Improved Charge Separation Research Articles

Charge Separation-Engineered Piezoelectric Ultrathin Nanorods Modulate Tumor Stromal Microenvironment and Enhance Cell Immunogenicity for Synergistically Piezo-Thermal-Immune Therapy.

The tumor microenvironment (TME) is characterized by hypoxia and low immunogenicity, with a dense and rigid extracellular matrix (ECM) that impedes the diffusion of therapeutic agents and immune cells, thereby limiting the efficacy of immunotherapy. To overcome these challenges, an oxygen defect piezoelectric-photothermal sensitizer, bismuth vanadate nanorod-supported platinum nanodots (BVP) is developed. The integration of platinum enhances the photothermal effect and improves charge separation efficiency under ultrasound, leading to increased heat generation and the production of reactive oxygen species (ROS) and oxygen. Platinum also catalyzes the conversion of hydrogen peroxide in the TME to oxygen, which serves as both a ROS source and a means to alleviate tumor hypoxia, thereby reversing the immunosuppressive TME. Moreover, the coordination of bismuth ions with glutathione further amplifies cellular oxidative stress. The generated heat and ROS not only denature the collagen in the ECM, facilitating the deeper penetration of BVP into the tumor but also induce immunogenic cell death in tumor cells. Through the "degeneration and penetration" strategy, photoacoustic therapy effectively activates immune cells, inhibiting both tumor growth and metastasis. This study introduces a pioneering approach in the design of antitumor nanomedicines aimed at reversing the immunosuppressive characteristics of the TME.

Visible Light-Driven Photocatalysis of Al-Doped SrTiO3: Experimental and DFT Study

Environmental problems associated with water pollution caused by organic dyes have raised serious concerns. In this context, photocatalytic processes have proven to be promising and environmentally friendly methods for water purification utilising abundant solar energy. In this study, a SrTiO3-based photocatalyst was modified by doping with Al ions and the deposition of dual co-catalysts (Rh/Cr2O3 and CoOOH) to enhance the photocatalytic decomposition efficiency of methylene blue (MB). Pure perovskite SrTiO3 was synthesised by chemical precipitation followed by calcination at 1100 °C. Al-doped SrTiO3 with deposited co-catalysts showed 3.2 times higher photocatalytic activity compared to unalloyed SrTiO3 with co-catalysts in MB decomposition under visible radiation. This study highlights the effectiveness of using dual co-catalysts and low-valence metal doping to enhance the efficiency of the photocatalytic decomposition of organic pollutants. The density functional theory analysis results show that the Al doping of SrTiO3 improves charge separation and increases the lifetime of photogenerated electrons and holes while maintaining the size of the forbidden band, which confirms its effectiveness for enhancing photocatalytic activity.

Pd Nanoparticles Decorated CeZrOx for Enhanced Photocatalytic Hydrogenation of Biomass‐Derived Compounds

The photocatalytic conversion of biomass‐derived compounds into value‐added chemicals presents a promising protocol for the sustainable production of renewable chemicals. Our study explores the hydrogenation of biomass model compounds under visible light illumination. Zr was incorporated into the CeO2 framework, forming a CeZrOx(1:0.5) solid solution, confirmed by powder X‐ray diffraction (PXRD) and X‐ray photoelectron spectroscopy (XPS) analyses. The light uptake capacity of the CeZrOx solid solution was characterized using UV‐visible spectroscopy. Additionally, the band structure of the CeZrOx solid solution was assessed using valance band X‐ray photoelectron spectroscopy (VB‐XPS) and Ultraviolet photoelectron spectroscopy (UPS) analysis, revealing a Z‐Scheme, which was further confirmed by various control experiments. Upon decorating the CeZrOx(1:0.5) solid solution with 1 wt% palladium (Pd), the resulting 1Pd/CeZrOx(1:0.5) composite exhibited improved charge separation and enhanced visible light absorption capacity. This composite achieved ~99% conversion of furfural to tetrahydrofurfuryl alcohol under a 15 W blue LED illumination and 0.2 MPa hydrogen. Similarly, it demonstrated ~99% conversion of benzyl phenyl ether (BPE) to toluene and phenol under a 10 W blue LED illumination. Our findings elucidate the active sites and demonstrate the recyclability of mixed metal oxides for selective furfural hydrogenation and BPE hydrogenolysis under visible light.

Unlocking Topological Effects in Covalent Organic Frameworks for High-Performance Photosynthesis of Hydrogen Peroxide.

Covalent organic frameworks (COFs) offer a compelling platform for the efficient photosynthesis of hydrogen peroxide (H2O2). Constructed with diverse topologies from various molecular building units, COFs can exhibit unique photocatalytic properties. In this study, three π-conjugated 2D sp2 carbon-linked COFs with distinctly different topologies (hcb, sql, and hxl) are designed to investigate the topological effect on the overall photosynthesis of H2O2 from water and oxygen. Despite their similar chemical and band structures, the QP-HPTP-COF with hxl topology outperformed other COFs in the photosynthesis of H2O2, demonstrating a remarkable solar-to-chemical conversion efficiency of 1.41%. Comprehensive characterizations confirmed that the hxl topology can substantially improve charge separation and transfer, thereby significantly enhancing photocatalytic performance. This study not only unravels the topology-directed charge carrier dynamics in COFs but also establishes a molecular engineering framework for developing high-performance photocatalysts for sustainable H2O2 production.

A Facile Microwave-Promoted Formation of Highly Photoresponsive Au-Decorated TiO2 Nanorods for the Enhanced Photo-Degradation of Methylene Blue

The integration of noble metal nanoparticles (NPs) effectively modifies the electronic properties of semiconductor photocatalysts, leading to improved charge separation and enhanced photocatalytic performance. TiO2 nanorods decorated with Au NPs were successfully synthesized using a cost-effective, rapid microwave-assisted method in H2O2 and HF media for methylene blue (MB) degradation under visible light illumination. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 physisorption, and UV–vis spectroscopy were employed to characterize the structures, morphologies, compositions, and photoelectronic properties of the as-synthesized materials. The fusing of Au NPs effectively alters the electronic structure of TiO2, enhancing the charge separation efficiency and improved electrical conductivity. The HF treatment promotes the exposure of the highly reactive (001) and (101) crystalline facets. The improved photocatalytic activity of Au/TiO2, achieving 97% efficiency, is attributed to the surface plasmon resonance (SPR) effect of the Au NPs and the presence of oxygen vacancies. The photodegradation of MB using the TiO2/Au photocatalysts follows pseudo-first-order kinetics, highlighting the enhanced catalytic efficiency of the synthesized nanostructures. The exceptional properties of the binary Au/TiO2 photocatalysts, including the SPR effect, exposed crystallographic faces, and efficient charge carrier separation through a decrease in the recombination of electrons and holes, contribute to the photocatalytic degradation of MB.

Breaking New Grounds: solid-state synthesis of TiO2 – La2O3 – CuO Nanocomposites for degrading Brilliant Green dye under Visible Light

Environmental pollution, particularly from industrial dyes and chemicals, poses a significant threat to ecosystems and human health. Traditional pollution mitigation methods are often inefficient and costly. Photocatalysis has emerged as a promising solution for degrading pollutants using light energy. Titanium dioxide (TiO2) is a widely studied photocatalyst due to its stability, non-toxicity, and strong oxidative power. However, its efficiency is limited by a wide bandgap, restricting absorption to the UV region, and rapid electron-hole recombination. To address these limitations, doping TiO2 with materials like La2O3 and CuO has been explored to enhance its photocatalytic activity under visible light. This study investigates the enhancement of TiO2 nanocomposites by incorporating La2O3 and CuO. X-ray diffraction (XRD) revealed that the nanocomposites retained TiO2's anatase and rutile phases with improved crystallinity. Scanning electron microscopy (SEM) displayed spherical nanoparticles forming agglomerates, typically due to high surface energy. Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) confirmed the presence of La and Cu in the TiO2 matrix. Fourier-transform infrared (FTIR) spectroscopy identified characteristic vibrational modes of Ti–O, La–O, and Cu–O bonds, suggesting strong chemical interactions between dopants and TiO2 lattice. Ultraviolet-visible (UV-Vis) spectroscopy showed a red shift in absorption spectra with La2O3 and CuO addition, reducing the bandgap energy from 3.23 eV (pure TiO2) to 2.27 eV for the TiO2–0.1La2O3–0.2CuO composite. Photoluminescence (PL) spectroscopy indicated improved charge separation and reduced electron-hole recombination rates in the synthesized nanocomposites. Photocatalytic performance was evaluated by degrading Brilliant Green (BG) dye under visible light. The TiO2–0.1La2O3–0.2CuO (TLC0.2) nanocomposite achieved a maximum dye degradation of over 95% after 204 minutes under optimal conditions (C0 = 17 mg/L and a S/L ratio of 1 g/L). Adding the inorganic agent Na2SO4 to this process significantly enhanced photocatalytic activity, increasing degradation from 56% to 95% after 180 min of visible light irradiation under C0 = 20 mg/L and S/L = 0.5 g/L conditions, as it shows a high stability after six reuse cycles. In conclusion, La2O3 and CuO doping significantly enhance TiO2 nanocomposites' crystalline structure, morphology, optical properties, and photocatalytic efficiency, demonstrating their potential for environmental remediation and solar energy conversion.

Unveiling the potential of Au cocatalysts to induce SPR charges on CuO/CdS system for sunlight driven hydrogen production†

Atmospheric pollution and increasing costs of the fossil fuels have compelled the researchers to explore the alternative sources. The objective of current project is to discover the stable catalysts that can drive water splitting reaction with sunlight. To the purpose, visible light active catalysts i.e. CdS, CuO/CdS, and Au@CuO/CdS have been synthesized and evaluated for hydrogen generation activities. Gold cocatalysts have been employed to enhance the surface stability and catalytic efficiencies. Whereas, CuO/CdS heterojunction have been synthesized to improve charge separation ability. The optical characteristics, structural properties, and morphology of catalysts have been evaluated by UV‒Vis/DRS, XRD, Raman, BET, SEM, AFM, PL and FTIR techniques. Chemical compositions, photocurrent or charge transfer have been verified with XPS, EDX and EIS results. Catalytic reactions were performed in photoreactor (150mL/Pyrex), whereas hydrogen production activities were predicted via online GC-TCD (Shimadzu-2010/Japan). Results depict that catalyst with 0.8% of Au on CuO/CdS exhibit relatively higher activity (i.e. 32.13 mmolg‒1h‒1) than the other catalysts of the series. Higher activities were attributed to the presence of Au cocatalysts. It has been predicted that coexistence of gold develops Schottky junctions that progressively rectify the surface charges (i.e. movement of electrons). Additionally, gold induces the SPR charges and enhances activity of electrons. Schottky junctions formed by Au cocatalysts on CuO/CdS system restrict the charge recombination i.e. back reactions. In this study, various factors like temperature, pH, light intensity and dose of catalysts have been assessed and discussed. On the basis of activities, it has been concluded that work reported herein hold promise to replace the conventional catalysts used for hydrogen energy technologies.

Enhanced Visible‐Light‐Driven Photocatalytic Overall Splitting of Pure Water in a Porous Microreactor

AbstractPhotocatalytic overall splitting of pure water (H2O) without sacrificial reagent to hydrogen (H2) and oxygen (O2) holds a great potential for achieving carbon neutrality. Herein, by anchoring cobalt sulfide (Co9S8) as cocatalyst and cadmium sulfide (CdS) as light absorber to channel wall of a porous polymer microreactor (PP12), continuous violent H2 and O2 bubbling productions from photocatalytic overall splitting of pure H2O without sacrificial reagent is achieved, with H2 and O2 production rates as high as 4.41 and 2.20 mmol h−1 gcat.−1 respectively. These are significantly enhanced than those in the widely used stirred tank‐type reactor in which no O2 is produced and H2 production rate is only 0.004 mmol h−1 gcat.−1. Besides improved charge separation and interaction of H2O with photocatalyst in PP12, bonding interaction of Co9S8 with PP12 creates abundant catalytic active sites for simultaneous productions of H2 and O2, thus leading to the significantly enhanced H2 and O2 bubbling productions in PP12. This offers a new strategy to enhance photocatalytic overall splitting of pure H2O without sacrificial reagent.

Multifunctional Conductive MOFs Enhance the Photocatalytic Hydrogen Evolution Efficiency of S-Type Ni3(HITP)2/TiO2 Heterojunctions.

Despite their high surface area, remarkable porosity, and efficient charge transfer mechanisms, conductive MOFs have found limited utilization within the domain of photocatalysis. In this study, we synthesized a cutting-edge S-type Ni3(HITP)2/TiO2 heterojunction photocatalyst exhibiting outstanding light harvesting and prolonged lifetime of photogenerated electrons through an in situ synthesis approach. Compared with TiO2, the composite materials not only significantly increase the specific surface area by 4.07 times but also expand the visible light absorption edge from 400 to 1100 nm. The hydrogen production rate of Ti/Ni-3 reached 4.927 mmol·g-1·h-1, which is 4.51 times that of TiO2. The S-type interface charge transfer pathway of the Ni3(HITP)2/TiO2 composite material was inferred by band structure, in situ XPS, SPV, and free radical capture, which improves charge separation and extends the carrier lifetime to undergo directional migration driven by an IEF. This is the main reason for the improved photocatalytic performance of Ni3(HITP)2/TiO2 composite materials.

Tailoring CoAl2O4 inversion degree-driven photocarrier separation and injection for photoelectrochemical water splitting

Highly efficient photoanodes are highly desirable for hydrogen production to construct photoelectrochemical (PEC) water oxidation devices. This work used the spinel-structured CoAl2O4 (CAO) as the cocatalysts to BiVO4(BVO), delivering the high photocurrent density of 3.85 mA/cm2 at 1.23 VRHE. Interestingly, their PEC performance depended on the CAO's inversion degree (δ). When δ = 0.2, the oxygen evolution process on CAO can cooperatively adsorb *OOH and dissociate the O2, then the *OH absorbs on the re-exposed active site again, leading to an improved charge separation on the surface. Meanwhile, the n-p heterojunction was formed at the interface of BVO/CAO, with the most robust built-in field strength at δ = 0.2, and the charge separation in bulk was greatly improved. Additionally, the CAO can also retard the photo corrosion of BVO by effectively extract and reservoir the photoholes, achieving over 10 h of long-term durability on BVO/CAO-450. This work illustrates the roles of CAO, clarifies the effect of inversion degree on PEC water oxidation, offers fresh insights into constructing highly efficient and stable OER catalysts, and provides fundamentals for developing high-efficiency PEC devices.

A hybrid MAPbI3/PEDOT-ZrO2 perovskedot composite for enhanced stability and charge transport in photo-batteries

Designing flexible photo-batteries that are capable of charged directly by light is critical for improving off-grid power options. This paper presents a unique photo-battery design that uses a MAPbI3/PEDOT as the effective light-harvesting and hole-transporting layer, and zirconium oxide (ZrO2) as the channel for electrons and hole-blocking layer. The MAPbI3 perovskite material absorbs sunlight and develops charge carriers, while PEDOT helps transport holes to the anode, improving charge separation and minimizing recombination losses. ZrO2, with its strong electron mobility and great chemical stability, provides fast transport of electrons to the cathode. It also efficiently blocks holes, increasing overall charge transfer dynamics. This improved design improves photo-conversion efficiency by up to 0.51 % and has a high capacity retention rate of around 96 % after 500 cycles. This improved MAPbI3/PEDOT/ZrO2 photo-battery could decrease light charging time by three times, enabling adaptable, light-rechargeable batteries more practical for real-world applications.

Elucidating the Advancement in the Optoelectronics Characteristics of Benzoselenadiazole-Based A2-D-A1-D-A2-Type Nonfullerene Acceptors for Efficient Organic Solar Cells.

The potential applications of nonfullerene acceptors (NFAs) such as tunable band gaps, improved charge separation, wide-range absorption, enhanced power conversion efficiency, and operational stability make them highly favorable for organic photovoltaic applications. Herein, we designed eight novel structurally modified nonfused benzoselenadiazole (BSe)-based A2-D-A1-D-A2-type NFAs for efficient organic solar cells (OSCs). These newly modeled BSe-based NFA series contain BSe as the central core. We employed strong electron-withdrawing moieties at terminal acceptor A2 to further enhance the optical, optoelectronics, and photovoltaic characteristics of OSCs. These designed molecules (HNM1-HNM8) along with the synthetic reference molecule (HNM) were thoroughly characterized by using efficient and advanced quantum chemical simulation approaches. Thus, to ascertain the enhancement of both optical and photochemical response, a thorough density functional theory (DFT) study was carried out using the M062X level in association with the 6-31G(d,p) basis set. All of the investigated molecules (HNM1-HNM8) had their excited states calculated using the time-dependent density functional theory method. The newly designed molecules (HNM1-HNM8) presented narrower band gaps, improved absorption and optoelectronics properties, and reduced excitation and binding energies. The electrostatic potential, density of states, transition density matrix, ionization potential, and electron affinity analysis of this newly designed (HNM1-HNM8) series revealed a strong coherence with those of the reference HNM molecule. Electron density difference mapping allowed us to visualize the spatial movement of electrons between the donor and acceptor molecules during excitation. This insight helps us to understand the efficiency of charge separation and recombination processes that are critical for the performance of organic photovoltaics. The reorganization energy and charge transfer analysis suggests that HNM1-HNM8 molecules could act as NFAs for organic photovoltaic applications to enhance their efficiency further. The donor: acceptor charge transfer analysis was also carried out, which revealed that the PTB7-Th:HNM2 donor:acceptor complex shows a great charge transportation process at the donor-acceptor interface. Moreover, the photovoltaic analysis shows that the designed (HNM1-HNM8) NFA series has a great potential to produce improved open-circuit voltage and fill factor values, which may be helpful in enhancing the overall PCEs of the OSCs.

Efficient Photocatalytic Hydrogen Evolution via Cocatalyst Loaded Al-doped SrTiO3

The growing reliance on fossil fuels is causing significant environmental issues, prompting the search for renewable energy sources. Hydrogen energy, which produces only water vapor, is a promising solution. This study focuses on developing an aluminum-doped SrTiO3 photocatalyst with dual cocatalysts (Rh/Cr2O3 and CoOOH) for efficient photocatalytic water splitting. Using a simple chemical deposition method, high-purity and crystalline SrTiO3 was synthesized and thoroughly characterized. The results show that the modified SrTiO3 achieved significantly higher photocatalytic activity, with Rh/Cr2O3/SrTiO3@Al/CoOOH producing 11.04 mmol g–1 h–1 of H2 and 4.69 mmol g–1 h–1 of O2. This work demonstrates the effectiveness of dual cocatalyst deposition and aluminum doping in enhancing photocatalytic performance by improving charge separation and reducing recombination.

Yolk-Shell TiO2-NRs@SiO2 with enhanced photocatalytic hydrogen production

The efficiency of photocatalysis largely hinges on the design of the photocatalysts, which can be optimized for effective light absorption, improved charge separation and transport, and faster surface reactions. In this research, we developed a yolk-shell nanostructured photocatalyst featuring one-dimensional TiO2 nanorods (NRs) cores encapsulated within a porous silica shell. After photodepositing Pt nanoparticles (NPs) onto the TiO2-NRs, the photocatalyst exhibited excellent performance. Under simulated sunlight, Pt2-TiO2-NRs@SiO2 achieved a photocatalytic efficiency of 55.47 mmol g-1h−1 using methanol as the sacrificial agent and an apparent quantum efficiency (AQE) of 7.93 % at 350 nm, surpassing most previously reported TiO2-based catalysts. This superior activity is attributed to 1D NRs, along with the hollow structure that enhances light utilization through multiple scattering. The stability and high catalytic performance of these yolk-shell structures highlight the effectiveness of our design strategy in fabricating novel, highly active, and stable catalysts.

Enhanced CO2 Reduction via S-Scheme Heterojunction of Amorphous/Crystalline Metal-free Carbon Nitride Photocatalysts

Metal-free carbon nitride nanosheets (CNs) are promising photocatalysts, but face challenges with severe charge recombination and limited visible light absorption. To overcome these challenges, we have developed a 2D/2D amorphous/crystalline carbon nitride (CNs/CCN) S-scheme heterojunction photocatalyst through electrostatic self-assembly. The built-in electric field in the CNs/CCN heterojunction facilitates an S-scheme transfer of photogenerated electrons from CCN to CNs, effectively enhancing electron-hole separation. Our optimized CNs/CCN-1/3 heterojunction exhibits substantially higher production rates of CO and CH4 compared to its individual components. Notably, CNs/CCN-1/3 maintains excellent CO2 reduction efficiency even under irradiation at wavelengths exceeding 700 nm. This study introduces an innovative strategy for the development of CNs-based photocatalysts with improved charge separation and enhanced visible-light absorption.

Adjusting the Covalency of Metal-Oxygen Bonds in CuBi2O4 by Zn Cation Doping to Achieve Highly Efficient Photocathodes.

Zn doped CuBi2O4 photocathodes are prepared by using a low-cost solution-based spray pyrolysis method. The doping of Zn in CuBi2O4 promotes the separation and migration of carriers and effectively increases the carrier density. Compared with CuBi2O4 alone, the photoelectrochemical activity of the Zn doped CuBi2O4 photoelectrode is improved with the photocurrent density of -0.56 mA/cm2 at 0.4 V vs. RHE. This improvement is due to the lower electronegativity of Zn, which leads to the covalent increase of Cu-O and Bi-O bonds in CuBi2O4, which limits the recombination of photogenerated electrons and holes and improves charge separation and transport. This study presents an innovative approach to enhance the charge separation efficiencies of photocathodes by implementing element doping strategies, which may contribute to further research on photocatalytic water splitting.

Surface Optimization of Noble-Metal-Free Conductive [Mn1/4Co1/2Ni1/4]O2 Nanosheets for Boosting Their Efficacy as Hybridization Matrices.

Conductive 2D nanosheets have evoked tremendous scientific efforts because of their high efficiency as hybridization matrices for improving diverse functionalities of nanostructured materials. To address the problems posed by previously reported conductive nanosheets like poorly-interacting graphene and cost-ineffective RuO2 nanosheets, economically feasible noble-metal-free conductive [MnxCo1-2xNix]O2 oxide nanosheets are synthesized with outstanding interfacial interaction capability. The surface-optimized [Mn1/4Co1/2Ni1/4]O2 nanosheets outperformed RuO2/graphene nanosheets as hybridization matrices in exploring high-performance visible-light-active (λ>420nm) photocatalysts. The most efficient g-C3N4-[Mn1/4Co1/2Ni1/4]O2 nanohybrid exhibited unusually high photocatalytic activity (NH4 + formation rate: 1.2mmol g-1 h-1), i.e., one of the highest N2 reduction efficiencies. The outstanding hybridization effect of the defective [Mn1/4Co1/2Ni1/4]O2 nanosheets is attributed to the optimization of surface bonding character and electronic structure, allowing for improved interfacial coordination bonding with g-C3N4 at the defect sites. Results from spectroscopic measurements and theoretical calculations reveal that hybridization helps optimize the bandgap energy, and improves charge separation, N2 adsorptivity, and surface reactivity. The universality of the [Mn1/4Co1/2Ni1/4]O2 nanosheet as versatile hybridization matrices is corroborated by the improvement in the electrocatalytic activity of hybridized Co-Fe-LDH as well as the photocatalytic hydrogen production ability of hybridized CdS.

Synergy of S doping and defect construction in holey ultra-thin g-C3N4 nanosheets for improved photocatalytic hydrogen production from water

Combining the advantages of multiple strategies including morphology control, atom doping, and defect construction, the photocatalytic hydrogen evolution reaction (HER) performance of graphitic carbon nitride (g-C3N4) may be boosted significantly. Herein, holey ultra-thin g-C3N4 nanosheets (CNS-x, x = H, O, N) modified with structural vacancies and sulfur (S) dopant are synthesized through a straightforward method involving the pyrolysis of thiocyanuric acid under various gas atmospheres. The textural properties, type and concentration of structural defect, and S doping level are significantly influenced by the gas atmosphere. Remarkably, CNS-H with C, N dual defects and S-dopant exhibits the HER rate of 46.59 mmol·g−1·h−1, which is 16.68 times higher than that of bulk g-C3N4. The corresponding apparent quantum yields are 17.24 % at 420 nm and 1.90 % at 520 nm. The enhanced HER performance of CNS-H can be attributed to the combined effect of improved charge separation, extended photoabsorption, and optimized properties of the platinum cocatalyst.

Z-scheme heterostructure of ZnO@NPC/Au/ZnIn2S4 for chemical replacement reaction-mediated signal-on photoelectrochemical assay of mercury ion

Herein, an advanced Zn-based metal organic framework (Zn-MOF) derived ZnO embedded in a nitrogen-doped porous carbon (ZnO@NPC) polyhedron/Au/ three-dimensional (3D) chrysanthemum-like ZnIn2S Z-scheme heterojunction was employed for the chemical replacement reaction-mediated signal-on photoelectrochemical (PEC) sensing detection of mercury ions (Hg2+). The p-type ZnO@NPC polyhedron was initially prepared by carbonising the zeolitic imidazolate framework (ZIF)-8 polyhedron, followed by modification with Au nanoparticles (NPs) via an in situ photocatalytic reduction method. Subsequently, the ZnO@NPC/Au polyhedron was combined with n-type 3D chrysanthemum-like ZnIn2S4 through physical adsorption, forming the ZnO@NPC polyhedron/Au/3D chrysanthemum-like ZnIn2S4 Z-scheme heterostructure. The newly constructed heterostructure exhibited strong visible light–harvesting capacity, and considerably improved photoelectric conversion efficiency. The 3D chrysanthemum-like ZnIn2S4 functioned not only as a photosensitiser but also as an Hg2+ recognition probe. Importantly, the PEC sensor exhibited a considerably increased photocurrent response to Hg2+. This is presumably because the introduction of Hg2+ triggered a selective Zn-to-Hg chemical replacement reaction, leading to the in-situ formation of a ZnO@NPC/Au/ZnIn2S4/HgS heterojunction, which further improved charge separation. Consequently, Hg2+ was sensitively detected with a wide linear range from 0.5 pM to 2 μM and a low detection limit of 0.07 pM. Furthermore, the proposed sensor was validated by detecting Hg2+ in food and aqueous environments, indicating its potential application in food safety and environmental monitoring.

Charge carrier dynamics of chemical vapor deposited carbon-doped titanium dioxide photoanodes

This study explores the synthesis of carbon-doped titanium dioxide TiO2(C) photoanodes through a single-step, low-pressure chemical vapor deposition (LCPVD) method, investigating the influence of carbon doping and oxygen vacancies on photoelectrochemical performance. The research employs morphological, structural, and photoelectrochemical characterization methods, including intensity-modulated photocurrent spectroscopy (IMPS) and distribution of relaxation times (DRT) analysis. We correlate the simultaneous presence of surface carbon and oxygen defects to improved charge separation and collection for TiO2(C) photoanodes. This work provides a comprehensive and detailed explanation of the photoelectrochemical performance of TiO2 electrodes, showing the potential behind combined IMPS-DRT analysis for photoelectrode characterization.