Building a highly concentration responsive optical thermometer via tunable electron transfer pathways supported by intervalence charge transfer states.

The thermal-coupled levels (TCLs) of lanthanides have attracted great attention in the field of optical thermometer, offering an efficient method to achieve non-contect temperatuer feedback in complex environment. However, the iner 4f electrons are shielded, which becomes the core obstacle in improving the sensing performance. This issue is now circumvented by constructing an electron transfer pathway between Tm3+(1D2) and Eu3+(5D0) configurations. As a result, the electron transfer barrier is related to the relative temperature sensitivity, giving an insight into the modulation mechanism. Compared to the conventional TCLs systems, the relative temperature sensitivity of this strategy is highly concentration-responsive, increasing from 5.56 to 10.1 % K-1 as the Eu3+ molar concentration rises from 0.3 to 0.5 mol%. This work reveals the inner emission mechanism based on IVCT-supported emission mode, and presents the highly adjustability of sensing performance.

Tailoring refractive index dispersion in ionic liquids: The influence of charge delocalization in cations.

In this work, we study the contributions that different molecular blocks have in the wavelength-dependence of the refractive index in ionic liquids. The ionic liquids chosen for this work are combinations of the bis(trifluoromethylsulfonyl)imide anion with cations based on four different heterocycles with different extents of charge delocalization. The analysis is performed in terms of the experimental electronic polarizability, which is obtained by combining measurements of refractive index curves and densities via the Lorentz-Lorenz equation. Exploiting the additivity of electronic polarizability in ionic liquids, the contribution of the anion and the heterocycles of the cations is separated from that of the alkyl chains. Our results show important differences in these contributions, revealing a key influence of the charge delocalization in the cationic rings on the behavior of the refractive index dispersion. The understanding of how different parts of ionic liquids affect their refractive index dependence on wavelength would allow to gain precise control of this magnitude, enabling the development of customized optical materials for diverse applications in photonics and sensing technologies.

Phosphorus and sulfur co-doped nickel molybdate with rich-oxygen vacancies for efficient water splitting.

The rational design of high-performance electrocatalysts is essential for promoting the industrialization of electrocatalytic water-splitting technology. Herein, phosphorus and sulfur co-doped nickel molybdate with rich-oxygen vacancies (P, S-NiMoO4) was prepared as an efficient bifunctional self-supporting water-splitting catalyst from the perspective of enhancing the conductivity and optimizing the electronic configurations. The incorporation of P, S and oxygen vacancies greatly enhances the conductivity and charge-transfer efficiency of NiMoO4. Additionally, P and S can serve as proton carriers and electron acceptors to enhance the catalytic activity by accelerating proton activation and high-valent metal generation in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). As expected, P, S-NiMoO4 demonstrates efficient bifunctional catalytic activity with an overpotential of only 31/206 mV at 10 mA cm-2 for HER/OER in 1 M KOH. Meantime, the electrolyzer assembled with P, S-NiMoO4 as electrodes requires a voltage of only 1.55 V to achieve a water-splitting current density of 50 mA cm-2 along with good stability over 110 h. This work puts forward a novel approach based on elemental doping and vacancy engineering for the design of effective and enduring catalysts for water splitting.

Facilitating charge transfer via a Semi-Coherent Fe(PO3)2-Co2P2O7 heterointerface for highly efficient Zn-Air batteries.

Developing reversible oxygen electrodes for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial for achieving high-performance rechargeable Zn-air batteries (ZABs). This study introduced an nitrogen-doped carbon confined with a semi-coherent Fe(PO3)2-Co2P2O7 heterojunction for bifunctional oxygen electrocatalysis. This nanocomposite yielded an ORR half-wave potential of 0.908 V and an OER overpotential of 291 mV at 10 mA/cm2. ZABs incorporating this catalyst yielded impressive performance, including a peak power density of 203 mW/cm2, a specific capacity of 737 mAh/gZn, and promoted stability. Both experimental and theoretical simulations demonstrated that the unique electric field between Fe(PO3)2 and Co2P2O7 promoted efficient charge transport across the heterointerface. This interaction likely modulated the d-band center of the heterojunction, expedite the desorption of oxygen intermediates, thus improving oxygen catalysis and, consequently, ZAB performance. This work illustrates a significant design principle for creating efficient bifunctional catalysts in energy conversion technologies.

Engineering S-scheme mCN@mPDIP molecular heterojunction with highly efficient interface charge transfer for photocatalytic aerobic oxidation synthesis.

The construction of S-scheme heterojunctions, which offers a promising approach for spatially separating photogenerated charge carriers with high redox potentials and multimolecular activation, represents a viable modification strategy in photocatalytic applications. However, the prevalent insufficient contact areas between two components result in low interface charge transfer efficiency, thereby impeding the photocatalytic performance of such heterostructures. Herein, we address this limitation by introducing a unique mCN@mPDIP molecular heterojunction through a pH-triggered molecule self-assembly eutectoid technique, enabling intimate interface contact and promoting highly efficient interfacial charge transfer following an S-scheme mechanism. Consequently, the mCN@mPDIP molecular heterojunction achieves significantly improved charge separation efficiency and higher concentration of active carriers compared to typical bCN-bPDIP bulk heterojunction and nCN/nPDIP nano heterojunction. Combined with the effective sulfide activation on mPDIP sites and O2 activation on mCN sites, the resulting mCN@mPDIP demonstrates outstanding activity in the photocatalytic aerobic oxidation of sulfides into sulfoxides without any redox mediators.

Planar Chiral Charge-Transfer Cyclophanes: Convenient Synthesis, Circularly Polarized Light-Responsive Photothermal Conversion and Supramolecular Chiral Assembly.

We report herein a series of macrocycles in which the densely π-stacked charge-transfer (CT) donor/acceptor with naphthalenediimides (NDIs) or perylene diimide (PDI) as acceptor moiety pairing various donor moieties are locked by covalent bond. The X-ray crystallography of C8BDT-NDI reveals a short intramolecular π-stacking distance around 3.4 Å and the existence of intermolecular donor/acceptor π-stacking (3.7 Å). The intramolecular CT is highly dependent on the electron-donating ability of donor moiety and replacing carbazole (C8KZ) with benzo[1,2-b:4,5-b']dithiophene (C8BDT) or dihydroindolo[3,2-b]indole (C8DN) redshift CT absorption into NIR region. Notably, both C8BDT-NDI and C8DN-NDI demonstrate excellent photothermal performance, which is a result of the active non-radiative pathways. Interestingly, the different molecular symmetry between donor and acceptor moiety endows C8BDT-NDI and C8DN-NDI with intrinsic planar chirality. The enantiomeric C8BDT-NDI shows chiral selectivity for incident light, i.e., when irradiated by left-circularly polarized light, (R)-C8BDT-NDI is more sensitive and a higher maximum stable temperature is achieved. While, enantiomeric C8DN-NDI pack with different orientations forming M- and P-handedness helix, respectively, demonstrating molecular planar chirality being transferred and amplified through molecular assembly. These results provide insight into the intramolecular charge transfer in enforced D/A π-stacks in which CT interactions and planar chirality would be engineered through structural control.

Building Asymmetric Zn-N3 Bridge between 2D Photocatalyst and Co-catalyst for Directed Charge Transfer toward Efficient H2O2 Synthesis.

Two-dimensional (2D) polymeric semiconductors are a class of promising photocatalysts; however, it remains challenging to facilitate their interlayer charge transfer for suppressed in-plane charge recombination and thus improved quantum efficiency. Although some strategies, such as π-π stacking and van der Waals interaction, have been developed so far, directed interlayer charge transfer still cannot be achieved. Herein, we report a strategy of forming asymmetric Zn-N3 units that can bridge nitrogen (N)-doped carbon layers with polymeric carbon nitride nanosheets (C3N4-Zn-N(C)) to address this challenge. The symmetry-breaking Zn-N3 moiety, which has an asymmetric local charge distribution, enables directed interfacial charge transfer between the C3N4 photocatalyst and the N-doped carbon co-catalyst. As evidenced by femtosecond transient absorption spectroscopy, charge separation can be significantly enhanced by the interfacial asymmetric Zn-N3 bonding bridges. As a result, the designed C3N4-Zn-N(C) catalyst exhibits dramatically enhanced H2O2 photosynthesis activity, outperforming most of the reported C3N4-based catalysts. This work highlights the importance of tailoring interfacial chemical bonding channels in polymeric photocatalysts at the molecular level to achieve effective spatial charge separation.

Phase Distribution Dictates Charge Transfer and Transport Dynamics in Layered Quasi-2D Perovskite.

Strategic manipulation of spatiotemporal evolution of charge carriers is critical for optimizing performance of quasi-two-dimensional (2D) perovskite-based optoelectronic devices. Nonetheless, the inhomogeneous phase distribution and band alignment engender intricate energy landscapes, complicating internal charge and energy funneling processes. Herein, we integrate high spatiotemporal resolution transient absorption microscopy with multiple time-resolved spectroscopy and find that asynchronous electron and hole transfers rather than direct energy transfer govern the funneling mechanisms. Notably, the charge funneling pathways and transport behaviors can be modifiable by phase manipulation. The accumulation of small-n phases suppresses the electron funneling toward large-n phases and doubles the carrier diffusion rate from 0.085 to 0.20 cm2/s, yielding a 1.5-fold enhancement in diffusion length. Phase order engineering is further corroborated for facilitating charge separation. Our investigation underscores the prospects of manipulating the phase distribution to control internal charge funneling and transport, thereby substantiating the theoretical foundations for optimizing optoelectronic devices.

POD-like nanozyme constructed from perspective of charge transfer engineering for biosensing of magnetic separation treated Listeria monocytogenes.

For foodborne pathogens pose a serious threat to public health, a magnetic separation strategy and a nanozyme-based biosensor are proposed for biosensing of Listeria monocytogenes (L. monocytogenes). In this work, doripenem is selected as a recognized molecule for the modification of magnetic beads to capture L.monocytogenes in food and environmental samples. Furthermore, the POD-like MXene-Hemin-Au is constructed from perspective of charge transfer engineering which provides a vivid example to rational design of nanozymes. Finally, the captured L.monocytogenes is labeled with MXene-Hemin-Au@mAb, forming the sandwich complexes for quantitative determination. The current signals that generated by the complexes exhibit a good linear relationship with a limit of detection of 2.3 × 101 CFU/mL. The biosensor shows a satisfactory applicability in real samples with recoveries of 91.19% to 102.98%. Overall, the biosensor with integrated magnetic separation strategy presents a potential approach for high sensitivity biosensing of foodborne pathogens.

Unraveling the Spin-to-Charge Current Conversion Mechanism and Charge Transfer Dynamics at the Interface of Graphene/WS2 Heterostructures at Room Temperature.

We report experimental investigations of spin-to-charge current conversion and charge transfer (CT) dynamics at the interface of the graphene/WS2 van der Waals heterostructure. Pure spin current was produced by the spin precession in the microwave-driven ferromagnetic resonance of a permalloy film (Py=Ni81Fe19) and injected into the graphene/WS2 heterostructure through a spin pumping process. The observed spin-to-charge current conversion in the heterostructure is attributed to the inverse Rashba-Edelstein effect (IREE) at the graphene/WS2 interface. Interfacial CT dynamics in this heterostructure was investigated based on the framework of the core-hole clock (CHC) approach. The results obtained from spin pumping and CHC studies show that the spin-to-charge current conversion and charge transfer processes are more efficient in the graphene/WS2 heterostructure compared to isolated WS2 and graphene films. The results show that the presence of WS2 flakes improves the current conversion efficiency. These experimental results are corroborated by density functional theory (DFT) calculations, which reveal (i) Rashba spin-orbit splitting of graphene orbitals and (ii) electronic coupling between graphene and WS2 orbitals. This study provides valuable insights for optimizing the design and performance of spintronic devices.

Reinforced interfacial coupling effect of NiO/Ni2P by Fe doping for boosting water splitting.

Nickel-based catalysts are suitable for water splitting to generate hydrogen. However, the low conductivity and weak stability have always been urgent issues to be addressed in nickel-based catalysts. Fe-doped nickel oxide/nickel phosphide (Fe-NiO/Ni2P) was prepared as a bifunctional electrocatalyst by doping metal and constructing heterogeneous interface. The introduction of Fe contributed to the reinforced interfacial coupling effect of NiO/Ni2P to promote charge transfer and accelerate reaction kinetics. The heterojunction regulated the interfacial charge density between NiO and Ni2P to improve the electronic environment of Ni2+ and enhance conductivity. The O-Fe-P bond at the heterogeneous interface induced the directional transfer of electrons and ensured the structure stability. The synergistic effect of Fe doping and heterogeneous interface increased the adsorption energy of *O and coordinated the adsorption energy of *H, advancing the catalytic performance. Fe-NiO/Ni2P exhibited the overpotential of 242 mV and 141 mV at 10 mA cm-2 for oxygen and hydrogen evolution, respectively.

Enhancing Phototoxicity in BODIPY-perylene Charge Transfer Dyads by Combined Iodination and Mesylation.

The uptake and phototoxicity of a family of BODIPY-perylene charge transfer dyads are compared in live cancer non-cancer cell lines to evaluate their performance in Imaging and photodynamic therapy (PDT). The impact of iodination and mesylation of the meso position of the compounds on their optical properties, cell uptake and toxicity are compared. Notably, across all derivatives the probes were minimally dark toxic up to 50 µM, (the maximum concentration tested), but exhibited outstanding phototoxicity with nanomolar IC50 values and impressive phototoxic indices (PI, ratio of dark IC50 to light IC50), with best performance for the mesylated iodinated derivative. This compound, MB2PI had a PI of >218 and >8.9 in MCF-7 cells and in tumor spheroids respectively. This is significantly higher than non-iodinated analogue, M2P, in MCF-7 cells with an observed PI of >109 and slightly higher than MB2PI in spheroids with a PI of >8.. This compound also showed interesting emission spectral variation with localisation that responded to stimulation of inflammation. Additional studies confirmed efficient singlet oxygen generation by the BODIPYs, suggesting a Type II mechanism of phototoxicity. Overall, the data indicates that combining charge transfer and iodination is an effective strategy for enhancing phototherapeutic capacity of  BODIPY PS.

Unveiling peripheral symmetric acceptors coupling with tetrathienylbenzene core to promote electron transfer dynamics in organic photovoltaics.

Non-fullerene organic compounds are promising materials for advanced photovoltaic devices. The photovoltaic and electronic properties of the derivatives (TTBR and TTB1-TTB6) were determined by employing density functional theory (DFT) and time-dependent density functional theory (TD-DFT) analyses using the M06/6-311G(d,p) functional. To enhance the effectiveness of fullerene-free organic photovoltaic cells, modifications were applied to end-capped acceptors by using strong electron-withdrawing moieties. The structural tailoring showed a significant electronic impact for HOMO and LUMO for all chromophores, resulting in decreased band gaps (3.184-2.540 eV). Interestingly, all the designed derivatives exhibited broader absorption spectra in the range of 486.365-605.895 nm in dichloromethane solvent. Among all derivatives, TTB5 was observed to be the promising candidate because of its lowest energy gap (2.54 eV) and binding energy (0.494 eV) values, along with the bathochromic shift (605.895 nm). These chromophores having an A-π-A framework might be considered promising materials for efficient organic cells.

Green Preparation of S, N Co-Doped Low-Dimensional C Nanoribbon/C Dot Composites and Their Optoelectronic Response Properties in the Visible and NIR Regions.

The green production of nanocomposites holds great potential for the development of new materials. Graphene is an important class of carbon-based materials. Despite its high carrier mobility, it has low light absorption and is a zero-bandgap material. In order to tune the bandgap and improve the light absorption, S, N co-doped low-dimensional C/C nanocomposites with polymer and graphene oxide nanoribbons (the graphene oxide nanoribbons were prepared by open zipping of carbon nanotubes in a previous study) were synthesized by one-pot carbonization through dimensional-interface and phase-interface tailoring of nanocomposites in this paper. The resulting C/C nanocomposites were coated on untreated A4 printing paper and the optoelectronic properties were investigated. The results showed that the S, N co-doped C/C nanoribbon/carbon dot hybrid exhibited enhanced photocurrent signals of the typical 650, 808, 980, and 1064 nm light sources and rapid interfacial charge transfer compared to the N-doped counterpart. These results can be attributed to the introduction of lone electron pairs of S, N elements, resulting in more transition energy and the defect passivation of carbon materials. In addition, the nanocomposite also exhibited some electrical switching response to the applied strain. The photophysical and doping mechanisms are discussed. This study provides a facile and green chemical approach to prepare hybrid materials with external stimuli response and multifunctionality. It provides some valuable information for the design of C/C functional nanocomposites through dimensional-interface and phase-interface tailoring and the interdisciplinary applications.

Exploring the Dynamics of Charge Transfer in Photocatalysis: Applications of Femtosecond Transient Absorption Spectroscopy.

Artificial photocatalytic energy conversion is a very interesting strategy to solve energy crises and environmental problems by directly collecting solar energy, but low photocatalytic conversion efficiency is a bottleneck that restricts the practical application of photocatalytic reactions. The key issue is that the photo-generated charge separation process spans a huge spatio-temporal scale from femtoseconds to seconds, and involves complex physical processes from microscopic atoms to macroscopic materials. Femtosecond transient absorption (fs-TA) spectroscopy is a powerful tool for studying electron transfer paths in photogenerated carrier dynamics of photocatalysts. By extracting the attenuation characteristics of the spectra, the quenching path and lifetimes of carriers can be simulated on femtosecond and picosecond time scales. This paper introduces the principle of transient absorption, typical dynamic processes and the application of femtosecond transient absorption spectroscopy in photocatalysis, and summarizes the bottlenecks faced by ultrafast spectroscopy in photocatalytic applications, as well as future research directions and solutions. This will provide inspiration for understanding the charge transfer mechanism of photocatalytic processes.

Sandwiched naphthyl carbazole: Inversion Circularly Polarized Luminescence based on a pull-push electron valve strategy.

Inspired by circularly polarized luminescence (CPL), artificial CPL assembly has attracted intense attention. However, precise manipulation of chiral transfer from achiral and luminescent materials remains a formidable challenge. Two sandwiched carbazole and binaphthol derivatives composed of pyridine or trifluoride methyl benzene have been synthesized. Among R-1 and R-2, their spectra were found in the violet region, both in the solution and the film state. They exhibit the photoluminescence dissymmetry factors up to 1.4 × 10-3 for R-2 and an opposite value of -5.6 × 10-4 for R-1. Theoretical CPL and circular dichroism (CD) studies were in good agreement with the experimental data and deciphered their opposite signals by the transition electric and magnetic moment. Our study offers a strategy for studying the charge and chiral transfer.

SF6 Negative Ion Formation in Charge Transfer Experiments.

In the present work, we report an update and extension of the previous ion-pair formation study of Hubers, M.M.; Los, J. Chem. Phys.1975, 10, 235-259, noting new fragment anions from time-of-flight mass spectrometry. The branching ratios obtained from the negative ions formed in K + SF6 collisions, in a wide energy range from 10.7 up to 213.1 eV in the centre-of-mass frame, show that the main anion is assigned to SF5- and contributing to more than 70% of the total ion yield, followed by the non-dissociated parent anion SF6- and F-. Other less intense anions amounting to <20% are assigned to SF3- and F2-, while a trace contribution at 32u is tentatively assigned to S- formation, although the rather complex intramolecular energy redistribution within the temporary negative ion is formed during the collision. An energy loss spectrum of potassium cation post-collision is recorded showing features that have been assigned with the help of theoretical calculations. Quantum chemical calculations for the lowest-lying unoccupied molecular orbitals in the presence of a potassium atom are performed to support the experimental findings. Apart from the role of the different resonances participating in the formation of different anions, the role of higher-lying electronic-excited states of Rydberg character are noted.

Theoretical Study of Metal-Ligand Interactions in Lead Complexes with Radiopharmaceutical Interest.

The 203Pb and 212Pb lead radioisotopes are attracting growing interest as they can aid in the development of personalized, targeted radionuclide treatment for advanced and currently untreatable cancers. In the present study, the bonding interactions of Pb2+ with twelve macrocyclic ligands, having an octa and nona coordination, were assessed using Density Functional Theory (DFT) calculations. The molecular structures in an aqueous solution were computed utilizing the polarized continuum model. The preference for the twisted square antiprismatic (TSAP) structure was confirmed for ten out of the eleven cyclen-based complexes. The characteristics of the bonding were assessed using a Natural Energy Decomposition Analysis (NEDA). The analysis revealed a strong electrostatic character of the bonding in the complexes, with minor variations in electrical terms. The charge transfer (CT) had a comparable energetic contribution only in the case of neutral ligands, while in general, it showed notable variations regarding the various donor groups. Our data confirmed the general superiority of the carboxylate O and aromatic N donors. The combination of the selected efficient pendant arms pointed out the superiority of the acetate pendant arms and the lack of significant cooperation between the different pendant arms in the probed ligands. Altogether, the combination led only to a marginal enhancement in the total CTs in the complexes.

Photoinduced Enantioselective Triplet Radical Reaction on Metal: Copper-Catalyzed Conjugate Addition of Acylsilanes to α,ß-Unsaturated Ketones and Aldehydes.

A photoinduced copper-catalyzed enantioselective conjugate addition of acylsilanes has been developed. The conjugate acylation of α,ß-unsaturated ketones and aldehydes was promoted by a copper(I)/chiral NHC catalyst under visible-light irradiation for synthesizing various 2-substituted 1,4-dicarbonyl compounds in enantioenriched forms. Mechanistic studies combining experiments and quantum chemical calculations indicated a reaction mechanism involving copper-to-acyl charge transfer (i.e., metal-to-ligand charge transfer (MLCT)) excitation of an alkene-bound acylcopper complex. The MLCT excitation is followed by an electronical and geometrical change to generate a ß-radical-C-enolate-Cu(II)-acyl complex with an acyl radical character, which undergoes facile C-C bond formation in the copper coordination sphere, affording the 1,4-conjugate addition product.

Regulation of organic solar cells performance through external electric field: From charge transfer mechanisms to photovoltaic properties.

In organic solar cells (OSCs), comprehending the charge transfer mechanism at D/A interfaces is crucial for photoinduced charge generation and enhancing power conversion efficiency (PCE). The charge transfer mechanism and photovoltaic performance of the parallel stacking interface configuration of the PTQ10 polymer donor and T2EH non-fullerene acceptor (NFA) are systematically studied at the microscopic scale. The analysis of the electron-hole distribution of the PTQ10/T2EH excited states revealed the presence of multiple charge excitation modes and charge transfer pathways. Using Marcus theory, we examine the charge separation rate (KCS) of PTQ10/T2EH under external electric field (Fext) modulation, and it is clarified that reorganization energy (λ) is the main factor that affects the KCS. Our results show that Fext has a positive impact on the photovoltaic properties of PTQ10/T2EH thin films, as evidenced by the modulation of the open circuit voltage (VOC), voltage loss (VLOSS) and fill factor (FF). Overall, this study provides valuable theoretical insights for Fext to accelerate the charge separation process and enhance photovoltaic efficiency.