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Effect of Phosphine-Free Selenium Precursor Reactivity on The Optical and Vibrational properties of Colloidal CdSe Nanocrystals
摘要： Phosphine-free selenium precursor solutions have been prepared by heating at temperatures ranging from 160 °C to 240 °C and studied by means of infrared absorption spectroscopy. The colloidal CdSe nanocrystals (NCs) synthesized from all those solutions by the wet chemical method. The influence of heating temperature on the chemical reactivity of selenium precursor and its role on the optical and vibrational properties of CdSe NCs are discussed in details. Their morphology, particle size, structural, optical and vibrational properties were investigated using transmission electron microscopy, X-ray diffraction, UV-Vis, fluorescence and Raman spectroscopy, respectively.
关键词： vibrational properties,Phosphine-free selenium precursor,CdSe nanocrystals,optical properties
更新于2025-09-04 15:30:14
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Ultrafast defect dynamics: A new approach to all optical broadband switching employing amorphous selenium thin films
摘要： Optical switches offer higher switching speeds than electronics, however, in most cases utilizing the interband transitions of the active medium for switching. As a result, the signal suffers heavy losses. In this article, we demonstrate a simple and yet efficient ultrafast broadband all-optical switching on ps timescale in the sub-bandgap region of the a-Se thin film, where the intrinsic absorption is very weak. The optical switching is attributed to short-lived transient defects that form localized states in the bandgap and possess a large electron-phonon coupling. We model these processes through first principles simulation that are in agreement with the experiments.
关键词： electron-phonon coupling,optical switches,interband transitions,all optical broadband switching,first principles simulation,amorphous selenium thin films,ultrafast defect dynamics,sub-bandgap region,transient defects
更新于2025-09-04 15:30:14
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A Facile Green Approach for Synthesis of Selenium Nanowires with Visible Light Photocatalytic Properties
摘要： In this work, high purity trigonal selenium (t-Se) nanowires were synthesized through a simple one-step solvothermal process at 50 °C. Sodium formaldehyde sulfoxylate (SFS) was used as a reducing agent. To our knowledge, this is the first time that SFS was used as the reducing agent for synthesis of Se nanostructures. In this method, Se nanowires were obtained at lower temperature, shorter period of reaction time and without using complex equipment. The experimental parameters, such as reaction duration, temperature and amount of surfactant, were investigated. The as-prepared Se nanowires have a diameter of about 100–200 nm and length of up to 10 μm. A “Solid–Solution–Solid” growth mechanism was proposed. In the presence of H2O2, the Se nanowires showed good catalytic performance, where over 99% of methylene blue (MB) was degraded in 3.0 h. Results from this study demonstrated that the Se nanowires exhibit a promising application for photodegradation.
关键词： Synthesis,Photocatalytic Performance,Selenium,Nanowires
更新于2025-09-04 15:30:14
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<i>In My Element</i> : Selenium
摘要： Selenium-rich foods are very popular in southern China, such as Se-rich oranges, tea, rice and mushrooms. As southern China has Se-rich soils, Se can be bioconcentrated by orange and tea trees or by rice and mushrooms growing in these soils. It holds true with many other plants grown in these Se-rich soils, and their fruits are believed to be Se-rich too. Eating Se-rich food every day is considered beneficial to our health because of its antioxidant effect.
关键词： redox-responsive,diselenide,dynamic covalent bonds,drug delivery,micronutrient,Selenium,Keshan disease,dendrimer,antioxidant,glutathione peroxidase
更新于2025-09-04 15:30:14
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Effect of excess electron on structure, bonding, and spectral properties of sulfur/selenium based dichalcogen systems
摘要： First principle based quantum chemical methods are employed to characterize structure, bonding, and spectral properties of sulfur and selenium based dichalcogen systems in presence of an excess electron. Inter molecular two-center three-electron (2c-3e) bonding between two chalcogen (X) atoms is described in the systems of the type (R-X)2?- (R = Ph, PhCH2 X = S, Se). In addition, effect of electron withdrawing (-NO2) and electron donating (-CH3) groups in phenyl ring on the stability of these 2c-3e bonded systems is also studied in water medium applying a macroscopic hydration model. Molecular parameters and binding energy of the neutral, (R-X)2 and reduced, (R-X)2?- dichalcogen systems are compared. Search for minimum energy structures of these open shell doublet systems are carried out applying various density functionals with dispersion corrections and MP2 method considering 6-311++G (d,p) set of basis functions for all atoms. Effect of water medium is introduced through a macroscopic solvation model based on density (SMD). Frontier molecular orbitals based analysis is carried out for showing the definite presence of 2c-3e bond between two chalcogen atoms in these radical anions of sulfur and selenium based aromatic dichalcogen systems. Excited state calculations are performed on all these systems using Time Dependent Density Functional Theory (TDDFT). UV-Vis spectra are simulated and effect of solvent water on the absorption maximum of these radical anions is discussed. This study illustrates that the combination of electronic effect and geometrical flexibility decides the strength of two-center three-electron bond in these systems.
关键词： sulfur,hemi bond,radical anion,density functional theory,chalcogen,excess electron,2c-3e bond,antioxidant,selenium
更新于2025-09-04 15:30:14