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Visible light active titanates photosensitized by Ti(IV) surface complexes
摘要： For the first time, photosensitization of selected alkaline titanates with surface charge transfer complexes has been proven. Activation of BaTiO3, SrTiO3 and CaTiO3 to visible as well as ultraviolet light has been achieved by impregnation with catechol, salicylic acid and 2,3-naphthalenediol. Simple modification of titanates with organic compounds forming inner-sphere CT complexes with Ti atoms located at the surface of semiconductors resulted in coloration of the materials. Even though acceptor electronic states of titanates are characterized by a higher energy compared with titania (even up to 0.75 eV higher for CaTiO3), complexes formed at titanates’ surface absorb in similar or even broader optical range of visible light. Beside changes in the absorption properties, used modifications also strongly influenced their photoelectrochemical and photocatalytic properties. In contrast to similarly modified titanium dioxide, modified titanates show significantly improved photocatalytic activity not only under visible light but also within ultraviolet range of radiation. Remarkably increased efficiency of photocurrent generation within the UV range of radiation may suggest that apart from observed electron transfer from HOMO of the complex to conduction band (CB) of the semiconductor also indirect photosensitization mechanism through the electron transfer from the excited complexes to the CB of titanates may take place.
关键词： photosensitization,visible light activity,surface complexes,titanates,charge transfer
更新于2025-09-23 15:21:21
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Polyoxometalate as Control Agent for the Doping in HgSe Self-Doped Nanocrystals
摘要： Intraband and plasmonic transitions have appeared over the last years as an interesting tool to achieve optical absorption in the mid infrared. Tuning the doping magnitude has become a major challenge not only to tune the optical spectrum but also properties such as the dark current or the time response. Here we investigate the case of self-doped HgSe colloidal quantum dots (CQDs). Tuning of the doping was so far relying on band bending induced by a dipole design at the nanoparticle surface. With such a surface gating approach, it is difficult to conciliate both the massive tuning of the Fermi level with the preservation of transport properties of the CQD arrays. Here we propose a strategy to graft functionalized polyoxometalates (POMs) at the CQD surface and obtain simultaneously a massive tuning of the carrier density (≈5 electrons per nanoparticle) and conduction properties. We bring a consistent demonstration of the HgSe CQD doping decrease by a charge transfer to the POM. This method is highly promising for large tuning of carrier density in degenerately doped semiconductor nanoparticles.
关键词： Intraband,mid infrared,charge transfer,polyoxometalates,plasmonic transitions,doping control,HgSe colloidal quantum dots
更新于2025-09-23 15:21:21
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Surface-nanostructured single silver nanowire: a new one-dimensional microscale SERS interface
摘要： One-dimensional microscale SERS-active interfaces have been intriguing as a newly emerging class of SERS interfaces compared to conventional macroscale SERS substrates. In this work, a stable surface-nanostructured single silver nanowire was fabricated. The nanostructures on the nanowire are formed by nanoscale silver crystal dots with diameters of 20-50 nm. The SERS signals of the crystal violet probe molecules adsorbed on the nanostructures are dramatically enhanced by both electromagnetic and chemical effects. The hot spots generated at the junctions of adjacent nanoscale dots yield highly efficient surface plasmon resonance. Simultaneously, the charge transfer on the atomic-scale silver cluster located at the nanostructured interface causes an enhancement similar to a Raman resonance. The intensity distributions of the SERS peaks on the surface-nanostructured single nanowire are characterized by SERS mapping. It is found that, although the intensities of the SERS peaks are different, their SERS mapping images show uniform SERS enhancement distributions, whereas the noticeable SERS intensity distributions on the single smooth silver nanowire are mainly located on the two ends of the nanowire. The large number of nanoscale crystal dots along with the atomic-scale silver clusters are uniformly and densely distributed on the surface of the single roughened nanowire; these structural attributes induce a uniform and large surface plasmon resonance and charge transfer enhancements on the entire surface of the nanowire. This work indicates that the surface-nanostructured single silver nanowire, synthesized using a quite simple preparation method, performs as an excellent one-dimensional microscale SERS substrate with uniform and high enhancement characteristics, which shows high potential for applications as a new class of SERS-active substrates. Furthermore, the higher enhancement factor of the microscale SERS interfaces can be achieved by introducing other roughened nanowires to assemble a dimer and a trimer as micro SERS substrates, which is consistent with the dark field (DF) measurements.
关键词： Hot spots,Raman,Micro SERS interfaces,Charge transfer,Silver nanowire
更新于2025-09-23 15:21:21
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p-Doping Poly(3-hexylthiophene) in Solvent Mixtures
摘要： One method to improve the conductivity of conjugated polymers, like poly(3-hexylthiophene) (P3HT), is to “chemically dope” them analogous to inorganic materials. One electron acceptor that has been used in tandem to p-doped P3HT is 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), and recently there has been much interest in the nature of the interactions between F4TCNQ and P3HT in the solution phase. To date, however, there are few reports that investigate the behavior of F4TCNQ-doped P3HT in binary solvent mixtures. The study reported herein is an investigation of F4TCNQ-doped P3HT in mixtures of chloroform (CF) with dichloromethane (DCM) or acetonitrile (AcN), wherein variations in the doping efficiency in these mixtures are observed using UV–vis absorption, Raman, and electron paramagnetic resonance spectroscopic techniques. The contrasting solubility and charge transfer behavior of F4TCNQ-doped P3HT in CF:DCM and CF:AcN show that judicious selection of solvent mixtures may be exploited to improve the doping efficiency and solution processability of p-doped P3HT dispersions.
关键词： dispersions,charge transfer,conjugated polymers,self-assembly
更新于2025-09-23 15:21:21
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Luminescence and reactivity of a charge-transfer excited iron complex with nanosecond lifetime
摘要： Iron’s abundance and rich coordination chemistry are potentially appealing features for photochemical applications. However, the photoexcitable charge-transfer (CT) states of most Fe complexes are limited by picosecond or sub-picosecond deactivation through low-lying metal centered (MC) states, resulting in inefficient electron transfer reactivity and complete lack of photoluminescence. Here we show that octahedral coordination of Fe(III) by two mono-anionic facial tris-carbene ligands can suppress such deactivation dramatically. The resulting complex [Fe(phtmeimb)2]+, where phtmeimb is [phenyl(tris(3-methylimidazol-1-ylidene))borate]-, exhibits strong, visible, room temperature photoluminescence with a 2.0 ns lifetime and 2% quantum yield via spin-allowed transition from a ligand-to-metal charge-transfer (2LMCT) state to the ground state (2GS). Reductive and oxidative electron transfer reactions were observed for the 2LMCT state of [Fe(phtmeimb)2]+ in bimolecular quenching studies with methylviologen and diphenylamine.
关键词： charge-transfer,iron complex,electron transfer,photoluminescence,N-heterocyclic carbene
更新于2025-09-23 15:21:01
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Dual-Emission and Two Charge Transfer States in Ytterbium-Doped Cesium Lead Halide Perovskite Solid Nanocrystals
摘要： Some unusual phenomena besides near-infrared emission of Yb3+ ions have been observed in ytterbium-doped perovskite solid nanocrystals. A systematic study on doping kinetic and energy transfer processes is presented. The observed unique dual-peak PL emission of perovskite nanocrystals in the visible region can be attributed to radiative recombination in the near-surface region and the interior region of perovskite nanocrystals respectively. Insight studies based on dual-peak PL emission clarify the kinetic process of doping in perovskite nanocrystals. After dopant concentration of rare earth ions in the near-surface region is more than a certain value, dopant ions are starting to be immersed into the interior region of host nanocrystals. The unusual excitation spectra of ytterbium-doped perovskite solid nanocrystals could be explained by the presences of two charge transfer (CT) states at ~24000 cm-1 (CT1) and ~21460 cm-1 (CT2), and both of them could be observed in the near-surface region of the perovskite host. Furthermore, the lifetime of near-infrared emission of Yb3+ ions through the CT2 state is three orders faster than that through CT1 state (in millisecond) which should be fixed on the surface of perovskite nanocrystals. The results provide essential insights into the dynamic carrier behaviors and surface effects of all inorganic perovskite nanocrystals doped with rare earth ions for expanded functionality.
关键词： dual-emission,kinetic process,rare earth,charge transfer states,Perovskite solid nanocrystals,energy transfer
更新于2025-09-23 15:21:01
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Photogenerated-Carrier Separation and Transfer in Two-Dimensional Janus Transition Metal Dichalcogenides and Graphene van der Waals Sandwich Heterojunction Photovoltaic Cells
摘要： Two-dimensional (2D) Janus transition metal dichalcogenides (JTMDs) show direct band gaps and strong visible-light absorption with promising applications in photovoltaic (PV) cells. Here, we investigate the electronic structures and dynamics of photogenerated carriers in 2D JTMDs and graphene van der Waals sandwich heterojunction (G/JTMDs/G) photovoltaic cells by using first-principles calculations. We find that the intrinsic built-in electric field in JTMDs results in an asymmetry potential, which can be used to effectively enhance the separation and transfer of photogenerated carriers from JTMDs to different graphene layers with a preferred direction within hundreds of femtoseconds in the G/JTMDs/G heterostructures. Furthermore, the photogenerated electrons (holes) can transfer from monolayer MoSSe (MoSeTe) to the graphene sheets by the Se side with lower (higher) potential, while the transfer of the photogenerated holes (electrons) is prohibited due to the large separation between donor and acceptor states.
关键词： First-principles calculations,van der Waals heterostructures,Janus transition metal dichalcogenides,Photogenerated carriers,Two-dimensional materials,Graphene,Charge transfer,Photovoltaic cells
更新于2025-09-23 15:21:01
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Interfacial engineering revolutionizers: perovskite nanocrystals and quantum dots accentuated performance enhancement in perovskite solar cells
摘要： Utilization of efficient nanomaterials in perovskite solar cells (PSCs) for effectual conversion of solar energy to electrical energy has prompted the extensive progression of PSCs as a suitable alternative to silicon-based photovoltaic (PV) technologies. Most recent progressions are inclusive of nanoscale materials incorporation particularly nanocrystals (NCs) and quantum dots (QDs) with unique sizes, morphological and compositional aspects aimed at PSCs modification. In all conventional architectures of the PSCs, there are number of interfaces between the transport layers and active absorber perovskite layer. Nanocrystals and quantum dots have been employed for the interfacial engineering in PSCs owing to their remarkable optoelectronic and photo-physical characteristics favoring the facile and efficient power generation and reducing dependence on silicone-based PVs. Myriad of NCs and QDs having inorganic and/or inorganic perovskite composition have been investigated, however, the overall synthetic costs, procedural complications, current, and voltage (J–V) hysterical response and stability toward air and light needs further meticulous investigations due to which PV community has been disseminating experimental results rapidly since last few years. Considering the potential of perovskite NCs and QDs, current review has for the first time explored the most recent progressions done in utilization of these nanoscale materials in augmenting PSCs PV functionality through interface modification. Magnifying extent of nanoscale materials for PSCs modification and current investigation signifies the future candidacy of perovskite NCs and QDs as humanity gallants for provisioning of cheaper and sustainable power sources.
关键词： Absorptivity,photovoltaics,bandgap,diffusion length,charge transfer
更新于2025-09-23 15:21:01
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Osmium sensitizer with enhanced spin-orbit coupling for panchromatic dye-sensitized solar cells
摘要： Low-lying triplet metal-to-ligand charge transfer (3MLCT) transitions of osmium complexes induced by spin-orbit coupling (SOC) is promising to extend photocurrent response when applied to dye-sensitized solar cells. In this study, we present a newly designed osmium complex (coded CYC-33O), incorporating a 2-thiohexyl-3,4-ethylenedioxythiophene functionalized bipyridyl ancillary ligand to red-shift the absorption and enhance the absorbance of both singlet and triplet MLCT transitions. Time-dependent density functional theory (TDDFT) calculations clearly signify the reinforced 1MLCT and 3MLCT transitions of CYC-33O mainly originate from osmium to 4,4',4"-tricarboxy-2,2':6',2"-terpyridine anchoring ligand, advantaging the heterogeneous electron transfer between CYC-33O and TiO2. The device sensitized with CYC-33O exhibits the panchromatic conversion beyond 1000 nm, yielding the photocurrent density of 19.38 mA cm–2 which is much higher than those of the cells based on the ruthenium analogue (CYC-33R) and model osmium complex (Os-3) sensitizers.
关键词： dye-sensitized solar cell,triplet metal-to-ligand charge transfer (3MLCT),ruthenium complex,spin-orbit coupling (SOC),osmium complex,time-dependent density functional theory (TDDFT)
更新于2025-09-23 15:21:01
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Effect of intermolecular interaction on excited-state properties of thermally activated delayed fluorescence molecules in solid phase: A QM/MM study
摘要： Recently, thermally activated delayed fluorescence (TADF) molecules have attracted great attention since nearly 100% exciton usage efficiency was obtained in TADF molecules. Most TADF molecules used in organic light-emitting diodes are in aggregation state, so it is necessary to make out the intermolecular interaction on their photophysical properties. In this work, the excited-state properties of the molecule AI-Cz in solid phase are theoretically studied by the combined quantum mechanics and molecular mechanics (QM/MM) method. Our results show that geometry changes between the ground state (S0) and the first singlet excited state (S1) are limited due to the intermolecular π-π and CH-π interactions. The energy gap between S1 and the first triplet excited state is broadened and the transition properties of excited states are changed. Moreover, the Huang-Rhys factors and the reorganization energy between S0 and S1 are decreased in solid phase, because the vibration modes and rotations are hindered by intermolecular interaction. The non-radiative rate has a large decrease in solid phase which improves the light-emitting performance of the molecule. Our calculation provides a reasonable explanation for experimental measurements and highlights the effect of intermolecular interaction on excited-states properties of TADF molecules.
关键词： Hybridized local and charge transfer state,Thermally activated delayed fluorescence,Intermolecular interactions,QM/MM method
更新于2025-09-23 15:21:01