Enhancement of photocatalytic by Mn3O4 spinel ferrite decorated graphene oxide nanocomposites

The hydrothermal process was used to prepare Mn3O4/x%GO nanocomposites (NC’s) having different ratios of the Mn3O4 nanoparticles (NP’s) on the surface of graphene oxide (GO) sheet. SEM image showed that the Mn3O4 NP’s were distributed over the surface of GO sheet. HRTEM images exhibited the lattice fringe arising from the (101) plane of the Mn3O4 NP’s having the interplanar d-spacing of 0.49 nm decorating on the surface of GO. The electronic absorption spectra of Mn3O4/x%GO NC’s also show broad bands from 250 to 550 nm. These bands arise from the d–d crystal field transitions of the tetrahedral Mn3+ species and indicate a distortion in the crystal structure. Photo-catalytic activity of spinel ferrite Mn3O4 NP’s by themselves was low but photo-catalytic activity is enhanced when the NP’s are decorating the GO sheet. Moreover, the Mn3O4/10%GO NC’s showed the best photo-catalytic activity. This result comes from the formation of Mn–O–C bond that confirm by FT-IR. This bond would facilitate the transfer of the photoelectrons from the surfaces of the NP’s to the GO sheets. PL emission which is in the violet–red luminescent region shows the creation of defects in the fabricated Mn3O4 NP’s nanostructures. These defects create the defect states to which electrons in the VB can be excited to when the CB. The best degradation efficiency was achieved by the Mn3O4 NP’s when they were used to decorate the GO sheets in the Mn3O4/10%GO NC’s solution. Highlights Lattice fringe of Mn3O4 with an interplanar d-spacing of 0.49 nm for (101) plane. Photocatalytic activity of spinel ferrite Mn3O4 nanoparticles by itself is low. Number of photoelectrons created depends on number of Mn3O4 on a given area of GO The bonding of the Mn3O4 to the GO sheet would be though a Mn–O–C junction. The degradation processes were accelerated by Mn3O4/10%GO nanocomposites Graphic abstract

Quantum Dots Based Materials for Water Treatment

Quantum dot is a new class of nanomaterials having size in nanometers (˂10 nm). This material has excellent photo-catalytic activity towards dyes and pollutants with great absorbance and photoluminescence properties. It shows shifting of peak in UV-FL data which indicates the excitation dependent emission spectra means tunable properties in different wavelength and this property makes it a wonderful probe for sensing application for different heavy metals, pollutants present in water. In this chapter the synthesis, properties, types, application of quantum dots and focus on the research that has been done in field of water treatment with possible future outcomes is discussed.

Boron Doped ZnO Nanostructures for Photo Degradation of Methylene Blue, Methyl Orange and Rhodamine B

The design of sensitive and efficient photo catalyst for the energy and environmental applications with minimum charge recombination rate and excellent photo conversion efficiency is a challenging task. Herein we have developed a nonmetal doping methodology into ZnO crystal using simple solvothermal approach. The boron (B) is induced into ZnO. The doping of B did not make any significant change on the morphology of ZnO nano rods as confirmed by scanning electron microscopy (SEM) without considerable change on periodic arrangement of nanostructures. The existence of B, Zn, and O is shown by energy dispersive spectroscopy (EDS). The X-ray diffraction (XRD) patterns are well matched to the hexagonal phase for both pristine ZnO and B-doped ZnO. The XRD has shown slight dislocation of 2theta degree. The UV-visible spectroscopy was used to measure the optical bandgap and photo catalytic activity for the degradation of organic dyes. The nonmetal doped ZnO has shown potential and outstanding photo catalytic activity for the photo degradation of methylene blue (MB), methyl orange (MO) and rhodamine B in aqueous solution. The photo degradation efficiency of MB, MO and rhodamine B is found to be 96%, 86% and 80% respectively. The enhanced photo catalytic activity of B-doped ZnO is indexed to the inhibited charge recombination rate due to the reduction in the optical bandgap. Based on the obtained results, it can be said that nonmetal doping is excellent provision for the design of active materials for the extended range of applications.

Influence of Ni2+ Ions on the Structural, Morphological, Photoluminescence, Photo-Catalytic and Anti-Bacterial Studies of Cd0.9Zn0.1S Nanostructures

Controlled synthesis of Cd0.9Zn0.1S and Cd0.89Zn0.1Ni0.01S nanostructures by chemical co-precipitation route was reported. The XRD analysis confirmed the cubic structure of CdS on Zn doping and Zn, Ni dual doping without any secondary/impurity phases and no alteration in cubic phase was noticed by Zn/Ni addition. The shrinkage of crystallite size from 69 Å to 43 Å and the variation in lattice constants and micro-strain were described by the addition of Ni and the defects associated with Ni2+ ions. The enhanced optical absorbance in the visible wavelength and the reduced energy gap by Ni substitution showed that Cd0.89Zn0.1Ni0.01S nanostructures are useful to improve the efficiency of opto-electronic devices. The functional groups of Cd-S / Zn-Cd-S /Zn/Ni-Cd-S and their chemical bonding were verified by Fourier transform infrared studies. The elevated visible PL emissions such as blue and green emissions by Ni addition was explained by worsening of crystallite size and generation of more defects. Zn, Ni dual doped CdS nanostructures are identified as the probable an efficient photo-catalyst for the degradation of methylene blue dye. The liberation of more charge carriers, better visible absorbance, improved surface to volume ratio and the creation of more defects are accountable for the current photo-catalytic activity in Zn/Ni doped CdS which exhibited better photo-catalytic activity after sex cycling process. The noticed higher bacterial killing ability at Ni doped Cd0.9Zn0.1S is due to the collective effect of lower particle/grain size and also higher ROS producing capacity.