The present work reports the development of super-hydrophobic and optically opaque monolith silic... more The present work reports the development of super-hydrophobic and optically opaque monolith silica aerogel that float in water. The opaque silica aerogels were prepared by the two step sol-gel process using tetraethoxysilane (TEOS) as silica precursor followed by cost effective ambient pressure drying with various aging solutions. The surface texture and microstructural properties of various silica aerogels are studied by the nitrogen adsorptionand field emission scanning electron microscopy (FESEM) techniques, respectively. The elemental analysis was carried out by energy dispersive X-ray (EDX) spectroscopy. The Fourier transform infrared (FT-IR) spectroscopy was utilized to investigate the genesis of the hydrophobic property. The X-ray photoelectron spectroscopy (XPS) technique was used to understand the prevalent oxidation state at the surface of the silica aerogel. The water contact angle (WCA) of silica aerogel was evaluated by the WCA measurement technique. The silica aerogel ...
Abstract Nano-scale load (P) dependency of fracture toughness (K1C) of indium tin oxide (ITO) coa... more Abstract Nano-scale load (P) dependency of fracture toughness (K1C) of indium tin oxide (ITO) coating on silicon (Si) substrate is evaluated by nanoindentation based direct and energy methods. A Berkovich triangular diamond nanoindenter is used with nine different P values e.g., 10, 15, 20, 30, 40, 50, 100, 150 and 200 mN. Extensive utilization of both optical microscopy (OM) and field emission scanning electron microscopy (FESEM) techniques reveal that up to P ≤ 40 mN only the sharp radial cracks form from three corners of the nanoindent. However, for P > 40 mN, multiple cracks occur over and above the radial cracks. Finally, at P: 150–200 mN coating gets chipped off from the substrate. The K1C values of the ITO coating are calculated on the basis of both the conventional radial crack length measurement based method and the strain energy release based method. The K1C values are strongly sensitive to variations in P. Further, the strain energy method results in higher magnitudes of the K1C values.
Journal of the mechanical behavior of biomedical materials, 2018
Here we report for the very first time the synthesis of 100% phase pure calcium silicate nanopart... more Here we report for the very first time the synthesis of 100% phase pure calcium silicate nanoparticles (CSNPs) of the α-wollastonite phase without using any surfactant or peptizer at the lowest ever reported calcination temperature of 850 °C. Further, the phase purity is confirmed by quantitative phase analysis. The nano-network like microstructure of the CSNPs is characterized by FTIR, Raman, XRD, FESEM, TEM, TGA, DSC etc. techniques to derive the structure property correlations. The performance efficacies of the CSNPs against gram-positive e.g., S. pyogenes and S. aureus (NCIM2127) and gram-negative e.g., E. coli (NCIM2065) bacterial strains are studied. The biocompatibility of the CSNPs is established by using the conventional mouse embryonic osteoblast cell line (MC3T3). In addition, the biofilm inhibition efficacies of two varieties of CSNPs e.g., CSNPs(W) and CSNPs(WC) are investigated. Further, the interconnection between ROS e.g., superoxide (O) and hydroxyl radical (OH) gen...
The mesoporous silica materials find important applications in stimuli responsive drug delivery d... more The mesoporous silica materials find important applications in stimuli responsive drug delivery devices as biocompatible due to high surface area, large pore volume and tunable pore diameter. The large surface area of the mesoporous silica and its biocompatibility are the two major factors beyond its vast in vivo and in vitro applications. The present study considers three different types of commercially available silica namely, glass silica, nano silica and mesoporous silica (that already contained ordered pores) for the investigation of structural aspects responsible for formation of pores within the nano particles. The purpose of the work was to study the formation mechanism of the pores in mesoporous silica. It was observed that crystallite sizes and lattice strain are the two important structural parameters responsible for the formation of pores within the nano silica. Results reveal that the mesoporous silica has the critical crystallite size and the nano particles are under highly strained condition compared to the other silica samples. So this high lattice strain and crystallite size may be the key factors for the formation of pores within the nanoparticles under certain condition.
Highly crystalline titanium dioxide (TiO2) and gold nanoparticle (Au NP) incorporated TiO2 films ... more Highly crystalline titanium dioxide (TiO2) and gold nanoparticle (Au NP) incorporated TiO2 films (with varying Au NP concentration), prepared by sol-gel route have been compared as regards their optical absorption spectra. Results indicated an increase in absorbance as well as systematic shift of the absorption edge towards the visible region, with increase in Au NP concentration, upto a critical concentration, beyond which a decrease in absorbance was observed. The optical band gap, calculated from the UV-Vis spectra, shows significant decrease ( eV) with respect to pristine TiO2, for this critical concentration (10% Au NP in TiO2 by volume), above which the decrease () was found to be less. The morphology of the composite film at this critical concentration revealed a homogeneous microstructure comprising particles of ~50 nm. The optimum band gap decrease was found to be associated with a structural change from rutile for the pristine to anatase-rutile mixed phase for the composite film. X-ray diffraction and transmission electron microscopy results indicated a reasonably good match of the lattice spacing for the optimum film. Preliminary current–voltage measurements indicated decrease in electrical resistivity of the optimum Au–TiO2 film, compared to that of its pristine counterpart.
In the present work V2O5 xerogel thin films are deposited on quartz substrate by using a cost eff... more In the present work V2O5 xerogel thin films are deposited on quartz substrate by using a cost effective sol–gel based dip coating method. Films of thickness ~122, 224 and 284 nm are grown as the number of dipping varies from one to three. Phase analyses of the thin films are investigated by X-ray diffraction technique. The microstructural characterization is carried out by electron microscopy techniques. Crystalline, phase pure V2O5 thin films with uniform nanoporous microstructure are grown in the present work. Solar transmittance and reflectance of films are measured by UV–VIS–NIR spectrophotometer. The optical band gap, refractive index and extinction coefficient of the films are also evaluated. Further, the average solar absorptance and IR emittance are evaluated by solar spectrum reflectometer and emissometer, respectively. The solar transmittance and optical band gap decrease with the increase in film thickness from 122 to 284 nm while reverse trend is observed for solar absorptance. Refractive index (~1.95) and IR emittance (~0.75) of the nanoporous V2O5 xerogel thin films on quartz substrate are almost independent of film thickness. The sheet resistance value slightly decreases from ~1.6 × 106 to ~2.6 × 105 ohm/cm2 as the thickness of the V2O5 xerogel thin film increases from 112 to 284 nm.
Here we report the synthesis of V2O5 nanostructures by a fast, simple, cost-effective, low-temper... more Here we report the synthesis of V2O5 nanostructures by a fast, simple, cost-effective, low-temperature chemical process; followed by the deposition of V2O5 xerogel thin films on a glass substrate by a sol-gel route. Phase analysis, phase transition, microstructural and electronic characterization studies are carried out by x-ray diffraction, texture coefficient analysis, field emission scanning electron microscopy, transmission electron microscopy (TEM), related selected area electron diffraction pattern (SAED) analysis, Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis, differential scanning calorimetry, and x-ray photoelectron spectroscopy techniques. Confirmatory TEM and SAED data analysis prove further that in this polycrystalline powder there is a unique localized existence of purely single crystalline V2O5 powder with a preferred orientation in the (0 1 0) direction. The most interesting result obtained in the present work is that the xerogel thin films exhibit an inherent capability to enhance the intrinsic resistance against contact induced deformations as more external load is applied during the nanoindentation experiments. In addition, both the nanohardness and Young's modulus of the films are found to be insensitive to load variations (e.g. 1 to 7 mN). These results are explained in terms of microstructural parameters, e.g. porosity and structural configuration.
The present work reports a simple, inexpensive method for synthesis of calcium hydroxide [Ca(OH)2... more The present work reports a simple, inexpensive method for synthesis of calcium hydroxide [Ca(OH)2] nanoparticles (CHNPs). The method involves chemical precipitation (CP) in aqueous medium at room temperature. Calcium nitrate dihydrate [Ca(NO3)2.2H2O] and sodium hydroxide were used as precursors. The CHNPs were characterized by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), Rietveld analysis, field‐emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM), BET surface area evaluation as well as particle size distribution analysis techniques. The results confirmed the synthesis of CHNPs as the major phase. The CHNPs exhibited an average size of about 350 nm. In addition, some calcite phase formed due to the inevitable carbonation process. A very minor amount of aragonite phase was also present. A schematically developed new qualitative model is proposed to explain the genesis and subsequent evolution of the various phases at th...
The present work reports the development of super-hydrophobic and optically opaque monolith silic... more The present work reports the development of super-hydrophobic and optically opaque monolith silica aerogel that float in water. The opaque silica aerogels were prepared by the two step sol-gel process using tetraethoxysilane (TEOS) as silica precursor followed by cost effective ambient pressure drying with various aging solutions. The surface texture and microstructural properties of various silica aerogels are studied by the nitrogen adsorptionand field emission scanning electron microscopy (FESEM) techniques, respectively. The elemental analysis was carried out by energy dispersive X-ray (EDX) spectroscopy. The Fourier transform infrared (FT-IR) spectroscopy was utilized to investigate the genesis of the hydrophobic property. The X-ray photoelectron spectroscopy (XPS) technique was used to understand the prevalent oxidation state at the surface of the silica aerogel. The water contact angle (WCA) of silica aerogel was evaluated by the WCA measurement technique. The silica aerogel ...
Abstract Nano-scale load (P) dependency of fracture toughness (K1C) of indium tin oxide (ITO) coa... more Abstract Nano-scale load (P) dependency of fracture toughness (K1C) of indium tin oxide (ITO) coating on silicon (Si) substrate is evaluated by nanoindentation based direct and energy methods. A Berkovich triangular diamond nanoindenter is used with nine different P values e.g., 10, 15, 20, 30, 40, 50, 100, 150 and 200 mN. Extensive utilization of both optical microscopy (OM) and field emission scanning electron microscopy (FESEM) techniques reveal that up to P ≤ 40 mN only the sharp radial cracks form from three corners of the nanoindent. However, for P > 40 mN, multiple cracks occur over and above the radial cracks. Finally, at P: 150–200 mN coating gets chipped off from the substrate. The K1C values of the ITO coating are calculated on the basis of both the conventional radial crack length measurement based method and the strain energy release based method. The K1C values are strongly sensitive to variations in P. Further, the strain energy method results in higher magnitudes of the K1C values.
Journal of the mechanical behavior of biomedical materials, 2018
Here we report for the very first time the synthesis of 100% phase pure calcium silicate nanopart... more Here we report for the very first time the synthesis of 100% phase pure calcium silicate nanoparticles (CSNPs) of the α-wollastonite phase without using any surfactant or peptizer at the lowest ever reported calcination temperature of 850 °C. Further, the phase purity is confirmed by quantitative phase analysis. The nano-network like microstructure of the CSNPs is characterized by FTIR, Raman, XRD, FESEM, TEM, TGA, DSC etc. techniques to derive the structure property correlations. The performance efficacies of the CSNPs against gram-positive e.g., S. pyogenes and S. aureus (NCIM2127) and gram-negative e.g., E. coli (NCIM2065) bacterial strains are studied. The biocompatibility of the CSNPs is established by using the conventional mouse embryonic osteoblast cell line (MC3T3). In addition, the biofilm inhibition efficacies of two varieties of CSNPs e.g., CSNPs(W) and CSNPs(WC) are investigated. Further, the interconnection between ROS e.g., superoxide (O) and hydroxyl radical (OH) gen...
The mesoporous silica materials find important applications in stimuli responsive drug delivery d... more The mesoporous silica materials find important applications in stimuli responsive drug delivery devices as biocompatible due to high surface area, large pore volume and tunable pore diameter. The large surface area of the mesoporous silica and its biocompatibility are the two major factors beyond its vast in vivo and in vitro applications. The present study considers three different types of commercially available silica namely, glass silica, nano silica and mesoporous silica (that already contained ordered pores) for the investigation of structural aspects responsible for formation of pores within the nano particles. The purpose of the work was to study the formation mechanism of the pores in mesoporous silica. It was observed that crystallite sizes and lattice strain are the two important structural parameters responsible for the formation of pores within the nano silica. Results reveal that the mesoporous silica has the critical crystallite size and the nano particles are under highly strained condition compared to the other silica samples. So this high lattice strain and crystallite size may be the key factors for the formation of pores within the nanoparticles under certain condition.
Highly crystalline titanium dioxide (TiO2) and gold nanoparticle (Au NP) incorporated TiO2 films ... more Highly crystalline titanium dioxide (TiO2) and gold nanoparticle (Au NP) incorporated TiO2 films (with varying Au NP concentration), prepared by sol-gel route have been compared as regards their optical absorption spectra. Results indicated an increase in absorbance as well as systematic shift of the absorption edge towards the visible region, with increase in Au NP concentration, upto a critical concentration, beyond which a decrease in absorbance was observed. The optical band gap, calculated from the UV-Vis spectra, shows significant decrease ( eV) with respect to pristine TiO2, for this critical concentration (10% Au NP in TiO2 by volume), above which the decrease () was found to be less. The morphology of the composite film at this critical concentration revealed a homogeneous microstructure comprising particles of ~50 nm. The optimum band gap decrease was found to be associated with a structural change from rutile for the pristine to anatase-rutile mixed phase for the composite film. X-ray diffraction and transmission electron microscopy results indicated a reasonably good match of the lattice spacing for the optimum film. Preliminary current–voltage measurements indicated decrease in electrical resistivity of the optimum Au–TiO2 film, compared to that of its pristine counterpart.
In the present work V2O5 xerogel thin films are deposited on quartz substrate by using a cost eff... more In the present work V2O5 xerogel thin films are deposited on quartz substrate by using a cost effective sol–gel based dip coating method. Films of thickness ~122, 224 and 284 nm are grown as the number of dipping varies from one to three. Phase analyses of the thin films are investigated by X-ray diffraction technique. The microstructural characterization is carried out by electron microscopy techniques. Crystalline, phase pure V2O5 thin films with uniform nanoporous microstructure are grown in the present work. Solar transmittance and reflectance of films are measured by UV–VIS–NIR spectrophotometer. The optical band gap, refractive index and extinction coefficient of the films are also evaluated. Further, the average solar absorptance and IR emittance are evaluated by solar spectrum reflectometer and emissometer, respectively. The solar transmittance and optical band gap decrease with the increase in film thickness from 122 to 284 nm while reverse trend is observed for solar absorptance. Refractive index (~1.95) and IR emittance (~0.75) of the nanoporous V2O5 xerogel thin films on quartz substrate are almost independent of film thickness. The sheet resistance value slightly decreases from ~1.6 × 106 to ~2.6 × 105 ohm/cm2 as the thickness of the V2O5 xerogel thin film increases from 112 to 284 nm.
Here we report the synthesis of V2O5 nanostructures by a fast, simple, cost-effective, low-temper... more Here we report the synthesis of V2O5 nanostructures by a fast, simple, cost-effective, low-temperature chemical process; followed by the deposition of V2O5 xerogel thin films on a glass substrate by a sol-gel route. Phase analysis, phase transition, microstructural and electronic characterization studies are carried out by x-ray diffraction, texture coefficient analysis, field emission scanning electron microscopy, transmission electron microscopy (TEM), related selected area electron diffraction pattern (SAED) analysis, Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis, differential scanning calorimetry, and x-ray photoelectron spectroscopy techniques. Confirmatory TEM and SAED data analysis prove further that in this polycrystalline powder there is a unique localized existence of purely single crystalline V2O5 powder with a preferred orientation in the (0 1 0) direction. The most interesting result obtained in the present work is that the xerogel thin films exhibit an inherent capability to enhance the intrinsic resistance against contact induced deformations as more external load is applied during the nanoindentation experiments. In addition, both the nanohardness and Young's modulus of the films are found to be insensitive to load variations (e.g. 1 to 7 mN). These results are explained in terms of microstructural parameters, e.g. porosity and structural configuration.
The present work reports a simple, inexpensive method for synthesis of calcium hydroxide [Ca(OH)2... more The present work reports a simple, inexpensive method for synthesis of calcium hydroxide [Ca(OH)2] nanoparticles (CHNPs). The method involves chemical precipitation (CP) in aqueous medium at room temperature. Calcium nitrate dihydrate [Ca(NO3)2.2H2O] and sodium hydroxide were used as precursors. The CHNPs were characterized by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), Rietveld analysis, field‐emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM), BET surface area evaluation as well as particle size distribution analysis techniques. The results confirmed the synthesis of CHNPs as the major phase. The CHNPs exhibited an average size of about 350 nm. In addition, some calcite phase formed due to the inevitable carbonation process. A very minor amount of aragonite phase was also present. A schematically developed new qualitative model is proposed to explain the genesis and subsequent evolution of the various phases at th...
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