Manjeet S. Dahiya

EPR and impedance spectroscopic investigations on lithium bismuth borate glasses containing nickel and vanadium ions.

Glasses having composition 7NiO∙23Li2O∙20Bi2O3∙50B2O3, 7V2O5∙23Li2O∙20Bi2O3∙50B2O3 and x(2NiO∙V2O5)∙(30-x)Li2O∙50B2O3∙20Bi2O3 (with x=0, 2, 5, 7 & 10 mol%) prepared through melt-quench route are explored by analyzing density, impedance spectroscopy and electron paramagnetic resonance (EPR). It is found that both density and molar volume increase with an increase in substitution of 2NiO∙V2O5 in the base glass matrix. Different dielectric parameters viz. dielectric loss (ε), electrical modulus (M), loss tangent (tanδ) etc. are evaluated and their variations with frequency and temperature are analyzed which reveals that these glasses exhibit a non-Debye relaxation behavior. A phenomenal description of the capacitive behavior is obtained by considering the circuitry as a parallel combination of bulk resistance (Rb) and constant phase element (CPE). The conduction mechanism is found to follow Quantum Mechanical Tunneling (QMT) model. Spin Hamiltonian Parameters (SHPs) and covalency rates are calculated from the EPR spectra of vanadyl ion. The observed EPR spectra confirmed that V(4+) ion exists as vanadyl ion in the octahedral coordination with tetragonal compression.

An excellent humidity sensor based on In–SnO2 loaded mesoporous graphitic carbon nitride

A highly sensitive and fast responsive relative humidity (% RH) sensor based on In–SnO2 loaded cubic mesoporous graphitic carbon nitride (g-C3N4) has been demonstrated in this study. The mesoporous In–SnO2/meso-CN nanohybrid was synthesized through template inversion of mesoporous silica, KIT-6, using a nanocasting process. Due to its 3D replicated cubic structure with ordered mesopores, the nanohybrid facilitates the process of adsorption, charge transmission and desorption of water molecules across the sensor surfaces. Consequently, the optimized In–SnO2/meso-CN nanohybrid exhibits excellent response (5 orders change in impedance) in the 11–98% RH range, high stability, negligible hysteresis (0.7%) and superior real time % RH detection performance. Compared to traditional metal oxide based resistive sensors with unique mesoporous/hierarchical/sheet-like morphology, the 3D mesostructured In–SnO2/meso-CN nanohybrid demonstrated a superfast response (3.5 s) and recovery (1.5 s) in the 11–98% RH range at room temperature. These results open the door for breath monitoring and show a promising glimpse for designing mesoporous 2D layered materials in the development of future ultra-sensitive % RH sensors.

Optical and thermal investigations on vanadyl doped zinc lithium borate glasses

Abstract Using standard melt-quench technique, transition metal oxide (2 mol% of V2O5) doped glasses having composition xZnO·(30 − x)Li2O·70B2O3 (x = 0, 2, 5, 7 and 10) are prepared. The density (D) is measured using buoyancy and found to be lying between 2.21 and 2.45 g/cm3 with an increasing trend on substituting ZnO contents in place of Li2O. The theoretical optical basicity (Λth) is calculated and found to increase with increasing inclusion of ZnO indicating an increase in the ionic character. The molar refraction (Rm), refractive index (nr) and molar polarizability (αm) are calculated and explained on the basis of structural changes. The optical absorption spectra have been used to evaluate the values of optical band gap (Eopt) and band tailing parameter (B). It is observed that Eopt decreases with the increasing contents of ZnO in base glass matrix. The decrease in Eopt is an evidence of enhancement in the number of non-bridging oxygen atoms (NBOs) thereby increasing the four-coordinated boron atoms. The as-quenched samples in bulk form are subjected to differential thermal analysis (DTA) to assess the glass transition temperature (Tg), which is 476 °C for pure lithium borate glass. The variations suggest that the structure is being modified by the substitution of ZnO.

Physical, thermal, structural and optical absorption studies of vanadyl doped magnesium oxy-chloride bismo-borate glasses

Abstract Oxy-chloride bismuth-borate glasses with composition xMgCl2·(30 − x)MgO·20Bi2O3·50B2O3 containing 2 mol% doping of V2O5 (x = 12, 15, 20, 25 and 30) are prepared by melt-quenching technique. The structural, thermal and optical behaviors are explained by analyzing the data obtained from density (D), molar volume (Vm), theoretical optical basicity (Λth), differential scanning calorimetry (DSC), FTIR and UV–vis results. A decrease in D and increase in Vm (except for sample MBV3 for which D is maximum) on increasing chloride content suggests the formation of non-bridging oxygen atoms. Maximum glass transition temperature (Tg) and crystallization temperature (Tx) have been observed for sample MBV3. The glass stability (S) and stability ratio (S/Tg) have been calculated from the values of Tg and Tx and both are having maximum values for sample MBV3. Study of the FTIR spectra in the mid-IR range reveals the presence of both triangular and tetrahedral coordinated boron. The optical studies through UV–vis spectral analysis show non-sharp edge. The optical band gap (Eg) is also maximum for sample MBV3

Effect of mixed transition metal ions on DC conductivity in lithium bismuth borate glasses

The DC conductivities of glasses having composition x(2NiO·V2O5)·(30-x)Li2O·20Bi2O3·50B2O3 (with x=0, 2, 5, 7 and 10, i.e. NVLBB glasses) and glass samples having composition 7NiO·23 Li2O·20Bi2O3·50B2O3 and 7V2O5·23Li2O·20Bi2O3·50B2O3 (NLBB and VLBB respectively) are investigated as a function of temperature. Conductivity for glasses containing higher percentage of lithium ions is predominantly ionic and in glasses containing higher percentage of transition metal (TM) ions is predominantly electronic. The observed increase in conductivity with x and peak-like behavior at x=7 in NVLBB glasses due to competitive transport of small polaron contributing to a significant structural change in NVLBB glasses. Variation of molar volume and density was also observed with x. In NVLBB glasses, as x increases density increases except a slight decrease at x=7. Also density increases in NLBB whereas in case of VLBB it decreases in comparison to NVLBB1 glass composition. Mott’s small polaron hopping (SPH) model has been ...

Appearance of small polaron hopping conduction in iron modified cobalt lithium bismuth borate glasses

Lithium bismuth borate glasses containing different amounts of cobalt and iron oxides having chemical composition xFe2O3•(20-x)CoO•30Li2O•10Bi2O3•40B2O3 (x = 0, 5, 10, 15 and 20 mol% abbreviated as CFLBB1-5 respectively) prepared via melt quench technique have been investigated for their dc electrical conductivity. The amorphous nature of prepared glasses has been confirmed through X-ray diffraction measurements. The dc electrical conductivity has been analyzed by applying Mott’s small polaron hopping model. Activation energies corresponding to lower and higher temperature region have been evaluated. The iron ion concentration (N), mean spacing between iron ions (R) and polaron radius (Rp) has been evaluated using the values of phonon radius (Rph) and Debye temperature (θD). The glass sample without iron (CFLBB1) shows ionic conductivity but the incorporation of iron in the glass matrix results in the appearance of electronic conductivity.

Structural study and DC conductivity of vanadyl doped zinc lithium borate glasses

Glasses with composition xZnO⋅(30 − x)⋅Li2O⋅70B2O3 containing 2 mol% of V2O5 (x = 0, 2, 5, 7 and 10) were prepared by standard melt-quench technique. The amorphous nature of the glass samples was confirmed by using x-ray diffraction. The structural changes in these glasses have been investigated by employing IR spectroscopy in the mid-IR range. The infrared spectroscopic analysis confirms the presence of both triangular and tetraheldral coordinated boron units and absence of boroxol ring. It also shows that metal-oxide vibrations are present which are due to the bonding of lithium and zinc ions with oxygen. The dc conductivity was measured in the temperature range 353-523 K. The dc conductivity results show that conductivity decreases and activation energy increases when Li2O is replaced by ZnO, keeping the concentration of B2O3 constant. Decrease in conductivity and increase in activation energy shows that addition of ZnO to the glass matrix shows a “blocking effect” on the overall mobility of alkali ion...

Nano crystalline Bi2(VO5) phases in lithium bismuth borate glasses containing mixed vanadium-nickel oxides

Glass composition 7V2O5·23Li2O·20Bi2O3·50B2O3 and x(2NiO·V2O5)·(30-x)Li2O·20Bi2O3·50B2O3, x=0, 2, 5, 7 and 10, were produced by conventional melt quenching technique. The quenched amorphous glass samples were annealed at temperatures 400°C and 500°C for 6 hours. The Bi2(VO5) crystallite were grown in all prepared glass matrix. Tn vanadium lithium bismuth borate glass (annealed), the some phrase of V2O5-crystal were observed along with the nano crystalline Bi2(VO5) phase. The sharp peaks in FTTR spectra of all annealed compositions were also compatible with the XRD diffraction peaks of the system under investigation. Average crystalline size (D) of the Bi2(VO5) nano-crystallite was ~30nm for samples annealed at 400°C and ~42nm for samples annealed at 500°C. Lattice parameter and the lattice strain for all the samples was also calculated corresponding to the (113) plane of Bi2(VO5) crystallite.

Metal–ferrite nanocomposites for targeted drug delivery

Abstract Targeted drug delivery has emerged as an astonishing medication methodology for direct treatment of the infected body organ, and it avoids the side effects caused to other healthy organs of human body. Due to the ability to carry an adequate drug concentration and release it directly to the organ to be treated, nanocomposite materials have proven to be a boon for targeted drug delivery. The present chapter aims to discuss the role of metal–ferrite nanocomposites in achieving the targeted drug delivery. This will include the elaboration of different synthesis methodologies of metal–ferrite nanocomposites along with their compositional flexibility as the synthesis route has a strong impact on the structure of nanocomposites. The performance of these nanocomposites toward drug release, as analyzed by different scientists through in vitro studies, has been discussed. The reported literature has been integrated to understand the conceptual concreteness of drug release attributes such as drug-loading efficiency, biocompatibility, drug solubility, and so on, as well as the optimization criteria. Each category of nanocomposites including nanoparticles, 1D, 2D, and 3D nanostructures has been explored with their unique attributes toward their drug carrying and drug release performance. Moreover, the chapter deals with the current advancement in drug delivery systems based on magnetic ferrite nanocomposites and possible future perspectives through a critical discussion of the loopholes that exist in present methodologies.