 3 QDs , X = Cl , Br CsPbX 3 QDs , X = Cl , Br (CsPbX_(3)QDs,X=Cl,Br:}\left(\mathrm{CsPbX}_{3} \mathrm{QDs}, \mathrm{X}=\mathrm{Cl}, \mathrm{Br}\right., and I ) ) )) have attracted much attention due to their excellent opto-electric properties such as high absorption
随着工业的快速发展，有机物造成的污染日益严重。苏丹红等非离子有机染料广泛应用于纺织、皮革、涂料、塑料等行业，对环境造成严重危害。一些不法分子将其添加到食品中。它们的代谢产物被列为二级或三级致癌物。更重要的是，苏丹红染料是一种偶氮化合物，与甲基橙等一些广泛使用的光催化降解染料相比，其化学结构极其稳定，难以去除。因此，大多数国家禁止使用苏丹红染料。寻找一种有效的方法来解决这些问题迫在眉睫。光催化降解技术是一种在可再生太阳能的帮助下，将有机污染物转化为 CO 2 CO 2 CO_(2)\mathrm{CO}_{2} 、水和其他小分子物质的高效清洁技术[1-4]。传统的光催化剂，如 TiO 2 TiO 2 TiO_(2)\mathrm{TiO}_{2} 具有宽带隙（3.2 eV），只能吸收紫外线，而紫外线的能量只占整个太阳光能量的 5 % 5 % 5%5 \% 左右。全无机卤化物过氧化物纳米晶体量子点 ( CsPbX 3 QDs , X = Cl , Br CsPbX 3 QDs , X = Cl , Br (CsPbX_(3)QDs,X=Cl,Br:}\left(\mathrm{CsPbX}_{3} \mathrm{QDs}, \mathrm{X}=\mathrm{Cl}, \mathrm{Br}\right. 和 I ) ) )) 由于具有高吸收等优异的光电特性而备受关注。
coefficient in the visible light range, controllable band-gaps, multi-excitons and high quantum yields [5-8]. They have been widely used in solar cells [9-11], light-emitting diode [12-15], lasers and so on [ 16 , 17 ] [ 16 , 17 ] [16,17][16,17]. Recent years, halide perovskite QDs are also considered possible candidate materials for photocatalytic applications. The main photocatalytic application fields of halide perovskites include photocatalytic hydrogen evolution, carbon dioxide reduction, pollutant degradation and photocatalytic polymerization reaction [18-20]. Up to now, the published reports focus on photocatalytic hydrogen evolution and carbon dioxide reduction. The reports of halide perovskites nanocomposites for photocatalytic degradation are very limited. The main challenge of halide perovskite materials in application of photocatalytic degradation is that the degradation efficiency is still low [20].
在可见光范围内的系数、可控带隙、多激子和高量子产率 [5-8]。它们已被广泛应用于太阳能电池 [9-11]、发光二极管 [12-15]、激光等领域 [ 16 , 17 ] [ 16 , 17 ] [16,17][16,17] 。近年来，卤化物过氧化物 QDs 也被认为是光催化应用的可能候选材料。卤化物类包晶石的主要光催化应用领域包括光催化氢气进化、二氧化碳还原、污染物降解和光催化聚合反应 [18-20]。迄今为止，已发表的报告主要集中在光催化氢进化和二氧化碳还原方面。关于卤化物过氧化物纳米复合材料用于光催化降解的报道非常有限。卤化物包晶材料在光催化降解应用中面临的主要挑战是降解效率仍然较低[20]。
In recent years, two-dimensional MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} has been used in the field of photocatalysis. Researchers found that MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} as a co-catalyst attached on semiconductor can improve the efficiency of visible light absorption and charge separation [21], and greatly increase the photocatalytic activity of catalyst materials [22,23]. Graphene oxide (GO) has special physical and chemical properties, such as two-dimensional structure, large specific surface area, good conductivity and high mobility [24-27]. It has
近年来，二维 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 在光催化领域得到了应用。研究人员发现， MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 作为助催化剂附着在半导体上，可以提高可见光吸收和电荷分离的效率[21]，大大提高催化剂材料的光催化活性[22,23]。氧化石墨烯（GO）具有特殊的物理和化学特性，如二维结构、大比表面积、良好的导电性和高迁移率 [24-27]。它具有
Fig. 1. Schematic diagram of (a) MoS 2 − GO MoS 2 − GO MoS_(2)-GO\mathrm{MoS}_{2}-\mathrm{GO} and (b) CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites forming process.
图 1.(a) MoS 2 − GO MoS 2 − GO MoS_(2)-GO\mathrm{MoS}_{2}-\mathrm{GO} 和 (b) CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} 纳米复合材料成型过程示意图。
been proved to be an ideal co-catalyst for enhancing photocatalytic activity. GO can not only prevent the photocatalyst from agglomerating, but also provide a charge transfer channel with high mobility to prevent the recombination of electron hole pairs [28].
已被证明是提高光催化活性的理想助催化剂。GO 不仅能防止光催化剂团聚，还能提供具有高迁移率的电荷转移通道，防止电子空穴对的重组 [28]。
In this paper, we make full use of the respective advantages of two dimensional MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} and GO in catalytic field and combine them with CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs to form CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites. This structure is expected to solve the main challenge of low photocatalytic efficiency of pure halide perovskite QDs. When CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs absorbs solar light, electrons in the valence band are stimulated to the conduction band, and holes are formed in the valence band. Because the redox potential of GO / GO ∙ − GO / GO ∙ − GO//GO^(∙-)\mathrm{GO} / \mathrm{GO}^{\bullet-} is lower than the conduction band of CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3}, photogenerated electrons can easily be transferred to GO [29]. GO as an electron transport channel can transfer electrons. MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} on GO can receive electrons and provide more reaction sites for catalytic reaction. This can further prevent the recombination of electrons and holes and improve the photocatalytic degradation of organic pollutants [30]. Up to our best knowledge, there are no reports about the photocatalytic degradation of CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-GO nanocomposites.
本文充分利用二维 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 和 GO 在催化领域的各自优势，将它们与 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs 结合形成 CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} 纳米复合材料。这种结构有望解决纯卤化物过氧化物 QDs 光催化效率低的主要难题。当 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs 吸收太阳光时，价带中的电子被激发到导带，同时在价带中形成空穴。由于 GO / GO ∙ − GO / GO ∙ − GO//GO^(∙-)\mathrm{GO} / \mathrm{GO}^{\bullet-} 的氧化还原电位低于 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} 的导带，光生电子很容易转移到 GO 上 [29]。作为电子传输通道，GO 可以传输电子。GO 上的 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 可以接收电子，并为催化反应提供更多的反应位点。这可以进一步防止电子和空穴的重组，提高有机污染物的光催化降解能力 [30]。据我们所知，目前还没有关于 CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} -GO 纳米复合材料光催化降解的报道。

2. Experimental section  2.实验部分

Fig. 1 shows the synthesis process of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} - GO and CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites. The details of the synthesis are blow.
图 1 显示了 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} - GO 和 CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} 纳米复合材料的合成过程。合成的详细过程如下。

2.1. Synthesis of CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs
2.1. CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QD 的合成

5 mL octadecene and 0.188 mmol ( 69 mg ) PbBr 2 0.188 mmol ( 69 mg ) PbBr 2 0.188mmol(69mg)PbBr_(2)0.188 \mathrm{mmol}(69 \mathrm{mg}) \mathrm{PbBr}_{2} were added into a three flask under the protection of N 2 N 2 N_(2)\mathrm{N}_{2}. After heating at 120 ∘ C 120 ∘ C 120^(@)C120{ }^{\circ} \mathrm{C} for 1 h , 0.5 mL oleic acid and 0.5 mL oleamine were added. After 30 min , the solution was gradually heated to 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C} and 0.4 mL cesium oleate was rapidly injected. After 5 s , it was cooled by ice-water bath and 20 mL ethyl acetate was added to dissolve completely the synthesized samples. Then the obtained samples were centrifuged for 5 min at 12000 rpm / 12000 rpm / 12000rpm//12000 \mathrm{rpm} / min, washed three times with ethyl acetate, and vacuum dried at 70 ∘ C 70 ∘ C 70^(@)C70^{\circ} \mathrm{C} for 12 h .
在 N 2 N 2 N_(2)\mathrm{N}_{2} 的保护下，将 5 mL 十八烯和 0.188 mmol ( 69 mg ) PbBr 2 0.188 mmol ( 69 mg ) PbBr 2 0.188mmol(69mg)PbBr_(2)0.188 \mathrm{mmol}(69 \mathrm{mg}) \mathrm{PbBr}_{2} 加入三口烧瓶中。在 120 ∘ C 120 ∘ C 120^(@)C120{ }^{\circ} \mathrm{C} 下加热 1 小时后，加入 0.5 mL 油酸和 0.5 mL 油胺。30 分钟后，将溶液逐渐加热至 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C} ，并迅速注入 0.4 mL 油酸铯。5 秒后，冰水浴冷却，加入 20 mL 乙酸乙酯使合成样品完全溶解。然后在 12000 rpm / 12000 rpm / 12000rpm//12000 \mathrm{rpm} / 分钟离心5分钟，用乙酸乙酯洗涤三次，在 70 ∘ C 70 ∘ C 70^(@)C70^{\circ} \mathrm{C} 真空干燥12小时。

2.2. Synthesis of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} nanosheets
2.2. MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 纳米片的合成

0.205 g Na 2 MoO 4 0.205 g Na 2 MoO 4 0.205gNa_(2)MoO_(4)0.205 \mathrm{~g} \mathrm{Na}_{2} \mathrm{MoO}_{4} and 0.38 g thiourea were dissolved in 60 mL deionized water, then were transferred to 100 mL hydrothermal reactor, sealed and reacted at 210 ∘ C 210 ∘ C 210^(@)C210^{\circ} \mathrm{C} for 26 h and cooled to room temperature naturally. The solution was centrifuged at 12000 rpm / min 12000 rpm / min 12000rpm//min12000 \mathrm{rpm} / \mathrm{min} speed for 5 min, washed alternately with deionized water and ethanol for 3 times, and dried in vacuum at 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} for 12 h .
将 0.205 g Na 2 MoO 4 0.205 g Na 2 MoO 4 0.205gNa_(2)MoO_(4)0.205 \mathrm{~g} \mathrm{Na}_{2} \mathrm{MoO}_{4} 和 0.38 g 硫脲溶于 60 mL 去离子水中，然后转移到 100 mL 水热反应器中，密封并在 210 ∘ C 210 ∘ C 210^(@)C210^{\circ} \mathrm{C} 下反应 26 h，然后自然冷却到室温。溶液以 12000 rpm / min 12000 rpm / min 12000rpm//min12000 \mathrm{rpm} / \mathrm{min} 速度离心 5 分钟，用去离子水和乙醇交替洗涤 3 次，在 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} 真空中干燥 12 小时。

2.3. Synthesis of GO
2.3.合成 GO

GO is synthesized by an improved Hummers method [31]. Firstly, 2 g graphite powder and 1 g NaNO 3 1 g NaNO 3 1gNaNO_(3)1 \mathrm{~g} \mathrm{NaNO}_{3} were mixed evenly. 96 mL H 2 SO 4 96 mL H 2 SO 4 96mLH_(2)SO_(4)96 \mathrm{~mL} \mathrm{H}_{2} \mathrm{SO}_{4} was added into the ice bath slowly and stirred continuously. Then 6 g KMnO 4 was added gradually. Then the mixture was heated to 35 ∘ C 35 ∘ C 35^(@)C35{ }^{\circ} \mathrm{C} in water bath for 18 h . During the reaction, the mixture becomes pasty and brown. Then the paste mixture was added slowly into 150 mL H 2 O 150 mL H 2 O 150mLH_(2)O150 \mathrm{~mL} \mathrm{H}_{2} \mathrm{O}. Since the addition of water into high concentration H 2 SO 4 H 2 SO 4 H_(2)SO_(4)\mathrm{H}_{2} \mathrm{SO}_{4} will release a lot of heat, it is necessary to keep the mixture in an ice bath so that the temperature of the mixture can be kept below 50 ∘ C .5 mL 30 % H 2 O 2 50 ∘ C .5 mL 30 % H 2 O 2 50^(@)C.5mL30%H_(2)O_(2)50{ }^{\circ} \mathrm{C} .5 \mathrm{~mL} 30 \% \mathrm{H}_{2} \mathrm{O}_{2} was diluted with 240 mL H 2 O 240 mL H 2 O 240mLH_(2)O240 \mathrm{~mL} \mathrm{H}_{2} \mathrm{O} and then slowly added to the mixture. The color of the solution gradually turned bright yellow and bubbles were constantly emerging. After stirring for 2 h , the mixture was filtered and washed with 250 mL 10 % HCl 250 mL 10 % HCl 250mL10%HCl250 \mathrm{~mL} \mathrm{10} \mathrm{\%} \mathrm{HCl} aqueous solution, deionized water and ethanol to remove other ions. The final sample was vacuum dried at 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C}.
GO 是通过改进的 Hummers 方法合成的[31]。首先，将 2 克石墨粉和 1 g NaNO 3 1 g NaNO 3 1gNaNO_(3)1 \mathrm{~g} \mathrm{NaNO}_{3} 混合均匀。将 96 mL H 2 SO 4 96 mL H 2 SO 4 96mLH_(2)SO_(4)96 \mathrm{~mL} \mathrm{H}_{2} \mathrm{SO}_{4} 缓慢加入冰浴中并不断搅拌。然后逐渐加入 6 g KMnO 4。然后将混合物在水浴中加热至 35 ∘ C 35 ∘ C 35^(@)C35{ }^{\circ} \mathrm{C} 18 小时。在反应过程中，混合物变成糊状和棕色。然后将糊状混合物缓慢加入 150 mL H 2 O 150 mL H 2 O 150mLH_(2)O150 \mathrm{~mL} \mathrm{H}_{2} \mathrm{O} 中。由于向高浓度的 H 2 SO 4 H 2 SO 4 H_(2)SO_(4)\mathrm{H}_{2} \mathrm{SO}_{4} 中加水会释放大量热量，因此必须将混合物置于冰浴中，使混合物的温度保持在 50 ∘ C .5 mL 30 % H 2 O 2 50 ∘ C .5 mL 30 % H 2 O 2 50^(@)C.5mL30%H_(2)O_(2)50{ }^{\circ} \mathrm{C} .5 \mathrm{~mL} 30 \% \mathrm{H}_{2} \mathrm{O}_{2} 以下，用 240 mL H 2 O 240 mL H 2 O 240mLH_(2)O240 \mathrm{~mL} \mathrm{H}_{2} \mathrm{O} 稀释后缓慢加入混合物中。溶液的颜色逐渐变成亮黄色，并不断冒出气泡。搅拌 2 小时后，过滤混合物，用 250 mL 10 % HCl 250 mL 10 % HCl 250mL10%HCl250 \mathrm{~mL} \mathrm{10} \mathrm{\%} \mathrm{HCl} 水溶液、去离子水和乙醇洗涤，除去其他离子。最后的样品在 60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} 真空干燥。

2.4. Preparation of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}-GO nanocomposites
2.4.制备 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} -GO 纳米复合材料

0.135 g GO was well dispersed in 60 mL deionized water by ultrasonic for 30 min . Then 0.205 g Na 2 MoO 4 0.205 g Na 2 MoO 4 0.205gNa_(2)MoO_(4)0.205 \mathrm{~g} \mathrm{Na}_{2} \mathrm{MoO}_{4} and 0.380 g thiourea were added in the solution. After stirred for 30 min , the mix solution was transferred into 100 mL hydrothermal reactor, sealed and reacted at 210 ∘ C 210 ∘ C 210^(@)C210^{\circ} \mathrm{C} for 26 h then cooled naturally to room temperature. The obtained sample was centrifuged at 12000 rpm / min 12000 rpm / min 12000rpm//min12000 \mathrm{rpm} / \mathrm{min} for 5 min , washed alternately with deionized water and ethanol for 3 times, and dried in vacuum at
用超声波将 0.135 克 GO 充分分散在 60 毫升去离子水中 30 分钟。然后在溶液中加入 0.205 g Na 2 MoO 4 0.205 g Na 2 MoO 4 0.205gNa_(2)MoO_(4)0.205 \mathrm{~g} \mathrm{Na}_{2} \mathrm{MoO}_{4} 和 0.380 克硫脲。搅拌 30 分钟后，将混合溶液转移到 100 mL 水热反应器中，密封并在 210 ∘ C 210 ∘ C 210^(@)C210^{\circ} \mathrm{C} 温度下反应 26 小时，然后自然冷却至室温。得到的样品在 12000 rpm / min 12000 rpm / min 12000rpm//min12000 \mathrm{rpm} / \mathrm{min} 下离心 5 分钟，用去离子水和乙醇交替洗涤 3 次，然后在 12000 rpm / min 12000 rpm / min 12000rpm//min12000 \mathrm{rpm} / \mathrm{min} 下真空干燥。
Fig. 2. (a) XRD patterns of CsPbBr 3 , MoS 2 , CsPbBr 3 − GO , CsPbBr 3 − MoS 2 , MoS 2 − CsPbBr 3 , MoS 2 , CsPbBr 3 − GO , CsPbBr 3 − MoS 2 , MoS 2 − CsPbBr_(3),MoS_(2),CsPbBr_(3)-GO,CsPbBr_(3)-MoS_(2),MoS_(2)-\mathrm{CsPbBr}_{3}, \mathrm{MoS}_{2}, \mathrm{CsPbBr}_{3}-\mathrm{GO}, \mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}, \mathrm{MoS}_{2}- GO and CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO}, (b) The Raman spectra of CsPbBr 3 , GO , CsPbBr 3 − GO CsPbBr 3 , GO , CsPbBr 3 − GO CsPbBr_(3),GO,CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}, \mathrm{GO}, \mathrm{CsPbBr}_{3}-\mathrm{GO}, CsPbBr 3 − MoS 2 , MoS 2 − GO CsPbBr 3 − MoS 2 , MoS 2 − GO CsPbBr_(3)-MoS_(2),MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}, \mathrm{MoS}_{2}-\mathrm{GO} and CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites.
图 2：（a） CsPbBr 3 , MoS 2 , CsPbBr 3 − GO , CsPbBr 3 − MoS 2 , MoS 2 − CsPbBr 3 , MoS 2 , CsPbBr 3 − GO , CsPbBr 3 − MoS 2 , MoS 2 − CsPbBr_(3),MoS_(2),CsPbBr_(3)-GO,CsPbBr_(3)-MoS_(2),MoS_(2)-\mathrm{CsPbBr}_{3}, \mathrm{MoS}_{2}, \mathrm{CsPbBr}_{3}-\mathrm{GO}, \mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}, \mathrm{MoS}_{2}- GO 和 CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} 的 XRD 图；（b） CsPbBr 3 , GO , CsPbBr 3 − GO CsPbBr 3 , GO , CsPbBr 3 − GO CsPbBr_(3),GO,CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}, \mathrm{GO}, \mathrm{CsPbBr}_{3}-\mathrm{GO} 、 CsPbBr 3 − MoS 2 , MoS 2 − GO CsPbBr 3 − MoS 2 , MoS 2 − GO CsPbBr_(3)-MoS_(2),MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}, \mathrm{MoS}_{2}-\mathrm{GO} 和 CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} 纳米复合材料的拉曼光谱。

60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} for 12 h.   60 ∘ C 60 ∘ C 60^(@)C60^{\circ} \mathrm{C} 12小时。

2.5. Preparation of CsPbBr 3 − MoS 2 , CsPbBr 3 − GO CsPbBr 3 − MoS 2 , CsPbBr 3 − GO CsPbBr_(3)-MoS_(2),CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}, \mathrm{CsPbBr}_{3}-\mathrm{GO} and CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites
2.5.制备 CsPbBr 3 − MoS 2 , CsPbBr 3 − GO CsPbBr 3 − MoS 2 , CsPbBr 3 − GO CsPbBr_(3)-MoS_(2),CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}, \mathrm{CsPbBr}_{3}-\mathrm{GO} 和 CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} 纳米复合材料

5 mL octadecene was added into a 50 mL flask, then 5 mg MoS 2 5 mg MoS 2 5mgMoS_(2)5 \mathrm{mg} \mathrm{MoS}{ }_{2} (or 5 mg GO or 5 mg MoS 2 5 mg MoS 2 5mgMoS_(2)5 \mathrm{mg} \mathrm{MoS}_{2}-GO) was added to the flask and well dispersed under ultrasonic for 30 min . Then 0.188 mmol ( 69 mg ) PbBr 2 0.188 mmol ( 69 mg ) PbBr 2 0.188mmol(69mg)PbBr_(2)0.188 \mathrm{mmol}(69 \mathrm{mg}) \mathrm{PbBr}_{2} was added to the flask under the protection of N 2 N 2 N_(2)\mathrm{N}_{2}. The solution was heated and kept at 120 ∘ C 120 ∘ C 120^(@)C120{ }^{\circ} \mathrm{C} for 1 h , then 0.5 mL oleic acid and 0.5 mL oleamine were added. After reaction for 30 min , the temperature gradually increased to 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C}, 0.4 mL cesium oleate was rapidly injected into the flask and cooled by ice-water bath after 5 s . Then 20 mL ethyl acetate was added. The mixture was centrifuged at 1200 rpm / min 1200 rpm / min 1200rpm//min1200 \mathrm{rpm} / \mathrm{min} for 5 min and washed with ethyl acetate three times and dried in vacuum at 70 ∘ C 70 ∘ C 70^(@)C70^{\circ} \mathrm{C} for 12 h . Fig. 1 shows the preparation process of MoS 2 − GO MoS 2 − GO MoS_(2)-GO\mathrm{MoS}_{2}-\mathrm{GO} and CSPbBr 3 − MoS 2 − GO CSPbBr 3 − MoS 2 − GO CSPbBr_(3)-MoS_(2)-GO\mathrm{CSPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites
在 50 mL 烧瓶中加入 5 mL 十八烯，然后向烧瓶中加入 5 mg MoS 2 5 mg MoS 2 5mgMoS_(2)5 \mathrm{mg} \mathrm{MoS}{ }_{2} （或 5 mg GO 或 5 mg MoS 2 5 mg MoS 2 5mgMoS_(2)5 \mathrm{mg} \mathrm{MoS}_{2} -GO），并在超声波下充分分散 30 分钟。然后在 N 2 N 2 N_(2)\mathrm{N}_{2} 的保护下向烧瓶中加入 0.188 mmol ( 69 mg ) PbBr 2 0.188 mmol ( 69 mg ) PbBr 2 0.188mmol(69mg)PbBr_(2)0.188 \mathrm{mmol}(69 \mathrm{mg}) \mathrm{PbBr}_{2} 。将溶液加热并保持在 120 ∘ C 120 ∘ C 120^(@)C120{ }^{\circ} \mathrm{C} 的温度下 1 小时，然后加入 0.5 mL 油酸和 0.5 mL 油胺。反应 30 分钟后，温度逐渐升高至 180 ∘ C 180 ∘ C 180^(@)C180^{\circ} \mathrm{C} ，向烧瓶中快速注入 0.4 mL 油酸铯，5 秒后冰水浴冷却，然后加入 20 mL 乙酸乙酯。混合物在 1200 rpm / min 1200 rpm / min 1200rpm//min1200 \mathrm{rpm} / \mathrm{min} 下离心 5 分钟，用乙酸乙酯洗涤三次，在 70 ∘ C 70 ∘ C 70^(@)C70^{\circ} \mathrm{C} 下真空干燥 12 小时。图 1 显示了 MoS 2 − GO MoS 2 − GO MoS_(2)-GO\mathrm{MoS}_{2}-\mathrm{GO} 和 CSPbBr 3 − MoS 2 − GO CSPbBr 3 − MoS 2 − GO CSPbBr_(3)-MoS_(2)-GO\mathrm{CSPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} 纳米复合材料的制备过程

2.6. Evaluation of photocatalytic degradation performance
2.6.光催化降解性能评估

The photocatalytic degradation of Sudan Red III by the composites of CsPbBr 3 , CsPbBr 3 − GO , CsPbBr 3 − MoS 2 CsPbBr 3 , CsPbBr 3 − GO , CsPbBr 3 − MoS 2 CsPbBr_(3),CsPbBr_(3)-GO,CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}, \mathrm{CsPbBr}_{3}-\mathrm{GO}, \mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} and CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-GO under xenon lamp were evaluated. 10 mg nanocomposites were dispersed into 30 mL 10 mg / L 30 mL 10 mg / L 30mL10mg//L30 \mathrm{~mL} 10 \mathrm{mg} / \mathrm{L} Sudan Red III solution respectively, stirred in darkness for 30 min to achieve adsorption-desorption equilibrium, and then stirred continuously under 300 W xenon lamp irradiation. The light
评估了 CsPbBr 3 , CsPbBr 3 − GO , CsPbBr 3 − MoS 2 CsPbBr 3 , CsPbBr 3 − GO , CsPbBr 3 − MoS 2 CsPbBr_(3),CsPbBr_(3)-GO,CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}, \mathrm{CsPbBr}_{3}-\mathrm{GO}, \mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} 和 CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} -GO 复合材料在氙灯下对苏丹红 III 的光催化降解作用。将 10 mg 纳米复合材料分别分散到 30 mL 10 mg / L 30 mL 10 mg / L 30mL10mg//L30 \mathrm{~mL} 10 \mathrm{mg} / \mathrm{L} 苏丹红 III 溶液中，在黑暗条件下搅拌 30 min 以达到吸附-解吸平衡，然后在 300 W 氙灯照射下持续搅拌。光
source was 10 cm away from the solution. After irradiation for an interval of time, 2.5 mL solution was taken out and centrifuged, the supernatant was separated and used for the UV-vis absorption measurement. The change of concentration of Sudan Red III can be judged by the change of the absorbance at the maximum absorption wavelength.
光源距离溶液 10 厘米。照射一段时间后，取出 2.5 mL 溶液并离心，分离上清液，用于紫外-可见吸收测量。苏丹红 III 浓度的变化可以通过最大吸收波长处吸光度的变化来判断。

2.7. Characterization methods
2.7.表征方法

The crystal structure of the samples was characterized by X-ray diffraction (XRD, Smartlab) with Cu K α Cu K α CuKalpha\mathrm{Cu} \mathrm{K} \alpha radiation ( λ = 1.5406 Å λ = 1.5406 Å lambda=1.5406"Å"\lambda=1.5406 \AAÅ ). The morphology and lattice of the samples were analyzed by transmission electron microscopy (TEM, JEOL JEM200CX). The absorption spectra of the samples were measured by ultraviolet spectrophotometer (SHIMADZU, UV-1750). The photoluminescence (PL) emission spectra of the samples were measured by fluorescence spectrometer (Hitachi, F-4600).
利用 X 射线衍射（XRD，Smartlab）和 Cu K α Cu K α CuKalpha\mathrm{Cu} \mathrm{K} \alpha 辐射（ λ = 1.5406 Å λ = 1.5406 Å lambda=1.5406"Å"\lambda=1.5406 \AAÅ ）对样品的晶体结构进行了表征。透射电子显微镜（TEM，JEOL JEM200CX）分析了样品的形态和晶格。用紫外分光光度计（SHIMADZU，UV-1750）测量了样品的吸收光谱。荧光光谱仪（Hitachi，F-4600）测量了样品的光致发光（PL）发射光谱。

3. Results and discussion
3.结果和讨论

3.1. The characterizations of photocatalysts
3.1.光催化剂的特性

Fig. 2(a) is the XRD patterns of CsPbBr 3 , MoS 2 , CsPbBr 3 − GO CsPbBr 3 , MoS 2 , CsPbBr 3 − GO CsPbBr_(3),MoS_(2),CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}, \mathrm{MoS}_{2}, \mathrm{CsPbBr}_{3}-\mathrm{GO}, CsPbBr 3 − MoS 2 , MoS 2 − GO CsPbBr 3 − MoS 2 , MoS 2 − GO CsPbBr_(3)-MoS_(2),MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}, \mathrm{MoS}_{2}-\mathrm{GO} and CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} - GO nanocomposites. The diffraction peaks at 15.21 , 21.49 , 30.69 , 34.19 , 37.60 15.21 , 21.49 , 30.69 , 34.19 , 37.60 15.21,21.49,30.69,34.19,37.6015.21,21.49,30.69,34.19,37.60 and 43.69 ∘ 43.69 ∘ 43.69^(@)43.69^{\circ} correspond to the crystal planes of CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} (100), (110), (200), (210), ( 2 ― 11 2 ¯ 11 bar(2)11\overline{2} 11 ) and (202) of the standard card (JCPDS No. 18-0364), respectively. It shows that the perovskite QDs are well crystallized and no other phases are observed. The diffraction peaks of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} at 14.5, 22.0, 33.8 , 39.6 33.8 , 39.6 33.8,39.633.8,39.6 and 59.2 ∘ 59.2 ∘ 59.2^(@)59.2^{\circ} correspond to the characteristic planes of (002), (100), (103), (105) and (110) of hexagonal MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}, respectively. When GO was compounded with CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} or MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}, there was no new characteristic peaks compared with pure MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} due to the amorphous nature of GO. The XRD pattern of CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} and CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites shows similar peaks, both of them contained both characteristic peaks of CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} and MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}, which indicated that the two phases coexisted in the composite. Further characterizations of TEM and Raman are needed to prove the existence of GO. Fig. 2(b) shows the Raman spectra of CsPbBr 3 , GO , CsPbBr 3 − GO , CsPbBr 3 − MoS 2 , MoS 2 − GO CsPbBr 3 , GO , CsPbBr 3 − GO , CsPbBr 3 − MoS 2 , MoS 2 − GO CsPbBr_(3),GO,CsPbBr_(3)-GO,CsPbBr_(3)-MoS_(2),MoS_(2)-GO\mathrm{CsPbBr}_{3}, \mathrm{GO}, \mathrm{CsPbBr}_{3}-\mathrm{GO}, \mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}, \mathrm{MoS}_{2}-\mathrm{GO} and CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-GO nanocomposites. A weak, broad band at 310 cm − 1 310 cm − 1 310cm^(-1)310 \mathrm{~cm}^{-1} is assigned to the second-order vibrational phonon mode of [ PbBr 6 ] 4 − PbBr 6 4 − [PbBr_(6)]^(4-)\left[\mathrm{PbBr}_{6}\right]^{4-} octahedron of the CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} crystal with Pnma phase [32,33]. There were two strong peaks at 1357 cm − 1 1357 cm − 1 1357cm^(-1)1357 \mathrm{~cm}^{-1} and 1593 cm − 1 1593 cm − 1 1593cm^(-1)1593 \mathrm{~cm}^{-1}. The peak at 1357 cm − 1 1357 cm − 1 1357cm^(-1)1357 \mathrm{~cm}^{-1} corresponds to the D peak of sp3-carbon atom, which is the vibration absorption peak of carbon atom on GO surface group. The peak at 1593 cm − 1 cm − 1 cm^(-1)\mathrm{cm}^{-1} corresponds to the G peak of sp2-carbon atom, which is the vibration absorption peak of carbon skeleton atom in GO [34]. The intensity ratio of D peak to G peak ( I D / I G I D / I G I_(D)//I_(G)I_{\mathrm{D}} / I_{\mathrm{G}} ) of GO in nanocomposites is 1.01 , which is close to pure GO ( I D / I G = 1.00 ) I D / I G = 1.00 (I_(D)//I_(G)=1.00)\left(I_{\mathrm{D}} / I_{\mathrm{G}}=1.00\right), indicating that there are few structural defects in the nanocomposites [35,36]. The Raman peaks of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} are weak compared to the strong D and G peaks of GO. The peaks at 383 cm − 1 383 cm − 1 383cm^(-1)383 \mathrm{~cm}^{-1} and 412 cm − 1 412 cm − 1 412cm^(-1)412 \mathrm{~cm}^{-1} correspond to the vibration modes of E 2 g 1 E 2 g 1 E_(2g)^(1)E_{2 g}^{1} and A 1 g A 1 g A_(1g)A_{1 g} of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} [37]. The Raman results matches well with XRD results, which shows that CsPbBr 3 , MoS 2 CsPbBr 3 , MoS 2 CsPbBr_(3),MoS_(2)\mathrm{CsPbBr}_{3}, \mathrm{MoS}_{2} and GO are well combined in the nanocomposite.
图 2(a) 是 CsPbBr 3 , MoS 2 , CsPbBr 3 − GO CsPbBr 3 , MoS 2 , CsPbBr 3 − GO CsPbBr_(3),MoS_(2),CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}, \mathrm{MoS}_{2}, \mathrm{CsPbBr}_{3}-\mathrm{GO} 、 CsPbBr 3 − MoS 2 , MoS 2 − GO CsPbBr 3 − MoS 2 , MoS 2 − GO CsPbBr_(3)-MoS_(2),MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}, \mathrm{MoS}_{2}-\mathrm{GO} 和 CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} - GO 纳米复合材料的 XRD 图样。在 15.21 , 21.49 , 30.69 , 34.19 , 37.60 15.21 , 21.49 , 30.69 , 34.19 , 37.60 15.21,21.49,30.69,34.19,37.6015.21,21.49,30.69,34.19,37.60 和 43.69 ∘ 43.69 ∘ 43.69^(@)43.69^{\circ} 处的衍射峰分别对应于标准卡（JCPDS 编号：18-0364）中 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} (100)、(110)、(200)、(210)、( 2 ― 11 2 ¯ 11 bar(2)11\overline{2} 11 ) 和 (202) 的晶面。这表明过氧化物质点结晶良好，没有观察到其他相。 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 在 14.5、22.0、 33.8 , 39.6 33.8 , 39.6 33.8,39.633.8,39.6 和 59.2 ∘ 59.2 ∘ 59.2^(@)59.2^{\circ} 处的衍射峰分别对应于六方 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 的(002)、(100)、(103)、(105)和(110)特征面。当 GO 与 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} 或 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 复合时，由于 GO 的无定形性质，与纯 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 相比没有出现新的特征峰。 CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} 和 CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} 纳米复合材料的 XRD 图谱显示出相似的峰值，它们都包含 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} 和 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 的特征峰，这表明复合材料中这两相共存。要证明 GO 的存在，还需要进一步的 TEM 和拉曼表征。图 2(b) 显示了 CsPbBr 3 , GO , CsPbBr 3 − GO , CsPbBr 3 − MoS 2 , MoS 2 − GO CsPbBr 3 , GO , CsPbBr 3 − GO , CsPbBr 3 − MoS 2 , MoS 2 − GO CsPbBr_(3),GO,CsPbBr_(3)-GO,CsPbBr_(3)-MoS_(2),MoS_(2)-GO\mathrm{CsPbBr}_{3}, \mathrm{GO}, \mathrm{CsPbBr}_{3}-\mathrm{GO}, \mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}, \mathrm{MoS}_{2}-\mathrm{GO} 和 CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} -GO 纳米复合材料的拉曼光谱。在 310 cm − 1 310 cm − 1 310cm^(-1)310 \mathrm{~cm}^{-1} 处有一个微弱的宽波段，该波段属于具有 Pnma 相的 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} 晶体的 [ PbBr 6 ] 4 − PbBr 6 4 − [PbBr_(6)]^(4-)\left[\mathrm{PbBr}_{6}\right]^{4-} 八面体的二阶振动声子模式[32,33]。在 1357 cm − 1 1357 cm − 1 1357cm^(-1)1357 \mathrm{~cm}^{-1} 和 1593 cm − 1 1593 cm − 1 1593cm^(-1)1593 \mathrm{~cm}^{-1} 处有两个强峰值。 1357 cm − 1 1357 cm − 1 1357cm^(-1)1357 \mathrm{~cm}^{-1} 处的峰对应于 sp3 碳原子的 D 峰，是 GO 表面基团上碳原子的振动吸收峰。1593 cm − 1 cm − 1 cm^(-1)\mathrm{cm}^{-1} 处的峰对应于 sp2 碳原子的 G 峰，即 GO 中碳原子骨架的振动吸收峰 [34]。纳米复合材料中 GO 的 D 峰与 G 峰（ I D / I G I D / I G I_(D)//I_(G)I_{\mathrm{D}} / I_{\mathrm{G}} ）的强度比为 1。01 ，这与纯 GO ( I D / I G = 1.00 ) I D / I G = 1.00 (I_(D)//I_(G)=1.00)\left(I_{\mathrm{D}} / I_{\mathrm{G}}=1.00\right) 接近，表明纳米复合材料中几乎没有结构缺陷 [35,36]。与 GO 的强 D 峰和 G 峰相比， MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 的拉曼峰较弱。 383 cm − 1 383 cm − 1 383cm^(-1)383 \mathrm{~cm}^{-1} 和 412 cm − 1 412 cm − 1 412cm^(-1)412 \mathrm{~cm}^{-1} 的峰值对应于 E 2 g 1 E 2 g 1 E_(2g)^(1)E_{2 g}^{1} 和 A 1 g A 1 g A_(1g)A_{1 g} 的振动模式 [37]。拉曼结果与 XRD 结果非常吻合，这表明 CsPbBr 3 , MoS 2 CsPbBr 3 , MoS 2 CsPbBr_(3),MoS_(2)\mathrm{CsPbBr}_{3}, \mathrm{MoS}_{2} 与 GO 在纳米复合材料中结合得很好。
Fig. 3 is the TEM images of GO and MoS 2 − GO MoS 2 − GO MoS_(2)-GO\mathrm{MoS}_{2}-\mathrm{GO} as well as CsPbBr 3 − CsPbBr 3 − CsPbBr_(3)-\mathrm{CsPbBr}_{3}- MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}-GO nanocomposites. The GO lamellae are very thin (Fig. 3(a)). Because of the strong π − π π − π pi-pi\pi-\pi conjugation between GO lamellae, the GO lamellae overlap slightly. Fig. 3(b) shows that MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} belts grown on GO lamellae surface. There is a slight agglomeration of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} belts and forms flower-like clusters since no surfactants were added in the process of synthesizing MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}. Fig. 3© clearly shows that CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs and MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} nanosheets are closely attached to GO surface, in which CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs are about 15 nm in size and dispersed uniformly on GO surface. The lattice fringes can be clearly seen in the HRTEM of Fig. 3(d), where the long belts are MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}, and the lattice spacing of 0.62 nm corresponds to the
图 3 是 GO 和 MoS 2 − GO MoS 2 − GO MoS_(2)-GO\mathrm{MoS}_{2}-\mathrm{GO} 以及 CsPbBr 3 − CsPbBr 3 − CsPbBr_(3)-\mathrm{CsPbBr}_{3}- MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} -GO 纳米复合材料的 TEM 图像。GO 薄层非常薄（图 3(a)）。由于 GO 片层之间存在较强的 π − π π − π pi-pi\pi-\pi 共轭作用，GO 片层略有重叠。图 3(b) 显示， MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 带生长在 GO 片层表面。由于在合成 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 的过程中没有添加表面活性剂，因此 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 带有轻微的聚集，并形成了花朵状的团簇。图 3© 清楚地表明， CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs 和 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 纳米片紧密地附着在 GO 表面，其中 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs 大小约为 15 nm，均匀地分散在 GO 表面。从图 3(d) 的 HRTEM 中可以清楚地看到晶格条纹，其中长带为 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} ，晶格间距为 0.62 nm，对应于 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QD 的晶格条纹。
Fig. 3. TEM images of (a) GO and (b) MoS 2 − GO MoS 2 − GO MoS_(2)-GO\mathrm{MoS}_{2}-\mathrm{GO}, © LRTEM and (d) HRTEM images of CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-GO nanocomposites.
图 3.(a) GO 和 (b) MoS 2 − GO MoS 2 − GO MoS_(2)-GO\mathrm{MoS}_{2}-\mathrm{GO} 的 TEM 图像，© CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} -GO 纳米复合材料的 LRTEM 和 (d) HRTEM 图像。
Fig. 4. (a) Picture of Sudan Red III solution degraded by CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-GO nanocomposites with different duration time. Absorption spectra of Sudan Red III degraded by (b) CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs, © CsPbBr 3 − GO CsPbBr 3 − GO CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}-\mathrm{GO} nanocomposites, (d) CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} nanocomposites and (e) CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites with illumination time, (f) concentration ( C t / C 0 ) C t / C 0 (C_(t)//C_(0))\left(C_{t} / C_{0}\right) changes of Sudan Red III with different catalysts under visible light irradiation.
图 4：(a) CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} -GO 纳米复合材料在不同持续时间内降解苏丹红 III 溶液的图片。(b) CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs、© CsPbBr 3 − GO CsPbBr 3 − GO CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}-\mathrm{GO} 纳米复合材料、(d) CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} 纳米复合材料和 (e) CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} 纳米复合材料降解苏丹红 III 的吸收光谱随光照时间的变化；(f) 可见光照射下不同催化剂降解苏丹红 III 的浓度 ( C t / C 0 ) C t / C 0 (C_(t)//C_(0))\left(C_{t} / C_{0}\right) 变化。
MoS 2 ( 002 ) MoS 2 ( 002 ) MoS_(2)(002)\mathrm{MoS}_{2}(002) crystal plane of the hexagonal system. The lattice spacing of 0.58 nm corresponds to (100) lattice plane of CsPbBr 3 . CsPbBr 3 CsPbBr 3 . CsPbBr 3 CsPbBr_(3).CsPbBr_(3)\mathrm{CsPbBr}_{3} . \mathrm{CsPbBr}_{3} QDs, MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} nanoribbons and GO lamellae are closely attached to each other.
MoS 2 ( 002 ) MoS 2 ( 002 ) MoS_(2)(002)\mathrm{MoS}_{2}(002) 六方晶系的晶面。0.58 nm的晶格间距对应于 CsPbBr 3 . CsPbBr 3 CsPbBr 3 . CsPbBr 3 CsPbBr_(3).CsPbBr_(3)\mathrm{CsPbBr}_{3} . \mathrm{CsPbBr}_{3} QD 的（100）晶格面， MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 纳米带和 GO 片层彼此紧密相连。

3.2. Photocatalytic degradation evolution
3.2.光催化降解演化

The photocatalytic degradation of Sudan Red III of above samples
上述样品光催化降解苏丹红 III 的情况
under a 300 W Xe lamp experiments were carried out. Fig. 4 shows the photocatalytic degradation of Sudan Red III with different catalysts. From Fig. 4(a), it can be clearly seen that when CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-GO nanocomposites is used as catalyst, Sudan Red III solution gradually changes from orange to colorless after 100 min of illumination, which intuitively reflects that Sudan Red III was absolutely degraded by nanocomposites. Fig. 4(b) shows that Sudan Red III is gradually
在 300 W Xe 灯下进行了实验。图 4 显示了不同催化剂对苏丹红 III 的光催化降解情况。从图 4（a）中可以清楚地看到，当使用 CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} -GO 纳米复合材料作为催化剂时，苏丹红 III 溶液在 100 分钟的光照后由橙色逐渐变为无色，直观地反映出苏丹红 III 被纳米复合材料完全降解。图 4(b) 显示，苏丹红 III 在纳米复合材料的作用下逐渐由橙色变为无色。
Fig. 5. Absorption spectra of CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs, CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} nanocomposites, CsPbBr 3 − GO CsPbBr 3 − GO CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}-\mathrm{GO} nanocomposites and CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites.
图 5. CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs、 CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} 纳米复合材料、 CsPbBr 3 − GO CsPbBr 3 − GO CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}-\mathrm{GO} 纳米复合材料和 CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} 纳米复合材料的吸收光谱。
degraded by pure CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs, indicating that pure CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs has poor catalytic ability. This is consistent with our previous results [20]. From Fig. 4©, we can see that the degradation performance of Sudan Red III is greatly enhanced after GO is compounded. However, Fig. 4(d) shows that the photocatalytic degradation performance of Sudan Red III by CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} is relatively poor, which is due to the agglomeration of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} in the absence of GO. As can be seen from Fig. 4(e), Sudan Red III was rapidly degraded in a short period of 100 min when CsPbBr 3 − MoS 2 − CsPbBr 3 − MoS 2 − CsPbBr_(3)-MoS_(2^(-))\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2^{-}} GO nanocomposites were used as a catalyst. Fig. 4(f) visually reflects the degradation rate of Sudan Red III by different catalysts after 100 min of illumination. The degradation rate of Sudan Red III expressed as ( C 0 − C t ) C 0 − C t (C_(0)-C_(t))\left(\mathrm{C}_{0}-\mathrm{C}_{\mathrm{t}}\right) / C 0 C 0 C_(0)\mathrm{C}_{0} by pure CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs was, CsPbBr 3 − GO , CsPbBr 3 − MoS 2 CsPbBr 3 − GO , CsPbBr 3 − MoS 2 CsPbBr_(3)-GO,CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{GO}, \mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} and CsPbBr 3 − CsPbBr 3 − CsPbBr_(3)-\mathrm{CsPbBr}_{3}- MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}-GO within 100 min of light exposure was 30 % , 70 % , 8 % 30 % , 70 % , 8 % 30%,70%,8%30 \%, 70 \%, 8 \% and 93.1 % 93.1 % 93.1%93.1 \%, respectively. This indicates that the degradation rate of catalyst CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} is 3.1 times of that of pure CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs. The introduction of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}-GO greatly improves the photocatalytic degradation performance of perovskite QDs.
CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs降解，表明纯 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs的催化能力较差。这与我们之前的研究结果一致[20]。从图 4©可以看出，复合 GO 后，苏丹红 III 的降解性能大大提高。然而，从图 4(d) 可以看出， CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} 对苏丹红 III 的光催化降解性能相对较差，这是由于 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} 在没有 GO 的情况下发生了团聚。从图 4(e)可以看出，当使用 CsPbBr 3 − MoS 2 − CsPbBr 3 − MoS 2 − CsPbBr_(3)-MoS_(2^(-))\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2^{-}} GO 纳米复合材料作为催化剂时，苏丹红 III 在 100 分钟的短时间内迅速降解。图 4(f) 直观地反映了不同催化剂在光照 100 分钟后对苏丹红 III 的降解率。在光照 100 分钟内，纯 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs 对苏丹红 III 的降解率为 ( C 0 − C t ) C 0 − C t (C_(0)-C_(t))\left(\mathrm{C}_{0}-\mathrm{C}_{\mathrm{t}}\right) / C 0 C 0 C_(0)\mathrm{C}_{0} ， CsPbBr 3 − GO , CsPbBr 3 − MoS 2 CsPbBr 3 − GO , CsPbBr 3 − MoS 2 CsPbBr_(3)-GO,CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{GO}, \mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} 和 CsPbBr 3 − CsPbBr 3 − CsPbBr_(3)-\mathrm{CsPbBr}_{3}- MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} -GO 对苏丹红 III 的降解率分别为 30 % , 70 % , 8 % 30 % , 70 % , 8 % 30%,70%,8%30 \%, 70 \%, 8 \% 和 93.1 % 93.1 % 93.1%93.1 \% 。这表明催化剂 CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} 的降解率是纯 CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs 的 3.1 倍。 MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} -GO 的引入大大提高了包晶QDs的光催化降解性能。

3.3. Absorption, PL and time-resolved transient PL analysis
3.3.吸收、聚合和时间分辨瞬态聚合分析

Generally, the catalytic performance of semiconductor nanocrystals depends on the particle size (diffusion distance), crystallinity, defects, energy band structure and carrier transfer rate, and so on. From the above TEM results, the CsPbBr 3 QDs are only 6-10 nm, far less than the diffusion length, which is very conducive for carriers to reach the surface of the particles and contact with Sudan Red III. XRD and Raman analysis showed that CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} crystallized well, which was beneficial to improve the photocatalytic performance. Then we need to further consider the band structure and carrier transfer of the nanocomposites. Thus, PL, time-resolved transient PL decay spectra of above samples were conducted. Fig. 5 shows the absorption spectra of CsPbBr 3 QDs 2 CsPbBr 3 − CsPbBr 3 QDs 2 CsPbBr 3 − CsPbBr_(3)QDs^(2)CsPbBr_(3^(-))\mathrm{CsPbBr}_{3} \mathrm{QDs}^{2} \mathrm{CsPbBr}_{3^{-}} MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} nanocomposites, CsPbBr 3 − GO CsPbBr 3 − GO CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}-\mathrm{GO} nanocomposites and CsPbBr 3 − MoS 2 − CsPbBr 3 − MoS 2 − CsPbBr_(3)-MoS_(2^(-))\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2^{-}} GO nanocomposites. It can be seen that CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs has strong absorption in the wavelength range below 529 nm . There is an acromion at 505 nm due to the good monodispersity of CsPbBr 3 QDs . When CsPbBr 3 − CsPbBr 3 QDs . When  CsPbBr 3 − CsPbBr_(3)QDs_(". When ")CsPbBr_(3^(-))\mathrm{CsPbBr}_{3} \mathrm{QDs}_{\text {. When }} \mathrm{CsPbBr}_{3^{-}} GO nanocomposites were formed, the visible-light absorption was much stronger than that of pure CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs, and the color of the nanocomposites was deeper. This is well understood because GO with high C/ O ratio is a narrow band semiconductor material with strong light absorption in visible to near-infrared regions. When combined CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs with MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} belts, the absorption was enhanced and the acromion at 505 nm was more obvious due to the higher absorption of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}. The optical absorption ability of ternary CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites of was greatly enhanced compared to pure CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs. This indicates that the introduction of GO and MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} can enhance the absorption, 
Fig. 6. (a) PL and (b) time-resolved transient PL decay spectra of CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs, CsPbBr 3 − GO , CsPbBr 3 − MoS 2 CsPbBr 3 − GO , CsPbBr 3 − MoS 2 CsPbBr_(3)-GO,CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{GO}, \mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} and CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites. 
produce more photogenerated carriers and is expected to be helpful to the final photocatalytic performance. 
Room-temperature PL spectroscopy were performed for CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs, CsPbBr 3 − GO CsPbBr 3 − GO CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}-\mathrm{GO} nanocomposites, and CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites, respectively, as shown in Fig. 6(a). The emission intensity of CsPbBr 3 − GO CsPbBr 3 − GO CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}-\mathrm{GO} nanocomposites is much lower than that of pure CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs since the introduction of GO can provide internal radiation channels for transfer excited electrons. The PL of CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} - GO nanocomposites is absolutely quenched and much lower than that of pure CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} nanocomposites. Because of the high conductivity of GO, which can provide an additional energy-transfer pathway besides the intrinsic radiative channel for electron transfer, the photogenerated electron hole pairs in the nanocomposites can be separated quickly and charge recombination can be suppressed effectively, which ultimately leads to the quenching of fluorescence [38]. However, the PL of CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} nanocomposites is slightly higher than that of pure CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs, which is due to the agglomeration of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} in the absence of GO, which provides space for the recombination of photogenerated electrons and holes and promotes their recombination. The existence of GO is very important for getting uniformly dispersed MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} and CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs. The good dispersibility of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} and CsPbBr 3 QDs CsPbBr 3 QDs CsPbBr_(3)QDs\mathrm{CsPbBr}_{3} \mathrm{QDs} on the surface of GO, which effectively reduces the defects, is also helpful to transfer electrons and inhibit charge recombination. 
To further verify this viewpoint, time-resolved fluorescence emission decay spectra for above samples were recorded and the standardized decay curves were fitted, as shown in Fig. 5(b). The average fluorescence lifetimes of CsPbBr 3 QDs , CsPbBr 3 − GO CsPbBr 3 QDs , CsPbBr 3 − GO CsPbBr_(3)QDs,CsPbBr_(3)-GO\mathrm{CsPbBr}_{3} \mathrm{QDs}, \mathrm{CsPbBr}_{3}-\mathrm{GO} nanocomposites, and CsPbBr 3 − CsPbBr 3 − CsPbBr_(3)-\mathrm{CsPbBr}_{3}- MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}-GO nanocomposites were determined to be 12.4 ns , 37.1 ns 12.4 ns , 37.1 ns 12.4ns,37.1ns12.4 \mathrm{~ns}, 37.1 \mathrm{~ns} and 
Fig. 7. (a) Schematic illustration of the energy diagram and electrons transfer route and (b) schematic structure for CsPbBr 3 − MoS 2 − GO − CsPbBr 3 − MoS 2 − GO − CsPbBr_(3)-MoS_(2)-GO^(-)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO}^{-}nanocomposites. 
81.0 ns , respectively. The significantly increased lifetime of CsPbBr 3 − CsPbBr 3 − CsPbBr_(3^(-))\mathrm{CsPbBr}_{3^{-}} MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2}-GO nanocomposites compared with that of bare CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs and CsPbBr 3 − GO CsPbBr 3 − GO CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}-\mathrm{GO} nanocomposites illustrated that the introduction of GO and MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} could effectively enhance the separation of photogenerated electron and hole pairs. 

3.4. Proposed possible mechanism 

Base on experiments and analysis above, the possible mechanism of photocatalytic degradation of Sudan Red III has been discussed. As shown in Fig. 7, under the irradiation of 300 W xenon lamp, the valence band electrons of CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs are excited to the conduction band, and holes are generated in the valence band to form electron-hole pairs. The conductive band (CB) potential of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} and GO / GO ∙ − GO / GO ∙ − GO//GO∙-\mathrm{GO} / \mathrm{GO} \bullet- are about -0.2 eV versus NHE, and -0.08 eV versus NHE, respectively [39]. Both of them are more positive than the CB potential of CsPbBr 3 ( − 1.02 eV CsPbBr 3 ( − 1.02 eV CsPbBr_(3)(-1.02eV\mathrm{CsPbBr}_{3}(-1.02 \mathrm{eV} versus NHE) [40]. Thus, the conduction band electrons of CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} can be transferred from the CB of CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} to the CB of the surface of GO. CH Chen and CM Chiang suggested that graphene or GO can serve as a photosensitizer responsible for transferring electrons into the CB of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} [41]. The mobility of these electrons on the GO sheet is very high, photoelectrons in GO can thus be further transferred to MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} nanoribbons via GO sheet (GO as electron transport channel). MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} nanoribbons in CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites can accept electrons and act as effective electron collectors and the active site of O 2 O 2 O_(2)\mathrm{O}_{2}. Photogenerated electrons can convert oxygen in air into free radicals, which can degrade Sudan Red III. The holes in valence bands can be trapped by H 2 O H 2 O H_(2)O\mathrm{H}_{2} \mathrm{O} on the surface of materials to form ∙ OH ∙ OH ∙OH\bullet \mathrm{OH}, which has strong oxidation ability and can directly degrade Sudan Red III into non-toxic and harmless substances. CH Chen and coworkers reported that graphene or GO thickness can control the performance of photocatalysis, and threelayer graphene stacks showed the highest activity. This paves a way for our future work and the related work is in progress [42]. 

4. Conclusion 

The paper presents the first report on the photocatalytic degradation performance of CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposite. CsPbBr 3 QDs CsPbBr 3 QDs CsPbBr_(3)QDs\mathrm{CsPbBr}_{3} \mathrm{QDs}, CsPbBr 3 − MoS 2 , CsPbBr 3 − GO CsPbBr 3 − MoS 2 , CsPbBr 3 − GO CsPbBr_(3)-MoS_(2),CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}, \mathrm{CsPbBr}_{3}-\mathrm{GO} and CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposite photocatalysts were successfully synthesized. XRD and TEM results show that CsPbBr 3 CsPbBr 3 CsPbBr_(3)\mathrm{CsPbBr}_{3} QDs and MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} nanoribbons with good crystallinity and uniform size are well attached to GO surface. The photocatalytic degradation of Sudan Red III by nanocomposites catalyst showed that CsPbBr 3 − MoS 2 CsPbBr 3 − MoS 2 CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-GO nanocomposites exhibited much excellent photocatalytic degradation performance than pure CsPbBr 3 , CsPbBr 3 − MoS 2 CsPbBr 3 , CsPbBr 3 − MoS 2 CsPbBr_(3),CsPbBr_(3)-MoS_(2)\mathrm{CsPbBr}_{3}, \mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2} and CsPbBr 3 − GO CsPbBr 3 − GO CsPbBr_(3)-GO\mathrm{CsPbBr}_{3}-\mathrm{GO} composites. The degradation rate is 3.1 times of that of pure perovskite. The main reason is that GO reduces the overlap of MoS 2 MoS 2 MoS_(2)\mathrm{MoS}_{2} nanoplates, has high conductivity and suitable band structure, provides more active sites. Moreover, GO as an electron transport channel can effectively reduce carrier recombination, which ultimately improves the 
photocatalytic degradation performance of CsPbBr 3 − MoS 2 − GO CsPbBr 3 − MoS 2 − GO CsPbBr_(3)-MoS_(2)-GO\mathrm{CsPbBr}_{3}-\mathrm{MoS}_{2}-\mathrm{GO} nanocomposites. Our study paves a new way to take the advantage of perovskite materials for promising applications in photocatalytic degradation of pollutants. 

CRediT authorship contribution statement 

Hongmei Ju: Investigation, Writing - original draft. Tingsen Fang: Formal analysis. Yun Zhou: Investigation. Xianbin Feng: . Tinghui Song: Validation. Feng Lu: . Wenchao Liu: Supervision, Formal analysis, Writing - original draft. 

Declaration of Competing Interest 

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. 

Acknowledgment 

This work was supported by the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No. 17KJA430009) and the National Natural Science Foundation of China (51202108). Dr. Liu thanks Prof. Wei Huang of Nanjing Tech University and Northwestern Polytechnical University for his helpful suggestion. 

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    • Corresponding author. 
    E-mail address: iamwcliu@njtech.edu.cn (W. Liu). 
    https://doi.org/10.1016/j.apsusc.2021.149452
    Received 12 November 2020; Received in revised form 20 February 2021; Accepted 28 February 2021 
    Available online 2 March 2021 
    0169-4332/© 2021 Elsevier B.V. All rights reserved.