基础实验:金纳米粒子的制备及其光学性质

围绕金纳米粒子前沿内容,设计了一个简易的本科生基础实验,利用柠檬酸钠还原氯金酸法制备分散性好的金纳米粒子溶液,讨论了其尺寸与颜色的关系,探究了不同电解质和非电解质对金纳米粒子团聚及其颜色的影响,初步了解金纳米粒子的光学特性和探针效应基本原理。     

Colloidal Synthesis and Optical Properties of All‐Inorganic Low‐Dimensional Cesium Copper Halide Nanocrystals

Low‐dimensional metal halides have recently attracted extensive attention owing to their unique structure and photoelectric properties. Herein, we report the colloidal synthesis of all‐inorganic low‐dimensional cesium copper halide nanocrystals (NCs) by adopting a hot‐injection approach. Using the same reactants and ligands, but different reaction temperatures, both 1D CsCu₂I₃ nanorods and 0D Cs₃Cu₂I₅ NCs can be prepared. Density functional theory indicates that the reduced dimensionality in 1D CsCu₂I₃ compared to 0D Cs₃Cu₂I₅ makes the excitons more localized, which accounts for the strong emission of 0D Cs₃Cu₂I₅ NCs. Subsequent optical characterization reveals that the highly luminescent, strongly Stokes‐shifted broadband emission of 0D Cs₃Cu₂I₅ NCs arises from the self‐trapped excitons. Our findings not only present a method to control the synthesis of low‐dimensional cesium copper halide nanocrystals but also highlight the potential of 0D Cs₃Cu₂I₅ NCs in optoelectronics.     

ZnxCd1-xS纳米线的可控合成及其可调的光学性质

采用简单的气相沉积法,合成了不同组成的Zn_xCd_1-xS (0< x <1)纳米线. 利用扫描电子显微镜、透射电子显微镜和电子能谱研究了所制得的纳米线的表面形貌和组成. 该方法以Au为催化剂,简单控制起始物质的相对用量和沉积温度,可以获得可控的Zn/Cd 比例. X射线衍射结果表明所制得的Zn_xCd_1-xS纳米线具有纤维锌矿的单晶结构. 根据制得纳米线的表面形貌讨论了纳米线可能的生长机理为“底部生长”机理. 利用拉曼光谱和光致发光光谱研究了Zn_xCd_1-xS纳米线的光学性质,其纵向光学(LO)声子的拉曼位移频率随着组成的变化在ZnS和CdS的拉曼位移频率之间连续变化. 光致发光光谱中同时存在带边发光和缺陷发光. Zn_xCd_1-xS纳米线的带间跃迁的频率可随着组成的调节而调节,纳米线的禁带宽度介于ZnS (3.63 eV)和CdS (2.41 eV)的禁带宽度之间.     

Self‐Sorting Double‐Network Hydrogels with Tunable Supramolecular Handedness and Mechanical Properties

Self‐sorting, simultaneous, and orthogonal operations during the self‐assembly of complex mixtures are commonly observed for biological species but rare in artificial systems. In this study, we designed two gelators (LPF and LPFEG) containing the same chiral phenylalanine core but different achiral peripheral substituents to give hydrogels with opposite supramolecular handedness. When the two hydrogels were mixed, double‐network nanofibers with opposite handedness were formed by spontaneous high‐order organization and self‐sorting of the two gelators. The chiroptical activity of the double‐network hydrogels could be tuned by varying the molar ratio of LPF and LPFEG in the mixture, thus showing that the two gelators were highly independent of each other. Enhanced mechanical properties were observed for the interpenetrating networks when the LPF/LPFEG molar ratio was 3:7, with a more than fourfold increase in both the storage (G′) and loss modulus (G′′) relative to those of the individual hydrogels.