Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, Jan 14, 2015
Surfactants are used to prevent the irreversible aggregation of partially refolded proteins and t... more Surfactants are used to prevent the irreversible aggregation of partially refolded proteins and they also assist in protein refolding. We have reported the design and screening of gemini surfactant to stabilize bovine serum albumin (BSA) with the help of computational tool (iGEMDOCK). A series of gemini surfactant has been designed based on bis-N-alkyl nicotinate dianion via varying the alkyl group and anion. On changing the alkyl group and anion of the surfactant, the value of Log P changes means polarity of surfactant can be tuned. Further, the virtual screening of the gemini surfactant has been carried out based on generic evolutionary method. Herein, thermodynamic data was studied to determine the potential of gemini surfactant as BSA stabilizer. Computational tools help to find out the efficient gemini surfactant to stabilize the BSA rather than to use the surfactant randomly and directionless for the stabilization. It can be confirmed through the experimental techniques. Previously, researcher synthesized one of the designed and used gemini surfactant to stabilize the BSA and their interactions were confirmed through various techniques and computational docking. But herein, the authors find the most competent gemini surfactant to stabilize BSA using computational tools on the basis of energy score. Different from the single chain surfactant, the gemini surfactants exhibit much stronger electrostatic and hydrophobic interactions with the protein and are thus effective at much lower concentrations. Based on the present study, it is expected that gemini surfactants may prove useful in the protein stabilization operations and may thus be effectively employed to circumvent the problem of misfolding and aggregation.
The chromium and titanium oxynitride films on glass substrate were deposited by using reactive RF... more The chromium and titanium oxynitride films on glass substrate were deposited by using reactive RF magnetron sputtering in the present work. The structural and optical properties of the chromium and titanium oxynitride films as a function of power variations are investigated. The chromium oxynitride films are crystalline even at low power of Cr target (≥60 W) but the titanium oxynitride films are amorphous at low target power of Ti target (≤90 W) as observed from glancing incidence X-ray diffraction (GIXRD) patterns. The residual stress and strain of the chromium oxynitride films are calculated by sin2 ψ method, as the average crystallite size decreases with the increase in sputtering power of the Cr target, higher stress and strain values are observed. The chromium oxynitride films changes from hydrophilic to hydrophobic with the increase of contact angle value from 86.4° to 94.1°, but the deposited titanium oxynitride films are hydrophilic as observed from contact angle measurements. The changes in surface energy were calculated using contact angle measurements to substantiate the hydrophobic properties of the films. UV–vis and NIR spectrophotometer were used to obtain the transmission and absorption spectra, and the later was used for determining band gap values of the films, respectively. The refractive index of chromium and titanium oxynitride films increases with film packing density due to formation of crystalline chromium and titanium oxynitride films with the gradual rise in deposition rate as a result of increase in target powers.► Ti-doped chromium oxynitride and Cr-doped titanium oxynitride films at Cr and Ti targets powers. ► Such co-sputtering studies using helium as inert gas is rare in literature. ► This article deals with a systematic study on structural, optical and hydrophobic properties of films. ► The chromium oxynitride films changes from hydrophilic to hydrophobic. ► The surface energy is sensitive to the contact angle and optical properties like n, Eg, %T are tailored.
The thermally stimulated discharge behaviour of vacuum-deposited polyvinyl fluoride films (about ... more The thermally stimulated discharge behaviour of vacuum-deposited polyvinyl fluoride films (about 0022-3727/30/8/014/img7 thick) studied as a function of polarization temperature (313 - 453 K) and polarization field (1 - 0022-3727/30/8/014/img8) shows a single relaxation peak whose peak temperature, charge, activation energy and so on depend strongly on the polarization parameters. The peak has been attributed to space-charge distributed polarization due to the migration of the charge carriers, injected from the electrodes or present inherently, over macroscopic distances and their subsequent trapping; the trapping levels being distributed in the range of energies 0.55 - 0.69 eV.
In this study, we report the synthesis and antibacterial activity of a new series of 5-amido-1-(2... more In this study, we report the synthesis and antibacterial activity of a new series of 5-amido-1-(2,4dinitrophenyl)-1H-4-pyrazolecarbonitriles. Our results show that all compounds exhibit antimicrobial activities against methicillin susceptible Staphylococcus aureus and methicillin resistant S. aureus with MIC values of 25.1 and 91.0 lM.
Catharanthus roseus is a medicinal herb found in many tropical and subtropical regions around the... more Catharanthus roseus is a medicinal herb found in many tropical and subtropical regions around the world. This plant produces a diverse array of secondary metabolites that are pharmaceutically important like vinblastine and vincristine used as chemotherapeutic agents in the treatment of several types of cancers. Low yield of these vinca alkaloids from the plant in vivo and the challenges to meet their high demand worldwide led researchers to develop various in vitro techniques like hairy root culture, callus cultures, shoot cultures, metabolic engineering and regulation studies to increase their production. The present review gives an account of the various phytochemicals derived from the plant and the pharmacological aspects of secondary metabolites studied. Present review also highlights the biotechnological prospects of an efficient and alternative means of production of valuable metabolites from Catharanthus roseus and also from rich microflora residing inside the plant tissues. It gives an emphasis on the need of exploration of diverse niches of endophytes.
... Sci. Technol., B 16 (1998) 1305. 4. A. Costa, S. Camargo Jr., C. Achete, R. Carius, Thin Soli... more ... Sci. Technol., B 16 (1998) 1305. 4. A. Costa, S. Camargo Jr., C. Achete, R. Carius, Thin Solid Films 377-378 (2000) 243. 5. YS Katharria, S. Kumar, F. Singh, JC Pivin, D. Kanjilal, J. Phys., D, Appl. Phys. 39 (2006) 3969, and the refs. therein.
We report on the growth of terbium iron garnet (TbIG, Tb 3 Fe 5 O 12 ) thin films having anomalou... more We report on the growth of terbium iron garnet (TbIG, Tb 3 Fe 5 O 12 ) thin films having anomalously large coercivity and in-plane easy axis of magnetization. The TbIG thin films were prepared at room temperature (RT) on Pt/Si(1 0 0) substrates by pulsed laser deposition technique. The films deposited at RT were X-ray amorphous and do not show any magnetic order. Annealing of the RT deposited film at 900 1C resulted into fully textured (532) TbIG film. Atomic force microscopy and cross-sectional scanning electron microscopy studies of the TbIG films showed good surface quality with an average surface roughness of 5.0 nm and thickness of about 300 nm, respectively. The M-H loops measured at 20 K for TbIG films, exhibit about an order of magnitude enhancement in the coercivity value (H c ) than the single crystal. In-plane and out-of-plane M-H loops revealed that the easy axis of the magnetization lies within the film's plane. In-plane magnetization combining with large H c value of the TbIG thin film may be of scientific interest for the possible applications.
Nanocrystalline powders of cubic (Zn, Cd) S and Zn x Cd 1− x S were synthesized by the chemical p... more Nanocrystalline powders of cubic (Zn, Cd) S and Zn x Cd 1− x S were synthesized by the chemical precipitate method from the aqueous solution of sodium sulphide, zinc nitrate and cadmium nitrate at 277 K without any capping agent. High temperature X-ray diffraction ( ...
The aim of this work is to develop zirconium oxynitride coatings by RF magnetron sputtering on si... more The aim of this work is to develop zirconium oxynitride coatings by RF magnetron sputtering on silicon substrates. The film properties were analyzed as a function of oxygen flux percentage in two different inert gas atmospheres namely argon and helium. At low oxygen flux percentage, Zr 2 ON 2 and ZrO 2 phases are observed from the structural characterization by X-ray diffraction. The atomic ratio of nonmetallic to metallic atoms (N + O)/Zr content varies from 1.22 to 2.03 for zirconium oxynitride films deposited in argon atmosphere and from 1.43 to 2.33 for films deposited in helium atmosphere. The thickness of the film was measured by surface profiler and the growth rate decreases from 11.33 to 5.1 nm/min for films deposited in argon atmosphere and from 7.01 to 3.75 nm/min for films deposited in helium atmosphere with increase in oxygen flux percentage. The films deposited are hydrophobic and the contact angle was measured by contact angle measuring system. Higher surface roughness and maximum contact angle values of 100°and 103°are observed for films deposited in argon and helium atmosphere respectively at low oxygen flux percentage (2.5%). The surface energy of films was calculated by two methods: Owens-Wendt's geometric mean and Wu's harmonic mean approach. The elevated surface energy values were observed with increase in oxygen flux percentage. The stress measurements of the deposited films were done by sin 2 ψ X-ray diffraction method which depends on the variation of Zr 2 ON 2 and m-ZrO 2 phases.
With a view to understand the influence of nano size on various properties of cobalt-doped ZnO-ba... more With a view to understand the influence of nano size on various properties of cobalt-doped ZnO-based diluted magnetic semiconductors, a series of materials were prepared by the citrate gel route. The phase and morphology studies have been carried out by X-ray diffraction and transmission electron microscopy, respectively. All the samples of the present investigation are found to have hexagonal wurtzite structure and crystallite sizes are found to vary from 25 nm to 65 nm. From the optical absorption measurements it has been observed that upon doping with cobalt, the energy band gap is found to shift towards lower energy side (red shift) while it shifts towards higher energy side (blue shift) when the crystallite size is increased continuously. It has been observed from the XPS results that oxidation state of Cobalt is +2 and that the difference in binding energies of Co 2p 3/2 and Co 2p 1/2 is found to increase continuously with increasing crystallite size. Finally, all the samples are found to exhibit room temperature ferromagnetism and the specific magnetization decreases with increasing crystallite size.
ABSTRACT The present paper reports the structural and magnetic properties of sputter deposited (S... more ABSTRACT The present paper reports the structural and magnetic properties of sputter deposited (SiO2/Co/Pt/SiO2)n multilayers deposited by magnetron sputtering on quartz substrates as a function of the number of layers (n = 1, 2, 3, 4) and the effect of swift heavy ions (120 MeV Ag9+) irradiation on them. The deposition of multilayers was performed under high vacuum on substrates held at 780 °C. All the deposited films were found to contain stoichiometric (Co50Pt50) particles with L10 ordered structure and their coercivity increases with the increasing number of layers. The formation of L10 ordered structure was evident by the presence of (0 0 1), (1 1 0) super lattice peaks in XRD patterns and from selected area electron diffraction pattern images in TEM. The coercivity of these films was measured using SQUID magnetometer. Irradiation of these films induced an increase in coercivity together with a loss of chemical ordering in the metal phase. However, the easy axis of magnetization remained in the film plane contrary to the case of FePt particles in silica matrix as previously reported.
We report the effect of inert gas (argon and helium) along with different concentrations of oxyge... more We report the effect of inert gas (argon and helium) along with different concentrations of oxygen on the structural and optical properties of the rf magnetron sputtered nanocrystalline tungsten oxide thin films. The crystal structure and surface morphology were studied by X-ray diffraction (XRD) and atomic force microscope (AFM), respectively. We find that the atomic mass of the sputtering gas significantly affects the primary crystallite size as well as the surface morphology and texture. We were able to relate the higher oxidation of the tungsten atoms with low partial pressure of oxygen when films are deposited in helium instead of argon. It was also observed that the bandgap of the WO 3 films increases with increase in the partial pressure of oxygen.
We report on the synthesis of single phase SrS:Ce/quartz thin film nanophosphors at a substrate t... more We report on the synthesis of single phase SrS:Ce/quartz thin film nanophosphors at a substrate temperature of 400 • C using pulsed laser deposition. The AFM and FESEM micrographs reveal the island structure with granular growth of nanophosphors. The average crystallite size (∼ 13 nm using Williamson-Hall plot), the average grain size (∼ 40 nm using AFM) and the blue shift in band gap confirm the nanostructure formation. Interestingly, the photoluminescence emission corresponding to 5d−4f transitions in Ce 3+ ion under the cubic crystal field of SrS also exhibits a significant blue shift, which can be explained using phenomenological crystal field model modified by covalency factor.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, Jan 14, 2015
Surfactants are used to prevent the irreversible aggregation of partially refolded proteins and t... more Surfactants are used to prevent the irreversible aggregation of partially refolded proteins and they also assist in protein refolding. We have reported the design and screening of gemini surfactant to stabilize bovine serum albumin (BSA) with the help of computational tool (iGEMDOCK). A series of gemini surfactant has been designed based on bis-N-alkyl nicotinate dianion via varying the alkyl group and anion. On changing the alkyl group and anion of the surfactant, the value of Log P changes means polarity of surfactant can be tuned. Further, the virtual screening of the gemini surfactant has been carried out based on generic evolutionary method. Herein, thermodynamic data was studied to determine the potential of gemini surfactant as BSA stabilizer. Computational tools help to find out the efficient gemini surfactant to stabilize the BSA rather than to use the surfactant randomly and directionless for the stabilization. It can be confirmed through the experimental techniques. Previously, researcher synthesized one of the designed and used gemini surfactant to stabilize the BSA and their interactions were confirmed through various techniques and computational docking. But herein, the authors find the most competent gemini surfactant to stabilize BSA using computational tools on the basis of energy score. Different from the single chain surfactant, the gemini surfactants exhibit much stronger electrostatic and hydrophobic interactions with the protein and are thus effective at much lower concentrations. Based on the present study, it is expected that gemini surfactants may prove useful in the protein stabilization operations and may thus be effectively employed to circumvent the problem of misfolding and aggregation.
The chromium and titanium oxynitride films on glass substrate were deposited by using reactive RF... more The chromium and titanium oxynitride films on glass substrate were deposited by using reactive RF magnetron sputtering in the present work. The structural and optical properties of the chromium and titanium oxynitride films as a function of power variations are investigated. The chromium oxynitride films are crystalline even at low power of Cr target (≥60 W) but the titanium oxynitride films are amorphous at low target power of Ti target (≤90 W) as observed from glancing incidence X-ray diffraction (GIXRD) patterns. The residual stress and strain of the chromium oxynitride films are calculated by sin2 ψ method, as the average crystallite size decreases with the increase in sputtering power of the Cr target, higher stress and strain values are observed. The chromium oxynitride films changes from hydrophilic to hydrophobic with the increase of contact angle value from 86.4° to 94.1°, but the deposited titanium oxynitride films are hydrophilic as observed from contact angle measurements. The changes in surface energy were calculated using contact angle measurements to substantiate the hydrophobic properties of the films. UV–vis and NIR spectrophotometer were used to obtain the transmission and absorption spectra, and the later was used for determining band gap values of the films, respectively. The refractive index of chromium and titanium oxynitride films increases with film packing density due to formation of crystalline chromium and titanium oxynitride films with the gradual rise in deposition rate as a result of increase in target powers.► Ti-doped chromium oxynitride and Cr-doped titanium oxynitride films at Cr and Ti targets powers. ► Such co-sputtering studies using helium as inert gas is rare in literature. ► This article deals with a systematic study on structural, optical and hydrophobic properties of films. ► The chromium oxynitride films changes from hydrophilic to hydrophobic. ► The surface energy is sensitive to the contact angle and optical properties like n, Eg, %T are tailored.
The thermally stimulated discharge behaviour of vacuum-deposited polyvinyl fluoride films (about ... more The thermally stimulated discharge behaviour of vacuum-deposited polyvinyl fluoride films (about 0022-3727/30/8/014/img7 thick) studied as a function of polarization temperature (313 - 453 K) and polarization field (1 - 0022-3727/30/8/014/img8) shows a single relaxation peak whose peak temperature, charge, activation energy and so on depend strongly on the polarization parameters. The peak has been attributed to space-charge distributed polarization due to the migration of the charge carriers, injected from the electrodes or present inherently, over macroscopic distances and their subsequent trapping; the trapping levels being distributed in the range of energies 0.55 - 0.69 eV.
In this study, we report the synthesis and antibacterial activity of a new series of 5-amido-1-(2... more In this study, we report the synthesis and antibacterial activity of a new series of 5-amido-1-(2,4dinitrophenyl)-1H-4-pyrazolecarbonitriles. Our results show that all compounds exhibit antimicrobial activities against methicillin susceptible Staphylococcus aureus and methicillin resistant S. aureus with MIC values of 25.1 and 91.0 lM.
Catharanthus roseus is a medicinal herb found in many tropical and subtropical regions around the... more Catharanthus roseus is a medicinal herb found in many tropical and subtropical regions around the world. This plant produces a diverse array of secondary metabolites that are pharmaceutically important like vinblastine and vincristine used as chemotherapeutic agents in the treatment of several types of cancers. Low yield of these vinca alkaloids from the plant in vivo and the challenges to meet their high demand worldwide led researchers to develop various in vitro techniques like hairy root culture, callus cultures, shoot cultures, metabolic engineering and regulation studies to increase their production. The present review gives an account of the various phytochemicals derived from the plant and the pharmacological aspects of secondary metabolites studied. Present review also highlights the biotechnological prospects of an efficient and alternative means of production of valuable metabolites from Catharanthus roseus and also from rich microflora residing inside the plant tissues. It gives an emphasis on the need of exploration of diverse niches of endophytes.
... Sci. Technol., B 16 (1998) 1305. 4. A. Costa, S. Camargo Jr., C. Achete, R. Carius, Thin Soli... more ... Sci. Technol., B 16 (1998) 1305. 4. A. Costa, S. Camargo Jr., C. Achete, R. Carius, Thin Solid Films 377-378 (2000) 243. 5. YS Katharria, S. Kumar, F. Singh, JC Pivin, D. Kanjilal, J. Phys., D, Appl. Phys. 39 (2006) 3969, and the refs. therein.
We report on the growth of terbium iron garnet (TbIG, Tb 3 Fe 5 O 12 ) thin films having anomalou... more We report on the growth of terbium iron garnet (TbIG, Tb 3 Fe 5 O 12 ) thin films having anomalously large coercivity and in-plane easy axis of magnetization. The TbIG thin films were prepared at room temperature (RT) on Pt/Si(1 0 0) substrates by pulsed laser deposition technique. The films deposited at RT were X-ray amorphous and do not show any magnetic order. Annealing of the RT deposited film at 900 1C resulted into fully textured (532) TbIG film. Atomic force microscopy and cross-sectional scanning electron microscopy studies of the TbIG films showed good surface quality with an average surface roughness of 5.0 nm and thickness of about 300 nm, respectively. The M-H loops measured at 20 K for TbIG films, exhibit about an order of magnitude enhancement in the coercivity value (H c ) than the single crystal. In-plane and out-of-plane M-H loops revealed that the easy axis of the magnetization lies within the film's plane. In-plane magnetization combining with large H c value of the TbIG thin film may be of scientific interest for the possible applications.
Nanocrystalline powders of cubic (Zn, Cd) S and Zn x Cd 1− x S were synthesized by the chemical p... more Nanocrystalline powders of cubic (Zn, Cd) S and Zn x Cd 1− x S were synthesized by the chemical precipitate method from the aqueous solution of sodium sulphide, zinc nitrate and cadmium nitrate at 277 K without any capping agent. High temperature X-ray diffraction ( ...
The aim of this work is to develop zirconium oxynitride coatings by RF magnetron sputtering on si... more The aim of this work is to develop zirconium oxynitride coatings by RF magnetron sputtering on silicon substrates. The film properties were analyzed as a function of oxygen flux percentage in two different inert gas atmospheres namely argon and helium. At low oxygen flux percentage, Zr 2 ON 2 and ZrO 2 phases are observed from the structural characterization by X-ray diffraction. The atomic ratio of nonmetallic to metallic atoms (N + O)/Zr content varies from 1.22 to 2.03 for zirconium oxynitride films deposited in argon atmosphere and from 1.43 to 2.33 for films deposited in helium atmosphere. The thickness of the film was measured by surface profiler and the growth rate decreases from 11.33 to 5.1 nm/min for films deposited in argon atmosphere and from 7.01 to 3.75 nm/min for films deposited in helium atmosphere with increase in oxygen flux percentage. The films deposited are hydrophobic and the contact angle was measured by contact angle measuring system. Higher surface roughness and maximum contact angle values of 100°and 103°are observed for films deposited in argon and helium atmosphere respectively at low oxygen flux percentage (2.5%). The surface energy of films was calculated by two methods: Owens-Wendt's geometric mean and Wu's harmonic mean approach. The elevated surface energy values were observed with increase in oxygen flux percentage. The stress measurements of the deposited films were done by sin 2 ψ X-ray diffraction method which depends on the variation of Zr 2 ON 2 and m-ZrO 2 phases.
With a view to understand the influence of nano size on various properties of cobalt-doped ZnO-ba... more With a view to understand the influence of nano size on various properties of cobalt-doped ZnO-based diluted magnetic semiconductors, a series of materials were prepared by the citrate gel route. The phase and morphology studies have been carried out by X-ray diffraction and transmission electron microscopy, respectively. All the samples of the present investigation are found to have hexagonal wurtzite structure and crystallite sizes are found to vary from 25 nm to 65 nm. From the optical absorption measurements it has been observed that upon doping with cobalt, the energy band gap is found to shift towards lower energy side (red shift) while it shifts towards higher energy side (blue shift) when the crystallite size is increased continuously. It has been observed from the XPS results that oxidation state of Cobalt is +2 and that the difference in binding energies of Co 2p 3/2 and Co 2p 1/2 is found to increase continuously with increasing crystallite size. Finally, all the samples are found to exhibit room temperature ferromagnetism and the specific magnetization decreases with increasing crystallite size.
ABSTRACT The present paper reports the structural and magnetic properties of sputter deposited (S... more ABSTRACT The present paper reports the structural and magnetic properties of sputter deposited (SiO2/Co/Pt/SiO2)n multilayers deposited by magnetron sputtering on quartz substrates as a function of the number of layers (n = 1, 2, 3, 4) and the effect of swift heavy ions (120 MeV Ag9+) irradiation on them. The deposition of multilayers was performed under high vacuum on substrates held at 780 °C. All the deposited films were found to contain stoichiometric (Co50Pt50) particles with L10 ordered structure and their coercivity increases with the increasing number of layers. The formation of L10 ordered structure was evident by the presence of (0 0 1), (1 1 0) super lattice peaks in XRD patterns and from selected area electron diffraction pattern images in TEM. The coercivity of these films was measured using SQUID magnetometer. Irradiation of these films induced an increase in coercivity together with a loss of chemical ordering in the metal phase. However, the easy axis of magnetization remained in the film plane contrary to the case of FePt particles in silica matrix as previously reported.
We report the effect of inert gas (argon and helium) along with different concentrations of oxyge... more We report the effect of inert gas (argon and helium) along with different concentrations of oxygen on the structural and optical properties of the rf magnetron sputtered nanocrystalline tungsten oxide thin films. The crystal structure and surface morphology were studied by X-ray diffraction (XRD) and atomic force microscope (AFM), respectively. We find that the atomic mass of the sputtering gas significantly affects the primary crystallite size as well as the surface morphology and texture. We were able to relate the higher oxidation of the tungsten atoms with low partial pressure of oxygen when films are deposited in helium instead of argon. It was also observed that the bandgap of the WO 3 films increases with increase in the partial pressure of oxygen.
We report on the synthesis of single phase SrS:Ce/quartz thin film nanophosphors at a substrate t... more We report on the synthesis of single phase SrS:Ce/quartz thin film nanophosphors at a substrate temperature of 400 • C using pulsed laser deposition. The AFM and FESEM micrographs reveal the island structure with granular growth of nanophosphors. The average crystallite size (∼ 13 nm using Williamson-Hall plot), the average grain size (∼ 40 nm using AFM) and the blue shift in band gap confirm the nanostructure formation. Interestingly, the photoluminescence emission corresponding to 5d−4f transitions in Ce 3+ ion under the cubic crystal field of SrS also exhibits a significant blue shift, which can be explained using phenomenological crystal field model modified by covalency factor.
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