IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Large room-temperature magnetodielectric effect in polyvinylidene fluoride-trifluoroethylene/La0.7Sr0.3MnO3 (0-3) nanocomposite thin films
No full textWe observe large room-temperature magnetodielectric effect (nearly 12% suppression of dielectric constant under similar to 20 kOe field) as well as its remarkable field-driven switch - from positive to negative - in polyvinyli-dene fluoride-trifluoroethylene/La0.7Sr0.3MnO3 (PVDF-TrFE/LSMO) thin films (0-3 connectivity) containing 7.5 volume% LSMO. The magnetodielectric effect is mapped with the volume fraction of the LSMO nanoparticle across 5-20 volume%. It reveals a close correlation among the LSMO nanoparticles volume fraction, their distribution pattern within the PVDF-TrFE matrix, uniformity in the magnetic domain size (imaged by magnetic force microscopy), and the magnetodielectric effect. The observed 20% jump in the intrinsic bulk capacitance at a critical magnetic field H, similar to 10 kOe can be exploited to develop smart nanoscale magnetoelectric devices
Band-structure tunability via the modulation of excitons in semiconductor nanostructures: manifestation in photocatalytic fuel generation
No full textUnderstanding the energetics of electron transfer at the semiconductor interface is crucial for the development of solar harvesting technologies, including photovoltaics, photocatalysis, and solar fuel systems. However, modern artificial photosynthetic materials are not efficient and limited by their fast charge recombination with high binding energy of excitons. Hence, reducing the exciton binding energy can increase the generation of charge carriers, which improve the photocatalytic activities. Extensive research has been dedicated to improving the exciton dissociation efficiency through rational semiconductor design via heteroatom doping, vacancy engineering, the construction of heterostructures, and donor-pi-acceptor (D-pi-A) interfaces to extend the charge carrier migration, promoting the dissociation of excitons. Consequently, functionalized photocatalysts have demonstrated remarkable photocatalytic performances for solar fuel production under visible light irradiation. This review provides the fundamental aspects of excitons in semiconductor nanostructures, having a high binding energy and ultrafast exciton formation together with promising photo-redox properties for solar to fuel conversion application. In particular, this review highlights the significant role of the excitonic effect in the photocatalytic activity of newly developed functional materials and the underlying mechanistic insight for tuning the performance of nanostructured semiconductor photocatalysts for water splitting, CO2 reduction, and N-2 fixation reactions
Bimetallic metal-organic frameworks for efficient visible-light-driven photocatalytic CO2 reduction and H2 generation
No full textA series of robust octahedral bimetallic metal-organic frameworks, NH2-UiO-66(Zr/M), denoted as Zr/M-ATA, (where M is Fe, Co, or Cu) were prepared by solvothermal de novo reaction of 2-aminoterephthalic acid (denoted as H2ATA) and mixed metal salts using benzoic acid as a modulator. Photocatalytic studies revealed that Zr/Fe-ATA, Zr/Cu-ATA and Zr/Co-ATA containing double metals outperformed that of the monometallic Zr-ATA. Zr/Cu-ATA displayed excellent performance for visible-light-driven CO2 reduction with a formate forma-tion rate of 122 mu mol h-1 mmolMOF-1 , which is among the highest performance of NH2-UiO-66 based MOFs. Furthermore, Zr/Cu-ATA is an efficient catalyst that can generate 12.8 mmol of H2 in 2 h under visible light irradiation. The light absorption band of Zr/Cu-ATA shifted to the near-IR region and the presence of Cu-oxo clusters significantly narrowed the bandgap from 2.95 eV (Zr-ATA) to 1.93 eV (Zr/Cu-ATA). Other photo -electrochemical studies further confirmed that the high catalytic performance of Zr/Cu-ATA can be ascribed to optimized bandgap, facile charge transfer and availability of large number of active sites
Barium titanate based paraelectric material incorporated Poly(vinylidene fluoride) for biomechanical energy harvesting and self-powered mechanosensing
No full textBeing a superior dielectric material exhibiting low loss, x = 0.4 composition of Ba1-xSrxTiO3 nanoparticles have been widely used as fillers in poly(vinylidene fluoride) (PVDF) for efficient flexible dielectric and electrical energy storage application. The mentioned composition of the material is also very attractive choice of interest to the researchers due to its ability of ferroelectric to paraelectric phase transition. Due to its paraelectric nature, Ba0.6Sr0.4TiO3 has not been used for mechanical energy harvesting application till date. Here we have used Ba0.6Sr0.4TiO3 particles as fillers in PVDF matrix for efficient mechanical energy harvesting purpose. In the present work, along with the flexible dielectric, ferroelectric and energy storage applications, the developed composite films have been explicitly used for efficient biomechanical energy harvesting, powering small elec-tronic devices and pressure sensing. The fabricated nanogenerator successfully generated a maximum output voltage and output power density of 15 V and 6.75 mu W/cm2 respectively on repeated human finger tapping. The obtained output power has been clearly explained on the basis of polar phase formation and consideration of stress concentration effect
Air-plasma discharged PVDF based binary magnetoelectric composite for simultaneously enhanced energy storage and conversion efficiency
No full textDifferent nanomaterials and their modified forms are very often added into a poly(vinylidene fluoride) (PVDF) matrix in order to improve the energy storage and conversion efficiency of the system. The improvement in energy storage density caused by this secondary nanomaterial addition is most often found to be accompanied by the reduction in energy storage efficiency due to increased amounts of space charges. Here, we show that both the capacitive energy storage density and efficiency can be simultaneously improved by air-plasma discharging on the PVDF based composite system. The energy storage density and efficiency of a 5 wt. % BiFeO3 loaded PVDF film (5BF) have been found to be increased to similar to 1.55 J/cm(3) and similar to 73%, respectively, from the values of similar to 1.36 J/cm(3) and 59% after air-plasma discharging. The dipole rotation caused by air-plasma discharging also helped in improving the mechanical to electrical energy conversion efficiency and magnetoelectric coupling of the studied composite system. Upon similar periodic applied stress, the pristine and air-plasma discharged 5BF film showed similar to 3 and 9.6 mu W/cm(2) of output electrical power density with similar to 13.5 and 19.2 V of open circuit output voltage, respectively. The air-plasma discharged 5BF film (5BFD) has also shown an excellent magnetoelectric coupling coefficient (alpha(33)) of similar to 35 mV cm(-1) Oe(-1) at 1 kHz frequency of fixed AC magnetic field (similar to 3 Oe) and 4 kOe of DC bias field. The simultaneous improvement of all of these parameters of the studied composite system caused by air-plasma discharging proves its multifunctional applicability in a variety of real life applications
Synergistic improvement of antibacterial, mechanical and degradation properties of Cu added Mg-Zn-Zr alloy
No full textPresent study is focused on synergistic improvement of antibacterial properties along with mechanical as well as corrosion properties of Mg-5Zn-0.5Zr-0.7Cu alloy through alloying and thermomechanical processing. Detailed microstructural analysis and textural study showed significant increase in grain refinement through dynamic recrystallization and basal-texture strengthening after forging. As a result, 1.2 times improvement of strength and 2.3 times reduction in in vitro degradation rate were observed. Complete mitigation of E.Coli bacteria was noticed within 32 h of culture for both the alloys due to addition of Cu. In addition, non-toxic nature of the alloys was proven from the cell viability studies, suggesting that Mg-5Zn-0.5Zr-0.7Cu alloy has the potential to be used as internal fracture-fixation material
Long-Period Fiber Grating Probe: An Improved Design Suitable for Biosensing
No full textAdd-layer sensitivity of long-period fiber grating (LPFG) near mode transition (MT) has been studied in reflection configuration to realize a highly sensitive LPFG-based sensor probe suitable for biosensing. The dependency of the sensitivity on the separation between the resonant cladding modes considered during MT has also been investigated. The separation between two consecutive cladding modes was precisely increased or stretched to a desired value by reducing the cladding diameter. The probe was formed by cleaving the mode stretched LPFG (MSLPFG) through the grating region. The MSLPFG was designed to operate near MT by deposition of electrostatic self-assembled (ESA) polymeric overlay layers on the grating surface. We demonstrate that the polymeric overlay not only increases the sensitivity of the sensor but also eliminates undesirable multiple resonant bands that appear due to the introduction of arbitrary phase while cleaving the grating. Add-layer sensitivity of the MSLPFG sensor probe was obtained and found to be similar to 2.0 nmWL/nmTH with a significantly enhanced peak attenuation of similar to -30 dB around the MT region
Copper ferrite inverse spinel-based highly sensitive and selective chemiresistive gas sensor for the detection of formalin adulteration in fish
No full textThe unexpected presence of food preservatives such as formalin in food can cause significant health hazards e.g., severe damage to the pulmonary and nervous system, kidney, lungs, eyes, etc. In this work, semi-conducting Copper ferrite (CuFe2O4) inverse spinel nanoparticles-based gas sensor for the detection of formalin adulteration in fish has been reported. The nanopowder was synthesized by a simple sol-gel route. The nanopowder was characterized by multiple sophisticated techniques, viz., XRD, XPS, FESEM, TEM, EDS, UV-Vis spectroscopy, laser diffraction-based particle size distribution measurement, current-Voltage (I-V) measurement, infra-red imaging, and non-contact optical profilometry. The developed sensor exhibits high p-type sensitivity towards trace formalin gas (5-30 ppm), rapid response (-2.7 s) and recovery times (-34 s), and appreciable selectivity with respect to other gases in trace concentrations, such as acetone, ethanol etc., and saturated moisture at moderate operating temperature (260 & DEG;C). The excellent long-term stability of the sensor for at least 6 months renders it suitable for commercial applications. & COPY; 2023 Elsevier B.V. All rights reserved
Self-Powered Photodetector Fabricated from a Single-Charge-Transfer Complex Nanowire Grown In Situ between Prefabricated Electrodes on an Si3N4 Membrane
No full textPower consumption in an electronic circuit is one ofthe seriouschallenges that need to be improved to achieve a durable future. Aphotodetector is one such electronic device that consumes a huge externalpower to operate. This motivated the researchers to concentrate onself-powered optical photodetectors that can operate without externalbias. On the contrary, building a device on a transparent film ornanomembrane has great importance in the field of electronic skins,and lightweight and intelligent wearables technology. Here, we havereported the fabrication and characterization of a self-power opticalphotodetector device based on a single Cu:7,7,8,8-tetracyanoquinodimethanenanowire (Cu:TCNQ NW) of length & SIM;500 nm and diameter & SIM;50nm. The NW photodetector device was fabricated on a silicon nitride(Si3N4) membrane window (size = 100 & mu;mx 100 & mu;m, membrane thickness & SIM;100 nm) to meet thedemands of a lightweight and transparent technology. The reportedself-powered single-NW photodetector exhibits excellent photoresponsivity(& SIM;5.5 A/W), high detectivity (& SIM; 7 x 10(7) Jones), outstanding external quantum efficiency (& SIM;1.6 x10(3)%), and a large on/off current ratio (& SIM;1.5 x10(2)) at 49 nW optical power. The analysis reveals thatthe contribution is due to photocarrier generation, radial built-in-fieldon the NW's surface, and barrier height reduction during illumination.Self-powered optical photodetectors, in particular, have enormouspotential as novel emerging self-driven optoelectronic devices
Properties and performance of cordierite-bonded porous silicon carbide membrane prepared using waste fly ash and other oxide additives
No full textThe low-cost cordierite-bonded porous SiC ceramic membranes were successfully synthesized at 1300 & DEG;C for 1 h in the air by in-situ solid-state reactions of SiC with a mixture of fly ash, & alpha;-Al2O3 and MgO (FAM). The effects of sintering temperature and FAM content on porosity, mechanical strength, phase compositions, microstructure and permeability were carefully investigated. The ceramics prepared at 1300 & DEG;C with a 20 wt% FAM mixture showed a very high mechanical strength of 85.8 MPa at a porosity of 28 vol%. The addition of pore former effectively improved the porosity and permeability properties without significantly degradation of mechanical strength. The membrane exhibited 98.4% oil removal efficiency from synthetic oil-water emulsion (1000 mg l(-1)), which suggests that the membranes are suitable for oil-water separation and other microfiltration applications. The use of fly ash successfully reduced the sintering temperature for the fabrication of ceramic membranes and provided an efficient way of utilizing waste resources