Cobalt doped zinc oxide nanoparticles (NPs) and nanorods (NRs) were synthesized by a simple chemical method. An increase in the formation of nanorods with an increase in cobalt doping is found to occur from scanning electron microscopy and transmission electron microscopy studies. Powder X-ray diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction confirm the formation of a wurtzite crystal structure of ZnO. Shifting and broadening of the bands at 437 cm⁻¹ and 579 cm⁻¹ in the micro-Raman study of Co-doped ZnO nanostructures indicates the incorporation of Co in ZnO. Shifting of the absorption edge to lower wavelength and blue shift of the band gap is observed in UV-visible spectra of Co-doped ZnO samples. Field-dependent magnetization measurements exhibit diamagnetic behavior down to 2 K in the case of ZnO whereas Co-doped ZnO samples show coexistence of superparamagnetic and ferromagnetic behavior at room temperature and at 2 K. The observed ferromagnetism may have originated due to the exchange interaction between the localized d electrons in Co²⁺ atoms and free carriers generated due to Co-doping as well as due to cobalt clustering in the Co-doped samples.

We have carried out a detailed study of the morphological, structural, optical and magnetic properties of Cr doped TiO₂ nanocrystals with doping concentrations varying from 3 to 12 atomic weight%. The results obtained from transmission electron microscopy analysis, size–strain plots of all the Cr-doped samples and crystallite size estimation reveal the particle size of the prepared nanocrystals to be well below 10 nm, which is observed to exhibit a decreasing trend with an increase in the Cr dopant concentration. All the samples crystallize in the anatase tetragonal phase of TiO₂, which is confirmed from the Rietveld refinement of the X-ray diffraction patterns and the different modes present in the Raman spectra. The E_g(1) mode shows a clear red shift and broadening with increase in the Cr concentration, which indicates the replacement of Ti ions with Cr ions in the TiO₂ lattice. The possibility of the presence of different functional groups present is verified by Fourier transform infra-red spectroscopy. The presence of Cr³⁺ and Ti⁴⁺ is confirmed from the X-ray photoelectron spectroscopy (XPS) results suggesting the formation of oxygen vacancies to compensate for the charge neutrality. The XPS results validate the Cr³⁺ existence in the Cr:TiO₂ system and corroborate with a slight peak shift towards lower diffraction angle and further confirm the substitutional doping in the present case. Enhanced visible range optical absorption and a clear red shift associated with the absorption edge also suggest the incorporation of Cr³⁺ ions into the host system. The estimated band-gap of Cr-doped TiO₂ nanocrystals reveals a decreasing trend with increasing Cr concentration. The Urbach energy associated with all the Cr-doped samples signifies the presence of oxygen vacancy related defects in the present system, which is further verified using photoluminescence (PL) spectra, and the deconvolution of the PL spectra provides an insight into the oxygen vacancy defects associated with the system. Paramagnetic (PM) behaviour is observed with an increase in the PM moment, suggesting the increase in isolated Cr ions with increase in the Cr concentration, which is further explained using a bound magnetic polaron (BMP) model. Isolated BMP formation could be the reason for the observed PM behavior of the present system, where the trapping of 3d electrons associated with Cr³⁺ in the vacancy sites could ultimately lead to fewer overlapped BMPs, yielding a net PM moment. The present Cr:TiO₂ system could be modified with tailored optical and magnetic properties for functional applications such as magneto-optics and optoelectronic devices.

Focussing on the green synthesis of ZnO NPs using a novel Lepidagathis ananthapuramensis (LA) leaf template and its photocatalytic activity.

The present study investigates the influence of cobalt doping on the structural and magnetic properties of TiO₂ nanoparticles prepared by a simple wet chemical method.

The temperature variation of electrical resistivity $\rho \left(T\right)$ and Seebeck coefficient $S\left(T\right)$ of Heusler-type ${\text{Fe}}_2{\text{VAl}}_{1-x}{\text{B}}_x$ $\left(0\le x\le 1\right)$ alloys have been investigated. All the studied alloys were crystallized into a single-phase cubic structure with $Fm3m$ space group. The $\rho \left(T\right)$ shows a negative temperature coefficient of resistivity (TCR) for the $x=0$ sample, which turns into a positive TCR for the $x=1$ sample; while intermediate compositions show a resistivity minimum at low temperatures $\left(T_{\text{min}}\right)$ below 50 K. From the analysis of temperature dependence of the electrical resistivity data, we demonstrate a semiconductorlike to metal transition on B substitution in the ${\text{Fe}}_2\text{VAl}$ alloy. With a minute substitution of isoelements (B and In) and nonisoelement (Si), $S$ changes drastically in its sign and magnitude accompanied by an appearance of a broad maximum at higher temperatures, which shifts toward high temperatures with increasing concentration of the substituents. These features are indicative of a dramatic modification in the band structures of the ${\text{Fe}}_2\text{VAl}$ alloy with the substitution of elements. Although similar changes in $\rho$ and $S$ values with compositions of B-, In-, and Si-substituted ${\text{Fe}}_2\text{VAl}$ alloys are observed, the $\rho$ decreases rapidly on B substitution and ultimately attains a metallic behavior, suggesting a true semiconductorlike to metal transition. The strong composition dependence of $S$ and $\rho$ on elemental substitution is attributed to the size, relative positions of the atomic levels and the number of valence electrons of the substituents.

Here, we explore the structural and optical properties of Ag-doped ZnO nanoparticles. We looked at the photocatalytic activity for degrading Methylene Blue and the antibacterial effectiveness against bacterial strains, including Gram-negative Escherichia coli and Gram-positive Bacillus subtilis.