Nonconjugated Polymers Enabled Solar Water Oxidation.

Wholly distinct from conjugated polymers which are featured by generic charge transfer capability stemming from a conjugated molecular structure, solid nonconjugated polymers mediated charge transport has long been deemed as theoretically impossible because of the deficiency of π electrons along the molecular skeleton, thereby retarding their widespread applications in solar energy conversion. Herein, we first conceptually unveil that intact encapsulation of metal oxides (e.g., TiO2, WO3, Fe2O3, and ZnO) with an ultrathin nonconjugated polyelectrolyte of branched polyethylenimine (BPEI) can unexpectedly accelerate the unidirectional charge transfer to the active sites and foster the defect generation, which contributes to the boosted charge separation and prolonged charge lifetime, ultimately resulting in considerably improved photoelectrochemical (PEC) water oxidation activities. The interfacial charge transport origins endowed by BPEI adornment are elucidated, which include acting as a hole-withdrawing mediator, promoting vacancy generation, and stimulating the directional charge flow route. We additionally ascertain that such charge transport characteristics of BPEI are universal. This work would unlock the charge transfer capability of nonconjugated polymers for solar water oxidation. The nonconjugated insulating polymer was utilized as a charge transport mediator for boosting charge migration and separation over metal oxides toward solar water oxidation.

Simultaneous Photocatalytic Tetracycline Oxidation and Cr(VI) Reduction by Z-Scheme Multiple Layer TiO2/SnIn4S8.

Wastewater pollutants are a major threat to natural resources, with antibiotics and heavy metals being common water contaminants. By harnessing clean, renewable solar energy, photocatalysis facilitates the synergistic removal of heavy metals and antibiotics. In this paper, MXene was both a template and raw material, and MXene-derived oxide (TiO2) and SnIn4S8 Z-scheme composite materials were synthesized and characterized. The synergistic mode of photocatalytic reduction and oxidation leads to the enhanced utilization of e-/h+ pairs. The TiO2/SnIn4S8 exhibited a higher photocatalytic capacity for the simultaneous removal of tetracycline (TC) (20 mg·L-1) and Cr(VI) (15 mg·L-1). The main active substances of TC degradation and Cr(VI) reduction were identified via free radical scavengers and electron paramagnetic resonance (EPR). Additionally, the potential photocatalytic degradation route of TC was thoroughly elucidated through liquid chromatography-mass spectrometry (LC-MS).

Precise Layer-by-Layer Assembly of Dual Quantum Dots Artificial Photosystems Enabling Solar Water Oxidation.

Quantum dots (QDs) colloidal nanocrystals are attracting enduring interest by scientific communities for solar energy conversion due to generic physicochemical merits including substantial light absorption coefficient, quantum confinement effect, enriched catalytically active sites, and tunable electronic structure. However, photo-induced charge carriers of QDs suffer from ultra-short charge lifespan and poor stability, rendering controllable vectorial charge modulation and customizing robust and stable QDs artificial photosystems challenging. Herein, tailor-made oppositely charged transition metal chalcogenides quantum dots (TMCs QDs) and MXene quantum dots (MQDs) are judiciously harnessed as the building blocks for electrostatic layer-by-layer assembly buildup on the metal oxides (MOs) framework. In these exquisitely designed LbL assembles MOs/(TMCs QDs/MQDs)n heterostructured photoanodes, TMCs QDs layer acts as light-harvesting antennas, and MQDs layer serves as electron-capturing mediator to relay cascade electrons from TMCs QDs to the MOs substrate, thereby yielding the spatially ordered tandem charge transport chain and contributing to the significantly boosted charge separation over TMCs QDs and solar water oxidation efficiency of MOs/(TMCs QDs/MQDs)n photoanodes. The relationship between interface configuration and charge transfer characteristics is unambiguously unlocked, by which photoelectrochemical mechanism is elucidated. This work would provide inspiring ideas for precisely mediating interfacial charge transfer pathways over QDs toward solar energy conversion.

Customizing precise, tunable, and universal cascade charge transfer chains towards versatile photoredox catalysis.

The core factors dictating the photocatalysis efficiency are predominantly centered on controllable modulation of anisotropic spatial charge transfer/separation and regulating vectorial charge transport pathways. Nonetheless, the sluggish charge transport kinetics and incapacity of precisely tuning interfacial charge flow at the nanoscale level are still the primary dilemma. Herein, we conceptually demonstrate the elaborate design of a cascade charge transport chain over transition metal chalcogenide-insulating polymer-cocatalyst (TIC) photosystems via a progressive self-assembly strategy. The intermediate ultrathin non-conjugated insulating polymer layer, i.e., poly(diallyl-dimethylammonium chloride) (PDDA), functions as the interfacial electron relay medium, and simultaneously, outermost co-catalysts serve as the terminal "electron reservoirs", synergistically contributing to the charge transport cascade pathway and substantially boosting the interfacial charge separation. We found that the insulating polymer mediated unidirectional charge transfer cascade is universal for a large variety of metal or non-metal reducing co-catalysts (Au, Ag, Pt, Ni, Co, Cu, NiSe2, CoSe2, and CuSe). More intriguingly, such peculiar charge flow characteristics endow the self-assembled TIC photosystems with versatile visible-light-driven photoredox catalysis towards photocatalytic hydrogen generation, anaerobic selective organic transformation, and CO2-to-fuel conversion. Our work would provide new inspiration for smartly mediating spatial vectorial charge transport towards emerging solar energy conversion.

Crafting Insulating Polymer Mediated and Atomically Precise Metal Nanoclusters Photosensitized Photosystems Towards Solar Water Oxidization.

Atomically precise metal nanoclusters (NCs) have been deemed as a new generation of metal nanomaterials because of their characteristic atomic stacking fashion, quantum confinement effect, and multitude of active sites. The discrete molecular-like energy band structure of metal NCs endows them with photosensitization capability for light harvesting and conversion. However, applications of metal NCs in photoelectrocatalysis are limited by the ultrafast charge recombination and unfavorable stability, impeding the construction of metal NC-based photosystems. In this work, we elaborately crafted multilayered metal oxide (MO)/(metal NCs/insulating polymer)n photoanodes by a facile layer-by-layer (LbL) assembly technique. In these well-defined heterostructured photoanodes, glutathione (GSH)-wrapped metal NCs (Agx@GSH, Ag9@GSH6, Ag16@GSH9, and Ag31@GSH19) and an insulating poly(allylamine hydrochloride) (PAH) layer are alternately deposited on the MO substrate in a highly ordered integration mode. We found that photoelectrons of metal NCs can be tunneled into the MO substrate via the intermediate ultrathin insulating polymer layer by stimulating the tandem charge transfer route, thus facilitating charge separation and boosting photoelectrochemical water oxidation performances. Our work would open a new frontier for judiciously regulating directional charge transport over atomically precise metal NCs for solar-to-hydrogen conversion.

Layer-By-Layer Assembly of Atomically Precise Alloy Nanoclusters Photosystems for Solar Water Oxidation.

Atomically precise metal nanoclusters (NCs) have garnered tremendous attention as light-harvesting antennas in heterogeneous photocatalysis due to unique atomic stacking mode, quantum confinement effect, and enriched active sites. However, metal NCs as photosensitizers suffer from extremely short carrier lifetime, poor photostability, and difficulty in carrier migration, which hinder the wide-spread utilization of metal NCs in solar energy conversion. To solve these problems, herein, Ag-doped glutathione (GSH)-capped gold NCs, i.e., alloy Au1- x Agx @GSH NCs and non-conjugated insulating polymer of poly(diallyl-dimethylammonium chloride) (PDDA) are utilized as the building blocks for layer-by-layer assembly of spatially multilayered alloy NCs/metal oxide (MO) photosystems. The alternately deposited ultrathin PDDA layer in-between Au1- x Agx @GSH NCs on the MO substrate functions as an efficient charge flow mediator to relay the directional photoelectron transfer over Au1- x Agx @GSH NCs, giving rise to the cascade charge transfer chain. This peculiar carrier migration mode endowed by exquisite interface configuration design significantly boosts the unidirectional electron migration from the Au1- x Agx @GSH NCs to the MO substrate, substantially improving the visible-light-driven photoelectrochemical water oxidation performances of MO/(PDDA-Au1- x Agx )n multilayer heterostructured photoanodes. The work will inspire the rational construction of alloy metal NCs-based photosystems for modulating spatially controllable charge transfer pathway for solar energy conversion.

Solar CO2 Reduction Enabled by Cascade Hole Migration.

Solar-powered photocatalytic conversion of CO2 to hydrocarbon fuels represents an emerging approach to solving the greenhouse effect. However, low charge separation efficiency, deficiency of surface catalytic active sites, and sluggish charge-transfer kinetics, together with the complicated reaction pathway, concurrently hinder the CO2 reduction. Herein, we show the rational construction of transition metal chalcogenides (TMCs) heterostructure CO2 reduction photosystems, wherein the TMC substrate is tightly integrated with amorphous oxygen-containing cobalt sulfide (CoSOH) by a solid non-conjugated polymer, i.e., poly(vinyl alcohol) (PVA), to customize the unidirectional charge-transfer pathway. In this well-defined multilayered nanoarchitecture, the PVA interim layer intercalated between TMCs and CoSOH acts as a hole-relaying mediator and meanwhile boosts CO2 adsorption capacity, while CoSOH functions as a terminal hole-collecting reservoir, stimulating the charge transport kinetics and boosting the charge separation over TMCs. This peculiar interface configuration and charge transport characteristics endow TMC/PVA/CoSOH heterostructures with significantly enhanced visible-light-driven photoactivity and CO2 conversion. Based on the intermediates probed during the photocatalytic CO2 reduction reaction, the photocatalytic mechanism was determined. Our work would inspire sparkling ideas to mediate the charge transfer over semiconductor for solar carbon neutral conversion.

Atomically Precise Metal Nanocluster Photosystem: Electron Relay Boosts Photocatalytic Organic Transformation.

Atomically precise metal nanoclusters (NCs) demonstrate emerging potential as a new generation of photosensitizers in photoredox catalysis. However, metal NCs suffer from intrinsic poor instability, which leads to the loss of photosensitization effect and hampers their widespread applications in heterogeneous photocatalysis. Herein, we corroborate the design of a spatially directional charge transfer pathway over transition metal chalcogenide (TMC)-based heterostructures by way of a facile and efficient electrostatic self-assembly approach. Positively charged solid-state nonconjugated insulating polymer of poly(allylamine hydrochloride) (PAH) and negatively charged glutathione (GSH) capped metal NCs [Ag9@(GSH)6] as building blocks were controllably and highly ordered anchored on the TMC substrate. It was unveiled that owing to the appropriate energy level alignment and interface configuration, photogenerated electrons over metal NCs can directionally flow to the TMC substrate with the aid of PAH, which functions as an interfacial charge transfer mediator, and simultaneously holes migrate in the opposite direction, thereby collaboratively contributing to substantially boosted charge separation and prolonged charge lifetime. Benefiting from these merits, the thus self-assembled TMCs/PAH/metal NC heterostructure unfolds conspicuously enhanced photoactivity toward anaerobic selective photocatalytic reduction of nitroaromatics to amino derivatives under visible light irradiation. This work would significantly reinforce our fundamental understanding of the charge transfer characteristic of atomically precise metal NCs and the charge-withdrawing capability of solid insulating polymers for solar energy conversion.

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.

Maneuvering the Directional Charge Flow for Photoredox Organic Conversion.

Transition-metal chalcogenide quantum dots (TMC QDs) show great promise in artificial photosynthesis for excellent light-harvesting capability. Nonetheless, TMC QDs have limitations of ultrafast charge recombination rate, sluggish carrier migration kinetics, and generic photocorrosion, retarding their widespread applications. To solve these obstacles, herein, we demonstrate the stimulation of charge migration over TMC QDs with the aid of nonconjugated insulating polymer and graphene (GR) for a versatile photoredox selective organic transformation. To this end, an ultrathin insulating polymer layer, i.e., poly(allylamine hydrochloride) (PAH), grafted on the GR framework, is electrostatically intercalated at the interface of TMCs QDs and the GR framework via a self-assembly for constructing TMC QDs/PAH/GR three-dimensional spatially multilayered heterostructures. In this well-defined nanoarchitecture, TMC QDs function as a light-harvesting antenna, GR as a terminal electron reservoir, and PAH as an intermediate interfacial charge relay mediator. We ascertain that the ultrathin PAH interim layer unexpectedly fosters the photoelectron migration from TMCs QDs to the GR framework in a tunable fashion, boosting the charge separation of TMCs QDs and resulting in significantly improved photoactivities toward anaerobic reduction of aromatic nitro compounds to amino derivatives and oxidation of alcohols to aldehydes under visible light. Photoredox catalysis mechanisms of such TMC QDs/PAH/GR photosystems are elucidated, and the active species in these photoredox organic conversion reactions are comprehensively determined. Our work would open new frontiers to finely modulate the charge transport of TMCs QDs via nonconjugated insulating polymers for solar energy conversion.

Electron Tunneling Fosters Solar-to-Hydrogen Energy Conversion.

Transition-metal chalcogenide quantum dots (TMCs QDs) exhibit emerging potential in the field of solar energy conversion due to large absorption coefficients for light harvesting, quantum size effect, and abundant active sites. However, fine-tuning the photoinduced charge carrier over TMCs QDs to manipulate the directional charge-transfer pathway remains challenging, considering their ultrashort charge lifetime and slow charge-transfer kinetics. To this end, herein, MoSx/PDDA/TMCs QDs heterostructures were exquisitely designed by a simple and green electrostatic self-assembly strategy under ambient conditions, wherein tailor-made negatively charged TMCs QDs stabilized by mercaptoacetic acid (MAA) were precisely self-assembled on the positively charged polydiallyl dimethylammonium chloride (PDDA)-modified MoSx nanoflowers (NFs), forming a well-defined three-dimensional heterostructured nanoarchitecture. As an electron trapping agent, an MoSx NFs cocatalyst benefits the unidirectional electron transfer from TMCs QDs to the ideal active centers on the MoSx NFs surface by tunneling the ultrathin insulating polymer interim layer, thereby boosting the charge separation efficiency and endowing self-assembled MoSx/PDDA/TMCs QDs heterostructures with considerably increased photocatalytic hydrogen evolution activity (1.96 mmol·g-1·h-1) and admirable stability under visible light irradiation. Our work will provide new insights into smart regulation of directional charge transfer over TMCs QDs-based photosystems for solar energy conversion.

Solar-CO2 -to-Syngas Conversion Enabled by Precise Charge Transport Modulation.

The rational design of the directional charge transfer channel represents an important strategy to finely tune the charge migration and separation in photocatalytic CO2 -to-fuel conversion. Despite the progress made in crafting high-performance photocatalysts, developing elegant photosystems with precisely modulated interfacial charge transfer feature remains a grand challenge. Here, a facile one-pot method is developed to achieve in situ self-assembly of Pd nanocrystals (NYs) on the transition metal chalcogenide (TMC) substrate with the aid of a non-conjugated insulating polymer, i.e., branched polyethylenimine (bPEI), for photoreduction of CO2 to syngas (CO/H2 ). The generic reducing capability of the abundant amine groups grafted on the molecular backbone of bPEI fosters the homogeneous growth of Pd NYs on the TMC framework. Intriguingly, the self-assembled TMCs@bPEI@Pd heterostructure with bi-directional spatial charge transport pathways exhibit significantly boosted photoactivity toward CO2 -to-syngas conversion under visible light irradiation, wherein bPEI serves as an efficient hole transfer mediator, and simultaneously Pd NYs act as an electron-withdrawing modulator for accelerating spatially vectorial charge separation. Furthermore, in-depth understanding of the in situ formed intermediates during the CO2 photoreduction process are exquisitely probed. This work provides a quintessential paradigm for in situ construction of multi-component heterojunction photosystem for solar-to-fuel energy conversion.

Robust and Stable Atomically Precise Metal Nanoclusters Mediated Solar Water Splitting.

Atomically precise metal nanoclusters (NCs) represent an emerging sector of light-harvesting antennas by virtue of peculiar atomic stacking fashion, quantum confinement effect, and molecular-like discrete energy band structure. Nevertheless, precise control of charge carriers over metal NCs has yet to be achieved by the short carrier lifetime and intrinsic instability of metal NCs, which renders the complexity of metal NCs-based photosystems with photoredox mechanisms remaining elusive. Herein, fine tuning of charge migration over metal NCs is demonstrated by constructing directional charge transfer channels in multilayered heterostructure enabled by a facile layer-by-layer (LbL) assembly approach, wherein oppositely charged branched poly-ethylenimine (BPEI) and glutathione (GSH)-capped gold NCs [Aux NCs, Au25 (GSH)18 NCs] are alternately deposited on the metal oxide (MOs: TiO2 , WO3 , Fe2 O3 ) substrates. TheAux (Au25 ) NCs layer serves as light-harvesting antennas for engendering charge carriers, andBPEI interim layer uniformly intercalated at the interface of Aux NCs layer constitutes the tandem hole transport channel for motivating the charge transfer cascade, resulting in the considerably enhanced photoelectrochemical water oxidation performances. Besides, poor photo-stability of Aux NCs is surmounted by stimulating the hole transfer kinetics process.

Photosensitization Efficiency Modulation of Atomically Precise Silver Nanoclusters for Photoelectrocatalysis.

Atomically precise metal nanoclusters (NCs) have emerged as feasible alternatives to traditional photosensitizers in solar energy conversion due to the unique atomic stacking mode, quantum size effect, and abundant active sites. Despite the sporadic advancement in fabricating metal NC-based photosystems, most of which are predominantly centered on Au NCs, unleashing atomically precise silver nanoclusters as light-harvesting antennas has still been in the infant stage, with the charge transfer mechanism remaining elusive. Herein, we comprehensively demonstrate the photosensitization effect of Ag NCs in the photoelectrochemical (PEC) water-splitting reaction and strictly evaluate the correlation of photosensitization efficiency with atomic architecture. To these ends, tailor-made negatively charged l-glutathione (GSH)-capped Ag NCs [Agx, Ag9(GSH)6, Ag16(GSH)9, Ag31(GSH)19] as building blocks are controllably deposited on the metal oxide (MOs = TiO2, WO3, Fe2O3) substrate by a facile self-assembly strategy. Benefiting from the highly efficient photosensitization effect of atomically precise Ag NCs, these self-assembled MOs/Ag NC heterostructured photoanodes with an elegant charge transfer interface demonstrate significantly enhanced photoelectrochemical water oxidation performances under visible-light irradiation on account of efficient charge transport from Ag NCs to the MO substrate, substantially prolonging the charge lifetime of Ag NCs. Our work would significantly inspire ongoing interest in unlocking the generic photosensitization capability of atomically precise metal NCs for solar energy conversion.

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 Aux 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.

Atomically Precise Metal Nanoclusters versus Metal Nanocrystals: Maneuvering Tunable Charge Transfer in an Integrated Photosystem.

Atomically precise metal nanoclusters (NCs) have recently emerged as a promising sector of metal nanomaterials in terms of peculiar atomic stacking fashion, quantum confinement effect, and enriched catalytically active sites, which are wholly distinct from conventional metal nanocrystals (NYs) in all respects. However, atomically precise metal NCs inevitably suffer from intrinsic poor instability either under light irradiation or thermal treatment owing to the ultrahigh surface energy, thereby resulting in substantial loss of photosensitization efficiency and retarding their emerging utilization in photoredox catalysis. Here, we first conceptually reveal the charge transfer characteristic difference between atomically precise metal NCs and metal NYs attained by self-transformation in boosting interfacial charge migration and separation. The results signify that the interfacial charge transfer impetus of atomically precise metal NCs as a photosensitizer versus metal NYs as a Schottky-type electron-withdrawing mediator is closely associated with the loading amount on the semiconductor substrate. The photosensitization effect of atomically precise metal NCs is superior to the electron trapping capability of metal NYs when the loading amount of the metal ingredient is relatively high and vice versa. Our work would significantly bridge the gap between atomically precise metal NCs and metal NYs in fine tuning of the charge transfer pathway in photocatalysis toward solar energy conversion.

Steering Photocatalytic CO2 Conversion over CsPbBr3 Perovskite Nanocrystals by Coupling with Transition-Metal Chalcogenides.

Transition-metal chalcogenides (TMCs) have received enormous attention by virtue of their large light absorption coefficient, abundant catalytically active sites, and markedly reduced spatially vectorial charge-transfer distance originating from generic structural merits. However, the controllable construction of TMC-based heterostructured photosystems for photocatalytic carbon dioxide (CO2) reduction is retarded by the ultrashort charge lifetime, sluggish charge-transfer kinetics, and low target product selectivity. Herein, we present the rational design of two-dimensional (2D)/zero-dimensional (0D) heterostructured CO2 reduction photosystems by an electrostatic self-assembly strategy, which is enabled by precisely anchoring CsPbBr3 quantum dots (QDs) on the 2D TMC (CdIn2S4, ZnIn2S4, In2S3) frameworks. The peculiar 2D/0D integration mode and suitable energy-level alignment between these two assembly units afford maximal interfacial contact and applicable potential for CO2 photoreduction, thus endowing the self-assembled TMCs/CsPbBr3 nanocomposites with considerably improved visible-light-driven photocatalytic performances toward CO2 reduction to carbon monoxide with high selectivity. The enhanced photocatalytic performances of TMCs/CsPbBr3 heterostructures are attributed to the abundant active sites on the TMC frameworks, excellent light absorption of CsPbBr3 QDs, and well-defined 2D/0D heterostructures of TMCs/CsPbBr3 QDs photosystems, which synergistically boosts the directional charge transport from CsPbBr3 QDs to TMCs, enhancing the interfacial charge migration/separation. Our work would inspire the construction of novel TMCs-involved photosystems for solar-to-fuel conversion.

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.

Precisely Modulating the Photosensitization Efficiency of Transition-Metal Chalcogenide Quantum Dots toward Solar Water Oxidation.

Precisely modulating the spatial charge migration/separation constitutes the central issue in dictating the solar conversion efficiency of photoelectrochemical (PEC) cells, whereas it still remains a grand challenge. Here, we conceptually demonstrate the construction of hierarchically ordered metal oxide (MO)/transition-metal chalcogenide quantum dots (TMC QDs) multilayered heterostructured photoanodes, that is, MO/[TMC QDs(+)/TMC QDs(-)]n (TMC QDs: CdTe, CdSe, CdS), by a simple and general bottom-up self-assembly route. Tailor-made intrinsically oppositely charged TMC QDs are alternately deposited on the highly ordered MO via a generic ligand-triggered electrostatic interaction to craft heterostructured photoanodes. The charge-transfer pathway stimulated by the photosensitization of TMC QDs is finely tuned by the assembly sequence. The advantageous multilayered nanoarchitecture renders the MO/[TMC QDs(+)/TMC QDs(-)]n photoanodes exhibit substantially enhanced PEC performances under light irradiation, owing to the applicable energy-level configuration and peculiar combination fashion between building blocks and considerably boosted interfacial charge separation resulting from generating spatial tandem charge transport. Furthermore, photosensitization efficiency comparison among TMC QDs is comprehensively performed with PEC mechanisms elucidated.

4-1BBL Promoted the Proliferation and Migration of Human Gastric Cancer Cells through Wnt/p-catenin Signaling Pathway / 中国生物化学与分子生物学报

4-IBB and 4-IBB ligand (4-1BBL) , also known as CI) 137 and CD 137 ligand, are members of tumor necrosis factor (TNF) receptor and ligand family, respectively.The interaction of 4-1BBL and 4-IBB can activate T cell immune response.Therefore, 4-1BBL has been playing a role as a classical costimulatory molecule involving in anti-tumor immune responses.In recent decades, it was reported that 4-1BBL had multiple functions in tumor cells.However, the molecular mechanism of 4-1BBL in the progression of gastric cancer (GC) remains unclear.This study investigated the biological function and molecular mechanism of 4-1BBL in human GC cells.First, analysis from TCGA and Kaplan Meier plotter databases showed that 4-1BBL expression level in GC tissues was significantly higher than that in adjacent tissues (P<0.001) , and 4-1BBL high expression was positively associated with poor prognosis of GC (P<0.05).Knockout of 4-1BBL significantly inhibited the proliferation (P<0.05) , invasion and migration of GC cells (P<0.05 ) , and increased the apoptosis of GC cells (P<0.05).Western blot showed that 4- 1 BBL knockout decreased the protein expression levels of (3-catenin, c-Myc and Cyclin D1, and blocked Wnt/p-catenin signaling pathway.On the contrary, 4-1 BBL overexpression significantly promoted the proliferation (P<0.05) , invasion and migration of GC cells (P<0.05) , and reduced the apoptosis of GC cells (P<0.05).Moreover, 4-1 BBL overexpression increased the protein expression levels of (3- catenin, c-Myc and Cyclin D1, and activated Wnt/p-catenin signaling pathway.In summary, 4-1 BBL promoted the proliferation and migration of human GC cells through Wnt/(B-catenin signaling pathway.