In the present study sol gel silica glasses doped with rhodamine dye (Rh6G) and transition metals... more In the present study sol gel silica glasses doped with rhodamine dye (Rh6G) and transition metals like silver, copper and iron were prepared at room temperature through sol gel route. The molar concentrations of dye and metal are varied and synthesized to get a uniform dye and metal doped clusters in silica matrices. Structural characterization is performed by SEM and XRD on doped silica glasses. SEM micrographs reveal the size of particles to be 10-50µm. The amorphous structures of the glasses are confirmed by XRD. The absorption spectra are monitored and analyzed. The absorption spectra of fluorescent dye doped sol gel silica glasses are found within the limit of 400-600 nm and the absorption spectra of different metal doped glasses are in the range of 250-350nm. Oscillator strengths of dye doped and metal doped glasses are calculated and compared. Oscillator strength of rhodamine dye doped silica glasses is comparatively higher than the other doped glasses. Silver is seen to have high oscillator strength among the metal doped silica glasses.
Al and Cu doped ZnO nanoparticles are considered as appropriate for modulation of structural and ... more Al and Cu doped ZnO nanoparticles are considered as appropriate for modulation of structural and optoelectronic properties. Al atoms are found to substitute the host Zn whereas Cu dopants mainly segregate in grain boundaries and thereby determine the optical properties. The undoped as well as Al and Cu doped ZnO exhibit spherical well defined particles. The spherical nanoparticles change to rod type structures on co-doping. The average particle size decreases on doping what consequently results in an increment in band gap. Blue shift in UV absorption is governed by the functional group of glucose; further blue shift occurring on metal doping may be attributed to Burstein-Moss effect. PL spectra of doped and undoped ZnO show a dominant near band gap UV emission along with visible emission owing to the defects. The PL peak intensity increases on doping with Cu and Al. The linear I-V characteristics indicate the ohmic behavior of ZnO nanostructures.
Abstract Oxides of nanosheets are currently drawing much attention for their unique properties an... more Abstract Oxides of nanosheets are currently drawing much attention for their unique properties and wider potential applications. Copper (Cu) doped ZnO/ Zn(OH) 2 nanosheets are synthesised by CBD method in glucose matrix. The structural, optical and electrical properties of the samples are investigated through XRD, HRTEM, UV-Visible, Pl spectroscopy and I-V measurements. XRD shows the formation of hexagonal ZnO along with Zn(OH) 2 traces. Porous, transparent nanosheets having width around 3nm and nanoparticles of average size 2nm-5nm, superlattice structures are found in HRTEM images. Cu dopant may play a key role in bringing such a superlattice structure that enhances the transparency in the sheets. Formation of triangular lamina of Cu doped ZnO/ Zn(OH) 2 nanosheets are confirmed by HRTEM images. EDS spectrum confirms the presence of zinc, oxygen and copper elements in CZO sample. PL spectra yield intense green emission peaks at 522.41nm which can be exploited to fabricate green LED. UV-Visible study shows band gap values as 3.70eV, 3.75eV and 3.78eV particularly for nanosheets with increasing doping concentration of copper in ZnO. The electrical conductivity is found to increase with the doping level. A correlation has been expected between the optoelectronic properties and nanosheets which are governed by superlattice structure.
International journal of scientific research, Sep 1, 2015
Zinc oxide (ZnO) nanoparticles have been synthesised through chemical bath deposition(CBD) method... more Zinc oxide (ZnO) nanoparticles have been synthesised through chemical bath deposition(CBD) method using glucose and poly vinyl alcohol (PVA) respectively as capping agent. The XRD, HRTEM and UV-Visible characterisation techniques were employed. Tauc's plot of PVA capped sample yield direct band gap of 5.72eV. Blue shifting observed in the absorption edge of the UV-Visible spectra confirms quantum confinement. Good crystallinity has been inferred from XRD spectra. In the XRD spectra of PVA capped sample of 0.5M molarity of nano ZnO synthesised at a temperature of 80 0 C. Crystallite size calculated using Scherrer formula was found to be of 2.08nm. HRTEM images show nanocrystals and quantum dots of ZnO.
In this work, a chemical bath deposition (CBD) method was employed for the synthesis of ZnS nanof... more In this work, a chemical bath deposition (CBD) method was employed for the synthesis of ZnS nanofilms. These ZnS nanofilms were grown two dimensionally on a silica glass substrate immersed in a colloidal solution of ZnS nanopartilces. These colloidal ZnS nanoparticles were prepared by mixing equivolume and equimolar (0.5M) solution of zinc sulphate dehydrate and thiourea in the presence of ammonia at room temperature and 3% solution of Poly-Vinyl Alcohol (PVA) was added to it as capping agent. In TEM analyses, the formation of the different size of ZnS nanofilms was observed. XRD analysis showed that sample prepared were the cubic Zinc blende structure with particles’ size in the ranges 5nm -12nm and the measured spacing of crystallographic plane is about 0.27nm. Room-temperature optical absorption spectroscopy exhibits the presence of two separate excitonic characters inferring that the as-prepared ZnS nanostructures have some crystal defects. Due to the simplicity of this synthesi...
In this work, a chemical bath deposition (CBD) method was employed for the synthesis of ZnS nanof... more In this work, a chemical bath deposition (CBD) method was employed for the synthesis of ZnS nanofilms. These ZnS nanofilms were grown two dimensionally on a silica glass substrate immersed in a colloidal solution of ZnS nanopartilces. These colloidal ZnS nanoparticles were prepared by mixing equivolume and equimolar (0.5M) solution of zinc sulphate dehydrate and thiourea in the presence of ammonia at room temperature and 3% solution of Poly-Vinyl Alcohol (PVA) was added to it as capping agent. In TEM analyses, the formation of the different size of ZnS nanofilms was observed. XRD analysis showed that sample prepared were the cubic Zinc blende structure with particles’ size in the ranges 5nm -12nm and the measured spacing of crystallographic plane is about 0.27nm. Room-temperature optical absorption spectroscopy exhibits the presence of two separate excitonic characters inferring that the as-prepared ZnS nanostructures have some crystal defects. Due to the simplicity of this synthesi...
As many as six thermoluminescence (TL) peaks occurring in the range of RT t o 400 "C can be excit... more As many as six thermoluminescence (TL) peaks occurring in the range of RT t o 400 "C can be excited in beryl b y RT X-irradiation. The number of TL peaks as well as the peak temperatures differ in some samples. However these TL peaks occurring in different samples can be correlated to each other. The TL of different specimens of beryl is reported which includes gem quality green beryl, mineral variety as well as synthetic microcrystals grown under different conditions. Six T L peaks occurring a t 70, 113, 160, 215, 267, and 312 "C can be isolated. Thermal activation energies (E) of these peaks calculated by using Chen's general order kinetics equations and the various heating rates method of Hoogenstraaten are found to give consistent results. The frequency factor (8) of the peaks is also calculated. Sechs Thermolumineszenz(TL)-Maxima, die im Bereich zwischen Raumtemperatur (RT) und 400 "C auftreten, konnen in Beryllium durch RT-Rontgenbestrahlung angeregt werden. Sowohl die Zahl der TL-Maxima als auch die Maxima-Temperaturen unterscheiden sich in einigen Proben. Jedoch lassen sich diese Maxima, die in verschiedenen Proben auftreten, miteinander korrelieren. Es wird die T L von verschiedenen Beryllproben mitgeteilt, wobei sowohl die Mineralvarietat griiner gem-Beryll, als auch synthetische Mikrokristalle, die unter verschiedenen Bedingungen geziichtet werden, eingeschlossen sind. SechsTL-Maxima, die bei 70, 113, 160, 215, 267 und 312 "C auftreten, lassen sich isolieren. Die mittels der kinetischen Gleichungen allgemeiner Ordnurg vcn Chen und der Methode unterschiedlicher Heizgeschwindigkeiten van Haogenstraattn berechneten thermischcn Aktivierungsenergien (E) geben konsistente Ergebnisse. Der Freqnenzfaktor (8) der Maxima wird ebenfalls berechnet.
As many as six thermoluminescence (TL) peaks occurring in the range of RT t o 400 "C can be excit... more As many as six thermoluminescence (TL) peaks occurring in the range of RT t o 400 "C can be excited in beryl b y RT X-irradiation. The number of TL peaks as well as the peak temperatures differ in some samples. However these TL peaks occurring in different samples can be correlated to each other. The TL of different specimens of beryl is reported which includes gem quality green beryl, mineral variety as well as synthetic microcrystals grown under different conditions. Six T L peaks occurring a t 70, 113, 160, 215, 267, and 312 "C can be isolated. Thermal activation energies (E) of these peaks calculated by using Chen's general order kinetics equations and the various heating rates method of Hoogenstraaten are found to give consistent results. The frequency factor (8) of the peaks is also calculated. Sechs Thermolumineszenz(TL)-Maxima, die im Bereich zwischen Raumtemperatur (RT) und 400 "C auftreten, konnen in Beryllium durch RT-Rontgenbestrahlung angeregt werden. Sowohl die Zahl der TL-Maxima als auch die Maxima-Temperaturen unterscheiden sich in einigen Proben. Jedoch lassen sich diese Maxima, die in verschiedenen Proben auftreten, miteinander korrelieren. Es wird die T L von verschiedenen Beryllproben mitgeteilt, wobei sowohl die Mineralvarietat griiner gem-Beryll, als auch synthetische Mikrokristalle, die unter verschiedenen Bedingungen geziichtet werden, eingeschlossen sind. SechsTL-Maxima, die bei 70, 113, 160, 215, 267 und 312 "C auftreten, lassen sich isolieren. Die mittels der kinetischen Gleichungen allgemeiner Ordnurg vcn Chen und der Methode unterschiedlicher Heizgeschwindigkeiten van Haogenstraattn berechneten thermischcn Aktivierungsenergien (E) geben konsistente Ergebnisse. Der Freqnenzfaktor (8) der Maxima wird ebenfalls berechnet.
... BY RK GARTIA (a), RANJIT SINGHA (a), and T. SHANKER RAO (b) Department of Physics, Manipur Un... more ... BY RK GARTIA (a), RANJIT SINGHA (a), and T. SHANKER RAO (b) Department of Physics, Manipur University, Imphal 1) (a) and Introduction A12(F,0H)Si04 above RT with suitable excitation has been studied by a number of research workers /1 to 4/. Some of these workers /2 ...
... BY RK GARTIA (a), RANJIT SINGHA (a), and T. SHANKER RAO (b) Department of Physics, Manipur Un... more ... BY RK GARTIA (a), RANJIT SINGHA (a), and T. SHANKER RAO (b) Department of Physics, Manipur University, Imphal 1) (a) and Introduction A12(F,0H)Si04 above RT with suitable excitation has been studied by a number of research workers /1 to 4/. Some of these workers /2 ...
To promote the use of abundant low rank Assam coal resources, it is necessary to understand the e... more To promote the use of abundant low rank Assam coal resources, it is necessary to understand the extent of emission of volatile species from the coals on thermal treatment. As no pyrolysis work seems to be done with most of the coals so far using a green catalyst, ZnO nanoparticles, this study is an attempt to visualize the magnitude of volatile species released from the thermal treatment of Assam coal in nitrogen atmosphere which is a great environmental concern. The evolution of volatile species for the 72 BS sized unblended coal, have been found to be higher than those samples containing varying amounts of ZnO. For 100BS sized coal particles, similar amounts of volatiles from the unblended coal as well as blended coal of (coal : ZnO for100:5 and 100:7.5) have been observed but for 100:10 ratio ZnO blended samples decrease of volaties has been found. Kinetic study reveals that the rate of reaction was initially very fast and then gradually declined. Moreover, the rate constants for...
International journal of scientific research, 2015
Zinc oxide (ZnO) nanoparticles have been synthesised through chemical bath deposition(CBD) method... more Zinc oxide (ZnO) nanoparticles have been synthesised through chemical bath deposition(CBD) method using glucose and poly vinyl alcohol (PVA) respectively as capping agent. The XRD, HRTEM and UV-Visible characterisation techniques were employed. Tauc’s plot of PVA capped sample yield direct band gap of 5.72eV. Blue shifting observed in the absorption edge of the UV-Visible spectra confirms quantum confinement. Good crystallinity has been inferred from XRD spectra. In the XRD spectra of PVA capped sample of 0.5M molarity of nanoZnO synthesised at a temperature of 80 0 C crystallite size calculated using Scherrer formula was found to be of 2.08nm. HRTEM images show nanocrystals and quantum dots of ZnO.
International Journal of Applied Physics and Mathematics, 2012
In the present work ZnS nanoparticles were synthesized by chemical co-precipitation method at roo... more In the present work ZnS nanoparticles were synthesized by chemical co-precipitation method at room temperature. The structural properties of ZnS nanoparticles were determined by XRD (X-ray Diffraction), TEM (Tunneling Electron Microscopy) and their optical properties by UV-Visible and PL (Photoluminescence) analyses. XRD analysis showed that sample prepared were the cubic Zinc blende structure with particles' size in the ranges 5nm -12nm. The TEM analysis revealed the formation of ZnS nanoparticles with almost uniform shape and size. In optical characterization the UV_Visible spectra show a large blue shift. In PL analysis, three strong and board emission bands located at 365nm, 400nm and 425nm have been observed. It is well known that the luminescent peak centered at 365nm could be assigned to the UV-excitonic emission and other peaks attributing to the sulfur vacancy.
AbstractZnS quantum dots have been synthesized via chemical bath deposition (CBD) method. From th... more AbstractZnS quantum dots have been synthesized via chemical bath deposition (CBD) method. From the x-ray diffraction pattern we can observe the structure of ZnS QDs as the zinc-blende structure. TEM image shows the formation of spherical ZnS QDs. According to UV_visible spectra analyses, a large blue shift is observed which can be attributed to quantum confinement effect of the ZnS QDs. In its PL spectra measurement, the dominant emission band at peaks 438 and 521 nm are identified with optical transitions arising from vacancy and interstitial sites for both Zn and S atoms.
International Journal of Innovative Research in Science, Engineering and Technology, 2015
In the present work the synthesis of undoped and Mn- doped ZnO nanoparticles by simple coprecipit... more In the present work the synthesis of undoped and Mn- doped ZnO nanoparticles by simple coprecipitation method is reported. The nanoparticles were characterized by transmission electron microscopy (TEM), Xray diffraction (XRD), UV-Vis spectroscopy and Photoluminescence (PL) spectroscopy for their structural and optical properties. X-ray diffraction data revealed the formation of hexagonal wurtzite phase for both undoped and Mn-doped nanoparticles. The mean crystallite size as obtained by Debye-Scherrer formula for undoped and doped ZnO nanoparticles of different concentrations are 26.64 nm, 21.66 nm, 23.60 nm and 22.31 nm respectively. The broadening in the XRD patterns clearly indicates the presence of very small nanocrystals. A linear decrease in the band gap is observed with increase of doping percentage. The room temperature PL spectra reveal that all the particles have a high purity with perfect crystallinity; however some crystal defects (vacancy, interstitial etc) are also pre...
Undoped and 2wt%, 4wt%, 6wt% Mn doped ZnO nanoparticles were synthesized by using Chemical Co-pre... more Undoped and 2wt%, 4wt%, 6wt% Mn doped ZnO nanoparticles were synthesized by using Chemical Co-precipitation method. X-ray diffraction data revealed the formation of hexagonal wurtzite phase of mean crystallite sizes 26.64 nm, 21.66 nm, 23.60 nm and 22.31 nm respectively obtained by Scherrer formula for undoped and Mn doped ZnO nanoparticles of different concentrations. Thermoluminescence studies of the nanoparticles of the above samples show TL peaks in three regions occurring around 346-361, 404 and 424-428 Kelvin. The thermal activation energy(E) of the peaks calculated by using CGCD technique are found to be 0.54 eV, 0.7eV and 0.83 eV respectively, with the first peak following nearly second order kinetics while the other two follow nearly first order kinetics. This result is in close agreement with those obtained by Chen’s Peak shape method
In this work grain like ZnO naostructures were synthesized by co-precipitation method and the gro... more In this work grain like ZnO naostructures were synthesized by co-precipitation method and the growth of the particles were stabilized using PVA (Poly-Vinyl-Alcohol) as capping agent. The results from X-ray diffraction patterns and TEM image confirmed the formation of grain like ZnO nanostructuctures with particle size of width 150-200nm and length 350nm -500nm which is in agreement with the SEM analysis. Energy dispersive X-ray [EDAX] analysis established that the as-prepared ZnO nanostucturs have no impurity. The room temperature photoluminescence (PL) spectra of the ZnO nanostructures were recorded under the excitation wavelength of 300nm. In PL spectra three strong and board emission bands located around 374nm, 395nm and 535nm have been observed.
In the present study sol gel silica glasses doped with rhodamine dye (Rh6G) and transition metals... more In the present study sol gel silica glasses doped with rhodamine dye (Rh6G) and transition metals like silver, copper and iron were prepared at room temperature through sol gel route. The molar concentrations of dye and metal are varied and synthesized to get a uniform dye and metal doped clusters in silica matrices. Structural characterization is performed by SEM and XRD on doped silica glasses. SEM micrographs reveal the size of particles to be 10-50µm. The amorphous structures of the glasses are confirmed by XRD. The absorption spectra are monitored and analyzed. The absorption spectra of fluorescent dye doped sol gel silica glasses are found within the limit of 400-600 nm and the absorption spectra of different metal doped glasses are in the range of 250-350nm. Oscillator strengths of dye doped and metal doped glasses are calculated and compared. Oscillator strength of rhodamine dye doped silica glasses is comparatively higher than the other doped glasses. Silver is seen to have high oscillator strength among the metal doped silica glasses.
Al and Cu doped ZnO nanoparticles are considered as appropriate for modulation of structural and ... more Al and Cu doped ZnO nanoparticles are considered as appropriate for modulation of structural and optoelectronic properties. Al atoms are found to substitute the host Zn whereas Cu dopants mainly segregate in grain boundaries and thereby determine the optical properties. The undoped as well as Al and Cu doped ZnO exhibit spherical well defined particles. The spherical nanoparticles change to rod type structures on co-doping. The average particle size decreases on doping what consequently results in an increment in band gap. Blue shift in UV absorption is governed by the functional group of glucose; further blue shift occurring on metal doping may be attributed to Burstein-Moss effect. PL spectra of doped and undoped ZnO show a dominant near band gap UV emission along with visible emission owing to the defects. The PL peak intensity increases on doping with Cu and Al. The linear I-V characteristics indicate the ohmic behavior of ZnO nanostructures.
Abstract Oxides of nanosheets are currently drawing much attention for their unique properties an... more Abstract Oxides of nanosheets are currently drawing much attention for their unique properties and wider potential applications. Copper (Cu) doped ZnO/ Zn(OH) 2 nanosheets are synthesised by CBD method in glucose matrix. The structural, optical and electrical properties of the samples are investigated through XRD, HRTEM, UV-Visible, Pl spectroscopy and I-V measurements. XRD shows the formation of hexagonal ZnO along with Zn(OH) 2 traces. Porous, transparent nanosheets having width around 3nm and nanoparticles of average size 2nm-5nm, superlattice structures are found in HRTEM images. Cu dopant may play a key role in bringing such a superlattice structure that enhances the transparency in the sheets. Formation of triangular lamina of Cu doped ZnO/ Zn(OH) 2 nanosheets are confirmed by HRTEM images. EDS spectrum confirms the presence of zinc, oxygen and copper elements in CZO sample. PL spectra yield intense green emission peaks at 522.41nm which can be exploited to fabricate green LED. UV-Visible study shows band gap values as 3.70eV, 3.75eV and 3.78eV particularly for nanosheets with increasing doping concentration of copper in ZnO. The electrical conductivity is found to increase with the doping level. A correlation has been expected between the optoelectronic properties and nanosheets which are governed by superlattice structure.
International journal of scientific research, Sep 1, 2015
Zinc oxide (ZnO) nanoparticles have been synthesised through chemical bath deposition(CBD) method... more Zinc oxide (ZnO) nanoparticles have been synthesised through chemical bath deposition(CBD) method using glucose and poly vinyl alcohol (PVA) respectively as capping agent. The XRD, HRTEM and UV-Visible characterisation techniques were employed. Tauc's plot of PVA capped sample yield direct band gap of 5.72eV. Blue shifting observed in the absorption edge of the UV-Visible spectra confirms quantum confinement. Good crystallinity has been inferred from XRD spectra. In the XRD spectra of PVA capped sample of 0.5M molarity of nano ZnO synthesised at a temperature of 80 0 C. Crystallite size calculated using Scherrer formula was found to be of 2.08nm. HRTEM images show nanocrystals and quantum dots of ZnO.
In this work, a chemical bath deposition (CBD) method was employed for the synthesis of ZnS nanof... more In this work, a chemical bath deposition (CBD) method was employed for the synthesis of ZnS nanofilms. These ZnS nanofilms were grown two dimensionally on a silica glass substrate immersed in a colloidal solution of ZnS nanopartilces. These colloidal ZnS nanoparticles were prepared by mixing equivolume and equimolar (0.5M) solution of zinc sulphate dehydrate and thiourea in the presence of ammonia at room temperature and 3% solution of Poly-Vinyl Alcohol (PVA) was added to it as capping agent. In TEM analyses, the formation of the different size of ZnS nanofilms was observed. XRD analysis showed that sample prepared were the cubic Zinc blende structure with particles’ size in the ranges 5nm -12nm and the measured spacing of crystallographic plane is about 0.27nm. Room-temperature optical absorption spectroscopy exhibits the presence of two separate excitonic characters inferring that the as-prepared ZnS nanostructures have some crystal defects. Due to the simplicity of this synthesi...
In this work, a chemical bath deposition (CBD) method was employed for the synthesis of ZnS nanof... more In this work, a chemical bath deposition (CBD) method was employed for the synthesis of ZnS nanofilms. These ZnS nanofilms were grown two dimensionally on a silica glass substrate immersed in a colloidal solution of ZnS nanopartilces. These colloidal ZnS nanoparticles were prepared by mixing equivolume and equimolar (0.5M) solution of zinc sulphate dehydrate and thiourea in the presence of ammonia at room temperature and 3% solution of Poly-Vinyl Alcohol (PVA) was added to it as capping agent. In TEM analyses, the formation of the different size of ZnS nanofilms was observed. XRD analysis showed that sample prepared were the cubic Zinc blende structure with particles’ size in the ranges 5nm -12nm and the measured spacing of crystallographic plane is about 0.27nm. Room-temperature optical absorption spectroscopy exhibits the presence of two separate excitonic characters inferring that the as-prepared ZnS nanostructures have some crystal defects. Due to the simplicity of this synthesi...
As many as six thermoluminescence (TL) peaks occurring in the range of RT t o 400 "C can be excit... more As many as six thermoluminescence (TL) peaks occurring in the range of RT t o 400 "C can be excited in beryl b y RT X-irradiation. The number of TL peaks as well as the peak temperatures differ in some samples. However these TL peaks occurring in different samples can be correlated to each other. The TL of different specimens of beryl is reported which includes gem quality green beryl, mineral variety as well as synthetic microcrystals grown under different conditions. Six T L peaks occurring a t 70, 113, 160, 215, 267, and 312 "C can be isolated. Thermal activation energies (E) of these peaks calculated by using Chen's general order kinetics equations and the various heating rates method of Hoogenstraaten are found to give consistent results. The frequency factor (8) of the peaks is also calculated. Sechs Thermolumineszenz(TL)-Maxima, die im Bereich zwischen Raumtemperatur (RT) und 400 "C auftreten, konnen in Beryllium durch RT-Rontgenbestrahlung angeregt werden. Sowohl die Zahl der TL-Maxima als auch die Maxima-Temperaturen unterscheiden sich in einigen Proben. Jedoch lassen sich diese Maxima, die in verschiedenen Proben auftreten, miteinander korrelieren. Es wird die T L von verschiedenen Beryllproben mitgeteilt, wobei sowohl die Mineralvarietat griiner gem-Beryll, als auch synthetische Mikrokristalle, die unter verschiedenen Bedingungen geziichtet werden, eingeschlossen sind. SechsTL-Maxima, die bei 70, 113, 160, 215, 267 und 312 "C auftreten, lassen sich isolieren. Die mittels der kinetischen Gleichungen allgemeiner Ordnurg vcn Chen und der Methode unterschiedlicher Heizgeschwindigkeiten van Haogenstraattn berechneten thermischcn Aktivierungsenergien (E) geben konsistente Ergebnisse. Der Freqnenzfaktor (8) der Maxima wird ebenfalls berechnet.
As many as six thermoluminescence (TL) peaks occurring in the range of RT t o 400 "C can be excit... more As many as six thermoluminescence (TL) peaks occurring in the range of RT t o 400 "C can be excited in beryl b y RT X-irradiation. The number of TL peaks as well as the peak temperatures differ in some samples. However these TL peaks occurring in different samples can be correlated to each other. The TL of different specimens of beryl is reported which includes gem quality green beryl, mineral variety as well as synthetic microcrystals grown under different conditions. Six T L peaks occurring a t 70, 113, 160, 215, 267, and 312 "C can be isolated. Thermal activation energies (E) of these peaks calculated by using Chen's general order kinetics equations and the various heating rates method of Hoogenstraaten are found to give consistent results. The frequency factor (8) of the peaks is also calculated. Sechs Thermolumineszenz(TL)-Maxima, die im Bereich zwischen Raumtemperatur (RT) und 400 "C auftreten, konnen in Beryllium durch RT-Rontgenbestrahlung angeregt werden. Sowohl die Zahl der TL-Maxima als auch die Maxima-Temperaturen unterscheiden sich in einigen Proben. Jedoch lassen sich diese Maxima, die in verschiedenen Proben auftreten, miteinander korrelieren. Es wird die T L von verschiedenen Beryllproben mitgeteilt, wobei sowohl die Mineralvarietat griiner gem-Beryll, als auch synthetische Mikrokristalle, die unter verschiedenen Bedingungen geziichtet werden, eingeschlossen sind. SechsTL-Maxima, die bei 70, 113, 160, 215, 267 und 312 "C auftreten, lassen sich isolieren. Die mittels der kinetischen Gleichungen allgemeiner Ordnurg vcn Chen und der Methode unterschiedlicher Heizgeschwindigkeiten van Haogenstraattn berechneten thermischcn Aktivierungsenergien (E) geben konsistente Ergebnisse. Der Freqnenzfaktor (8) der Maxima wird ebenfalls berechnet.
... BY RK GARTIA (a), RANJIT SINGHA (a), and T. SHANKER RAO (b) Department of Physics, Manipur Un... more ... BY RK GARTIA (a), RANJIT SINGHA (a), and T. SHANKER RAO (b) Department of Physics, Manipur University, Imphal 1) (a) and Introduction A12(F,0H)Si04 above RT with suitable excitation has been studied by a number of research workers /1 to 4/. Some of these workers /2 ...
... BY RK GARTIA (a), RANJIT SINGHA (a), and T. SHANKER RAO (b) Department of Physics, Manipur Un... more ... BY RK GARTIA (a), RANJIT SINGHA (a), and T. SHANKER RAO (b) Department of Physics, Manipur University, Imphal 1) (a) and Introduction A12(F,0H)Si04 above RT with suitable excitation has been studied by a number of research workers /1 to 4/. Some of these workers /2 ...
To promote the use of abundant low rank Assam coal resources, it is necessary to understand the e... more To promote the use of abundant low rank Assam coal resources, it is necessary to understand the extent of emission of volatile species from the coals on thermal treatment. As no pyrolysis work seems to be done with most of the coals so far using a green catalyst, ZnO nanoparticles, this study is an attempt to visualize the magnitude of volatile species released from the thermal treatment of Assam coal in nitrogen atmosphere which is a great environmental concern. The evolution of volatile species for the 72 BS sized unblended coal, have been found to be higher than those samples containing varying amounts of ZnO. For 100BS sized coal particles, similar amounts of volatiles from the unblended coal as well as blended coal of (coal : ZnO for100:5 and 100:7.5) have been observed but for 100:10 ratio ZnO blended samples decrease of volaties has been found. Kinetic study reveals that the rate of reaction was initially very fast and then gradually declined. Moreover, the rate constants for...
International journal of scientific research, 2015
Zinc oxide (ZnO) nanoparticles have been synthesised through chemical bath deposition(CBD) method... more Zinc oxide (ZnO) nanoparticles have been synthesised through chemical bath deposition(CBD) method using glucose and poly vinyl alcohol (PVA) respectively as capping agent. The XRD, HRTEM and UV-Visible characterisation techniques were employed. Tauc’s plot of PVA capped sample yield direct band gap of 5.72eV. Blue shifting observed in the absorption edge of the UV-Visible spectra confirms quantum confinement. Good crystallinity has been inferred from XRD spectra. In the XRD spectra of PVA capped sample of 0.5M molarity of nanoZnO synthesised at a temperature of 80 0 C crystallite size calculated using Scherrer formula was found to be of 2.08nm. HRTEM images show nanocrystals and quantum dots of ZnO.
International Journal of Applied Physics and Mathematics, 2012
In the present work ZnS nanoparticles were synthesized by chemical co-precipitation method at roo... more In the present work ZnS nanoparticles were synthesized by chemical co-precipitation method at room temperature. The structural properties of ZnS nanoparticles were determined by XRD (X-ray Diffraction), TEM (Tunneling Electron Microscopy) and their optical properties by UV-Visible and PL (Photoluminescence) analyses. XRD analysis showed that sample prepared were the cubic Zinc blende structure with particles' size in the ranges 5nm -12nm. The TEM analysis revealed the formation of ZnS nanoparticles with almost uniform shape and size. In optical characterization the UV_Visible spectra show a large blue shift. In PL analysis, three strong and board emission bands located at 365nm, 400nm and 425nm have been observed. It is well known that the luminescent peak centered at 365nm could be assigned to the UV-excitonic emission and other peaks attributing to the sulfur vacancy.
AbstractZnS quantum dots have been synthesized via chemical bath deposition (CBD) method. From th... more AbstractZnS quantum dots have been synthesized via chemical bath deposition (CBD) method. From the x-ray diffraction pattern we can observe the structure of ZnS QDs as the zinc-blende structure. TEM image shows the formation of spherical ZnS QDs. According to UV_visible spectra analyses, a large blue shift is observed which can be attributed to quantum confinement effect of the ZnS QDs. In its PL spectra measurement, the dominant emission band at peaks 438 and 521 nm are identified with optical transitions arising from vacancy and interstitial sites for both Zn and S atoms.
International Journal of Innovative Research in Science, Engineering and Technology, 2015
In the present work the synthesis of undoped and Mn- doped ZnO nanoparticles by simple coprecipit... more In the present work the synthesis of undoped and Mn- doped ZnO nanoparticles by simple coprecipitation method is reported. The nanoparticles were characterized by transmission electron microscopy (TEM), Xray diffraction (XRD), UV-Vis spectroscopy and Photoluminescence (PL) spectroscopy for their structural and optical properties. X-ray diffraction data revealed the formation of hexagonal wurtzite phase for both undoped and Mn-doped nanoparticles. The mean crystallite size as obtained by Debye-Scherrer formula for undoped and doped ZnO nanoparticles of different concentrations are 26.64 nm, 21.66 nm, 23.60 nm and 22.31 nm respectively. The broadening in the XRD patterns clearly indicates the presence of very small nanocrystals. A linear decrease in the band gap is observed with increase of doping percentage. The room temperature PL spectra reveal that all the particles have a high purity with perfect crystallinity; however some crystal defects (vacancy, interstitial etc) are also pre...
Undoped and 2wt%, 4wt%, 6wt% Mn doped ZnO nanoparticles were synthesized by using Chemical Co-pre... more Undoped and 2wt%, 4wt%, 6wt% Mn doped ZnO nanoparticles were synthesized by using Chemical Co-precipitation method. X-ray diffraction data revealed the formation of hexagonal wurtzite phase of mean crystallite sizes 26.64 nm, 21.66 nm, 23.60 nm and 22.31 nm respectively obtained by Scherrer formula for undoped and Mn doped ZnO nanoparticles of different concentrations. Thermoluminescence studies of the nanoparticles of the above samples show TL peaks in three regions occurring around 346-361, 404 and 424-428 Kelvin. The thermal activation energy(E) of the peaks calculated by using CGCD technique are found to be 0.54 eV, 0.7eV and 0.83 eV respectively, with the first peak following nearly second order kinetics while the other two follow nearly first order kinetics. This result is in close agreement with those obtained by Chen’s Peak shape method
In this work grain like ZnO naostructures were synthesized by co-precipitation method and the gro... more In this work grain like ZnO naostructures were synthesized by co-precipitation method and the growth of the particles were stabilized using PVA (Poly-Vinyl-Alcohol) as capping agent. The results from X-ray diffraction patterns and TEM image confirmed the formation of grain like ZnO nanostructuctures with particle size of width 150-200nm and length 350nm -500nm which is in agreement with the SEM analysis. Energy dispersive X-ray [EDAX] analysis established that the as-prepared ZnO nanostucturs have no impurity. The room temperature photoluminescence (PL) spectra of the ZnO nanostructures were recorded under the excitation wavelength of 300nm. In PL spectra three strong and board emission bands located around 374nm, 395nm and 535nm have been observed.
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Papers by Ranjit Singha