Prakash Thanigainathan - Academia.edu (original) (raw)

Papers by Prakash Thanigainathan

IET Optoelectronics, 2020

A small portion of an optical fibre clad was removed and coated with methylamine hydroiodide by a... more A small portion of an optical fibre clad was removed and coated with methylamine hydroiodide by a slurry deposition process to develop an evanescent wave optical fibre ammonia sensor. The experiment was performed for a few volatile organic compounds in order to understand the selectivity and sensitivity. Prior to the gas sensing measurement, the methylamine hydroiodide sample was characterised using X-ray diffraction (XRD), scanning electron microscope with energy dispersive X-ray spectroscopy, Fourier transform infrared, Raman, diffuse reflectance and UV–Vis spectroscopy. In order to understand the sensor response, the samples were independently exposed to acetone, ammonia, ethanol and methanol gases and then analysed using the XRD technique. This analysis reveals that the structural variation is observed because of the ammonia exposure as compared to other gases. It has initiated to fabricate a clad-modified optical fibre ammonia sensor that exhibits ∼28% of the sensitivity. These experimental results are discussed in detail.

Electronic Materials Letters, 2013

ABSTRACT Grain boundary effect on the room temperature dielectric behavior in mechanically alloye... more ABSTRACT Grain boundary effect on the room temperature dielectric behavior in mechanically alloyed nanocrystalline CuAlO2 has been investigated using impedance spectroscopy under the applied DC bias voltages 0 V to 4.8 V in a periodic interval of 0.2 V. Analysis of impedance data confirms the existence of double Schottky potential barrier heights (Φ b ) between two adjacent grains (left and right side) with grain boundary and its influences in dielectric relaxation time (τ), dielectric constant (ɛ′) and dielectric loss (tan δ) factor. Also, clear evidence on the suppression of Φ b was demonstrated in the higher applied bias voltages with the parameter τ. At equilibrium state, τ is 0.63 ms and it was reduced to 0.13 ms after the 3.2 V applied DC bias. These observed DC bias voltage effects are obeying ‘brick layer model’ and also elucidates Φ b is playing a crucial role in controlling dielectric properties of nanomaterials.

Electronic Materials Letters, 2013

ABSTRACT Carrier transport through electrically active grain boundaries was studied under biased ... more ABSTRACT Carrier transport through electrically active grain boundaries was studied under biased condition using impedance spectroscopy in the frequency range 1 Hz to 1 MHz for a model system nanocrystalline CuSCN. Since, grain boundaries of semiconductors contain defects which often trap charge carriers and cause to form a potential barrier around them also plays a crucial role in the electrical properties of nanomaterials. The influence of bias voltage on relaxation times of grain (τ g ) and grain boundary (τ gb ) for our wet chemically prepared nanocrystalline CuSCN was estimated at a periodic increment of 0.35 V from 0 V to −4.2 V. In the static case with no applied bias voltage the grain boundary potential barrier height was found to be 0.144 eV. During each periodic increment of applied bias voltages, both the grain and grain boundary relaxation times are decreases it gives direct and unambiguous evidence on the suppression of grain boundary potential barrier height (Φ b ).

Electronic Materials Letters, 2012

Nanostructured semiconductors with different morphologies are used widely in various applications... more Nanostructured semiconductors with different morphologies are used widely in various applications in order to enhance their technological advancements compared with the bulk sample. This flourishing nanoscience field has enabled rapid developments that have created numerous opportunities for scienctific advancements with various devices. Considering large environmental impacts such as global warming, problems of nuclear waste storage and nuclear accidents, there is an urgent need for environmentally sustainable energy technologies such as solar cells and fuel cells. In the present paper, the role of nanostructured semiconductors in dyesensitized solar cells (DSSCs) is reviewed entensively. The review discusses the present developmental prospects of DSSCs and the problems associated with its layer materials and propose a method of overcoming these problems.

AIP Advances, 2011

The grain boundary space charge depletion layer in nanocrystalline alpha phase CuSCN is investiga... more The grain boundary space charge depletion layer in nanocrystalline alpha phase CuSCN is investigated by studying electrical properties using impedance spectroscopic analysis in frequency domain. The measurements were performed at room temperature in wide frequency range 1 Hz to 1 MHz under various DC bias applied voltages ranges from 0 V to -2.1 V. The effect of bias on grain

Science of Advanced Materials, 2012

ABSTRACT Nanocrystals of wide bandgap p-type semiconductors CuAlO2 by mechanical alloying and β-C... more ABSTRACT Nanocrystals of wide bandgap p-type semiconductors CuAlO2 by mechanical alloying and β-CuSCN by chemical precipitation method was synthesized. Both the nanocrystals are dispersed in poly(vinyl carbazole) dissolved dichloromethane solution to create nanocrystals embedded polymeric matrix by dip coating method. Applicability of such materials as a solid hole-transporter in dye sensitized solar cell was investigated under 15 mW/cm2 stimulated white light. Performance of the device constructed and the physical properties both the hole-transporter materials are investigated, which are discussed in detail.

International Nano Letters, 2012

Nanocrystalline CuAlO 2 was synthesized by mechanical alloying of Cu 2 O and α-Al 2 O 3 powders i... more Nanocrystalline CuAlO 2 was synthesized by mechanical alloying of Cu 2 O and α-Al 2 O 3 powders in the molar ratio of 1:1 for 20 h in toluene medium with tungsten carbide balls and vials using planetary ball mill. The ball milling was carried out at 300 rpm with a ball to powder weight ratio of 10:1 and then annealed at 1373 K in a platinum crucible for 20 h to get CuAlO 2 phase with average crystallite size 45 nm. Complex impedance spectroscopic measurement in the frequency region 1 Hz to 10 MHz between the temperatures 333 to 473 K was carried out for nanocrystalline CuAlO 2 sample. The obtained complex impedance data was analyzed for AC conductivities, DC and AC conductivities correlations and crossover frequencies (f co). The BNN (Barton, Nakajima and Namikawa) relation was applied to understand the correlation between DC and AC conductivities. The observed experimental results were discussed in the paper.

Advanced Materials Letters, 2011

Copper (I) iodide (CuI) has been synthesized by wet chemical route at room temperature using fres... more Copper (I) iodide (CuI) has been synthesized by wet chemical route at room temperature using freshly prepared copper oxide (CuO) as a precursor. The as-prepared CuI exists in -phase and it undergoes two structural phase transition between room temperature and its melting point. Differential scanning calorimetry measurement in both heating and cooling cycles confirms its structural reversible phase transitions from  to  phase then from  to  phase. In order to understand the underlying physical properties before and after transitions induced by temperature was studied by X-ray diffraction, scanning electron microscopy, fluorescence, fourier transformed infrared spectroscopy and thermal analysis using TGA, DTA and DSC.

In this study, cadmium oxide was prepared by thermal decomposition from their respective acetate ... more In this study, cadmium oxide was prepared by thermal decomposition from their respective acetate without the use of any additive. This method is simple, fast and cost effective compared to other methods. Thermo gravimetric analysis of cadmium acetate was carried out before the actual synthesis process, to determine the dehydration, acetate decomposition and oxide formation temperatures. The structure and crystalline size of the prepared samples were confirmed by X-ray diffraction analysis. The XRD results indicate the formation of single crystalline CdO having a cubic structure. The HR-SEM images indicate the formation of pyramid shaped nano cadmium oxide. The bandgap value of pure CdO was examined by UV-Vis spectrometer. Further the sample was used for degradation of various dyes under UV light condition.

Soft Nanoscience Letters, 2011

Nickel masters are widely used to produce surface relief grating like patterned antireflection co... more Nickel masters are widely used to produce surface relief grating like patterned antireflection coatings of polysiloxane material by simple embossing process. In the present work, patterned nickel master was prepared by using aluminium template, which is a foil peeled off from the commercial compact disk. Nickel was deposited using Watts nickel bath by pulsed electrodeposition for different relaxation times on patterned aluminium template. The deposition led to the transfer of patterns of aluminium replica to the nickel deposit. After deposition, the aluminium template was etched out chemically. Observation under an optical microscope showed that the obtained pattern was highly homogenous only for T on = 0.1 ms, T off = 0.9 ms duty cycles as compared with other 'on' and 'off' times of pulse cycles. This simple single step cost effective nickel master can serve as stamps for the subsequent embossing process. The preparation conditions and its salient features are discussed in this paper in detail.

Electronic Materials Letters, 2013

The effect of crystallite size and applied DC bias voltage on dielectric permittivity of CuO was ... more The effect of crystallite size and applied DC bias voltage on dielectric permittivity of CuO was studied using impedance spectroscopy. The measurements were performed at room temperature in a wide frequency range of 1 Hz to 1 MHz under applied DC bias voltages from 0 to 3 V in the periodic increment of 0.2 V. The observed applied DC bias voltage effect on giant dielectric constant (ε' = 10 4) were analyzed with 'grain boundary double Schottky potential barrier height model'. The percentage of tunability (T %) at the frequency 100 Hz is found to be 45.5% for the case of nanocrystalline CuO in contrast to 0% tunability in bulk CuO.

IET Nanobiotechnology, 2013

Nanoenabled drug carriers are emerging as alternatives to conventional small-molecule drugs and t... more Nanoenabled drug carriers are emerging as alternatives to conventional small-molecule drugs and their in-vitro biocompatibility evaluation with blood components is a necessary part of early preclinical development. In the present study, Chitosan-based bionanocomposites of sol-gel derived TiO 2 and SiO 2 were synthesised by the ex situ process. Samples were characterised by X-ray diffraction, Fourier transformed infrared spectrophotometer, transmission electron microscopy and selected area electron diffraction techniques. The analysis reveals the formation of single-phase oxides and their bionanocomposites. Haemolysis (destruction of red blood cell) study was performed by spectrophotometer to assess the haemocompatibility nature as a function of different incubation time. Experimental results reveal the percentage of haemolysis increase with the increase of the incubation time, but it was found to be <2%. This confirms our bionanocomposites are more haemocompatible as compared with respective nanocrystalline ceramics. Also, the interaction of our bionanocomposites with serum proteins at various incubation periods (1-24 h) were investigated using sodium dodecyl sulphate-polyacrylamide gel experiment, the obtained results were discussed in details.

International Conference on Nanoscience, Engineering and Technology (ICONSET 2011), 2011

International Nano Letters, 2013

In this work, transparent heterojunction between zinc oxide (ZnO) and poly(N-vinyl carbazole) (PV... more In this work, transparent heterojunction between zinc oxide (ZnO) and poly(N-vinyl carbazole) (PVK) was fabricated by solution processing techniques such as spin-coating and dip-coating techniques; then, its performance was studied using current (I)-voltage (V) measurement at room temperature. Before fabricating the heterojunction, initially, the growth characteristics of both thin films were independently optimized on a well-cleaned glass substrate, then its structural properties, optical properties, and surface topography were characterized using an Xray diffractometer, UV-VIS-NIR spectrophotometer, and atomic force microscope, respectively. The structural analysis confirms the existence of a PVK thin film in amorphous nature and ZnO thin film in hexagonal crystal structure. The transparent nature of the heterojunction was found to be more than 85% in the visible and NIR regions with the absorption onset in the ultraviolet region. The observed experimental results explored the possibilities of fabricating ZnO/PVK transparent heterojunction by solution-based routes on a transparent fluorine-doped tin oxide substrate for transparent electronics applications.

Pramana, 2005

The ultra high vacuum chamber was developed in the Department of Nuclear Physics, University of M... more The ultra high vacuum chamber was developed in the Department of Nuclear Physics, University of Madras with the funding from DST, India. This UHV chamber is used to prepare nanocrystalline materials by inert gas condensation technique (IGCT). Nanocrystalline materials such as PbF 2 , Mn 2+-doped PbF 2 , Sn-doped In 2 O 3 (ITO), ZnO, Al 2 O 3 , Ag 2 O, CdO, CuO, ZnSe:ZnO etc., were prepared by this technique and characterized. Results of some of these materials will be presented in this paper. In solid-state 207 Pb NMR on PbF 2 a separate signal due to the presence of grain boundary has been observed. The structural phase transition pressure during the phase transformation from the cubic phase to orthorhombic phase under high pressure shows an increase with the decrease in grain size. Presence of electronic centres in nanocrystalline PbF2 is observed from Raman studies and the same has been confirmed by photoluminescence studies. Al 2 O 3 was prepared and 56 Fe ions were implanted. After implantation segregation of 56 Fe ions was examined by SEM. The oxidation properties of ITO were studied by HRTEM. As against the expectation of oxide coating on individual nanograins of In-Sn alloy, ITO nanograins grew into faceted nanograins on heat treatment in air and O 2 atmosphere. The growth of ITO under O 2 atmosphere showed pentagon symmetry. The PMN was initially prepared by solid-state reaction. Further, this PMN relaxor material will be used to convert into nanocrystalline PMN by IGCT with sputtering and will be studied.

Journal of Nanoscience and Nanotechnology, 2009

The search for colossal dielectric constant materials is imperative because of their potential fo... more The search for colossal dielectric constant materials is imperative because of their potential for promising applications for the areas of device miniaturization and energy storage. In this work, (Nd 0.5 Nb 0.5) x Ti 1-x O 2 ceramics is prepared via the solid-state reaction route. The microstructure, crystal structures, and dielectric properties of (Nd 0.5 Nb 0.5) x Ti 1-x O 2 ceramics are investigated. It is proved that schottky barrier exists at grain boundary by measuring impedance spectrum of different DC biases and C-V curve. The grain boundary characteristics of the ceramics are studied. It is found that the proper second phase is beneficial to increase the grain boundary resistance and restrain the long range movement of electrons, so that the material keeps low dielectric loss and improves the temperature stability. But too much of second phase will deteriorate performance due to excessive space charges. In addition, all the (Nd 0.5 Nb 0.5) x Ti 1-x O 2 ceramics displays a colossal dielectric constant (> 10 4), especially a high dielectric constant (2.55×10 4) and low dielectric loss (0.023) at 1 kHz and room temperature which can be obtain in (Nd 0.5 Nb 0.5) x Ti 1-x O 2 ceramic with x=3%. The dielectric properties of (Nd 0.5 Nb 0.5) x Ti 1-x O 2 ceramics can be explained by internal barrier layer capacitor (IBLC) model, which can be optimized by balancing grain size, barrier height and barrier width.

Journal of Nanoscience and Nanotechnology, 2008

Nanocrystalline p-type semiconductor copper aluminum oxide (CuAlO2) has been synthesized by mecha... more Nanocrystalline p-type semiconductor copper aluminum oxide (CuAlO2) has been synthesized by mechanical alloying using freshly prepared Cu2O and α-Al2O3 nanocrystals in toluene medium. A study on structural property performed with different alloying and post annealing durations, by X-ray diffraction (XRD) reveals the formation of single phase with average crystallite size ∼45 nm. Optical absorbance onset at 364.5 nm confirms its wide band gap nature (Eg = 3.4 eV) and the fluorescence emission behaviour (390 nm) confirms its direct band type transition. The activation energy for electrical conduction has been calculated by Arrhenius plots using impedance measurement. Both grain and grain boundary conductivity takes place with almost equal activation energies of ∼0.45 eV. The paper discusses synthesis, structural, optical and electrical properties of delafossite CuAlO2 in detail.

Journal of Molecular Liquids, 2014

ZnO nanorods with substitution of different transition metal ions (Hg, Cd, Cu, Mn and Ni) were pr... more ZnO nanorods with substitution of different transition metal ions (Hg, Cd, Cu, Mn and Ni) were prepared by simple thermal decomposition process. Structural and microstructural properties of all the as-synthesized samples were characterized using the X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electrical conductivity and dielectric properties of all the samples have been studied over a wide frequency range 1 Hz to 1 MHz by complex impedance spectroscopic measurements at room temperature. The dc conductivity (σ dc) was extracted for all the samples by extrapolating frequency independent region of respective ac conductivity (σ ac) plot. Frequency variation of the dielectric loss (tanδ) of the samples has been obtained from impedance data and the same plot was further used to extract dielectric relaxation time (τ). Reasons for the tailored conductivity as well as relaxation time because of substitution in ZnO nanorods were discussed in detail.

Journal of Applied Physics, 2007

Transparent semiconductor CuAlO2 in nanodimension was prepared by mechanical alloying of Cu2O and... more Transparent semiconductor CuAlO2 in nanodimension was prepared by mechanical alloying of Cu2O and alpha-Al2O3 powders in toluene medium. The formation of single phase CuAlO2 with an average crystallite size of 45 nm was confirmed by x-ray diffraction analysis. The nanocrystalline nature of CuAlO2 was confirmed by atomic force microscopy. Frequency-dependent dielectric property measurements and the relaxation behavior were studied using

IET Optoelectronics, 2020

A small portion of an optical fibre clad was removed and coated with methylamine hydroiodide by a... more A small portion of an optical fibre clad was removed and coated with methylamine hydroiodide by a slurry deposition process to develop an evanescent wave optical fibre ammonia sensor. The experiment was performed for a few volatile organic compounds in order to understand the selectivity and sensitivity. Prior to the gas sensing measurement, the methylamine hydroiodide sample was characterised using X-ray diffraction (XRD), scanning electron microscope with energy dispersive X-ray spectroscopy, Fourier transform infrared, Raman, diffuse reflectance and UV–Vis spectroscopy. In order to understand the sensor response, the samples were independently exposed to acetone, ammonia, ethanol and methanol gases and then analysed using the XRD technique. This analysis reveals that the structural variation is observed because of the ammonia exposure as compared to other gases. It has initiated to fabricate a clad-modified optical fibre ammonia sensor that exhibits ∼28% of the sensitivity. These experimental results are discussed in detail.

Electronic Materials Letters, 2013

ABSTRACT Grain boundary effect on the room temperature dielectric behavior in mechanically alloye... more ABSTRACT Grain boundary effect on the room temperature dielectric behavior in mechanically alloyed nanocrystalline CuAlO2 has been investigated using impedance spectroscopy under the applied DC bias voltages 0 V to 4.8 V in a periodic interval of 0.2 V. Analysis of impedance data confirms the existence of double Schottky potential barrier heights (Φ b ) between two adjacent grains (left and right side) with grain boundary and its influences in dielectric relaxation time (τ), dielectric constant (ɛ′) and dielectric loss (tan δ) factor. Also, clear evidence on the suppression of Φ b was demonstrated in the higher applied bias voltages with the parameter τ. At equilibrium state, τ is 0.63 ms and it was reduced to 0.13 ms after the 3.2 V applied DC bias. These observed DC bias voltage effects are obeying ‘brick layer model’ and also elucidates Φ b is playing a crucial role in controlling dielectric properties of nanomaterials.

Electronic Materials Letters, 2013

ABSTRACT Carrier transport through electrically active grain boundaries was studied under biased ... more ABSTRACT Carrier transport through electrically active grain boundaries was studied under biased condition using impedance spectroscopy in the frequency range 1 Hz to 1 MHz for a model system nanocrystalline CuSCN. Since, grain boundaries of semiconductors contain defects which often trap charge carriers and cause to form a potential barrier around them also plays a crucial role in the electrical properties of nanomaterials. The influence of bias voltage on relaxation times of grain (τ g ) and grain boundary (τ gb ) for our wet chemically prepared nanocrystalline CuSCN was estimated at a periodic increment of 0.35 V from 0 V to −4.2 V. In the static case with no applied bias voltage the grain boundary potential barrier height was found to be 0.144 eV. During each periodic increment of applied bias voltages, both the grain and grain boundary relaxation times are decreases it gives direct and unambiguous evidence on the suppression of grain boundary potential barrier height (Φ b ).

Electronic Materials Letters, 2012

Nanostructured semiconductors with different morphologies are used widely in various applications... more Nanostructured semiconductors with different morphologies are used widely in various applications in order to enhance their technological advancements compared with the bulk sample. This flourishing nanoscience field has enabled rapid developments that have created numerous opportunities for scienctific advancements with various devices. Considering large environmental impacts such as global warming, problems of nuclear waste storage and nuclear accidents, there is an urgent need for environmentally sustainable energy technologies such as solar cells and fuel cells. In the present paper, the role of nanostructured semiconductors in dyesensitized solar cells (DSSCs) is reviewed entensively. The review discusses the present developmental prospects of DSSCs and the problems associated with its layer materials and propose a method of overcoming these problems.

AIP Advances, 2011

The grain boundary space charge depletion layer in nanocrystalline alpha phase CuSCN is investiga... more The grain boundary space charge depletion layer in nanocrystalline alpha phase CuSCN is investigated by studying electrical properties using impedance spectroscopic analysis in frequency domain. The measurements were performed at room temperature in wide frequency range 1 Hz to 1 MHz under various DC bias applied voltages ranges from 0 V to -2.1 V. The effect of bias on grain

Science of Advanced Materials, 2012

ABSTRACT Nanocrystals of wide bandgap p-type semiconductors CuAlO2 by mechanical alloying and β-C... more ABSTRACT Nanocrystals of wide bandgap p-type semiconductors CuAlO2 by mechanical alloying and β-CuSCN by chemical precipitation method was synthesized. Both the nanocrystals are dispersed in poly(vinyl carbazole) dissolved dichloromethane solution to create nanocrystals embedded polymeric matrix by dip coating method. Applicability of such materials as a solid hole-transporter in dye sensitized solar cell was investigated under 15 mW/cm2 stimulated white light. Performance of the device constructed and the physical properties both the hole-transporter materials are investigated, which are discussed in detail.

International Nano Letters, 2012

Nanocrystalline CuAlO 2 was synthesized by mechanical alloying of Cu 2 O and α-Al 2 O 3 powders i... more Nanocrystalline CuAlO 2 was synthesized by mechanical alloying of Cu 2 O and α-Al 2 O 3 powders in the molar ratio of 1:1 for 20 h in toluene medium with tungsten carbide balls and vials using planetary ball mill. The ball milling was carried out at 300 rpm with a ball to powder weight ratio of 10:1 and then annealed at 1373 K in a platinum crucible for 20 h to get CuAlO 2 phase with average crystallite size 45 nm. Complex impedance spectroscopic measurement in the frequency region 1 Hz to 10 MHz between the temperatures 333 to 473 K was carried out for nanocrystalline CuAlO 2 sample. The obtained complex impedance data was analyzed for AC conductivities, DC and AC conductivities correlations and crossover frequencies (f co). The BNN (Barton, Nakajima and Namikawa) relation was applied to understand the correlation between DC and AC conductivities. The observed experimental results were discussed in the paper.

Advanced Materials Letters, 2011

Copper (I) iodide (CuI) has been synthesized by wet chemical route at room temperature using fres... more Copper (I) iodide (CuI) has been synthesized by wet chemical route at room temperature using freshly prepared copper oxide (CuO) as a precursor. The as-prepared CuI exists in -phase and it undergoes two structural phase transition between room temperature and its melting point. Differential scanning calorimetry measurement in both heating and cooling cycles confirms its structural reversible phase transitions from  to  phase then from  to  phase. In order to understand the underlying physical properties before and after transitions induced by temperature was studied by X-ray diffraction, scanning electron microscopy, fluorescence, fourier transformed infrared spectroscopy and thermal analysis using TGA, DTA and DSC.

In this study, cadmium oxide was prepared by thermal decomposition from their respective acetate ... more In this study, cadmium oxide was prepared by thermal decomposition from their respective acetate without the use of any additive. This method is simple, fast and cost effective compared to other methods. Thermo gravimetric analysis of cadmium acetate was carried out before the actual synthesis process, to determine the dehydration, acetate decomposition and oxide formation temperatures. The structure and crystalline size of the prepared samples were confirmed by X-ray diffraction analysis. The XRD results indicate the formation of single crystalline CdO having a cubic structure. The HR-SEM images indicate the formation of pyramid shaped nano cadmium oxide. The bandgap value of pure CdO was examined by UV-Vis spectrometer. Further the sample was used for degradation of various dyes under UV light condition.

Soft Nanoscience Letters, 2011

Nickel masters are widely used to produce surface relief grating like patterned antireflection co... more Nickel masters are widely used to produce surface relief grating like patterned antireflection coatings of polysiloxane material by simple embossing process. In the present work, patterned nickel master was prepared by using aluminium template, which is a foil peeled off from the commercial compact disk. Nickel was deposited using Watts nickel bath by pulsed electrodeposition for different relaxation times on patterned aluminium template. The deposition led to the transfer of patterns of aluminium replica to the nickel deposit. After deposition, the aluminium template was etched out chemically. Observation under an optical microscope showed that the obtained pattern was highly homogenous only for T on = 0.1 ms, T off = 0.9 ms duty cycles as compared with other 'on' and 'off' times of pulse cycles. This simple single step cost effective nickel master can serve as stamps for the subsequent embossing process. The preparation conditions and its salient features are discussed in this paper in detail.

Electronic Materials Letters, 2013

The effect of crystallite size and applied DC bias voltage on dielectric permittivity of CuO was ... more The effect of crystallite size and applied DC bias voltage on dielectric permittivity of CuO was studied using impedance spectroscopy. The measurements were performed at room temperature in a wide frequency range of 1 Hz to 1 MHz under applied DC bias voltages from 0 to 3 V in the periodic increment of 0.2 V. The observed applied DC bias voltage effect on giant dielectric constant (ε' = 10 4) were analyzed with 'grain boundary double Schottky potential barrier height model'. The percentage of tunability (T %) at the frequency 100 Hz is found to be 45.5% for the case of nanocrystalline CuO in contrast to 0% tunability in bulk CuO.

IET Nanobiotechnology, 2013

Nanoenabled drug carriers are emerging as alternatives to conventional small-molecule drugs and t... more Nanoenabled drug carriers are emerging as alternatives to conventional small-molecule drugs and their in-vitro biocompatibility evaluation with blood components is a necessary part of early preclinical development. In the present study, Chitosan-based bionanocomposites of sol-gel derived TiO 2 and SiO 2 were synthesised by the ex situ process. Samples were characterised by X-ray diffraction, Fourier transformed infrared spectrophotometer, transmission electron microscopy and selected area electron diffraction techniques. The analysis reveals the formation of single-phase oxides and their bionanocomposites. Haemolysis (destruction of red blood cell) study was performed by spectrophotometer to assess the haemocompatibility nature as a function of different incubation time. Experimental results reveal the percentage of haemolysis increase with the increase of the incubation time, but it was found to be <2%. This confirms our bionanocomposites are more haemocompatible as compared with respective nanocrystalline ceramics. Also, the interaction of our bionanocomposites with serum proteins at various incubation periods (1-24 h) were investigated using sodium dodecyl sulphate-polyacrylamide gel experiment, the obtained results were discussed in details.

International Conference on Nanoscience, Engineering and Technology (ICONSET 2011), 2011

International Nano Letters, 2013

In this work, transparent heterojunction between zinc oxide (ZnO) and poly(N-vinyl carbazole) (PV... more In this work, transparent heterojunction between zinc oxide (ZnO) and poly(N-vinyl carbazole) (PVK) was fabricated by solution processing techniques such as spin-coating and dip-coating techniques; then, its performance was studied using current (I)-voltage (V) measurement at room temperature. Before fabricating the heterojunction, initially, the growth characteristics of both thin films were independently optimized on a well-cleaned glass substrate, then its structural properties, optical properties, and surface topography were characterized using an Xray diffractometer, UV-VIS-NIR spectrophotometer, and atomic force microscope, respectively. The structural analysis confirms the existence of a PVK thin film in amorphous nature and ZnO thin film in hexagonal crystal structure. The transparent nature of the heterojunction was found to be more than 85% in the visible and NIR regions with the absorption onset in the ultraviolet region. The observed experimental results explored the possibilities of fabricating ZnO/PVK transparent heterojunction by solution-based routes on a transparent fluorine-doped tin oxide substrate for transparent electronics applications.

Pramana, 2005

The ultra high vacuum chamber was developed in the Department of Nuclear Physics, University of M... more The ultra high vacuum chamber was developed in the Department of Nuclear Physics, University of Madras with the funding from DST, India. This UHV chamber is used to prepare nanocrystalline materials by inert gas condensation technique (IGCT). Nanocrystalline materials such as PbF 2 , Mn 2+-doped PbF 2 , Sn-doped In 2 O 3 (ITO), ZnO, Al 2 O 3 , Ag 2 O, CdO, CuO, ZnSe:ZnO etc., were prepared by this technique and characterized. Results of some of these materials will be presented in this paper. In solid-state 207 Pb NMR on PbF 2 a separate signal due to the presence of grain boundary has been observed. The structural phase transition pressure during the phase transformation from the cubic phase to orthorhombic phase under high pressure shows an increase with the decrease in grain size. Presence of electronic centres in nanocrystalline PbF2 is observed from Raman studies and the same has been confirmed by photoluminescence studies. Al 2 O 3 was prepared and 56 Fe ions were implanted. After implantation segregation of 56 Fe ions was examined by SEM. The oxidation properties of ITO were studied by HRTEM. As against the expectation of oxide coating on individual nanograins of In-Sn alloy, ITO nanograins grew into faceted nanograins on heat treatment in air and O 2 atmosphere. The growth of ITO under O 2 atmosphere showed pentagon symmetry. The PMN was initially prepared by solid-state reaction. Further, this PMN relaxor material will be used to convert into nanocrystalline PMN by IGCT with sputtering and will be studied.

Journal of Nanoscience and Nanotechnology, 2009

The search for colossal dielectric constant materials is imperative because of their potential fo... more The search for colossal dielectric constant materials is imperative because of their potential for promising applications for the areas of device miniaturization and energy storage. In this work, (Nd 0.5 Nb 0.5) x Ti 1-x O 2 ceramics is prepared via the solid-state reaction route. The microstructure, crystal structures, and dielectric properties of (Nd 0.5 Nb 0.5) x Ti 1-x O 2 ceramics are investigated. It is proved that schottky barrier exists at grain boundary by measuring impedance spectrum of different DC biases and C-V curve. The grain boundary characteristics of the ceramics are studied. It is found that the proper second phase is beneficial to increase the grain boundary resistance and restrain the long range movement of electrons, so that the material keeps low dielectric loss and improves the temperature stability. But too much of second phase will deteriorate performance due to excessive space charges. In addition, all the (Nd 0.5 Nb 0.5) x Ti 1-x O 2 ceramics displays a colossal dielectric constant (> 10 4), especially a high dielectric constant (2.55×10 4) and low dielectric loss (0.023) at 1 kHz and room temperature which can be obtain in (Nd 0.5 Nb 0.5) x Ti 1-x O 2 ceramic with x=3%. The dielectric properties of (Nd 0.5 Nb 0.5) x Ti 1-x O 2 ceramics can be explained by internal barrier layer capacitor (IBLC) model, which can be optimized by balancing grain size, barrier height and barrier width.

Journal of Nanoscience and Nanotechnology, 2008

Nanocrystalline p-type semiconductor copper aluminum oxide (CuAlO2) has been synthesized by mecha... more Nanocrystalline p-type semiconductor copper aluminum oxide (CuAlO2) has been synthesized by mechanical alloying using freshly prepared Cu2O and α-Al2O3 nanocrystals in toluene medium. A study on structural property performed with different alloying and post annealing durations, by X-ray diffraction (XRD) reveals the formation of single phase with average crystallite size ∼45 nm. Optical absorbance onset at 364.5 nm confirms its wide band gap nature (Eg = 3.4 eV) and the fluorescence emission behaviour (390 nm) confirms its direct band type transition. The activation energy for electrical conduction has been calculated by Arrhenius plots using impedance measurement. Both grain and grain boundary conductivity takes place with almost equal activation energies of ∼0.45 eV. The paper discusses synthesis, structural, optical and electrical properties of delafossite CuAlO2 in detail.

Journal of Molecular Liquids, 2014

ZnO nanorods with substitution of different transition metal ions (Hg, Cd, Cu, Mn and Ni) were pr... more ZnO nanorods with substitution of different transition metal ions (Hg, Cd, Cu, Mn and Ni) were prepared by simple thermal decomposition process. Structural and microstructural properties of all the as-synthesized samples were characterized using the X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electrical conductivity and dielectric properties of all the samples have been studied over a wide frequency range 1 Hz to 1 MHz by complex impedance spectroscopic measurements at room temperature. The dc conductivity (σ dc) was extracted for all the samples by extrapolating frequency independent region of respective ac conductivity (σ ac) plot. Frequency variation of the dielectric loss (tanδ) of the samples has been obtained from impedance data and the same plot was further used to extract dielectric relaxation time (τ). Reasons for the tailored conductivity as well as relaxation time because of substitution in ZnO nanorods were discussed in detail.

Journal of Applied Physics, 2007

Transparent semiconductor CuAlO2 in nanodimension was prepared by mechanical alloying of Cu2O and... more Transparent semiconductor CuAlO2 in nanodimension was prepared by mechanical alloying of Cu2O and alpha-Al2O3 powders in toluene medium. The formation of single phase CuAlO2 with an average crystallite size of 45 nm was confirmed by x-ray diffraction analysis. The nanocrystalline nature of CuAlO2 was confirmed by atomic force microscopy. Frequency-dependent dielectric property measurements and the relaxation behavior were studied using