Electrostatic Self-assembly Approach Research Articles

Origin of the Improved Photoelectrochemical and Photocatalytic Activity in a ZnO-TiO2 Nanohybrid Revealed by Experimental and Density Functional Theory Studies.

Heterojunctions of metal oxides have attracted a great deal of attention as photo (electro) catalysts owing to their excellent photoactivity. While multiple fundamental studies have been dedicated to heteroaggregation, self-assembly of oppositely charged particles to obtain heterojunctions for energy applications has been underexplored. Herein, we report the synthesis of ZnO-TiO2 heterojunctions using the electrostatic self-assembly approach. The synthesized ZnO-TiO2 heterojunctions were characterized by using multiple experimental techniques. Density functional theory calculations were conducted to establish the heterojunction formation mechanism and electronic properties. The ZnO-TiO2 nanohybrid was tested for the photodegradation of rhodamine B dye and water splitting applications. The photocatalytic performance of the ZnO-TiO2 nanohybrid is 3.5 times higher than that of bare ZnO. In addition, the heterostructure exhibited an excellent photocurrent density of 2.4 mA cm-2 at a low onset potential during photoelectrochemical oxygen evolution. The performance improvements are attributed to the formation of the type II heterojunction between ZnO and TiO2, which suppresses carrier recombination and enhances carrier transport, boosting the catalytic activity.

High-performance cellulose nanofibers-based actuators with multi-stimulus responses and energy storage

Smart actuating materials have received tremendous attention due to their promising applications in miniaturized robots, integrated electronics and wearable devices. However, simultaneously achieving sensitive multi-stimuli responsiveness, preferable energy storage capability and adequate mechanical properties by one material in a simple yet efficient way remains a considerable challenge. Herein, we propose a novel multi-responsive nanocomposite film actuator consisting of negatively charged cellulose nanofibers (CNF), polydopamine-chelated MXene-Fe3O4 nanohybrids (PMF) and positively charged carbon nanotubes (CCNT) via a cost-efficient electrostatic self-assembly approach. Benefiting from the laminated porous structure and compositional superiorities, including the water-induced swelling effect of CNF and PMF, conductive CCNT with countless interior hydrophobic channels and magneto-conductive properties of PMF, the optimized nanocomposite film actuator presents a high bending speed (100.5°/s), ultrashort actuation time (2.0 s), long-term stability (1005 cycles) and good magnetic response. These actuators can be assembled into a supercapacitor exhibiting an areal capacitance of 33.5 mF/cm2 at 0.5 mA/cm2 and good cycling stability with a capacitance retention of 80.5 % after 5000 cycles. Furthermore, the actuators are designed as soft robots with different motion modes, mechanical grippers for performing consecutive actions and an integrated circuit system to monitor surrounding humidity changes. This work provides inspiration to develop advanced nanocomposite materials for smart devices that require multifunction integration.

Crustacean-inspired chitin-based flexible buffer layer with a helical cross-linked network for bamboo fiber/poly(3-hydroxybutyrate) biocomposites

Marine biological resources, serving as a renewable and sustainable reservoir, holds significant import for the utilization of composite material. Hence, we produced bamboo fiber/poly(3-hydroxybutyrate) (BF/PHB) biocomposites with exceptional performance and economic viability, drawing inspiration from the resilience of crustacean shells. Polyaminoethyl modified chitin (PAECT) was synthesized using the alkali freeze-thaw method and introduced into the interface between BF and PHB to improve interfacial adhesion. The resulting chitin fibers, characterized by their intertwined helical chains, constructed a flexible mesh structure on the BF surface through an electrostatic self-assembly approach. The interwoven PAECT filaments infiltrated the dual-phase structure, acting as a promoter of interfacial compatibility, while the flexible chitin network provided a greater capacity for deformation accommodation. Consequently, both impact and tensile strength of the BF/PHB composites were notably enhanced. Additionally, this flexible layer ameliorated the thermal stability and crystalline properties of the composites. This investigation aimed to leverage the distinctive helical configuration of chitin to facilitate the advancement of bio-reinforced composites.

Synergized N and P co-doped Ti3C2Tx mxene enabling high-performance Li-air batteries

Lithium-oxygen batteries (LOBs) with a theoretical energy density of up to 3500 Wh kg−1 hold a promise for the next-generation high-energy-density batteries. However, the slow oxygen reduction/evolution kinetics at the cathode limits the performance of Li-air batteries. The rational design of efficient catalysts is essential for the improvement of oxygen electrode reaction kinetics. Herein, we report a facile strategy to co-dope N and P atoms simultaneously into Ti3C2Tx (NP-Ti3C2Tx) MXene via an electrostatic self-assembly approach. The co-doped NP-Ti3C2Tx layers expose abundant active sites, providing more space for accommodating the formed Li2O2. Moreover, the N and P co-doping facilitates efficient electron transport in Ti3C2Tx MXene. The LOB with NP-Ti3C2TX catalyst delivers a high discharge capacity of 24,940 mAh/g at 1000 mA g−1. At a cut-off capacity of 1000 mAh/g, this battery runs continuously for 159, 276, 185, and 229 cycles at current densities of 1000, 2000, 3000, and 5000 mA g−1, respectively. Theoretical calculations unveil that N and P co-doping enables lower ηORR and ηOER of only 0.26 V and 0.13 V on Ti3C2Tx MXene, respectively. This work offers a feasible approach for constructing efficient MXene electrocatalysts for Li–air batteries.

Ambient synthesis of one-dimensional core-shell nanocomposites by encapsulating SiC nanowires with layered double hydroxide nanosheets for high-performance microwave absorption application

The optimization design of micro/nanostructure and composition is an effective strategy for preparing high-performance electromagnetic wave absorption (EMA) material. Here, we provide a single-step in-situ electrostatic self-assembly growth approach at room temperature for the efficient construction of core-shell structural composites, consisting of bimetallic layered double hydroxides (LDH) nanosheets tightly wrapped around SiC nanowires. The formation of the bimetallic LDH nanosheets shell is caused by the binding of the bimetallic cations to OH−, which mainly arises from the hydrolysis of water induced by the 2-methylimidazole molecule, while the protonated 2-methylimidazole acts as an interlayer equilibrium anion. Through a heat-treatment process under air, the resulting derivatives of Co, Ni-LMc@SiC, and Zn, Ni-LMc@SiC generate excellent EMA properties due to the intrinsic and synergistic properties of the dielectric/magnetic components and the core-shell structure that provides numerous physical contacts and endows the composite with enhanced interfacial polarization and electron transport. As a result, Zn, Ni-LMc@SiC displays the highest RLmin value of −55.59 dB at 2.8 mm and EABmax of 6.28 at 2.4 mm, while Co, Ni-LMc@SiC has the widest EAB of 6.32 GHz at a thinner thickness of 2.2 mm. The successful construction of core-shell structures for LDH and SiC nanowires in such a facile strategy will broaden the application and development of high-performance EMA materials.

Hollow CuS nanoparticles equipped with hydroxyapatite/hyaluronic acid coating for NIR/pH dual-responsive drug delivery

The near-infrared (NIR)/pH dual-responsive nanoplatform shows great potential in remote photothermal therapy for tumor on account of the near-infrared window in biological tissue and the mild acidic environment in tumor cells. CuS nanoplatform has become a rising star in the field of photothermal agents due to its excellent NIR responsiveness and photostability. In this work, hollow CuS nanoparticles with high photothermal conversion efficiency (42.42 %) were synthesized through a novel surfactant micelle-assisted method. Then, CuS@hydroxyapatite (HAP)/hyaluronic acid (HA) nanoclusters with controllable drug release property were prepared by capping HAP and HA on the surface of CuS via electrostatic self-assembly approach. The hollow structure of CuS and the large specific surface area of HAP ensure an outstanding doxorubicin hydrochloride (DOX) loading efficiency of 99.2 % in CuS@HAP/HA nanoclusters. The introduction of HA effectively retards the initial burst release of DOX and ensures the excellent biocompatibility of nanoclusters. More importantly, CuS@HAP/HA displays distinct NIR/pH dual-responsive drug release properties owing to the excellent NIR responsiveness of hollow CuS and the gradual dissolution of HAP under acidic conditions. This work provides an environmentally benign method to prepare CuS-based nanoclusters with excellent NIR/pH responsive drug delivery properties, which has great potential in remote photothermal therapy.

G-C3 N4 @ZnONP electrostatic self-assembly: Enhanced ROS as a key factor for high-efficiency control of tobacco wildfire disease.

The utilization of nonmetallic inorganic nanomaterials for antimicrobial photocatalytic technology has emerged as a promising approach to combat drug-resistant bacteria. Recently, g-C3 N4 nanosheets have attracted significant attention due to their exceptional stability, degradability, low cost, and remarkable antibacterial properties. In this study, a facile electrostatic self-assembly approach was utilized to functionalize ZnO nanoparticles with g-C3 N4 nanosheets, resulting in the formation of g-C3 N4 @ZnO nanoparticle composites. The Z-shaped heterojunction architecture of these composites facilitates efficient separation of photogenerated electron-hole pairs and enhances visible light catalytic performance. Moreover, the formation of the g-C3 N4 @ZnO heterostructure showed a higher photocatalytic capacity and the generation of reactive oxygen species than g-C3 N4 nanosheets. The photocatalytic antibacterial mechanisms of g-C3 N4 @ZnO at the transcriptomic level primarily involve disrupting bacterial membrane synthesis and inhibiting motility and energy metabolism. Therefore, the antibacterial mechanism of g-C3 N4 @ZnO can be attributed to a combination of physical membrane damage, chemical damage (ROS enhancement) and inhibition of chemotaxis, biofilm formation and flagellar motility. These findings collectively provide novel high potential and insights into the practical application of photocatalysts in plant disease management. This article is protected by copyright. All rights reserved.

Bifunctional electrochemical biosensor based on PB-MXene films for the real-time analysis and detection of living cancer cells

Circulating tumor cells (CTCs) are important prognostic markers for cancer diagnosis and metastasis, and their detection is an important means to detect cancer metastasis. Herein, we construct a novel bifunctional electrochemical biosensor based on the PB-MXene composite films. A simple electrostatic self-assembly approach was employed to prepare a film composed of PB nanocubes on the MXene substrates. Given that the PB is an artificial peroxidase for H2O2 sensing, the PB-MXene films can realize the real-time monitoring of H2O2 secretion from living CTCs. Besides, the anti-CEA attached biosensors can be utilized to quantify the corresponding CTCs. The synergic effects of the MXene with a large specific area and PB with enzyme-free catalysis for H2O2 resulted in PB-MXene films exhibiting high electrocatalytic and low cytotoxicity for both H2O2 sensing and living CTCs capturing. As a result, the biosensor shows a low detection limit of 0.57 μM towards H2O2 with a wide linear range (1 μM to 500 μM), as well as an excellent sensing performance for CTCs (an extremely low detection limit of 9 cells/mL in a wide linear range of 1.3 ×101 to 1.3 ×106 cells/mL). Moreover, the prepared biosensor showed satisfactory stability and anti-interference ability for potential applications in clinical cancer diagnosis and tumor metastasis.

A Lead-Free 0D/2D Cs3Bi2Br9/Bi2WO6 S-Scheme Heterojunction for Efficient Photoreduction of CO2.

Photocatalytic reduction of CO2 into valuable hydrocarbon fuels is one of the green ways to solve the energy problem and achieve carbon neutrality. Exploring photocatalyst with low toxicity and high-efficiency is the key to realize it. Here we report a lead-free halide perovskite-based 0D/2D Cs3Bi2Br9/Bi2WO6 (CBB/BWO) S-scheme heterojunction for CO2 photoreduction, prepared by a facile electrostatic self-assembly approach. The CBB/BWO shows superior photoreduction of CO2 under visible light with CO generation rate of 220.1 μmol·g-1·h-1, which is ∼115.8 and ∼18.5 times higher than that of Cs3Bi2Br9 perovskite quantum dots (CBB PQDS) and Bi2WO6 nanosheets (BWO NS), respectively. The improved photocatalytic activity can be attributed to the tight 0D/2D structure and S-scheme charge transfer pathway between the Cs3Bi2Br9 PQDS and atomic layers of the Bi2WO6 NS, which shortens transmission distance of photogenerated carriers and boosts efficient separation and transfer of the carriers. This work provides insight in manufacturing potential lead-free perovskite-based photocatalysts for achieving carbon neutrality.

Honeycomb graphene–polyaniline nanocomposites as novel electrode materials for high-performance supercapacitors

Honeycomb graphene–polyaniline (HG–PANI) nanocomposites are synthesized through a facile electrostatic self-assembly approach, and the obtained material is characterized as the electrode for supercapacitor applications.

Highly Performant Electromagnetic Absorption at the X Band Based on Co@NCS/Ti3C2Tx Composites

Electromagnetic waves at the X band (8.2-12.4 GHz) play significant roles in military applications such as radar, satellite, and wireless communication. However, within this band range, the developed performance of electromagnetic absorption (EMA) is still unsatisfied, and it is hard to settle the corresponding problems on radar stealth and electromagnetic pollution. Herein, we demonstrate a state-of-the-art EMA property of -82.6 dB at 8.24 GHz with 2.57 mm thickness and 30 wt % paraffin filling ratio. For this purpose, an optimal Co@NCS/Ti3C2Tx composite is prepared by an electrostatic self-assembly approach through compelling Co-loading of nitrogen-doped carbon sheets (Co@NCS) derived from the pyrolysis of ZIF-67 (CoZn) with 2D Ti3C2Tx MXene nanosheets. Experimental results show that the highly efficient EMA performance of this Co@NCS/Ti3C2Tx composite originates from the large surface area for multiple reflection and electromagnetic wave scattering, from abundant defects sites for dipole and interfacial polarization, and from the optimizing impedance matching by the combination of Co magnetic nanoparticles and conductive NCS/Ti3C2Tx composite. These results confirm that the as-fabricated composites possess scientific and practical values for EMA applications at the X band, paving the way for developing highly performant electromagnetic absorbers toward specific microwave bands.

Visible light active hybrid silver decorated g-C3N4–CeO2 nanocomposite for ultrafast photocatalytic activity and toxicity evaluation

Development of hybrid graphitic carbon nitride (GCN) nanocomposite is an emerging research area in wastewater treatment. Herein, hybrid visible light active photocatalyst of silver decorated polymeric graphitic carbon nitride and (Ag-GCN) with cerium oxide (CeO2) nanocomposite was prepared and characterized in detail. The Ag-GCN/CeO2 photocatalyst has successfully prepared by an electrostatic self-assembly approach. The synthesized Ag-GCN/CeO2 NCs photocatalysts are characterized by various physio-chemical techniques. Using the Ag-GCN/CeO2 catalyst, the excellent photodegradation efficiency of Acid yellow-36 (AY-36) and Direct yellow-12 (DY-12) dye solution were achieved 100% within 150 min sun light irradiation. The Ag-GCN/CeO2 rate constant values of 0.048 and 0.046/min has been determined for AY-36 and DR-12 dyes, respectively. The extraordinary photocatalytic activity is due to incorporation of CeO2 with Ag-GCN which play a significant role in visible light absorption, superior reactive oxygen generation (ROS) and excellent pollutant catalyst interaction. The toxicity of the photocatalytically degraded AY-36 and DR-12 dyes were measured using the soil nematode Caenorhabditis elegans, a well-established in vivo model in biology, by analyzing survival, physiological functions, intracellular ROS levels, and stress-protective gene expressions.

Promoting charge separation of 0D/2D CsPbBr3/Bi2WO6 Z-scheme heterojunctions for boosting photocatalytic N2 reduction

High efficient photocatalytic nitrogen fixation is an alternative strategy to solve the problems of energy consumption and environmental pollution of industrial ammonia production effectively, hence the selection and modification of catalysts are very important to improve the nitrogen fixation efficiency. In this article, a straightforward Z-scheme 0D/2D CsPbBr3/Bi2WO6 heterojunction was successfully constructed via a simple electrostatic self-assembly approach. By combining CsPbBr3 quantum dots (CPB QDs) with ultrathin Bi2WO6 (BWO) nanosheets, a large-area heterointerface of CPB QDs and BWO nanosheets was connected tightly thus shortened the charge transport distance effectively. This facilitates the efficient charge transfer between CPB and BWO through the Z-scheme interface, thereby achieving the purpose of promoting charge separation, which is well validated in differential charge. On the basis of various characterizations, the results indicated that the CPB/BWO heterojunction possessed an excellent photocatalytic nitrogen fixation performance: the production of NH3 at 3CPB/BWO heterojunctions (126.3 μmol‧g−1‧h−1) was about 17.1 times higher than that of pure CPB QDs. The new strategy may offer a new opportunity to the exploration and the research of halide perovskite-type photo catalysts with obviously enhanced nitrogen fixation activities.

Polypyrrole/SnCl2 modified bacterial cellulose electrodes with high areal capacitance for flexible supercapacitors

Polypyrrole (PPy)/bacterial cellulose (BC) composite membranes are a promising kind of lightweight and flexible electrodes for supercapacitors. Herein, we explored a facile and efficient electrostatic self-assembly approach to uniformly depositing anion-doped PPy onto positively charged SnCl2-modifed BC (SBC). The obtained PPy@SBC electrode exhibited a high areal capacitance of 5718 mF cm−2 at a current density of 0.5 mA cm−2, a desirable capacitance retention of 83.1% at 5.0 mA cm−2 and excellent cycling stability (a capacitance retention of 86.8% after 10,000 cycles at 10 mA cm−2). A symmetric flexible supercapacitor was further assembled with the PPy@SBC electrodes, which delivered outstanding mechanical flexibility with negligible capacitance decay under different bent states. This study shows impressive potential in fabricating high-performance electrodes for flexible supercapacitors.

An electrostatic self-assembly approach to prepare tebuconazole nanoparticles with improved sustained release and enhanced antifungal activity

Compared with the traditional pesticides, the nanopesticides (NPs) exhibit better sustained release performance, higher utilization efficiency and reduction of environmental pollution. In this study, the antifungal tebuconazole (TEB) loaded nanoparticles (TEB NPs) were prepared by electrostatic self-assembly of the positively charged poly dimethyl diallyl ammonium chloride (PDADMAC) and sulfobutylether-β-cyclodextrin (SCD) inclusion complex (TEB-SCD) with negative charge. The water solubility and thermal stability of TEB were significantly improved after forming the inclusion complex. The blank NPs and TEB NPs were both characterized by particle size, zeta potential, scanning electron microscopy (SEM), sustained release and antifungal activity. The average particle size of the TEB NPs were 411.75 ± 61.65 nm, and the polydispersity index (PDI) showed low values (< 0.3). The TEB NPs were stable for at least 28 days at 25 °C. Compared with pure TEB, TEB NPs showed the sustained release properties. In addition, TEB NPs exhibited better antifungal activity than TEB industrial concentrate (TC, 98%) and commercially available TEB suspension concentrate (SC) with the 96.33 ± 13.52% antifungal rate of fusarium graminearum. The results indicated that the TEB NPs can improve the antifungal activity and reduce environmental pollution.

Electrostatic self-assembly approach in the deposition of bio-functional chitosan-based layers enriched with caffeic acid on Ti-6Al-7Nb alloys by alternate immersion.

Tailoring surface properties by layer-by-layer (LBL) deposition directed on the construction of complex multilayer coatings with nanoscale precision enables the development of novel structures and devices with desired functional properties (i.e., osseointegration, bactericidal activity, biocorrosion protection). Herein, electrostatic self-assembly was applied to fabricate biopolymer-based coatings involving chitosan (CSM) and alginate (AL) enriched with caffeic acid (CA) on Ti-6Al-7Nb alloyed surfaces. The method of CA grafting onto the chitosan backbone (CA-g-CSM) as well as all used reagents for implant functionalization were chosen as green and sustainable approach. The final procedure of surface modification of the Ti-6Al-7Nb alloy consists of three steps: (i) chemical treatment in Piranha solution, (ii) plasma chemical-activation of the Ti alloy surface in a RF CVD (Radio Frequency Chemical Vapour Deposition) reactor using Ar, O2 and NH3 gaseous precursors, and (iii) a multi-step deposition of bio-functional coatings via dip-coating method. Corrosion tests have revealed that the resulting chitosan-based coatings, also these involving CA, block the specimen surface and hinder corrosion of titanium alloy. Furthermore, the antioxidant layers are characterized by beneficial level of roughness (Ra up ca. 350nm) and moderate hydrophilicity (59°) with the dispersion part of conducive surface energy ca. 30mJ/m2. Noteworthy, all coatings are biocompatible as the intact morphology of cultured eukaryotic cells ensured proper growth and proliferation, while exhibit bacteriostatic character, particularly in contact with Gram-(-) bacteria (E. coli). The study indicates that the applied simple sustainable strategy has contributed significantly to obtaining homogeneous, stable, and biocompatible while antibacterial biopolymer-based coatings.

Synchronous Manipulation of Ion and Electron Transfer in Wadsley-Roth Phase Ti-Nb Oxides for Fast-Charging Lithium-Ion Batteries.

Implementing fast‐charging lithium‐ion batteries (LIBs) is severely hindered by the issues of Li plating and poor rate capability for conventional graphite anode. Wadsley–Roth phase TiNb2O7 is regarded as a promising anode candidate to satisfy the requirements of fast‐charging LIBs. However, the unsatisfactory electrochemical kinetics resulting from sluggish ion and electron transfer still limit its wide applications. Herein, an effective strategy is proposed to synchronously improve the ion and electron transfer of TiNb2O7 by incorporation of oxygen vacancy and N‐doped graphene matrix (TNO− x @N‐G), which is designed by combination of solution‐combustion and electrostatic self‐assembly approach. Theoretical calculations demonstrate that Li+ intercalation gives rise to the semi‐metallic characteristics of lithiated phases (Li y TNO− x ), leading to the self‐accelerated electron transport. Moreover, in situ X‐ray diffraction and Raman measurements reveal the highly reversible structural evolution of the TNO− x @N‐G during cycling. Consequently, the TNO− x @N‐G delivers a higher reversible capacity of 199.0 mAh g−1 and a higher capacity retention of 86.5% than those of pristine TNO (155.8 mAh g−1, 59.4%) at 10 C after 2000 cycles. Importantly, various electrochemical devices including lithium‐ion full battery and hybrid lithium‐ion capacitor by using the TNO− x @N‐G anode exhibit excellent rate capability and cycling stability, verifying its potential in practical applications.

Bismuth Vanadate Encapsulated with Reduced Graphene Oxide: A Nanocomposite for Optimized Photocatalytic Hydrogen Peroxide Generation

The photocatalytic H2O2 production is a sustainable and eco-friendly process. Bismuth vanadate (BiVO4 or BVO) is a promising photocatalyst with a low band gap energy. Reduced graphene oxide (rGO) is known for promoting the transport of charges and preventing the recombination of photogenerated electron–hole pairs. This study proposes a synthesis method based on an electrostatic self-assembly approach for functionalizing BVO with GO for photocatalytic H2O2 generation. Different amounts of GO loading on BVO have been taken to assess and optimize the quality of xrGO–BVO (where x = 0.5, 1, 2, and 4 wt %) composites for effective H2O2 generation. H2O2 shows stability under acidic conditions; hence, the effectivity of the xrGO–BVO was tested using acids with different strengths. 1rGO–BVO exhibited efficient H2O2 generation in the presence of oxalic acid, promoting two-electron O2 reduction reaction with a good cyclic stability. A photocatalytic flow reactor study has also been presented to assess the feasibility of continuous H2O2 generation.

Electrostatic Self-Assembly Approach to Fabricate Architectures of Carboxyl Functionalized Gold-Aryl Nanoparticles and Graphene Oxide Platforms

Graphene oxide (GO) was decorated with gold-aryl (Au-C) nanoparticles AuNPs-COOH by sodium borohydride reduction of aryldiazonium tetrachloroaurate(III) salt at room temperature in aqueous solutions. Brunauer-Emmett-Teller measurements supported GO anchoring by AuNPs modified with COOH; surface area dropped significantly. Morphology of AuNPs-COOH/GO nanocomposite (NC) was probed using AFM and TEM, showing NC’s surface roughness and wrinkling. XPS results suggest the clear reductive reaction of tetrachloroaurate anion into metallic gold in AuNPs-COOH/GO along with detailed interpretations of functional groups’ nature. Molecular dynamics calculations endowed support of favorable wrinkling at the edges and carboxyl intercalation to GO surface of types π- π, hydrogen bonding, and hydrophobic interactions. Solvent accessible surface area calculations of GO showed a decrease in total surface area. Environmental nanoremediation of the catalytic reduction of 4-nitrophenol, a priority pollutant listed by USEPA, was investigated. The apparent rate constants Kapp of four catalytic reduction cycles of nitrophenol were measured. The highest value is 1.17 × 10-1 min-1 for the first cycle which decreased to 4.49 × 10 -2 min -1 for the fourth cycle. The variations in rate constants were measured with different conditions, including NaBH 4 concentrations, NC loadings and NC incubating time in NaBH4.

Unlocking photoredox selective organic transformation over metal-free 2D transition metal chalcogenides-MXene heterostructures

Two-dimensional (2D) transition metal carbide, known as MXene, has recently received enduring attention for solar energy conversion by virtue of its pivotal role as efficient interfacial charge transfer mediator for photocatalysis. However, controllable design of MXene-based heterostructured photosystems is still in the infant stage and MXene-dominated photoredox mechanism in photoredox selective organic catalysis has so far not yet been unleashed. Herein, we conceptually report the rational construction of 2D/2D heterostructures by a facile electrostatic self-assembly approach utilizing oppositely charged transition metal chalcogenides (TMCs: CdIn2S4, CdS, Zn0.5Cd0.5S, ZnIn2S4) nanosheets (NSs) and Ti3C2Tx (MXene) as the building blocks for photocatalytic selective organic transformation. The peculiar face-to-face stacking mode between the building blocks and suitable energy level alignment synergistically endow the MXene-TMCs NSs heterostructures with markedly enhanced photoactivities toward multifarious photoredox catalysis including anaerobic selective photoreduction of nitroaromatics to amino derivatives and photoxidation of aromatic alcohols to aldehydes under the irradiation of visible light. The considerably enhanced photoactivities of MXene-TMCs NSs heterostructures are caused by the integrated merits of Ti3C2Tx (MXene) including: (i) abundant hydrophilic groups on the Ti3C2Tx (MXene) surface for affording substantial interaction with TMCs NSs, which benefits the charge migration; (ii) strong redox activities of surface Ti sites which promotes multiple electron reduction; (iii) electrons-withdrawing capability of Ti3C2Tx (MXene) to boost the electron transfer from TMCs NS to Ti3C2Tx (MXene), thereby enhancing the charge separation. This work would open a new frontier for constructing a host of MXene-based heterostructured photosystems and unveiling the charge transfer mechanism of MXene for solar energy conversion.