Showing papers by "Ajit Kumar Meikap published in 2022"

Study of Microstructural and Electrical Properties of Silver Substituted Hydroxyapatite for Drug Delivery Applications

Abstract: Silver doped hydroxyapatites (Ag-HAp) [Ca10−xAgx(PO4)6(OH)2;(0.0 ≤x ≤ 1.0)] were synthesized with pH = 10, by the in-situ hydrothermal method. Structural, microstructural, compositional, electrical and biocompatibility properties of Ag-Hap samples were studied to ascertain the suitability of the experimental samples in drug-delivery applications. The Rietveld refinement of the X-ray diffraction (XRD) pattern, analysis of Fourier transform infrared (FTIR) spectra, X-Ray photoelectron (XPS) spectra, and Energy Dispersive X-Ray (EDAX) spectra of the Ag-HAp samples had confirmed the successful doping of Ag atoms in the HAp lattice and simultaneous growth of secondary β-TCP phase with the detailed chemical phase compositions of appropriate percentages. The Field Emission Scanning Electron Microscopy (FESEM), EDAX, and Brunauer–Emmett–Teller (BET) characterizations were carried out to study their morphological, compositional, surface, and porous behavior. The cytocompatibility of the laboratory-synthesized biomaterials with sensitive human embryonic kidney cells (HEK293) by in-vitro MTT assay testing revealed that the Ag-HAp powders had no toxic effect on living body-cells up to the safe limit of usage (≤15 μg/mL). The relative cell-viability percentage (%rcv) was evaluated to be 95–106% for highly doped samples. The incorporation of monovalent Ag ions within HAp lattice influenced the thermal hopping of the charge carriers and resulted in significantly high ionic conductivity with very low activation energy for higher temperatures. The significantly high dielectric permittivity for elevated temperatures (613 K) of the Ag-HAp compared to that of pure-HAp, and the considerable amount of interfacial polarization occurring within highly-conductive grain (~10−5Sm−1) and resistive grain-boundary as established by complex impedance study gave rise to the probability of occurrence of the quasi-permanent surface potential with promising specific surface area (~40 m2/g). The highly biocompatible Ag-HAp rods, with good dielectric and electrical properties, showed a huge possibility of the material being used as a nano-carrier for electric field-induced targeted drug delivery purposes in the future.

The role of bias voltage in charge carrier transport mechanism of organic semiconductor

Abstract: The energy density of flexible electronics can be improved by storing charge at high voltage through the charge carrier transport in the organic semiconductor. However, voltage fluctuation triggers irreversible carrier recombination and associated heat generation, which influence interfacial and dipolar polarisation and a variation of relaxation phenomenon by densification of the space charge carriers in the electronic materials. This study provides a fundamental understanding of voltage variation and corresponding thermal variation via electrical transport properties measurement of 0.1 wt% and 0.5 wt% of cobalt oxide (Co3O4) on PVA flexible mat (Designated as PC0.1 and PC0.5 films). Here, we consider various models from the literature to demonstrate the effect of bias voltage on the transport properties of the flexible metal oxide film. The ac conduction mechanism follows a sharp transition of the Jonhcher power law to the jump relaxation model (JRM) around the system's glass transition temperature (Tg). The effect of the glass transition temperature is extensive analysis through the temperature-dependent real part of the dielectric and resistivity study. After Tg electrical transport properties of these composite films modifies significantly, as the resistivity follows Bӓssler's Gaussian disorder model (298–343 K) and Arrhenius model (348–383 K) in two different temperature regions. Further, we highlight the current-voltage characteristic at different temperatures and observe three different conduction mechanisms as trap free limited conduction (TFL) (−5 V→−1 V), Ohmic (0 V→+1 V), and Poole-Frenkel (PF) (1 V→+5 V) during trapping and de-trapping of the carriers in trap states. This fundamental study identifies the bias voltage effect in long-cycling organic electronics and enables us to market the implementation of flexible electronics with high-performance efficiency.

Template-free growth of copper-doped hydroxyapatite nanowhiskers and their use as uric acid electrochemical sensor

Abstract: We have synthesized copper-doped hydroxyapatite (Cu HAp) bioceramic nanowhiskers (aspect ratio ˃ 85) by a surfactant-free hydrothermal route. The detailed structural and compositional characterizations confirm the existence of catalytic multivalent Cu1+/Cu2+ dopant ions and secondary β TCP phase. The dopant-induced oxygen vacancies promote active sites on the mesoporous surface (specific area ∼ 60.4 m2/g) for electrochemical applications. The electrochemical studies of the fabricated Cu HAp FTO revealed good response, sensitivity and stability towards uric acid (lowest stable detection limit ∼0.5 μM) in the lower and higher concentration regimes respectively. Thus, our fabricated Cu HAp shows surface-dependent electrochemical activities and non-enzymatic selective response to uric acid.