Photoinduced Charge Transfer Research Articles

Revealing Light-Magnetism Coupling via Anomalous Hall Effect and Magneto-Photoresponse in Proximity-Coupled CrSBr/Graphene Heterostructures.

The interplay between light and magnetism sparks groundbreaking concepts for the next-generation versatile spintronic and nanoelectronic devices. However, direct measurements of light-magnetism coupling remain challenging due to the intrinsic difficulties in characterizing these properties simultaneously. Herein, via harnessing magnetic proximity and anomalous Hall effect (AHE), we report the effective modification of magnetism in the graphene/CrSBr heterostructure by an unpolarized 405 nm light. The emergence of magnetism in graphene is ascribed to the proximity effect, which arises from its coupling with the neighboring CrSBr. The photoinduced charge transfer doping into graphene exerts a precise tune over the Fermi level (EF), facilitating the optical control of carrier density and mobility. This operation engenders an adjustable anomalous Hall resistance and magnetoresistance congruent with the Fermi level tuning, further verified by surface potential measurements. In parallel, high-performance magneto-photoresponse has been realized, which is believed to result from spin polarization-enhanced photoinduced charge separation. Our study offers insights into the interplay between light and magnetism, showcasing the potential of 2D proximity-coupled heterostructures in opto-spintronics.

Trace Detection of Deltamethrin via Au/Cu2O/ZnO SERS Substrates with Multiple Heterojunctions.

Organic pesticide residues accumulate in the human body through dietary consumption, presenting a significant health risk. Therefore, efficient and sensitive detection of these residues is crucial. Surface-enhanced Raman scattering (SERS), as a powerful non-destructive detection technology, has attracted more attention due to its exceptional sensitivity and versatility. This study presents a novel Au/Cu2O/ZnO SERS substrate, synthesized through a multiple-cycle chemical adsorption plus reduction method, which exhibits exceptional sensitivity, stability, and repeatability. The substrate achieves a remarkable limit of detection (LOD) of 10-13 M for Rhodamine 6G (R6G), with an impressive enhancement factor of approximately 3.8 × 1010. Notably, the substrate's efficacy was further demonstrated in the successful detection of deltamethrin with a LOD of 0.01 mg/L. The effects of ZnO, Cu2O, and Au on the SERS performance of the substrate were clarified through a comprehensive analysis of the charge transfer mechanism. Experimental results demonstrate that the multiple heterojunctions within the ternary composite structure significantly facilitate the photo-induced charge transfer, thereby enhancing the SERS activity. This study demonstrates the potential of three-dimensional structures with multiple heterojunctions to significantly improve SERS performance and offers a novel strategy for designing noble metal/semiconductor SERS substrates characterized by dense hotspots and high charge transfer contributions.

Spectroscopic Kinetic Insights into the Critical Role of Metal-Oxide Interfaces in Enhancing the Concentration of Surface-Reaching Photoexcited Charges.

Surface modification of semiconductors with noble metals has been shown to effectively tune their photocatalytic activity. However, the photoinduced charge transfer processes at the metal/semiconductor interface and their impact on the concentration of surface-reaching photoexcited charges remain subjects of ongoing debate. In this study, we used time-resolved spectroscopy and kinetic analysis to investigate the behavior of surface-reaching photoholes in metal-loaded TiO2 nanoparticles. Our results reveal that the concentration of surface-reaching photoholes (Ch+(surf)) is highly dependent upon the type of metal and the resulting metal-oxide interface. Among the noble metals studied (Pt, Au, and Ag), Pt loading led to the most significant increase in Ch+(surf), with a nearly 3-fold enhancement compared to pristine TiO2. This enhancement was attributed to the generation of more abundant Ti3+ defects at the metal-oxide interface, which serve as hole trap states, thereby accelerating interfacial charge transfer, improving charge separation, and enriching Ch+(surf). These findings underscore the critical role of the metal-oxide interface in enhancing surface-reaching photoexcited charges, offering valuable insights for the design of advanced materials for solar energy conversion.

Photo-induced multiple charge transfer resonance of Ce-MOF for SERS detection of nucleic acid.

Sensitive and accurate detection of important cancer markers MicroRNAs (miRNAs) is critical to prevent and treat disease. Among many detection techniques, surface-enhanced Raman scattering(SERS) has attracted much attention due to its advantages such as narrow spectral peak, low interference and non-destructive detection. Interestingly, non-noble metal SERS substrates show good prospects due to their outstanding spectral reproducibility and biocompatibility. However, the low SERS sensitivity of non-noble metal substrates also limited their detection performance. Therefore, it is crucial to design a non-noble metal substrate with high SERS sensitivity for nucleic acid detection. In this study, we found that the photo induction (30min) of Ce-MOF has high SERS performance (abbreviated as Ce-MOF30). It is due to that photo-induction can regulate the energy level of the Ce-MOF and break the benzene-C bonds to introduce a defect energy level, which provides additional charge transfer channels. The Ce-MOF30 substrates can achieve an enhancement factor (EF) of 6.71×106 for Methylene blue (MB), about 7-fold higher than pristine Ce-MOF, which is the best Ce-based SERS substrate so far. Finally, a SERS detection platform was fabricated by combining the Mg2+ assisted dual signal amplification for miRNA 141 assay, and the detection limit was 1.72fM. This work proposed a simple photo-induction strategy to enhance SERS performance, which supplied a new detection platform for detection of nucleic acid and further expand the application of non-noble metal substrate in SERS field.

Photo-enhanced UiO-66/Au Nanoparticles with High Phosphatase-Like Activity for Rapid Degradation and Detection of Paraoxon.

The severe environmental and human health hazards posed by organophosphorus compounds underscore the pressing need for advancements in their degradation and detection. However, practical implementation is impeded by prolonged degradation durations and limited efficiency. Herein, an effective interfacial modification approach is proposed involving the integration of photoactive Au nanoparticles (NPs) onto metal-organic frameworks, resulting in the synthesis of UiO-66/Au NPs exhibiting enhanced hydrolysis activity under light excitation. Under illumination, UiO-66/Au NPs trigger rapid hydrolysis of ethyl-paraoxon within a mere 10-min timeframe, yielding a discernible colorimetric response indicative of extensive hydrolysis. Mechanistic analyses reveal that Au NPs elevate the local catalytic microenvironment temperature of UiO-66/Au NPs under light exposure, facilitating photo-induced charge transfer that enhances the affinity between the Zr6 clusters within UiO-66/Au NPs and the hydrolytic substrate. These cooperative mechanisms significantly boost the hydrolytic efficiency of UiO-66/Au NPs, resulting in a remarkable 17.8-fold enhancement in catalytic performance. Leveraging the superior photo-enhanced hydrolytic capabilities of UiO-66/Au NPs, a colorimetric sensor is developed for the rapid degradation and detection of ethyl-paraoxon, offering a practical and effective solution for addressing the degradation and detection challenges associated with organophosphorus compounds.

The Role of Open-Shell Organic Radical in Enhancing Anti-Tumor Photocatalysis Reaction of NIR Light-Activated Photosensitizer.

Open-shell radical materials, which are characterized by unpaired electrons, have led to revolutionary breakthroughs in material science due to their unique optoelectronic properties. However, the involvement of organic radicals in photodynamic therapy (PDT) has rarely been reported or discussed. This work studies two photosensitizer analogs. 4AM-OS with extended π-conjugation exhibits open-shell radical characters and enhanced type-I photodynamic activity compared with closed-shell 2AM-CS. 4AM-OS displays the thermally accessible triplet-state character, resulting in more unpaired electrons delocalized along the π-conjugated backbone at higher temperatures. Accordingly, the temperature-dependent photodynamic activity of 4AM-OS confirms its association with the open-shell electronic structure. As the unpaired electrons in open-shell 4AM-OS are more delocalized and generate additional electronic energy states, photo-induced charge transfer is promoted to facilitate type-I photodynamic reactions. This observation addresses the challenge associated with near-infrared (NIR) photosensitizers, such as 4AM-OS, which often demonstrate low efficacy in PDT due to the limited energy provided by NIR light despite its superior tissue penetration depth. Overall, clarifying the beneficial role of organic radicals in photodynamic reactions will bring revolutionary breakthroughs to developing high-performance NIR photosensitizers and promoting the efficacy of PDT for deep-seated lesions.

Photoinduced Long-Distance Charge Transfer in Silicanes: The Stacking Matters.

The generation of interlayer charge transfer excitons upon photoexcitation is strongly desirable for two-dimensional (2D) materials stacked through van der Waals interactions. In this work, we investigate photoinduced charge transfer in silicanes (SiH) with three typical stackings. A concept of the regional natural hole orbital and its conjugated particle orbital is developed to characterize excited states in solids. This method delivers bonding information about excited states and explains the formation of certain types of states in nanomaterials. Utilizing this tool, we demonstrate that SiH in the 1H and 6R stackings exhibits an interlayer charge transfer distance that reaches ∼10 Å under violet and near-ultraviolet radiation. The charge transfer is attributed to the interlayer overlap between orbitals at the conduction band minimum, which is disfavored by the 3R stacking. Our findings suggest a new and feasible approach for tuning the optoelectronic properties of Group 14 2D materials by altering their stackings.

Fabrication of core-shell Prussian blue analogue@ZnIn2S4 nanocubes for efficient photocatalytic hydrogen evolution coupled with biomass furfuryl alcohol oxidation.

Utilizing photocatalytic technology for the value-added conversion of biomass derivatives, alongside the production of clean hydrogen energy, represents a viable approach to addressing energy and environmental challenges. However, the design of cost-effective and efficient photocatalysts remains a significant obstacle. In this work, we employed open-framework Prussian blue analogs as co-catalytic centers and combined them with ZnIn2S4 to construct a series of core-shell nanocube photocatalysts with varying metal compositions. This unique structure provides abundant photocatalytic redox-active sites and effectively facilitates the separation and transfer of photoinduced charges. By examining the oxidation of furfuryl alcohol (FOL) to furfural (FAL) with cooperative H2 evolution, the optimal Ni-Co PBA@ZnIn2S4 sample exhibited remarkable catalytic activity, achieving H2 and FAL yields of 739.3 and 705.2 μmol g-1 h-1, respectively, which is approximately four times greater than that achieved with bare ZnIn2S4. This study offers valuable insights into the design of photocatalysts and the selection of co-catalytic metal centers.

Push-pull effect - how to effectively control photoinduced intramolecular charge transfer processes in rhenium(I) chromophores with ligands of D-A or D-π-A structure.

Over the last five decades, diimine rhenium(I) tricarbonyl complexes have been extensively investigated due to their remarkable and widely tuned photophysical properties. These systems are regarded as attractive targets for design functional luminescent materials and performing fundamental studies of photoinduced processes in transition metal complexes. This review summarizes the latest developments concerning Re(I) tricarbonyl complexes bearing donor-acceptor (D-A) and donor-π-acceptor (D-π-A) ligands. Such compounds can be treated as bichromophoric systems with two close-lying excited states, metal-to-ligand charge transfer (MLCT) and intraligand-charge-transfer (ILCT). A role of ILCT transitions in controlling photobehaviour was discussed for Re(I) tricarbonyls with six different diimine cores decorated by various electron-rich amine, sulphur-based and π-conjugated aryl groups. It was evidenced that this approach is an effective tool for enhancement of the visible absorptivity, bathochromic emission shift and significant prolongation of the excited-state, opening up new possibilities in the development of more efficient materials and expand the range of their applications.

Interfacial imine-bridging and charge directional migration dual regulation of ZnO/covalent organic frameworks S-scheme heterostructure for boosting photocatalytic CO2 reduction.

Covalent organic frameworks (COFs) equipped with controllable porosity and excellent structural stability are regarded as promising candidates for photocatalytic CO2 reduction, yet some inherent drawbacks including low CO2 activation and sluggish charge carriers' transfer properties urgently need to be addressed. Herein, we developed an imine-bridged strategy to construct ZnO/COF heterostructure by integrating donor-acceptor COF (TAPT-DMTP COF) on the surface of amino-modified ZnO for photocatalytic CO2 reduction. The optimal photocatalyst, NZnO/TAPT-DMTP COF-3, exhibited superior photocatalytic activity for reducing CO2 to CO and CH4, which was significantly higher than pristine COF and non-covalently bridged ZnO/TAPT-DMTP COF. Experimental and photo-electrochemical results reveal that the microstructure of TAPT-DMTP COF, interfacial imine-bridging and S-scheme heterojunction play a crucial role in promoting photoinduced charge transfer and separation, thus improving photocatalytic efficiency. Moreover, in-situ characterization and theoretical calculations indicate the photoinduced electrons transfer from NZnO to TAPT-DMTP COF upon hybridization, and this S-scheme heterostructure dramatically lowers the energy barrier of rate-determining step from *COOH to *CO. This work provides insight into the covalent-linked COF-based S-scheme photocatalyst and highlights its vital role in enhancing CO2 reduction.

Photoinduced charge transfer renormalization in NiO

Photoinduced charge transfer renormalization in NiO

Factors Affecting the Population of Excited Charge Transfer States in Adenine/Guanine Dinucleotides: A Joint Computational and Transient Absorption Study.

There is compelling evidence that the absorption of low-energy UV radiation directly by DNA in solution generates guanine radicals with quantum yields that are strongly dependent on the secondary structure. Key players in this unexpected phenomenon are the photo-induced charge transfer (CT) states, in which an electric charge has been transferred from one nucleobase to another. The present work examines the factors affecting the population of these states during electronic relaxation. It focuses on two dinucleotides with opposite orientation: 5'-dApdG-3' (AG) and 5'-dGpdA-3' (GA). Quantum chemistry calculations determine their ground state geometry and the associated Franck-Condon states, map their relaxation pathways leading to excited state minima, and compute their absorption spectra. It has been shown that the most stable conformer is anti-syn for AG and anti-anti for GA. The ground state geometry governs both the excited states populated upon UV photon absorption and the type of excited state minima reached during their relaxation. Their fingerprints are detected in the transient absorption spectra recorded with excitation at 266 nm and a time resolution of 30 fs. Our measurements reveal that in the large majority of dinucleotides, chromophore coupling is already operative in the ground state and that the charge transfer process occurs within ~120 fs. The competition among various relaxation pathways affects the quantum yields of the CT state formation in each dinucleotide, which are estimated to be 0.18 and 0.32 for AG and GA, respectively.

Superior degradation of tetracycline hydrochloride, rhodamine B, and methyl orange by platinum-modified Bi4Ti3O12/Ti3C2Tx photocatalyst: Synthesis, Catalytic performance, and Mechanism

Photocatalytic degradation of organic compounds and antibiotics in water by solar energy represents a promising approach for addressing environmental problems. The precious metal particles of platinum were connected through a facile ultraviolet light deposition technique based on Bi4Ti3O12 that was in situ hybridized with Ti3C2Tx. The potential development process was elucidated by investigating the breakdown of TC-HCl. The prepared Pt/Bi4Ti3O12/Ti3C2Tx material achieved complete removal of pollutants under light conditions, including tetracycline hydrochloride (10min), rhodamine B (30min), and methyl orange (10min), which benefited from the mutual enhancement between Ti3C2Tx and Bi4Ti3O12. Additionally, the increased specific surface area of Pt/Bi4Ti3O12/Ti3C2Tx may provide additional pathways for electron insertion/extraction. The platinum (Pt) rapidly absorbs photogenerated electrons, which facilitates photoinduced charge transfer and effectively suppresses carrier recombination. These collective effects significantly enhance catalytic activity and reduce photo-corrosion. This study paves the way for the development of photocatalytic materials based on Bi4Ti3O12/Ti3C2Tx, incorporating metal loads to enhance sunlight absorption capacity and antibiotic degradation capability.

Revealing Photoinduced Charge Transfer Mechanism of SnO2/BiOBr S-Scheme Heterostructure for CO2 Photoreduction

Revealing Photoinduced Charge Transfer Mechanism of SnO2/BiOBr S-Scheme Heterostructure for CO2 Photoreduction

Dual-Enhanced Nanohybrids for Synergistic Photothermal and Photodynamic Therapy in Cancer Treatment with Immune Checkpoint Inhibitors.

This study presents a nanohybrid that simultaneously improves both photothermal (PT) and photodynamic (PD) effects for cancer therapy. The conjugated polymer nanoparticle (CPN) comprises of p-type conjugated polymer as a photosensitizer, charge donor, and PT agent, n-type conjugated polymer as a charge acceptor and PD agent, and Au nanoparticles (NPs) as a PT agent. This nanohybrid is assembled through a film dispersion process using a hydrophobically modified phospholipid, producing a high yield of uniform hybrid NPs in a short timeframe, and displays exceptional photothermal and photodynamic effects, when activated at a single near-infrared wavelength. Photophysical analysis indicates that the inclusion of AuNPsenhances nonradiative exciton relaxation, while the incorporation of a n-type conjugated polymer boosts photoinduced charge transfer and potentially contributes to the charge-recombination mediated triplet-state formation for an enhanced generation of reactive oxygen species. During phototherapy, the nanohybrid demonstrates the most effective suppression of primary tumor growth and significantly boosts anti-tumor immune responses owing to its simultaneous photothermal and photodynamic effects. Furthermore, when combined with immune checkpoint inhibitors, nanohybrid treatment minimizes tumor sizes while maximizing survival rates in mice. Thus, the nanohybrid represents a promising nanoplatform for combination phototherapy in cancer treatment.

Observation of Excited State-Derived Photoluminescence Decay of Organic Dye to Monitor Its Photo-Induced Charge Transfer Efficiency

Understanding photo-induced charge transfer (PCT) is crucial for optimizing the performance of solar-powered devices like photovoltaic and photoelectrochemical cells, as PCT directly impacts their operation and overall power conversion efficiency. General assessment of PCT has heavily relied on transient absorption techniques to gauge electron transfer between the donor and acceptor. However, there is a pressing need to broaden the methods for comprehensively studying PCT.In this study, we propose an alternative approach utilizing transient photoluminescence to observe PCT dynamics between organic dyes and redox mediators. This approach involves adsorbing various organic dyes onto Al2O3 surfaces along with redox mediators. When excited, the dyes facilitate charge separation from each other, leading to the instantaneous oxidized form of the dye and subsequent electron transfer from the redox mediator. This process results in a decrease in the photoluminescence lifetime of the organic dye. The extent of this decreases correlates with the Gibbs free energy of charge transfer, reflecting the efficiency of electron transfer between the organic dye and the redox mediator. Our findings introduce an alternative avenue for studying PCT, offering insights that are pertinent to various fields including photovoltaics, optoelectronics, and photocatalysis. Figure 1

(Invited) Shooting Electron Bullets through Catalyst Pores

Intermolecular spaces between molecules support nonviolence correlation-bound anion states, or more colloquially superstorm states. Such states can act as electron waveguides for photoinduced donor-acceptor charge transfer, as we demonstrate by ultrafast coherent photoelectron spectroscopy. We explore the possibility of photoinduced coherent charge transfer through such waveguides and anticipate their potential role in photocatalytic chemistry.

Solar-Driven Polyvinyl Alcohol Remediation: Black Phosphorus Quantum Dot Sensitized g-C3N4 Photocatalyst Vs. H2 Evolution in Photocatalytic Fuel Cells

In response to polyvinyl alcohol (PVA) waste pollution, we developed a composite photocatalyst by sensitizing g-C3N4 with black phosphorus quantum dots (BPQDs) using a simple mechanical stirring technique. Both g-C3N4 and BPQDs are inorganic semiconductors, enabling efficient photoinduced charge transfer. Leveraging the adjacency of C, N, and P elements in the periodic table facilitated the formation of P-N or P-C bonds, resulting in uniform BPQD decoration on two-dimensional layered g-C3N4, with an average size of 2.2 nm. Under solar light simulator irradiation for 20 minutes, the composite photocatalyst exhibited significantly enhanced photocatalytic activity, increasing PVA degradation efficiency from 27.1% (pure g-C3N4) to 85.9%. Experimental observations and theoretical calculations suggest the establishment of a Z-scheme route at the g-C3N4/BPQDs interface, facilitating photoinduced electron transfer from g-C3N4 to BPQDs, leading to augmented carrier generation and separation, reduced charge-transfer resistance, and accelerated PVA degradation. The proposed composite photocatalyst holds promise in addressing PVA pollution and promoting environmental sustainability.Additionally, in a dual-chamber photocatalytic fuel cell setup, simultaneous degradation of PVA and hydrogen evolution were achieved, employing commercial P25 as the photoanode and Ag@Fe2O3 nanoparticles as the cathode. Moreover, the feasibility of a Fenton-like reaction at the cathode, utilizing Fe2+ ions and pumped O2, was demonstrated. The effects of different cathode materials, PVA types, and pH values on device performance were assessed, with quenching tests highlighting the pivotal roles of h+ and OH· radicals in PVA degradation. The device's long-term stability was established through cycling experiments.

Construction of S-scheme heterojunction via coating ZIF-8-derived Zn0.7Cd0.3S on Ni2P hydrangea for efficient photocatalytic hydrogen evolution coupled with benzyl alcohol oxidation

Coupling light-driven hydrogen (H2) evolution with benzyl alcohol (BA) oxidation is regard as a prospective strategy for obtaining value-added fuels as well as chemicals to deal with energy and environment crisis. In this contribution, a series of dual-functional noble metal-free S-scheme heterojunctions (Zn1-xCdxS@yNi2P) with spatially separated and precise redox sites were constructed by synthesizing Zn1-xCdxS with regular morphology uniformly coated on Ni2P nanosheets via the template method for coupling H2 evolution with BA oxidation. The optimized Zn0.7Cd0.3S@15 %Ni2P photocatalytic produced H2 (40.33 mmol g−1 h−1) and benzaldehyde (BAD) (43.38 mmol g−1 h−1), remarkably exceeding pure Ni2P and Zn0.7Cd0.3S. Notably, the Zn0.7Cd0.3S@15 %Ni2P gave a significant advantage in coupling H2 evolution and BA oxidation performance than the catalysts reported previously. The S-scheme heterojunction constructed between Zn0.7Cd0.3S and Ni2P was demonstrated by Density functional theory (DFT) calculations, in-situ radiation X-ray photoelectron spectroscopy (XPS), Kelvin probe force microscope (KPFM) and electron paramagnetic resonance (EPR). The effect of S-scheme heterointerfaces and internal electric field promoted photo-induced charge separation and transfer efficiency, greatly enhancing the photocatalysis performance. This work emphasizes the significance of rational engineering of heterojunctions, providing an enlightening guidance on synthesis of dual-functional photo-redox catalysts to improve economical solar fuel exploitation and production of value-added chemicals.

Theoretical analysis of photosensitization of DNA by thionine.

In this work, we are the first to perform a theoretical analysis of photoinduced charge transfer in the intercalation complex of thionine (TH) with double-stranded DNA, which was observed in experiments. Efficient DNA binding and long-wave absorption maximum make TH an attractive photosensitizer. d(CpG)2 tetranucleotide was used as a minimal model DNA fragment. Intercalation of TH between pairs of nucleobases causes the transfer of a small negative charge (0.24 e) from the tetranucleotide to the dye. S0 → S1 photoexcitation of their complex using visible light leads to the transfer in the same direction of a significant negative charge (0.9 e). This electronic transition has a HOMO → LUMO electronic configuration, with HOMO localized on one of the two phosphate groups of the tetranucleotide, and LUMO on TH; the latter has the same shape as the LUMO of free dye. In the complex, TH, by its amino groups, forms two intermolecular H-bonds: with the deoxyribose oxygen atom of one d(CpG)2 strand and with the non-bridging oxygen atom of the phosphate group of the other strand. In this case, the H-bond TH with the phosphate group is stronger than with the sugar, but the charge transfer is carried out from another phosphate group through the sugar to the dye. Thus, charge transfer occurs along the longer of the two paths. However, the path of charge transfer depends on the parameters of the excitation since higher electronic transitions also include the second phosphate group, i.e., a short way is also used. For the calculations of the excitation of the complex, TD-DFT was used in combination with a set of ten functionals (CAM-B3LYP + D3BJ, ωB97XD, LC-ωHPBE, M052X, M062X, M06HF, M08HX, M11, MN15, and SOGGA11X), which have proven themselves well in modeling the excitation of dimers of aromatic molecules. Of these, LC-ωHPBE, which gave the best agreement with the experiment, was selected for the final calculations. It was used in combination with the 6-31 + + G(d,p) basis set and the IEFPCM solvent model. The photoinduced charge redistribution was quantitatively estimated using natural population analysis, and visually by building the frontier molecular and natural transition orbitals.