Ag2S nanospheres were synthesized by a hydrothermal reaction using l-cysteine as the sulfur source and chelating reagent. The X-ray diffraction patterns and X-ray photoelectron spectra confirmed that the products were monoclinic α-Ag2S. The optical absorption spectra of the Ag2S nanospheres showed very broad absorption peaks centered at about 515 nm in wavelength. Photoluminescence spectra exhibited emission peaks centered at ∼637 nm in wavelength accompanied by weaker shoulder peaks at ∼590 nm in wavelength when the sample was excited with a wavelength of 490 nm. In addition, the formation mechanism of the Ag2S nanospheres was also determined. The l-cysteine-assisted hydrothermal route using l-cysteine as the sulfur source and chelating reagent provides an alternative approach to generate sulfide nanocrystals.
Shape-controlled crystallization and self-assembly of high-ordered CaCO3 architectures were realized by using soluble starch as structure directing agents in aqueous solution. Mushrooms, dumbbells, spheres, and truncated-octahedron CaCO3 crystals composed of spindly microcrystals were obtained by tuning the experimental parameters, such as the concentration of starch, pH value, and the concentration of Ca2+ cations. The phases, morphologies, and structures of the products were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, and infrared spectrophotometry. The surface properties of CaCO3 crystals were also successfully modified to be hydrophobic using n-dodecanethiol as a modifier. The contact angle changed from 23° to 137° and 148° after surface treatment. The hydrophobic properties of the resulting products may have potential applications as a filler in composite materials.
An L-cysteine-assisted self-assembly process for constructing complex PbS from cubes to star and dendritic structures via hydrothermal routes is reported. In this process, L-cysteine (Cys) was used as both a sulfur source and a chelating reagent. The effects of the molar ratios of Cys/Pb 2+ , the concentrations, reaction time and temperature on the self-assembly of PbS microcrystals were investigated. The X-ray diffraction (XRD) patterns confirmed the crystalline structure of PbS crystals. Raman spectroscopy helped to further demonstrate the purity of the products. Transmission electron microscopy (TEM) helped to determine the size and shape of the products. On the basis of systemic studies about the influence of experimental parameters on the products, possible evolution processes were proposed. The shape of PbS crystals was closely related to the relative growth rate of the {100} and {111} faces. The Cys/Pb 2+ molar ratios, the concentrations, and the reaction temperatures influenced the growth rate of the {100} and {111} faces, which determined the final morphology of PbS microcrystals.
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