Photoluminescence and white light generation behavior of lithium gadolinium silicoborate glasses

Shamshad, L.,Rooh, G.,Kirdsiri, K.,Srisittipokakun, N.,Damdee, B.,Kim, H.J.,Kaewkhao, J. Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.695 No.-

<P><B>Abstract</B></P> <P>The Dy<SUP>3+</SUP>-doped lithium gadolinium silica borate glasses with composition (in mol%) 40Li<SUB>2</SUB>O:15Gd<SUB>2</SUB>O<SUB>3</SUB>:5SiO<SUB>2</SUB>: (40-x)B<SUB>2</SUB>O<SUB>3</SUB>:xDy<SUB>2</SUB>O<SUB>3</SUB>, x = 0.01, 0.1, 0.5, 1.0, 2.0 were prepared by melt quenching technique and characterized through absorption and emission spectra, CIE chromaticity coordinates and decay rate analysis. Judd-Oflet parameters have been calculated for lithium gadolinium silico borate glass and used for the derivation of radiative properties for excited luminescent levels of Dy<SUP>3+</SUP> ions. The feasibility of white light generation have been evaluated by the yellow-to-blue emission intensity ratios and CIE chromaticity coordinates as a function of Dy<SUP>3+</SUP> concentration. The non-exponential decay rates are well-fitted to Inokuti-Hirayama model for S = 6. The perceived non-exponential decay nature and life time quenching have been ascribed to the energy transfer between excited and unexcited Dy<SUP>3+</SUP> ions through dipole–dipole interaction. The CCT values for the present studied glasses obtained in the 4584-4235 K at λ<SUB>exc</SUB> = 387 nm. These CCT values are below the warm CCT (i.e CCT 4000 K). The reasonably good luminescence properties of LGSiBDy10 glass indicates the potentiality of the title of glass to be applied as lasing medium for white light generation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Spectroscopic properties of Dy<SUP>3+</SUP> ion in Li<SUB>2</SUB>OGd<SUB>2</SUB>O<SUB>3</SUB> SiO<SUB>2</SUB> B<SUB>2</SUB>O<SUB>3</SUB> were studied. </LI> <LI> JO analysis were used to analyze spectroscopic properties. </LI> <LI> White emission was observed from glass sample. </LI> <LI> Lasing properties were characterized. </LI> </UL> </P>

Preparation and Characterization of Hybrid Polycaprolactone/Cellulose Ultrafine Fibers via Electrospinning

Shamshad Ali,김성훈,Zeeshan Khatri,오경화,김익수 한국고분자학회 2014 Macromolecular Research Vol.22 No.5

A series of poly(ε-caprolactone) (PCL)/cellulose acetate (CA) ultrafine fiber webs were prepared viaelectrospinning followed by deacetylation in an aqueous alkaline solution to convert CA into cellulose (CEL). Thewetting properties of PCL/CA and PCL/CEL blends were evaluated to investigate wicking behavior. The results showedthat the conversion of PCL/CA into PCL/CEL leads to an improved wettability. Attenuated total reflectance-Fouriertransform infrared (ATR-FTIR) study revealed that CA was completely converted into CEL after deacetylation, andPCL/CEL blends exhibited characteristics peaks of both constituent fibers. The differential scanning calorimetry (DSC)analysis demonstrated that the PCL/CA ultrafine fibers were partially miscible in PCL/CA ultrafine fibers. The fiber morphologyunder field emission scanning electron microscopy (FE-SEM) showed that the electrospun ultrafine fibers were beadfree. The crystallinity of PCL-CEL, (1:4) blend was greatly decreased in comparison to the treated PCL as revealed bywide angle X-ray diffraction (WAXD) measurements. The potential applications of PCL/CEL webs include liquidbiofilters, biosensor and biomedical materials.

Zein/Cellulose Acetate Hybrid Nanofibers: Electrospinning and Characterization

Shamshad Ali,김성훈,Zeeshan Khatri,오경화,김익수 한국고분자학회 2014 Macromolecular Research Vol.22 No.9

Protein based scaffolds are preferred for tissue engineering and other biomedical applications owing totheir unique properties. Zein, a hydrophobic protein, is a promising natural biodegradable polymer. However, electrospunstructures prepared from Zein have poor mechanical and wetting properties. Cellulose acetate (CA) is aneconomical, biodegradable polymer having good mechanical and water retention properties. The aim of presentstudy was to fabricate a novel material by electrospinning Zein/CA blends. A series of Zein/CA hybrid nanofiberswere electrospun and characterized. The attenuated total reflectance-Fourier transform infrared spectroscopy (ATRFTIR)spectrum showed the characteristic peaks of both Zein and CA, and was composition dependent. The X-rayphotoelectron spectrometry (XPS) curves of Zein/CA blends demonstrated a similar profile to that of pristine Zeinnanofibers. Thermogravimetric analyser (TGA) studies confirmed that the Zein/CA hybrid nanofibers have a higherdegradation temperature and better thermal stability than pristine Zein nanofibers. The glass transition temperature(Tg) of Zein/CA hybrid nanofibers was also increased in comparison to pure Zein nanofibers as revealed by differentialscanning calorimetry (DSC). Zein/CA hybrid nanofibers have hydrophilic surface character as revealed bywater contact angle (WCA) analysis. SEM imaging showed bead free morphology of the electrospun nanofibers. The average nanofiber diameter decreased for Zein/CA blends with increasing CA composition. The electrospunZein/CA hybrid nanofibers may be used for tissue engineering scaffolds and for other biomedical materials.

A comparative study of gadolinium based oxide and oxyfluoride glasses as low energy radiation shielding materials

Shamshad, L.,Rooh, G.,Limkitjaroenporn, P.,Srisittipokakun, N.,Chaiphaksa, W.,Kim, H.J.,Kaewkhao, J. Elsevier 2017 Progress in nuclear energy Vol.97 No.-

<P><B>Abstract</B></P> <P>The Gadolinium based oxide and oxyfluoride glass systems were prepared using conventional melt quenching method and studied for their radiation shielding properties. The mass attenuation coefficients (μ<SUB>m</SUB>), effective atomic numbers (Z<SUB>eff</SUB>) and effective electron densities (N<SUB>e</SUB>) of the glasses at different photon energies were calculated theoretically by WinXcom program and experimentally determined by the transmission method. Moreover, the mass attenuation coefficient was investigated using Geant4 Monte Carlo code and compared with each other. The gamma ray energies were varied by Compton scattering technique. The values of attenuation parameters of both the glass systems have been found to be decrease with the increase in gamma ray photon energy. The results show that, the experimental values of mass attenuation coefficients, effective atomic numbers and effective electron densities are in good agreement with the theoretical values. It seems that Geant4 values are systematically lower than WinXCom. It could be caused by the simplification of geometry in Geant4. Although, the oxide glass system have superior shielding properties than oxyfluoride glass system, but, still, it has better shielding properties than commercial window glass and some existing concretes indicating the potential of this glass to be used as gamma ray shielding material. Moreover, there is no effect of fluoride component on the optical spectra. The optical absorption spectra of the glass systems under investigation have been shown with light transparency which is an edge to be used as radiation shielding material.</P>

Effect of cadmium addition on the optical constants of thermally evaporated amorphous Se.S.Cd thin films

Shamshad A. Khan,F.S. Al-Hazmi,S. Al-Heniti,A.S. Faidah,A.A. Al-Ghamdi 한국물리학회 2010 Current Applied Physics Vol.10 No.1

Se75S25-xCdx is a promising ternary material, which has received considerable attention due to its applications in the fabrication of various solid state devices. These have distinct advantages, large packing density,mass replication, fast data rate, high signal-to-noise ratio and high immunity to defects. Measurements of optical constants (absorption coefficient, refractive index, extinction coefficient, real and imaginary part of the dielectric constant) have been made on Se75S25-xCdx (where x = 0, 2, 4, 6 and 8) thin films of thickness 3000 Å as a function of photon energy in the wave length range 400–1000 nm. It has been found that the optical band gap and extinction coefficient increases while the value refractive index decreases on incorporation of cadmium in Se–S system. The results are interpreted in terms of the change in concentration of localized states due to the shift in Fermi level. Due to the large absorption coefficient and compositional dependence of reflectance, these materials may be suitable for optical disk material.

Optical band gap and optical constants in a-Se80Te20 xPbx thin films

Shamshad A. Khan,M. Zulfequar,M. Husain 한국물리학회 2005 Current Applied Physics Vol.5 No.6

The optical constants (absorption coecient, refractive index, extention coecient, real and imaginary part of dielectric con-stant) have been studied for a-Se80Te20. xPbx (wherex = 0,2,6,10) thin lms as a function of photon energy in the wave length range(5001000nm). It has been found that the optical band gap increases while the refractive index and the extinction coecient (k)decreases on incorporation of lead in SeTe system. The value of absorption coecient (a) and the extinction coecient (k)increases, while the value of refractive index (n) decreases with incident photon energy. The results are interpreted in terms ofthe change in concentration of localized states due to the shift in fermi level..

Accelerated Tseng's Technique to Solve Cayley Inclusion Problem in Hilbert Spaces

Shamshad, Husain,Uqba, Rafat Department of Mathematics 2022 Kyungpook mathematical journal Vol.62 No.4

In this study, we solve the Cayley inclusion problem and the fixed point problem in real Hilbert space using Tseng's technique with inertial extrapolation in order to obtain more efficient results. We provide a strong convergence theorem to approximate a common solution to the Cayley inclusion problem and the fixed point problem under some appropriate assumptions. Finally, we present a numerical example that satisfies the problem and shows the computational performance of our suggested technique.

Calorimetric studies of the crystallization process in a-Se75S25-xAgx chalcogenide glasses

Shamshad A. Khan,F.S. Al-Hazmi,A.S. Faidah,A.A. Al-Ghamdi 한국물리학회 2009 Current Applied Physics Vol.9 No.3

Calorimetric studies of amorphous Se75S25-xAgx (x = 2, 4, 6 and 8) chalcogenide glasses are made at different heating rates (5, 10, 15 and 20 K/min) under non-isothermal condition using Differential scanning calorimetry. The values of glass transition temperature and crystallization temperature are observed to be composition and heating rate dependence. From the heating rate dependence of glass transition temperature and crystallization temperature, the activation energy for structural relaxation (△Et), the activation energy of crystallization (△Ec) and the order parameter (n) have been calculated. It is observed that Se75S19Ag6 has a minimum value of activation energy for structural relaxation (△Et), which indicates that this particular glass has a larger probability to jump to a state of lower configurational energy and higher stability in the glassy region. On the basis of the obtained experimental data the temperature difference (Tc - Tg) is found to be maximum for Se75S19Ag6, which further indicate that this glass is the thermally most stable in the entire composition range of investigation. Calorimetric studies of amorphous Se75S25-xAgx (x = 2, 4, 6 and 8) chalcogenide glasses are made at different heating rates (5, 10, 15 and 20 K/min) under non-isothermal condition using Differential scanning calorimetry. The values of glass transition temperature and crystallization temperature are observed to be composition and heating rate dependence. From the heating rate dependence of glass transition temperature and crystallization temperature, the activation energy for structural relaxation (△Et), the activation energy of crystallization (△Ec) and the order parameter (n) have been calculated. It is observed that Se75S19Ag6 has a minimum value of activation energy for structural relaxation (△Et), which indicates that this particular glass has a larger probability to jump to a state of lower configurational energy and higher stability in the glassy region. On the basis of the obtained experimental data the temperature difference (Tc - Tg) is found to be maximum for Se75S19Ag6, which further indicate that this glass is the thermally most stable in the entire composition range of investigation.

Variant biochemical responses: intrinsic and adaptive system for ecologically different rice varieties

Shamshad Ul Haq,Deepa Kumari,Prerna Dhingra,S. L. Kothari,Sumita Kachhwaha 한국작물학회 2021 Journal of crop science and biotechnology Vol.24 No.3

India has a diverse range of agro-ecological conditions which support the cultivation of diferent rice varieties difering in the adaptation which is so important for sustainable development of rice crop. Specifc ecotypes of rice adapted to diverse conditions have divergence in their morphology, physiology, biochemistry, molecular function, agronomy, and stress response. In the present study, 12 diferent rice varieties viz., PB-1, PB-1509, Pusa-RH-10, CSR-30, HKR-47, PR-126, Govind, Sharbati, ADT-37, ADT-39, ADT-45, White Ponni, were selected for the study of intrinsic biochemical behaviour and these varieties belong to diferent Agro-ecological zones and basmati or non-basmati rice varieties. Amongst intrinsic biochemicals activity, the diferential response of radical scavenging, superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (POX) activities, were observed in the selected rice varieties at 14 days old seedling stage, developed under controlled growth conditions. Comparatively, North India region rice varieties displayed an enhanced intrinsic biochemical response than south India region rice varieties. Similarly, basmati rice varieties showed increased biochemical response compared to non-basmati rice varieties. Thus, the diferential biochemical responses (radical scavenging, SOD, CAT, and POX activities) observed creates a signifcant diference between rice varieties and provides valuable information about rice ecotype-biochemical interaction for sustainable adaptive value under diferent ecological conditions.

Development of Li₂O-SrO-GdF₃-B₂O₃ oxyfluoride glass for white light LED application

Shamshad, L.,Rooh, G.,Kirdsiri, K.,Srisittipokakun, N.,Kim, H.J.,Kaewkhao, J. Elsevier Scientific Pub. Co 2016 Journal of molecular structure Vol.1125 No.-

Dysprosium doped Li<SUB>2</SUB>O-SrO-GdF<SUB>3</SUB>-B<SUB>2</SUB>O<SUB>3</SUB> (LSGB) glasses were prepared by the conventional melt quenching technique in order to study the luminescence properties and their utility for white light emitting diodes (LEDs). The glass structure was studied by X-ray diffraction (XRD) and Fourier transform infra-red (FT-IR) spectroscopy. XRD confirmed the amorphous structure of the glass samples. The FT-IR spectra revealed the presence of BO<SUB>3</SUB>, BO<SUB>4</SUB> and non-bridging oxygen's. The optical absorption measurement were carried out in UV-VIS-NIR region. The PL emission and excitation spectra for the LSGB glasses were investigated. From the excitation and the emission spectra the highest Dy<SUP>3+</SUP> excitation and emission intensities was observed for 0.5 mol% Dy<SUP>3+</SUP>-doped oxyfluoride glass. Strong blue (482 nm) and yellow (575 nm) emission bands were observed upon various excitations. These two emissions corresponds to the (<SUP>4</SUP>F<SUB>9/2</SUB> → <SUP>6</SUP>H<SUB>15/2</SUB>) and (<SUP>4</SUP>F<SUB>9/2</SUB> → <SUP>6</SUP>H<SUB>13/2</SUB>) transitions of Dy<SUP>3+</SUP> ions, respectively. The blending of these blue and yellow bands gives white light. The CIE 1931 chromaticity coordinates for all the as made glass samples under various excitation wavelengths lies right in white region. The calculated correlated color temperature (CCT) values for the present oxyfluoride glasses were found in the range of 4336-4299 K. These were slightly more than warm CCT (i.e., CCT<4000 K) which lies in between those of fluorescent tube (3935 K) and day light (5500 K). These results reveals the possibility of the studied glasses to be used in various photonic devices for white light generation.