Richa Bhargava

Differential Susceptibility of Escherichia coli Cells toward Transition Metal-Doped and Matrix-Embedded ZnO Nanoparticles

Dependence of the antibacterial behavior on ZnO (TM-doped and surface-modified) nanoparticles on Escherichia coli cells has been investigated. ZnO nanoparticles that differ in size, activator ion and in the microenvironment in which these nanoparticles are embedded were used. Comprehensive antibacterial studies of these ZnO nanoparticles owing to their size and surface defects are carried out against E. coli cells. These studies have been carried out both in Luria-Bertani medium and on solid agar medium in the presence and absence of light. The differences in antibacterial effect have been quantified in terms of minimum inhibitory concentration, minimum bactericidal concentration, colony forming unit counts, and qualitatively evaluated by growth curves and disk diffusion tests. The difference in antibacterial activities of the ZnO nanoparticles may be attributed to the enhanced or reduced oxygen vacancies and defect states and could be attributed to the increased or decreased surface defects.

Switching in structural, optical, and magnetic properties of self-assembled Co-doped ZnO: effect of Co-concentration

Here, we report on the self-assembled Co-doped ZnO nanoparticles synthesized by using sol–gel technique. It has been observed that when Co is introduced in the solution, nanoparticles arrange themselves into a particular pattern. This self-assembly of Zn1−xCoxO, were found to be consistent with the change in Co-doping concentration. Using electron microscopy these systems were studied to confirm the assembly formation with doping. Optical study of these assemblies suggests the decrease in direct band gap of these systems with the increase in doping concentration. In addition to it, the Urbach energy was found to be increased, indicating the redistribution of states in between conduction and valence band with doping. Magnetic measurement shows the introduction of paramagnetic behavior with Co-doping in this self-assembled Co-doped ZnO.