K. Kombaiah

Green synthesis of Ag nanoparticles using Tamarind fruit extract for the antibacterial studies

In the present study, first time we report the microwave-assisted green synthesis of silver nanoparticles (AgNPs) using Tamarindus indica natural fruit extract. The plant extract plays a dual role of reducing and capping agent for the synthesis of AgNPs. The formation of spherical shape AgNPs is confirmed by XRD, HR-SEM, and HR-TEM. The presence of face-centered cubic (FCC) silver is confirmed by XRD studies and the average crystallite size of AgNPs is calculated to be around 6-8nm. The average particle diameter is found to be around 10nm, which is identified from HR-TEM images. The purity of AgNPs is confirmed by EDX analysis. The presence of sigmoid curve in UV-Visible absorption spectra suggests that the reaction has complicated kinetic features. To investigate the functional groups of the extract and their involvement in the reduction of AgNO3 to form AgNPs, FT-IR studies are carried out. The redox peaks are observed in cyclic voltammetry in the potential range of -1.2 to +1.2V, due to the redox active components of the T. indica fruit extract. In photoluminescence spectroscopy, the excited and emission peaks were obtained at 432nm and 487nm, respectively. The as-prepared AgNPs showed good results towards antibacterial activities. Hence, the present approach is a facile, cost- effective, reproducible, eco-friendly, and green method.

Bioreduction potentials of dried root of Zingiber officinale for a simple green synthesis of silver nanoparticles: Antibacterial studies

Green synthesis of silver nanoparticles (Ag NPs) using an extract of dried Zingiber officinale (ginger) root as a reducing and capping agent in the presence of microwave irradiation was herein reported for the first time. The formation of symmetrical spheres is confirmed from the UV-Visible spectrum of Ag NPs. Fourier transform infra-red spectroscopy confirms the formation of the Ag NPs. X-ray diffraction analysis was utilized to calculate the crystallite size of Ag NPs and the value was found to be 10nm. High-resolution transmission electron microscopy and high-resolution scanning electron microscopy were used to investigate the morphology and size of the synthesized samples. The sphere like morphology is confirmed from the images. The purity and crystallinity of Ag NPs is confirmed by energy-dispersive X-Ray analysis and selected area electron diffraction respectively. The electrochemical behavior of the synthesized Ag NPs was assessed by cyclic voltammetry (CV) and shows the redox peaks in the potential range of -1.1 to +1.1V. Agar diffusion method is used to examine the antibacterial activity of Ag NPs. For this purpose, two gram positive and two gram negative bacteria were studied. This single step approach was found to be simple, short time, cost-effective, reproducible, and eco-friendly.

Effects of Ba doping on structural, morphological, optical, and photocatalytic properties of self-assembled ZnO nanospheres

A simple low-temperature co-precipitation method was employed to synthesize pure and Ba-doped self-assembled ZnO nanospheres. The presence of self-assembled nanosphere-like morphology, high crystallinity, uniform size distribution, and more defects were confirmed by X-ray diffraction, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. Photocatalytic degradation of 2,4,6-trichlorophenol, a potent endocrine-disrupting chemical in aqueous medium was investigated. The effects of Ba doping on the structure, morphology, absorption, emission, and photocatalytic activity of ZnO nanospheres were investigated systematically. Furthermore, the effects of different photocatalytic degradation reaction parameters were investigated. The resulting photocatalytic degradation activity of Ba-doped ZnO nanospheres shows superior efficiency compared to pure ZnO and commercial TiO2 (Degussa P-25).Graphical AbstractA simple co-precipitation method was developed to synthesize pure and Ba-doped ZnO self-assembled nanospheres. The prepared photocatalyst shows a novel morphology, high crystallinity, uniform size distribution, and more defects. Effect of Ba doping on the structural, optical and photocatalytic properties of ZnO nanospheres were investigated systematically.