High Efficient Charge Transfer Research Articles

Metallo-Supramolecular Helicates as Surface-Enhanced Raman Scattering (SERS) Substrates with High Tailorability.

The exploration of novel functionalized supramolecular coordination complexes (SCCs) can enable new applications in domains that include purification and sensing. In this study, employing a coordination-driven self-assembly strategy, we designed and prepared a series of benzochalcogenodiazole-based metallohelicates as high-efficiency charge transfer surface-enhanced Raman scattering (SERS) substrates, expanding the range of applications for these metallohelicates. Through structural modifications, including the substitution of single heteroatoms on ligands, replacement of coordinating metals, and alteration of ligand framework linkages, the Raman performance of these metallohelicates as substrates were systematically optimized. Notably, the SERS enhancement factors (EFs) of the metallohelicate-based SERS substrates were significantly enhanced to levels as high as 1.03 × 107, which rivals the EFs of noble metals devoid of "hot spots". Additionally, the underlying Raman enhancement mechanisms of these metallohelicates have been investigated through a combination of control experiments and theoretical calculations. This study not only demonstrates the utility of metallohelicates as SERS substrates but also offers insights and materials for the development of high-efficiency new charge transfer SERS substrates.

Plasmonic tandem heterojunctions enable high-efficiency charge transfer for broad spectrum photocatalytic hydrogen production

Rational engineering of semiconductor photocatalysts for efficient hydrogen production is of great significance but still challenging, primarily due to the limitations in charge transfer kinetics. Herein, a fascinating plasmonic tandem heterojunction with the hc-CdS/Mo2C@C heterostructure is aimfully prepared for effectively promoting the charge separation kinetics of the CdS photocatalyst via the synergistic strategy of phase junction, Schottky junction, and photothermal effect. The difference in atomic configuration between cubic-CdS (c-CdS) and hexagonal-CdS (h-CdS) leads to effective charge separation through a typical II charge transfer mechanism, and plasmonic Schottky junction further extracts the electrons in the hc-CdS phase junction to realize gradient charge transfer. Besides, the photothermal effect of Mo2C@C helps to expand the light absorption, accelerate charge transfer kinetics, and reduce the hydrogen evolution energy barrier. The carbon layer provides a fast channel for charge transfer and protects the photocatalyst from photocorrosion. As a result, the optimized hc-CMC photocatalyst exhibits a significantly high photocatalytic H2 production activity of 28.63 mmol/g/h and apparent quantum efficiency of 61.8%, surpassing most of the reported photocatalysts. This study provides a feasible strategy to enhance the charge transfer kinetics and photocatalytic activity of CdS by constructing plasmonic tandem heterogeneous junctions.

Elaborate Modulating Binding Strength of Intermediates via Three-component Covalent Organic Frameworks for CO2 Reduction Reaction.

The catalytic performance for electrocatalytic CO2 reduction reaction (CO2RR) depends on the binding strength of the reactants and intermediates. Covalent organic frameworks (COFs) have been adopted to catalyze CO2RR, and their binding abilities are tuned via constructing donor-acceptor (DA) systems. However, most DA COFs have single donor and acceptor units, which caused wide-range but lacking accuracy in modulating the binding strength of intermediates. More elaborate regulation of the interactions with intermediates are necessary and challenge to construct high-efficiency catalysts. Herein, the three-component COF with D-A-A units was first constructed by introducing electron-rich diarylamine unit, electron-deficient benzothiazole and Co-porphyrin units. Compared with two-component COFs, the designed COF exhibit elevated electronic conductivity, enhanced reducibility, high efficiency charge transfer, further improving the electrocatalytic CO2RR performance with the faradic efficiency of 97.2 % at -0.8 V and high activity with the partial current density of 27.85 mA cm-2 at -1.0 V which exceed other two-component COFs. Theoretical calculations demonstrate that catalytic sites in three-component COF have suitable binding ability of the intermediates, which are benefit for formation of *COOH and desorption of *CO. This work offers valuable insights for the advancement of multi-component COFs, enabling modulated charge transfer to improve the CO2RR activity.

Elaborate Modulating Binding Strength of Intermediates via Three‐component Covalent Organic Frameworks for CO2 Reduction Reaction

AbstractThe catalytic performance for electrocatalytic CO2 reduction reaction (CO2RR) depends on the binding strength of the reactants and intermediates. Covalent organic frameworks (COFs) have been adopted to catalyze CO2RR, and their binding abilities are tuned via constructing donor‐acceptor (DA) systems. However, most DA COFs have single donor and acceptor units, which caused wide‐range but lacking accuracy in modulating the binding strength of intermediates. More elaborate regulation of the interactions with intermediates are necessary and challenge to construct high‐efficiency catalysts. Herein, the three‐component COF with D‐A‐A units was first constructed by introducing electron‐rich diarylamine unit, electron‐deficient benzothiazole and Co‐porphyrin units. Compared with two‐component COFs, the designed COF exhibit elevated electronic conductivity, enhanced reducibility, high efficiency charge transfer, further improving the electrocatalytic CO2RR performance with the faradic efficiency of 97.2 % at −0.8 V and high activity with the partial current density of 27.85 mA cm−2 at −1.0 V which exceed other two‐component COFs. Theoretical calculations demonstrate that catalytic sites in three‐component COF have suitable binding ability of the intermediates, which are benefit for formation of *COOH and desorption of *CO. This work offers valuable insights for the advancement of multi‐component COFs, enabling modulated charge transfer to improve the CO2RR activity.

Ultrasensitive electrochemical sensor via bismuth vanadate anchored graphite for detection of carbendazim in fruits and vegetables

Herein, we fabricated a novel electrochemical sensor based on bismuth vanadate/graphite nanocomposites (BiVO4/Gr/GCE) for rapid and ultrasensitive detection of carbendazim. The fabricated BiVO4/Gr/GCE sensor exhibited better electrochemical performances toward carbendazim than the sensors that modified by BiVO4, Gr and bare-electrode, respectively. For the BiVO4/Gr/GCE nano-composite, the porous Gr possesses large specific area, almighty conductivity capability, high-efficiency charge transfer, while hollow BiVO4 can promote the adsorption and electro-transfer efficiency of CBD on the BiVO4/Gr/GCE sensor. Additionally, Gr with remarkable conductivity could largely compensate the inferior-conductivity and prevent the aggregation dispersion of BiVO4. The synergistic effect of BiVO4 and Gr result in significant electro-activity good electrochemical sensing capability towards CBD. The fabricated sensor showed a wide linear response range in 4.0 × 10−8∼1.0 × 10−5, 1.0 × 10−5∼8.0 × 10−5 M with the correlation coefficient of R2 = 0.997 and R2 = 0.995, respectively. The limit of detection was 3.78 × 10−9 M (S/N = 3). Moreover, the proposed BiVO4/Gr/GCE sensor as well displays good operating stability, reproducibility, anti-disruptors, and repeatability for carbendazim detection. Furthermore, it was successfully used for carbendazim detection in pear and tomato juice with satisfactory recoveries of 90%∼108.3%, indicating that the sensor has a promising application for the detection of actual carbendazim.

Size-dependent SERS property of red phosphorous in the transition from bulk to nanosheet and its application in immunosensing

Attributed to their structure-dependent chemical enhancement capability and perfect biocompatibility, semiconductors have attracted significant concern in surface enhanced Raman scattering (SERS)-based immunoassay. By continually adjusting the size of red phosphorus (RP) in the transition process from bulk to nanosheet, we investigated in detail about the improvement of high-efficient charge transfer (CT) resonance dependent on the perfect energy level matching within the substrate-molecule combination. The nano-sized RP has achieved an impressive three-fold enhancement in SERS intensity in comparison to the RP nanosheet. Furthermore, the RP-based immunosubstrate was combined with MoS2 nanoflowers-based immunoprobe to construct a sandwich immunostructure for the accurate and efficient diagnostics of cancer marker prostate-specific antigen. A limit of detection as low as 3.99 × 10−10 M was obtained in the SERS-based immunoassay with reliable specificity. This study presents an innovative approach to promote the SERS performance of semiconductors, which may find potential biological applications in the early screening of cancer.

Unveiling the origin of high-efficiency charge transport effect of C3N5/C3N4 homojunction for activating peroxymonosulfate to degrade atrazine under visible light

Photocatalytic activation of PMS is a potential advanced oxidation process in refractory wastewater purification. Herein, a C3N5/C3N4 homojunction (AT-CN) catalyst as an efficient photocatalyst for PMS activation is reported, which owns interlaced band structure, high-efficiency charge transfer, and PMS activation capability. This homojunction structure is demonstrated to be highly efficient in charge transfer and separation. As experimental result, the reaction rate constants of atrazine in AT-CN/PMS/Vis system increased to 2.9-fold and 7.4-fold, compared with C3N4/PMS/Vis and C3N5/PMS/Vis system. The photocatalytic activation of PMS for atrazine removal efficiency reached 97 % within 60 min (under pH = 3). The band structure, the charge density difference, the PMS adsorption behavior of AT-CN, and the activation pathways of PMS have been studied through the DFT calculation. According to experimental and DFT simulation, the AT-CN homojunction not only suppress the charge recombination via built-in electric field, but also exhibited a better PMS activation capability. In brief, this study through the combination of experiment and simulation is providing more inspiration for designing appropriate nonmetal homojunction in the photo-activated PMS process.

A high-performance and broadband two-dimensional perovskite-based photodetector via van der Waals integration

Van der Waals (vdW) integration of two-dimensional (2D) nanosheets provides the possibility to design optoelectronic devices with extended functionality in a controllable manner. Here, by leveraging the appropriate energy band alignment and the high-efficiency charge transfer at the junction, we construct the MoS2/graphene/2D-perovskite vdW heterostructure, which realizes the highly sensitive and broadband photodetection. Particularly, at the near-infrared (NIR) wavelength (λ = 1550 nm), the heterostructure photodetector shows a balanced trade-off between the high responsivity (>3000 A/W) and fast response time (<1 ms), outperforming the previously reported NIR photodetectors based on all-inorganic vdW heterostructures. Our work not only extends the response wavelength of the 2D hybrid perovskite-based photodetector to the NIR range, but also offers additional insight into optoelectronic devices via vdW integration engineering.

Constructing a p-n heterojunction in 3D urchin-like CoNixSy/g-C3N4 composite microsphere for high performance asymmetric supercapacitors

A built-in electric field generated at the p-n heterojunction will enhance charge transfer at the interface, which brings a new strategy for improving electrochemical energy storage. Herein, we construct a novel p-n heterojunction in a three-dimensional (3D) urchin-like CoNixSy/g-C3N4 (3D–2D) junction microsphere based on a one-step solvothermal method. The forming built-in electric field at the heterointerface of p-type semiconductor (CoNixSy) and n-type semiconductor (g-C3N4) ensure its high-efficiency charge transfer. Besides, the porous 3D urchin-like microsphere could facilitate the diffusion of electrolytes and enhance the stability and volumetric energy density. Benefiting from the synergistic advantages of the p-n heterojunction and the 3D urchin-like structure, the CoNixSy/g-C3N4 electrode displayed an ultrahigh battery-type specific capacity (1029 C g−1) in a three-electrode system. Furthermore, an asymmetric supercapacitor formed by positive electrode of CoNixSy/g-C3N4 and negative electrode of activated carbon (AC) obtains a high energy density of 71.9 Wh kg−1 and a retention of 72.2% after 5000 cycles.

High-efficiency charge transfer on SERS-active semiconducting K2Ti6O13 nanowires enables direct transition of photoinduced electrons to protein redox centers

Photoinduced charge transfer (PICT) plays a crucial role in the chemical mechanism of surface-enhanced Raman scattering (SERS), in which small organic molecules are generally used as probes. Herein, semiconducting K2Ti6O13 nanowires (NWs) are synthesized and are found to exhibit high SERS activity probed by 4-mercaptobenzoic acid (4-MBA). Density functional theory (DFT) calculations reveal high-efficiency CT on the K2Ti6O13 nanowires. Furthermore, PICT on the K2Ti6O13 NWs is for the first time evidenced by a redox protein, cytochrome c (Cyt c). Under optimized experimental conditions, the transformation of oxidized Cyt c to its reduced state clearly verifies the electron transfer (ET) from the K2Ti6O13 nanowire to the protein. The ET mechanism is explored based on energy levels of semiconductors and molecular dynamics simulations, thus revealing the importance of energy level matching and electron tunneling from the semiconductor surface to the redox center. This study indicates a great potential of multiple-layered K2Ti6O13 NWs in the application of SERS on semiconducting materials and more importantly, it provides a new route for the rational design of protein-semiconductor interfaces for investigating electron transfer processes of redox proteins and biocatalytic reactions.

A SERS biosensor constructed by calcined ZnO substrate with high-efficiency charge transfer for sensitive detection of Pb2+

Herein, calcined ZnO submicron flowers (ZnO SFs) with excellent surface enhanced Raman scattering (SERS) activity were employed as substrate to fabricate a novel SERS biosensor for sensitive detection of Pb2+, which improved SERS effect of ZnO submicron particles (ZnO SPs). Compared with ZnO SPs, calcined ZnO SFs substrate possessed narrow energy band to enhance the efficiency of charge transfer owing to easily generate exciton transition to achieve eminent Raman enhancement effect. Furthermore, free-legged DNA walker amplification strategy was utilized to convert trace amounts of Pb2+ into vast trigger DNAs for construction an ultrasensitive biosensor, which exhibited a liner relationship ranged from 10 pM to 100 μM with a low detection limit of 3.55 pM. Therefore, this work not only provided a novel approach for detection of heavy metal ions, but also broadened the application of semiconductor SERS substrate.

Modification of graphitic carbon nitride by elemental boron cocatalyst with high-efficient charge transfer and photothermal conversion

• Elemental boron (EB) was applied as a cocatalyst for photocatalysis. • The photothermal effect of EB lead to the increase of reaction temperature. • Increased temperature resulted in better molecular collision and charge transfer. • The load of EB modulated band structure and enhanced the charge separation. Photocatalysis is considered as a promising method to degrade pollutants with clean and readily available energy source. Great efforts have been devoted to improve solar energy utilization of the photocatalyst. Herein, we report that elemental boron (EB) nanoparticle can act as an advanced bi-functional cocatalyst for photocatalysis with high solar energy utilization. As a photothermal material, EB could convert long-wavelength light energy to heat to increase the reaction temperature and accelerate the photocatalytic reaction. Moreover, the strong electronic interaction between EB and graphitic carbon nitride altered band structure and also suppressed the recombination of charge carriers. Benefiting from these, EB decorated graphitic carbon nitride exhibited dramatic improvement in photocatalytic degradation of sulfamerazine under the simulated sunlight. This work not only reveals the hidden talent of elemental boron as an advanced bi-functional cocatalyst, but also provides an alternative strategy for efficient full-spectrum solar energy conversion.

Charge-transfer-mediated photocatalysis of W18O49@CdS nanotubes to boost photocatalytic hydrogen production

Photocatalysts for hydrogen (H2) production is urgently needed. Herein, the Z-scheme CdS@W18O49 nanotubes are described where CdS nanoparticles are wrapped into hollow W18O49 nanotubes via a hydrothermal process. Thanks to the broad absorption from UV to NIR region and the high efficient charge transfer in this direct Z-scheme system, the photocatalyst activity of CdS@W18O49 nanotubes are drastically enhanced. Such CdS@W18O49 nanotubes show a prominent photocatalytic H2 production rate of 11732 μmol h−1 g−1 without any sacrifice agents, which is higher than the most CdS-based photocatalysts. Furthermore, the as-prepared CdS@W18O49 nanotubes exhibit outstanding stability, which can overcome the inherent drawback of photocorrosion and keep their catalytic activity unchanged in a 40 h circular reaction. The time-resolved photoluminescence (TRPL) spectra results confirm the lifetime of photo-generated carriers are greatly prolonged through the fabrication of this direct Z-scheme structure. This work may broaden the application potential of some catalysts with inherent drawbacks and provide a valuable guideline for developing highly efficient photocatalysts.

Flexible perylenediimide/GaN organic\u2013inorganic hybrid system with exciting optical and interfacial properties

We report the band gap tuning and facilitated charge transport at perylenediimide (PDI)/GaN interface in organic–inorganic hybrid nanostructure system over flexible titanium (Ti) foil. Energy levels of the materials perfectly align and facilitate high efficiency charge transfer from electron rich n-GaN to electron deficient PDI molecules. Proper interface formation resulted in band gap tuning as well as facilitated electron transport as evident in I–V characteristics. Growth of PDI/GaN hybrid system with band gap tuning from ultra-violet to visible region and excellent electrical properties open up new paradigm for fabrication of efficient optoelectronics devices on flexible substrates.

Cytochrome C-decorated graphene field-effect transistor for highly sensitive hydrogen peroxide detection

High-level in vivo reactive oxygen species (ROS) can damage many biomolecules via oxidative stress and play vital roles in the pathogenesis of several bodily disorders. Therefore, fast and sensitive monitoring strategies for trace ROS, such as hydrogen peroxide (H2O2), are of great significance. Herein, we present a highly sensitive field-effect transistor (FET) sensor based on single-layer graphene for trace hydrogen peroxide (H2O2) detection. Graphene and cytochrome c (Cyt c) were employed as the conductive substrate material and biomolecular receptor for H2O2 detection, respectively. High-efficiency charge transfer can be achieved by reliable electrical contact across the Cyt c/underlying graphene interface. The Cyt c/graphene FET platform exhibited hole-transport behavior with high conductivity and high sensitivity toward H2O2 with a detection limit of 100fM and rapid response time (<1s). Moreover, our sensor platform was able to specifically discriminate H2O2 from a series of interfering substances, such as dopamine, ascorbic acid, glucose, uric acid and glutamate. This result, therefore, demonstrates that the proposed Cyt c/single-layer graphene FET sensor could facilitate the high-efficiency charge transfer between the redox center of the Cyt c/graphene interface, indicating a promising application in future trace H2O2 or free radical biosensors.

Amorphous Mn3 O4 Nanocages with High-Efficiency Charge Transfer for Enhancing Electro-Optic Properties of Liquid Crystals.

Improving electro-optic properties is essential for fabricating high-quality liquid crystal displays. Herein, by doping amorphous Mn3 O4 octahedral nanocages (a-Mn3 O4 ONCs) into a nematic liquid crystal (NLC) matrix E7, outstanding electro-optic properties of the blend are successfully obtained. At a doping concentration of 0.03 wt%, the maximum decreases of threshold voltage (Vth ) and saturation voltage (Vsat ) are 34% and 31%, respectively, and the increase of contrast (Con ) is 160%. This remarkable electro-optic activity can be attributed to high-efficiency charge transfer within the a-Mn3 O4 ONCs NLC system, caused by metastable electronic states of a-Mn3 O4 ONCs. To the best of our knowledge, such remarkable decreased electro-optic activity is observed for the first time from doping amorphous semiconductors, which could provide a new pathway to develop excellent energy-saving amorphous materials and improve their potential applications in electro-optical devices.

High-Performance All-Inorganic CsPbCl3 Perovskite Nanocrystal Photodetectors with Superior Stability.

All-inorganic perovskites nanostructures, such as CsPbCl3 nanocrystals (NCs), are promising in many applications including light-emitting diodes, photovoltaics, and photodetectors. Despite the impressive performance that was demonstrated, a critical issue remains due to the instability of the perovskites in ambient. Herein, we report a method of passivating crystalline CsPbCl3 NC surfaces with 3-mercaptopropionic acid (MPA), and superior ambient stability is achieved. The printing of these colloidal NCs on the channel of graphene field-effect transistors (GFETs) on solid Si/SiO2 and flexible polyethylene terephthalate substrates was carried out to obtain CsPbCl3 NCs/GFET heterojunction photodetectors for flexible and visible-blind ultraviolet detection at wavelength below 400 nm. Besides ambient stability, the additional benefits of passivating surface charge trapping by the defects on CsPbCl3 NCs and facilitating high-efficiency charge transfer between the CsPbCl3 NCs and graphene were provided by MPA. Extraordinary optoelectronic performance was obtained on the CsPbCl3 NCs/graphene devices including a high ultraviolet responsivity exceeding 106 A/W, a high detectivity of 2 × 1013 Jones, a fast photoresponse time of 0.3 s, and ambient stability with less than 10% degradation of photoresponse after 2400 h. This result demonstrates the crucial importance of the perovskite NC surface passivation not only to the performance but also to the stability of the perovskite optoelectronic devices.

Bi-metal-organic frameworks type II heterostructures for enhanced photocatalytic styrene oxidation.

Fabricating heterostructures enhances the photocatalytic performance of metal-organic frameworks (MOFs) due to their excellent light absorption and high efficient charge transfer capacity. In this study, we designed and implemented three-dimensional dendritic UiO-66-NH2@MIL-101(Fe) (UOML) heterostructures as catalysts for photocatalytic styrene oxidation. The UOML catalysts exhibited a well-matched band gap structure and efficient catalytic interface, leading to a remarkable photoexcited carrier separation and catalytic activity. Our results present a promising insight for synthesizing novel MOFs-based catalysts and their applications.

Printable Nanocomposite FeS2-PbS Nanocrystals/Graphene Heterojunction Photodetectors for Broadband Photodetection.

Colloidal nanocrystals are attractive materials for optoelectronics applications because they offer a compelling combination of low-cost solution processing, printability, and spectral tunability through the quantum dot size effect. Here we explore a novel nanocomposite photosensitizer consisting of colloidal nanocrystals of FeS2 and PbS with complementary optical and microstructural properties for broadband photodetection. Using a newly developed ligand exchange to achieve high-efficiency charge transfer across the nanocomposite FeS2-PbS sensitizer and graphene on the FeS2-PbS/graphene photoconductors, an extraordinary photoresponsivity in exceeding ∼106 A/W was obtained in an ultrabroad spectrum of ultraviolet (UV)-visible-near-infrared (NIR). This is in contrast to the nearly 3 orders of magnitude reduction of the photoresponsivity from ∼106 A/W at UV to 103 A/W at NIR on their counterpart of FeS2/graphene detectors. This illustrates the combined advantages of the nanocomposite sensitizers and the high charge mobility in FeS2-PbS/graphene van der Waals heterostructures for nanohybrid optoelectronics with high performance, low cost, and scalability for commercialization.

Enhanced photocurrent gain by CdTe quantum dot modified ZnO nanowire

In this paper, a zinc oxide (ZnO) nanowire (NW) photodetector was fabricated using dielectrophoresis technique. The ZnO NW was synthesized by chemical vapor deposition (CVD) method, and characterized by SEM, XRD and photoluminescence (PL) spectrum. The photodetector showed obvious photoresponse to 365nm UV light. By decorating the ZnO NWs with CdTe quantum dots (QDs), the photocurrent (PC) gain was enhanced from 199 to 2896, when the light intensity was 5.3mW/cm2. The response spectrum was also extended to the visible light region. The underlying mechanism of the enhancement was assigned to the high-efficiency charge transfer caused by the type-II band structure between ZnO NWs and CdTe QDs. The greatly quenched PL intensity of CdTe QDs/ZnO NWs composites provided further evidence for the high efficiency charge transfer.