Ravi Sharma - Academia.edu (original) (raw)
Papers by Ravi Sharma
This paper reports the photoluminescence properties of Ca2MgSi 2 O 7 phosphor with different conc... more This paper reports the photoluminescence properties of Ca2MgSi 2 O 7 phosphor with different concentrations of trivalent cerium Ce, dyposium Dy and divalent Eu as dopant. The phosphor is synthesized using the solid state reaction. Photoluminescence studies is done on the prepared phosphor. For crystal structure and surface morphology SEM micrographs of Ca2MgSi 2 O 7 : Ce, Dy , Eu phosphor were also studied. From SEM confirms the formation of micro phosphor in the range around 100 μm-500μm
Luminescence : the journal of biological and chemical luminescence, Jan 7, 2016
CdSe nanoparticles were synthesized by green route and chemical route methods. In the green route... more CdSe nanoparticles were synthesized by green route and chemical route methods. In the green route method the samples were capped by starch and in the chemical route method the samples were capped by mercaptoacetic acid (MAA). The samples were characterized by powder X- ray diffraction (XRD) and transmission electron microscopy (TEM). Both the samples showed zinc blend structure. The optical absorption spectra and Fourier transform infrared (FTIR) spectra were also studied. A blue shift was seen in the absorption spectra as compared with the bulk as well as the sample capped by starch. TEM images showed agglomeration for the starch-capped sample as compared with the MAA-capped sample. The particle size for the sample capped by MAA was found to be less as compared with the starch-capped sample. A blue shift in the photoluminescence (PL) spectra was also recorded for the samples prepared by the chemical route as compared with the sample prepared by the green route as well as the bulk. ...
Luminescence : the journal of biological and chemical luminescence, Jan 21, 2015
In this paper, europium-doped strontium aluminate (SrAl2 O4 :Eu(2+) ) phosphors were synthesized ... more In this paper, europium-doped strontium aluminate (SrAl2 O4 :Eu(2+) ) phosphors were synthesized using a combustion method with urea as a fuel at 600°C. The phase structure, particle size, surface morphology and elemental analysis were studied using X-ray diffractometry (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and Fourier transform infrared (FTIR) spectra. The EDX and FTIR spectra confirm the elements present in the SrAl2 O4 :Eu(2+) phosphor. The optical properties of SrAl2 O4 :Eu(2+) phosphors were investigated by photoluminescence (PL) and mechanoluminescence (ML). The excitation and emission spectra showed a broad band with peaks at 337 and 515 nm, respectively. The ML intensities of SrAl2 O4 :Eu(2+) phosphor increased proportionally with the increase in the height of the mechanical load, which suggests that this phosphor could be used in stress sensors. The CIE colour chromaticity diagram and ML spectra confirm that the SrAl2 O4 :...
Multi Scale Entropy analysis of the sectoral indices of Indian Stock Market
There has been considerable interest in quantifying the complexity of the time series of price va... more There has been considerable interest in quantifying the complexity of the time series of price variations exhibited by stock markets. Different methods have been developed for this purpose. Traditional entropy based algorithms quantify the regularity of the time series. Entropy increases with disorder, however, an increase in entropy may not always be with increase in dynamic complexity. The traditional algorithms may generate misleading results because the algorithms are based on single time scale .However, the multiscale entropy approach measures the complexity of the system taking into account the multiple time scales. This computational tool can be quite effectively used to quantify the complexity of a given time series. In this paper we study the variation in various sectoral indices of Indian stock market using multiscale entropy analysis (MSE).The sample entropies (SampEn) of different sectoral indices are calculated at different ranges of scales and their MSE profiles are co...
Thermo luminescence of CdS-ZnD Nanophosphers
The present paper reports the synthesis and characterization of undoped ZnS nanophosphor and ZnS ... more The present paper reports the synthesis and characterization of undoped ZnS nanophosphor and ZnS naophosphor doped with different Mn concentrations. Nanophosphors of ZnS and ZnS:Mn were prepared by chemical precipitation method using the solution of zinc chloride, sodium sulphide, manganese chloride and mercaptoethanol was used as the capping agent .The particle size of such nanoparticles were measured using XRD analysis and it is found that the average particle size is of few nm. For Zns nanophosphor only one peak was found whereas two peaks were obtained in the photoluminescence spectra of ZnS:Mn nanoparticles. The dominant peak lies at 593nm and the low intensity peak lies at 424nm. The XRD pattern indicated the growth of the nanoparticles.
Application of Nonlinear Dynamics to Commodity Market and its chaotic Behavior
Optical Properties of Bulk ZnS:Mn and ZnS:Mn Nanoparticles
The present paper reports the chemical route synthesis and characterization of ZnS:Mn nanocrystal... more The present paper reports the chemical route synthesis and characterization of ZnS:Mn nanocrystals with mercaptoethanol (ME) as the capping agent. The particle size of such nanocrystals was measured using XRD and SEM pattern and it was found to be in the range 2nm - 6nm. The absorption spectra showed blue shift for the synthesized samples as compared to bulk. The photoluminescence spectra shows two peaks for the ZnS:Mn nanoparticles. The first peak was at around 420 nm and the second peak was found at 598nm.
Thermoluminescence of Cu doped ZnS nanoparticles
ZnS nanoparticles doped with Cu were synthesized bywet chemical route method at 4°C temperature. ... more ZnS nanoparticles doped with Cu were synthesized bywet chemical route method at 4°C temperature. We have investigated the Thermoluminescence (TL) properties of the undoped ZnS and Cu doped ZnS with increase in Cu concentration from 0.5 millimole to 1.5 millimole and also study for different weight of Sodium Hexa Meta Phosphate (SHMP) capping agent from 2gm to 10gm. The XRD studies indicate that most of the samples are cubic in nature. The broadening of peaks tends to increase with increasing weight of capping agent showing decrease in particle size. The crystalline size computed using Scherer formula is found 2nm to 3nm. Absorption spectra show blue shift with different weight of capping agent. TL glow curve shows a single peak at 543 K temperature. Variation in TL intensity as a function of copper concentration is studied and 1mM is found to be the optimum concentration for TL. The trap parameters namely, activation energy (E), order of kinetics (b) and frequency factor(s) of ZnS: ...
Chalcogenide Letters
School of studies in Physics, Pt. Ravishankar Shukla University, Raipur(C.G.) 492010 ZnS:Mn nanoc... more School of studies in Physics, Pt. Ravishankar Shukla University, Raipur(C.G.) 492010 ZnS:Mn nanocrystals show a high luminescence quantum efficiency, and,therefore,they have potential for their use in several opto-electronic devices The present paper reports the synthesis and characterization of luminescent nanocrystals of manganese doped zinc sulphide ,which were prepared by chemical deposition method using the solution of zinc chloride ,sodium sulphide and manganese chloride, whereas mercaptoethanol was used as an capping agent .The particle size of such nanocrystals was measured using XRD pattern and it is found to be in between 3nm -4nm. The optical absorption spectra of the samples shows the blue-shift with decreasing particle size .. The thermoluminescence (TL) of ZnS:Mn nanoparticles is also reported. The TL intensity increases as the particle size is decreased. The shift in peak position was also seen with decreasing size.The consistency of the size dependence of the TL with...
Luminescence : the journal of biological and chemical luminescence, Jan 5, 2014
Copper-doped zinc sulfide (ZnS:Cu) nanoparticles with varying concentrations of capping agent wer... more Copper-doped zinc sulfide (ZnS:Cu) nanoparticles with varying concentrations of capping agent were prepared using a chemical route technique. These particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy and X-ray diffraction (XRD). Optical absorption studies showed that the absorption edge shifted towards the blue region as the concentration of the capping agent increased. Using effective mass approximation, calculation of the nanoparticle size indicated that effective band gap energy increases with decreasing particle size. The thermoluminescence (TL) properties of sodium hexameta phosphate (SHMP)-passivated ZnS:Cu nanoparticles were investigated after UV irradiation at room temperature. The TL glow curve of capped ZnS:Cu showed variations in TL peak position and intensity with the change in capping agent concentration. The photoluminescence (PL) spectra of ZnS:Cu nanoparticles excited at 254 nm exhibited a broad green emission band pea...
The Open Nanoscience Journal, 2011
Eu doped strontium Aluminate phosphors were synthesized by combustion method using urea as a redu... more Eu doped strontium Aluminate phosphors were synthesized by combustion method using urea as a reducer at initiating temperature of 600 o C. We have investigated the Fracto-Mechanoluminescence (ML) and Thermoluminescence (TL) of SrAl 2 O 4 : Eu. Two peaks have been found in time Vs ML intensity plot. The peak of ML intensity Vs time curve increases with increasing velocity of the piston. The total ML intensity (area below the curve) also increases with impact velocity and attains saturation at higher value of the impact velocity. We have also investigated that the ML intensity is completely recovered by irradiation with ultraviolet light. The TL intensity was recorded for different exposure time with UV light and it was observed that TL intensity is maximum for 15 minute exposure time. We have calculated the trap depth by different methods.
E-Journal of Chemistry, 2010
The present paper reports the synthesis and characterization of luminescent nanocrystals of manga... more The present paper reports the synthesis and characterization of luminescent nanocrystals of manganese doped zinc sulphide. Nanocrystals of zinc sulphide were prepared by chemical precipitation method using the solution of zinc chloride, sodium sulphide, manganese chloride and mercaptoethanol was used as the capping agent. It was found that change in the molar concentration changes the particle size. The particle size of such nanocrystals was measured using XRD pattern and it is found to be in between 3 nm – 5 nm. The blue-shift in absorption spectra was found with reducing size of the nanoparticles
Chemical route synthesis dependent particle size of Mn activated ZnS nanophosphors
International Journal of Nanoparticles, 2011
... Lett., Vol. 63, p.2349. Nikesh, VV, Lad, AD, Kimaru, S., Nozaki, S. and Mahamuni, S. (2006) J... more ... Lett., Vol. 63, p.2349. Nikesh, VV, Lad, AD, Kimaru, S., Nozaki, S. and Mahamuni, S. (2006) J. Appl. Phys., Vol. ... Shionoya, S. and Yen, WM (1999) Phosphor Handbook, CRC Press, Boca Raton, FL. Singh, K., Verma, NK and Bhatti, HS (2009) Physica B, Vol. 404, p.300. ...
Research on Chemical Intermediates, 2014
Sr 2 MgSi 2 O 7 :Eu 2? , Dy 3? and Ca 2 MgSi 2 O 7 :Eu 2? , Dy 3? phosphors were synthesized by t... more Sr 2 MgSi 2 O 7 :Eu 2? , Dy 3? and Ca 2 MgSi 2 O 7 :Eu 2? , Dy 3? phosphors were synthesized by the high-temperature solid-state reaction method. The phase structure of the prepared phosphors was of akermanite type, which belongs to the tetragonal crystallography. The EDX and FTIR spectra confirm the presence of elements in prepared phosphors. Sr 2 MgSi 2 O 7 :Eu 2? , Dy 3? and Ca 2 MgSi 2 O 7 :Eu 2? , Dy 3? phosphors would emit blue and green light; the main emission peaks that appeared at 465 and 535 nm belong to the broad emission band ascribed to the 4f 6 5d 1 ? 4f 7 transition. Decay graph indicates that both the phosphors have fast decay and slow decay. Investigation into afterglow property showed that the Sr 2-MgSi 2 O 7 :Eu 2? , Dy 3? phosphor held better afterglow property than Ca 2 MgSi 2 O 7 :-Eu 2? , Dy 3? phosphors. ML measurements showed a linear increase in the ML intensity with the impact velocity of the moving piston.
Arxiv preprint arXiv: …, 2011
Abstract: The conventional economic approaches explore very little about the dynamics of the econ... more Abstract: The conventional economic approaches explore very little about the dynamics of the economic systems. Since such systems consist of a large number of agents interacting nonlinearly they exhibit the properties of a complex system. Therefore the tools of ...
phys.sinica.edu.tw
Traditional entropy based algorithms used in the analysis of time series data quantify the regula... more Traditional entropy based algorithms used in the analysis of time series data quantify the regularity of the time series. But there is no straight forward correspondence between regularity and complexity. Neither completely predictable (e.g. periodic) signal, which have minimum entropy, nor completely unpredictable (e.g. uncorrelated random) signals which have maximum entropy, are truly complex, since they can be described very compactly. Entropy increases with disorder, however, an increase in entropy may not always be associated be with increase in dynamic complexity. Thus the traditional algorithms may generate misleading results because the algorithms are based on single time scale .However, the multiscale entropy (MSE) approach measures the complexity of the system taking into account the multiple time scales. This computational tool can be quite effectively used to quantify the complexity of a given time series. In this paper the behavior of Indian stock market index NIFTY is studied using MSE approach and it is shown that the market exhibits different MSE patterns at different level of information received. However this difference in MSE profile disappears when the time scale is increased. Since the complexity of the market changes with information this approach can be used to verify the applicability of Efficient Market Hypothesis(EMH) and to test the time scales above (below) which market behave efficiently(inefficiently).
Study of scaling behavior of NIFTY using detrended fluctuation analysis
phys.sinica.edu.tw
1 Arts & Commerce Girls College Devendranagar, Raipur,(CG) 492001, India Email - rvsharma65@gmail... more 1 Arts & Commerce Girls College Devendranagar, Raipur,(CG) 492001, India Email - rvsharma65@gmail.com 2 Department of Physics and Computer science, Govt.Science College Raipur 492010 India Email - sharma_balgopal@rediffmail.com 3 School of studies in ...
chalcogen.infim.ro
This paper reports the synthesis of. ZnS:Mn nanocrystals using chemical route; in which mercaptoe... more This paper reports the synthesis of. ZnS:Mn nanocrystals using chemical route; in which mercaptoethanol was used as the capping agent. The particle size of such nanocrystals was measured using XRD and TEM patterns and was found to be in between 3nm-5nm. When a ZnS:Mn nanocrystal are deformed impulsively by applying a load from a fixed height, then initially the ML intensity increases with time, attains a peak value I m at a particular time t m , and later on it decreases with time. The peak intensity I m increases linearly with the increasing height of the load. After t m, initially the ML intensity decreases at a fast rate, and later on it decreases at a slow rate. The ML in ZnS:Mn nanocrystals can be understood on the basis of the piezoelectrically-induced electron detrapping model, in which the local piezoelectric field near the Mn 2+ centres reduces the trap-depth, and therefore, the detrapping of filled electron traps takes place, and subsequently the energy released non-radiatively during the electron-hole recombination excites the Mn 2+ centres and de-excitation gives rise to the ML.
Luminescence, 2014
The thermoluminescence (TL) of nanoparticles has become a matter of keen interest in recent times... more The thermoluminescence (TL) of nanoparticles has become a matter of keen interest in recent times but is rarely reported. This article reports the synthesis of ZnS:Mn nanocrystals using a chemical route, with mercaptoethanol (ME) as the capping agent. The particle sizes for the nanocrystals were measured by X-ray diffraction (XRD) and also by studying transmission electron microscopy (TEM) patterns. The particle sizes of the synthesized samples were found to be between 1 and 3 nm. For samples with different concentrations of the capping agent, it was found that the TL intensity of the ZnS: Mn nanoparticles increased as the particle size decreased. A shift in the peak position of the TL glow curve was also seen with decreasing particle size. The TL intensity was found to be maximal for samples with 1.2% of Mn. A change in the peak position was not found for samples with different concentrations of Mn. The half-width glow peak curve method was used to determine the trap-depth. The frequency factor of the synthesized samples was also calculated. The stability of the charge carriers in the traps increases with decreasing nanoparticle size. The higher stability may be attributed to the higher surface/volume ratio and also to the increase in the trap-depth with decreasing particle size.
Journal of Luminescence, 2011
Rare earth ions play an important role in modern technology as optically active elements in solid... more Rare earth ions play an important role in modern technology as optically active elements in solid-state luminescent materials. In many of these materials, interactions between the electronic band states of the host crystal and the rare earth ion's localized 4f N and 4f N-1 5d states influence the optical properties of materials. This paper reports the mechanoluminescence (ML) induced by impulsive excitation and thermoluminescence (TL) of Ȗ-irradiated dysprosium doped NaCl single crystals and powder. The NaCl crystals having different concentrations of dysprosium were prepared by melt technique (slow cooling).The crystals of small sizes were cleaved from grown crystal block and crushed to obtain microcrystalline powder. The annealed samples were irradiated by gamma source with dose rate of 0.50 kGy/h. Mechanoluminescence is excited impulsively by dropping a load of 0.4 kg with impact velocity 313 cm/s onto it. Two peaks are observed in the ML intensity versus time curves for both single crystals and powder samples. In thermoluminescence of NaCl: Dy crystals and powder samples only one peak is observed in the glow curve at around 210-230°C. In the ML spectra, a broad band with single peak at 482 nm is obtained. The ML and TL intensities of single crystals are compared with the microcrystalline powder of the same mass in the present investigation. The total TL intensity obtained is more in microcrystalline powder than single crystal and reverse intensity yield is obtained in the ML process.
This paper reports the photoluminescence properties of Ca2MgSi 2 O 7 phosphor with different conc... more This paper reports the photoluminescence properties of Ca2MgSi 2 O 7 phosphor with different concentrations of trivalent cerium Ce, dyposium Dy and divalent Eu as dopant. The phosphor is synthesized using the solid state reaction. Photoluminescence studies is done on the prepared phosphor. For crystal structure and surface morphology SEM micrographs of Ca2MgSi 2 O 7 : Ce, Dy , Eu phosphor were also studied. From SEM confirms the formation of micro phosphor in the range around 100 μm-500μm
Luminescence : the journal of biological and chemical luminescence, Jan 7, 2016
CdSe nanoparticles were synthesized by green route and chemical route methods. In the green route... more CdSe nanoparticles were synthesized by green route and chemical route methods. In the green route method the samples were capped by starch and in the chemical route method the samples were capped by mercaptoacetic acid (MAA). The samples were characterized by powder X- ray diffraction (XRD) and transmission electron microscopy (TEM). Both the samples showed zinc blend structure. The optical absorption spectra and Fourier transform infrared (FTIR) spectra were also studied. A blue shift was seen in the absorption spectra as compared with the bulk as well as the sample capped by starch. TEM images showed agglomeration for the starch-capped sample as compared with the MAA-capped sample. The particle size for the sample capped by MAA was found to be less as compared with the starch-capped sample. A blue shift in the photoluminescence (PL) spectra was also recorded for the samples prepared by the chemical route as compared with the sample prepared by the green route as well as the bulk. ...
Luminescence : the journal of biological and chemical luminescence, Jan 21, 2015
In this paper, europium-doped strontium aluminate (SrAl2 O4 :Eu(2+) ) phosphors were synthesized ... more In this paper, europium-doped strontium aluminate (SrAl2 O4 :Eu(2+) ) phosphors were synthesized using a combustion method with urea as a fuel at 600°C. The phase structure, particle size, surface morphology and elemental analysis were studied using X-ray diffractometry (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and Fourier transform infrared (FTIR) spectra. The EDX and FTIR spectra confirm the elements present in the SrAl2 O4 :Eu(2+) phosphor. The optical properties of SrAl2 O4 :Eu(2+) phosphors were investigated by photoluminescence (PL) and mechanoluminescence (ML). The excitation and emission spectra showed a broad band with peaks at 337 and 515 nm, respectively. The ML intensities of SrAl2 O4 :Eu(2+) phosphor increased proportionally with the increase in the height of the mechanical load, which suggests that this phosphor could be used in stress sensors. The CIE colour chromaticity diagram and ML spectra confirm that the SrAl2 O4 :...
Multi Scale Entropy analysis of the sectoral indices of Indian Stock Market
There has been considerable interest in quantifying the complexity of the time series of price va... more There has been considerable interest in quantifying the complexity of the time series of price variations exhibited by stock markets. Different methods have been developed for this purpose. Traditional entropy based algorithms quantify the regularity of the time series. Entropy increases with disorder, however, an increase in entropy may not always be with increase in dynamic complexity. The traditional algorithms may generate misleading results because the algorithms are based on single time scale .However, the multiscale entropy approach measures the complexity of the system taking into account the multiple time scales. This computational tool can be quite effectively used to quantify the complexity of a given time series. In this paper we study the variation in various sectoral indices of Indian stock market using multiscale entropy analysis (MSE).The sample entropies (SampEn) of different sectoral indices are calculated at different ranges of scales and their MSE profiles are co...
Thermo luminescence of CdS-ZnD Nanophosphers
The present paper reports the synthesis and characterization of undoped ZnS nanophosphor and ZnS ... more The present paper reports the synthesis and characterization of undoped ZnS nanophosphor and ZnS naophosphor doped with different Mn concentrations. Nanophosphors of ZnS and ZnS:Mn were prepared by chemical precipitation method using the solution of zinc chloride, sodium sulphide, manganese chloride and mercaptoethanol was used as the capping agent .The particle size of such nanoparticles were measured using XRD analysis and it is found that the average particle size is of few nm. For Zns nanophosphor only one peak was found whereas two peaks were obtained in the photoluminescence spectra of ZnS:Mn nanoparticles. The dominant peak lies at 593nm and the low intensity peak lies at 424nm. The XRD pattern indicated the growth of the nanoparticles.
Application of Nonlinear Dynamics to Commodity Market and its chaotic Behavior
Optical Properties of Bulk ZnS:Mn and ZnS:Mn Nanoparticles
The present paper reports the chemical route synthesis and characterization of ZnS:Mn nanocrystal... more The present paper reports the chemical route synthesis and characterization of ZnS:Mn nanocrystals with mercaptoethanol (ME) as the capping agent. The particle size of such nanocrystals was measured using XRD and SEM pattern and it was found to be in the range 2nm - 6nm. The absorption spectra showed blue shift for the synthesized samples as compared to bulk. The photoluminescence spectra shows two peaks for the ZnS:Mn nanoparticles. The first peak was at around 420 nm and the second peak was found at 598nm.
Thermoluminescence of Cu doped ZnS nanoparticles
ZnS nanoparticles doped with Cu were synthesized bywet chemical route method at 4°C temperature. ... more ZnS nanoparticles doped with Cu were synthesized bywet chemical route method at 4°C temperature. We have investigated the Thermoluminescence (TL) properties of the undoped ZnS and Cu doped ZnS with increase in Cu concentration from 0.5 millimole to 1.5 millimole and also study for different weight of Sodium Hexa Meta Phosphate (SHMP) capping agent from 2gm to 10gm. The XRD studies indicate that most of the samples are cubic in nature. The broadening of peaks tends to increase with increasing weight of capping agent showing decrease in particle size. The crystalline size computed using Scherer formula is found 2nm to 3nm. Absorption spectra show blue shift with different weight of capping agent. TL glow curve shows a single peak at 543 K temperature. Variation in TL intensity as a function of copper concentration is studied and 1mM is found to be the optimum concentration for TL. The trap parameters namely, activation energy (E), order of kinetics (b) and frequency factor(s) of ZnS: ...
Chalcogenide Letters
School of studies in Physics, Pt. Ravishankar Shukla University, Raipur(C.G.) 492010 ZnS:Mn nanoc... more School of studies in Physics, Pt. Ravishankar Shukla University, Raipur(C.G.) 492010 ZnS:Mn nanocrystals show a high luminescence quantum efficiency, and,therefore,they have potential for their use in several opto-electronic devices The present paper reports the synthesis and characterization of luminescent nanocrystals of manganese doped zinc sulphide ,which were prepared by chemical deposition method using the solution of zinc chloride ,sodium sulphide and manganese chloride, whereas mercaptoethanol was used as an capping agent .The particle size of such nanocrystals was measured using XRD pattern and it is found to be in between 3nm -4nm. The optical absorption spectra of the samples shows the blue-shift with decreasing particle size .. The thermoluminescence (TL) of ZnS:Mn nanoparticles is also reported. The TL intensity increases as the particle size is decreased. The shift in peak position was also seen with decreasing size.The consistency of the size dependence of the TL with...
Luminescence : the journal of biological and chemical luminescence, Jan 5, 2014
Copper-doped zinc sulfide (ZnS:Cu) nanoparticles with varying concentrations of capping agent wer... more Copper-doped zinc sulfide (ZnS:Cu) nanoparticles with varying concentrations of capping agent were prepared using a chemical route technique. These particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy and X-ray diffraction (XRD). Optical absorption studies showed that the absorption edge shifted towards the blue region as the concentration of the capping agent increased. Using effective mass approximation, calculation of the nanoparticle size indicated that effective band gap energy increases with decreasing particle size. The thermoluminescence (TL) properties of sodium hexameta phosphate (SHMP)-passivated ZnS:Cu nanoparticles were investigated after UV irradiation at room temperature. The TL glow curve of capped ZnS:Cu showed variations in TL peak position and intensity with the change in capping agent concentration. The photoluminescence (PL) spectra of ZnS:Cu nanoparticles excited at 254 nm exhibited a broad green emission band pea...
The Open Nanoscience Journal, 2011
Eu doped strontium Aluminate phosphors were synthesized by combustion method using urea as a redu... more Eu doped strontium Aluminate phosphors were synthesized by combustion method using urea as a reducer at initiating temperature of 600 o C. We have investigated the Fracto-Mechanoluminescence (ML) and Thermoluminescence (TL) of SrAl 2 O 4 : Eu. Two peaks have been found in time Vs ML intensity plot. The peak of ML intensity Vs time curve increases with increasing velocity of the piston. The total ML intensity (area below the curve) also increases with impact velocity and attains saturation at higher value of the impact velocity. We have also investigated that the ML intensity is completely recovered by irradiation with ultraviolet light. The TL intensity was recorded for different exposure time with UV light and it was observed that TL intensity is maximum for 15 minute exposure time. We have calculated the trap depth by different methods.
E-Journal of Chemistry, 2010
The present paper reports the synthesis and characterization of luminescent nanocrystals of manga... more The present paper reports the synthesis and characterization of luminescent nanocrystals of manganese doped zinc sulphide. Nanocrystals of zinc sulphide were prepared by chemical precipitation method using the solution of zinc chloride, sodium sulphide, manganese chloride and mercaptoethanol was used as the capping agent. It was found that change in the molar concentration changes the particle size. The particle size of such nanocrystals was measured using XRD pattern and it is found to be in between 3 nm – 5 nm. The blue-shift in absorption spectra was found with reducing size of the nanoparticles
Chemical route synthesis dependent particle size of Mn activated ZnS nanophosphors
International Journal of Nanoparticles, 2011
... Lett., Vol. 63, p.2349. Nikesh, VV, Lad, AD, Kimaru, S., Nozaki, S. and Mahamuni, S. (2006) J... more ... Lett., Vol. 63, p.2349. Nikesh, VV, Lad, AD, Kimaru, S., Nozaki, S. and Mahamuni, S. (2006) J. Appl. Phys., Vol. ... Shionoya, S. and Yen, WM (1999) Phosphor Handbook, CRC Press, Boca Raton, FL. Singh, K., Verma, NK and Bhatti, HS (2009) Physica B, Vol. 404, p.300. ...
Research on Chemical Intermediates, 2014
Sr 2 MgSi 2 O 7 :Eu 2? , Dy 3? and Ca 2 MgSi 2 O 7 :Eu 2? , Dy 3? phosphors were synthesized by t... more Sr 2 MgSi 2 O 7 :Eu 2? , Dy 3? and Ca 2 MgSi 2 O 7 :Eu 2? , Dy 3? phosphors were synthesized by the high-temperature solid-state reaction method. The phase structure of the prepared phosphors was of akermanite type, which belongs to the tetragonal crystallography. The EDX and FTIR spectra confirm the presence of elements in prepared phosphors. Sr 2 MgSi 2 O 7 :Eu 2? , Dy 3? and Ca 2 MgSi 2 O 7 :Eu 2? , Dy 3? phosphors would emit blue and green light; the main emission peaks that appeared at 465 and 535 nm belong to the broad emission band ascribed to the 4f 6 5d 1 ? 4f 7 transition. Decay graph indicates that both the phosphors have fast decay and slow decay. Investigation into afterglow property showed that the Sr 2-MgSi 2 O 7 :Eu 2? , Dy 3? phosphor held better afterglow property than Ca 2 MgSi 2 O 7 :-Eu 2? , Dy 3? phosphors. ML measurements showed a linear increase in the ML intensity with the impact velocity of the moving piston.
Arxiv preprint arXiv: …, 2011
Abstract: The conventional economic approaches explore very little about the dynamics of the econ... more Abstract: The conventional economic approaches explore very little about the dynamics of the economic systems. Since such systems consist of a large number of agents interacting nonlinearly they exhibit the properties of a complex system. Therefore the tools of ...
phys.sinica.edu.tw
Traditional entropy based algorithms used in the analysis of time series data quantify the regula... more Traditional entropy based algorithms used in the analysis of time series data quantify the regularity of the time series. But there is no straight forward correspondence between regularity and complexity. Neither completely predictable (e.g. periodic) signal, which have minimum entropy, nor completely unpredictable (e.g. uncorrelated random) signals which have maximum entropy, are truly complex, since they can be described very compactly. Entropy increases with disorder, however, an increase in entropy may not always be associated be with increase in dynamic complexity. Thus the traditional algorithms may generate misleading results because the algorithms are based on single time scale .However, the multiscale entropy (MSE) approach measures the complexity of the system taking into account the multiple time scales. This computational tool can be quite effectively used to quantify the complexity of a given time series. In this paper the behavior of Indian stock market index NIFTY is studied using MSE approach and it is shown that the market exhibits different MSE patterns at different level of information received. However this difference in MSE profile disappears when the time scale is increased. Since the complexity of the market changes with information this approach can be used to verify the applicability of Efficient Market Hypothesis(EMH) and to test the time scales above (below) which market behave efficiently(inefficiently).
Study of scaling behavior of NIFTY using detrended fluctuation analysis
phys.sinica.edu.tw
1 Arts & Commerce Girls College Devendranagar, Raipur,(CG) 492001, India Email - rvsharma65@gmail... more 1 Arts & Commerce Girls College Devendranagar, Raipur,(CG) 492001, India Email - rvsharma65@gmail.com 2 Department of Physics and Computer science, Govt.Science College Raipur 492010 India Email - sharma_balgopal@rediffmail.com 3 School of studies in ...
chalcogen.infim.ro
This paper reports the synthesis of. ZnS:Mn nanocrystals using chemical route; in which mercaptoe... more This paper reports the synthesis of. ZnS:Mn nanocrystals using chemical route; in which mercaptoethanol was used as the capping agent. The particle size of such nanocrystals was measured using XRD and TEM patterns and was found to be in between 3nm-5nm. When a ZnS:Mn nanocrystal are deformed impulsively by applying a load from a fixed height, then initially the ML intensity increases with time, attains a peak value I m at a particular time t m , and later on it decreases with time. The peak intensity I m increases linearly with the increasing height of the load. After t m, initially the ML intensity decreases at a fast rate, and later on it decreases at a slow rate. The ML in ZnS:Mn nanocrystals can be understood on the basis of the piezoelectrically-induced electron detrapping model, in which the local piezoelectric field near the Mn 2+ centres reduces the trap-depth, and therefore, the detrapping of filled electron traps takes place, and subsequently the energy released non-radiatively during the electron-hole recombination excites the Mn 2+ centres and de-excitation gives rise to the ML.
Luminescence, 2014
The thermoluminescence (TL) of nanoparticles has become a matter of keen interest in recent times... more The thermoluminescence (TL) of nanoparticles has become a matter of keen interest in recent times but is rarely reported. This article reports the synthesis of ZnS:Mn nanocrystals using a chemical route, with mercaptoethanol (ME) as the capping agent. The particle sizes for the nanocrystals were measured by X-ray diffraction (XRD) and also by studying transmission electron microscopy (TEM) patterns. The particle sizes of the synthesized samples were found to be between 1 and 3 nm. For samples with different concentrations of the capping agent, it was found that the TL intensity of the ZnS: Mn nanoparticles increased as the particle size decreased. A shift in the peak position of the TL glow curve was also seen with decreasing particle size. The TL intensity was found to be maximal for samples with 1.2% of Mn. A change in the peak position was not found for samples with different concentrations of Mn. The half-width glow peak curve method was used to determine the trap-depth. The frequency factor of the synthesized samples was also calculated. The stability of the charge carriers in the traps increases with decreasing nanoparticle size. The higher stability may be attributed to the higher surface/volume ratio and also to the increase in the trap-depth with decreasing particle size.
Journal of Luminescence, 2011
Rare earth ions play an important role in modern technology as optically active elements in solid... more Rare earth ions play an important role in modern technology as optically active elements in solid-state luminescent materials. In many of these materials, interactions between the electronic band states of the host crystal and the rare earth ion's localized 4f N and 4f N-1 5d states influence the optical properties of materials. This paper reports the mechanoluminescence (ML) induced by impulsive excitation and thermoluminescence (TL) of Ȗ-irradiated dysprosium doped NaCl single crystals and powder. The NaCl crystals having different concentrations of dysprosium were prepared by melt technique (slow cooling).The crystals of small sizes were cleaved from grown crystal block and crushed to obtain microcrystalline powder. The annealed samples were irradiated by gamma source with dose rate of 0.50 kGy/h. Mechanoluminescence is excited impulsively by dropping a load of 0.4 kg with impact velocity 313 cm/s onto it. Two peaks are observed in the ML intensity versus time curves for both single crystals and powder samples. In thermoluminescence of NaCl: Dy crystals and powder samples only one peak is observed in the glow curve at around 210-230°C. In the ML spectra, a broad band with single peak at 482 nm is obtained. The ML and TL intensities of single crystals are compared with the microcrystalline powder of the same mass in the present investigation. The total TL intensity obtained is more in microcrystalline powder than single crystal and reverse intensity yield is obtained in the ML process.