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Structural and luminescence studies of Sm3+:CaLa4Si3O13 phosphors: An orange-emitting component for WLEDs application
摘要： With the help of the conventional sol-gel process, six different concentrations of CaLa4-xSi3O13:xSm3+ (0.005≤x≤0.09) phosphors were fabricated. For all samples, by XRD crystal structure and luminescence features have been examined. Based on the diffuse reflectance spectrum, for CaLa3.91Si3O13:0.09Sm3+ phosphor, both direct and indirect optical band gaps have been computed. Following measured PLE and PL spectra, we found that samples can be pumped efficiently by n-UV or blue LED chips for obtaining an intense orange emission at 598 nm (4G5/2→6H7/2) upon 403 nm (6H5/2→4F7/2) excitation. CIE color chromaticity coordinates (x, y) for both CaLa4Si3O13:0.005 and 0.09 Sm3+ phosphors are computed following their corresponding emission spectra. Under 365 nm UV lamp, CaLa4Si3O13:0.09 Sm3+ sample exhibits a bright orange color emission. In this work, it was found that the CaLa4Si3O13:0.09 Sm3+ phosphor possesses potentiality for YAG:Ce3+ phosphor color rendering index (CRI) improvement in WLEDs, excited by the blue LED chips.
关键词： CaLa4Si3O13,XRD,Sm3+ ion,CIE,Photoluminescence,Sol-gel
更新于2025-09-23 15:19:57
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Enhanced efficiency of quantum dot light-emitting diode by sol-gel derived Zn1-xMgxO electron transport layer
摘要： In this study, sol-gel derived Zn1-xMgxO (ZMO) is proposed as an electron transport layer (ETL) for solution-processed quantum-dot light-emitting diodes (QLEDs). It is demonstrated that the increase of Mg content in Zn1-xMgxO films from 0% to 20% causes a dramatic suppression of electron current, which is attributed to the lifting of conduction band minimum and reduction of electron mobility. As a result of Mg-doping, the charge carrier balance might be achieved in the QLED with the Zn0.85Mg0.15O layer resulting in maximum external quantum efficiency of 5.74% and current efficiency of 18 cd·A-1, which are over 3-fold higher than in the case of the device with ZnO layer. Improved device performance is further explained by reduced exciton quenching at QDs/ZMO interface, which is confirmed by time-resolved PL experiments. Obtained results indicate that sol-gel derived ZMO is a promising candidate for ETL in quantum-dot based optoelectronic devices.
关键词： quantum dot,doped zinc oxide,sol-gel process,light-emitting diode,electron transport layer
更新于2025-09-23 15:19:57
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Influence of the modification of annealing parameters on solution-processed metal oxide ETL buffer layers, and a comparative study of spin-coated and thermally evaporated MoOx HTL for use in an inverted polymer solar cell
摘要： Transparent metal oxide thin films were synthesized on indium tin oxide (ITO) substrates via the sol-gel spin coating method using various precursor solutions. The types of metal oxides investigated were zinc oxide (ZnO), titanium dioxide (TiO2) and molybdenum oxide (MoOx) whose purpose was to serve as buffer layers in organic solar cells. ZnO and TiO2 layers were to serve as electron transport layers (ETL), and the MoOx layer served as a hole transport layer (HTL). Compared to conventional ordering, in this set-up, the sequence of the buffer layers is inverted to improve the stability of the polymer solar cells. The annealing temperature during the preparation of the ETL metal oxide layers was varied in order to investigate the effect on the morphological properties of the thin films. The HTL layer was both spin-coated and thermally evaporated and the results were compared. The surface morphology and elemental analysis of the prepared samples were studied using a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS) capability. The optical properties were investigated by UV–Vis spectroscopy and it was found that the metal oxide layers have high optical transparency in the visible range, as required. The crystal structures of the prepared metal oxides were investigated by X-ray diffraction (XRD). A comparative study on the effect of the ETLs individually in solar cells was done by incorporating them individually with active layers of blends of poly (3-hexylthiophene) (P3HT), as electron donor and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as electron acceptor respectively. The device performance was subsequently measured and compared.
关键词： Metal oxide,Sol-gel,Buffer layers,Spin coating,Solar cell,Organic
更新于2025-09-23 15:19:57
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Structural and optical properties of doped ZnO/SiO <sub/>2</sub> nanocomposite
摘要： The synthesis of ZnO/SiO2 nanocomposite doped with Co, Cu and Mn nanoparticles were performed using sol-gel method. Rietveld refinement analysis was done for the X-ray diffraction data and results showed that all samples are single wurtzite hexagonal phase and have an average crystallite size ~14 nm. The lattice parameters, bond length, crystallite size, microstrain, dislocation density and the system volume were studied in details. Transmission electron microscopy technique showed that nanoparticles characterized by an elliptical shape. Fourier transform infrared and scanning electron microscope techniques proved the presence of SiO2 in the system. The energy gap values of both undoped and doped samples with Co, Mn and Cu were 2.84, 2.47, 2.71 and 2.8 eV, respectively. Photoluminescence spectra for undoped and doped ZnO/SiO2 were investigated in details.
关键词： ZnO/SiO2,Sol-gel,Nanocomposites,Structure,Photoluminescence
更新于2025-09-23 15:19:57
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Wettability, Photoactivity, and Antimicrobial Activity of Glazed Ceramic Tiles Coated with Titania Films Containing Tungsten
摘要： Self-cleaning coatings are advanced materials for the removal of pollutants and microorganisms by combining wettability, photocatalytic degradation, and antimicrobial activity. In this work, we propose a rational design of self-cleaning films based on TiO2 synthesized by sol?gel on commercial glazed ceramic tiles for building’s indoor applications. The synthesis strategy is based on hydrolysis and condensation of Ti-isopropoxide in the presence of W(VI) precursors to tune defects and crystallinity of the resulting W?TiO2 thin film. From the microstructure and surface composition analysis for different tungsten contents and annealing temperatures, we conclude that the film is composed by sintered TiO2 particles with adsorbed polytungstates (WOx) that inhibit anatase/rutile transformation. Polytungstates on TiO2 also induce surface defects that enhance water contact angle and inactivation of Escherichia coli under visible light. The presence of W(VI) has a negligible effect toward crystal violet degradation either under visible or under UV light. These results provide evidence on the existence of at least two different types of defects: (i) intrinsic defect from a sol?gel route and (ii) induced defect by tungsten species on the surface. Understanding the correlation between composition, structure, and self-cleaning properties provides a base for an efficient design of low-cost self-cleaning ceramic tiles that can be fully manufactured in an industrial plant.
关键词： photocatalytic degradation,sol?gel,W?TiO2,TiO2,antimicrobial activity,self-cleaning coatings
更新于2025-09-23 15:19:57
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Enhanced photocatalytic activity of a mesoporous TiO2 aerogel decorated onto three-dimensional carbon foam
摘要： TiO2/carbon composites have been well studied as solar-light photocatalysts because they combine the advantages of TiO2 (good photocatalytic activity) and carbon (enhanced charge carrier separation). Mesoporous TiO2 aerogels are fragile by nature and the addition of free-standing three-dimensional (3D) porous carbon foam (CF) not only makes it easy for separation and collection after photocatalytic treatment but also acts as a scaffold for the long-term application of TiO2 aerogels in the photocatalysis. Hence, recent reports have shown that mesoporous TiO2 aerogel/CF composites synthesized by the carbonization of a polymer followed by using the sol-gel method are significant for use in photocatalysis applications. In addition, the 3D macroporous CF not only acts as a support for TiO2 aerogels but also improves the efficiency of light use and extends the photoresponse of TiO2 to the visible region. The TiO2 aerogel was homogeneously distributed onto the 3D CF because of the vacuum infiltration used during the synthesis of the composites. The simulated solar-light irradiated photocatalytic degradation of Rhodamine B organic pollutant was used to evaluate the TiO2 aerogel/CF composite catalysts, which was higher than with a pristine TiO2 aerogel. This facile synthesis approach for 3D foam type TiO2/carbon composites could be useful in the treatment of wastewater.
关键词： anatase,Mesoporous TiO2 aerogel,photocatalysis,sol-gel method,carbon foam
更新于2025-09-23 15:19:57
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Sol-Gel Synthesis and Spectral Characterizations of (35-x)B2O3-65Bi2O3-x Fe2O3 Glass System
摘要： Sol-gel technique was used to prepare glasses of the (35-x)B2O3-65Bi2O3-x Fe2O3 (0.1≤ x ≤ 0.4) system (A1-A4: x = 0.1, 0.2, 0.3, 0.4). The local structure and symmetry around trivalent iron were determined by studying X-band powder EPR spectra at room temperature. The EPR spectra of trivalent iron in glass samples are characterized by a more intense line at g = 4.2 and a less intense line at g = 2.0. The EPR line at g = 4.2 is attributed to trivalent iron in rhombic octahedral environment. The line at g = 2.0 is because of two or more trivalent iron coupling through dipole-dipole interactions in distorted octahedral symmetry. The intensity of EPR lines is dependent of Fe2O3 content in the glass samples. At higher concentration of Fe2O3, EPR line at g = 4.2 is less intense whereas the line at g = 2.0 is more intense which is ascribed to the formation of clusters of trivalent iron. The electronic spectra of glass samples show two broad bands corresponding to d-d transition in the range 410-450 nm and in the range 530-570 nm, respectively which are assigned to trivalent iron in distorted octahedral environment.
关键词： Glass samples,Dipole-dipole interaction,Electronic spectra,Sol-gel technique
更新于2025-09-19 17:15:36
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Sol-Gel Synthesis and Characterization of Ba1-xGdxTiO3+δ Thin Films on SiO2/Si Substrates Using Spin-Coating Technique
摘要： Ba1-xGdxTiO3+δ, at x = 0, 0.05, 0.1, 0.15, 0.2, (BGT) thin films have been fabricated on SiO2/Si substrate using sol-gel method. The microstructure and surface morphology of the fabricated films have been investigated using X-ray diffraction (XRD) and atomic force microscopy (AFM). The XRD results show that the fabricated films are crystalline with perovskite structure. There is a shifting of the preferred peak at 31.5° to a higher angle as the doping ratio increases suggesting a distortion lattice exists in the films, which could be due to the substitution of Gd3+ ions into Ba-site. The decreasing of lattice constants confirms the substitution of Gd3+ in BaTiO3 lattice structure. The microstrain and dislocation density are found to be increased with the increase of Gd3+ doping, which attributed to the reduction of lattice volume that due to the ionic size mismatch effect. The AFM results show decreasing trend in both average grain size and roughness parameters. Therefore, the microstructure and surface morphology of BGT samples is strongly dependent on the Gd3+ doping concentration that mainly due to the difference ionic radius substitution.
关键词： microstructure,thin film,barium titanate,sol-gel,gadolinium doping
更新于2025-09-19 17:15:36
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Fluorescence Studies of Dy3+ Ions in Silica Sol Gel
摘要： The fluorescence properties of Dy3+ ion are utilized to study the structural changes during the gel to glass transition of the silica xerogels. The fluorescence intensity ratio (yellow to blue, Y/B) is used as a measure of the symmetry of rare earth ion environment during the gel-glass conversion. The high value of the intensity ratio of gel heated to 1000 °C showed that the rare earth ions are embedded in the glassy silica network with an asymmetric environment. Fluorescence study is also used to characterize the effect of metal cation co-dopants on the state of aggregation of rare earth ions in silica sol gel. The addition of co-dopants inhibits the clustering of rare earth ions and promotes better dispersion. The inhibition of clustering is correlated with the generation of strong crystal field bonding sites for rare earth ions in the presence of co-dopants.
关键词： Rare earth doped materials,Luminescence,Sol gel
更新于2025-09-19 17:15:36
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[BestMasters] Topographic Organization of the Pectine Neuropils in Scorpions (An Analysis of Chemosensory Afferents and the Projection Pattern in the Central Nervous System) || High Performance VOCs Sensor Based on ?-Fe2O3/Al-ZnO Nanocomposites
摘要： In this study, ternary G-Fe2O3/Al-ZnO nanocomposites (NC) were prepared using the solvothermal sol-gel process and a successive supercritical drying in ethanol. SEM analysis of the ternary NC samples showed clearly that they are formed by very small nanoparticles in the nanometer range. XRD highlighted the presence of the characteristic diffraction peaks of G-Fe2O3 and ZnO phases in all samples. Conductometric sensors were fabricated and tested for the monitoring of acetone in air. Results obtained have demonstrated that the ternary composite-based sensors display higher response to acetone and ethanol compared to that obtained with Al-ZnO and G-Fe2O3 ones.
关键词： Sol-gel,Acetone Selectivity,G-Fe2O3,Al-ZnO,Composite nanoparticles
更新于2025-09-19 17:15:36