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High-temperature tungsten trioxides obtained by concentrated solar energy: physicochemical and electrochemical characterization
摘要： High-crystalline tungsten trioxides (WO3) have been synthesized by an environmentally friendly method using concentrated solar energy. The obtained tungsten trioxides (WO3) at three different temperatures and two oxygen mole fractions used for the highest synthesis temperature were characterized by XRD, SEM, and XPS. Higher crystallinity and concentration of W5+ was observed in tungsten trioxides as the synthesis temperature increased. Nevertheless, despite of the different synthetic conditions used, a mixture of two different crystalline structures was observed in all solar-prepared tungsten trioxides: monoclinic and triclinic. Comparing oxides obtained at 1000 °C, higher concentration of W5+ and more defects were found when using lower oxygen molar fraction (WO3-1000-2). Their electrochemical performance was evaluated using cyclic voltammetry (CV) in a conventional three-electrode cell in the following three aqueous electrolytes: acidic, alkaline, and neutral media. In the acidic medium, all the tungsten trioxides showed a capacitive behavior, which was enhanced for oxides obtained at 1000 °C due to a mixed valence of W. On the other hand, in the alkaline medium, a catalytic behavior was detected with higher activity towards hydrogen evolution reaction for the oxide with more defects, higher crystallinity, and monoclinic phase, obtained at 1000 °C and a lower oxygen molar fraction in the synthesis. Finally, in the neutral medium, the oxides synthesized at 1000 °C presented a capacitive behavior whereas the oxides prepared at the lowest temperatures (600 and 800 °C) presented electrochemical processes related to a catalytic behavior for water reduction, which must correspond to their minor concentration of defects, as confirmed by XPS.
关键词： High-temperature synthesis,Concentrated solar energy,Green synthesis,WO3,Tungsten trioxides
更新于2025-09-04 15:30:14
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Modulation of Excited‐State Proton Transfer Dynamics Inside the Nanocavity of Microheterogeneous Systems: Microenvironment‐Sensitive F?rster Energy Transfer to Riboflavin
摘要： Excited-state proton transfer (ESPT) in a tetraarylpyrene derivative, 1,3,6,8-tetrakis(4-hydroxy-2,6-dimethylphenyl)pyrene (TDMPP), was investigated thoroughly in the presence of various surfactant assemblies such as micelles, vesicles, etc. The surfactants can significantly retard the extent of excited-state proton transfer process, resulting in a distinguishable optical signal compared to that in the bulk medium. Physical characteristics of the surfactant assemblies such as order, interfacial hydration and surface charge influence the proton transfer process, and allow multiparametric sensing. A higher degree of interfacial hydration facilitates the proton transfer process, while the positively charged head groups of the surfactants specifically stabilize the anionic form of the probe (TDMPP-O*). Further, Forster energy transfer from the probe to riboflavin was studied in phospholipid membrane, wherein the relative ratio of neutral vs anionic forms (TDMPP-OH/TDMPP-O*) was found to influence the extent of energy transfer. Overall, we demonstrate how an ultrafast photophysical process, that is, the excited-state proton transfer, can be influenced by microenvironment.
关键词： surfactants,Excited-state proton transfer,Energy transfer,microheterogeneous system,microenvironment
更新于2025-09-04 15:30:14
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Responsive Upconversion Nanoprobe for Background‐Free Hypochlorous Acid Detection and Bioimaging
摘要： Responsive nanoprobes play an important role in bioassay and bioimaging, early diagnosis of diseases and treatment monitoring. Herein, a upconversional nanoparticle (UCNP)-based nanoprobe, Ru@UCNPs, for specific sensing and imaging of hypochlorous acid (HOCl) is reported. This Ru@UCNP nanoprobe consists of two functional components, i.e., NaYF4:Yb, Tm UCNPs that can convert near infrared light-to-visible light as the energy donor, and a HOCl-responsive ruthenium(II) complex [Ru(bpy)2(DNCH-bpy)](PF6)2 (Ru-DNPH) as the energy acceptor and also the upconversion luminescence (UCL) quencher. Within this luminescence resonance energy transfer nanoprobe system, the UCL OFF–ON emission is triggered specifically by HOCl. This triggering reaction enables the detection of HOCl in aqueous solution and biological systems. As an example of applications, the Ru@UCNPs nanoprobe is loaded onto test papers for semiquantitative HOCl detection without any interference from the background fluorescence. The application of Ru@UCNPs for background-free detection and visualization of HOCl in cells and mice is successfully demonstrated. This research has thus shown that Ru@UCNPs is a selective HOCl-responsive nanoprobe, providing a new way to detect HOCl and a new strategy to develop novel nanoprobes for in situ detection of various biomarkers in cells and early diagnosis of animal diseases.
关键词： imaging,nanoprobes,paper-based test strips,bioassay and bioimaging,luminescence resonance energy transfer,selective HOCl detection and imaging
更新于2025-09-04 15:30:14
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Microscopy of the Heart || Optogenetic Tools in the Microscopy of Cardiac Excitation-Contraction Coupling
摘要： Microscopy became a scienti?c investigation method in the seventeenth century with the application of the ?rst build microscopes on biological samples [1, 2]. Soon it became a popular method to stain samples in order to visualise particular (cellular and subcellular) structures [3]. These stains, either based on absorption or ?uorescence, have limitations in respect to their speci?city and are often toxic to cells, which limits investigations to short intervals or even dead samples. In 1987 the idea came up to use a ?uorescent protein that was discovered 25 years before [4], in particular a green ?uorescent protein (GFP) form the medusa Aequorea victoria to label cells and cellular structures [5]. With the sequencing and cloning of GFP, a so-called ‘green revolution’ started, which led to regular usage of ?uorescent proteins as markers or sensors (for details see below) in the majority of cellular research in physiology, microbiology, pharmacology, molecular biology, anatomy, cell biology, biophysics and many other biomedical ?elds. Although the expression of the ?uorescent proteins and their optical investigation can already be regarded as optogenetic tools, this term was only applied when the optical properties of proteins were used to manipulate cells. The best-known example of such a protein is the channelrhodopsin, a light-gated ion channel [6, 7]. When this ion channel is expressed in a membrane and illuminated with light of the appropriate wavelength, the channel will be activated and opened, which results in passive transportation of ions across the membrane and a change of the membrane potential. However, within this chapter we consider both aspects, the observation and the manipulation as optogenetic tools. To use the optogenetic tool, the genes of these proteins need to be transferred into the cells to allow the expression of the protein. For an overview of gene delivery into target cells, see [8].
关键词： channelrhodopsins,cardiac excitation-contraction coupling,F?rster Resonance Energy Transfer,genetically encoded biosensors,Optogenetic tools,microscopy
更新于2025-09-04 15:30:14
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Density-functional-theory calculations of structural and electronic properties of vacancies in monolayer hexagonal boron nitride (h-BN)
摘要： We have carried out the density functional theory calculations of vacancies in monolayer h-BN. We model five configurations, two configurations of monovacancies (VB and VN) and three configurations (VBB, VNN, and VBN) of divacancies. In the case of monovacancies, we find that VB and VN form a C3V symmetry. In the divacancy case, we find that VNN produces a heart-like configuration having two pentagons and leaving two dangling bonds, while VBB leaves four dangling bonds. As for VBN, it produces two pentagons and has no dangling bond. The calculated formation energies of VB; VN; VBB; VNN, and VBN are 11.65 eV, 12.05 eV, 17.59 eV, 22.32 eV, and 16.89 eV, respectively. These energies show that VB is more stable than VN, while VBB is more stable than VNN. We conclude that the N-rich h-BN sheet is energetically more favorable to be formed rather than the B-rich one. However, the most stable configuration of the divacancies belongs to VBN compensating from the absence of the dangling bond, which obeys the dangling-bond-counting-model. Furthermore, we calculate band structures of the most stable mono- and divacancies. We find that monovacancy somewhat changes the electronic structure, shown by localized states near the Fermi level, while the divacancy produces two new states above the Fermi level.
关键词： B-N vacancies,Electronic structure,Formation energy
更新于2025-09-04 15:30:14
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Design and energy transfer mechanism for single-phased Gd2MgTiO6: Bi3+, Eu3+ tunable white light-emitting phosphors
摘要： In recent years, numerous efforts have been made to develop single-phased white light-emitting phosphors for the near-UV region to solve problems of color reabsorption and ratio regulation between different phosphors. In this work, we have designed Bi3+- and Eu3+-codoped single-phased Gd2MgTiO6 phosphors to achieve tunable white light emission based on multi-luminescence center energy transfer. The structural analysis showed that all the samples were crystallized as a monoclinic double perovskite with the P21/n symmetry space group (No. 14), with HRTEM images showing clear lattice fringes between the lattice planes. The single Bi3+-doped Gd2MgTiO6 sample exhibits two obvious emission peaks at 417 and 508 nm, which correspond to a characteristic 3P1 → 1S0 transition for the Bi3+ ions under near-UV excitation due to two types of Bi3+ emission centers, with their relative emission intensity depending closely on the value of the excitation wavelength. In this case, a suitable choice of excitation wavelength can achieve tunable emission for Gd2MgTiO6: Bi3+ between blue and green. Eu3+ is codoped into Gd2MgTiO6 as a red emission component and shows sharp emission lines that correspond to the characteristic 5D0 → 7FJ (J = 1, 2, 3, and 4) transitions of Eu3+ ions. Energy transfer in Gd2MgTiO6: Bi3+, Eu3+ has been confirmed by the electric dipole–dipole (d–d) interaction from Bi3+ to Eu3+. Our experiments show that it is straightforward to create tunable white light emission by adjusting the excitation scheme and Eu3+ concentration. Moreover, a schematic for the energy transfer mechanism and simplified spectral levels based on Bi3+ and Eu3+ ions has also been established.
关键词： Eu3+,Bi3+,Gd2MgTiO6,white light-emitting phosphors,energy transfer,tunable emission,near-UV
更新于2025-09-04 15:30:14
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Potential, optimization and sensitivity analysis of photovoltaic-diesel-battery hybrid energy system for rural electrification in Algeria
摘要： Integration of hybrid renewable energy systems (HRES) as an electrification solution can enhance the rural electrification situation in Algeria's predominantly remote Saharan regions, where diesel generators are used to provide very basic and limited electricity service. The exploitation of such a solution requires a sustainable, optimized HRES design. This paper presents a methodology both to optimize and to perform a sensitivity analysis of an autonomous hybrid PV-diesel-battery energy system. Particle Swarm Optimization (PSO) and ε-constraint method were used to simultaneously minimize total system cost, unmet load, and CO2 emissions. One optimal solution was chosen among the solutions set and analyzed. The remote Saharan village of Tiberkatine, province of Tamanrasset in southern Algeria was considered as a case study. The hybrid system supplied the energy demand of 20 households. It was found that the optimal solution can supply energy without unmet load, the minimum cost of energy COE is 0.37 $/kWh with 93% renewable fraction. A sensitivity analysis was performed on the optimal system to study the impact of three parameters (load consumption, εCO2, and εLLP constraints) on the system behavior. Finally, a comparative analysis between PSO and HOMER was performed, it was found that the PSO based approach is more cost effective with more PV penetration than HOMER.
关键词： Photovoltaic,Diesel,PSO optimization,Rural electrification,Hybrid renewable energy system
更新于2025-09-04 15:30:14
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Oxygen and cerium defects mediated changes in structural, optical and photoluminescence properties of Ni substituted CeO2
摘要： Local and long-range structural properties, of sol-gel synthesized, Ce1-xNixO2 (0 ≤ x ≤ 0.1) nanopowders have been investigated. Substitution of Ce4+ by comparably smaller Ni2+/Ni3+ ions leads to decrement in lattice parameters. UV-visible spectra reveal decrease of bandgap with increase of disorder upon increasing Ni substitution. The photoluminescence (PL) spectra reveal five major peaks attributed to various defect states. Ni substitution results in the creation of oxygen vacancies (VO) which further leads to conversion of considerable amount of Ce4+ ions to larger size Ce3+. These changes notably, modify the structure of the host lattice. The defects created along with the structural modifications bring, changes in the PL emission. The disorder in the lattice results in increase of non-radiative decay which reduces the PL emission. An increasing VO and Ce3+ concentration at the surface acts as emission quenching centers. Lattice disorder and VO quantities were estimated using X-ray absorption (XAS), UV-vis and Raman spectroscopy.
关键词： Nanoparticles,Urbach energy,Cerium oxide,Strain,Bandgap
更新于2025-09-04 15:30:14
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The Middle Road Less Taken: Electronic-Structure-Inspired Design of Hybrid Photocatalytic Platforms for Solar Fuel Generation
摘要： The development of efficient solar energy conversion to augment other renewable energy approaches is one of the grand challenges of our time. Water splitting, or the disproportionation of H2O into energy-dense fuels, H2 and O2, is undoubtedly a promising strategy. Solar water splitting involves the concerted transfer of four electrons and four protons, which requires the synergistic operation of solar light harvesting, charge separation, mass and charge transport, and redox catalysis processes. It is unlikely that individual materials can mediate the entire sequence of charge and mass transport as well as energy conversion processes necessary for photocatalytic water splitting. An alternative approach, emulating the functioning of photosynthetic systems, involves the utilization of hybrid systems wherein different components perform the various functions required for solar water splitting. The design of such hybrid systems requires the multiple components to operate in lockstep with optimal thermodynamic driving forces and interfacial charge transfer kinetics.
关键词： hybrid systems,water splitting,photocatalytic,charge transfer,solar energy conversion
更新于2025-09-04 15:30:14
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Resonance Energy Transfer in Arbitrary Media: Beyond the Point Dipole Approximation
摘要： In this work, we present a comprehensive theoretical and computational study of donor/acceptor resonance energy transfer (RET) beyond the dipole approximation, in arbitrary inhomogeneous and dispersive media. The theoretical method extends Fo?rster theory for RET between particles (molecules or nanoparticles) to the case where higher multipole transitions in the donor and/or acceptor play a significant role in the energy transfer process. In our new formulation, the energy transfer matrix element is determined by a fully quantum electrodynamic expression, but its evaluation requires only classical electrodynamics calculations. By means of a time domain electrodynamical approach (TED), the matrix element evaluation involves the electric and magnetic fields generated by the donor and evaluated at the position of the acceptor, including fields associated with transition electric dipoles, electric quadrupoles, and magnetic dipoles in the donor, and the acceptor response to the electric and magnetic fields and to the electric field gradient. As an illustration of the benefits of the new formalism, we tested our method with a 512 atom lead sulfide (PbS) quantum dot as the donor/acceptor in vacuum, and with spherical nanoparticles (toy model) possessing designed transition multipoles. This includes an analysis of the effects of interferences between multipoles in the energy transfer rate. The results show important deviations from the conventional Fo?rster dipole theory that are important even in vacuum but that can be amplified by interaction with a plasmonic nanoparticle.
关键词： multipole transitions,resonance energy transfer,plasmonic nanoparticle,quantum electrodynamics,dipole approximation,RET
更新于2025-09-04 15:30:14