M. Shahnawaze Ansari

Formation of Mn-Doped SnO2 Nanoparticles Via the Microwave Technique: Structural, Optical and Electrical Properties

Ultrafine pure and Mn-doped SnO2 nanoparticles (NPs) were synthesized via the microwave technique. They were produced using tin chloride and hexamethylenetetramine at the molar ratio of 1:20. The concentrations of Mn in the SnO2 matrix were in the range of 0.1–5 mol%. These nanomaterials were characterized using different techniques. SEM and TEM results show ultrafine NPs with sizes around 10 nm in both pure and Mn-doped samples. A single-phase rutile-type tetragonal structure was observed in pure and Mn-doped samples, as revealed by XRD analysis, while PL emission spectra of these samples showed the broad band peaking at 365 nm. The intensity of this band was observed to increase by increasing the concentration of Mn up to 0.3 mol%, and then to decrease at higher values. A Raman spectrum of the pure sample shows two bands at 630 and 780 cm−1, which are the regular A1g and B2g vibrations of SnO2, while an extra band is observed at 210 cm−1 in the doped samples. The resistivity of Mn-doped SnO2 NPs was observed to decrease by increasing the temperature, but it drastically increased by increasing the Mn content. The activation energy of Mn-doped SnO2 NPs was also calculated, and was found to increase from 0.53 to 1.21 eV by varying the Mn dopant from 0.1 to 5 mol%. These results show that the microwave technique is a powerful tool that can be used to produce a high yield of ultrafine SnO2 NPs. Moreover, Mn was found to be a proper activator for tuning the optical and electrical properties of this material, for its application as a dilute magnetic semiconductor or spintronic devices.

Data Fitting to Study Ablated Hard Dental Tissues by Nanosecond Laser Irradiation.

Laser ablation of dental hard tissues is one of the most important laser applications in dentistry. Many works have reported the interaction of laser radiations with tooth material to optimize laser parameters such as wavelength, energy density, etc. This work has focused on determining the relationship between energy density and ablation thresholds using pulsed, 5 nanosecond, neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12 (Nd:YAG) laser at 1064 nanometer. For enamel and dentin tissues, the ablations have been performed using laser-induced breakdown spectroscopy (LIBS) technique. The ablation thresholds and relationship between energy densities and peak areas of calcium lines, which appeared in LIBS, were determined using data fitting. Furthermore, the morphological changes were studied using Scanning Electron Microscope (SEM). Moreover, the chemical stability of the tooth material after ablation has been studied using Energy-Dispersive X-Ray Spectroscopy (EDX). The differences between carbon atomic % of non-irradiated and irradiated samples were tested using statistical t-test. Results revealed that the best fitting between energy densities and peak areas of calcium lines were exponential and linear for enamel and dentin, respectively. In addition, the ablation threshold of Nd:YAG lasers in enamel was higher than that of dentin. The morphology of the surrounded ablated region of enamel showed thermal damages. For enamel, the EDX quantitative analysis showed that the atomic % of carbon increased significantly when laser energy density increased.

Structural and dielectric properties of Ni-Cu-Mg nanoferrites

Nanoscale Ni0.7-xCu0.3MgxFe2O4 (0.0 ≤ × ≤ 0.5) powders were prepared by sol-gel synthesis with M= Ni, Cu, Mg. they are obtained as dried gel after the successful reaction of their respective metal nitrates. X-ray diffraction method confirmed the successful synthesis of the materials. The average particle size of these materials has been found between 19-26 nm. Dielectric constant (e) decreases with increase in frequency which is rapid at lower frequencies and slower at higher frequencies which may be due to Maxwell-Wagner interfacial polarization. Dielectric relaxation peaks were observed in the lower concentration for frequency dependence of dielectric loss tangent curves.