Charge Transfer Mechanism Research Articles

Boosted charge separation in porphyrin-based MOFs/CdS photocatalyst via interfacial −N−Cd− bridge bond construction

The high interfacial charge transfer barrier has been a main thermodynamic obstacle for improving the catalytic efficiency of heterojunction materials. Optimizing the interfacial environment is an effective strategy to achieve high catalytic efficiency. Herein, the coordinate bond (−N−Cd−) is designed to connect the hafnium porphyrin−metal organic framework (HT) and CdS nanoparticles, which is systematically analyzed by the 1H NMR, FTIR, Raman and DRS, respectively. The optimized 15HT1.5 H/CdS6 composite featuring interfacial bridge bonds, exhibits an H2 production up to 11.9 mmol·g−1·h−1, which is 28.5, 52.8 and 7 times greater than pure CdS, HTH, and mechanically mixed sample without interfacial chemical bonds connected, respectively. Mechanistic study suggests that the coordination bonds between HT and CdS serve as the directional carrier transfer bridges, significantly improving interfacial charge separation and chemical stability. Moreover, the formed Z-scheme charge transfer mechanism also endows the composite with high redox ability. This strategic construction of interfacial chemical bonds within heterojunction provides an effective pathway for improving interfacial charge transfer in the heterojunction photocatalysts.

Enhanced photocatalytic reduction of Cr (VI) using porous hierarchical Bi2O3/Bi2S3 high-low heterojunctions: Novel strategies and charge transfer mechanisms

High-low heterojunctions derived from metal-organic frameworks (MOFs) have promising applications in photocatalytic wastewater treatment because of their high photo-redox ability and boosted charge separation efficiency. Herein, Bi-MOF derived porous hierarchical Bi2O3/Bi2S3 nanoflower-like heterojunctions were prepared by the calcination-hydrothermal method. The optimized Bi2O3/Bi2S3-2 composite showed a higher degradation rate of Cr (VI) (99.79 % in 30 min) than the pure substance. Moreover, comprehensive studies were conducted on the kinetics, stability and recycling of Bi2O3/Bi2S3, as well as optical characteristics. The active species trapping experiments confirmed that e- plays a dominant role in the elimination of Cr (VI). These findings provided novel strategies for construction of porous hierarchical heterojunctions with advanced visible-light-induced degradation performance. The enhanced photo-degradation efficiency of the optimal nanocomposite was assigned to the higher visible-light absorbance, separation of photogenerated carriers, reduced recombination of photo-induced carriers, and enhanced redox capability owing to the construction of porous hierarchical heterojunctions amongst the components.

Charge Transfer Mechanism in Guanine-Based Self-Assembled Monolayers on a Gold Surface.

In this work, we have theoretically determined the one-electron oxidation potentials and charge transfer mechanisms in complex systems based on a self-assembled monolayer of guanine molecules adsorbed on a gold surface through different organic linkers. Classical molecular dynamics simulations were carried out to sample the conformational space of both the neutral and the cationic species. Thus, the redox potentials were determined for the ensembles of geometries through multiscale quantum-mechanics/molecular-mechanics/continuum solvation model calculations in the framework of the Marcus theory and in combination with an additive scheme previously developed. In this context, conformational sampling, description of the environment, and effects caused by the linker have been considered. Applying this methodology, we unravel the phenomena of electric current transport by evaluating the different stages in which charge transfer could occur. The results revealed how the positive charge migrates from the organic layer to the gold surface. Specifically, the transport mechanism seems to take place mainly along a single ligand and driven with the help of the electrostatic interactions of the surrounding molecules. Aside, several self-assembled monolayers with different linkers have been analyzed to understand how the nature of that moiety can tune the redox properties and the efficiency of the transport. We have found that the conjugation between the guanine and the linker, at the same time conjugated to the gold surface, gives rise to a more efficient transport. In conclusion, the established computational protocol sheds light on the mechanism behind charge transport in electrochemical DNA-based biosensor nanodevices.

Preparation and performance of g-C3N4/g-C3N5 homojunction photocatalyst activated peroxymonosulfate for ceftriaxone sodium degradation

As the overuse of antibiotics increasingly contaminates the environment, one of modern chemistry's objectives is to identify high-performance photocatalytic materials to degrade antibiotics. This study initially utilized NH4Cl as a gas template to synthesize porous lamellar g-C3N4 (CNS) through a high-temperature calcination process. Building upon this, a homojunction catalyst, CNS/g-C3N5 (S-CN), was developed via a secondary sintering technique using different amount of 3-amino-1,2,4-triazole addition to evaluate its efficacy in activating peroxymonosulfate (PMS) for degrading the antibiotic ceftriaxone sodium. Under neutral conditions, the photocatalytic system composed of S-CN catalysts prepared by 50 mg of 3-amino-1,2,4-triazole addition and PMS (S3-CN/PMS) exhibited degradation rates that were 3.37 and 8.11 times higher than those of the CNS/PMS and g-C3N5/PMS, respectively. At a pH of 8, the S3-CN/PMS system attained a 99.7 % degradation efficiency within 75 min. Based on results from UV–visible diffuse reflectance spectroscopy (DRS), transient photocurrent response, electrochemical impedance spectroscopy (EIS), photoluminescence spectroscopy and radical scavenging experiments, this high efficiency is attributed to a homojunction Z-type charge transfer mechanism that enhances the separation of photogenerated carriers. Furthermore, the study found that the optimal PMS addition was 20 mg and the optimal pH was 8. Chloride ions promoted the reaction, while other ions decreased the reaction rate. In conclusion, this paper provides valuable insights for the morphological modification of carbon nitride homojunction materials and the efficient activation of PMS for pollutant degradation.

Pseudohalide-Based Ionic Liquids: Advancing Crystallization Kinetics and Optoelectronic Properties in All-Inorganic Perovskite Solar Cells.

This study delves into the innovative approach of enhancing the efficiency and stability of all-inorganic perovskite solar cells (I-PSCs) through the strategic incorporation of thiocyanate (SCN-) ions via pseudohalide-based ionic liquid (IL) configurations. This straightforward methodology has exhibited captivating advancements in the kinetics of crystallization as well as the optoelectronic characteristics of the resulting perovskite films. These developments hold the promise of enhancing not only the quality and uniformity of the films but also aspects such as band alignment and the efficacy of charge transfer mechanisms. Calculation results corroborate that the incorporation of 1-butyl-3-methylimidazolium thiocyanate (BmimSCN)led to a significant redistribution of electron state density and enhanced electron-donating properties, indicating a substantial electron transfer between the perovskite material and the IL. Notably, the engineered devices demonstrate a remarkable efficiency surpassing 15%, a substantial enhancement attributed to the synergistic effects of the SCN- ion. Additionally, this approach offers inherent stability benefits, thereby addressing a significant challenge in I-PSC technology. This IL maintains >90% of the initial efficiency after 600h, while the control device decreased to <20% of its initial value after only 100h. 1-butyl-3-methylimidazolium iodide (BmimI) is also employed to further investigate the effects of SCN- ions on device performance.

Band alignment and charge transfer mechanisms in the prediction of advanced gate dielectrics for carbon nanotube field-effect transistors

The search for novel gate dielectrics to mitigate interface state density is a pressing concern in the fabrication of high-performance carbon nanotube field-effect transistors (CNT-FETs). In this study, we investigated the feasibility of employing strontium titanate (STO) with an ultra-high dielectric constant as the gate dielectric in CNT-FETs. By combining X-ray photoelectron spectroscopy measurements with first-principles calculations, we determined the band offsets between CNT and STO, as well as between CNT and conventional gate dielectrics such as HfO2 and SiO2. The valence/conduction band offset (VBO/CBO) at the STO/CNT interface is found to be 1.1 eV/1.5 eV, which is the smallest among all studied interfaces, followed by those at HfO2/CNT interface (VBO = 1.3 eV/CBO = 3.4 eV) and SiO2/CNT interface (VBO = 3.6 eV/CBO = 4.5 eV). Moreover, charge transfer at the STO/CNT interface exhibits two orders of magnitude lower values compared to that at HfO2/CNT interface and is also significantly smaller than that at SiO2/CNT interface. This phenomenon can be ascribed to the combined effects of van der Waals forces at the STO/CNT interface and fewer dangling bonds on the STO surface. These findings suggest exceptional compatibility between STO and CNT, making STO highly suitable for high-performance CNT-FETs.

Fast-Responsive HClO-Activated Near-Infrared Fluorescent Probe for In Vivo Diagnosis of Inflammatory Bowel Disease and Ex Vivo Optical Fecal Analysis.

Inflammatory bowel disease (IBD) is an idiopathic intestinal inflammatory disease, whose etiology is intimately related to the overproduction of hypochlorous acid (HClO). Optical monitoring of HClO in the living body favors real-time diagnosis of inflammatory diseases. However, HClO-activated near-infrared (NIR) fluorescent probes with rapid response and high inflammatory cell uptake are still lacking. Herein, we report an activatable acceptor-π-acceptor (A-π-A)-type NIR fluorescent probe (Cy-DM) bearing two d-mannosamine groups for the sensitive detection of HClO in early IBD and stool testing. Once reacted with HClO, nonfluorescent Cy-DM could be turned on within 2 s by generating a donor-π-acceptor (D-π-A) structure due to the enhanced intramolecular charge transfer mechanism, showing intense NIR fluorescence emission at 700 nm and a large Stokes shift of 115 nm. Moreover, it was able to sensitively and selectively image exogenous and endogenous HClO in the lysosomes of living cells with a detection limit of 0.84 μM. More importantly, because of the d-mannosamine modification, Cy-DM was efficiently taken up by inflammatory cells in the intestine after intravenous administration, allowing noninvasive visualization of endogenous HClO in a lipopolysaccharide-induced IBD mouse model with a high fluorescence contrast of 6.8/1. In addition, water-soluble Cy-DM has also been successfully applied in ex vivo optical fecal analysis, exhibiting a 3.4-fold higher fluorescence intensity in the feces excreted by IBD mice. We believe that Cy-DM is promising as an invaluable tool for rapid diagnosis of HClO-related diseases as well as stool testing.

Construction of loading g-C3N4/TiO2 on waste cotton-based activated carbon S-scheme heterojunction for enhanced photocatalytic degradation of microplastics: Performance, DFT calculation and mechanism study

In order to achieve the degradation of polyethylene microplastics (PE) in wastewater. The g-C3N4/TiO2/WCT-AC composite photocatalytic materials were prepared by mixed high-temperature thermal polymerization method with the g-C3N4 and the waste cotton based activated carbon (WCT-AC) loaded TiO2 as precursors. The phase morphology, elemental composition, morphology and photochemical properties of the g-C3N4/TiO2/WCT-AC were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), ultraviolet–visible diffuse reflectance spectrum (UV–vis DRS) and photo luminescence (PL). The results of UV–vis DRS and PL showed that the combination of the g-C3N4 and the TiO2/WCT-AC improved the absorption in the visible region, broadened the spectral response range, and the formation of heterojunctions enabled efficient photoelectron-hole separation and improved the photocatalytic activity. Under visible light irradiation for 200 h, catalyst dosage 50 mg, and system pH = 7.0, the highest removal rate of the g-C3N4/TiO2/WCT-AC for PE microplastics reached 67.58 %, and it still showed excellent stability after 5 cycles. The active groups such as ·O2−, ·OH and h+ produced in the g-C3N4/TiO2/WCT-AC system under visible light excitation realized the degradation of PE microplastics. The whole process is a complex oxidation bond breaking process, and the degradation of PE microplastics by g-C3N4/TiO2/WCT-AC follows the S-type charge transfer mechanism.

In situ loading of Ag2MoO4 nanoparticles onto oxygen-doped porous g-C3N4 for enhanced photocatalytic H2 evolution

Photogenerated carriers transfer and separation from the substance itself to produce spatial isolated electron-hole pairs is crucial for the utilization of composite photocatalysts in the field of photocatalytic hydrogen (H2) evolution. Herein, novel oxygen-doped porous graphitic carbon nitride (g-C3N4) micro-sheets decorated with Ag2MoO4 have been fabricated by a facile calcination method followed by in situ deposition strategy. The physicochemical properties of the obtained Ag2MoO4/OC3N4 composites were characterized via SEM, TEM, EDS, XRD, N2 adsorption-desorption, XPS, UV–vis DRS, PL, transient photocurrent response, and EIS, as well as DFT calculation. In addition, the effects of Ag2MoO4 content, type of scavengers, pH value of reaction solution and dosage of scavenger on photocatalytic H2 production were investigated. The results show that the modification of ammonium acetate thermal polymerization with urea could enhance the porosity of g-C3N4 and its specific surface area. The Ag2MoO4 nanoparticles are highly dispersed on the OC3N4 surface, reducing the charge transfer resistance at their interfaces. The OC3N4 photocatalyst achieves H2 yield of 8629.11 μmol/g over 2 h, which is about 1.46 times higher than that of C3N4. The H2 production amount over the optimal Ag2MoO4/OC3N4 composite photocatalyst (50 mg) is further enhanced to 16619 μmol/g, which is 1.93 and 180 times higher than that of OC3N4 and Ag2MoO4, respectively. The S-scheme charge transfer mechanism of Ag2MoO4/OC3N4 is proposed based on the DFT calculation. This work provides a facile and easy strategy to develop g–C3N4–based photocatalysts through adjusting chemical composition and photocatalytic properties.

Tailored nanocones arrays on cellulose fiber: A higher-performance flexible SERS substrate for trace chemical detection

This study presents the successful fabrication of silver nanocone surface-enhanced Raman spectroscopy (SERS) substrate on flexible 70 GSM paper using the Direct Current (DC) magnetron sputter deposition technique. XRD analysis confirmed the crystalline nature and face-centered cubic structure of the Silver Nanocone (AgNC) substrate. SEM analysis revealed the fabricated AgNC substrate shows nanocones arrayed on the cellulose fibers. UV–visible spectral analysis validates the surface plasmon resonance peak of the AgNC substrate at 406 nm. Furthermore, SERS spectral analysis showed excellent detection abilities by accurately identifying rhodamine 6G and methylene blue dyes and fipronil pesticides at concentrations of 10−9 M, 10−8 M, and 10−6 M respectively. In addition, the substrate detects fipronil (pesticide) sprayed on tomatoes and nicotine (energy booster) mixed with tea for commercial applications. The substrate exhibits enhancement factor values for rhodamine 6G, methylene blue, fipronil, and nicotine as 1.3 × 107, 1.2 × 106, 2.6 × 105, and 5.8 × 104, respectively. Theoretical validation using density functional theory confirms the experimental Raman and SERS peaks show good similarity. Considering that the charge transfer mechanism shown in the study of the frontier molecular orbitals allowed for the identification of the interaction between the analyte molecules and silver cluster. The fabricated SERS substrate exhibited remarkable stability and reproducibility.

Heterostructure engineering of resorcinol-formaldehyde resins and sulfur-vacancy-containing Zn3In2S6 for high-efficiency photocatalytic H2O2 production

Resorcinol-formaldehyde (RF) resins have garnered significant interest due to their remarkable efficiency in producing photocatalytic H2O2. The combination of RF with inorganic semiconductors to create organic–inorganic heterojunctions represents a promising strategy for enhancing photocatalytic activity. In this work, RF was coated onto Zn3In2S6 nanoflowers with sulfur-vacancy, creating RF/Zn3In2S6 composites with an S-scheme heterostructure. This novel composite exhibited superior photocatalytic activity for H2O2 production in both pure water and seawater, without sacrificial agents. Specifically, the production rate of RF/Zn3In2S6-0.3 in pure water under simulated solar illumination achieved 3174.34 μmol/h/g, marking 8.53 and 4.17 times over RF and Zn3In2S6, respectively. Moreover, its photocatalytic activity in seawater reached an impressive 2290.81 μmol/h/g, 4.93 and 3.12 times greater than that of RF and Zn3In2S6, respectively. The enhanced photocatalytic activity is attributed to the S-scheme charge transfer mechanism, which facilitates efficient charge separation and amplifies redox capabilities. Both experimental and density function theory analyses confirm the S-scheme route in RF/Zn3In2S6-0.3 for photocatalytic H2O2 production. This study not only presents the first account of an organic semiconductor RF being employed in an S-scheme heterojunction interface but also introduces the surface sulfur-vacancy mediated S-scheme heterojunction strategy for photocatalytic H2O2 production, representing a significant advancement in the field.

A lysosomal-targeted and viscosity-ultrasensitive near-infrared fluorescent probe for sensing viscosity in cells and a diabetic mice model

Diabetes, as a metabolic disorder, has been implicated in organ dysfunction, often correlated with aberrant changes in viscosity. Lysosomal viscosity serves as an indicator of the lysosome's condition and activity, as it always varies synchronously with the change of lysosome's positioning, structure, and internal constituents. Diabetes, a condition within the metabolic disease category, has the potential to disrupt organ function due to irregular changes in viscosity. Therefore, early and precise diagnosis of diabetes is crucial for the prevention and management of diabetic conditions. Understanding the correlation between viscosity variations and lysosomal changes in vivo is vitally important for researching associated diseases. In this study, we developed Lyso-V, a near-infrared (NIR) fluorescent probe targeting lysosomes, with ultrasensitivity to viscosity changes. This probe, designed with a donor-π-bridge-acceptor (D-π-A) structure, exhibits a significant increase in NIR fluorescence intensity (approximately 690 times) when responding to viscosity, due to a twisted intramolecular charge transfer (TICT) mechanism. Furthermore, the probe designed specifically for lysosomes, enables the detection of changes in lysosomal viscosity as well as autophagy processes. Notably, through the application of this probe, we have detected an increased viscosity within the pathological model of the diabetic mouse. Moreover, Lyso-V was employed to measure the viscosity in diabetic mice. Owing to the multifaceted nature of the Lyso-V probe, it is anticipated to act as a practical and potent resource for deepening our understanding of the pathophysiological aspects of diabetes and aiding in its early detection.

An oxidizer-resistant fluorescence probe for detecting bisulfite and viscosity in biosystems

Fluorescence probes bearing malononitrile derivatives as electron withdrawing group have attracted the interests of many researchers during the past decades. Even for the similar fluorophore, the sensing mechanism and pathway could be much different and hard to predict. Thus, we designed a fluorescence probe consisting 2-(3,5,5-trimethylcyclohex-2-en-1-ylidene)malononitrile as the electron withdrawing group and thienocoumarin as fluorophore in order to investigate the possible superiority in designing related optical sensors. In our research, it is interesting to find that our probe has the different properties compared with the similar reported probe bearing the coumarin fluorophore. The novel fluorescent probe (CSO–CN) was demonstrated to be able to detect HSO3− ions and changes in viscosity with a good resistance to oxidizers. The probe offers high sensitivity (LOD = 0.149 μM) for detecting HSO3− via the Michael addition reaction. It also enables fluorescence emission at 483 nm and the tracking of viscosity alternation by impeding the twisted intramolecular charge transfer (TICT) mechanism. Besides, the dual-functional probe has effectively been utilized to monitor HSO3− level in living cells, zebrafish and real food samples.

Sulfur-vacancy-modified ZnIn2S4/TpPa-1 S-scheme heterojunction with enhanced internal electric field for boosted photocatalytic hydrogen production

The construction of S-scheme heterojunction is an effective approach to accelerate photocarrier transfer and improve charge utilization, thus promoting photocatalytic hydrogen evolution. Herein, we report, for the first time, the construction of a S-scheme heterojunction based on sulfur-vacancy-modified ZnIn2S4 (Sv-ZIS) and covalent organic frameworks (COFs), by in-situ growth of Sv-ZIS on COF TpPa-1 (composed of 1,3,5-triformylphloroglucinol and p-phenylenediamine). Under visible-light irradiation, in the absence of cocatalyst, the optimal Sv-ZIS/TpPa-1 (5:1) (with a Sv-ZIS: TpPa-1 mass ratio of 5:1) achieved an enhanced hydrogen production rate of 2745 μmol g−1 h−1 than parent ZIS/TpPa-1 (5:1), with an AQE of 4.67 % at 420 nm. Theoretical calculations confirmed that sulfur-vacancy enlarged the internal electric field (IEF) in Sv-ZIS/TpPa-1, leading to greater interfacial charge transfer from Sv-ZIS to TpPa-1 than that of ZIS to TpPa-1. The enhanced IEF and rapid separation and transfer of photocarriers following S-scheme charge transfer mechanism synergistically guaranteed the improved performance.

Novel phenothiazine appended thiophene and pyridine for highly selective and sensitive detection of hypochlorite in aqueous and living cells

A novel colorimetric chemosensor, (Z)-3-(5-(10H-phenothiazin-10-yl)thiophen-2-yl)-2-(pyridin-2-yl)acrylonitrile (PTH-TH-PY), was synthesized through Buchwald coupling followed by Knoevenagel condensation for the detection of hypochlorite ions (OCl-). This compound demonstrates exceptional selectivity and sensitivity towards OCl- ions with a low detection limit of 0.2 nM. PTH-TH-PY's remarkable sensitivity is attributed to its effective inhibition of the internal charge transfer (ICT) mechanism. High-resolution mass spectrometry (HR-MS) and Job's plot analysis confirmed a 1:1 binding ratio between the compound and OCl-. The probe also changes from yellow to colorless upon interaction with OCl- in naked-eye. The practical utility of PTH-TH-PY was validated through TLC plate analysis and its ability to detect OCl- in various water samples. Furthermore, the compound's capacity to detect hypochlorite in live HeLa cells indicates its potential application in biological systems. These findings highlight PTH-TH-PY as a promising sensor for real-time OCl- monitoring in diverse settings, including environmental and medical contexts.

Investigation of the synergistic photocatalytic activity of a ternary ZrTiO4/TiO2/Mn3O4 (ZTM) nanocomposite in a typical water treatment process

Because of the exploration of the increase in the aqueous environment caused by various organic pollutants, an urgent need is sensed to develop novel photocatalysts with high efficiency. Here, ZrTiO4/TiO2/Mn3O4 (ZTM) was in-situ synthesized and relatively well-characterized by XRD, FTIR, UV–Vis DRS, EIS, TG/DTG, TPD, SEM, TEM, and BET characterization techniques. Diffraction data showed the crystallite sizes of about 22 and 13 nm obtained by the Scherrer and Williamson-Hall formulas, respectively, with a d-spacing of about 0.21 nm. Then, the composite catalyst was applied in the photodegradation of Metoclopramide (MCP) and showed a boosted photocatalytic activity concerning ZrTiO4, TiO2, and Mn3O4 alone. The effective surface area of 105, 54, and 93 m2/g were obtained in BET analysis of ZTM, Mn3O4, and TiO2. ZTM, Mn3O4, TiO2, and ZrTiO4 band gap energies were obtained via the DRS spectra as 2.22, 1.88, 3.05, and 3.31 eV The scavenging agent's study confirmed that hydroxyl radical and photoinduced electrons have higher roles in the MCP photodegradation process, accordingly confirmed by a sequential direct Z-scheme charge transfer mechanism in the composite.

Enhanced photocatalytic property of Cu doped Ce2Zr2O7 toward photodegradation of methylene blue under visible light

Widespread ecosystem degradation from noxious substances like industrial waste, toxic dyes, pesticides, and herbicides poses serious environmental risks. For remediation of these hazardous problems, present study introduces an innovative Cu-doped Ce₂Zr₂O₇ nano-photocatalyst, fabricated via a simple, eco-friendly hydrothermal method, designed to degrade toxic textile dye methylene blue. Harnessing Cu doping for pyrochlore Ce2Zr2O7, structure engineering carried out through a hydrothermal synthesis method to achieve superior photocatalytic performance, addressing limitations of rapid charge carrier recombination in existing photocatalysts. Photoluminescence analysis showed that doped pyrochlore slows charge carrier recombination, boosting dye degradation efficiency. UV–Visible analysis demonstrated an impressive 96 % degradation of methylene blue by Cu-doped Ce2Zr2O7 within 50 min, far exceeding the performance of pristine materials. Trapping experiments clarified the charge transfer mechanism, deepening our understanding of the photocatalytic process. These findings highlight the potential for developing innovative, highly efficient photocatalysts for environmental remediation, offering sustainable solutions to combat pollution. This study not only addresses the limitations of existing photocatalysts but also opens new avenues for enhancing photocatalytic performance through strategic material design.

Facile Synthesis of Organic-Inorganic Hybrid Heterojunctions of Glycolated Conjugated Polymer-TiO2-X for Efficient Photocatalytic Hydrogen Evolution.

The utilization of the organic-inorganic hybrid photocatalysts for water splitting has gained significant attention due to their ability to combine the advantages of both materials and generate synergistic effects. However, they are still far from practical application due to the limited understanding of the interactions between these two components and the complexity of their preparation process. Herein, a facial approach by combining a glycolated conjugated polymer with a TiO2-X mesoporous sphere to prepare high-efficiency hybrid photocatalysts is presented. The functionalization of conjugated polymers with hydrophilic oligo (ethylene glycol) side chains can not only facilitate the dispersion of conjugated polymers in water but also promote the interaction with TiO2-X forming stable heterojunction nanoparticles. An apparent quantum yield of 53.3% at 365nm and a hydrogen evolution rate of 35.7mmol h-1 g-1 is achieved by the photocatalyst in the presence of Pt co-catalyst. Advanced photophysical studies based on femtosecond transient absorption spectroscopy and in situ, XPS analyses reveal the charge transfer mechanism at type II heterojunction interfaces. This work shows the promising prospect of glycolated polymers in the construction of hybrid heterojunctions for photocatalytic hydrogen production and offers a deep understanding of high photocatalytic performance by such heterojunction photocatalysts.

A hollow core-shell TiO2/NiCo2S4 Z-Scheme heterojunction photocatalyst for efficient hydrogen evolution

Constructing heterojunctions have received significant attention in photocatalysis because of their efficient separation of photogenerated carriers and improving light utilization efficiency. Bimetallic sulfides (e.g. NiCo2S4) are applied in electrocatalysis and supercapacitors that can be coupled with TiO2 to form a heterojunction. Owing to the staggered energy band arrangement between TiO2 and NiCo2S4, the establishing of a Z-scheme heterojunction between them is expected to enhance the carrier separation efficiency and reduce the sulfide photo-corrosion. However, the application of NiCo2S4 in photocatalysis and studies on the mechanism of the TiO2/NiCo2S4 Z-scheme heterojunction have seldom been reported. In this work, we obtained a hollow core-shell TiO2/NiCo2S4 Z-scheme photocatalyst through a solvothermal method for photocatalytic hydrogen evolution (PHE). The PHE rate of the optimized TiO2/NiCo2S4-0.3 is 8.55 mmol g−1 h−1, approximately 34 times higher than pure TiO2, 94 times higher than pure NiCo2S4. The remarkable photocatalytic activity can be ascribed to the hollow structure and the in-situ constructed Z-scheme heterojunction. The photogenerated charge transfer mechanism is revealed by hydroxyl radical trapping experiments and electron paramagnetic resonance (EPR) characterization. The in-situ construction of the Z-scheme heterojunction not only enhances the efficiency of separating the photogenerated carriers but also reduces the photo-corrosion of NiCo2S4. This study proposes an effective strategy for the design of TiO2-based Z-scheme heterojunctions and the application of NiCo2S4 in photocatalysis.

Localized Surface Doping Induced Ultralow Contact Resistance between Metal and (Bi,Sb)2Te3 Thermoelectric Films.

Micro thermoelectric devices are expected to further improve the cooling density for the temperature control of electronic devices; nevertheless, the high contact resistivity between metals and semiconductors critically limits their applications, especially in chip cooling with extremely high heat flux. Herein, based on the calculated results, a low specific contact resistivity of ∼10-7 Ω cm2 at the interface is required to guarantee a desirable cooling power density of micro devices. Thus, we developed a generally applicable interfacial modulation strategy via localized surface doping of thermoelectric films, and the feasibility of such a doping approach for both n/p-type (Bi,Sb)2Te3 films was demonstrated, which can effectively increase the surface-majority carrier concentration explained by the charge transfer mechanism. With a proper doping level, ultralow specific contact resistivities at the interfaces are obtained for n-type (6.71 × 10-8 Ω cm2) and p-type (3.70 × 10-7 Ω cm2) (Bi,Sb)2Te3 layers, respectively, which is mainly attributed to the carrier tunneling enhancement with a narrowed interfacial contact barrier width. This work provides an effective scheme to further reduce the internal resistance of micro thermoelectric coolers, which can also be extended as a kind of universal interfacial modification technique for micro semiconductor devices.