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Direct Observation of Curved Surface Enhanced Disordering in Ag <sub/>2</sub> S Nanoparticles
摘要： Surface induced order-disorder phase transition has been widely studied on flat bulk surfaces, while such a transition is poorly understood on curved surfaces in nanoscale. Here, we report a direct observation of the dynamic behaviors of surface-initiated disordering in Ag2S nanoparticles using atomic resolution in-situ transmission electron microscopy. It was found that the disordering behavior is different from the traditional model that the disordered layer follows a logarithmical thickness dependence with temperature. In particular, the disordering is largely enhanced at higher temperature when the radius of the residual order phase is getting smaller. Moreover, the correlation length of disordered phase was found to be several times larger than the typical value for bulk surfaces. This significantly enhanced disordering in nanoparticles could be attributed to the extra driving force provided by the decreasing of order-disorder interface area.
关键词： nanoscale,Ag2S nanoparticles,in-situ TEM,phase transition,surface-initiated disordering
更新于2025-09-04 15:30:14
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Fabrication and characterization of pure and modified Co3O4 nanocatalyst and their application for photocatalytic degradation of eosine blue dye: a comparative study
摘要： The present work deals with the synthesis of cobalt oxide, and Fe2+- and Ni2+-doped cobalt oxide nanoparticles as a catalyst. The study is investigating the different factors in obtaining cobalt oxide, and Fe2+- and Ni2+-doped cobalt oxide nanoparticles. Photocatalytic degradation studies are carried out for water-soluble eosine blue (EB) dye using cobalt oxide, and Fe2+- and Ni2+-doped cobalt oxide nanoparticles in aqueous solution. Different parameters such as initial dye concentration, dose of catalyst, contact time and pH have been studied to optimize reaction conditions. It is observed that photocatalytic degradation is a more effective and faster mode of removing EB dye by cobalt oxide, and Fe2+- and Ni2+-doped cobalt oxide nanoparticles than work done before. The optimum conditions for the removal of the EB dye are initial concentration 40 mg/L, photocatalyst dose 0.8 g/L, and pH 7.5. The EDS technique gives the elemental composition of synthesised cobalt oxide, and Fe2+- and Ni2+-doped cobalt oxide nanoparticles. The TEM and XRD studies are carried for morphological feature characteristics of synthesized cobalt oxide, and Fe2+- and Ni2+-doped cobalt oxide nanoparticles. Pseudo-first-order kinetic has been investigated for both pure and doped cobalt oxide catalysts. Almost 95% dye degradation has been observed for doped cobalt oxide nanoparticles.
关键词： Photocatalytic degradation,Modified cobalt oxide nanoparticles,Eosine blue,EDS,SEM,XRD,TEM
更新于2025-09-04 15:30:14
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In situ TEM Study of the Degradation of PbSe Nanocrystals in Air
摘要： PbSe nanocrystals have attracted widespread attention due to a variety of potential applications. However, the practical utility of these nanocrystals has been hindered by their poor air stability, which induces undesired changes in the optical and electronic properties. An understanding of the degradation of PbSe nanocrystals when they are exposed to air is critical for improving the stability and enhancing their applications. Here, we use in situ transmission electron microscopy (TEM) with an environmental cell connected to air to study PbSe nanocrystal degradation triggered by air exposure. We have also conducted a series of complementary studies, including in situ environmental TEM study of PbSe nanocrystals exposed to pure oxygen, PbSe nanocrystals in H2O using a liquid cell, ex situ experiments, such as O2 plasma treatment and thermal heating of PbSe nanocrystals under different air exposure. Our in situ observations reveal that when PbSe nanocrystals are exposed to air (or oxygen) under electron beam irradiation, they experience a series of changes, including shape evolution of individual nanocrystals with the cuboid intermediates, coalescence between nanocrystals, and formation of PbSe thin films through drastic solid‐state fusion. Further studies show that the PbSe thin films transform into an amorphous Pb rich phase or eventually pure Pb, which suggest that Se reacts with oxygen and can be evaporated under electron beam illumination. These various in situ and ex situ experimental results indicate that PbSe nanocrystal degradation in air is initiated by the dissociation and removal of ligands from the PbSe nanocrystal surface.
关键词： in situ TEM,air stability,ligand removal,degradation,PbSe nanocrystals,oxygen exposure
更新于2025-09-04 15:30:14