BHU Institutional Repository :: Browsing by Author "Kaur, Gagandeep"

Browsing by Author "Kaur, Gagandeep"

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Acetylsalicylic acid sensitized lasing luminescence of terbium complex in PVA: A case of energy avalanche via 1, 10-Phenanthroline
(Elsevier, 2017) Kumar, Brijesh; Kaur, Gagandeep; Rai, S.B.
Ternary complexes of Terbium with acetylsalicylic acid (ASA) and 1, 10 Phenanthroline (Phen) were synthesized in PVA polymer film. The structural properties of the complex were evaluated using XRD and formation of complex was verified by FT-IR technique. The absorption, excitation and photoluminescence properties of the Tb3+ ion get improved when complexed with ASA and Phen ligands. Selective excitations of Tb3+, ASA and Phen revealed an efficient energy transfer enhancing green luminescence of Tb3+ ion on excitation with 355, 335 and 306 nm radiations respectively. The emission intensity arising from Tb(ASA)3Phen complex in PVA has been observed to be much more as compared to the one with Tb3+ ions only. The fluorescence decay time for Tb3+ (5D4 → 7F5 transition) is seen to increase from 557 μs in Tb3+ to 628 μs in presence of Tb(ASA)3Phen complex. The fluorescence decay time for Phen and ASA is seen to decrease from 4.43 ns to 1.64 ns and from 5.75 ns to 1.58 ns respectively in Tb(ASA)3Phen complex. This reflects an energy transfer from excited Phen to ASA and finally to Tb3+ is proposed as the cause of the above observations and thus an energy avalanche. The intense green luminescence on 266 nm excitation in Tb(ASA)3Phen complex in PVA with quantum yield of 0.32 shows a tendency towards lasing. © 2016 Elsevier B.V.
Anomalous electrical properties of poly vinyl alcohol films with Tb3+ ions and copper nanoparticles in different solvents
(Royal Society of Chemistry, 2015) Kumar, Brijesh; Kaur, Gagandeep; Singh, Prabhakar; Rai, S.B.
Laser ablation was used to fabricate copper nanoparticles (NPs) in different solvents from sodium lauryl sulphate, acetone and ethanol by applying 1064 nm radiation from a Nd:YAG laser. The sizes and shapes of the colloidal Cu NPs were investigated by transmission electron microscopy (TEM). The electrical conductivities of Tb3+ in polymer films with Cu NPs were measured in the frequency range of 20 Hz to 1 MHz and the temperature range of 308-343 K. It was found that the electrical conductivity of Tb3+ was greater for larger Cu NPs with sizes ranging from 20-40 nm in ethanol as compared to Cu NPs with smaller dimensions formed in the other two solvents. It was concluded that using ethanol as the solvent enhanced the electrical conductivity of Tb3+ in the polymer film. The activation energy as well as the variation in the loss tangent with temperature also explains the enhanced electrical conductivity. This journal is © The Royal Society of Chemistry 2015.
Bismuth functionalized PVA film: Field, plasmonic and pH effect on PVA originated broad photoluminescence
(Royal Society of Chemistry, 2016) Kumar, Brijesh; Kaur, Gagandeep; Verma, Rajesh Kumar; Bahadur, A.; Rai, S.B.
Bismuth (Bi) NPs have been synthesized by Laser Ablation Synthesis in Solution (LASiS) at different pH in different aqueous solutions [viz. H2O (H), H2O + NaOH (HN), and H2O + HCl (HC)]. The NPs in aqueous solution have been characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and UV-Vis-NIR techniques. The NPs are spherical, core shell type and hollow spheres in H, HN and HC, respectively. The vibrational features have been studied using Raman technique and correlated with different states of NPs (neutral NPs, ionized NPs, hollow NPs, core shell type NPs and NPs complex, etc.). The NPs were later dispersed in polyvinyl alcohol (PVA). The electronic spectra of PVA molecules along with different types of Bi NPs films have been studied at different excitation wavelengths (λexci = 240 nm, 270 nm, 300 nm and 360 nm). The sequences of optical sensitization in increasing order are NPs, core shell type NPs, and hollow spherical NPs. The enhanced emission is discussed in terms of plasmonic and field effects and is verified by lifetime measurements. © 2016 The Royal Society of Chemistry.
Bismuth induced enhanced green emission from terbium ions and their complex in thin films
(Royal Society of Chemistry, 2014) Kaur, Gagandeep; Kumar, Brijesh; Verma, R.K.; Rai, S.B.
Bismuth nanoparticles (NPs) have been prepared by the pulsed laser ablation technique using the third harmonics of a Nd-YAG laser. UV-absorption and TEM micrographs show Bi NPs of spherical shape with the average particle size ranging from 15 to 20 nm. These NPs were dispersed with Tb3+ ions and their complex with salicylic acid (Sal) in polyvinyl alcohol to obtain thin films. The influence of Bi NPs on the emissive properties of Tb3+ ions and the [Tb(Sal)3(phen)] complex has been studied by luminescence spectroscopy using 266 nm and 355 nm as excitation wavelengths. The luminescence intensity of Tb3+ ions complexed with Sal in the thin polymer films increased significantly as compared to the Tb3+ ions in the presence of Bi NPs on excitation at 355 nm. However, terbium ions in the case of the [Tb(Sal)3(phen)] complex together with NPs show an intense and extended emission spectrum in the 375-700 nm range for transitions arising from 5D3 and 5D4 levels to different 7FJ levels on 266 nm excitation. The luminescence enhancement has also been supported by lifetime measurements. © 2014 the Partner Organisations.
Cool white light emission in dysprosium and salicylic acid doped poly vinyl alcohol film under UV excitation
(2012) Kaur, Gagandeep; Rai, S.B.
Dysprosium (Dy) and Salicylic acid (Sal) doped Poly Vinyl Alcohol (PVA) films have been successfully prepared by solution cast technique. The absorption, excitation, emission and lifetime analysis of the samples have been carried out. Judd-Ofelt theory has been used to estimate several parameters for DyCl 3 and Dy(Sal) 3Phen in PVA polymer film which show fair agreement between the experimental and the theoretical values supporting the J-O theory. A combination of blue and yellow emissions in Dy x(Sal) 3Phen co-doped PVA samples makes one perceive cool white light when excited by ultraviolet light. Energy transfer (ET) from Sal to Dy 3+ is investigated by directly observing the luminescence intensity of Dy 3+ in the Dyx(Sal)3Phen co-doped PVA samples which is much stronger than that in the DyCl3 in PVA which is further confirmed by lifetime studies with different concentrations of Dysprosium ion (Dy 3+). The generation of white light with chromaticity coordinates (0.30, 0.34) makes it potential material for white LED and display devices. © 2011 Springer Science+Business Media, LLC.
Enhancement of up-conversion emission and emerging cool white light emission in co-doped Yb3+/ Er3+: Li2O-LiF-B2O3-ZnO glasses for photonic applications
(Elsevier Ltd, 2017) Vijayalakshmi, L.; Kumar, K. Naveen; Hwang, Pyung; Kaur, Gagandeep
A series of co-doped (Yb3+/Er3+): Li2O-LiF-B2O3-ZnO glasses were prepared by standard melt quenching technique. Structural and morphological studies were carried out by XRD and FESEM. Phonon energy dynamics have been clearly elucidated by Laser Raman analysis. The pertinent absorption bands were observed in optical absorption spectra of singly doped and co-doped Yb3+/Er3+: LBZ glasses. We have been observed a strong up-conversion red emission pertaining to Er3+ ions at 1.0 mol% under the excitation of 980 nm. However, the up-conversion and down conversion (1.53 µm) emission intensities were remarkably enhanced with the addition of Yb3+ ions to Er3+: LBZ glasses due to energy transfer from Yb3+ to Er3+. Up-conversion emission spectra of co-doped (Yb3+/Er3+): LBZ glasses exhibits three strong emissions at 480 nm, 541 nm and 610 nm which are assigned with corresponding electronic transitions of 2H9/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 respectively. Consequently, the green to red ratio values (G/R) also supports the strong up-conversion emission. The Commission International de E′clairage coordinates and correlated color temperatures (CCT) were calculated from their up-conversion emission spectra of co-doped (Yb3+/Er3+): LBZ glasses. The obtained chromaticity coordinates for optimized glass (0.332, 0.337) with CCT value at 5520 K are very close to the standard white colorimetric point in cool white region. These results could be suggested that the obtained co-doped (Yb3+/Er3+): LBZ glasses are promising candidates for w-LEDs applications. © 2017 Elsevier Ltd and Techna Group S.r.l.
Eu3+ and Yb3+ codoped Gd2 O3 single phase nanophosphor: An enhanced monochromatic red emission through cooperative upconversion and downconversion
(2010) Kaur, Gagandeep; Singh, S.K.; Rai, S.B.
Single phase cubic Gd2 O3 nanophosphor codoped with Eu3+ and Yb3+ ions has been synthesized through solution combustion route. Structural properties have been investigated using x-ray diffraction (XRD) and transmission electron microscopy (TEM). The as-synthesized Gd2 O3 phosphor shows amorphous nature which changes to crystalline single cubic phase on annealing. Optical properties have been investigated through absorption, photoluminescence, and lifetime measurements. Intense red emission (D5 0 → F7 2) is observed both from cooperative upconversion (Yb3+ + Yb3+ → Eu3+ on 976 nm excitation) as well as through downconversion process (on 355 nm excitation). The unusual and rarely reported emissions from the higher lying D5 J (J=2, 3, and 4) to F7 J (J=0, 1, 2, 3, and 4) levels are also observed with 976 nm excitation. Nearly twenty two times enhancement in the intensity of the hypersensitive transition (D5 0 → F7 2) along with an increase in the decay time (770 μs) is observed for the sample annealed at 1200 °C on 355 nm excitation. These observations have been explained satisfactorily. © 2010 American Institute of Physics.
Gd 3+ sensitized enhanced green luminescence in Gd:Tb(Sal) 3Phen complex in PVA
(2011) Kaur, Gagandeep; Dwivedi, Y.; Rai, S.B.
Ternary and tertiary complexes of Tb(Sal) 3Phen and Gd:Tb(Sal) 3Phen were synthesized and characterized in PVA polymer. The structural properties of these systems were evaluated on the basis of NMR and FT-IR techniques. The absorption, excitation and emissive properties of the Tb 3+ ion were improved when coordinated with Sal and Phen ligands. Photoluminescence properties of the complexes in solution, crystals and dispersed in PVA film were explored in steady state and in time domain. Selective excitations (487, 355, 310 and 266 nm) of Tb 3+, Sal and Gd 3+ ions reveal an intramolecular energy transfer process. The emission of Gd:Tb(Sal) 3Phen complex in PVA indicates the contribution of Gd 3+ ion to enhance the emission intensity of Tb 3+ ion. On the basis of these investigations, photophysics was widely discussed in terms of energy transfer and encapsulation effect. © 2010 Springer Science+Business Media, LLC.
Green and NIR sensitized luminescent nanophosphor: Preparation, characterization and application
(2012) Kaur, Gagandeep; Dwivedi, Y.; Rai, A.; Rai, S.B.
Luminescent nanophosphor of Er, Yb: Gd 2O 3 has been synthesized by well known combustion synthesis. Along with strong UV-Vis upconversion emission, sensor for temperature and magnetic field, nano-heater etc., it can also be used as luminescent ink by dispersing the nanophosphor in aqueous polyvinyl alcohol solution. The stability of the ink has been found to depend strongly on the mixing process of the phosphor powder in the polymer solution. The X-ray diffraction results and TEM images with diffraction pattern show that the particles are in cubic phase of Gd 2O 3 with particles of average size <40 nm. SEM images show flaky structure which makes it suitable for dispersing in PVA and useful for luminescent ink purposes on NIR excitation. The FT-IR and the thermal analysis support the presence of PVA. Upconversion and downconversion luminescence has also been observed with 532 nm excitation and energy transfer mechanism has been explained. The NIR pumping gives strong UC emission bands in red and green regions extending up to extreme UV (240 nm) in this host. © 2012 Elsevier B.V. All rights reserved.
Investigations of spherical Cu NPs in sodium lauryl sulphate with Tb3+ ions dispersed in PVA films
(Elsevier Ltd, 2016) Kumar, Brijesh; Kaur, Gagandeep; Rai, S.B.
Cu nanoparticles (NPs) have been prepared in SDS solution using 1064 nm laser radiation at different fluence 37 J/cm2, 64 J/cm2 and 88 J/cm2 and structurally characterized. The TEM measurements reveal the presence of nanoparticles of spherical shape with different size. The size of the nanoparticles and their concentration increases with the increase of fluence.The effect of these Cu nanoparticles on the emissive properties of Tb3+ ion in polymer films has been studied. It is found that emission intensity of Tb3+ first increases and then deceases both with concentration of Cu NPs as well as with sizes. The PL intensity of Tb3+ ions is minimum for Cu NPs prepared with highest fluence. It has been explained in term of local field effect. This was also verified by life time measurements. These thin PVA films of copper nanoparticles displayed a highly temperature-dependent electrical conductivity with sensitivity at least comparable to commercial materials which suggest the use of these copper NPs embedded PVA films as novel, low-cost sensor materials. © 2015 Elsevier Ltd.
Investigations on electrical and magnetic properties of Fe2O3 nanoparticles dispersed in polymer film with terbium ion
(American Scientific Publishers, 2015) Kumar, Brijesh; Kaur, Gagandeep; Kotnala, R.K.; Rai, S.B.
Spherical Fe2O3 nanoparticles (NPs) with average particle size 30–70 nm have been prepared by laser ablation method in distilled water by applying 1064 nm laser line from Nd:YAG laser and were used for the fabrication of PVA films with and without Tb ion. The frequency and temperature dependent electrical conductivity of PVA polymer film have been measured in presence of Tb ions with Fe2O3 NPs for frequency range between 20 Hz to 1 MHz and temperature range 308–348 K. It has been found that electrical conductivity of the films is enhanced in presence of Fe2O3 NPs and Tb ion. Magnetization (M–H) loop revealed PVA as diamagnetic with very small magnetic moment −0.0015 emu/g converted to ferromagnetic in presence of Fe2O3 nanoparticles and paramagnetic in presence of Tb ion with saturation magnetization of 0.004 emu/g and 0.07 emu/g respectively. It maintains its paramagnetic character in presence of both Fe2O3 NPs and Tb ions with saturation magnetization 0.03 emu/g. © 2015 American Scientific Publishers. All rights reserved.
Luminescence properties of Sm, Tb(Sal)3Phen complex in polyvinyl alcohol: An approach for white-light emission
(2011) Kaur, Gagandeep; Rai, S.B.
Polyvinyl alcohol polymer films doped with Sm,Tb(Sal)3Phen complexes have been synthesized using solution casting technique. An enhancement in absorption intensity is observed revealing the encapsulation of rare earth ions by salicylic acid (Sal)/1,10 phenanthroline (Phen) complex. Photoluminescence spectra of the co-doped samples were examined by varying the concentration of Tb3+ keeping concentration of Sm3+ ions fixed and vice-versa. It is found that the polymer samples emit a combination of blue, green and orange-red wavelengths tunable to white light when excited with 355 nm radiation. The emission spectra also show a self-quenching effect at higher concentration of Sm3+ ions. An efficient energy transfer was observed from Tb3+ : 5D4 → Sm3+ : 4G9/2. The reason for the enhancement in fluorescence intensities of Sm3+ in the co-doped polymer sample is the intermolecular as well as the intramolecular energy transfer. © 2011 IOP Publishing Ltd.
Plasmon-enhanced luminescence of Sm complex using silver nanoparticles in Polyvinyl Alcohol
(2012) Kaur, Gagandeep; Verma, R.K.; Rai, D.K.; Rai, S.B.
Silver (Ag) nanoparticles (NPs) were prepared by laser ablation in water with an aim to enhance the luminescence of rare earth coordinated complex in polymer host. A fixed concentration of the complex containing Samarium (Sm), Salicylic acid (Sal) and 1, 10-phenanthroline (Phen) were combined with different concentrations of silver NPs in PolyVinyl Alcohol at room temperature. Absorption spectrum and XRD patterns of the sample show that the Sm(Sal) 3Phen complex is accompanied by Ag NPs. The luminescence from the complex was recorded in the presence and absence of Ag NPs using two different excitation wavelengths viz. 400 and 355 nm. Of these, 400 nm radiation falls in the surface plasmon resonance of Ag NPs. It was found that the Ag NPs led to a significant enhancement in luminescence of the complex. Surprisingly, a high concentration of Ag NPs tends to quench the luminescence. © 2012 Elsevier B.V.
Sensitized green emission of terbium with dibenzoylmethane and 1, 10 phenanthroline in polyvinyl alcohol and polyvinyl pyrrolidone blends
(Elsevier B.V., 2017) Kumar, Brijesh; Kaur, Gagandeep; Rai, S.B.
Tb doped polyvinyl alcohol: polyvinyl pyrrolidone blends with dibenzoylmethane (DBM) and 1, 10 Phenanthroline (Phen) have been prepared by solution cast technique. Bond formation amongst the ligands and Tb3 + ions in the doped polymer has been confirmed employing Fourier Transform Infrared (FTIR) techniques. Optical properties of the Tb3 + ions have been investigated using UV–Vis absorption, excitation and fluorescence studies excited by different radiations. Addition of dimethylbenzoate and 1, 10 Phenanthroline to the polymer blend increases the luminescence from Tb3 + ions along with energy transfer from the polymer blend itself. Luminescence decay curve analysis affirms the non-radiative energy transfer from DBM and Phen to Tb3 + ions, which is identified as the reason behind this enhancement. The fluorescence decay time of PVA-PVP host decreases from 6.02 ns to 2.31 ns showing an evidence of energy transfer from the host blend to the complexed Tb ions. Similarly the lifetime of DBM and Phen and both in the blend reduces in the complexed system showing the feasibility of energy transfer from these excited DBM and Phen to Tb3 + and is proposed as the cause of the above observations. These entire phenomena have been explained by the energy level diagram. © 2016
Study of enhanced red emission from Sm(Sal)3Phen ternary complexes in Poly Vinyl Alcohol film
(2010) Kaur, Gagandeep; Dwivedi, Y.; Rai, S.B.
In the present work, dinuclear complexes of salicylic acid (Sal) and 1,10-phenanthroline (Phen) were synthesized with different concentrations of Samarium ion (Sm3+) in Poly Vinyl Alcohol (PVA) polymer films and their structural and spectroscopic properties were investigated. Judd-Ofelt theory has been employed to estimate the several radiative parameters for SmCl3 and Sm(Sal)3Phen complex in PVA polymer film which are in fairly agreement between the experimental and the theoretical values supporting the J-O theory. Photoluminescence properties of the complex have been studied on 355 nm and 400 nm excitations in steady state as well as in time domain. On the basis of the UV-Vis absorption, FT-IR absorption, excitation, emission spectra and decay curves, spectroscopic properties of these films were studied and the photophysics involved was explained in terms of energy transfer and the RE encapsulation effect. © 2010 Elsevier B.V. All rights reserved.
Synthesis and characterization of a stable dispersion of multifunctional Gd2O3:Er,Yb in polyvinyl alcohol
(John Wiley and Sons Ltd, 2013) Kaur, Gagandeep; Rai, S.B.
A stable dispersion of multifunctional Gd2O3:Er,Yb phosphor in polyvinyl alcohol (PVA) was synthesized by varying the concentration of Yb3+ ions. It had a strong ultraviolet-visible-near infrared (UV-vis) upconversion emission and applications in temperature and magnetic field sensors (e.g., nano-heaters), as well as potential use in bioleveling and bioimaging. Stability of the dispersion was found to strongly depend on the mixing process of the powder in the polymer solution. Spherical shaped nanoparticles in cubic phase of ~ 43 nm diameter were synthesized and characterized by X-ray diffraction; results were confirmed by scanning electron microscopy (SEM). Fourier transform infrared sspectroscopy (FT-IR) and thermal analysis supported the presence of PVA. NIR pumping produced strong UC emission bands in the red and green regions extending up to very high UV (240 nm). This method provides an alternative for synthesizing a highly UC-efficient non-agglomerated pure transparent dispersion from various efficient phosphors for biological applications. Copyright © 2012 John Wiley & Sons, Ltd.
Synthesis, structural, optical and electrical properties of metal nanoparticle-rare earth ion dispersed in polymer film
(2013) Kumar, Brijesh; Kaur, Gagandeep; Singh, P.; Rai, S.B.
Cu-nanoparticles have been prepared by ablating a copper target submerged in benzene with laser pulses of Nd:YAG (wavelength: 355, 532 nm and 1,064 nm). Colloidal nanoparticles have been characterized by UV-Vis spectroscopy and transmission electron microscopy. The obtained radius for the nanoparticles prepared using 1,064 nm irradiation lies in the range 15-30 nm, with absorption peak at 572 nm. Luminescence properties of Tb3+ ions in the presence and absence of Cu-nanoparticles have been investigated using 355 nm excitation. An enhancement in luminescence of Tb3+ by local field effect causing increase in lifetime of 5D4 level of Tb3+ ion has been observed. Frequency and temperature-dependent conductivity of Tb3 + doped PVA thin films with and without Cu-nanoparticles have been measured in the frequency range 20 Hz-1 MHz and in the temperature range 318-338 K (well below its melting temperature). Real part of the conductivity spectra has been explained in terms of power law. The electrical properties of the thin films show a decrease in dc conductivity on incorporation of the Cu-nanoparticles. © 2013 Springer-Verlag Berlin Heidelberg.
Synthesis, structural, thermal and optical studies of rare earth coordinated complex: Tb(Sal)3Phen
(2011) Kaur, Gagandeep; Dwivedi, Y.; Rai, S.B.
Complexes of salicylic acid (Sal) and 1,10-phenanthroline (Phen) were synthesized coordinated with terbium ion (Tb3+) in crystalline phases. The structural characterizations of the lanthanide complex were made using FT-IR, NMR (1H and 13C) and XRD techniques. These measurements confirm the formation of Tb(Sal)3Phen complex structure. The thermal aspects of the complex were examined using DTA and TGA techniques. An enhancement in luminescence intensity of Tb3+ ion bands were observed in Tb(Sal)3Phen complex as compared to TbCl3 crystals on 355 nm laser excitation. Enhancement is reported due to the efficient energy transfer process from Sal to Tb3+ ions. This is also confirmed by the time resolved photoluminescence spectroscopy with increase in lifetime of Tb3+ ions due to encapsulation in Sal/Phen network. Our system in itself can be a deserving candidate for luminescent solar collector material when coupled with solar cells. © 2011 Elsevier B.V. All rights reserved.

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