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Graphene based nanocomposites for efficient photocatalytic hydrogen evolution: insight into the interface toward separation of photogenerated charges
摘要： Although the reduced graphene oxide (rGO) has been intensively applied to photocatalytic H2 evolution, no enough attention was given to study the interface between photocatalyst and rGO, which is the key point to affect the transportation of photogenerated electron. Herein, in order to research the heterojunctions interface, the series of SrTiO3 photocatalysts with different crystal facets were fabricated to load with rGO for photocatalytic H2 evolution. The characterization measurements and theory calculation verified that the rGO was mainly anchored on the Ti-O bond of SrTiO3. So, compared to {001} facets sample, the {110} facets of SrTiO3, exposed more Ti and O atoms, could form stronger bond with the rGO. Additionally, DFT study deduced that the photoinduced electron could immigrate rapidly from Ti-O bond to the rGO, which was in good agreement with the results of photoelectrochemical and photoluminescence (PL) experiments. Meanwhile, experimentally, the 1 % wt. rGO@SrTiO3 with {110} facets nanocomposite showed the superior photocatalytic H2 yield rate (3.82 mmol/h/g), which was 2.2 times and 3.2 times higher than that of pure SrTiO3 with the same facets and 1 % wt. rGO@SrTiO3 with {001} facets, respectively. Both experiments and theoretical calculations unveiled that the synergetic effect of SrTiO3 facets engineering and rGO loading effectively prompted the immigration of photoinduced electron at the nanocomposites interface. This work provides a rational thinking of a high efficiency rGO-based heterogeneous photocatalysts for solar energy conversion.
关键词： density functional theory study,rGO-based heterogeneous photocatalysts,separation of photogenerated charges,photocatalytic hydrogen evolution,SrTiO3,electron screening effect
更新于2025-09-09 09:28:46
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Morphological evolution of upconversion nanoparticles and their biomedical signal generation
摘要： Advancements in the fabrication of upconversion nanoparticles (UCNPs) for synthetic control can enable a broad range of applications in biomedical systems. Herein, we experimentally verified the role of the hydrothermal reaction (HR) time in the synthesis of NaYF4:20%Yb3+/3%Er3+ UCNPs on their morphological evolution and phase transformation at different temperatures. Characterizations of the as-prepared UCNPs were conducted using X-ray diffraction (XRD), electron microscopy and spectroscopy, and thermogravimetric and upconversion (UC) luminescence analysis. We demonstrated that determining the optimal HR time, also referred to here as the threshold time, can produce particles with good homogeneity, hexagonal phase, and UC luminescence efficiency. Subsequently, the polymer coated UCNPs maintained their original particle size distribution and luminescence properties, and showed improved dispersibility in a variety of solvents, cellular nontoxicity, in vitro bioimaging, and biocompatibility as compared to the bare UCNP. Besides this, polyacrylic acid conjugated UCNPs (UCNP@PAA) also revealed the strong anticancer effect by conjugating with doxorubicin (DOX) as compared to the free DOX. Based on these findings, we suggest that these particles will be useful in drug-delivery systems and as in vivo bioimaging agents synchronously.
关键词： phase transformation,morphological evolution,biomedical applications,hydrothermal reaction,upconversion nanoparticles
更新于2025-09-09 09:28:46
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Transient electrohydrodynamics of a liquid drop in AC electric fields
摘要： The transient behavior of a leaky dielectric liquid drop under a uniform AC electric ?eld of small strength is investigated, using a closed form analytical solution. The drop settles to a quasi-steady state in a relaxation time that is set by the viscosities of the drop and the ambient ?uid and the surface tension, and oscillates around a mean deformation with a frequency that is twice the electric ?eld frequency. The mode of instantaneous deformation remains the same (oblate or prolate) or switches between oblate and prolate, depending on the relative importance of the time-periodic component of the deformation compared to that of the time-exponential. The structure of the ?ow ?eld and its evolution is studied for representative ?uid systems at a high and a low electric ?eld frequency. The individual contribution of the net tangential and normal electric stresses, which are the driving forces of the problem, on the ?ow structure and drop deformation is characterized. On the basis of the mean (time-independent) and time-periodic components of the driving forces, the ?ow ?eld is represented as the superposition of three di?erent ?ow patterns. It is shown that the interplay of these ?ow patterns leads to formation and destruction of toroidal vortices, and that the residence time of these vortices correlates inversely with the ?eld frequency.
关键词： liquid drop,AC electric ?elds,leaky dielectric,?ow ?eld evolution,transient electrohydrodynamics
更新于2025-09-09 09:28:46
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On the Interpretation of Far-infrared Spectral Energy Distributions. I. The 850 <i>μ</i> m Molecular Mass Estimator
摘要： We use a suite of cosmological zoom galaxy formation simulations and dust radiative transfer calculations to explore the use of the monochromatic 850 μm luminosity (Lν,850) as a molecular gas mass (Mmol) estimator in galaxies between 0 < z < 9.5 for a broad range of masses. For our fiducial simulations, where we assume that the dust mass is linearly related to the metal mass, we find that empirical Lν,850–Mmol calibrations accurately recover the molecular gas mass of our model galaxies and that the Lν,850-dependent calibration is preferred. We argue that the major driver of scatter in the Lν,850–Mmol relation arises from variations in the molecular gas-to-dust mass ratio, rather than variations in the dust temperature, in agreement with the previous study of Liang et al. Emulating a realistic measurement strategy with ALMA observing bands that are dependent on the source redshift, we find that estimating Sν,850 from continuum emission at a different frequency contributes 10%–20% scatter to the Lν,850–Mmol relation. This additional scatter arises from a combination of mismatches in assumed Tdust and β values, as well as the fact that the SEDs are not single-temperature blackbodies. However, this observationally induced scatter is a subdominant source of uncertainty. Finally, we explore the impact of a dust prescription in which the dust-to-metals ratio varies with metallicity. Though the resulting mean dust temperatures are ～50% higher, the dust mass is significantly decreased for low-metallicity halos. As a result, the observationally calibrated Lν,850–Mmol relation holds for massive galaxies, independent of the dust model, but below Lν,850 ? 1028 erg s?1 (metallicities log10(Z/Z⊙) ? ?0.8) we expect that galaxies may deviate from literature observational calibrations by ?0.5 dex.
关键词： galaxies: ISM,galaxies: evolution,galaxies: high-redshift
更新于2025-09-09 09:28:46
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Localized Surface Plasmon Resonance Enhanced Photocatalytic Hydrogen Evolution via Pt@Au NRs/C <sub/>3</sub> N <sub/>4</sub> Nanotubes under Visible-Light Irradiation
摘要： Au nanorods (NRs) decorated carbon nitride nanotubes (Au NRs/CNNTs) photocatalysts have been designed and prepared by impregnation–annealing approach. Localized surface plasmon resonance (LSPR) peaks of Au NRs can be adjusted by changing the aspect ratios, and the light absorption range of Au NRs/CNNTs is extended to longer wavelength even near-infrared light. Optimal composition of Pt@Au NR769/CNNT650 has been achieved by adjusting the LSPR peaks of Au NRs and further depositing Pt nanoparticles (NPs), and the photocatalytic H2 evolution rate is 207.0 μmol h?1 (20 mg catalyst). Preliminary LSPR enhancement photocatalytic mechanism is suggested. On one hand, LSPR of Au NRs is beneficial for visible-light utilization. On the other hand, Pt NPs and Au NRs have a synergetic enhancement effect on photocatalytic H2 evolution of CNNTs, in which the local electromagnetic field can improve the photogenerated carrier separation and direct electron transfer increases the hot electron concentration while Au NRs as the electron channel can well restrain charge recombination, finally Pt as co-catalyst can boost H+ reduction rate. This work provides a new way to develop efficient photocatalysts for splitting water, which can simultaneously extend light absorption range and facilitate carrier generation, transportation and reduce carrier recombination.
关键词： synergetic effect,plasmonic photocatalysts,carbon nitride nanotubes,Au nanorods,photocatalytic H2 evolution
更新于2025-09-09 09:28:46
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Investigation of sintering kinetics and morphological evolution of silver films from nano-dispersion
摘要： The present study aimed at investigating the sintering kinetics and the mechanism of achieving uniform film morphology from silver nano-dispersion through evaporation of the solvent. A tuned time elapse between drop casting of silver dispersion and the annealing (dwell-time) acted as the decision maker in engineering the morphology: ring stain (infinite dwell-time), uniform deposit (variable dwell-time) and dot formation (zero dwell-time). Three distinct dwell-times (10, 20 and 30 min) are chosen for the study at different temperatures (120 to 250 °C) and the conclusion is derived based on the profile of the deposit. The frozen morphology that resulted from the evaporation goes through the debonding of surfactant with simultaneous sintering to minimize the surface energy. A linear isothermal sintering model comprising initial grain size, grain growth parameter, annealing time and fractional porosity helps to predict the grain size post-annealing. Theoretical predictions of grain sizes are well matched with experimental ones. The grain growth parameter which shows an upward trend with the annealing temperature is mainly due to a reduction in the porosity and the increase in the fraction of solid–solid interface which shows betterment in the percolation paths available for the movement of carriers.
关键词： sintering kinetics,dwell-time,silver films,nano-dispersion,morphological evolution
更新于2025-09-09 09:28:46
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Research Advances in Quantum Dynamics || Minimum Time in Quantum State Transitions: Dynamical Foundations and Applications
摘要： This chapter is about the minimum time evolution between two quantum states considering the dynamics obeying either time-invariant Hamiltonians or time-varying ones. Merit figures are defined to help quantum control designers to define optimiza‐ tion parameters. The expressions are derived from the time-energy uncertainty relations and a practical case is studied as an example.
关键词： minimum time,quantum evolution,un‐ certainty relations,quantum control,merit figures
更新于2025-09-09 09:28:46
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Hybrid differential evolution algorithms for the optimal camera placement problem
摘要： Purpose – This paper aims to investigate to what extent hybrid differential evolution (DE) algorithms can be successful in solving the optimal camera placement problem. Design/methodology/approach – This problem is stated as a unicost set covering problem (USCP) and 18 problem instances are de?ned according to practical operational needs. Three methods are selected from the literature to solve these instances: a CPLEX solver, greedy algorithm and row weighting local search (RWLS). Then, it is proposed to hybridize these algorithms with two hybrid DE approaches designed for combinatorial optimization problems. The ?rst one is a set-based approach (DEset) from the literature. The second one is a new similarity-based approach (DEsim) that takes advantage of the geometric characteristics of a camera to ?nd better solutions. Findings – The experimental study highlights that RWLS and DEsim-CPLEX are the best proposed algorithms. Both easily outperform CPLEX, and it turns out that RWLS performs better on one class of problem instances, whereas DEsim-CPLEX performs better on another class, depending on the minimal resolution needed in practice. Originality/value – Up to now, the ef?ciency of RWLS and the DEset approach has been investigated only for a few problems. Thus, the ?rst contribution is to apply these methods for the ?rst time in the context of camera placement. Moreover, new hybrid DE algorithms are proposed to solve the optimal camera placement problem when stated as a USCP. The second main contribution is the design of the DEsim approach that uses the distance between camera locations to fully bene?t from the DE mutation scheme.
关键词： Unicost set covering problem,Differential evolution,Hybridization,Optimal camera placement,Row weighting local search,Combinatorial optimization
更新于2025-09-09 09:28:46
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Interfacial Optimization of g-C3N4-based Z-Scheme Heterojunction toward Synergistic Enhancement of Solar-Driven Photocatalytic Oxygen Evolution
摘要： Exploring active catalyst materials for solar-driven photocatalytic water splitting into oxygen has proven extremely challenging, mostly due to poor oxygen-evolving efficiency originating from intrinsically sluggish oxygen evolution reaction (OER) kinetics. Ag3PO4 has been actively pursued as a promising photocatalyst for oxygen evolution from water-splitting. However, its low OER efficiency is a long standing problem. Both the construction of Z-scheme Ag3PO4-based composite photocatalytic systems and the optimization of surface morphology and interfacial contact in heterojunctions photocatalysts would be beneficial for boosting OER efficiency. Here we report on the fabrication of Ag3PO4/fish scale-like graphitic carbon nitride (g-C3N4) sheet composites with well-defined heterostructures and intimate interfacial contact driven by electrostatic assembly. The Ag3PO4/modified g-C3N4 composites photocatalyst reveals significantly enhanced oxygen-evolving activity under light-emitting diode (LED) illumination. Effective surface modification of g-C3N4, strong interfacial interactions between two semiconductors and tandem Z-scheme-type pathway for more efficient charge transfer synergistically accelerates the redox capability of Ag3PO4 for OER. This work may provide new insights into the design and construction of high-performance solar-driven Z-scheme photocatalytic water splitting systems.
关键词： water splitting,Z-scheme,photocatalytic oxygen evolution,g-C3N4,Ag3PO4
更新于2025-09-09 09:28:46
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A new photocatalyst based on Co(CO3)0.5(OH)·0.11H2O/Bi2WO6 nanocomposites for high-efficiency cocatalyst-free O2 evolution
摘要： The practical application of photocatalytic water splitting is essentially limited by the slow kinetic nature of the water oxidation process. Therefore, it is highly desirable but challenging to explore a low-cost and high-efficiency water oxidation catalyst for the aim of commercialization and industrialization. We herein report the first-time synthesis of a novel and high-efficiency visible-light-driven photocatalyst composed of flower-like Co(CO3)0.5(OH)·0.11H2O (CCO) nanowires and Bi2WO6 (BWO) nanosheets, i.e. CCO/BWO nanocomposite, via a facile hydrothermal method. Without utilizing any additional cocatalyst, the composite of CCO/BWO in 30% weight ratio exhibits extraordinarily high photoactivity and photostability towards O2 evolution, achieving an average O2 generation rate of 953 μmol h?1 g?1 under visible-light irradiation (λ > 420 nm).
关键词： Bi2WO6,Nanocomposite,Cocatalyst-free,Photocatalytic O2 evolution,Co(CO3)0.5(OH)·0.11H2O
更新于2025-09-09 09:28:46