Abhijit Jadhav - Academia.edu (original) (raw)

Papers by Abhijit Jadhav

Current Applied Physics, 2016

Abstract A phosphor with higher emission efficiency in the visible region can be very helpful in ... more Abstract A phosphor with higher emission efficiency in the visible region can be very helpful in various optoelectronics applications such as solar cells. Effective conversion of UV and NIR radiations to more useful visible and red emissions were carried out through Gd 2 O 3 :Er 3+ nanostructures synthesized by conventional co-precipitation method. The spectroscopic study of Gd 2 O 3 :Er 3+ samples were carried out as a function of dopant concentration under the excitation wavelengths of 378, 975 and 1540 nm, respectively. The doping of erbium show downconversion emission at 561 and 660 nm under 378 nm excitation while upconversion emission under 975 and 1540 nm excitations shows upconversion of NIR photons to 561 and 660 nm visible emissions. The enhanced red emission (660 nm) at higher erbium concentration was observed due to the dominant cross-relaxation processes. The efficiency of upconversion luminescence is highly dependent on the various relaxation and energy transfer processes involved in different energy levels of erbium. The intensity of downconversion and upconversion emission was enhanced by lithium co-doping in Gd 2 O 3 :Er 3+ nanostructures. The incorporation of alkali metal ions in Gd 2 O 3 :Er 3+ shows considerable enhancement in downconversion and upconversion emission intensity making the phosphor more suitable for optoelectronic applications.

Science of Advanced Materials, 2012

Journal of Luminescence, 2015

Well-dispersed Eu-doped CaMgSi 2 O 6 (CMS) nanophosphors of 4-16 nm size range were synthesized b... more Well-dispersed Eu-doped CaMgSi 2 O 6 (CMS) nanophosphors of 4-16 nm size range were synthesized by a simple co-precipitation method followed by thermal annealing in controlled ambient. Emission behaviors of the nanophosphors have been studied to optimize and tune their emissions in desired spectral range (red, blue or both). Effects of temperature and calcination atmosphere on the interconversion (Eu 3 þ 2Eu 2 þ) ability of europium ions in CMS matrix have been studied thoroughly. It has been observed that by calcinating the nanophosphors in oxidizing atmosphere like O 2 , about 70% of the incorporated europium atoms can be transformed to their trivalent (Eu 3 þ) state. On the other hand, calcinating the nanophosphors in reducing atmosphere like H 2 þ N 2 mixture, about 99% of Eu ions can be transformed to their divalent state (Eu 2 þ). It has been demonstrated that by controlling the temperature and ambient of calcination, a dual emitting CMS:Eu nanophosphor could be converted either to blue or red emitting nanophosphor of high emission efficiency. The interchangeable emission characteristic of the size controlled nanophosphor is expected to have immense impact in the fabrication of highly efficient luminescent and display devices.

ChemInform, 2014

The properties of magnetic material of Nd-Fe-B are highly affected by various factors such as par... more The properties of magnetic material of Nd-Fe-B are highly affected by various factors such as particle size, magnetic anisotropy, phase purity and crystal structure. Incorporation of excess neodymium was carried out in various percentages so that it will adjust the proportion of neodymium in the host crystal after reduction treatment and finally help to improve magnetic property of a material. The interdiffusion of Nd-Fe and boron was studied for various compositions and their effect on magnetic property was understood with theoretical concepts. The factors such as amount of hard and soft phase in the reduction treated product is also responsible for the possible exchange coupling between hard and soft phase magnets for better magnetic properties.

Polymer International, 2012

Nanocomposites are a new class of polymeric materials which include organic or inorganic nano-pha... more Nanocomposites are a new class of polymeric materials which include organic or inorganic nano-phase materials. These nanocomposite films can show interesting properties which have many applications for wavelength conversion and energy saving. In this paper, we present polyolefin based nanocomposite films prepared using wavelength-converting red 'phosphors' such as Y 2 O 3 : Eu 3+ and LiAl 5 O 8 :Fe 3+ and blue 'phosphor' CaMgSi 2 O 6 : Eu 2+. The durability of the polymer chain is unaffected by incorporation of inorganic nanoparticles as there is no direct interaction between them. The addition of surfactant in the nanocomposite film helps to improve the dispersion ability of the nanoparticles and increase the flexibility of the polymer film. Wavelength-converting 'nanophosphors' incorporated in a polymer matrix help to increase the tensile strength of the film. The films show excellent wavelength conversion ability of UV light into the visible and near IR range. These nanocomposite films have great application in energy saving devices.

Thin Solid Films, 2012

Cu and Cu 2 O films can be prepared on indium-doped tin oxide glass substrates by simple electrod... more Cu and Cu 2 O films can be prepared on indium-doped tin oxide glass substrates by simple electrodeposition in a solution containing 0.1 M Cu(NO 3) 2 and 3 M lactic acid at different pH values. At low pH (pH=1.2), the uniform Cu films were obtained; when pH≥ 7, the pure Cu 2 O films can be deposited. Especially, at pH=11, the deposited Cu 2 O films exhibited cubic surface morphology exposing mainly {100} plane; in contrast, the films consisting of semi-spherical particles were obtained when the solution was being stirred for 2 weeks prior to use. The possible growth process and mechanism were comparatively discussed.

The Journal of Physical Chemistry C, 2009

Nanoparticles of europium-doped yttrium oxide (Y 2 O 3 :Eu 3+) were synthesized by coprecipitatio... more Nanoparticles of europium-doped yttrium oxide (Y 2 O 3 :Eu 3+) were synthesized by coprecipitation method with use of different surfactants like butanol, hexanol, and oleic acid. The as-prepared Y 2 O 3 :Eu 3+ samples were annealed at 800°C and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and UV-visible and photoluminescence (PL) spectroscopy techniques. The nanoparticle shows cubic phase structure. Surfactant helps to inhibit or control the particle growth and avoids agglomeration of nanoparticles effectively by reducing the oxygen bridge bonds between the particles. The most intense red emission peak occurs at 614 nm at an excitation wavelength of λ) 200 nm. Nanoparticles of Y 2 O 3 :Eu 3+ with a particle size of 30 nm synthesized by using oleic acid with NaCl show a 73% rise in PL intensity of the 614 nm peak.

The Journal of Physical Chemistry C, 2009

Nanoparticles of europium doped yttrium oxide (Y 2 O 3 :Eu 3+) were synthesized by the coprecipit... more Nanoparticles of europium doped yttrium oxide (Y 2 O 3 :Eu 3+) were synthesized by the coprecipitation method using oleic acid as a surfactant in the presence of other additives. Incorporation of additives like ethylenediaminetetraacetic acid (EDTA) and NaCl in the reaction mixture drastically affects the particle size, size homogeneity, and emission behavior of the nanophosphors. Photoluminescence emission of the nanophosphors drastically enhances and quenches on addition of NaCl and EDTA in the reaction mixture, respectively. Such emission behaviors of the nanophosphors are explained considering the nephelauxetic effect induced by the incorporated ions in the reaction solution.

The Journal of Physical Chemistry C, 2009

This work reports on the structural and magnetic properties of 10 nm-sized Co nanoparticles, alon... more This work reports on the structural and magnetic properties of 10 nm-sized Co nanoparticles, along with a surface investigation of chemi-adsorption of fatty acid-like oleic acid on their surfaces. The hexagonal close-packed superparamagnetic Co nanoparticles were ...

New Journal of Chemistry, 2012

Journal of Nanoscience and Nanotechnology, 2010

Soft phase magnetic Fe-B nanoparticles were prepared by coprecipitation and the hard phase magnet... more Soft phase magnetic Fe-B nanoparticles were prepared by coprecipitation and the hard phase magnetic Nd-Fe-B nanoparticles were obtained from mechanical ball mill of the bulk Nd-Fe-B with a shaker mill. Also mechanical ball mill technique was applied to the mixture of Nd-Fe-B and Fe-B nanoparticles to build up an exchange-coupled nanocomposite magnet. It was loaded in electronic furnace and annealed under a flow of hydrogen at 953 K for 30 min. The exchange coupled interaction of isotropic magnets was characterized by smooth hysteresis loop with a high value of remanence (Mr/Ms > 0.5).

Journal of Nanoscience and Nanotechnology, 2013

In this work, a combination of nanoparticles of Nd2Fe14B hard magnetic phase and alpha-Fe soft ma... more In this work, a combination of nanoparticles of Nd2Fe14B hard magnetic phase and alpha-Fe soft magnetic phase were synthesized by one pot chemical synthesis technique using sol-gel method. A gel of Nd-Fe-B was prepared using NdCl3 x 6H2O, FeCl3 x 6H2O, H3BO3, citric acid, and ethylene glycol by pechini type sol-gel method. The gel was subsequently calcined and annealed to obtain the mixed oxide powders. The produced metal oxide particles were identified with XRD, SEM, TEM to obtain the crystal structure, shape and domain structure of them. The nanoparticles of mixed phase of Nd2Fe14B/alpha-Fe were obtained from these oxides by a process of reduction-diffusion in vacuum by employing CaH2 as reducing agent. During this process it was optimized by controlling temperature, reaction time and concentration of the reducing agent (CaH2). The phase formation of Nd2Fe14B was resulted by the direct diffusion of NdH2, Fe and B. The magnetic property of produced hard and soft phases was successfully identified with vibrating sample magnetometer (VSM). The mixed domains of the hard and soft phases were identified with selected area electron diffraction method (SAED) patterns.

Journal of Luminescence, 2012

Well dispersed Eu doped CaMgSi 2 O 6 (CMS) nanoparticles of 12-19 nm average sizes were synthesiz... more Well dispersed Eu doped CaMgSi 2 O 6 (CMS) nanoparticles of 12-19 nm average sizes were synthesized by the co-precipitation method using different ratios of water and ethanol mixture as a solvent and subsequent air annealing. While ethanol as solvent produced pure CMS in monoclinic phase, pure water produced Ca 2 MgSi 2 O 7 (C2MS) and CMS in the mixed phase. Apart from the composition of CMS and C2MS, concentration and ionization state of the activator depended strongly on the composition (effective dielectric constant) of the solvent. Both the blue and red emission bands could be revealed for the europium activated CMS nanoparticles using single europium precursor. Efficiency of blue and red emissions in the nanophosphors, controlled by the relative abundance of europium in Eu 2 þ and Eu 3 þ oxidation states, could be controlled by adjusting the water content in the solvent. The relative intensity of the red emission (615 nm) decreased with the increase of water content in the solvent.

Current Applied Physics, 2016

Abstract A phosphor with higher emission efficiency in the visible region can be very helpful in ... more Abstract A phosphor with higher emission efficiency in the visible region can be very helpful in various optoelectronics applications such as solar cells. Effective conversion of UV and NIR radiations to more useful visible and red emissions were carried out through Gd 2 O 3 :Er 3+ nanostructures synthesized by conventional co-precipitation method. The spectroscopic study of Gd 2 O 3 :Er 3+ samples were carried out as a function of dopant concentration under the excitation wavelengths of 378, 975 and 1540 nm, respectively. The doping of erbium show downconversion emission at 561 and 660 nm under 378 nm excitation while upconversion emission under 975 and 1540 nm excitations shows upconversion of NIR photons to 561 and 660 nm visible emissions. The enhanced red emission (660 nm) at higher erbium concentration was observed due to the dominant cross-relaxation processes. The efficiency of upconversion luminescence is highly dependent on the various relaxation and energy transfer processes involved in different energy levels of erbium. The intensity of downconversion and upconversion emission was enhanced by lithium co-doping in Gd 2 O 3 :Er 3+ nanostructures. The incorporation of alkali metal ions in Gd 2 O 3 :Er 3+ shows considerable enhancement in downconversion and upconversion emission intensity making the phosphor more suitable for optoelectronic applications.

Science of Advanced Materials, 2012

Journal of Luminescence, 2015

Well-dispersed Eu-doped CaMgSi 2 O 6 (CMS) nanophosphors of 4-16 nm size range were synthesized b... more Well-dispersed Eu-doped CaMgSi 2 O 6 (CMS) nanophosphors of 4-16 nm size range were synthesized by a simple co-precipitation method followed by thermal annealing in controlled ambient. Emission behaviors of the nanophosphors have been studied to optimize and tune their emissions in desired spectral range (red, blue or both). Effects of temperature and calcination atmosphere on the interconversion (Eu 3 þ 2Eu 2 þ) ability of europium ions in CMS matrix have been studied thoroughly. It has been observed that by calcinating the nanophosphors in oxidizing atmosphere like O 2 , about 70% of the incorporated europium atoms can be transformed to their trivalent (Eu 3 þ) state. On the other hand, calcinating the nanophosphors in reducing atmosphere like H 2 þ N 2 mixture, about 99% of Eu ions can be transformed to their divalent state (Eu 2 þ). It has been demonstrated that by controlling the temperature and ambient of calcination, a dual emitting CMS:Eu nanophosphor could be converted either to blue or red emitting nanophosphor of high emission efficiency. The interchangeable emission characteristic of the size controlled nanophosphor is expected to have immense impact in the fabrication of highly efficient luminescent and display devices.

ChemInform, 2014

The properties of magnetic material of Nd-Fe-B are highly affected by various factors such as par... more The properties of magnetic material of Nd-Fe-B are highly affected by various factors such as particle size, magnetic anisotropy, phase purity and crystal structure. Incorporation of excess neodymium was carried out in various percentages so that it will adjust the proportion of neodymium in the host crystal after reduction treatment and finally help to improve magnetic property of a material. The interdiffusion of Nd-Fe and boron was studied for various compositions and their effect on magnetic property was understood with theoretical concepts. The factors such as amount of hard and soft phase in the reduction treated product is also responsible for the possible exchange coupling between hard and soft phase magnets for better magnetic properties.

Polymer International, 2012

Nanocomposites are a new class of polymeric materials which include organic or inorganic nano-pha... more Nanocomposites are a new class of polymeric materials which include organic or inorganic nano-phase materials. These nanocomposite films can show interesting properties which have many applications for wavelength conversion and energy saving. In this paper, we present polyolefin based nanocomposite films prepared using wavelength-converting red 'phosphors' such as Y 2 O 3 : Eu 3+ and LiAl 5 O 8 :Fe 3+ and blue 'phosphor' CaMgSi 2 O 6 : Eu 2+. The durability of the polymer chain is unaffected by incorporation of inorganic nanoparticles as there is no direct interaction between them. The addition of surfactant in the nanocomposite film helps to improve the dispersion ability of the nanoparticles and increase the flexibility of the polymer film. Wavelength-converting 'nanophosphors' incorporated in a polymer matrix help to increase the tensile strength of the film. The films show excellent wavelength conversion ability of UV light into the visible and near IR range. These nanocomposite films have great application in energy saving devices.

Thin Solid Films, 2012

Cu and Cu 2 O films can be prepared on indium-doped tin oxide glass substrates by simple electrod... more Cu and Cu 2 O films can be prepared on indium-doped tin oxide glass substrates by simple electrodeposition in a solution containing 0.1 M Cu(NO 3) 2 and 3 M lactic acid at different pH values. At low pH (pH=1.2), the uniform Cu films were obtained; when pH≥ 7, the pure Cu 2 O films can be deposited. Especially, at pH=11, the deposited Cu 2 O films exhibited cubic surface morphology exposing mainly {100} plane; in contrast, the films consisting of semi-spherical particles were obtained when the solution was being stirred for 2 weeks prior to use. The possible growth process and mechanism were comparatively discussed.

The Journal of Physical Chemistry C, 2009

Nanoparticles of europium-doped yttrium oxide (Y 2 O 3 :Eu 3+) were synthesized by coprecipitatio... more Nanoparticles of europium-doped yttrium oxide (Y 2 O 3 :Eu 3+) were synthesized by coprecipitation method with use of different surfactants like butanol, hexanol, and oleic acid. The as-prepared Y 2 O 3 :Eu 3+ samples were annealed at 800°C and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and UV-visible and photoluminescence (PL) spectroscopy techniques. The nanoparticle shows cubic phase structure. Surfactant helps to inhibit or control the particle growth and avoids agglomeration of nanoparticles effectively by reducing the oxygen bridge bonds between the particles. The most intense red emission peak occurs at 614 nm at an excitation wavelength of λ) 200 nm. Nanoparticles of Y 2 O 3 :Eu 3+ with a particle size of 30 nm synthesized by using oleic acid with NaCl show a 73% rise in PL intensity of the 614 nm peak.

The Journal of Physical Chemistry C, 2009

Nanoparticles of europium doped yttrium oxide (Y 2 O 3 :Eu 3+) were synthesized by the coprecipit... more Nanoparticles of europium doped yttrium oxide (Y 2 O 3 :Eu 3+) were synthesized by the coprecipitation method using oleic acid as a surfactant in the presence of other additives. Incorporation of additives like ethylenediaminetetraacetic acid (EDTA) and NaCl in the reaction mixture drastically affects the particle size, size homogeneity, and emission behavior of the nanophosphors. Photoluminescence emission of the nanophosphors drastically enhances and quenches on addition of NaCl and EDTA in the reaction mixture, respectively. Such emission behaviors of the nanophosphors are explained considering the nephelauxetic effect induced by the incorporated ions in the reaction solution.

The Journal of Physical Chemistry C, 2009

This work reports on the structural and magnetic properties of 10 nm-sized Co nanoparticles, alon... more This work reports on the structural and magnetic properties of 10 nm-sized Co nanoparticles, along with a surface investigation of chemi-adsorption of fatty acid-like oleic acid on their surfaces. The hexagonal close-packed superparamagnetic Co nanoparticles were ...

New Journal of Chemistry, 2012

Journal of Nanoscience and Nanotechnology, 2010

Soft phase magnetic Fe-B nanoparticles were prepared by coprecipitation and the hard phase magnet... more Soft phase magnetic Fe-B nanoparticles were prepared by coprecipitation and the hard phase magnetic Nd-Fe-B nanoparticles were obtained from mechanical ball mill of the bulk Nd-Fe-B with a shaker mill. Also mechanical ball mill technique was applied to the mixture of Nd-Fe-B and Fe-B nanoparticles to build up an exchange-coupled nanocomposite magnet. It was loaded in electronic furnace and annealed under a flow of hydrogen at 953 K for 30 min. The exchange coupled interaction of isotropic magnets was characterized by smooth hysteresis loop with a high value of remanence (Mr/Ms > 0.5).

Journal of Nanoscience and Nanotechnology, 2013

In this work, a combination of nanoparticles of Nd2Fe14B hard magnetic phase and alpha-Fe soft ma... more In this work, a combination of nanoparticles of Nd2Fe14B hard magnetic phase and alpha-Fe soft magnetic phase were synthesized by one pot chemical synthesis technique using sol-gel method. A gel of Nd-Fe-B was prepared using NdCl3 x 6H2O, FeCl3 x 6H2O, H3BO3, citric acid, and ethylene glycol by pechini type sol-gel method. The gel was subsequently calcined and annealed to obtain the mixed oxide powders. The produced metal oxide particles were identified with XRD, SEM, TEM to obtain the crystal structure, shape and domain structure of them. The nanoparticles of mixed phase of Nd2Fe14B/alpha-Fe were obtained from these oxides by a process of reduction-diffusion in vacuum by employing CaH2 as reducing agent. During this process it was optimized by controlling temperature, reaction time and concentration of the reducing agent (CaH2). The phase formation of Nd2Fe14B was resulted by the direct diffusion of NdH2, Fe and B. The magnetic property of produced hard and soft phases was successfully identified with vibrating sample magnetometer (VSM). The mixed domains of the hard and soft phases were identified with selected area electron diffraction method (SAED) patterns.

Journal of Luminescence, 2012

Well dispersed Eu doped CaMgSi 2 O 6 (CMS) nanoparticles of 12-19 nm average sizes were synthesiz... more Well dispersed Eu doped CaMgSi 2 O 6 (CMS) nanoparticles of 12-19 nm average sizes were synthesized by the co-precipitation method using different ratios of water and ethanol mixture as a solvent and subsequent air annealing. While ethanol as solvent produced pure CMS in monoclinic phase, pure water produced Ca 2 MgSi 2 O 7 (C2MS) and CMS in the mixed phase. Apart from the composition of CMS and C2MS, concentration and ionization state of the activator depended strongly on the composition (effective dielectric constant) of the solvent. Both the blue and red emission bands could be revealed for the europium activated CMS nanoparticles using single europium precursor. Efficiency of blue and red emissions in the nanophosphors, controlled by the relative abundance of europium in Eu 2 þ and Eu 3 þ oxidation states, could be controlled by adjusting the water content in the solvent. The relative intensity of the red emission (615 nm) decreased with the increase of water content in the solvent.