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Titanium dioxide fiber saturable absorber for Q-switched fiber laser generation in the 1-micrometer region (vol 58, pg 3495, 2019)
No full textThis publisher's note serves to correct an error inAppl. Opt. 58, 3495 (2019). (C) 2022 Optica Publishing Grou
Formulation and Development of Thermally Stable Boron and Fluorine Incorporated Antibacterial Bioactive Glasses
No full textSurface Engineered PLGA Nanoparticle for Threshold Responsive Glucose Monitoring and “Self-Programmed” Insulin Delivery
No full textWe have developed a reversible, biocompatible, “self-
programmed”PLGA [poly(lactic-co-glycolic acid)] nanoparticle-based optical biosensor capable of sensing and continuous monitoring of glucose above the physiologically relevant threshold value (100−125 mg/dL) as well as “on-demand”insulin delivery via an “On−Off” technique. We have carefully surface engineered the PLGA nanoparticle using amino dextran-fluorescein (A-DexFl) and amino-phenyl boronic
acid (A-PBA) to exploit the binding affinity of boronic acids with that of cis-1,2 diols of dextran/glucose. Initially, the dextran chains wrap the nanoparticle surface due to its high affinity toward A-PBA (Kb = 6.1 × 106 M−1). The close proximity of the fluorophores with that of A-PBA
quenches the fluorescence, resulting in an “Off”state. On the addition of glucose, it competes with A-DexFl to bind with A-PBA. Above a certain threshold concentration of glucose, the binding affinity overcomes (Kb = 6.3 ×107 M−1) the dextran-A-PBA binding. This opens-up the wrapped A-DexFl chains from the nanoparticle surface and results in an increased distance between the fluorophore and A-PBA, triggering the “On”state. The activation of the On−Offstate can be finely tuned in the desired range of physiologically
relevant glucose concentrations by varying the ligand ratios on the PLGA surface. The nanoparticle core has also been used as an insulin reservoir to trigger the drug release in the “On”state. We have obtained ∼53% encapsulation efficiency and ∼20% loading efficiency for insulin loading. Once the glucose concentration falls beyond the detection range, the dextran chains collapse on the nanoparticle surface with a suspension in drug release. The process is solely controlled by the competition and multivalent binding
affinity between glucose, A-DexFl, and A-PBA, which allows it to be “self-programmed”and “self-regulated” with continuous monitoring up to 8−10 cycles over a 72 h time period. A sustained drug release has been found with ∼70% of released drug over a period of 72 h, although this release is insignificant in the absence of glucose. Several control experiments have been performed to optimize the sensor design
Dopant-induced cationic bivalency in hierarchical antimony-doped tin oxide nano-particles for room-temperature SO2 sensing
No full textThe modification of simultaneously existing multiple oxidation states in host lattice cations via the introduction of dopants has been reported for NiO- and Co3O4-based gas-sensing materials. However, SnO2, a widely used material for chemiresistive gas sensing has never been reported with simultaneous presence of Sn2+ and Sn4+ states, in both the absence and presence of dopants. In this work, we demonstrated how antimony doping in a 3+ state triggers the generation of cationic bivalency in tin oxide-based gas sensors, and it is the quantitative presence of unstable Sn2+ species that determines the fate of SO2-sensing responses by antimony-doped tin oxide gas sensors. While the Sn2+ content in Sn0.856Sb0.144O2 is 1.2 times less than that of Sn0.957Sb0.043O2, the SO2 sensing response in the former is 1.2 times more than that in the latter. Greater antimony content in Sn0.856Sb0.144O2 also leads to the generation of additional trap states that result in sequential return of electrons back into the valence band. The reversibility of Sn2+ ↔ Sn4+ during SO2 adsorption and desorption brings out a new dimension of SnO2-based chemiresistors besides those already existing
Permeability and dust filtration behaviour of porous SiC ceramic candle filter
No full textPorous SiC candle filter (similar to 660 mm L and 75 mm OD) were fabricated by ramming process using commercially available SiC powder (d(50) = 212 mu m), with and without alumina and small amount (3 wt %) of clay as the major binder phase additives, following heat treatment at 1400 degrees C in air. Depending on the composition, porosity of the candle filters varied from 36 to 39 vol% and C-ring strength varied from 15 to 23 MPa. The air permeability and dust filtration efficiency of the candle filter were evaluated using laboratory made test set up. At room temperature, Darcian (k(1)) and non-Darcian (k(2)) permeability parameters varied from 1.9 to 2.2 x 10(-12) m(2) and 5.4-9.72 x 10(-8) m, respectively. Airborne fly ash particle filtration tests showed good performance of SiC candle filter with filtration efficiency of >97%. (C) 2020 Elsevier Ltd. All rights reserved
Effect of annealing on the defect-mediated blue phosphorescence in ZnO nanocrystals
No full textRecently, UV/NUV excitable RGB phosphors with precisely tunable PL emission properties have been in high demand for their suitability in the fabrication of white LEDs. In this paper, we report to have tuned the PL intensity, shade, and color temperature of the defect-mediated blue phosphorescence of ZnO nanopowders by systematic annealing at different temperatures. The ZnO nanopowder was prepared by a facile and cost-effective aqueous solution-precipitation method. The as-synthesized nanopowder was annealed at different temperatures ranging from 150 degrees C to 850 degrees C and all these samples were characterized by XRD, FESEM, EDX, BET, Raman spectroscopy, and UV-Vis spectroscopy to have insight into their microstructural, compositional, and band-structure details. Optical studies of the samples were conducted by PL and tau-PL spectroscopy. Color coordinates of the samples were obtained from the CIE plots derived from the PL spectra. The CIE coordinates were further used to calculate the CCT values of the samples. tau-PL spectroscopy was carried out to measure the life-time of the photogenerated electrons. PL studies of the samples revealed that the blue emissions have red, yellow, and blue components originating from crystalline point defects, viz. zinc interstitial (Zn-i), and oxygen interstitial (O-i). Annealing at different temperatures triggered changes in the defect concentrations leading to the corresponding changes in the intensity, shade, and color temperature of the blue phosphorescence
A New Functional Composite for Photovoltaic and Sensor Applications
No full textAs a preliminary drive to eventually develop dye-sensitized solar cell (DSSC)-powered gas sensors, many oxide-based systems have been explored to fabricate sensors that can show response at room temperature for any analyte gas. As an outcome of recent work in this endeavor, a composite nanorod of anatase TiO2 with Na0.23TiO2 is found to exhibit both photovoltaic performance and gas sensing at room temperature as demonstrated here. An interesting morphology change along with a phase change from nanoparticle to nanorod is observed during the hydrothermal synthesis of anatase TiO2 nanoparticles with sodium hydroxide under a highly basic condition. In order to understand the effect of the minor phase Na0.23TiO2 on the inherent properties of anatase TiO2, the application of nanorod composite in two unique potential application areas, DSSC and acetone sensings is investigated. The composite material exhibits an enhanced efficiency of 7.85% for a DSSC. Surprisingly, a resistive sensor fabricated with the synthesized composite material exhibits room temperature p-type sensing behavior toward different concentrations of acetone (10, 5, 3, 2, and 1 ppm) with high selectivity
Synthesis and characterization of Tm2O3-doped Lu2O3 nanoparticle suitable for fabrication of thulium-doped laser fiber
No full textSynthesis of Tm2O3-doped Lu2O3 nanoparticle using homogeneous co-precipitation method along with its material/optical characterization is reported. Four different compositions with variation of Tm: Lu ratios are synthesized followed by calcination at different temperatures (800, 1000 and 1200 degrees C) was performed to optimize the synthesis process as well as composition. The XRD analysis indicates steady growth of particle size with increasing calcination temperature and an average particle size of 100 nm was achieved at 1200 degrees C. Pure bixbyite structure was observed for every sample independent of Tm: Lu ratio. The FESEM and HRTEM analysis associated with EDX indicates formation of pure crystalline particles and results are in good agreement with XRD analysis. The photoluminescence spectra observed under 808 nm excitation exhibit characteristic Tm emission peak that extended beyond 2 micron region the intensity of which is strongly depends on Lu: Tm ratio as well as calcination temperature. The overall result reveals that the synthesized material which indicates good thermal stability is a potential doping material for the development of Thulium-doped fiber suitable for eye-safe laser application
Removal of cadmium by in-situ Cu nanoparticle enhanced ceramic-supported-polymeric composite NF membrane
No full textA novel ceramic-polymer composite nanofiltration membrane was fabricated using in-situ generated Cu nanoparticles by dip coating over modified ceramic support tube. The prepared membrane was used for Cd (II) removal from contaminated water. Generation of in-situ Cu NPs on/in the membrane was characterized by SEM and XPS analysis. Incorporation of NPs formed by in-situ chemical reduction technique improved the pore size of modified ceramic substrate towards NF range (similar to 1 nm). The positively charged composite NF membrane exhibited satisfactory performance with respect to pure water permeability (8.09 L m(-2) h(-1) bar(-1)) and Cd(II) rejection of 95.5%. (C) 2021 Elsevier Ltd. All rights reserved
Microstructure-mechanical properties of Ag-0/Au-0 doped K-Mg-Al-Si-O-F glass-ceramics
No full textIn understanding the catalytic efficacy of silver (Ag-0) and gold (Au-0) nanoparticles (NPs) on glass-ceramic (GC) crystallization, the microstructure-machinability correlation of a SiO2-MgO-Al2O3-B2O3-K2O-MgF2 system is studied. The thermal parameters viz., glass transition temperature (T-g) and crystallization temperature (T-c) were extensively changed by varying NPs (in situ or ex situ). Tc was found to be increased (T-c = 870-875 degrees C) by 90-110 degrees C when ex situ NPs were present in the glass system. Under controlled heat-treatment at 950 +/- 10 degrees C, the glasses were converted into glass-ceramics with the predominant presence of crystalline phase (XRD) fluorophlogopite mica, KMg3(AlSi3O10)F-2]. Along with the secondary phase enstatite (MgSiO3), the presence of Ag and Au particles (FCC system) were identified by XRD. A microstructure containing spherical crystallite precipitates (similar to 50-400 nm) has been observed through FESEM in in situ doped GCs. An ex situ Ag doped GC matrix composed of rock-like and plate-like crystallites mostly of size 1-3 mu m ensured its superior machinability. Vicker's and Knoop microhardness of in situ doped GCs were estimated within the range 4.45-4.61 GPa which is reduced to 4.21-4.34 GPa in the ex situ Ag system. Machinability of GCs was found to be in the order, ex situ Ag > ex situ Au similar to in situ Ag > in situ Au. Thus, the ex situ Ag/Au doped SiO2-MgO-Al2O3-B2O3-K2O-MgF2 GC has potential for use as a machinable glass-ceramic