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Extracellular biosynthesis of Cu2-xSe nanocrystallites with photocatalytic activity
摘要： Semiconductor Cu2-xSe nanospheres were successfully biosynthesized based on bioreduction of SeO3 2? into Se2? by the selenite-reducing bacterium, Pantoea agglomerans. The Cu2-xSe nanospheres had excellent crystallinity with a face-centered cubic structure and an average diameter of 80 nm. Composition and oxidation states analysis using X-ray photoelectron spectroscopy and X-ray energy dispersive spectroscopy followed by optical characterization using ultraviolet-visible and Fourier transform infra-red spectroscopy confirmed that the biosynthesized Cu2-xSe nanospheres were capped by proteins. The extracellular proteins which mediated biosynthesis were visualized by excitation–emission matrix fluorescence spectroscopy. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis revealed that the molecular masses of proteins were about 110, 50, 38, 35 and 25 kDa. The biosynthesized Cu2?xSe nanospheres showed an excellent and stable photocatalytical activity under sunlight irradiation in the degradation of methylene blue for four cycles. This study put forward a green and toilless way to manufacture copper selenide nanoparticles using a biological process.
关键词： Biosynthesis,Photocatalytical activity,Cu2-xSe,Extracellular proteins
更新于2025-09-23 15:21:21
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Theory-Driven Heterojunction Photocatalyst Design with Continuously Adjustable Band Gap Materials
摘要： The utilization efficiency of hot carriers in photocatalyst is limited at present by their fast recombination. Heterojunction interface would reduce the recombination rate by effectively facilitating spatial separation of the hot electron and hole. Here, we establish a heterojunction photocatalyst design principle by using continuously adjustable band gap materials. This is demonstrated using first-principles calculations, and is subsequently validated by direct measurements of photocatalytic activity of ZnxCd1-xS-reduced graphene oxide (RGO) heterojunction as a proof-of-concept photocatalyst. Tuning the Zn/Cd ratio and/or the reduction degree of RGO can result into three types of heterojunction, and different conduction and valence band offsets by varying their band gap and positions of band edges. The modulation of efficient electron-hole separation at the interface is manifested by the consistency of calculated and experimental optical absorbance, and enhanced photocatalytical activity of ZnxCd1-xS-RGO heterojunction. This results can also rationalize the available experimental results of RGO-based composites. This design principle is broadly applicable to the development of other heterojunction materials ranging from photocatalysts and solar cells to functional electronic devices through interfacial band alignment engineering.
关键词： band gap,photocatalytic activity,RGO,heterojunction,ZnxCd1-xS,photocatalyst,first-principles calculations
更新于2025-09-23 15:21:21
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Density Functional Theory Calculations of Oxygen-Vacancy Formation and Subsequent Molecular Adsorption on Oxide Surfaces
摘要： The surface oxygen vacancy formation energy (EOvac) is an important parameter in determining the catalytic activity of metal oxides. Estimating these energies can therefore lead to data-driven design of promising catalyst candidates. In the present study, we determine EOvac for various insulating and semiconducting oxides. Statistical investigations indicate that the band gap, bulk formation energy, and electron affinity are factors that strongly influence EOvac. Electrons enter defect states after O desorption, and these states can be in the valence band, mid-gap, or in the conduction band. Subsequent adsorption of O2, NO, CO, CO2, and H2 molecules on an O-deficient surface is also investigated. These molecules become preferentially adsorbed at the defect sites, and EOvac is identified as the dominant factor that determines the adsorption mode as well as a descriptor that shows good correlation with the adsorption energy.
关键词： catalytic activity,molecular adsorption,oxygen vacancy formation energy,metal oxides,density functional theory
更新于2025-09-23 15:21:21
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Dual-mode Au nanoprobe based on surface enhancement Raman scattering and colorimetry for sensitive determination of telomerase activity both in cell extracts and the urine of patients
摘要： Telomerase is a valuable biomarker, which is highly correlated to cancer diseases. However, single-mode probe for telomerase detection cannot satisfy the challenge of detection of telomerase activity rapidly, simply with high selectivity, sensitivity and accuracy both in preliminary diagnosis and point of care (POC) testing. Therefore, there is an urgent need to develop a robust approach with controllable assembly and high accuracy to consider both the simplification of preliminary diagnosis and POC testing and the quantification requirement for early clinical diagnosis and treatment. Herein, a novel dual-mode Au NPs probe was developed for determination of telomerase activity with controllable assembly and aggregation statement based on surface enhancement Raman scattering (SERS) and colorimetry. In this strategy, an Au dimer-based probe with high uniformity was assembled successfully, telomerase activity was reflected according to the color variations of solution and the Raman intensity of Raman reporter. Taking advantage of the uniformity of Au dimers and the combination of colorimetry and SERS techniques, our strategy determined the telomerase activity with high accuracy, sensitivity and wide range. The established probe possessed of high selectivity, sensitivity and accuracy, which was approved as a reliable, intuitional and convenient approach for detecting telomerase activity.
关键词： colorimetry,bladder cancer,surface enhanced Raman scattering,Au nanoparticles,telomerase activity
更新于2025-09-23 15:21:21
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Disentangling stellar activity from exoplanetary signals with interferometry
摘要： Stellar activity can express as many forms at stellar surfaces: dark spots, convective cells, bright plages. Particularly, dark spots and bright plages add noise on photometric data or radial velocity measurements used to detect exoplanets, and thus lead to false detection or disrupt their derived parameters. Since interferometry provides a very high angular resolution, it may constitute an interesting solution to distinguish the signal of a transiting exoplanet and that of stellar activity. It has also been shown that granulation adds bias in visibility and closure phase measurements, affecting in turn the derived stellar parameters. We analyze the noises generated by dark spots on interferometric observables and compare them to exoplanet signals. We investigate the current interferometric instruments able to measure and disentangle these signals, and show that there is a lack in spatial resolution. We thus give a prospective of the improvements to be brought on future interferometers, which would also significantly extend the number of available targets.
关键词： closure phase measurements,interferometry,bright plages,dark spots,granulation,exoplanetary signals,visibility,stellar activity
更新于2025-09-23 15:21:21
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Magnetoencephalography with optically pumped 4He magnetometers at ambient temperature
摘要： In this paper, we present the first proof of concept confirming the possibility to record magnetoencephalographic (MEG) signals with Optically Pumped Magnetometers (OPMs) based on the parametric resonance of 4He atoms. The main advantage of this kind of OPM is the possibility to provide a tri-axis vector measurement of the magnetic field at room-temperature (the 4He vapor is neither cooled nor heated). The sensor achieves a sensitivity of 210 fT/√Hz in the bandwidth [2 Hz - 300 Hz]. MEG simulation studies with a brain phantom were cross-validated with real MEG measurements on a healthy subject. For both studies, MEG signal was recorded consecutively with OPMs and Superconducting Quantum Interference Devices (SQUIDs) used as reference sensors. For healthy subject MEG recordings, three MEG proofs of concept were carried out: auditory and visual evoked fields (AEF, VEF), and spontaneous activity. M100 peaks have been detected on evoked responses recorded by both OPMs and SQUIDs with no latency. Concerning spontaneous activity, an attenuation of the signal power between 8-12 Hz (alpha band) related to eyes opening has been observed with OPM similarly to SQUID. All these results confirm that the room temperature vector 4He OPMs can record MEG signals and provide reliable information on brain activity.
关键词： visual evoked field,Optically pumped magnetometer,vector measurement,magnetoencephalography,spontaneous activity,auditory evoked field,room temperature,Helium 4
更新于2025-09-23 15:21:21
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[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - Deep Learning based Human Activity Classification in Radar Micro-Doppler Image
摘要： A convolutional neural network (CNN) based deep learning (DL) approach to classify human activities in micro-Doppler spectrogram of radar is investigated. MOCAP dataset, from Carnegie Mellon University, is used for spectrogram simulation. Seven activities are classified with the proposed CNN network. Our network outperforms several previously published DL-based approaches. To understand the network’s impact on classification performance, we investigate some key parameters of the proposed network. Experiment result demonstrates that a deeper network does not necessarily result in a higher accuracy. We also examine the network size and the number of output feature maps to find out their impact on the result.
关键词： Deep Learning,Convolutional Neural Network,Human Activity Classification,Micro-Doppler Spectrogram,Radar image
更新于2025-09-23 15:21:21
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Applications of Functional Near-Infrared Spectroscopy (fNIRS) Neuroimaging in Exercise–Cognition Science: A Systematic, Methodology-Focused Review
摘要： For cognitive processes to function well, it is essential that the brain is optimally supplied with oxygen and blood. In recent years, evidence has emerged suggesting that cerebral oxygenation and hemodynamics can be modified with physical activity. To better understand the relationship between cerebral oxygenation/hemodynamics, physical activity, and cognition, the application of state-of-the art neuroimaging tools is essential. Functional near-infrared spectroscopy (fNIRS) is such a neuroimaging tool especially suitable to investigate the effects of physical activity/exercises on cerebral oxygenation and hemodynamics due to its capability to quantify changes in the concentration of oxygenated hemoglobin (oxyHb) and deoxygenated hemoglobin (deoxyHb) non-invasively in the human brain. However, currently there is no clear standardized procedure regarding the application, data processing, and data analysis of fNIRS, and there is a large heterogeneity regarding how fNIRS is applied in the field of exercise–cognition science. Therefore, this review aims to summarize the current methodological knowledge about fNIRS application in studies measuring the cortical hemodynamic responses during cognitive testing (i) prior and after different physical activities interventions, and (ii) in cross-sectional studies accounting for the physical fitness level of their participants. Based on the review of the methodology of 35 as relevant considered publications, we outline recommendations for future fNIRS studies in the field of exercise–cognition science.
关键词： working memory,executive functions,cognition,physical activity,optical imaging,fNIRS
更新于2025-09-23 15:21:21
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Effect of thermal oxidation temperatures on the phase evolution and photocatalytic property of tungsten-doped TiO <sub/>2</sub> thin film
摘要： Tungsten-doped titanium dioxide (W-TiO2) thin films were successfully prepared on glass substrates by sputtering thermally oxidized W-doped titanium films in air. Tungsten-doped titanium films were deposited using a DC and RF magnetron cosputtering system. The effects of annealing treatment and W content on the W-TiO2 film microstructure were investigated. The crystalline structures, morphological features, and photocatalytic activity of the annealed W-TiO2 films were systematically studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and ultraviolet spectrophotometry. The results indicated that annealing at 550 °C clearly induced the formation of an anatase and rutile phase mixture in the 5.5 at. % W-TiO2 films, which directly affected photocatalytic activity. The W-TiO2 films showed good photocatalytic activity under UV-light irradiation, with a higher rate of methylene blue dye degradation than in the case of undoped TiO2.
关键词： photocatalytic activity,tungsten-doped titanium dioxide,thermal oxidation,methylene blue degradation,thin films
更新于2025-09-23 15:21:21
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A facile room-temperature synthesis of three-dimensional coral-like Ag2S nanostructure with enhanced photocatalytic activity
摘要： Morphology is a crucial factor in determining the chemical, optical, and electrical properties of nanoscale materials. In this work, we utilized a facile room-temperature deposition method to synthesize three-dimensional (3D) coral-like Ag2S nanostructures. The formation mechanism of 3D coral-like Ag2S nanostructures was proposed by tracking the reaction process. In comparison with 0D Ag2S nanoparticles and 1D Ag2S nanowires of similar size, 3D coral-like Ag2S nanostructures exhibit higher pore volume, photocatalytic activity and cyclic stability for degradation of methyl orange (MO). Surface photovoltage measurement, electrochemical impedance spectroscopy, and Mott–Schottky analysis showed that compared to other Ag2S nanostructures, 3D coral-like Ag2S nanostructures have the strongest surface photovoltaic response, longest carrier lifetime, and highest carrier density.
关键词： Carrier lifetime,Surface photovoltage,Ag2S,3D coral-like nanostructure,Photocatalytic activity
更新于2025-09-23 15:21:21