Unexpected Boosted Solar Water Oxidation by Nonconjugated Polymer-Mediated Tandem Charge Transfer

Split-type photoelectrochemical biosensing for miRNA-144 assay based on a ZnIn2S4/TiO2 heterojunction

Highly efficient photoelectroactive materials with simple synthesis are essential for photoelectrochemical (PEC) biosensing. This study reports a facile hydrothermal synthesis of ZnIn2S4/TiO2 type II heterojunctions on FTO, creating a robust sensing platform. The favorable band energy alignment between ZnIn2S4 and TiO2 enhances charge transfer and charge carrier separation under illumination, resulting in a 24-fold photocurrent increase compared to TiO2. By combining magnetic separation with hybridization chain reaction (HCR) signal amplification, a highly sensitive split-type biosensor for miRNA-144 was developed. The resulting biosensor demonstrated a linear detection range from 10 fM to 1 nM, with a limit of detection (LOD) of 6.75 fM. Furthermore, excellent selectivity, long-term stability, and reliable miRNA-144 detection in spiked human serum samples were demonstrated, highlighting the great potential of this PEC biosensor for clinical miRNA applications.

Glutathione: a naturally occurring tripeptide for functional metal nanomaterials

Glutathione (GSH), a naturally occurring tripeptide, plays an important role as an intracellular antioxidant in the physiological microenvironment and participates in redox balance, detoxification, and cellular and disease regulation. The unique structural features of GSH, including the reductive thiol and multiple coordination sites (carboxyl and amino group), make it a significant molecule not only in the physiological context but also as a ligand in the development of functional metal nanomaterials. In this context, GSH's role as a protective ligand and reducing agent in surface etching and ligand exchange reactions has been explored at the molecular level, expanding the diversity of GSH-protected metal nanomaterials. With photoluminescence (PL) as one of its most intriguing properties, investigations into GSH's influence on PL properties emphasize its multifaceted coordination capabilities in surface coating, charge transfer from electron-rich functional groups, chirality arising from its unique structure, and available conjugation sites. Moreover, the biocompatibility of GSH, combined with the synergistic effect of metal components, renders GSH-protected nanomaterials an "Inseparable Duo" highly suited for applications in bio-sensing, bio-imaging via PL radiative decay and anti-cancer bio-therapies through photothermal therapy, photodynamic therapy, and radiotherapy. By exploring the multifaceted roles of GSH, this Perspective aims to highlight pathways including the encouragement of deeper synthetic exploration, innovative design at the bio-nano interface, and expanded nanobiomedical applications.

Magic-Sized Nanoclusters-Induced Cascade Tandem Charge Transfer for Solar Water Oxidation

Magic-sized nanoclusters (MSCs) have been attracting enduring interest by virtue of the quantum confinement effect, discrete energy band structure, and enriched catalytic active sites. Nevertheless, up to date, exploration of MSCs artificial photosystems and fine-tuning of spatial vectorial charge transfer in photoredox catalysis have so far been scarcely reported. Hence, we employed a facile and easily accessible layer-by-layer (LbL) assembly strategy to highly ordered, alternately, and periodically deposit oppositely charged tailor-made transition metal chalcogenides (TMCs) MSCs and non-conjugated polymer (NCP) building blocks on the MO substrate, resulting in the MO/(NCP-TMCs MSCs)n multilayer heterostructures. It is affirmed that the ultra-thin NCP uniformly intercalated at the interface of every TMCs MSCs layer fosters the unidirectional electron flow from TMCs MSCs to MO substrate with the assistance of NCP, and moreover the multilayered interface configuration benefits the establishment of cascade tandem charge transfer route, synergistically giving rise to the significantly enhanced charge separation and boosted solar water oxidation performances of MO/(TMCs MSCs-NCP)n heterostructure under simulated solar light irradiation. Our work elucidates the specific roles of NCP and MSCs as charge relay mediators and photosensitizers, affording a quintessential paradigm to rationally regulate the photocarrier transport and separation over MSCs for solar energy conversion.

Atomically Precise Metal Nanocluster-Mediated Solar Hydrogen Production

Atomically precise metal nanoclusters (NCs) stand out within metal nanomaterials due to the distinctive atomic stacking configuration, discrete energy band, quantum confinement effect, and enriched catalytic centers, positioning them as promising substitutes for conventional photosensitizers in solar energy absorption and utilization. However, the light-induced poor stability and ultrashort carrier lifetime of metal NCs as well as the difficulties in modulating charge migration collectively constrain their potential applications in photoredox catalysis. In this work, we conceptually construct the metal NC artificial photosystems by electrostatically self-assembling l-glutathione (GSH)-capped Au25(GSH)18 NCs onto transition metal chalcogenide (TMC) substrates (CdS, Zn0.5Cd0.5S, and ZnIn2S4) at ambient conditions. Benefiting from the advantageous photosensitization effect of Au25@(GSH)18 NCs, these self-assembled TMCs/Au25@(GSH)18 NC heterostructures exhibit significantly enhanced photocatalytic hydrogen production performance (λ > 420 nm). This universal photoactivity enhancement is predominantly attributed to the suitable energy level alignment between Au25@(GSH)18 NCs and TMCs, which considerably enhances the interfacial charge transfer and effectively extends the carrier lifetime. In addition, the photocatalytic mechanism is determined. This work would spark continued interest in crafting diverse atomically precise metal NC photocatalytic systems toward solar-to-hydrogen energy conversion.

Solvent-free fabrication of ultrathin two-dimensional metal oxides/sulfides in a fixed interlayer by geometric confinement

Two-dimensional (2D) nanomaterials display unique characteristics owing to their ultrahigh surface-to-volume ratio and quantum confinement effects. Nonetheless, seeking a versatile and facile method to rationally shape ultrathin 2D frameworks is still an appealing challenge. Herein, a series of ultrathin 2D metal oxide crystals (2D MOs), including 3d transition metals (Ti, Cr, Mn, Fe, Co, Ni, Cu, Zr, W), lanthanide (Ce) and nontransition metal (In, Sn, Bi) oxides, were created through a confined interlayer growth strategy in combination with melt infiltration, in which no complicated chemistry or sophisticated equipment was needed. The 2D oxides presented lamellar constructions with high crystallinity, and the thickness was strictly limited to ~ 1 nm. The crystallization process, including the Frank-van der Merwe mode and the Volmer-Weber mode, was described. The defects and distortions of 2D TiO2 reduced the optical band gap and improved the sunlight utilization efficiency, thus accelerating the photocatalytic activity. This method could be extended to the preparation of 2D polymetallic oxides, metal sulfides etc., which enables the development of versatile systems for ultrathin 2D frameworks, especially for nonlayered structures originally.

Surmounting the instability of atomically precise metal nanoclusters towards boosted photoredox organic transformation

Atomically precise metal nanoclusters (NCs) have recently been recognized as an emerging sector of metal nanomaterials but suffer from light-induced poor stability, giving rise to the detrimental self-transformation into metal nanocrystals (NYs), losing the photosensitization effect and ultimately retarding their widespread applications in photoredox catalysis. Are metal NCs definitely superior to metal NYs in heterogeneous photocatalysis in terms of structural merits? To unlock this mystery, herein, we conceptually demonstrate how to rationally manipulate the instability of metal NCs to construct high-efficiency artificial photosystems and examine how the metal NYs self-transformed from metal NCs influence charge transfer in photoredox selective organic transformation. To our surprise, the results indicate that the Schottky-type electron-trapping ability of Au NYs surpasses the photosensitization effect of glutathione (GSH)-protected Au clusters [Au25(GSH)18 NCs] in mediating charge separation and enhancing photoactivities towards selective photoreduction of aromatic nitro compounds to amino derivatives and photocatalytic oxidation of aromatic alcohols to aldehydes under visible light irradiation. This work strategically provides new insights into the inherent instability of metal NCs utilized for photocatalysis and reinforces our fundamental understanding on metal NC-based artificial photosystems for solar energy conversion.

Efficient Photocatalytic Hydrogen Production Using In-Situ Polymerized Gold Nanocluster Assemblies

Gold nanoparticles (NPs) are widely recognized as co-catalysts in semiconductor photocatalysis for enhancing hydrogen production efficiency, but they are often overlooked as primary catalysts due to the rapid recombination of excited-state electrons. This study presents an innovative gold-based photocatalyst design utilizing an in situ dopamine polymerization-guided assembly approach for efficient H2 generation via water splitting. By employing gold superclusters (AuSCs; ≈100 nm) instead of ultra-small gold nanoclusters (AuNCs; ≈2 nm) before polymerization, unique nanodisk-like 3D superstructures consisting of agglomerated 2D polydopamine (PDA) nanosheets with a high percentage of uniformly embedded AuNCs are created that exhibit enhanced metallic character post-polymerization. The thin PDA layer between adjacent AuNCs functions as an efficient electron transport medium, directing excited-state electrons toward the surface and minimizing recombination. Notably, the AuSCs@PDA structure shows the largest potential difference (26.0 mV) compared to AuSCs (≈18.4 mV) and PDA NPs (≈14.6 mV), indicating a higher population of accumulated photo-generated carriers. As a result, AuSCs@PDA achieves a higher photocurrent density, improved photostability, and lower charge transfer resistance than PDA NPs, AuSCs, or AuNCs@PDA, with the highest hydrogen evolution rate of 3.20 mmol g-1 h-1. This work highlights a promising in situ polymerization strategy for enhancing photocatalytic hydrogen generation with metal nanoclusters.

A Photo-Assisted Zinc-Air Battery with MoS2/Oxygen Vacancies Rich TiO2 Heterojunction Photocathode

Converting solar energy into electrochemical energy is a sustainable strategy, but the design of photo-assisted zinc-air battery (ZAB) with efficient utilization of sunlight faces huge challenges. Herein, a photo-assisted ZAB of a three-electrode system using MoS2/oxygen vacancies-rich TiO2 heterojunction as charge cathode and Fe, N-doped carbon matrix (FeNC) as discharge cathode is constructed, where MoS2 is chosen as solar light-responsive catalytic material and TiO2 acts as electron transport layer and hole blocking layer, arising from a train of thought for efficient charging under sunlight irradiation and light-independent discharging. The introduction of oxygen vacancies in TiO2 facilitates the temporary trapping of carriers and triggers rapid carrier transfer at the interface of the heterojunction, which hinders the recombination of photogenerated holes, thereby facilitating their further participation in the oxygen evolution reaction. Moreover, FeNC exhibits superior oxygen reduction reaction performance due to strong d-π interactions. As a result, the well-built ZABs deliver a low charge voltage (0.71 V) under illumination at 0.1 mA cm-2, and a high power density (167.6 mW cm-2) in dark. This work paves a special way for the development of ZABs by directly harvesting solar energy in charging and efficiently discharging regardless of lighting conditions.

Identifying Root Origin of Insulating Polymer Mediated Solar Water Oxidation

Rational construction of high-efficiency photoelectrodes with optimized carrier migration to the ideal active sites, is crucial for enhancing solar water oxidation. However, complexity in precisely modulating interface configuration and directional charge transfer pathways retards the design of robust and stable artificial photosystems. Herein, a straightforward yet effective strategy is developed for compact encapsulation of metal oxides (MOs) with an ultrathin non-conjugated polymer layer to modulate interfacial charge migration and separation. By periodically coating highly ordered TiO2 nanoarrays with oppositely charged polyelectrolyte of poly(dimethyl diallyl ammonium chloride) (PDDA), MOs/polymer composite photoanodes are readily fabricated under ambient conditions. It is verified that electrons photogenerated from the MOs substrate can be efficiently extracted by the ultrathin solid insulating PDDA layer, significantly boosting the carrier transport kinetics and enhancing charge separation of MOs, and thus triggering a remarkable enhancement in the solar water oxidation performance. The origins of the unexpected electron-withdrawing capability of such non-conjugated insulating polymer are unambiguously uncovered, and the scenario occurring at the interface of hybrid photoelectrodes is elucidated. The work would reinforce the fundamental understanding on the origins of generic charge transport capability of insulating polymer and benefit potential wide-spread utilization of insulating polymers as co-catalysts for solar energy conversion.

Microenvironment Engineering of Heterogeneous Catalysts for Liquid-Phase Environmental Catalysis

Environmental catalysis has emerged as a scientific frontier in mitigating water pollution and advancing circular chemistry and reaction microenvironment significantly influences the catalytic performance and efficiency. This review delves into microenvironment engineering within liquid-phase environmental catalysis, categorizing microenvironments into four scales: atom/molecule-level modulation, nano/microscale-confined structures, interface and surface regulation, and external field effects. Each category is analyzed for its unique characteristics and merits, emphasizing its potential to significantly enhance catalytic efficiency and selectivity. Following this overview, we introduced recent advancements in advanced material and system design to promote liquid-phase environmental catalysis (e.g., water purification, transformation to value-added products, and green synthesis), leveraging state-of-the-art microenvironment engineering technologies. These discussions showcase microenvironment engineering was applied in different reactions to fine-tune catalytic regimes and improve the efficiency from both thermodynamics and kinetics perspectives. Lastly, we discussed the challenges and future directions in microenvironment engineering. This review underscores the potential of microenvironment engineering in intelligent materials and system design to drive the development of more effective and sustainable catalytic solutions to environmental decontamination.

Modulating built-in electric field via Bi-VO4-Fe interfacial bridges to enhance charge separation for efficient photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting on semiconductor electrodes is considered to be one of the important ways to produce clean and sustainable hydrogen fuel, which is a great help in solving energy and environmental problems. Bismuth vanadate (BiVO4) as a promising photoanode for photoelectrochemical water splitting still suffers from poor charge separation efficiency and photo-induced self-corrosion. Herein, we develop heterojunction-rich photoanodes composed of BiVO4 and iron vanadate (FeVO4), coated with nickel iron oxide (NiFeOx/FeVO4/BiVO4). The formation of the interface between BiVO4 and FeVO4 (Bi-VO4-Fe bridges) enhances the interfacial interaction, resulting in improved performance. Meanwhile, high-conductivity FeVO4 and NiFeOx oxygen evolution co-catalysts effectively enhance bulk electron/hole separation, interface water's kinetics and photostability. Concurrently, the optimized NiFeOx/FeVO4/BiVO4 possesses a remarkable photocurrent density of 5.59 mA/cm2 at 1.23 V versus reversible hydrogen electrode (vs RHE) under AM 1.5G (Air Mass 1.5 Global) simulated sunlight, accompanied by superior stability without any decreased of its photocurrent density after 14 h. This work not only reveals the crucial role of built-in electric field in BiVO4-based photoanode during PEC water splitting, but also provides a new guide to the design of efficient photoanode for PEC.

Systematic Constructing FeOCl/BiVO4 Hetero-Interfacial Hybrid Photoanodes for Efficient Photoelectrochemical Water Splitting

Bismuth vanadate (BiVO4), as a promising photoanode for photoelectrochemical (PEC) water splitting, suffers from poor charge separation efficiency and light absorption efficiency. Herein, iron oxychloride (FeOCl) is introduced as a novel cocatalyst simply grafted on BiVO4 to construct an integrated photoanode, enhancing PEC performance. The optimized FeOCl/BiVO4 photoanode exhibits a superior photocurrent density value of 5.23 mA cm-2 at 1.23 V versus reversible hydrogen electrode (RHE) under AM 1.5G illuminations. From experimental analysis, such high PEC performance is ascribed to the unique properties of FeOCl, facilitating charge transport, increasing light absorption efficiency, and promoting water oxidation kinetics. Density functional theory calculations further confirm that FeOCl optimizes the Gibbs free energy of H and O-containing intermediates (OOH*) during PEC processes, boosting the catalytic kinetics of PEC water splitting. This work presents FeOCl as a promising catalyst for constructing high efficient PEC water-splitting photoanodes.

Atomically precise metal nanoclusters combine with MXene towards solar CO2 conversion

Atomically precise metal nanoclusters (NCs) have been deemed a new generation of photosensitizers for light harvesting on account of their quantum confinement effect, peculiar atom-stacking mode, and enriched catalytic active sites. Nonetheless, to date, precise charge modulation over metal NCs has still been challenging considering their ultra-short carrier lifetime and poor stability. In this work, we conceptually demonstrate the integration of metal NCs with MXene in transition metal chalcogenide (TMC) photosystems via a progressive, exquisite, and elegant interface design to trigger tunable, precise and high-efficiency charge motion over metal NCs, stimulating a directional carrier transport pathway. In this customized ternary heterostructured photosystem, metal NCs function as light-harvesting antennas, MXene serves as a terminal electron reservoir, and the TMC substrate provides suitable energy level alignment for retracting photocarriers of metal NCs, giving rise to a spatial cascade charge transport route and markedly boosting charge separation efficiency. The interface configuration and energy level alignment engineering synergistically contribute to the considerably enhanced visible-light-driven photocatalytic CO2-to-CO reduction performance of the metal NCs/TMCs/MXene heterostructure. The intermediate active species during the photocatalytic CO2 reduction are unambiguously determined, based on which the photocatalytic mechanism is elucidated. Our work will provide an inspiring idea to bridge the gap between atomically precise metal NCs and MXene in terms of controllable charge migration for solar-to-fuel conversion.

Photocarrier tunneling triggering CO2 photocatalysis

Solar CO2 reduction to renewable hydrocarbon fuels offers a promising pathway to carbon neutrality, but it is retarded by tough CO2 activation, complicated mechanisms, sluggish charge transport kinetics, and a scarcity of strategies for precise tuning of charge transport pathways. Herein, we first conceptually design a novel insulating polymer-mediated electron-tunneling artificial photosystem via progressive interface configuration regulation, wherein tailor-made Ag@citrate nanocrystals (NCs) are controllably self-assembled on transition metal chalcogenides (TMCs) assisted by an ultrathin insulating polymer interim layer, i.e., poly(allylamine hydrochloride) (PAH). In this multilayered nano-architecture, a solid ultra-thin insulating PAH interim layer serves as an unexpected charge tunneling mediator to stimulate smooth electron transfer from the TMC substrate to the terminal electron reservoirs of Ag@citrate NCs, engendering the tandem charge transfer route and significantly boosting the visible-light-driven photocatalytic CO2-to-syngas conversion performances. Furthermore, we have ascertained that such TMC-insulating polymer-metal NC tunneling photosystems are universal. This study would spark new inspiration for unleashing the long-term neglected charge tunneling capability of insulating polymers and diversifying non-conjugated polymer-based artificial photosystems for solar-to-fuel energy conversion.

High-Precision Single-Cell microRNA Therapy by a Functional Nanopipette with Sensitive Photoelectrochemical Feedback

This work proposes the concept of single-cell microRNA (miR) therapy and proof-of-concept by engineering a nanopipette for high-precision miR-21-targeted therapy in a single HeLa cell with sensitive photoelectrochemical (PEC) feedback. Targeting the representative oncogenic miR-21, the as-functionalized nanopipette permits direct intracellular drug administration with precisely controllable dosages, and the corresponding therapeutic effects can be sensitively transduced by a PEC sensing interface that selectively responds to the indicator level of cytosolic caspase-3. The experimental results reveal that injection of ca. 4.4 × 10-20 mol miR-21 inhibitor, i.e., 26488 copies, can cause the obvious therapeutic action in the targeted cell. This work features a solution to obtain the accurate knowledge of how a certain miR-drug with specific dosages treats the cells and thus provides an insight into futuristic high-precision clinical miR therapy using personalized medicine, provided that the prerequisite single-cell experiments are courses of personalized customization.

Ti3C2Tx MXene-based hybrid nanocoating for flame retardant, early fire-warning and piezoresistive tension sensing smart polyester fabrics

Flammability feature of textiles is a big underlying risk causing fire disasters. The fabrication of reliable fire resistant and quick fire warning fabrics is imperative but challenging. Herein, three types of early fire-warning polyester fabrics, namely, FPP@AM-X, FPP@PM-X and FPP@AX-M1, with good flame retardant and piezoresistive sensing performance were developed by fabricating polyethyleneimine (PEI), ammonium polyphosphate (APP), phytic acid (PA) and MXenes onto phosphorus-containing flame retardant polyethylene terephthalate (FRPET) via polydopamine (PDA) mediated layer-by-layer self-assembly. Owing to the improved thermoelectric properties of MXenes, FPP@A5-M1 exhibited a maximum thermoelectric voltage of 0.59 mV at a temperature difference of 130 °C and can provide an ideal cyclic early fire warning response within 4 s. In addition, due to the synergistic flame retardant effect of MXenes and APP in the coating layer, FPP@A5-M1 could be self-extinguished within 2 s after ignition and the value of peak heat release ratio and total smoke production decreased by 41.9% and 30.4%, respectively. Besides, the MXene-based hybrid coated fabric can detect the movement of human fingers and elbows, illustrating its potential application in piezoresistive tension sensing. This work provides a new route to designing and developing multi-functional and smart fire protection fabrics.

Optical and Electrical Modulation Strategies of Photoelectrodes for Photoelectrochemical Water Splitting

When constructing efficient, cost-effective, and stable photoelectrodes for photoelectrochemical (PEC) systems, the solar-driven photo-to-chemical conversion efficiency of semiconductors is limited by several factors, including the surface catalytic activity, light absorption range, carrier separation, and transfer efficiency. Accordingly, various modulation strategies, such as modifying the light propagation behavior and regulating the absorption range of incident light based on optics and constructing and regulating the built-in electric field of semiconductors based on carrier behaviors in semiconductors, are implemented to improve the PEC performance. Herein, the mechanism and research advancements of optical and electrical modulation strategies for photoelectrodes are reviewed. First, parameters and methods for characterizing the performance and mechanism of photoelectrodes are introduced to reveal the principle and significance of modulation strategies. Then, plasmon and photonic crystal structures and mechanisms are summarized from the perspective of controlling the propagation behavior of incident light. Subsequently, the design of an electrical polarization material, polar surface, and heterojunction structure is elaborated to construct an internal electric field, which serves as the driving force to facilitate the separation and transfer of photogenerated electron-hole pairs. Finally, the challenges and opportunities for developing optical and electrical modulation strategies for photoelectrodes are discussed.

Interfacial Se-O Bonds Modulating Spatial Charge Distribution in FeSe2/Nb:Fe2O3 with Rapid Hole Extraction for Efficient Photoelectrochemical Water Oxidation

Surface engineering is an effective strategy to improve the photoelectrochemical (PEC) catalytic activity of hematite, and the defect states with abundant coordinative unsaturation atoms can serve as anchoring sites for constructing intimate connections between semiconductors. On this basis, we anchored an ultrathin FeSe2 layer on Nb5+-doped Fe2O3 (FeSe2/Nb:Fe2O3) via interfacial Se-O chemical bonds to tune the surface potential. Density functional theory (DFT) calculations indicate that amorphous FeSe2 decoration could generate electron delocalization over the composite photoanodes so that the electron mobility was improved to a large extent. Furthermore, electrons could be transferred via the newly formed Se-O bonds at the interface and holes were collected at the surface of electrode for PEC water oxidation. The desired charge redistribution is in favor of suppressing charge recombination and extracting effective holes. Later, work function calculations and Mott-Schottky (M-S) plots demonstrate that a type-II heterojunction was formed in FeSe2/Nb:Fe2O3, which further expedited carrier separation. Except for spatial carrier modulation, the amorphous FeSe2 layer also provided abundant active sites for intermediates adsorption according to the d band center results. In consequence, the target photoanodes attained an improved photocurrent density of 2.42 mA cm-2 at 1.23 V versus the reversible hydrogen electrode (RHE), 2.5 times as that of the bare Fe2O3. This study proposed a defect-anchoring method to grow a close-connected layer via interfacial chemical bonds and revealed the spatial charge distribution effects of FeSe2 on Nb:Fe2O3, giving insights into rational designation in composite photoanodes.

Self-Transformation of Atomically Precise Alloy Nanoclusters to Plasmonic Alloy Nanocrystals: Evaluating Photosensitization in Solar Water Oxidation

Atomically precise alloy nanoclusters (NCs) inherit the advantages of homometal NC counterparts such as atomic stacking fashion, quantum confinement effect, and enriched catalytic active sites and simultaneously possess the advantageous physicochemical properties such as significantly enhanced photostability, ideal photosensitization efficiency, and favorable energy band structure. Nevertheless, elucidation of the roles of alloy NCs and alloy nanocrystals (NYs) in boosting solar water oxidation has so far not yet been reported owing to the deficiency of applicable alloy NC photosystems. Herein, utilizing the generic thermal-induced self-transformation of alloy NCs to alloy NYs, we comprehensively explore the photosensitization properties of glutathione (GSH)-capped alloy NCs (AgxAu1-x@GSH and CuxAu1-x@GSH) and the corresponding alloy NY (AgAu and CuAu) counterparts in solar water oxidation reaction. The results imply that photoelectrons of alloy NCs surpass the hot electrons over plasmonic alloy NYs in stimulating the PEC water oxidation reaction. The photoelectrons of alloy NCs demonstrate lower interfacial charge-transfer resistance, longer carrier lifetime, and a more enhanced photosensitization effect with respect to the plasmonic alloy NYs, contributing to the significantly boosted photoelectrochemical water oxidation activities. Moreover, we found that our result is universal.

Roles of Cobalt-Coordinated Polymeric Perylene Diimide in Hematite Photoanodes for Improved Water Oxidation

Interfacial charge recombination is a permanent issue that impedes the photon energy utilization in photoelectrochemical (PEC) water splitting. Herein, a conjugated polymer, urea linked perylene diimide polymer (PDI), is introduced to the designation of hematite-based composite photoanodes. On account of its unique molecule structure with abundant electronegative atoms, the O and N atoms with lone electron pairs can bond with Fe atoms at the surface of Zr4+ doped α-Fe2 O3 (Zr:Fe2 O3 ) and thus establish charge transfer channels for expediting hole separation and migration. Meanwhile, PDI molecules can passivate the surface states in Zr:Fe2 O3 , which is in favor of suppressing carrier recombination. Particularly, Co2+ is used to coordinate with PDI (Co-PDI) to accelerate hole extraction as well as utilization, and the as-obtained Co-PDI form type-II heterojunction with Zr:Fe2 O3 . Such a photoanode configuration takes advantage of the unique molecule structure of PDI, and the target Co-PDI/Zr:Fe2 O3 photoanodes eventually attain a photocurrent density of 2.17 mA cm-2 , which is inspirational for unearthing the potential use of conjugative molecules in PEC fields.

Effective photodegradation of antibiotics by guest-host synergy between photosensitizer and bismuth vanadate: Underlying mechanism and toxicity assessment

The removal of antibiotics in wastewater has attracted increasing attention. Herein, a superior photosensitized photocatalytic system was developed with acetophenone (ACP) as the guest photosensitizer, bismuth vanadate (BiVO₄) as the host catalyst and poly dimethyl diallyl ammonium chloride (PDDA) as the bridging complex, and used for the removal of sulfamerazine (SMR), sulfadiazine (SDZ) and sulfamethazine (SMZ) in water under simulated visible light (λ > 420 nm). The obtained ACP-PDDA-BiVO₄ nanoplates attained a removal efficiency of 88.9%-98.2% for SMR, SDZ and SMZ after 60 min reaction and achieved kinetic rate constant approximately 10, 4.7 and 13 times of BiVO₄, PDDA-BiVO₄ and ACP-BiVO₄, respectively, for SMZ degradation. In the guest-host photocatalytic system, ACP photosensitizer was found to have a great superiority in enhancing the light absorption, promoting the surface charge separation-transfer and efficient generation of holes (h⁺) and superoxide radical (·O₂^-), greatly contributing to the photoactivity. The SMZ degradation pathways were proposed based on the identified degradation intermediates, involving three main pathways of rearrangement, desulfonation and oxidation. The toxicity of intermediates was evaluated and the results demonstrated that the overall toxicity was reduced compared with parent SMZ. This catalyst maintained 92% photocatalytic oxidation performance after five cyclic experiments and displayed a co-photodegradation ability to others antibiotics (e.g., roxithromycin, ciprofloxacin et al.) in effluent water. Therefore, this work provides a facile photosensitized strategy for developing guest-host photocatalysts, which enabling the simultaneous antibiotics removal and effectively reduce the ecological risks in wastewater.

Alloy Metal Nanocluster: A Robust and Stable Photosensitizer for Steering Solar Water Oxidation

Metal nanoclusters (NCs) have been unleashed as an emerging category of metal materials by virtue of integrated merits including the unusual atom-stacking mode, quantum confinement effect, and fruitful catalytically active sites. Nonetheless, development of metal NCs as photosensitizers is blocked by light-induced instability and ultrashort carrier lifespan, which remarkably retards the design of metal NC-involved photosystems, hence resulting in the decreased photoactivities. To solve these obstacles, herein, we conceptually probed the charge transfer characteristics of the BiVO₄ photoanode photosensitized by atomically precise alloy metal NCs, wherein tailor-made l-glutathione-capped gold-silver bimetallic (AuAg) NCs were controllably self-assembled on the BiVO₄ substrate. It was uncovered that alien Ag atom doping is able to effectively stabilize the alloy AuAg NCs and simultaneously photosensitize the BiVO₄ photoanode, significantly boosting the photoelectrochemical (PEC) water oxidation performances. The reasons for the robust and stable PEC water oxidation activities of the AuAg NCs/BiVO₄ composite photoanode were unambiguously unleashed. We ascertain that Ag atom doping in the staple motif of Au_x NCs efficaciously protects the NCs from rapid oxidation, enhancing the photostability, boosting the photosensitization efficiency, and thus leading to the considerably improved PEC water splitting activities compared with the homometallic counterpart. This work could afford a new strategy to judiciously tackle the inherent detrimental instability of metal NCs for solar energy conversion.

Dynamic semiconductor-electrolyte interface for sustainable solar water splitting over 600 hours under neutral conditions

Photoelectrochemical (PEC) water splitting that functions in pH-neutral electrolyte attracts increasing attention to energy demand sustainability. Here, we propose a strategy to in situ form a NiB layer by tuning the composition of the neutral electrolyte with the additions of nickel and borate species, which improves the PEC performance of the BiVO₄ photoanode. The NiB/BiVO₄ exhibits a photocurrent density of 6.0 mA cm^-2 at 1.23 V_RHE with an onset potential of 0.2 V_RHE under 1 sun illumination. The photoanode displays a photostability of over 600 hours in a neutral electrolyte. The additive of Ni²⁺ in the electrolyte, which efficiently inhibits the dissolution of NiB, can accelerate the photogenerated charge transfer and enhance the water oxidation kinetics. The borate species with B─O bonds act as a promoter of catalyst activity by accelerating proton-coupled electron transfer. The synergy effect of both species suppresses the surface charge recombination and inhibits the photocorrosion of BiVO₄.

A study on the role of plasmonic Ti3C2Tx MXene in enhancing photoredox catalysis

Engineering the spatial separation and transfer of photogenerated charge carriers has been one of the most enduring research topics in the field of photocatalysis due to its crucial role in determining the performances of photocatalysts. Herein, as a proof-of-concept, Ti₃C₂T_x MXene is coupled with a typical heterojunction of TiO₂@CdS through a co-assembly strategy to boost electron pumping towards improving the photocatalytic efficiency. In addition to the band alignment-mediated electron transfer in TiO₂@CdS-Ti₃C₂T_x heterojunctions, the plasmon-induced electric field enhancement of Ti₃C₂T_x is found to cooperate with the electron-reservoir role of Ti₃C₂T_x to extract photoinduced electrons. The synergistic dual functions of Ti₃C₂T_x promote multichannel electron transfer in TiO₂@CdS-Ti₃C₂T_x hybrids to improve the photocatalytic efficiency. These results intuitively show that there is a wide scope to manipulate the spatial separation and transfer of photoinduced electrons by cultivating the fertile ground of Ti₃C₂T_x toward boosting the efficiency of solar-to-chemical conversion.

Expediting hole transfer via surface states in hematite-based composite photoanodes

Regarding the indirect hole transfer route in hematite-based photoelectrodes, the widely accepted viewpoint is that the Fe^IVO states act as a hole transfer medium, while other types of surface states act as recombination centers. Alternatively, it has rarely been reported that the recombining surface states may contribute to the charge transport in modified photoelectrodes. In this study, we employed CoCr layered double hydroxide (LDH)/Fe₂O₃ and CoCr LDH/Zr:Fe₂O₃ as research models to investigate the distinct charge transfer pathways in composite photoanodes. Different from the adverse role of surface states at ∼0.7 V versus the reversible hydrogen electrode (r-SS) in the bare hematite photoelectrodes (Fe₂O₃ or Zr:Fe₂O₃), the r-SS in the composite photoanodes (CoCr LDH/Fe₂O₃ or CoCr LDH/Zr:Fe₂O₃) served as a hole transfer station to induce high-valent Co cations, and the position of r-SS determined the onset potential of the composite photoelectrodes. Moreover, the Fe^IVO states still acted as active intermediates to transport numerous holes to the cocatalyst, which enhanced the charge utilization efficiency at 1.23 V versus the reversible hydrogen electrode (RHE) to a large extent. Besides, a noteworthy fact is that Zr doping increased the number of active Fe^IVO states, which significantly contributed to the enhancement in current density. However, it led to a delayed onset potential because of the positively shifted surface states (r-SS and Fe^IVO). Evidently, the different surface state distributions between Fe₂O₃ and Zr:Fe₂O₃ gave rise to anisotropic charge transfer and recombination behavior in the composite photoanodes. This study gives extensive insight into the hole transfer route in composite photoanodes and reveals the surface state-tuning effects of dopants and cocatalysts, which are significant for a deep understanding of the surface states and optimal design of composite photoanodes via surface state modulation.

Thiourea-Assisted Facile Fabrication of High-Quality CsPbBr3 Perovskite Films for High-Performance Solar Cells

Inorganic CsPbBr₃ perovskite solar cells have attracted widespread attention recently because of their decent efficiency and good ambient stability. Nevertheless, the fabrication of high-quality CsPbBr₃ perovskite via the conventional solution-processing strategy still faces great challenges because the solubility of CsBr in the conventional solvent is poor. Here, we develop a facile thiourea-assisted two-step spin-coating process to fabricate a CsPbBr₃ perovskite film with high phase purity and crystallinity and enlarged crystal grains. Thiourea is introduced into the PbBr₂ layer during the first-step spin-coating process, which promotes the wettability of the PbBr₂ layer and produces the space for growing large perovskite grains. The green high-concentration CsBr/H₂O solution is adopted at the second-step spin-coating process, enabling enough CsBr to be deposited by a facile one-step process. By optimizing the content of thiourea, a compact CsPbBr₃ perovskite film with a smooth surface, large grains, and high phase purity and crystallinity is formed. Consequently, the fabricated perovskite solar cell with the architecture of FTO/TiO₂/CsPbBr₃ film/carbon exhibits a superior performance with a high efficiency of 9.11%. In addition, the unencapsulated device preserves over 90% of its initial efficiency after storage at ambient conditions for 45 days.

Biometric Photoelectrochemical-Visual Multimodal Biosensor Based on 3D Hollow HCdS@Au Nanospheres Coupled with Target-Induced Ion Exchange Reaction for Antigen Detection

Three-dimensional (3D) hollow photoactive nanomaterials can enhance light capture due to the light scattering benefiting from the unique hollow nanostructures, which contributes to the decrease in energy loss and the electron-hole recombination during the process of photoelectric conversion. Herein, a 3D hollow HCdS@Au nanosphere synthesized by the templated-assisted method and photodeposition is employed to construct a multimodal sensing platform by combining the photoelectrochemical (PEC) biosensor with colorimetric analysis and photothermal imaging. In the presence of target carcinoembryonic antigen (CEA), a sandwich structure is formed on magnetic beads based on the dual-aptamer recognition, followed by the initiation of rolling circle amplification (RCA) to bind numerous CuO-DNA probes. Upon stimulation by chlorhydric acidic, a large number of Cu²⁺ is released from CuO, which could interact with yellow HCdS@Au on electrode to produce dark CuS by ion exchange. As a result, with increased CEA level, the photocurrent is weakened and the color of electrode interface is changed from yellow to dark, which thus facilitates the PEC and colorimetric detection of CEA. Simultaneously, the formed CuS with highly photothermal effect can achieve qualitative visual analysis of CEA using a portable infrared thermal imager. This work exhibits an excellent performance for sensitive and selective detection of CEA in the dynamic working range from 0.015 to 2.4 ng/mL with a detection limit as low as 3.5 pg/mL. Moreover, the proposed PEC biosensor is successfully applied to CEA determination in human serum, which holds great promise in accurate analysis of biomarkers and early diagnosis of diseases in the clinic.

Dynamic arrest and aging of biomolecular condensates are modulated by low-complexity domains, RNA and biochemical activity

Biomolecular condensates require suitable control of material properties for their function. Here we apply Differential Dynamic Microscopy (DDM) to probe the material properties of an in vitro model of processing bodies consisting of out-of-equilibrium condensates formed by the DEAD-box ATPase Dhh1 in the presence of ATP and RNA. By applying this single-droplet technique we show that condensates within the same population exhibit a distribution of material properties, which are regulated on several levels. Removal of the low-complexity domains (LCDs) of the protein decreases the fluidity of the condensates. Structured RNA leads to a larger fraction of dynamically arrested condensates with respect to unstructured polyuridylic acid (polyU). Promotion of the enzymatic ATPase activity of Dhh1 reduces aging of the condensates and the formation of arrested structures, indicating that biochemical activity and material turnover can maintain fluid-like properties over time.

Harvesting the infrared part of solar light to promote charge transfer in Bi2S3/WO3 photoanode for enhanced photoelectrochemical water splitting

Infrared light absorbed by semiconductors hardly contributes to the solar energy conversion due to its low photon energy. Herein, photothermal effect activated by infrared part of solar light is introduced to promote the photoelectrochemical (PEC) water splitting of photoanodes. Narrow band-gap semiconductor Bi₂S₃ is deposited on the surface of WO₃ nanosheets, exhibiting a broad-spectral response. In addition to the enhanced density of photo-generated electrons, significant temperature elevation is observed for the Bi₂S₃/WO₃ composite photoanode under the illumination of infrared part of solar light because of the photothermal conversion property of Bi₂S₃. The moderately enhanced temperature accelerates charge carrier migration and finally increases the efficiency of solar energy conversion. With the assistance of photothermal effect, a remarkable photocurrent density of 4.05 mA cm^-2 at 1.23 V vs. reversible reference electrode (V_RHE) is achieved by Bi₂S₃/WO₃ composite photoanode, over 880% higher than that of the pristine WO₃. The introduction of photothermal effect activated by infrared light provides general and robust strategy to promote the PEC performance of photoanodes.

Semiconducting Polymers for Oxygen Evolution Reaction under Light Illumination

Sunlight-driven water splitting to produce hydrogen fuel has stimulated intensive scientific interest, as this technology has the potential to revolutionize fossil fuel-based energy systems in modern society. The oxygen evolution reaction (OER) determines the performance of overall water splitting owing to its sluggish kinetics with multielectron transfer processing. Polymeric photocatalysts have recently been developed for the OER, and substantial progress has been realized in this emerging research field. In this Review, the focus is on the photocatalytic technologies and materials of polymeric photocatalysts for the OER. Two practical systems, namely, particle suspension systems and film-based photoelectrochemical systems, form two main sections. The concept is reviewed in terms of thermodynamics and kinetics, and polymeric photocatalysts are discussed based on three key characteristics, namely, light absorption, charge separation and transfer, and surface oxidation reactions. A satisfactory OER performance by polymeric photocatalysts will eventually offer a platform to achieve overall water splitting and other advanced applications in a cost-effective, sustainable, and renewable manner using solar energy.

Unleashing non-conjugated polymers as charge relay mediators

The core factors affecting the efficiency of photocatalysis are predominantly centered on controllable modulation of anisotropic spatial charge separation/transfer and regulating vectorial charge transport pathways in photoredox catalysis, yet it still meets with limited success. Herein, we first conceptually demonstrate the rational design of unidirectional cascade charge transfer channels over transition metal chalcogenide nanosheets (TMC NSs: ZnIn2S4, CdS, CdIn2S4, and In2S3), which is synergistically enabled by a solid-state non-conjugated polymer, i.e., poly(diallyldimethyl ammonium chloride) (PDDA), and MXene quantum dots (MQDs). In such elaborately designed photosystems, an ultrathin PDDA layer functions as an intermediate charge transport mediator to relay the directional electron transfer from TMC NSs to MQDs that serve as the ultimate electron traps, resulting in a considerably boosted charge separation/migration efficiency. The suitable energy level alignment between TMC NSs and MQDs, concurrent electron-withdrawing capabilities of the ultrathin PDDA interim layer and MQDs, and the charge transport cascade endow the self-assembled TMC/PDDA/MQD heterostructured photosystems with conspicuously improved photoactivities toward anaerobic selective reduction of nitroaromatics to amino derivatives and photocatalytic hydrogen evolution under visible light irradiation. Furthermore, we ascertain that this concept of constructing a charge transfer cascade in such TMC-insulating polymer-MQD photosystems is universal. Our work would afford novel insights into smart design of spatial vectorial charge transport pathways by precise interface modulation via non-conjugated polymers for solar energy conversion.

Multilayer Conductive Hybrid Nanosheets as Versatile Hybridization Matrices for Optimizing the Defect Structure, Structural Ordering, and Energy-Functionality of Nanostructured Materials

The hybridization of conductive nanospecies has garnered significant research interest because of its high efficacy in improving the diverse functionalities of nanostructured materials. In this study, a novel synthetic strategy is developed to optimize the defect structure, structural ordering, and energy-related functionality of nanostructured-materials by employing a multilayer multicomponent two-dimenstional (2D) graphene/metal oxide/graphene nanosheet (NS) as a versatile hybridization matrix. The hybridization of the robust trilayer, polydiallyldiammonium (PDDA)-anchored reduced-graphene oxide (prGO)/metal oxide/prGO NS effectively enhance the structural ordering and porosity of the hybridized MoS₂ /MnO₂ NS through suppression of defect formation and tight stacking. In comparison with monolayer rGO/RuO₂ NS-based homologs, the 2D superlattice trilayer prGO/RuO₂ /prGO NS hybrids deliver better functionalities as a hydrogen evolution electrocatalyst and as a supercapacitor electrode, demonstrating the merits of hybridization with multilayer NSs. The advantages of using multilayer multicomponent conductive NSs as hybridization matrices arise from the enhancement of charge and mass transport through the layer flattening or defect suppression of the hybridized NSs and the increase in porosity, as evidenced by density functional theory calculations. Finally, the universal utility of multilayer NSs is confirmed by investigating the strong effect of the stacking order on the electrocatalytic functionality of MoS₂ /rGO/RuO₂ films fabricated through layer-by-layer deposition.

Au nanoclusters-decorated WO3 nanorods for ultrasensitive photoelectrochemical sensing of Hg2+

Ultrasensitive photoelectrochemical sensing of Hg2+ is achieved using Au nanocluster-decorated WO3 nanorods as photoactive materials.

Significant Aggregation-Enhanced Carrier Separation in Nanoscopic Catalysts Heterojunction Stacks

Nanoscopic heterojunction stacks are prevalent in nature as well as in artificial material systems, such as the nanoscopically blended components in soil or artificial catalytic layers on device surfaces. Despite the enormous attention placed on studying individual heterojunctions, the advantageous catalytic performance of heterojunction aggregates has not been recognized. In this study, we employ the ordered N-doped TiO₂ nanosheets and Au nanoparticle heterojunction multilayers obtained by a layer-by-layer technique to investigate the functional merits stemmed from heterojunction aggregates. The study demonstrates that nanoscopic heterojunction stacks promote the internal electric field that stemmed from charge separation and boost carrier separations. The aggregate-enhanced carrier separation can be harnessed in chemical conversions. The enhancement effect is influenced by both the dimensions of the entire aggregates as well as the dimensions of the nanoscopic building units. We expect the study to promote the understanding of heterojunction catalysts and corresponding matter conversion from the individual particulate level to the nanoscopic aggregate level and facilitate better harnessing of the photovoltaic effects or catalytic power in nanoscopic heterojunction aggregates.

The ligand effect of atomically precise gold nanoclusters in tailoring catalytic properties

It is well known that surface ligands are vital layers for ligand-protected Au_n nanoclusters. Improving the knowledge of the relationship between ligands and catalytic properties is a forefront research topic for Au_n nanoclusters. Enormous effort has been devoted to realizing the ligand effect in synthesis, including well-controlled sizes and shapes as well as structural transformation. However, the crucial function of surface ligands has not been addressed yet in catalytic reactions. Here, this review mainly aims to summarize the recent progress concerning the influence of surface ligand layers on catalytic activity and selectivity, based on the various types of ligand protected Au_n nanoclusters. Besides, the potential challenges and opportunities of Au_n nanoclusters are indicated, mainly in terms of surface ligands to guide the improvement of catalytic performances.