Photoelectrochemical Research Articles

Photoelectrocatalytic Hydrogen Generation: Current Advances in Materials and Operando Characterization.

Photoelectrochemical (PEC) hydrogen generation is a promising technology for green hydrogen production yet faces difficulties in achieving stability and efficiency. The scientific community is pushing toward the development of new electrode materials and a better understanding of the underlying reactions and degradation mechanisms. Advances in photocatalytic materials are being pursued through the development of heterojunctions, tailored crystal nanostructures, doping, and modification of solid-solid and solid-electrolyte interfaces. Operando and in situ techniques are utilized to deconvolute the charge transfer mechanisms and degradation pathways. In this review, both materials development and Operando characterization are covered for advancing PEC technologies. The recent advances made in the PEC materials are first reviewed including the applied improvement strategies for transition metal oxides, nitrites, chalcogenides, Si, and group III-V semiconductor materials. The efficiency, stability, scalability, and electrical conductivity of the aforementioned materials along with the improvement strategies are compared. Next, the Operando characterization methods and cite selected studies applied for PEC electrodes are described. Operando studies are very successful in elucidating the reaction mechanisms, degradation pathways, and charge transfer phenomena in PEC electrodes. Finally, the standing challenges and the potential opportunities are discussed by providing recommendations for designing more efficient and electrochemically stable PEC electrodes.

Study on the Preparation and PEC-Type Photodetection Performance of β-Bi2O3 Thin Films.

Bismuth-based compounds have been regarded as a kind of promising material due to their narrow bandgap, high carrier mobility, low toxicity, and strong oxidation ability, showing potential applications in the field of photoelectrochemical (PEC) activities. They can be applied in sustainable energy production, seawater desalination and treatment, optical detection and communication, and other fields. As a member of the broader family of bismuth-based materials, β-Bi2O3 exhibits significant advantages for applications in engineering, including high photoelectric response, stability in harsh environments, and excellent corrosion resistance. This paper presents the synthesis of β-Bi2O3 thin films utilizing the mist chemical vapor deposition (CVD) method at the optimal temperature of 400 °C. Based on the β-Bi2O3 thin film synthesized at optimal temperature, a PEC-type photodetector was constructed with the highest responsivity R of 2.84 mA/W and detectivity D of 6.01 × 1010 Jones, respectively. The photodetection performance was investigated from various points like illumination light wavelength, power density, and long-term stability. This study would broaden the horizontal and practical applications of β-Bi2O3.

Regulating coordinatively unsaturated Co active sites in TA@ZIF-L(Co) via tannic acid for efficient photoelectrochemical water oxidation

Metal-organic frameworks (MOFs) as a cocatalyst can enhance the photoelectrochemical (PEC) water oxidation performance to a certain extent, but still suffer from deficient exposure of active sites and low electron mobility. In this work, 2D Leaf-like zeolitic imidazolate frameworks (ZIF-L) were selected as a precursor for the generation of defective structures by tannic acid (TA) functionalization-assisted etching, and then coupling it with BiVO4 to prepare a novel and highly efficient TA@ZIF-L(Co)/BiVO4 photoanode by a simple impregnation method. The photocurrent density of TA@ZIF-L(Co)/BiVO4 composite photoanode achieves 4.21 mA cm−2 at 1.23 VRHE under AM 1.5 G illumination, which is superior to that of ZIF-L(Co)/BiVO4, and three times that of the bare BiVO4, with a charge injection efficiency of up to 80 %, and its stability is also remarkably improved. Experimental results and DFT calculations showed that the introduction of TA not only improved the light absorption efficiency, but also exposed more active sites, increased the electron density of the coordinatively unsaturated Co active sites, and enhanced the polarized electric field on the surface, thus accelerating electron mobility. This work demonstrates that TA as a surface modifier has great potential to activate metal sites and change the electronic environment of MOFs for BiVO4-based photoanode in PEC water oxidation, providing valuable insights into the rational design of photoanodes.

Quasi-homogeneous photoelectrochemical organic transformations for tunable products and 100% conversion ratio

Photoelectrochemical (PEC) organic transformation at the anode coupled with cathodic H2 generation is a potentially rewarding strategy for efficient solar energy utilization. Nevertheless, achieving the full conversion of organic substrates with exceptional product selectivity remains a formidable hurdle in the context of heterogeneous catalysis at the solid/liquid interface. Here, we put forward a quasi-homogeneous catalysis concept by using the reactive oxygen species (ROS), such as ·OH, H2O2 and SO4•−, as a charge transfer mediator instead of direct heterogeneous catalysis at the solid/liquid interface. In the context of glycerol oxidation, all ROS exhibited a preference for first-order reaction kinetics. These ROS, however, showcased distinct oxidation mechanisms, offering a range of advantages such as ∼ 100 % conversion ratios and the flexibility to tune the resulting products. Glycerol oxidative formic acid with Faradaic efficiency (FE) of 81.2 % was realized by the H2O2 and ·OH, while SO4•− was preferably for glycerol conversion to C3 products like glyceraldehyde and dihydroxyacetone with a total FE of about 80 %. Strikingly, the oxidative coupling of methane to ethanol was successfully achieved in our quasi-homogeneous system, yielding a remarkable production rate of 12.27 μmol h−1 and an impressive selectivity of 92.7 %. This study is anticipated to pave the way for novel approaches in steering solar-driven organic conversions by manipulating ROS to attain desired products and conversion ratios.

Nature-imitating optimized photoelectrochemical process in BiSe nanosheets-based photodetectors

Nature-imitating optimized photoelectrochemical process in BiSe nanosheets-based photodetectors

Room-temperature electrodeposition of Cu2O layers and its low-temperature annealing for photoelectrochemical water splitting applications

Cuprous oxide layers were obtained on a conductive glass substrate via room-temperature electrochemical deposition from the electrolyte containing 0.4 M CuSO4, 3 M lactic acid (pH = 12) at −0.5 V vs. SCE for various durations (from 0.25 to 3 h). Physicochemical properties of as-received FTO/Cu2O materials were characterized using SEM, PXRD, and UV–Vis DRS. The photoelectrochemical (PEC) properties of the obtained electrodes were evaluated in detail by analyzing the influence of the energy of monochromatic radiation, and the applied polarization on the resulting photocurrent transients. It was found that Cu2O crystals are getting bigger and sharper with prolonged electrosynthesis duration and a slight decrease in the band gap energy from 2.4 to 2.1 eV with increasing deposition duration was observed. Moreover, this trend was also reflected in PEC properties of resulted material, higher photocurrents were generated by the material deposited for 3 h. More importantly, this PEC response was enhanced by low-temperature (100 °C, 200 °C) annealing. Thermal treatment at 100 °C led to a noticeable improvement in the photoactivity of the samples. Further increasing post-treatment temperature to 200 °C resulted in a further six-fold increase in photocurrents. Finally, the calculated values of accumulated and dissipated charges indicated significantly lower surface recombination after thermal treatment.

Photoelectrochemical sensor for nitrite determination based on the etching of BiOCl/Zn0.5Cd0.5S

A rapid photoelectrochemical (PEC) sensor was constructed for nitrite detection in food based on the one-step chemical etching strategy of BiOCl/Zn0.5Cd0.5S (BOC/ZCS) nanocomposites by nitrite. BOC/ZCS heterojunction was prepared by a simple coprecipitation method, and it was found that BOC/ZCS showed significant photoelectrochemical (PEC) activity. The results of this study confirmed that the decrease in the photocurrent of the sensor was linked to the etching of ZCS by nitrite under acidic conditions. Under optimized conditions, the BOC/ZCS-based PEC sensor showed good analytical properties for detecting nitrite, with linear ranges of 1–100 μM and 100–600 μM. The detection limit of the sensor was 0.41 μM (S/N = 3). Excellent repeatability, reproducibility, low background noise, and immunity to interference were demonstrated using the proposed system, and satisfactory results were achieved for the nitrite assay using real samples. These results demonstrate a new method for nitrite detection developed using the proposed PEC sensor.

Salt removal from coal flotation product filter cakes using counter-current and displacement washing

Water reuse is a common practice to alleviate water scarcity concerns and mitigate their environmental footprint in coal processing facilities. Nevertheless, water reuse leads to the accumulation of various organic and inorganic substances, including salt and residual reagents in the processing water, potentially leading to the retention of soluble impurities within the coal product. Residual impurities may result in a reduction in the quality of coal products. Salt and moisture retention has become a common issue on-site, but there lacks a proper solution currently. To resolve this industrial problem, investigations were carried out for the effects of washing on removing inorganic impurities from the cake during filtration. Filter cakes were prepared from flocculated metallurgical coal in process water. Two washing methods were trialled namely counter-current washing and displacement washing. Regarding washing efficiency, counter-current washing tended to produce cakes with higher specific resistance, which caused longer filtration time. Displacement washing, however, showed increased filtration time, though to a lesser extent. In addition, washing with different washing liquid ratios for multiple wash cycles showed that the filtration time, specific cake resistance, and medium resistance increased with the number of wash cycles. The analysis of the filtrate indicated that utilising a strategy of displacement washing with a washing ratio of 1:20 yielded the most effective removal of salt. The filter cakes were analysed using the μCT imaging technique to gain insights into the pore structure of the cake at a microscopic level. There was a significant change in the cake structure, where the pore profile was more evenly distributed and smaller when the cake was washed by displacement washing.

Global assessment of production benefits and risk reduction in agroforestry during extreme weather events under climate change scenarios

Climate change and extreme weather events are threatening agricultural production worldwide. The anticipated increase in atmospheric temperature may reduce the potential yield of cultivated crops. Agroforestry is regarded as a climate-resilient system that is profitable, sustainable, and adaptable, and has strong potential to sequester atmospheric carbon. Agroforestry practices enhance agroecosystems’ resilience against adverse weather conditions via moderating extreme temperature fluctuations, provisioning buffers during heavy rainfall events, mitigating drought periods, and safeguarding land resources from cyclones and tsunamis-type events. Therefore, it was essential to comprehensively analyze and discuss the role of agroforestry in providing resilience during extreme weather situations. We hypothesized that integrating trees in to the agro-ecosystems could increase the resilience of crops against extreme weather events. The available literature showed that the over-story tree shade moderates the severe temperature (2–4°C) effects on understory crops, particularly in the wheat and coffee-based agroforestry as well as in the forage and livestock-based silvipasture systems. Studies have shown that intense rainstorms can harm agricultural production (40–70%) and cause waterlogging. The farmlands with agroforestry have been reported to be more resilient to heavy rainfall because of the decrease in runoff (20–50%) and increase in soil water infiltration. Studies have also suggested that drought-induced low rainfall damages many crops, but integrating trees can improve microclimate and maintain crop yield by providing shade, windshield, and prolonged soil moisture retention. The meta-analysis revealed that tree shelterbelts could mitigate the effects of high water and wind speeds associated with cyclones and tsunamis by creating a vegetation bio-shield along the coastlines. In general, existing literature indicates that implementing and designing agroforestry practices increases resilience of agronomic crops to extreme weather conditions increasing crop yield by 5–15%. Moreover, despite its widely recognized advantages in terms of resilience to extreme weather, the systematic documentation of agroforestry advantages is currently insufficient on a global scale. Consequently, we provide a synthesis of the existing data and its analysis to draw reasonable conclusions that can aid in the development of suitable strategies to achieve the worldwide goal of adapting to and mitigating the adverse impacts of climate change.

Research Progress of Biosensor Based on Organic Photoelectrochemical Transistor.

In order to solve the food safety problem better, it is very important to develop a rapid and sensitive technology for detecting food contamination residues. Organic photoelectrochemical transistor (OPECT) biosensor rely on the photovoltage generated by a semiconductor upon excitation by light to regulate the conductivity of the polymer channels and realize biosensor analysis under zero gate bias. This technology integrates the excellent characteristics of photoelectrochemical (PEC) bioanalysis and the high sensitivity and inherent amplification ability of organic electrochemical transistor (OECT). Based on this, OPECT biosensor detection has been proven to be superior to traditional biosensor detection methods. In this review, we summarize the research status of OPECT biosensor in disease markers and food residue analysis, the basic principle, classification, and biosensing mechanism of OPECT biosensor analysis are briefly introduced, and the recent applications of biosensor analysis are discussed according to the signal strategy. We mainly introduced the OPECT biosensor analysis methods applied in different fields, including the detection of disease markers and food hazard residues such as prostate-specific antigen, heart-type fatty acid binding protein, T-2 toxin detection in milk samples, fat mass and objectivity related protein, ciprofloxacin in milk. The OPECT biosensor provides considerable development potential for the construction of safety analysis and detection platforms in many fields, such as agriculture and food, and hopes to provide some reference for the future development of biosensing analysis methods with higher selectivity, faster analysis speed and higher sensitivity.

Oxygen-Vacancy-Induced Enhancement of BiVO4 Bifunctional Photoelectrochemical Activity for Overall Water Splitting.

Hydrogen generation via photoelectrochemical (PEC) overall water splitting is an attractive means of renewable energy production so developing and designing the cost-effective and high-activity bifunctional PEC catalysts both for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) has been focused on. Based on first-principles calculations, we propose a feasible strategy to enhance either HER or OER performance in the monoclinic exposed BiVO4 (110) facet by the introduction of oxygen vacancies (Ovacs). Our results show that oxygen vacancies induce charge rearrangements, which enhances charge transfer between active sites and adatoms. Furthermore, the incorporation of oxygen vacancies reduces the work function of the system, which makes charge transfer from the inner to the surface more easily; thus, the charges possess stronger redox capacity. As a result, the Ovac reduces both the hydrogen adsorption-free energy (ΔGH*) for the HER and the overpotential for the OER, facilitating the PEC activity of overall water splitting. The findings provide not only a method to develop bifunctional PEC catalysts based on BiVO4 but also insight into the mechanism of enhanced catalytic performance.

Facile Exfoliation of Few-Layer Sn-Based Nanosheets for Self-Powered Photo-Electrochemical and All-Optical Modulation Applications.

Few-layer tin (Sn)-based nanosheets (NSs) with a thickness of ≈2.5nm are successfully prepared using a modified liquid phase exfoliation (LPE) method. Here the first exploration of photo-electrochemical (PEC) and nonlinear properties of Sn NSs is presented. The results demonstrate that the PEC properties are tunable under different experimental conditions. Additionally, Sn NSs are shown to exhibit a unique self-powered PEC performance, maintaining a good long-term stability for up to 1 month. Using electron spin resonance, active species, such as hydroxyl radicals (·OH), superoxide radicals (·O2 -), and holes (h+), are detected during operations, providing a deeper understanding of the working mechanism. Furthermore, measurements of nonlinear response reveal that Sn NSs can be effective for all-optical modulation, as it enables the realization of all-optical switching through excitation spatial cross-phase modulation (SXPM). These findings present new research insights and potential applications of Sn NSs in optoelectronics.

Overstory and fuel traits drive moisture dynamics of mesophytic and pyrophytic leaf litter and 10-h woody debris fuels in a mixed longleaf pine-hardwood woodland

BackgroundFollowing decades of fire exclusion, many open pine and oak forests across the central and eastern US are shifting to closed-canopy forests that are increasingly dominated by shade-tolerant, fire-sensitive species (i.e., mesophytes). As mesophytes encroach into historically pyrophytic landscapes, changes in crown traits and understory microclimate may interact with fine fuel traits to influence fuel moisture retention, and ultimately, fire behavior. To better understand potential interactions among overstory trees and underlying fine fuels that occur during mesophyte encroachment, we measured in situ drying rates of leaf litter and 10-h woody debris of three functional groups (pyrophytic pine, pyrophytic oak, and mesophytic oak) in gaps and beneath overstory trees of each functional group within a longleaf pine-mixed oak woodland along with crown (area, volume, cover), leaf litter (curling, thickness, specific leaf area, volume), and woody debris (density) traits of each functional group and understory microclimate (vapor pressure deficit (VPD)).ResultsWe found that leaf litter from pyrophytic and mesophytic oaks had higher initial moisture content than pyrophytic pines, but pyrophytic pine and pyrophytic oak leaf litter dried 1.5 times faster than that of mesophytic oaks, likely due to their greater leaf curl, thickness, and volume. Initial moisture content of mesophytic oak woody fuels was lower than that of pyrophytic pine and pyrophytic oak, potentially because of higher wood density, but there were no differences in fuel drying rates. Regardless of fuel functional type, leaf litter and woody fuels dried 1.5 times faster in gaps and underneath pyrophytic pine compared to mesophytic oaks, likely due to the more open conditions in these areas. Notably overstory functional group and time of the day interacted to influence VPD, with VPD increasing throughout the day for all groups, but more so for gaps and beneath pyrophytic pines than either oak functional group.ConclusionsThus, fuel and crown traits differentially impacted understory microclimate and leaf litter and 10-h woody debris drying rates, leading to slower drying of fuels of encroaching mesophytes compared to pyrophytic pines and oaks, which could lead to reduced forest flammability, and consequently, the continued encroachment of mesophytic species into fire-dependent pine and oak forests.

Triple quenching effect of nanozyme catalyzed precipitation combined with enzyme-free amplification for photoelectrochemical biosensing of circulating tumor DNA

In this work, a new photoelectrochemical (PEC) biosensor based on triple quenching effect of nanozyme catalyzed precipitation to PEC signal of MgIn2S4 was constructed for ultrasensitive detection of circulating tumor DNA (ctDNA). Enzyme-free amplification technology was used to convert target ctDNA into a large number of product chains (PC) to improve the detection sensitivity. Co3O4 nanozyme with excellent peroxidase (POD)-like activity was introduced to the surface of MgIn2S4 by PC. Co3O4 could oxidize chromogenic agent 3-Amino-9-ethylcarbazole (AEC) to produce red insoluble precipitation in the presence of H2O2, resulting in the PEC signal “off” of MgIn2S4 to achieve ultrasensitive detection of ctDNA. In particular, Co3O4 nanozyme showed three synergistic quenching effects on PEC signal of MgIn2S4, which contributed greatly to improving the detection sensitivity. Firstly, the light absorption range of Co3O4 could reach 1000 nm, and compete with MgIn2S4 for light absorption. Secondly, the produced red precipitation belonged to the insulating material and had large electrochemical impedance, which hindered the transmission of photogenerated carriers. Thirdly, the precipitation also prevented the electron donor ascorbic acid (AA) from transferring electrons to MgIn2S4. This biosensor provided a promising sensitive PEC detection technology for ctDNA, and further broadened the application of nanozymes in the field of PEC analysis.

Anodized commercial galvanized grids decorated with Ag nanospheres and Cu worm-like nanorods for photoelectrochemical water splitting

The current work introduces novel and low-cost AgNSs-A@CGGs and CuNRs-A@CGGs photoanodes for the photoelectrochemical (PEC) water-splitting reaction. The photoanodes were fabricated by anodizing commercial galvanized grids(A@CGGs) in the sodium carbonate solution followed by deposition of Ag or Cu through a simple electroless substitution. Surface studies showed that AgNSs-A@CGGs and CuNRs-A@CGGs photoanodes have a unique morphology including Ag nanospheres (AgNSs) and Cu worm-like nanorods (CuNRs) with huge surface area. The UV-VIS diffuse reflectance spectra (DRS) of AgNSs-A@CGGs and CuNRs-A@CGGs photoanodes displayed the lower band gap energies of 2.4 eV, and 2.83 eV respectively, which compared to 3.91 eV for the A@CGGs, showing excellent photoanodic behavior for AgNSs-A@CGGs and CuNRs-A@CGGs photoanodes. Investigations of photoelectrochemical water-splitting under visible light irradiation showed that the production amount of H2 from AgNSs-A@CGGs and CuNRs-A@CGGs photoanodes was about 18570 and 6895 μmol h−1 cm−2 respectively. Moreover, AgNSs-A@CGGs showed 15.27 and 5.0 times higher photoconversion efficiency than CGGs and A@CGGs respectively. In this study, the introduced photoanode grids are expected to be used as cheap and industrial photoanodes for PEC water-splitting and hydrogen gas production.

Improved Production Rates of Hydrogen Generation and Carbon Dioxide Reduction Using Gallium Nitride with Nickel Oxide Nanofilm Capping Layer as Photoelectrodes for Photoelectrochemical Reaction.

This work investigates the production of hydrogen (H2) and formic acid (HCOOH) through a photoelectrochemical (PEC) approach. Nickel oxide nanofilms prepared by sputtering capped on n-GaN photoelectrodes were employed to achieve simultaneous water photoelectrolysis and CO2 reduction. The study delves into the role of the nickel oxide layer, examining its potential as a catalyst and/or a protective layer. Furthermore, the influence of nickel oxide layer thickness on the performance of the photoelectrodes is explored. In essence, appropriate nickel oxide thickness is beneficial in increasing the photocurrent of the PEC reaction. The observed improvements in photocurrents and, hence, the production rates can be attributed to the functionality of the nickel oxide nanofilm: mitigating the negative influence of surface defects on n-GaN and facilitating the separation of photogenerated electron-hole pairs at the electrolyte/n-GaN interface. Specifically, PEC cells utilizing the 4 nm-thick nickel oxide nanofilms deposited on n-gallium nitride (n-GaN) electrodes demonstrate a significant enhancement in hydrogen and formic acid production rates. These rates were at least 45% higher compared to PECs using bare n-GaN electrodes.

A photoelectrochemical immunosensor based on cobalt corrole sensitized carbon nitride for human norovirus detection

Norovirus (NoV) stands as the prevailing etiological agent behind childhood gastroenteritis and foodborne illness, garnering significant attention due to its high infectivity pathogenicity. Protruding domain within the capsid protein (VP1) emerges as the primary antigenicity determinant and a hypervariable region, presenting a potential target site for detecting NoV infection. Herein, a label-free photoelectrochemical (PEC) immunosensor was proposed to achieve high sensitivity toward VP1, utilizing Co-Corrole sensitized carbon nitride (Co-Corrole/CN). Co-Corrole combines with CN through covalent bonds, and the strong binding effect accelerates the directional transport of electrons from CN to Co-Corrole. Co-Corrole acts as a photosensitizer, enhancing light harvesting in the visible region. The well-defined interfacial contact in Co-Corrole/CN heterojunction facilitates the electron-hole pairs separation and transfer. The strong light utilization and efficient carrier migration improve the PEC performance to amplify the photocurrent. This developed immunosensor platform demonstrated a wide range (0.75 pg mL–1-150 ng mL–1) with a notably low limit of detection (0.25 pg mL–1), exhibiting excellent stability and selectivity for other viruses. Moreover, this sensor detected clinical samples with remarkable accuracy and practicability. This research develops a facile and label-free diagnostic analytical technology for highly sensitive detection of NoV VP1 and offers promising prospects for improved diagnostic capability.

Photoelectrochemical analysis of Pb2+ based on Au@PTCA Schottky junction with Pb2+-G quadruplex structure.

Herein, a novel photoelectrochemical (PEC) aptasensor using gold nanoparticles@3,4,9,10-perylene tetracarboxylic (Au@PTCA) Schottky junction as the effective optoelectronic material and lead ion (Pb2+)-G quadruplex structure as the efficient quencher was constructed for the detection of Pb2+ with high sensitivity and excellent selectivity. Au@PTCA Schottky junction, which was proposed by the in situ reduction of Au NPs on the PTCA surface, exhibited a strong unidirectional conductivity, which could generate a significantly enhanced PEC signal compared with the pure PTCA. The Pb2+-G quadruplex structure with a large spatial hindrance effect was formed when the target Pb2+ was present owing to the occurrence of the specific recognition between Pb2+ and its aptamer S1. The formation of a Pb2+-G quadruplex structure effectively quenched the initial signal generated by the Au@PTCA Schottky junction, which was derived from restricted electron transport and light transmission. The obtained prominently decreased PEC signal could achieve the quantitative detection of Pb2+ from 0.5 pM to 500 nM, with a low detection limit of 0.17 pM. The preparation time of this PEC aptasensor was 13 h, and the time for PEC measurement depended on the illumination time, which switched off-on-off for 10 s-20 s-10 s. The study proposed here with high sensitivity and excellent selectivity for Pb2+ analysis offered a novel and reliable tool for environmental monitoring related to heavy metal ions.

Nanozyme-mediated signal amplification on g-C3N4/NaBiO3 Z-scheme heterojunction photoelectrode toward ultrasensitive photoelectrochemical immunoassay for prostate-specific antigen

A sandwich-type photoelectrochemical (PEC) immunosensor for prostate-specific antigen (PSA) detection was developed using the g-C3N4/NaBiO3 (CN/NBO) Z-scheme heterojunction as the photoelectrode and glutathione-Cu/Cu2O nanozyme (GSH-Cu/Cu2O NPs) as the signal amplifier. The unique Z-scheme charge-carrier migration pathway of the CN/NBO heterojunction significantly promotes the separation and migration of photogenerated electron-hole pairs, producing a high photocurrent response of the photoelectrode. GSH-Cu/Cu2O NPs with ascorbic acid oxidase (AAO) activity were introduced into the PEC immunosensing system through immunoreactions for signal amplification. Signal amplification was achieved through double photocurrent quenching of the GSH-Cu/Cu2O NPs on the photoelectrode. On the one hand, GSH-Cu/Cu2O NPs as AAO catalyzed ascorbic acid (AA), an electron donor in the PEC system, to produce dehydroascorbic acid (DHA), leading to a decrease in the photocurrent response. On the other hand, the GSH-Cu/Cu2O NPs prevented AA transfer from the detection solution to the interface of the photoelectrode, further aggravating the PEC signal quenching effect. Benefiting from the excellent performance of the Z-scheme heterojunction-based photoelectrode, the dual signal quenching effect of GSH-Cu/Cu2O NPs, the PEC immunosensor showed an ultralow detection limit of 5.1 × 10−15 g mL−1. By coupling a Z-scheme heterojunction-based photoelectrode with a nanozyme-mediated signal amplification strategy, this study provides a novel avenue for the construction of ultrasensitive and convenient biosensing systems.

A molecularly imprinting photoelectrochemical sensor based on Bi2O2S-sensitized perovskite Cs2AgBiBr6 for sarcosine determination.

An original molecular imprinting photoelectrochemical (PEC) sensor for sarcosine detection based on stable lead-free inorganic halide double perovskite Cs2AgBiBr6 is proposed. Cs2AgBiBr6 as a lead-free halide perovskite material possesses severalpositive optoelectronic properties for PEC analysis, such as long-lived component to the charge-carrier lifetime, and strong absorption of visible light. At the same time, two-dimensional materials also offer excellent electronic and mechanical properties; thus, Bi2O2S was used and combined with Cs2AgBiBr6 to provide a stable and large photocurrent, which also benefits from the stability of perovskite Cs2AgBiBr6. Based on this novel PEC assay, the detection range for sarcosine was between 0.005 and 5000ng/mL with a low detection limit of 0.002ng/mL. This work also improved the adhibition of metal halide perovskite in analytical chemistry field, providing a novel way for other small molecule detection.