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Crystalline phase effect on the up-conversion processes and white emission of Yb3+/Er3+/Tm3+: Y2Si2O7 nanocrystals.
摘要： Yb3+, Er3+, Tm3+: Y2Si2O7 nano powders were fabricated by sol-gel method and then annealed at two different temperatures of 1050°C and 1480°C for 12 h to investigate the phase effect on the structural and optical properties. X-ray diffraction patterns (XRD) of all powders revealed that most of the peaks were in good harmony with the standard JCPDS cards of Y2Si2O7 (PDF#38-0223 and PDF#38-0440). SEM images of the powders were taken to examine the morphology and chemical analysis of the powders. Diffuse reflections spectra of Y2Si2O7 exhibited varying number of transitions depending on the dopant ion in all powders in the range of 400-1050 nm. Spectral properties of the powders were detailed to identify the possible up-conversion (UC) emission mechanism in the range between 400 - 900 nm under 975 nm excitation. The broadening white light emission was observed with increasing laser pumping power at room temperature as well. Spectral profiles of the transitions observed in both reflectance and up-conversion luminescence spectra were found to be crystalline phase depended.
关键词： Nanophosphors,Sol–gel process,Up-conversion,White emission
更新于2025-11-25 10:30:42
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Bulk Photodriven CO <sub/>2</sub> Conversion through TiO <sub/>2</sub> @Si(HIPE) Monolithic Macrocellular Foams
摘要： Operating photo-induced reactions exclusively on catalyst surfaces while not exploiting the full catalyst volume generates a major footprint penalty for the photocatalytic reactor and leads to an inefficient use of the catalytic material. Photonic investigations clearly show that the solid foams have a strongly multi-diffusive character, with photons being significantly trapped within the sample cores while addressing a photon mean free path lt = 20.1 ± 1.3 μm. This 3D process both greatly limits back-reactions and promotes outstanding selectivity toward methane (around 80%) generation, and even ethane (around 18%) through C-C coupling reaction, with residual carbon monoxide and dihydrogen contents (around 2%). Silica–titania TiO2@Si(HIPE) self-standing macrocellular catalysts lead to optimal efficient thicknesses up to 20 times those of powders, thereby enhancing the way for real 3D-photodriven catalytic processes above the millimeter scale and up to a 6 mm thickness. A rather simple Langmuir–Hinshelwood based kinetic model is proposed which highlights the strong dependence of photocatalytic reaction rates on light scattering and the crucial role on oxidation back-reactions. In addition, a strong correlation between light attenuation coefficient and photon mean free path and median pore aperture diameter is demonstrated, offering thus a tool for photocatalytic behavior prediction.
关键词： heterogeneous catalysis,CO2 photoreduction,sol–gel process,porous materials,integrative chemistry
更新于2025-09-23 15:22:29
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Synthesis of Calcium Aluminate-Based Luminophores by the Citrate Nitrate Sol–Gel Process
摘要： Microwave-assisted sol–gel process was used to synthesize calcium aluminate and luminescent materials based on it, which find wide use in the manufacture of construction materials, catalysts, optical emission sources, and display devices. The major processes involved in the formation of crystalline calcium aluminate were identified resorting to powder X-ray diffraction, thermal analysis, scanning electron microscopy, and IR spectroscopy data. Synthetic steps have moderate activation energies in the 44–260 kJ/mol range. Luminescence characteristics of the obtained crystal phosphors were measured. The increase in the synthesis temperature to 1200°C and the increase in the activator concentration to 5 mol % enhance the luminescence of the Eu3+-activated calcium aluminate-based luminophore. Further increase in the concentration of the activator ions leads to luminescence quenching caused by the concentration effect.
关键词： calcium aluminate,sol–gel process,microwave treatment,europium(III) ions,crystal phosphor
更新于2025-09-23 15:21:01
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Efficient N, Fe Co-Doped TiO2 Active under Cost-Effective Visible LED Light: From Powders to Films
摘要： An eco-friendly photocatalytic coating, active under a cost-effective near-visible LED system, was synthesized without any calcination step for the removal of organic pollutants. Three types of doping (Fe, N and Fe + N), with different dopant/Ti molar ratios, were investigated and compared with undoped TiO2 and the commercial P25 photocatalyst. Nano-crystalline anatase-brookite particles were successfully produced with the aqueous sol-gel process, also at a larger scale. All samples displayed a higher visible absorption and specific surface area than P25. Photoactivity of the catalyst powders was evaluated through the degradation of p-nitrophenol in water under visible light (>400 nm). As intended, all samples were more performant than P25. The N-doping, the Fe-doping and their combination promoted the activity under visible light. Films, coated on three different substrates, were then compared. Finally, the photoactivity of a film, produced from the optimal N-Fe co-doped colloid, was evaluated on the degradation of (i) p-nitrophenol under UV-A light (365 nm) and (ii) rhodamine B under LED visible light (395 nm), and compared to undoped TiO2 film. The higher enhancement is obtained under the longer wavelength (395 nm). The possibility of producing photocatalytic films without any calcination step and active under low-energy LED light constitutes a step forward for an industrial development.
关键词： aqueous sol-gel process,Fe/N doping,LED visible light,titania,photocatalysis
更新于2025-09-23 15:21:01
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Effect of the occupation of Ba and Ti sites on the structural, optical and dielectric properties of Sm-doped BaTiO3 ceramics
摘要： Sm-doped BaTiO3 powders have been synthesized with the help of the sol gel process. X-ray diffraction (XRD) patterns of the obtained powders, heat treated at a relatively low temperature (750 °C/3 h), revealed their crystallization in the pure perovskite structure without the presence of secondary phases. The occupation of the Ba and Ti sites by Sm in the BaTiO3 lattice and the evolution of the crystalline parameters as functions of the dopant content have been discussed based on XRD and Raman results. Dielectric measurements performed on the samples revealed a strong increasing diffuse character of the ferro-to-paraelectric phase transition with increasing Sm content. Moreover, the behavior of the permittivity as a function of frequency indicates that the samples are approaching their resonance frequency. The study of the conductivity showed the existence of a weak positive temperature coefficient of resistivity (PTCR) effect.
关键词： Sm-doped BaTiO3,dielectric properties,PTCR effect,perovskite structure,sol gel process
更新于2025-09-23 15:21:01
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Thin silica-based microsheets with controlled geometry
摘要： A high demand for materials with defined geometry and size is required in a wide range of fields. Inorganic compounds, especially silica-based, arise as a cheap source and chemically flexible for the purpose. Silica display unique properties, like easy functionalization and good optical to manipulate. In this work, we developed a method to create thin silica microsheets with defined size and high-fidelity shape using superhydrophobic-hydrophilic microarrays. These microstructures were produced through sol-gel process using biomimetic superhydrophobic surfaces decorated with wettable spots. The results confirm the manufacture of porous silica microstructures with defined design (squares and circles) and thickness around 7 μm. The methodology applied in this work enables the high throughput fabrication of shaped silica materials in a single step, unlocking an extensive number of applications in areas that require miniaturization, like microelectronics or in fields like sensing and biomedicine.
关键词： Silica microsheets,High-fidelity shape,Inorganic materials,High throughput,Sol-gel process
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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Sol-gel Syntheses of Photocatalysts for the Removal of Pharmaceutical Products in Water
摘要： A screening study on seven photocatalysts was performed to identify the best candidate for pharmaceutical products degradation in water. Photocatalysts were deposited as thin films through a sol-gel process and subsequent dip-coating on glass slides. The efficiency of each photocatalyst was assessed through the degradation of methylene blue first, and then, through the degradation of 15 different pharmaceutical products. Two main types of synthesis methods were considered: aqueous syntheses, where the reaction takes place in water, and organic syntheses, where reactions take place in an organic solvent and only a stoichiometric amount of water is added to the reaction medium. Photocatalysts synthesized via aqueous sol-gel routes showed relatively lower degradation efficiencies; however, the organic route required a calcination step at high temperature to form the photoactive crystalline phase, while the aqueous route did not. The best performances for the degradation of pharmaceuticals arose when Evonik P25 and silver nanoparticles were added to TiO2, which was synthesized using an organic solvent. In the case of methylene blue degradation, TiO2 modified with Evonik P25 and TiO2 doped with MnO2 nanoparticles were the two best candidates.
关键词： sol-gel process,thin films,pharmaceutical products,TiO2,photocatalysis
更新于2025-09-19 17:15:36
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Controlled gel research: the effect of ethanol for delaying the polycondensation of tetraethyl orthosilicate-dimethyldiethoxysilane
摘要： In this study, the effect of ethanol for delaying the polycondensation of silanol in the co-hydrolysis-condensation of tetraethyl orthosilicate-dimethyldiethoxysilane was first explored and demonstrated by varying the amount of ethanol under low-water content and acid-catalyzed. On the basis of this, the controllability of the sol-gel process is realized, and the calculation formula of the gel formation time is provided. The experiment shows that the storage gel time and the reaction gel time are extended from 75 h to at least 4584 h, or from 20 to 65 h with the increase of ethanol concentration, respectively. And we observed the microscopic process of solution-sol-gel transition by light transmission microscope. The sol-gel process established in this experiment gives a mechanism reference for future research.
关键词： Polycondensation,Sol-gel process,Delay,Gel time,Controllability
更新于2025-09-16 10:30:52
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PEGylation of protein-imprinted nanocomposites sandwiching CdTe quantum dots with enhanced fluorescence sensing selectivity
摘要： Fluorescent sensors combining the selective recognition of protein molecularly imprinted polymers (MIPs) and the fluorescent sensing of quantum dots (QDs) have been studied considerably, but their fluorescence sensing selectivity for the target proteins remains to be increased. Herein, we propose a strategy for increasing the sensing selectivity by post-imprinting PEGylation of surface protein-imprinted nanocomposites with embedded QDs. With bovine hemoglobin (BHb) as a model protein template, protein MIP nanolayers were anchored over the CdTe QD decorated SiO2 nanoparticles by the sol–gel process using aminopropyltriethoxy silane and tetraethoxysilicane. PEG chains were then grafted onto the surface of the imprinted nanostructures via the nucleophilic reaction of the surface amine groups with N-hydroxysuccinimide ester-terminal methoxy-PEG, followed by template removal. The resultant PEGylated sensors showed significantly improved aqueous dispersion stability compared with the non-PEGylated controls. More importantly, such PEGylation greatly increased the fluorescence response selectivity, with the Stern–Volmer equation based imprinting factor increasing from 2.7 to 5.4. The PEGylated sensors were applied to determine BHb in bovine serum samples with satisfactory recoveries at three spiking levels ranging from 94.3 to 103.7%, indicating their potential application in real samples.
关键词： PEGylation,Fluorescent sensors,Protein molecularly imprinted polymers,Quantum dots,Stern–Volmer equation,Bovine serum samples,Sol–gel process,Bovine hemoglobin
更新于2025-09-16 10:30:52