Synthesis and luminescence properties of Na+, Li+ compensated Er3+ doped CaAl4O7 phosphors

Here the green-emitting highly luminescent Er³⁺ doped, Er³⁺-Li⁺ co-doped, Er³⁺-Na⁺ co-doped CaAl₄O₇ is synthesized by Pechini method at 1000^°C. Photoluminescence (PL) of CaAl₄O₇: Er³⁺ studies have been compared with Li⁺ co-doped CaAl₄O₇: Er³⁺ and Na⁺ co-doped CaAl₄O₇: Er³⁺. Na⁺ co-doped CaAl₄O₇:Er³⁺ shows increases in luminescence intensity compared to Li⁺ co-doped CaAl₄O₇: Er³⁺ and Er³⁺ doped CaAl₄O_7. The results suggest that CaAl₄O₇:Er³⁺ phosphor can be used as efficient green-emitting phosphor in white LED. The resultant phosphor emits green color peaking at 549 nm upon 378 nm excitation. Powder X-ray diffraction (PXRD) and photoluminescence (PL) techniques have been studied to characterize the synthesized microparticles. Further, this phosphor has good thermal stability that implies its potential to act as green phosphor in white light-emitting diodes. The effect of activator (Er³⁺), Na⁺ co-doped CaAl₄O₇:Er³⁺, and Li⁺ co-doped CaAl₄O₇:Er³⁺ phosphors luminescence spectra as well as photoluminescence life time studies were studied in detail. The results show that as the concentration of Er³⁺ in CaAl₄O₇ increases, the symmetry around the Er³⁺ ion decreases due to the creation of lattice defects in the crystal. Addition of Na⁺ and Li⁺ ions in CaAl₄O₇: Er³⁺leads to a small distortion in the local symmetry of Er³⁺ ions, thereby significantly enhancing its luminescence property. Analysis of photoluminescence life time studies of the prepared samples shows a smaller concentration quenching of Er³⁺ luminescence in charge compensated Na⁺ and Li⁺ CaAl₄O₇ phosphor.

     

Synthesis and characterization of ZnS-based quantum dots to trace low concentration of ammonia

In the present work,a solution-based co-precipitation method has been adopted to synthesize pure and cobalt-doped ZnS quantum dots and characterized by XRD,SEM,TEM with EDX,FTIR and gas sensing properties.XRD analysis has shown a single phase of ZnS quantum dots having a zinc blend structure.TEM and XRD line broadening indicated that the aver-age crystallite size in the sample is in the range of 2 to 5 nm.SEM micrographs show spherical-shaped quantum dots.FTIR stud-ies show that cobalt has been successfully doped into the ZnS cubic lattice.EDX spectra have analyzed the elemental pres-ence in the samples and it is evident that the spectra confirmed the presence of cobalt (Co),zinc (Zn),oxygen (O),and sulphur(S) elements only and no other impurities are observed.The ZnS-based quantum dot sensors reveal high sensitivity towards 50 ppm of ammonia vapors at an operating temperature of 70 ℃.Hence,ZnS-based quantum dots can be a promising and quick traceable sensor towards ammonia sensing applications with good response and recovery time.     

Synthesis and Polymerization of Bismaleimide Derived from 5(6)-amino-1(4′-aminophenyl)-1,3,3′-trimethyl indane

The acid-catalyzed dimerization of α-methyl styrene led to the formation of trimethyl phenyl indane, which on nitration followed by reduction using hydrazine hydrate gave 5(6)-amino-1(4′-aminophenyl)-1,3,3′-trimethyl indane. This aromatic diamine was used to synthesize bismaleamic acid and imidized to yield bismaleimide. The bismaleamic acid was converted to prepolymer directly by imidizing it in refluxing toluene. All the materials synthesized were characterized using FTIR, ¹H and ¹³C NMR. The direct inlet mass spectral characterizations were carried out for bismaleamic acid, bismaleimide and bismaleimide prepolymer. The fragmentation pattern was discussed in detail and the structure proposed was confirmed. The thermogravimetric studies were done for all the materials and kinetic parameters (energy of activation and frequency factor) were calculated using Dharwadkar and Kharkhanavala method. The structural changes occurring in the thermally polymerized bismaleimide and bismaleimide prepolymer were discussed.     

CuInS2/In2S3 thin film solar cell using spray pyrolysis technique having 9.5% efficiency

Copper indium sulfide (CuInS₂)/In₂S₃ solar cells were fabricated using spray pyrolysis method and high short circuit current density and moderate open circuit voltage were obtained by adjusting the condition of deposition and thickness of both the layers. Consequently, a relatively high efficiency of 9.5% (active area) was obtained without any anti-reflection coating. The cell structure was ITO/CuInS₂/In₂S₃/Ag. We avoided the usual cyanide etching and CdS buffer layer, both toxic, for the fabrication of the cell.     

Experimental Verification of Photovoltaic-based Three-phase Four-wire Series Hybrid Active Power Filter

Abstract—This article proposes a photovoltaic and battery interfaced series hybrid active power filter, which is comprised of a series active power filter and an inductor-capacitor (LC) shunt passive filter. The main benefits of the proposed system provide the compensation against the voltage harmonics, current harmonics, and voltage interruption for the whole day. A series active power filter demands a source of energy for compensating the voltage sag/swell. The proposed topology utilizes the green energy source with an energy storage unit to meet the DC-link voltage requirement of the series active power filter. The control strategy is based on the dual formulation of the compensation system principles with adaptive fuzzy logic controller. The simulation and experimental studies are carried out to validate the effectiveness of the proposed photovoltaic interfaced three-phase four-wire series hybrid active power filter.