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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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Large-Scale Purification of Photon-Upconversion Nanoparticles by Gel Electrophoresis for Analog and Digital Bioassays
摘要： The performance of photon-upconversion nanoparticles (UCNPs) as background-free luminescent labels in bioanalytical applications strongly depends on the preparation of well-defined and water-dispersible nanoconjugates. We have exploited the separation power of agarose gel electrophoresis to purify milligram amounts of homogeneous UCNPs covered with carboxylated silica, biotin or streptavidin with recovery rates of 30 to 50%. Clusters containing discrete numbers of UCNPs were isolated from the gel and reanalyzed by agarose gel electrophoresis, single nanoparticle upconversion microscopy and additional complementary methods. The purified nanoconjugates improved conventional (analog) bioaffinity assays and provided highly monodisperse conjugates for assays that rely on counting individual UCNPs (digital assays).
关键词： streptavidin,bioconjugate,Agarose gel electrophoresis,purification,digital bioassay,biotin
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
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Tuning of opto-electrical properties of hematite thin films using Co2+ doping
摘要： Hematite thin films have attracted widespread interest in recent years because of their advanced electronic and optical properties. Optical and electronic properties of hematite thin films can be enhanced/tuned using doping or additive-based strategies. An application oriented sol–gel method is used for the synthesis of cobalt (Co) doped hematite sol with variation in Co concentration in the range of 0–10 wt%. Hematite phase is observed in undoped thin films annealed at 300 °C under 500 Oe magnetic field for 60 min. Strengthening of hematite phase is observed with increase in Co concentration up to a value of 8 wt%. Bond angle with +ive tilt (i.e. ~ 19.74°) was observed in refined structural parameters for thin films prepared with Co concentration in the range of 0–8 wt%. Higher Co concentration, i.e. 10 wt%, results in decrease in crystallinity of the films along with smaller +ive tilt in bond angle (i.e. ~ 8.82°). High transmission (~ 88%) is observed for thin film prepared using dopant concentration of 8 wt% in the visible and infrared regions. The energy band gap varies from 2.42 to 2.25 eV with variation in Co concentration from 0 to 10 wt%. Relatively smaller band gap values are correlated with defect induced states in the band gap. Spectroscopic ellipsometry is used for calculation of refractive index and high values are indication of high density of thin films. Relatively higher value of dielectric constant (~ 183, log f = 5.0) along with lower value of tangent loss is observed at Co concentration of 8 wt%. Higher grain boundary resistance (1.88 × 105 ?) was observed at 8 wt% Co concentration. Variation in d.c. conductivity with dopant concentration is studied in detail using Jonscher’s power law. The value of frequency exponent (n) lies in the range of 0.88–0.98 (< 1) with variation in dopant concentration signifying that motion of charge carriers involves translational motion along with sudden hopping process. It is important to mention here that combined tuning of optical and electrical properties are observed in the present study with no change in phase pure hematite crystallographic structure.
关键词： Hematite thin films,Optical properties,Sol-gel method,Electrical properties,Dielectric constant,Transmission,Band gap,Cobalt doping
更新于2025-09-19 17:15:36
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A Supramolecular Gel of Oxalic Acid-Monoethanolamine for Potential Schottky Barrier Diode Application
摘要： A functional supramolecular gel of oxalic acid and monoethanolamine (OXMEA) has been achieved through direct instant mixing of N,N-dimethyl formamide (DMF) solution of oxalic acid and pure monoethanolamine at room temperature under ambient condition. The rheological analysis established the viscoelastic semi-solid type nature of mechanically stable OXMEA supramolecular gel. The morphological pattern, imaged through field emission scanning electron microscopic investigation, explores the bean-seed like hierarchical architecture of the gel network. The semiconducting property of the gel was verified from band gap energy and conductivity estimation. The electrical charge transport property was also analyzed in the form of OXMEA gel based metal-semiconductor junction thin film device. The obtained nonlinear current-voltage characteristics of the device signify Schottky barrier diode nature of the synthesized gel. Overall, this work has been proof of development of semiconducting electronic device by OXMEA gel based gel medium.
关键词： Semiconductor,Morphology,Supramolecular Gel,Rheology,Schottky barrier diode
更新于2025-09-19 17:15:36