ZnS/还原氧化石墨烯复合材料的制备及光催化性能

水热法一步合成ZnS/还原氧化石墨烯（ZnS/RGO）复合材料,通过XRD、FTIR、Raman、SEM分析溶剂（乙醇、水）对ZnS/RGO复合材料形貌和结构的影响。结果表明,以乙醇为溶剂制备的ZnS颗粒尺寸小、均匀分散在石墨烯片层上,在形成ZnS纳米颗粒的同时将氧化石墨烯（GO）还原成石墨烯。对亚甲基蓝（MB）的光催化结果显示,ZnS/RGO复合材料具有优异的光催化性能,其光催化速率是纯ZnS颗粒的3.7倍,石墨烯作为优良光生电子的传输通道和收集体能够降低光生电子-空穴对的重新结合率,极大提高了ZnS/RGO复合材料的光催化性能。      

石墨烯纳米复合材料在光催化应用中的研究进展

石墨烯即"单层石墨片",是近年来人们发现和合成的具有独特的单原子层、二维晶体结构的纳米材料.利用石墨烯与半导体材料复合以提高光催化活性,已成为新型光催化研究的热点之一.对石墨烯及其应用进行了简单的叙述,重点报道了石墨烯在光催化制氢、光催化降解和光电转换应用方面的研究动态,以及用不同方法合成的石墨烯光催化复合材料,为以后石墨烯与其他材料的复合提供了实验依据.     

原位反应制备ZnS/还原氧化石墨烯复合材料及其光催化性能

以氧化石墨烯和ZnAc2为反应前驱物,采用二甲基亚砜(DMSO)作为硫源和反应溶剂,通过一步溶剂热法原位制备出负载ZnS的还原氧化石墨烯(RGO)复合材料(ZnS/RGO)。采用SEM、XRD、激光拉曼(Raman)和荧光光谱对样品的微观形貌和化学结构进行表征。结果显示:原位反应制备的ZnS/RGO复合材料是由呈圆球状并均匀负载的纳米ZnS和6~7层RGO层状结构组成;在模拟紫外光照射下,对甲基橙污染物的光催化结果表明,ZnS/RGO复合材料的降解效率明显高于纯ZnS;同时,在多次循环催化过程中,ZnS/RGO复合材料的光催化效率仍基本保持不变,表明原位反应使ZnS与RGO结合增强。荧光光谱结果表明,ZnS/RGO复合材料光催化效率增强的主要原因在于ZnS中光生电子通过RGO得到有效的分离,进而延长了电子-空穴的复合效率。     

rGO/ZnO纳米复合材料的制备及其光催化降解性能及机理研究

采用一锅法制备具有可见光活性的还原氧化石墨烯(rGO)/ZnO纳米复合材料,将其应用于光催化降解罗丹明B(RhB),并获得了优异的降解效果。结果表明：该复合材料具有六方纤锌矿结构,rGO均匀包覆在ZnO上,表面光滑呈现出颗粒及不规则片状。rGO/ZnO对RhB的降解率为97.8%,催化活性优于单独的ZnO。自由基捕获实验表明,光催化降解RhB的活性物种主要是·OH^-和·O^-₂,并由此推测了光催化降解机理。     

Pt-TiO_2-还原氧化石墨烯纳米复合材料的制备及氧还原性能

制备一种具有高氧还原电催化活性的Pt-Ti O2-还原氧化石墨烯复合材料;采用X射线衍射、扫描电镜、透射电镜、高分辨透射电镜和拉曼光谱分析手段对催化剂的组成和微观结构进行表征。结果表明:氧化石墨烯在复合材料的合成过程中被还原为还原氧化石墨烯,纳米Pt与Ti O2颗粒均匀地附着在还原氧化石墨烯的片层上形成Pt-Ti O2-还原氧化石墨烯复合材料;该复合材料氧还原起始电位为-0.20 V左右,通过Koutecky-Levich方程计算得到电催化过程中复合材料的交换电流密度为10-6~10-5m A/cm2,16 000 s的计时电流测试后其相对电流值高达起始值的88%以上。     

TiO2/石墨烯纳米复合材料的合成及其光催化应用研究进展

以石墨烯材料修饰TiO2半导体光催化材料能够促进电子-空穴的有效分离,增大半导体表面的氧化物种富集程度,提高光催化活性。因而石墨烯-TiO2复合材料在光催化领域中被广泛研究。综述了TiO2负载在石墨烯膜/片上结构、TiO2-石墨烯异质结结构、TiO2-石墨烯核-壳式结构、TiO2-石墨烯及其他掺杂物纳米复合材料的制备,及其在光催化应用中的最新研究进展。     

两步水热法制备还原氧化石墨烯/纳米TiO_2复合材料及其光催化性能

为研究由还原氧化石墨烯(RGO)和具有高活性晶面的TiO_2组成的复合材料的制备方法及其光催化性能,首先采用两步水热法制备了RGO/纳米TiO_2复合材料:第1步为合成暴露高活性晶面的纳米TiO_2;第2步为将合成的纳米TiO_2与氧化石墨烯(GO)复合,形成RGO/纳米TiO_2复合材料。然后,利用XRD、SEM、X射线光电子能谱仪和紫外-可见漫反射光谱等手段对制备的暴露不同晶面的纳米TiO_2和RGO/纳米TiO_2复合材料进行了表征,评价了其光催化性能。结果表明:在水热法的第1步中,通过调节HF的浓度能可控制备出具有高活性的(001)和(101)晶面的纳米TiO_2,氟原子在纳米TiO_2中以物理吸附态和化学结合态这2种形态存在;在第2步后,GO与纳米TiO_2复合形成RGO/纳米TiO_2复合材料,同时在此过程中GO被转化成RGO。在紫外光照射下,两步水热法合成的RGO/纳米TiO_2复合材料具有很好的光催化性能,明显优于商用TiO_2(P25)和纳米TiO_2的。RGO/纳米TiO_2复合材料的光催化性能有明显的提高,RGO和TiO_2暴露的晶面对光催化活性有影响。     

纳米银/三维还原氧化石墨烯复合材料的制备及其催化性能研究

为解决纳米银催化剂易团聚的问题,选择三维还原氧化石墨烯(3D-rGO)作为载体材料,采用一步绿色水热法制备了纳米银/三维还原氧化石墨烯(Ag/3D-rGO)复合材料,采用SEM、XRD、FTIR、Raman、XPS等方法对材料的形貌和结构进行了系统的表征,并在室温下以对硝基苯酚(4-NP)的催化还原反应为模型,考察了所得复合材料的催化性能。结果表明,成功制备出了Ag/3D-rGO纳米复合材料,材料内部呈3D多孔网络结构,Ag纳米颗粒均匀附着在孔壁表面,颗粒的平均粒径为67 nm,无明显团聚;Ag/3D-rGO纳米复合材料可以在2 min内实现4-NP的催化还原,该催化反应过程遵循一级催化动力学反应规律,对应的一级催化动力学常数为1.8694 min^-1,高于现有报道中同类材料。研究的材料制备方法简便,催化性能优异,在工业催化和环境保护领域具有广阔的应用前景。     

丁基橡胶/还原氧化石墨烯复合材料的制备及性能

采用水合肼(HH)为还原剂制备还原氧化石墨烯(rGO),以rGO作为增强填料,丁基胶乳为基体,通过改进的超声胶乳混合和原位还原工艺,制备了力学性能优异的丁基橡胶(IIR)/rGO复合材料。结果表明,在IIR基体中添加较低含量rGO时,rGO显示完全剥离和均匀分散的状态;rGO由于具有较高的比表面积,可以提高其与IIR基体之间的界面相互作用,使得IIR/rGO复合材料的拉伸强度和断裂伸长率共同增大;对比纯IIR,IIR/rGO复合材料的储能模量增加、损耗因子减小,具有更好的阻尼性能和热稳定性。     

粉煤灰基纳米复合材料的制备及光催化分解水产氢性能研究

采用一种经济可行的方法制备粉煤灰基CdS／Al-MCM-41介孔纳米复合材料,通过碱融法从粉煤灰中提取硅源和铝源,室温下模板组装纳米复合材料,小角XRD和高分辨率TEM结果表明,介孔分子筛Al-MCM-41的平均孔径约3．0nm,CdS颗粒均匀地分散于Al-MCM-41的孔道内;UV—vis漫反射光谱结果表明,CdS／Al-MCM-41纳米复合材料在波长约521nm处出现较强吸收边;荧光光谱结果表明,CdS与Al-MCM-41复合有效地降低了光生电子与空穴的复合几率;在可见光照射下,CdS／Al-MCM-41显示出较高的产H2活性,归因于CdS颗粒和介孔分子筛Al-MCM-41之间的协同作用所致。     

复合材料CdS/Al-HMS的制备及可见光催化降解污染物制氢活性研究

采用模板法、离子交换法、沉淀法和浸渍法等多步反应合成了系列CdS/Al-HMS和负载的Pt/CdS/Al-HMS光催化复合材料; 利用XRD、TEM、XRF及UV-Vis漫反射光谱等分析技术对其进行了表征; 研究结果表明: CdS的复合量是影响CdS/Al-HMS复合材料结构的主要因素.当CdS复合量较低时,形成掺杂复合材料; 当CdS复合量较高时,形成纳米复合材料. 载6%Pt后的CdS/Al-HMS光催化复合材料降解甲酸的最高产氢速率为22.3mL/h, 420nm处的表观量子产率为12%.     

A Simple Route to Reduced Graphene Oxide‐Draped Nanocomposites with Markedly Enhanced Visible‐Light Photocatalytic Performance

Nanocomposites (denoted RGO/ZnONRA) comprising reduced graphene oxide (RGO) draped over the surface of zinc oxide nanorod array (ZnONRA) were produced via a simple low‐temperature route, dispensing with the need for hydrothermal growth, electrochemical deposition or other complex treatments. The amount of deposited RGO can be readily tuned by controlling the concentration of graphene oxide (GO). Interestingly, the addition of Sn²⁺ not only enables the reduction of GO, but also functions as a bridge that connects the resulting RGO and ZnONRA. Remarkably, the incorporation of RGO improves the visible‐light absorption and reduces the bandgap of ZnO, thereby leading to the markedly improved visible‐light photocatalytic performance. Moreover, RGO/ZnONRA nanocomposites exhibit a superior stability as a result of the surface protection of ZnONRA by RGO. The mechanism on the improved photocatalytic performance based on the cophotosensitizations under the visible‐light irradiation has been proposed. This simple yet effective route to the RGO‐decorated semiconductor nanocomposites renders the better visible‐light utilization, which may offer great potential for use in photocatalytic degradation of organic pollutants, solar cells, and optoelectronic materials and devices.     

A Universal Synthesis Strategy for Lanthanide Sulfide Nanocrystals with Efficient Photocatalytic Hydrogen Production

As an important lanthanide (Ln)-based functional materials, the Ln chalcogenides possess unique properties and various applications. However, the controllable synthesis of Ln chalcogenide nanocrystals still faces great challenges because of the rather poor affinity between Ln and chalcogenide ions (S, Se, Te) as well as strong preference of combination with existed oxygen. Herein, a facile but general heterogeneous nucleation synthetic strategy is established toward a series of colloidal ternary Cu Ln sulfides nanocrystals using the Ln dithiocarbamates and CuI as precursors. To extend this synthetic protocol, similar strategy is used to prepare six kinds of high quality CuLnS₂ nanocrystals, while the bulk ones are only obtained by the traditional solid-state reaction at rigorous condition. Importantly, high-entropy nanocrystals CuLnS₂ and CuEu_xLn_2-xS₃ which contain six Ln elements (Nd, Sm, Gd, Tb, Dy) are readily obtained by the co-decomposed process attributed to their similar diffusion speed. As a proof-of-concept application, CuEu₂S₃ nanocrystals showed efficient photocatalytic hydrogen production properties.     

Synthesis of Manganese Ferrite/Graphene Oxide Nanocomposites for Biomedical Applications

In this study, MnFe₂O₄ nanoparticle (MFNP)‐decorated graphene oxide nanocomposites (MGONCs) are prepared through a simple mini‐emulsion and solvent evaporation process. It is demonstrated that the loading of magnetic nanocrystals can be tuned by varying the ratio of graphene oxide/magnetic nanoparticles. On top of that, the hydrodynamic size range of the obtained nanocomposites can be optimized by varying the sonication time during the emulsion process. By fine‐tuning the sonication time, MGONCs as small as 56.8 ± 1.1 nm, 55.0 ± 0.6 nm and 56.2 ± 0.4 nm loaded with 6 nm, 11 nm, and 14 nm MFNPs, respectively, are successfully fabricated. In order to improve the colloidal stability of MGONCs in physiological solutions (e.g., phosphate buffered saline or PBS solution), MGONCs are further conjugated with polyethylene glycol (PEG). Heating by exposing MGONCs samples to an alternating magnetic field (AMF) show that the obtained nanocomposites are efficient hyperthermia agents. At concentrations as low as 0.1 mg Fe mL^?1 and under an 59.99 kA m^?1 field, the highest specific absorption rate (SAR) recorded is 1588.83 W g^?1 for MGONCs loaded with 14 nm MFNPs. It is also demonstrated that MGONCs are promising as magnetic resonance imaging (MRI) T₂ contrast agents. A T₂ relaxivity value (r₂) as high as 256.2 (mM Fe)^?1 s^?1 could be achieved with MGONCs loaded with 14 nm MFNPs. The cytotoxicity results show that PEGylated MGONCs exhibit an excellent biocompatibility that is suitable for biomedical applications.     

Photocatalytic Reduction of Graphene Oxide–TiO2 Nanocomposites for Improving Resistive‐Switching Memory Behaviors

Graphene oxide (GO)‐based resistive‐switching (RS) memories offer the promise of low‐temperature solution‐processability and high mechanical flexibility, making them ideally suited for future flexible electronic devices. The RS of GO can be recognized as electric‐field‐induced connection/disconnection of nanoscale reduced graphene oxide (RGO) conducting filaments (CFs). Instead of operating an electrical FORMING process, which generally results in high randomness of RGO CFs due to current overshoot, a TiO₂‐assisted photocatalytic reduction method is used to generate RGO‐domains locally through controlling the UV irradiation time and TiO₂ concentration. The elimination of the FORMING process successfully suppresses the RGO overgrowth and improved RS memory characteristics are achieved in graphene oxide–TiO₂ (Go‐TiO₂) nanocomposites, including reduced SET voltage, improved switching variability, and increased switching speed. Furthermore, the room‐temperature process of this method is compatible with flexible plastic substrates and the memory cells exhibit excellent flexibility. Experimental results evidence that the combined advantages of reducing the oxygen‐migration barrier and enhancing the local‐electric‐field with RGO‐manipulation are responsible for the improved RS behaviors. These results offer valuable insight into the role of RGO‐domains in GO memory devices, and also, this mild photoreduction method can be extended to the development of carbon‐based flexible electronics.     

磁响应性TiO2/石墨烯纳米复合材料的合成及光催化性能

采用乳液插层水解法成功制备了一种层状磁响应性光催化纳米复合材料.首先通过水热法制备磁性Fe3O4纳米粒子,将其超声分散在溶有钛酸丁酯的无水乙醇中,形成钛酸丁酯包裹Fe3O4纳米粒子的微乳液,然后将该微乳液插层于石墨烯中,利用石墨烯的层状结构作为载体形成一种稳定体系,通过控制水解,使TiO2纳米粒子与磁性Fe3O4纳米粒子共同镶嵌于石墨烯层间,形成一种新型的磁响应TiO2/石墨烯纳米复合材料.通过扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、震动样品磁强计(VSM)等手段对该复合材料进行表征,并通过模拟太阳光下降解亚甲基蓝(MB)评价复合材料的光催化性能.该复合材料通过磁分离可反复使用,重复使用7次后,对亚甲基蓝的降解率仍大于90％.