IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Investigation of giant dielectric and room temperature ferromagnetic response of facile CZTO nanostructure
No full textCubic CoZnTiO4 (CZTO) nanocomposite structure has been synthesized via a modest chemical method at a much lower calcination temperature. The possible phase formations and crystalline nature of the as synthesized structure has been studied by X-ray diffraction technique. FESEM micrographs depict the grain growth within the nanocomposite. Thermal analysis shows endothermic as well as exothermic peaks which points out the thermal stability over the observed temperature range. The synthesized CZTO nanocomposite structure shows nearly frequency independent giant dielectric response on application of external electric field. The nanostructure shows epsilon' similar to 21,000 at 40 Hz frequency. With the help of internal barrier layer capacitor model, the origin of this large dielectric constant is well explained. The impedance spectroscopy analysis and equivalent circuit response also supports the obtained result. On application of external magnetic field, the synthesized CZTO sample also shows room temperature ferromagnetic response. This magneto-dielectric response of CZTO nanostructure enables it to be a superior material for forthcoming device application
Enhanced luminescence at 2.88 and 2.04 mu m from Ho3+/Yb3+ codoped low phonon energy TeO2-TiO2-La2O3 glass
No full textThe high phonon energy and short infrared cut-off wavelength of conventional oxide glass (or crystal) hosts are the limitations to achieve mid-infrared (MIR, ?=2.5 mu m) luminescence. In present study, the luminescence performance of low phonon and non-conventional TeO2-TiO2-La2O3-based glass (TTL) host doped with Ho3+ and Ho3+/Yb3+ has been investigated, for visible to MIR range. The MIR emission band with peak at 2.88 mu m (Ho3+:I-5(6)-> I-5(7)) and NIR band at 2.04 mu m (Ho3+:I-5(7)-> I-5(8)) has been realized from Ho3+ singly doped TTL glass due to low phonon energy and extended transmission window of the host. Intensity of MIR and NIR emission bands have enhanced significantly in Ho3+/Yb3+: TTL glass under Yb3+ excitation, signifying an efficient Yb3+?Ho3+ energy transfer. The Judd-Ofelt analysis, on Ho3+ absorption characteristics reveals relatively better radiative transition probability (34.4s(-1)) and branching ratio (10.5%), which is associated to Ho3+:I-5(6)-> I-5(7) transition. The effective bandwidth of 2.88 mu m emission band is 180nm, with stimulated emission cross-section is 4.26x10-21cm(2) and its gain bandwidth has been evaluated as 7.67x10-26cm(.) For 2.04 mu m (Ho3+:5I7?5I8) emission band, the effective bandwidth of 160.5nm and gain bandwidth of 7.26x10-26cm3 have been accomplished. The non-resonant Forster-Dexter method has been applied to Ho3+/Yb3+: TTL glass on emission (donor, Yb3+) and absorption (acceptor, Ho3+) cross sections. The evaluated donor-donor (CDD) and donor-acceptor (CDA) energy transfer micro-parameters are 1.02x10-38 and 5.88x10-41cm6/s respectively while, maximum energy transfer efficiency has been 80%. In concise, Ho3+/Yb3+ codoped TeO2-TiO2-La2O3 glass host has revealed its potential for MIR to NIR photonic applications. (C) 2019 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)
Structural and Femtosecond Third-Order Nonlinear Optical Properties of Sodium Borate Oxide Glasses: Effect of Antimony
No full textStructural and optical properties of antimony-containing sodium borate glasses were studied and their ultrafast third-order nonlinear optical (NLO) properties have been evaluated using Z-scan measurements with femtosecond (fs) pulses (similar to 150 fs, 80 MHz) at 750, 800, and 880 nm wavelengths. Glasses in the (mol %) 20Na(2)O (80 - x)B2O3 - xSb(2)O(3) (where x = 0, 10, 20, and 30) system have been fabricated via melt quench technique. The structural modifications were analyzed using the Raman and magic angle spinning (MAS)-nuclear magnetic resonance (NMR) (B-11 MAS-NMR and Na-23 MAS-NMR) techniques. The optical absorption spectra revealed that the absorption edge was red-shifted, suggesting the decrease in band gap energy with increase of antimony content in the glasses. Raman scattering results revealed that the boroxol rings are depressed with the incorporation of Sb2O3 for replacing B2O3. B-11 MAS-NMR results showed a progressive increase of B-4 units at the expense of B-3 units. The Raman and B-11 MAS-NMR results support the formation of Sb5+ ions due to oxidation of Sb3+ that played the role of charge compensation. Na-23 MAS-NMR spectra revealed a decreasing trend in the average of bond lengths of Na-O with increasing Sb2O3 contents. This suggested that sodium changed its role from charge compensator to modifier cation. The antimony-containing glasses demonstrated a reverse saturable absorption in open-aperture Z-scan mode due to two-photon absorption, while closed-aperture Z-scan signatures depicted positive nonlinear refraction due to self-focusing effect. The NLO coefficients were found to increase with Sb2O3 due to the increased nonbridging oxygens and also due to the hyperpolarizability of Sb3+ and Sb5+ ions. The observed NLO data clearly suggest that the investigated glasses are beneficial for optical limiting applications
How Does ``Wormhole'' Mesoporous gamma-Alumina Matrix Direct the Morphology of Pt Nanocrystals?
No full textThis study demonstrates experimental evidence of formation of different discrete shaped Pt nanocrystals inside a mesoporous gamma-alumina film at 500 degrees C. Shape and size of the finally formed nanocrystals are found to be dependent on the concentration of surfactant used to form the porous structure, as well as the precursor salt solution. Electron microscopic characterization at different temperature intervals during the growth of nanocrystals reveals the nucleation of small nanoparticles and their clustering and growth toward the formation of pyramidal, rhombus, cuboid, and bean-shaped nanocrystals in the mesoporous alumina matrix. The study finds that ``wormhole'' type mesoporous gamma-alumina is the key medium for the generation of these nanostructures which are not formed while using hexagonally ordered mesoporous alumina. From the experimental evidence, we attempted to understand the formation mechanism of Pt nanocrystals in the mesoporous gamma-alumina film matrix. This study is expected to open up new direction in the shape- and size-controlled synthesis of nanoparticles inside a mesoporous support matrix
First principles study of Ag absorption mechanism in amorphous large silica clusters
No full textAg nanoparticles cause interesting modifications to the electronic and optical properties of amorphous silica scaffold that is used in optical fibers. The present study is first of its kind to implement first principles based calculation of large amorphous dielectric host with metal inclusions in it. Ground state structural parameters and equilibrium geometries of amorphous (SiO2)(n) clusters (n = 8,16,24,32,40) with Ag atoms doped inside the interstitial space of the scaffold have been calculated using DMol(3) DFT program. We have shown that the configuration of small Ag clusters depend strongly on the structural characteristics of the scaffold. This creates a unique opportunity to control the microscopic properties of small metal clusters via Ag impregnation. Our study reveals that small sized silica clusters have lower level of absorption due to self-purification effect and Ag absorption efficiency depends on the nature of amorphicity of clusters having different geometries but same number of atoms. The nature of amorphicity of two different geometries of equal sized silica clusters has been verified via two independent approaches viz. (a) pair correlation and bond length/angle distributions plot of Si atoms and (b) the quasi-entropy calculated using USPEX code. More amorphous network of host leads to incorporation of more number of Ag atoms. The effect of host silica matrix on the structures of Ag nanoclusters are evaluated and the results show that bond distances in Ag clusters increase when encapsulated in silica matrix. The effect of doped Ag atoms on the structural characteristics of silica clusters are also evaluated and correlated with the shift in frequencies and change in Raman spectral intensities
Superior energy storage performance and fatigue resistance in ferroelectric BCZT thin films grown in an oxygen-rich atmosphere
No full textFerroelectric properties of chemical-solution-deposited Ba0.85Ca0.15Ti0.90Zr0.10O3 (BCZT) thin films in the 200 nm thickness range, grown in air and oxygen-rich atmospheres, were investigated. Oxygen-processed BCZT thin films were found to have very slim hysteresis with higher polarization, lower remanent polarization (P-r), much lower coercivity and much higher dielectric breakdown strength. Those properties resulted in superior energy storage properties. Oxygen-processed BCZT thin films showed an energy storage density (ESD) of 64.8 J cm(-3) and energy storage efficiency (ESF) of 73% at 2000 kV cm(-1) electric field. Apart from that, the films showed very low leakage current and improved polarization fatigue properties. Oxygen-processed virgin BCZT film displayed maximum polarization (P-max) of 106 mu C cm(-2) and P-r of 12.9 mu C cm(-2), whereas the measured P-max and P-r of the fatigued film after 10(10) switching cycles were 105 mu C cm(-2) and 13.2 mu C cm(-2) respectively. BCZT thin films with high ESD and ESF at 2000 kV cm(-1) electric field and with excellent fatigue properties could be considered as potential candidates for low and intermediate voltage ferroelectric energy storage applications
Surface properties and cytocompatibility of Ti-6Al-4V fabricated using Laser Engineered Net Shaping
No full textDirect laser deposition (DLD) is one of the rapidly emerging laser-based additive manufacturing (LBAM) process. Laser Engineered Net Shaping (LENS) is one such DLD technique which was employed to fabricate one of the widely used Ti-6Al-4V implant material with enhanced surface-related properties compared to the wrought sample (commercially available). Wear and corrosion behavior of LENS fabricated Ti-6Al-4V (L-Ti64) was characterized using low-frequency reciprocatory wear tester and potentiostat. Sample hardness was determined using Vickers's microhardness test. Adhesion and morphology of Human mesenchymal stem cells (hMSCs) on the samples were examined using Scanning Electron Microscopy (SEM) and fluorescence microscope whereas the quantification of live cells was determined using MIT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) was used to determine the concentration of leached-out metal ions during wear test. All the above mentioned surface-related properties were compared to that of wrought Ti-6Al-4V (W-Ti64) to standardize the efficiency of LENS-fabricated materials (L-Ti64) when compared to its wrought counterpart. The results clearly indicated stable passive behavior of L-Ti64, which was evident from the lower corrosion rate and high passive range obtained. L-Ti64 exhibited improved hardness level than W-Ti64 by 8% which enhanced the wear resistance and also prevented the release of wear debris. However, in presence of FBS, coefficient of friction (COF) increased by about 21 and 33% for L-Ti64 and W-Ti64 respectively, which inturn accelerated the wear rate of both the samples. Low cytotoxicity and well spread morphology of human Mesenchymal Stem Cells (hMSC's) affirmed higher level of biocompatibility of both the samples. However, no significant differences in the cellular behaviors were observed
Au nanoparticle-decorated aragonite microdumbbells for enhanced antibacterial and anticancer activities
No full textThe present work reports the very first hydrothermal synthesis of 100% triclinic phase pure aragonite (A1) with microdumbbell microstructural architecture and Au Nanoparticle-decorated (AuNP-decorated) aragonites (A2, A3 and A4) with spherical, pentagonal/hexagonal and agglomerated AuNP-decorated microdumbbells having triclinic aragonite phase as the major and cubic AuNPs as the minor phase. Even in dark the AuNP-decorated aragonites (especially A2) show efficacies as high 90% against gram-negative e.g., Pseudomonas putida (P. putida) bacteria. Further the AuNP-decorated aragonites (A3) show anti-biofilm capability of as high as about 20% against P. putida. Most importantly the AuNP-decorated aragonites (A3) offer anti-cancer efficacy of as high as 53% while those of A1, A2, and A4 are e.g., 26%, 46% and 37%, respectively. For the very first time, based on detailed investigations, the mechanisms behind such advance antibiofilm and anticancer activities are linked to the generation of excess labile toxic reactive oxygen species (ROS). Thus, these materials show enormous potential as futuristic, multi-functional biomaterials for anti-bacterial, anti-biofilm and anti-cancer applications
Intercalation of LDH NO3 with short-chain intercalants
No full textIntercalation behaviour of layered-double hydroxide (LDH) with short-chain intercalants (-(CH2)n-,nnH2O,] by an ion-exchange intercalation technique in a slightly acidic medium (pH=5.4). The adverse effect of a carbonate anion was avoided by performing the ion-exchange intercalation in slightly acidic medium (pH=5.4). It was found that basal spacing (d003) and experimental organic loading of intercalated LDH (O-LDH) increase monotonically with increasing anion-exchange capacity of LDH and intercalant chain length. The evolution of intercalated LDH (O-LDH) structures with increasing intercalant chain length and layered charge has been deciphered by correlating basal spacing of O-LDHs (by X-ray powder diffraction), organic loading data (by thermogravimetric analysis) and molecular conformation of O-LDHs (by Fourier-transform infrared spectroscopy) within the LDH gallery. Successful intercalation of LDH with these short-chain intercalants in slightly acidic medium has not been reported previously
Intercalation of shRNA-plasmid in Mg-Al layered double hydroxide nanoparticles and its cellular internalization for possible treatment of neurodegenerative diseases
No full textIn the present work, nanoconjugates of shRNA-plasmid and a non-viral nanoceramic vector, e.g., Mg-Al layered double hydroxide (Mg-Al LDH), were synthesized and intercalated. Subsequently, these particles with an average size of 40-60 nm, were transfected into mammalian neuroblastoma cells (SH-SY5Y). The as prepared Mg-Al LDH was able to protect the incorporated shRNA-plasmid against a range of pH values, DNaseI, endonucleases, and serum components. To test the applicability of the nanoconjugate for future in-vivo studies, serum from three different model experimental animals viz, mouse, rat and guinea pig was used for the serum protection study. Additionally, we showed that prolonged storage at different temperatures does not affect the quality of the nanoconjugate. Using this nanoconjugate to transform cells, a maximum internalization of similar to 26% at 24h was achieved. Lastly, we demonstrated effective and safe delivery of the plasmid by measuring GFP production and shRNA-induced knockdown of TNF alpha