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Photocatalytic overall water splitting on isolated semiconductor photocatalyst sites in an ordered mesoporous silica matrix: A multiscale strategy
摘要： Photocatalytic overall water splitting (OWS) in a stoichiometric ratio has attracted increasing attention for the realization of a sustainable, environmentally friendly future. However, this reaction exhibits sluggish kinetics due to efficiency limitations of the involved steps, including photon absorption, electron transfer, and the reactions that occur at triple-phase boundary regions. Herein, we report a general multiscale strategy to address this challenge by designing a model composite catalyst with a high loading density of isolated Bi0.5Y0.5VO4 nanocrystals, as building blocks, dispersed in a hexagonally ordered mesoporous silica matrix. In contrast to the well-recognized heterojunction formed between different semiconductors, we show that confined growth favours the formation of isolated quaternary solid-solution photocatalysts (Bi0.5Y0.5VO4), which can further interface with the insulating silica to overcome temperature limitations and exhibit enhanced photon absorption and electrochemical and mass transfer properties due to the transparent periodic porous structure of silica and the as-formed small nanocrystals with high crystallinity and a passivated surface. When the semiconductor photocatalyst is incorporated with the inert silica insulator, this nanoarchitecture does not inhibit the OWS activity but actually delivers a 10-fold higher OWS activity than bulk Bi0.5Y0.5VO4 prepared by the conventional solid-state method.
关键词： Multiscale strategy,Photocatalysis,Isolated solid-solution nanocrystal,Overall water splitting,Mesoporous composite
更新于2025-09-23 15:23:52
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Arbitrarily accurate variable rotations on the Bloch sphere by composite pulse sequences
摘要： Composite pulse sequences, which produce arbitrary prede?ned rotations of a two-state system at an angle θ on the Bloch sphere, are presented. The composite sequences can contain arbitrarily many pulses and can compensate experimental errors in the pulse amplitude and duration to any desired order. A special attention is devoted to two classes of π/2 sequences—symmetric and asymmetric—the phases of which are given by simple formulas in terms of rational multiples of π for any number of constituent pulses. This allows one to construct arbitrarily accurate π/2 composite rotations. These π/2 composite sequences are used to construct three classes of arbitrarily long composite θ sequences by pairing two π/2 composite sequences, one of which is shifted by a phase π ? θ with respect to the other one.
关键词： Bloch sphere,quantum control,composite pulses,error compensation,pulse sequences
更新于2025-09-23 15:23:52
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Photophysical performance of a rhodamine-MOF composite structure and its sensing potential for picric acid
摘要： For the following paper, a rhodamine-MOF composite structure, RO-EuBTC, was constructed for the optical recognition of PA (picric acid) by the covalent combination of an organic rhodamine dye and rare earth MOF. By means of XRD, IR, TGA, this composite structure was analyzed and confirmed. Its photophysical analysis suggested two sensing aspects towards PA. Be more specific, RO-EuBTC's rhodamine absorption intensity in visible region was proportional to PA, showing colorimetric sensing. RO-EuBTC's rhodamine emission intensity was proportional to PA as well, with its Eu emission intensity inversely proportional to PA, showing self-calibrated sensing signals. Both sensing aspects showed linear response and high selectivity towards PA. Their LOD value was as low as 2.2 μM. Detailed analysis confirmed its sensing mechanism as the combination of two parts, namely the rhodamine emission enhancement sparked by PA's proton and the Eu emission quenching caused by EuBTC's electron transfer to PA. RO-EuBTC was found superior to traditional optical sensing materials based on MOFs owing to its two sensing aspects and the possibility for naked eye detection.
关键词： Self-calibrated signals,Emission increase and decrease,Dynamic sensing,Composite structure
更新于2025-09-23 15:23:52
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Effect of the synthesis method on the properties of lithium doped graphene oxide composites with tin oxide nanoparticles: Towards white luminescence
摘要： Graphene oxide (GO) based composites functionalized with nanoparticles are emerging as potential candidates for multifunctional devices. As the synthesis route can strongly influence the way in which the nanoparticles are anchored to GO and the resulting properties, different routes have been employed and evaluated in this work for the preparation of composites formed by GO and undoped or Li doped SnO2 nanoparticles. Promotion of synergetic effects, as well as changes in the structural and luminescent properties of the composites have been also analyzed. In comparison with GO, composite samples synthesized in this work involve enhanced luminescence while retaining nearly white emission, which could lead to wider applicability of GO based composites in free standing and emitting and sensing devices. Aspects, such as GO reduction, stabilization of different Sn-based oxides, variation in the concentration of oxygen related functional groups, changes in the sp2 domain sizes, incorporation of lithium and enhancement of the luminescence, have been analyzed in this work by means of x-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), energy dispersive x-ray spectroscopy (EDS), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) characterizations.
关键词： Nanoparticles,Lithium,Tin oxide,Nanomaterials,Luminescence,Composite
更新于2025-09-23 15:23:52
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Enhancing the photocatalytic activity of ZnO by using tourmaline
摘要： The ZnO/tourmaline composite was synthesized by a facile precipitation-hydrothermal method. The composite showed significantly enhanced photocatalytic activity towards degradation of methylene blue (MB) compared with pure ZnO. The degradation rate maintained 90.8% after five successive photocatalytic reaction cycles in the presence of the composite. The results indicated that the enhanced photocatalytic performance of the composite was ascribed to the exposed active sites originated from the improved specific surface area, good interaction between ZnO and tourmaline, and furthermore, tourmaline’s ability of leading the photo-induced e- transferred directionally to achieve separation of e-/h+ pairs. As an earth-abundant polar mineral, tourmaline had potential application in the photocatalytic field.
关键词： Semiconductors,Photocatalysts,Composite materials,Tourmaline,ZnO
更新于2025-09-23 15:23:52
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Composite BNT-BT0.08/CoFe2O4 with core-shell nanostructure for piezoelectric and ferromagnetic applications
摘要： In this work, we report on the synthesis and characterization of BNT-BT0.08/CoFe2O4 biphasic composite with core-shell structure. This artificial core (BNT-BT0.08)/shell (CoFe2O4) heterostructure was prepared by sol-gel method and the resulting composite was characterized in term of microstructure, dielectric, piezoelectric and magnetic properties. BNT-BT0.08/CoFe2O4 sintered ceramic shows high permittivity (ε′ ≥ 30) and high dielectric losses (tan δ ≥ 10) in the low frequency range (ν ≤ 104 Hz), remnant polarization (Pr) of ～7.7 μC/cm2 and, remanent magnetization (Mr) of 24 emu/g at 5 K and of 14 emu/g, at room temperature. The present study reveals that the ferroelectric, piezoelectric and magnetic properties of this new architectured composite depend on the amount of each component and, can be tailored by adjusting their synthesis conditions. BNT-BT0.08/CoFe2O4 core-shell material investigated in this work provides a novel way to exploit new applications for the multifunctional composite, such as piezoelectric sensor, magnetoelectronic sensors and data storage devices.
关键词： Sol-gel processes,Composite core-shell,((Bi0.5Na0.5)0.92Ba0.08TiO3),Cobalt ferrite (CoFe2O4),Lead-free piezoelectric
更新于2025-09-23 15:23:52
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Single-Layer Multi-Via Loaded CRLH Leaky-Wave Antennas for Wide-Angle Beam Scanning with Consistent Gain
摘要： Achieving continuous backward-to-forward wide-angle beam scanning with consistent gain by employing composite right/left-handed leaky-wave antennas (LWAs) is reported. For structural and design simplicity, a single-layer 1-D structure is considered in which each unit cell consists of a patch shorted centrally to the ground plane. It was found that, when using only one via at the center of a unit cell, a continuous beam scan requires a large diameter via when all other parameters remain unchanged. To eliminate this limitation while maintaining a single-layer structure, novel unit cells are proposed using multiple vias in each unit cell. An LWA design for continuous beam scan with three vias in each unit cell is investigated and the results show good performance and design flexibility. A prototype antenna has been realized, and the measured results show that the antenna can scan the radiation beam continuously in a wide range, from ?60° to +66° with a consistent gain. The measured gain variation within the scan range is only 2.9 dB, and the 3dB gain bandwidth is 58.6%.
关键词： single-layer,leaky-wave antenna (LWA),backward and forward,consistent gain,composite right/left-handed (CRLH),Beam scanning
更新于2025-09-23 15:23:52
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Reusable surface plasmon resonance sensor for rapid detection of Cu2+ based on modified-chitosan thin film as an active layer
摘要： In this article, a reusable surface plasmon resonance (SPR) sensor for rapid detection of copper ions (Cu2+), based on optimized silver/gold (Ag/Au) composite film modified by modified-chitosan (MCS) thin film as an active layer, was achieved. We employed a four-layer Kretchmann semi-cylindrical prism configuration and induced a reference beam into the experimental system to improve the sensitivity and stability, and investigated the cross-linking technique of CS solution, the spin coating process of MCS film, the stability of active layer, the rebirth power of SPR sensor, and the detection for trace Cu2+. The rate of swelling or dissolution of MCS film after flushing sensor chip for four times is less than 9×10?4/min, and the decline of signal value is less than 1.5% after MCS film adsorbing Cu2+ and multiple flushing. The elution and capacity rates are above 96% after five times of elution for the sensor by EDTA solution with 0.5mmol/L. Within 1-5ppm, the SPR sensor was found to possess sensitivity of 0.7271ppm?1. The LOD is 18ppb for the trace Cu2+. The present SPR sensor not only could be used in trace monitoring of Cu2+ but also could be extended to other potential applications.
关键词： Copper ions,Reutilization,Composite film,Modified-chitosan,Surface plasmon resonance
更新于2025-09-23 15:23:52
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A highly sensitive photocatalytic plastic optic-fiber sensor for selective detection of phenol in aqueous solutions
摘要： We present a highly sensitive photocatalytic plastic optic-fiber (POF) sensor for the selective detection of phenol in aqueous solutions. To obtain high sensitivity and low limit of detection (LOD) of the sensor, part of the POF cladding was removed and replaced by a Canada balsam doped with GeO2 (CBG); a UV-visible-light-driven photocatalytic material, that is a CdS-sensitized Er3+YAlO3/SiO2/TiO2 (EYST) composite, was coated on the CBG film. To realize highly selective detection of phenol in water, a high phenol permselectivity and pH independence polymer membrane was fixed on the CdS-sensitized EYST-CBG-coated POF. Furthermore, a model was developed to show that the phenol concentration can be determined by measuring the change in transmitted light intensity of the POF sensor and the sensitivity of the sensors can be improved by employing the CdS-sensitized EYST film. The results showed that the proposed photocatalytic POF sensor has a high sensitivity of -0.39 (mg·mL-1)-1 and low LOD of 15 μg·L-1 for the selective detection of phenol in aqueous solutions with pH ranging from 2.0 to 14.0.
关键词： Cds sensitization,Phenol concentration,High sensitivity and selectivity,Upconversion luminescence agent,Plastic optical fiber,TiO2 composite film
更新于2025-09-23 15:23:52
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Polyimide-TiO2 nanocomposites and their corresponding membranes: Synthesis, characterization, and gas separation applications
摘要： In this work at firstly a new class of polyimide/TiO2 (PI/TiO2) composites containing amino acid (Methionine) and benzimidazole fractions in the structure with chemical bonds between the polyimide and TiO2 network has been synthesized by the sol-gel reaction and characterized and then secondly carbon (C) membranes were prepared by carbonization of PI/TiO2 at different temperatures under vacuum and nitrogen flow. Carbonization temperature was critical in the modification of membrane structure. At the same temperature, the carbon membranes fabricated under nitrogen atmosphere had higher gas permeations than those fabricated under vacuum. With the introduction of the TiO2, there was no significant enhancement of the gas separation in the resulting PI/TiO2 composite membranes over the PI membrane, which still suffered a "trade-off" relationship between permeability and selectivity. However, the derived C/PI/TiO2 composite membranes exhibited better gas separation properties. The C/PI/TiO2 15% composite membrane produced the highest permeations of 650.47, 520.56, 187.92 and 115.22 GPU for He, CO2, O2 and N2, respectively. The bionanocomposites were analyzed for antibacterial activity against Gram-positive and Gram-negative bacteria. The results indicated that the synthesized bionanocomposites is effective against all of the studied bacteria, and its effectiveness is higher for Pseudomonas aeruginosa.
关键词： Polyimide,Composite membranes,Carbonization,TiO2,Gas permeations
更新于2025-09-23 15:23:52