Light Energy Conversion Research Articles

Living Therapeutics for Synergistic Hydrogen-Photothermal Cancer Treatment by Photosynthetic Bacteria.

Hydrogen gas (H2) therapy, recognized for its inherent biosafety, holds significant promise as an anti-cancer strategy. However, the efficacy of H2 treatment modalities is compromised by their reliance on systemic gas administration or chemical reactions generation, which suffers from low efficiency, poor targeting, and suboptimal utilization. In this study, living therapeutics are employed using photosynthetic bacteria Rhodobacter sphaeroides for in situ H2 production combined with near-infrared (NIR) mediated photothermal therapy. Living R. sphaeroides exhibits strong absorption in the NIR spectrum, effectively converting light energy into thermal energy while concurrently generating H2. This dual functionality facilitates the targeted induction of tumor cell death and substantially reduces collateral damage to adjacent normal tissues. The findings reveal that integrating hydrogen therapy with photothermal effects, mediated through photosynthetic bacteria, provides a robust, dual-modality approach that enhances the overall efficacy of tumor treatments. This living therapeutic strategy not only leverages the therapeutic potential of both hydrogen and photothermal therapeutic modalities but also protects healthy tissues, marking a significant advancement in cancer therapy techniques.

A novel bi-level optimal strategy-assisted design boosting discovery of specific surface area of perovskite oxide for effective photocatalysis

Due to the inherent property of materials, photocatalysis plays a crucial role in diverse applications, such as the degradation of organic pollutants, fuel production, and nitrogen fixation. Perovskites, in particular, are remarkable for their high light absorption rate and energy conversion efficiency within the visible light range, thereby positioning them as promising photocatalysts. Given that specific surface area (SSA) is a critical metric for evaluating photocatalytic performance, accurately and quickly predicting the SSA of perovskites has emerged as a key area of technical research. Therefore, it is essential to explore the relationship between potential materials descriptors and SSA, which can significantly expedite the discovery of photocatalyzed perovskite materials with high SSA. In this study, we proposed a bi-level optimization method that combines descriptors identified strategy and model optimization strategy for predicting the SSA of unknown perovskite candidates, thereby elucidating the relationship between material features and SSA. Initially, at the upper level, the Gradient Boosting Regression combined with Recursive Feature Elimination (RFE-GBR) method was employed to identify crucial features that are closely correlated with the SSA of photocatalyzed perovskites. Subsequently, the Sure Independence Screening.Sparsifying Operator (SISSO) was utilized to develop new descriptors that exhibited strong correlations with SSA. Based on refined descriptors identifiied at the upper level, at the lower level, the optimal model strategy was obtained by Improved Osprey Optimization Algorithm (IOOA) using golden sine strategy and Gradient Boosting Regression (GBR) regression to tune the key parameters of GBR for optimizing SSA. The optimal designing method achieved remarkable predictive performance with R2 (R-squared) score of 0.90 and MAE (Mean Absolute Error) of 3.97 m2/g, along with 5-fold cross-validation. Then this method was applied to predict the SSA of 300 unidentified ABO3 perovskites. Comparison with experimental data revealed that our approach significantly accelerated the development of perovskite materials with superior photocatalytic properties, showing the potential of our model in advancing the field of photocatalysis.

Fabrication of solid-state plasmonic solar cell device using FTO|TiO2|Ag-nanoparticle assembly to generate hot electrons surpassing Schottky barrier

This work presents a detailed investigation into the fabrication and performance evaluation of plasmonic solar cells, where a thin film of silver nanoparticles is deposited onto a TiO₂ layer, with the silver film itself functioning as the active layer for light absorption and energy conversion. The study compares two deposition techniques—DC Magnetron Sputtering and Thermal Vapor Deposition (TVD)—revealing significant differences in the resulting device performance. The device fabricated using TVD demonstrated a significantly higher open circuit voltage of 440.3 mV and short circuit current density of 1.6 mA/cm² compared to the device fabricated via DC Magnetron Sputtering, which recorded an open circuit voltage of 56.92 mV and a short circuit current density of 0.03 mA/cm². These results indicate that TVD offers superior electron-hole separation, reduced recombination losses, and enhanced light absorption efficiency. The main contribution of this work lies in demonstrating that the TVD technique significantly improves the photovoltaic performance of plasmonic solar cells compared to DC Magnetron Sputtering. The study validates the hot-electron mechanism at the TiO2|Ag junction using Kelvin probe force microscopy, contributing valuable insights into the role of plasmonic effects in enhancing solar cell efficiency. Additionally, it underscores the potential of TVD for developing advanced solar cell technologies with higher energy conversion efficiency.

Long-Term Autotrophic Growth and Solar-to-Chemical Conversion in Shewanella Oneidensis MR-1 through Light-Driven Electron Transfer.

Members of the genus Shewanella are known for their versatile electron accepting routes, which allow them to couple decomposition of organic matter to reduction of various terminal electron acceptors for heterotrophic growth in diverse environments. Here, we report autotrophic growth of Shewanella oneidensis MR-1 with photoelectrons provided by illuminated biogenic CdS nanoparticles. This hybrid system enables photosynthetic oscillatory acetate production from CO2 for over five months, far exceeding other inorganic-biological hybrid system that can only sustain for hours or days. Biochemical, electrochemical and transcriptomic analyses reveal that the efficient electron uptake of S. oneidensis MR-1 from illuminated CdS nanoparticles supplies sufficient energy to stimulate the previously overlooked reductive glycine pathway for CO2 fixation. The continuous solar-to-chemical conversion is achieved by photon induced electric recycling in sulfur species. Overall, our findings demonstrate that this mineral-assisted photosynthesis, as a widely existing and unique model of light energy conversion, could support the sustained photoautotrophic growth of non-photosynthetic microorganisms in nutrient-lean environments and mediate the reversal of coupled carbon and sulfur cycling, consequently resulting in previously unknown environmental effects. In addition, the hybrid system provides a sustainable and flexible platform to develop a variety of solar products for carbon neutrality.

Long‐Term Autotrophic Growth and Solar‐to‐Chemical Conversion in Shewanella Oneidensis MR‐1 through Light‐Driven Electron Transfer

AbstractMembers of the genus Shewanella are known for their versatile electron accepting routes, which allow them to couple decomposition of organic matter to reduction of various terminal electron acceptors for heterotrophic growth in diverse environments. Here, we report autotrophic growth of Shewanella oneidensis MR‐1 with photoelectrons provided by illuminated biogenic CdS nanoparticles. This hybrid system enables photosynthetic oscillatory acetate production from CO2 for over five months, far exceeding other inorganic‐biological hybrid system that can only sustain for hours or days. Biochemical, electrochemical and transcriptomic analyses reveal that the efficient electron uptake of S. oneidensis MR‐1 from illuminated CdS nanoparticles supplies sufficient energy to stimulate the previously overlooked reductive glycine pathway for CO2 fixation. The continuous solar‐to‐chemical conversion is achieved by photon induced electric recycling in sulfur species. Overall, our findings demonstrate that this mineral‐assisted photosynthesis, as a widely existing and unique model of light energy conversion, could support the sustained photoautotrophic growth of non‐photosynthetic microorganisms in nutrient‐lean environments and mediate the reversal of coupled carbon and sulfur cycling, consequently resulting in previously unknown environmental effects. In addition, the hybrid system provides a sustainable and flexible platform to develop a variety of solar products for carbon neutrality.

Widespread adaptive evolution in angiosperm photosystems provides insight into the evolution of photosystem II repair.

Oxygenic photosynthesis generates the initial energy source that fuels nearly all life on Earth. At the heart of the process are the photosystems, which are pigment binding multi-protein complexes that catalyse the first step of photochemical conversion of light energy into chemical energy. Here, we investigate the molecular evolution of the plastid-encoded photosystem subunits at single-residue resolution across 773 angiosperm species. We show that despite an extremely high level of conservation, 7% of residues in the photosystems, spanning all photosystem subunits, exhibit hallmarks of adaptive evolution. Through in silico modelling of these adaptive substitutions, we uncover the impact of these changes on the predicted properties of the photosystems, focussing on their effects on co-factor binding and inter-subunit interface formation. By analyzing these cohorts of changes, we reveal that evolution has repeatedly altered the interaction between photosystem II and its D1 subunit in a manner that is predicted to reduce the energetic barrier for D1 turnover and photosystem repair. Together, these results provide insight into the trajectory of photosystem adaptation during angiosperm evolution.

Photomechanical Crystals as Light-Activated Organic Soft Microrobots.

In the field of materials science, dynamic molecular crystals have attracted significant attention as a novel class of energy-transducing materials. However, their development into becoming fully functional actuators remains somewhat limited. This study focuses on one family of dynamic crystalline materials and delves into exploring the efficiency of conversion of light energy to mechanical work. A simple setup is designed to determine a set of performance indices of anthracene-based crystals as an exemplary class of dynamic molecular crystals. The ability of these crystals to reversibly bend due to dimerization is realistically assessed from the perspective of the envisaged soft robotics applications, where wireless photomechanical grippers manipulate and assemble microscopic objects driven and controlled by light instead of lines and motors. The approach described here not only guides the quantification of responsive molecular crystals' actuation potential but also aims to attract an interdisciplinary interest to further develop this class of materials into controllable all-organic actuating elements to be used in microrobotics for engineering or biomedicine.

Performance of yellow and pink oyster mushroom dyes in dye sensitized solar cell

A solar photovoltaic (PV) cell, is an electrical device that uses the PV effect to convert light energy into electricity. The application of oyster mushroom dyes in dye sensitized solar cell (DSSC) is a novel strategy to substitute the costly chemical production process with easily extractable, environmentally acceptable dyes. Both dyes of yellow and pink oyster mushrooms were extracted using the same process but dried into powder form using two techniques, warm drying and freeze drying. The characterization was carried out utilizing current-voltage (I-V) characterization for electrical properties, Ultraviolet-Visible (UV-Vis) spectrophotometer for optical properties, Field Emission Scanning Electron Microscopy (FESEM), and Atomic Force Microscopy (AFM) for the structural properties. It was found that freeze-dried pink and yellow oyster mushroom had shown the good properties for DSSC application as it produced energy bandgap which lies within the range of efficient dye sensitizer; 1.7 eV and 2.2 eV, the most uniform distribution of pores and a nearly spherical form in FESEM analysis, and AFM result obtained with the highest root mean square (RMS) roughness value (26.922 and 34.033) with stereoscopic morphologies. The data proved that mushroom dyes can be incorporated in DSSC with the optimization of drying method in the extraction process, dilution of dye and the layer of deposition on the glass substrate. The current density-voltage (J–V) characteristics of fabricated DSSC was characterized using Newport Oriel Sol3A solar simulator under AM 1.5 Sun condition (100 mW/cm2, 25 oC). From the result obtained by solar simulator, the fabricated FTO/TiO2/Pleurotus djamor dye/Pt indicated the Voc of 0.499 V and Jsc of 0.397 mA/cm2.

Enhancing the hole utilization efficiency of Ti–Fe2O3 photoelectrode by decorating CoCu-ZIF for efficient photo-assisted rechargeable zinc air batteries

To enhance the oxygen evolution reaction (OER) performance of the zinc-air battery (ZAB), reduce charging voltage, and improve energy utilization efficiency, a sunlight-assisted strategy has been implemented. The photo-assisted rechargeable ZAB was proposed, featuring Ti–Fe2O3 decorated with Co0·8Cu0.2-ZIF as the air electrode. Upon illumination, valence band holes were generated in Ti–Fe2O3, oxidizing Co2+ in Co0·.8Cu0.2-ZIF to Co3+/Co4+, enhancing OER performance, reducing the charging voltage from 2 V to 1.3 V and effectively narrowing the charging-discharging voltage gap from approximately 1.15 V–0.45 V. The Ti–Fe2O3/Co0·8Cu0.2-ZIF structure maintains a round-trip efficiency of 65.3% after 300 cycles. This result demonstrates the successful integration of photoelectrochemical principles with ZAB technology, showcasing its efficacy in solar energy storage and light energy conversion.

Transcriptomic profiling reveals the complex interaction between a bipartite begomovirus and a cucurbitaceous host plant

BackgroundBegomoviruses are major constraint in the production of many crops. Upon infection, begomoviruses may substantially modulate plant biological processes. While how monopartite begomoviruses interact with their plant hosts has been investigated extensively, bipartite begomoviruses-plant interactions are understudied. Moreover, as one of the major groups of hosts, cucurbitaceous plants have been seldom examined in the interaction with begomoviruses.ResultsWe profiled the zucchini transcriptomic changes induced by a bipartite begomovirus squash leaf curl China virus (SLCCNV). We identified 2275 differentially-expressed genes (DEGs), of which 1310 were upregulated and 965 were downregulated. KEGG enrichment analysis of the DEGs revealed that many pathways related to primary and secondary metabolisms were enriched. qRT-PCR verified the transcriptional changes of twelve selected DEGs induced by SLCCNV infection. Close examination revealed that the expression levels of all the DEGs of the pathway Photosynthesis were downregulated upon SLCCNV infection. Most DEGs in the pathway Plant-pathogen interaction were upregulated, including some positive regulators of plant defenses. Moreover, the majority of DEGs in the MAPK signaling pathway-plant were upregulated.ConclusionOur findings indicates that SLCCNV actively interact with its cucurbitaceous plant host by suppressing the conversion of light energy to chemical energy and inducing immune responses. Our study not only provides new insights into the interactions between begomoviruses and host plants, but also adds to our knowledge on virus-plant interactions in general.

Effects of different particle size microplastics and di-n-butyl phthalate on photosynthesis and quality of spinach

As agricultural technology advances, microplastics (MP), which result from the degradation of widely used plastic products, have gradually accumulated in the soil, raising serious environmental concerns. This study explores the toxic effects of di-n-butyl phthalate (DnBP) on spinach, focusing on various particle sizes and MP concentrations through hydroponic experiments. Experimental results demonstrated that MP/DnBP combined pollution significantly reduced key photosynthetic parameters, including net photosynthetic rate, stomatal conductance, and transpiration rate, compared to treatments with DnBP or MP alone. Additionally, there was an increase in intercellular carbon dioxide concentration, suggesting that the inhibition of photosynthesis was due to non-stomatal factors. Moreover, spinach exposed to combined pollution conditions exhibited a notable decrease in maximum light energy conversion efficiency, electron transfer efficiency, and chlorophyll content. This disruption affected the synthesis of ribulose-1,5-bisphosphate carboxylase. On the other hand, the contents of ascorbic acid and glutathione in spinach roots and leaves increased, indicating the plant’s defense mechanisms were activated in response the toxic effects of MP and DnBP. Despite this, there was a significant reduction in soluble protein and soluble sugar content and a marked increase in nitrite content, reflecting a decline in spinach quality. This decline was attributed to the exacerbation of DnBP’s toxic effects by MP. Overall, MP/DnBP combined pollution reduced the quality of spinach by impairing photosynthesis and sugar metabolism, potentially amplifying ecological risks to crop plants. This study provides insight into the synergistic effects of MP and DnBP on plant health.

Photothermal-driven soft actuator capable of alternative control based on coupled-plasmonic effect

Recent advancements in small-scale soft actuators have showcased their ability to respond to various stimuli, making them ideal for biomedical engineering and robotics. Light-responsive actuators constructed from photothermal materials such as carbon-based materials have received great attention for their remote wireless control ability. However, conventional carbon-based actuators typically exhibit uniform responses to different light wavelengths, limiting the complexity of their control. To address this limitation, this study develops light-driven soft actuators utilizing gold nanorods (Au NRs) to enhance selective photo-responsiveness. Au NRs are incorporated given their superior ability to convert light energy into localized heat through localized surface plasmon resonances, with efficiency varying based on their size and the wavelength of incident light. By adjusting the specifications of the Au NRs and the wavelength of the optical field, tunable actuation efficiency can be achieved. Experimental calibration confirms that the actuator exhibits differential performance across various wavelengths, enabling more precise control over its behavior. Demonstrations of application devices highlight the actuator’s versatility in flexible robotics, showcasing its potential for advanced applications. This innovation represents a considerable step towards achieving more adaptable and functional soft robotic systems, paving the way for future developments in this area.

Bulk photovoltaic effect in ferroelectric nematic liquid crystals.

The bulk photovoltaic (BPV) effect in ferroelectric liquid crystals is of increasing scientific interest owing to its great potential for light-energy conversion. The ferroelectric nematic phase exhibits a huge spontaneous polarization that can be aligned to a preferred direction. In this Letter, we investigate the tensorial properties of the BPV effect in the planarly aligned ferroelectric nematic phase of the liquid crystalline material RM734. A steady-state short-circuit photocurrent of ~160 pA and an open-circuit photovoltage of ~50 mV were observed in a cell with a thickness of 5.5 µm under the illumination of ultraviolet light without any bias voltage. Based on the photocurrent measurements in different electrode configurations, the non-zero elements of the BPV tensor were obtained. The BPV effect is attributed to the combination of the spontaneous polarization and the asymmetric distribution of photoinduced charge carriers. This study not only provides an understanding of the bulk PV mechanism in soft ferroelectrics but also promises a wide range of unprecedented, to the best of our knowledge, benefits for light harvesting to engineer marketable photovoltaic devices.

(Invited) Semiconductor Nanostructures for Light Energy Conversion

This talk will review some of the key developments of semiconductor quantum dots based light energy conversion. Semiconductor nanostructures are finding new ways to design light energy conversion devices (e.g., thin film solar cells and light emitting devices). The decreased consumption of energy during the manufacture and the lessened use of semiconductor materials lowers the overall carbon footprint with energy payback time less than a year for such devices. The early studies which focused on the synthesis of various semiconductor nanostructures and exploration of their size dependent optical and electronic properties have led to their their integration in high efficiency thin film solar cells.. Unlike solar cell devices, photocatalytic processes are yet to deliver conversion efficiencies and stability that can make them compatible for practical applications. Understanding the limitations imposed by interfacial charge transfer processes remains a key to further advance photocatalytic systems for chemical energy storage. Recent developments in utilizing semiconductor nanostructures for light energy conversion and storage will be discussed.

(Invited) Designing Photocatalytic Membrane to Direct Electron and Hole Transport

Surface interaction of chromophore or redox active molecule which dictate the efficiency of energy/electron transfer, plays an important role in realizing photocatalytic and optoelectronic applications. Metal halide perovskite nanocrystals are interesting in the sense that they can either transfer energy or selectively transfer electrons or holes to the adsorbed molecules.1,2 The presentation will focus on two specific scenarios of the flow of energy and electron processes in CsPbX3 (X= Br, I) nanocrystal-molecular hybrids. The energy transfer is probed through three moleculr acceptors – rhodamine B (RhB), rhodamine isothiocyanate (RhB-NCS), and rose Bengal (RoseB), which contain an increasing degree of heavy atom pendant groups. Electron and/or hole transfer from excited CsPbX3 nanocrystals to a molecular relay present near the interface offers another avenue to directly convert light energy into chemical energy. Such interfacial electron transfer of semiconductor nanocrystals has been widely explored in photocatalytic processes. A basic understanding of the fundamental differences between the two excited deactivation processes (energy and charge transfer) and ways to modulate them should enable design of more efficient light harvesting assemblies with semiconductor and molecular systems.

(Invited) Changes in Electric Double-Layer Structures Under Localized Surface Plasmon Excitation

For the visible light energy conversion, the localized surface plasmon resonance (LSPR), which is the collective oscillations of free electrons, should be promising. With the excitation of LSPR, the highly localized electric field generates in the vicinity of metal nanostructures. It is interesting that various unique photo-response properties, such as chemical reactions or molecular excitations, can be observed due to the enhancement of light-matter interaction.[1] To understand and control such mediated chemical reactions or electrochemical reactions, the precise understanding about the electrified interfaces of plasmonic nanostructures should be required.Especially in the electrochemical system, the electric double layer is formed due to the difference in electrochemical potential between the metal interface and solution. The study of the surface potential is important for the design of chemical reactions because the surface potential at the liquid-solid interface is dependent on the physical properties of the systems. The zeta potential which is the potential of the slipping surface near the Stern layer of the diffusion layer could provide such information. From this point of view, in this study, we investigated the electric double-layer structures through the examination of the zeta potential under LSPR excitation condition. To obtain the zeta potential, we have performed the streaming potential method using Au nanoisland structures under visible light illuminations to excite the LSPR. It was interesting that the zeta potential was drastically changes under the visible light illumination conditions. This zeta potential change indicates the changes in the electric double layer structures through the excitation of LSPR. Through the investigations of incident wavelength dependence or the substrate dependences, the effects for the LSPR excitations on the electric double layer structure have been revealed. The present work would provide the fundamental knowledge about the effect on the LSPR excitation at solid-liquid interfaces.[1] H. Minamimoto et al., Acc. Chem. Res., 2022, 55(6), 809.

Solution-Phase Synthesis and Composition-Dependent Optical Properties of Less-Toxic Multinary Ag–Mn–Sn–S Quantum Dots

Introduction Multinary quantum dots (QDs) have been promising materials as an efficient light absorber in solar light energy conversion systems. These QDs including Cu(In,Ga)(S,Se)2 and Cu2ZnSn(S,Se)4 QDs, consisting of less-toxic elements, are known for their high absorption coefficient and excellent processability. However, the cation disorder in Cu2ZnSn(S,Se)4 has been observed to cause a bandgap fluctuation and an emergence of additional antisite defects1. An effective approach to mitigating such disorder involves the substitution of Cu or Zn with larger cations. Here we focus on Ag2MnSnS4 (AMTS) due to similar optical properties with Cu2ZnSn(S,Se)4 QDs. The energy gap of bulk AMTS was reported to ca. 2.0 eV2, making it suitable for efficient solar light energy conversion systems. However, creating AMTS structures can be challenging, often requiring high temperatures or pressures. Thus, a simpler synthesis route for preparing QDs will offer a new perspective in addressing this issue, and the size reduction will enable to tune their optical bandgap. In this study, we report for the first time the solution-phase preparation of AMTS QDs. The resulting QDs exhibited composition-dependent optical properties depending on the Ag/metal ratio. Experimental The synthesis of AMTS QDs was conducted by a facile colloidal heating-up method. Precursors of corresponding metal complexes and sulfur powder were dispersed in a mixture solvent of 1-dodecanethiol (DDT) and oleylamine (OLAm), followed by the heat treatment at more than 423 K. Thus-obtained solution was subjected to centrifugation to remove large precipitates, and target QDs were isolated from the supernatant by adding methanol and ethanol as a non-solvent, followed by centrifugation. Results and Discussion AMTS QDs with diameters less than 6 nm were obtained. The absorption spectra of AMTS QDs varied with the Ag/metal ratio. The onset wavelength was blue-shifted from ca. 670 nm to ca. 500 nm with a decrease in the Ag fraction. In the case of Ag/metal= 0.50, that is, the stoichiometric Ag2MnSnS4, the bandgap was determined to 2.0 eV, being similar to the bulk bandgap of monoclinic Ag2MnSnS4 2. The optical bandgap was monotonously increased from 2.0 eV to 2.4 eV as the Ag/metal ratio decreased from 0.50 to 0.05.The electronic energy structure of AMTS QDs was determined from the ionization energy of the QDs, which was evaluated from the onset energy of the photoelectron yield spectra in air. The conduction band minimum level shifted from –3.5 eV to –3.1 eV with a decrease in the Ag fraction, while the valence band maximum was constant at ca. –5.5 eV. The crystal structure and particle morphology were almost unchanged even when the particle composition was varied, indicating that the change in bandgap resulted from the composition. The stability of QDs was improved by surface coating with a ZnS shell. Subsequent ligand exchange with a hydrophilic molecule enabled the uniform dispersion of QDs in an aqueous solution without changing their optical properties and chemical composition. These findings open up possibilities for utilizing ATMS QDs in various applications such as photocatalysis and bioimaging in aqueous media. Reference 1 J. Kumar, and S. Ingole, J. Alloys Compd., 865, 158113 (2021). 2 Frank N. Keutsch, Dan Topa, Rie Takagi Fredrickson, E. Makovicky, and W.H. Paar, Mineral. Mag. 83(2), 233–238 (2019).

Beyond the First Coordination Sphere─Manipulating the Excited-State Landscape in Iron(II) Chromophores with Protons.

Molecular transition metal chromophores play a central role in light harvesting and energy conversion. Recently, earth-abundant transition-metal-based chromophores have begun to challenge the dominance of platinum group metal complexes in this area. However, the development of new chromophores with optimized photophysical properties is still limited by a lack of synthetic methods, especially with respect to heteroleptic complexes with functional ligands. Here, we demonstrate a facile and efficient method for the combination of strong-field carbenes with the functional 2,2'-bibenzimidazole ligand in a heteroleptic iron(II) chromophore complex. Our approach yields two isomers that differ predominantly in their excited-state lifetimes based on the symmetry of the ligand field. Deprotonation of both isomers leads to a significant red-shift of the metal-to-ligand charge transfer (MLCT) absorption and a shortening of excited-state lifetimes. Femtosecond transient absorption spectroscopy in combination with quantum chemical simulations and resonance Raman spectroscopy reveals the complex relationship between protonation and photophysical properties. Protonation is found to tip the balance between MLCT and metal-centered (MC) excited states in favor of the former. This study showcases the first example of fine-tuning of the excited-state landscape in an iron(II) chromophore through second-sphere manipulations and provides a new perspective to the challenge of excited-state optimizations in 3d transition metal chromophores.

Aggregation promotes charge separation in fullerene-indacenodithiophene dyad

Fast photoinduced charge separation (CS) and long-lived charge-separated state (CSS) in small-molecules facilitate light-energy conversion, while simultaneous attainment of both remains challenging. Here we accomplish this through aggregation based on fullerene-indacenodithiophene dyads. Transient absorption spectroscopy reveals that, compared to solution, the CS time in aggregates is accelerated from 41.5 ps to 0.4 ps, and the CSS lifetime is prolonged from 311.4 ps to 40 μs, indicating that aggregation concomitantly promotes fast CS and long-lived CSS. Fast CS arises from the hot charge-transfer states dissociation, opening up additional resonant channels to free carriers (FCs); subsequently, charge recombination into intramolecular triplet CSS becomes favorable mediated by spin-uncorrelated FCs. Different from fullerene/indacenodithiophene blends, the unique CS mechanism in dyad aggregates reduces the long-lived CSS dependence on molecular order, resulting in a CSS lifetime 200 times longer than blends. This endows the dyad aggregates to exhibit both photoelectronic switch properties and superior photocatalytic capabilities.

Size Dependence of Ultrafast Electron Transfer from Didodecyl Dimethylammonium Bromide-Modified CsPbBr3 Nanocrystals to Electron Acceptors.

Charge transfer efficiencies in all-inorganic lead halide perovskite nanocrystals (NCs) are crucial for applications in photovoltaics and photocatalysis. Herein, CsPbBr3 NCs with different sizes are synthesized by varying the ligand contents of didodecyl dimethylammonium bromide at room temperature. Adding benzoquinone (BQ) molecules leads to a decrease in the PL intensities and PL decay times in NCs. The electron transfer (ET) efficiency (ηET) increases with NC size in complexes of CsPbBr3 NCs and BQ molecules (NC-BQ complexes), when the same concentration of BQ is maintained, as investigated by transient photobleaching and photoluminescence spectroscopies. Controlling the same number of attached BQ acceptor molecules per NC induces the same ηET in NC-BQ complexes even though with different NC sizes. Our findings provide new insights into ultrafast charge transfer behaviors in perovskite NCs, which is important for designing efficient light energy conversion devices.