Synthesis of CdSe and CdSe:Ga nanostructures for antibacterial application

In this paper, the preparation of CdSe and CdSe:Ga nanoparticles using two methods: thermal evaporation and pulse laser ablation has been reported. Their structural properties were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). As confirmed by the XRD curves, CdSe and CdSe:Ga nanoparticles exhibited polycrystalline and wurtzite hexagonal structures with orientation planes of (100), (101), (102), (110) and (112). Also, a homogeneous distribution of nano-rod, flower-like, cylindrical, hexagonal and both nano-rod and hexagonal shapes with different diameters was seen by FESEM images. The band gaps of CdSe and CdSe:Ga (without annealed and annealed at temperatures of 150 (6 h) and 500∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{\circ }$$\end{document}C (1 h)) were found to be 1.72, 1.7, 1.69 and 1.64 eV, respectively. The antibacterial activity could be increased by annealing CdSe:Ga nanoparticles at 150∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{\circ }$$\end{document}C for 6 h in Gram-positive bacteria (Bacillus subtilis), whereas it is decreased in Gram-negative bacteria (Enterobacter cloacae). Alternatively, annealing CdSe:Ga at 500∘\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{\circ }$$\end{document}C for 1 h led to an increase in the antibacterial activity in both Gram-positive and Gram-negative bacteria. It is concluded that the antibacterial activity is highly dependent on the type of bacteria, material, preparation conditions and the used methods.