Crystalline nanostructures possess defects/vacancies that affect their physical and chemical properties. In this regard, the electronic structure of materials can be effectively regulated through defect engineering; t...Crystalline nanostructures possess defects/vacancies that affect their physical and chemical properties. In this regard, the electronic structure of materials can be effectively regulated through defect engineering; therefore, the correlation between defects/vacancies and the properties of a material has attracted extensive attention. Here, we report the synthesis of Bi2S3 microspheres by nanorod assemblies with exposed {211} facets, and the investigation of the types and concentrations of defects/vacancies by means of positron annihilation spectrometry. Our studies revealed that an increase in the calcined temperature, from 350 to 400 ℃, led the predominant defect/vacancy densities to change from isolated bismuth vacancies （VBi） to septuple Bi3＋-sulfur vacancy associates （VBiBiBiSSSS）. Furthermore, the concentration of septuple BiB＋-sulfur vacancy associates increased as the calcined temperature was increased from 400 to 450 ℃. The characterized transient photocurrent spectrum demonstrates that the photocurrent values closely correlate with the types and concentrations of the predominant defects/vacancies. Our theoretical computation, through first principles, showed that VBiBiBiSSSS strongly absorbs I2（sol）, easily desorbs I-（sol）, and enhances the electrocatalytic activity of the nanostructures.展开更多
The presence of defects/vacancies in nanomaterials influences the electronic structure of materials, and thus, it is necessary to study the correlation between the optoelectronic properties of a nanomaterial and its d...The presence of defects/vacancies in nanomaterials influences the electronic structure of materials, and thus, it is necessary to study the correlation between the optoelectronic properties of a nanomaterial and its defects/vacancies. Herein, we report a facile solvothermal route to synthesize three-dimensional （3D） SnS nanostructures formed by {131} faceted nanosheet assembly. The 3D SnS nanostructures were calcined at temperatures of 350, 400, and 450 ~C and used as counter electrodes, before their photocurrent properties were investigated. First principle computation revealed the photocurrent properties depend on the defect/vacancy concentration within the samples. It is very interesting that characterization with positron annihilation spectrometry confirmed that the density of defects/vacancies increased with the calcination temperature, and a maximum photocurrent was realized after treatment at 400 ℃. Further, the defect/vacancy density decreased when the calcination temperature reached 450℃ as the higher calcination temperature enlarged the mesopores and densified the pore walls, which led to a lower photocurrent value at 450℃ than at 400℃.展开更多
文摘Crystalline nanostructures possess defects/vacancies that affect their physical and chemical properties. In this regard, the electronic structure of materials can be effectively regulated through defect engineering; therefore, the correlation between defects/vacancies and the properties of a material has attracted extensive attention. Here, we report the synthesis of Bi2S3 microspheres by nanorod assemblies with exposed {211} facets, and the investigation of the types and concentrations of defects/vacancies by means of positron annihilation spectrometry. Our studies revealed that an increase in the calcined temperature, from 350 to 400 ℃, led the predominant defect/vacancy densities to change from isolated bismuth vacancies （VBi） to septuple Bi3＋-sulfur vacancy associates （VBiBiBiSSSS）. Furthermore, the concentration of septuple BiB＋-sulfur vacancy associates increased as the calcined temperature was increased from 400 to 450 ℃. The characterized transient photocurrent spectrum demonstrates that the photocurrent values closely correlate with the types and concentrations of the predominant defects/vacancies. Our theoretical computation, through first principles, showed that VBiBiBiSSSS strongly absorbs I2（sol）, easily desorbs I-（sol）, and enhances the electrocatalytic activity of the nanostructures.
文摘The presence of defects/vacancies in nanomaterials influences the electronic structure of materials, and thus, it is necessary to study the correlation between the optoelectronic properties of a nanomaterial and its defects/vacancies. Herein, we report a facile solvothermal route to synthesize three-dimensional （3D） SnS nanostructures formed by {131} faceted nanosheet assembly. The 3D SnS nanostructures were calcined at temperatures of 350, 400, and 450 ~C and used as counter electrodes, before their photocurrent properties were investigated. First principle computation revealed the photocurrent properties depend on the defect/vacancy concentration within the samples. It is very interesting that characterization with positron annihilation spectrometry confirmed that the density of defects/vacancies increased with the calcination temperature, and a maximum photocurrent was realized after treatment at 400 ℃. Further, the defect/vacancy density decreased when the calcination temperature reached 450℃ as the higher calcination temperature enlarged the mesopores and densified the pore walls, which led to a lower photocurrent value at 450℃ than at 400℃.
