Recent advances in photoelectrochemistry-coupled dual-modal biosensors:From constructions to biosensing applications

Precise and sensitive bioanalysis has been the major and urgent pursuit in pathologic diagnosis,food safety,environment monitoring,and drug evaluation.Photoelectrochemical(PEC)bioanalysis,as one of the most promising detection technologies,has rapidly expanded within the field of analysis.However,most of reported PEC analysis approaches still suffer from weak external anti-interference ability,high background,and the risk of false positive or negative errors due to their inherent single-signal readout.To overcome these shortcomings,new PEC-coupled dual-modal analysis approaches have been developed,where a dual-response signal can be derived through two completely different mechanisms and independent signal transduction pathways.This review introduces the basic principles of PEC biosensing and enumerates and classifies the substrate or probe selections,constructions,and applications of PEC-coupled dual-modal biosensors.Furthermore,the challenges and developmental prospects of PEC-coupled dual-mode sensing technologies are evaluated and discussed.We hope that this review will provide valuable insights into the latest advancements and practical applications of dual-mode PEC bioanalysis,which will be of great interest to those seeking to stay informed in this field.

PHOTOELECTROCHEMISTRY OF ELECTRODEPOSITED POLYCRYSTALLINE CuInSe_2 THIN FILMS (Ⅰ)——ELECTRODEPOSITION OF CuInSe_2 FILMS

Electrodeposition of CulnSe, was investigated in acidic solutions containing Cu2+, In3+ and HSeO2+ ions. The electrodeposition condition was optimized with the aim of obtaining uniform thin films on titanium substrate. The mechanism of the electrodeposition process is discussed. Structure analysis of the deposited film shows a typical polycrystalline chalcopyrite structure, good crystallinity and homogeneous dispersion. The photoelectrochemical cells made of these kinds of deposited films in polysulfide redox solution give distinct photoresponse.

Photoelectrochemistry of electrochemically deposited cadmium-rich cadmium mercury telluride films

The potentiostatic deposition of cadmium-rich CMT films onto Ti, Mo, Ni substrates from an aqueous bath was carried out. The photoelectrochemical properties of film electrodes were investigated when used in a solid-liquid junction photoelectrochemical cell (PEC). A.C. capacitance was determined.

Differences and Similarities of Photocatalysis and Electrocatalysis in Two-Dimensional Nanomaterials:Strategies,Traps,Applications and Challenges

Photocatalysis and electrocatalysis have been essential parts of electrochemical processes for over half a century.Recent progress in the controllable synthesis of 2D nanomaterials has exhibited enhanced catalytic performance compared to bulk materials.This has led to significant interest in the exploitation of 2D nanomaterials for catalysis.There have been a variety of excellent reviews on 2D nanomaterials for catalysis,but related issues of differences and similarities between photocatalysis and electrocatalysis in 2D nanomaterials are still vacant.Here,we provide a comprehensive overview on the differences and similarities of photocatalysis and electrocatalysis in the latest 2D nanomaterials.Strategies and traps for performance enhancement of 2D nanocatalysts are highlighted,which point out the differences and similarities of series issues for photocatalysis and electrocatalysis.In addition,2D nanocatalysts and their catalytic applications are discussed.Finally,opportunities,challenges and development directions for 2D nanocatalysts are described.The intention of this review is to inspire and direct interest in this research realm for the creation of future 2D nanomaterials for photocatalysis and electrocatalysis.

Enhanced Photocatalytic Efficiency of TiO2 by Combining the Modification of Ag Nanoparticles with the Application of Anodic Bias

Ag-TiO2/ITO film electrode was used as photoanode to investigate the feasibility of a hybrid technology of Ag nanoparticles combined with the application of anodic bias. The results showed that the deposited Ag and applied anodic bias have an apparent additive effect.

Surpassing electrocatalytic limit of earth-abundant Fe^(4+)embedded in N-doped graphene for(photo)electrocatalytic water oxidation

Developing highly active,cost-effective,and environmental friendly oxygen evolution reaction(OER)electrocatalysts facilitates various(photo)electrochemical processes.In this work,Fe3N nanoparticles encapsulated into N-doped graphene nanoshells(Fe_(3)N@NG)as OER electrocatalysts in alkaline media were reported.Both the experimental and theoretical comparison between Fe_(3) N@NG and Fe_(3)N/NG,specifically including in situ Mossbauer analyses,demonstrated that the NG nanoshells improved interfacial electron transfer process from Fe_(3)N to NG to form high-valence Fe^(4+)ions(Fe^(4+)@NG),thus modifying electronic properties of the outer NG shells and subsequently electron transfer from oxygen intermediate to NG nanoshells for OER catalytic process.Meanwhile,the NG nanoshells also protected Fe-based cores from forming OER inactive and insulated Fe_(2)O_(3),leading to high OER stability.As a result,the as-formed Fe^(4+)@NG shows one of the highest electrocatalytic efficiency among reported Fe-based OER electrocatalysts,which can as well highly improve the photoelectrochemical water oxidation when used as the cocatalysts for the Fe_(2)O_(3) nanoarray photoanode.

Photoelectrochemical Properties of Highly Oriented ZnO Nanotube Array Films on ITO Substrates

Highly oriented ZnO nanotube array films on the conducting substrates have been synthesized by a simple hydrothermal method and characterized by scanning electron microscopy (SEM) and UV-Vis spectroscopy. The thin films consisting of laterally fragmentized ZnO nanotubes with controlled orientation have been tested as photoanode in Gr鋞zel-type solar cell. For a sandwich-type cell, with 0.5 mol/L LiI and 0.05 mol/L I2 in propylene carbonate electrolyte, the overall solar energy conversion efficiency reaches 2.3%.

Research progress of TiO2 photocathodic protection to metals in marine environment

Corrosion protection has become an important issue as the amount of infrastructure construction in marine environment increased.Photocathodic protection is a promising method to reduce the corrosion of metals,and titanium dioxide(TiO2) is the most widely used photoanode.This review summarizes the progress in TiO2 photo gene rated protection in recent years.Different types of semiconductors,including sulfides,metals,metal oxide s,polymers,and other materials,are used to design and modify TiO2.The strategy to dramatically improve the efficiency of photoactivity is proposed,and the mechanism is investigated in detail.Characterization methods are also introduced,including morphology testing,light absorption,photoelectrochemistry,and protected metal observation.This review aims to provide a comprehensive overview of Ti02 development and guide photocathodic protection.

Stability of Ag@SiO2 core–shell particles in conditions of photocatalytic overall water-splitting

Core–shell nanoparticles containing plasmonic metals（Ag or Au） have been frequently reported to enhance performance of photo-electrochemical（PEC） devices. However, the stability of these particles in water-splitting conditions is usually not addressed. In this study we demonstrate that Ag@SiOcore–shell particles are instable in the acidic conditions in which WO-based PEC cells typically operate, Ag in the core being prone to oxidation, even if the SiOshell has a thickness in the order of 10 nm. This is evident from in situ voltammetry studies of several anode composites. Similar to the results of the PEC experiments, the Ag@SiOcore–shell particles are instable in slurry-based, Pt/ZnO induced photocatalytic water-splitting. This was evidenced by in situ photodeposition of Ag nanoparticles on the Pt-loaded ZnO catalyst, observed in TEM micrographs obtained after reaction. We explain the instability of Ag@SiOby OH-radical induced oxidation of Ag, yielding dissolved Ag+. Our results imply that a decrease in shell permeability for OH-radicals is necessary to obtain stable, Ag-based plasmonic entities in photo-electrochemical and photocatalytic water splitting.

Ni-Doped BiVO4 with V4+ Species and Oxygen Vacancies for Efficient Photoelectrochemical Water Splitting

Bismuth vanadate is a promising photoanode material for photoelectrochemical (PEC) water splitting, but its activity and stability need to be further improved. In this work, we synthesized Ni-doped BiVO 4 abundant with V 4+ species and oxygen defects through an in situ electrodeposition method. The eff ective doping can decrease the particle size of BiVO 4 and lead to the formation of V 4+ species/oxygen defects. Accordingly, the doped and defective BiVO 4 showed high optical absorption and rapid charge transfer, and further showed much higher PEC activity than pure BiVO 4 . Specifi cally, 5-Ni-BiVO 4 exhibits the highest activity in PEC water splitting, with a photocurrent of 2.39 mA/cm 2 at 1.23 V versus RHE (the reversible hydrogen electrode), which is 2.5 times higher than pure BiVO 4 (0.94 mA/cm 2 ), and much higher incident photon-to-current effi ciency (IPCE) value of 45%(while only 25% for BiVO 4 at ca. 400 nm). This work provides an in situ method for the development of a high-performance photoanode.

Solar-harvesting lead halide perovskite for artificial photosynthesis

Facing the upcoming energy and environmental crisis, artificial photosynthesis for producing various solar fuels (e.g., hydrogen or carbon products) via a solar-to-chemical energy conversion is receiving increasing attention;however, its low conversion efficiency is a challenge for commercialization. To resolve low-efficiency issues, lead halide perovskite (LHP) with outstanding optoelectronic properties compared to conventional semiconductors can be a promising approach to improve the solar-to-fuel conversion reactions and solar fuel production efficiency. The tunable energy band structure and charge transport properties of LHP have promoted their extensive use in the production of solar fuels. This study summarizes the recent advancements of LHP-mediated solar-to-fuel conversions, classified by their redox reactions, namely solar water splitting, hydrohalic acid splitting, and CO_(2) reduction. Advanced approaches for achieving high conversion efficiency and long-term durability are discussed, including the configuration of devices, the composition of LHP, and the protection strategy of LHP. Moreover, the reaction mechanisms of LHP-mediated solar-to-chemical energy conversions and obstacles for enhancing the conversion efficiency are discussed. Finally, we present the perspectives on the development of LHP-incorporated solar-to-fuel conversion systems, which might open a new era of energy harvesting and storage.

ELECTROCHEMISTRY OF POLYANILINE UNDER LIGHT

The electrochemistry of polyaniline synthesized electrochemically in acidic solution under light irradiation has been studied as a function of the applied potentials, the concentration and acidity of electrolyte as well as pH at applied potentials in the rang+0.40 to-0.5V vs. SCE. It is concluded that under selected experimental conditions the reduced repeat groups in polyaniline are oxidized by air in the dark and that this oxidation process can be strongly photocatalyzed.

Unravelling the essential difference between TiO_(x) and AlO_(x) interface layers on Ta_(3)N_(5) photoanode for photoelectrochemical water oxidation

Tantalum nitride(Ta_(3)N_(5))is a very promising photoanode material due to its narrow band gap(2.1 eV)and suitable band alignment for solar water splitting.However,it suffers from severe photocorrosion during water oxidation.In this work,it was found that surface passivation by AlO_(x) and TiO_(x) layers results in dramatically different PEC performance of Ta_(3)N_(5) photoanode for water oxidation.The mechanism study indicates that the negative charges on AlO_(x) can generate additional field to promote separation of photogenerated charges,while the positive charges on TiO_(x) layer show the opposite effect.As a result,the Ta_(3)N_(5) based photoanode modified with AlO_(x) layer gives a high photocurrent of 12.5 mA cm^(-2) for 24 h at 1.23 V versus the reversible hydrogen electrode(RHE).Dynamic analysis implies that the hole extraction and transfer are significantly improved by the modification with the AlO_(x) layer.This work reveals the importance of the charges on surface passivation layer in interface engineering of photoelectrodes.

Fabrication by Fine Particles and Evaluation of WO₃Photo Semiconductor Electrode

Application of semiconductor particles has been noticed to solve energy problems as photocatalysis for O2 evolution in water splitting etc. We are trying fabrication of semiconductor electrode by n-WO3 particle toward O2 evolution in water splitting. The electrode obtained high photooxidation properties of water as preventing effective recombination between electrons and holes by utilizing fine semiconductor particles. Particularly, application of suspension prepared by ball milling was able to obtain fine n-WO3 thin film and the remarked semiconductor properties.

Electrochemical and Photoelectrochemical Properties of Nano-Islands of Zinc and Niobium Oxides Deposited on Aluminum Thin Film by RF Magnetron Reactive Sputtering

Zinc oxide (ZnO) and niobium oxide (NbOx) with a nano-island structure were deposited by a sputtering method on Al-coated glass substrates. Cells with a (ZnO or NbOx)/Al/glass|KNO3aq.|Al/ glass structure were assembled, and electrochemical and photoelectrochemical properties were evaluated. The ZnO and NbOx electrodes had higher electrode potentials than the counter Al/glass electrode, and electron flows from the counter electrode to the ZnO and NbOx electrodes through the external circuit were commonly confirmed. In the ZnO-based cell, only faint photocurrent generation was seen, where Zn and Al elution from the ZnO electrode was found. In the NbOxbased cell, however, stable generation of electricity was successfully achieved, and electrode corrosion was not recognized even in microscopic observations. A photoelectrochemical conversion model was proposed based on potential-pH diagrams. In the case of nano-island structures formed at shorter NbOx deposition time, it was concluded that the photoelectrochemical reactions, which were proceeded in the immediate vicinity of the boundary among nano-islands, substrate, and electrolyte solution, were predominant for the photoelectrochemical conversion, and in the case of film structures with longer deposition time, the predominant reactions took place at the film surface.

Nanostructured AlFeO_(3) thin films as a novel photoanode for photoelectrochemical water splitting

The earth-abundant and robust aluminum ferrite,AlFeO_(3)(AFO),is mainly studied in the context of ferroelectrics.Herein,we demonstrate that AFO can be used as a stable solar absorber in photoelectrochemical cells for solar water splitting,exhibiting attractive performance.This is the first report on the photoelectrochemical activity of AFO.AFO thin-film photoelectrodes prepared by solution-processing methods are composed of vertically oriented thin nanosheets,featuring the rhombohedral symmetry(R3c)and n-type conductivity.The as-prepared AFO photoanodes generate a photocurrent density of+0.78 mA·cm^(-2) at 1.23 V vs.reversible hydrogen electrode(RHE)with the photocurrent _(onset) potential(U_(onset))close to the flat band potential of 0.5 V vs.RHE in the presence of hole scavengers.Remarkably,the U_(onset) of AFO for solar water splitting coincides with the flat band potential as well,which is rare in n-type inorganic absorbers.We also report other properties of AFO associated with photoelectrochemical performance.AFO films exhibit a band gap energy of 2.31 eV and positive band edges with low dispersion.Moreover,the carrier lifetimes in AFO films are up to millisecond timescales under the mediation of defect traps.Based on the photoelectrochemical behavior and optoelectronic properties,we believe that AFO has great potential for application in photoelectrochemical cells.

Developing silicon-based photocathodes for CO_(2)conversion

Photoelectrochemical(PEC)conversion of CO_(2)presents a promising avenue for solar-driven chemical fuel production,with silicon emerging as a cost-effective and high-light-absorbing material pivotal to this technology.Aiming at exploring opportunities for industrializing PEC CO_(2)reduction(PEC-CO_(2)R)by minimizing reaction energy consumption,enhancing reaction efficiency and selectivity,this review summarizes recent advancements in developing Si-based photocathodes for PEC-CO_(2)R.It outlines the fundamental principles,advantages,and limitations of Si photocathodes with key performance metrics.Based on this understanding,the strategies to enhance the performance of the PEC-CO_(2)R system,including light absorption,charge separation,and catalytic reactions are categorized as the interfacial modification,active site decoration,and protective layer design.The design ideas of this advantageous three-layer structure in promoting the efficiency,stability,and selectivity have been clarified.Then,this review scrutinizes the influence of the photocathodic chemical environment.This review consolidates the mechanism insights and notable breakthroughs of various fuel generation processes within Si-based PEC-CO_(2)R systems.Providing this wealth of information offers an up-to-date perspective on the dynamic developments in silicon-based PEC-CO_(2)conversion and underscores the promising pathways toward the sustainable fuel synthesis from pollutant CO_(2).

Electrolyte Effect on Photoetching of Gallium Nitride

The limited material removal rate of conventional chemical mechanical polishing(CMP)significantly hinders the fabrica-tion efficiency and surface quality,thereby preventing the development of gallium nitride(GaN)-based devices.Moreover,the incorporation of photoelectrochemistry in CMP has garnered increasing attention because of its potential to enhance the quality and efficiency of the GaN process.However,a considerable gap still exists in the comprehensive understanding of the specific photoelectrochemical(PEC)behavior of GaN.Here,we report the influence of the electrolyte on the PEC etching of GaN.Various acids and bases were tested,with their pH being carefully adjusted.The concentrations of the cations and anions were also examined.The results showed that photocorrosion/photoetching was more pronounced in sulfuric acid,phosphoric acid,and nitric acid environments than in alkaline environments,but it was less pronounced in hydrochloric acid.Furthermore,the effects of pH and anion concentration on photoetching were investigated,and the results revealed that pho-toetching in acidic environments weakened with increasing pH levels and diminished with increasing sulfate concentration.The underlying reasons contributing to this observation were explored.These findings provide ideas for improving the pho-toetching efficiency of GaN,thereby enriching the photoelectrochemical mechanical polishing(PECMP)technology of GaN.

Controllable decoration of Ni-MOF on TiO_(2):Understanding the role of coordination state on photoelectrochemical performance

Decoration of metal-organic framework(MOF)has been considered as an effective route to improve the photoelectrochemical(PEC)performance of TiO_(2),but there is still a lack of understanding of the regulatory structure.Herein,Ni-MOF was rationally introduced by in-situ etching method,which helps for artificially regulating the coordination state of Ni sites.The photocurrent density(0.81 mA/cm^(2))and IPCE value(33.1%)of TiO_(2)-MOF-2 are about twice higher than that of pristine TiO_(2) due to the rich unsaturated sites of Ni-MOF.Meanwhile,the saturated coordination has caused the decline of PEC performance because of the obvious steric hindrance.Therefore,this work presents an insight for the effect of coordination state on PEC activity especially in MOF system.