Scattering of light by ZnO nanorod arrays

The optical properties of ZnO nanorod (NR) arrays were investigated by optical total transmittance (TT) and diffuse reflectance (DR) spectroscopy in the visible region. The NRs were grown electrochemically in a three-electrode cell over a glass/fluorine-doped tin oxide (FTO) substrate. The mean length, radius, and density of NR samples were characterized by scanning electron microscopy. The results were correlated with the observed optical properties. Since light scattering for these NR arrays is highly dependent on their morphology, therefore, a model for light scattering based in the Mie theory for cylinders was implemented to understand the observed spectra. The mean scattering and extinction cross sections were calculated from the morphology of the samples. They were used to fit the DR spectra. From the fittings, the TT spectra of the samples could be calculated. A good agreement with the experimental results was obtained. This indicates that the implemented model represents well the observed scattering phenomena.

Manganese-Doped Zinc Oxide Nanostructures as Potential Scaffold for Photocatalytic and Fluorescence Sensing Applications

Herein, we report the photocatalytic and fluorescence sensing applications of manganese-doped zinc oxide nanostructures synthesized by a solution combustion technique, using zinc nitrate as an oxidizer and urea as a fuel. The synthesized Mn-doped ZnO nanostructures have been analyzed in terms of their surface morphology, phase composition, elemental analysis, and optical properties with the help of scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and UV-Visible (UV-Vis) spectroscopy. A careful observation of the SEM micrograph reveals that the synthesized material was porous and grown in very high density. Due to a well-defined porous structure, the Mn-doped ZnO nanostructures can be used for the detection of ciprofloxacin, which was found to exhibit a significantly low limit of detection (LOD) value i.e., 10.05 µM. The synthesized Mn-doped ZnO nanostructures have been further analyzed for interfering studies, which reveals that the synthesized sensor material possesses very good selectivity toward ciprofloxacin, as it detects selectively even in the presence of other molecules. The synthesized Mn-doped ZnO nanostructures have been further analyzed for the photodegradation of methyl orange (MO) dye. The experimental results reveal that Mn-doped ZnO behaves as an efficient photocatalyst. The 85% degradation of MO has been achieved in 75 min using 0.15 g of Mn-doped ZnO nanostructures. The observed results clearly confirmed that the synthesized Mn-dopedZnO nanostructures are a potential scaffold for the fabrication of sensitive and robust chemical sensors as well as an efficient photocatalyst.

Optical Properties of CdS and CdTe Sensitized ZnO Nanorods

Optical properties of ZnO-CdTe electrochemically prepared on a core-shell nanostructure (NS) were studied. Numerical simulations based on effective medium approximation give higher absorption than ZnO-CdS samples and a sensitive dependence on CdTe content. The absorption edges for deep black samples found by transmittance (T(λ)) and diffuse reflectance (Rdiff(λ)) measurements were at 1.33eV and 1.55eV, respectively. A split-off band edge was also found by Rdiff(λ) at ∼2.5eV. The red shift observed in T(λ), previously observed in ZnO-CdS, and may confirm the enhancement of sub-bandgap absorption due to the NS nature of samples.