Two Photoelectrochemical Processes for TiO2 Electrode under UV Illumination

TiO2 thin film electrode was prepared by a sol-gel method on ITO substrates. Cyclic voltammetric behavior of the ITO/TiO2 electrode under ultraviolet (UV) illumination was investigated in the solution of Na2SO4.There are two photoelectrochemical processes for TiO2 electrode under UV illumination.One is a fast process,which results in the appearance of anodic photocurrent.The anodic photocurrent will appear and disappear with the light on and off.The other is a slow process,which will be responsible for the appearance of an oxidative peak. When the electrode is illuminated under UV light for a long time,a new oxidative peak can be observed.The peak current increases with the increase of UV illumination time.It is assumed that the new peak belongs to the oxidation of Ti^3 ,which formed and accumulated on the electrode surface during the UV illumination.A detailed mechanism is proposed on the base of these two photoelectrochemical processes.It is assumed that the change of hydrophilicity of TiO2 thin film may be related to the slow process while the film irradiated by UV light.     

One-step synthesis of Pt nanoparticles/reduced graphene oxide composite with enhanced electrochemical catalytic activity

A one-step electrochemical approach for synthesis of Pt nanoparticles/reduced graphene oxide(Pt/RGO) was demonstrated.Graphene oxide(GO) and chloroplatinic acid were reduced to RGO and Pt nanoparticles(Pt NPs) simultaneously,and Pt/RGO composite was deposited on the fluorine doped SnO 2 glass during the electrochemical reduction.The Pt/RGO composite was characterized by field emission-scanning electron microscopy,Raman spectroscopy and X-ray photoelectron spectroscopy,which confirmed the reduction of GO and chloroplatinic acid and the formation of Pt/RGO composite.In comparison with Pt NPs and RGO electrodes obtained by the same method,results of cyclic voltammetry and electrochemical impedance spectroscopy measurements showed that the composite electrode had higher catalytic activity and charge transfer rate.In addition,the composite electrode had proved to have better performance in DSSCs than the Pt NPs electrode,which showed the potential application in energy conversion.     

Gold nanoparticles-enhanced bisphenol A electrochemical biosensor based on tyrosinase immobilized onto self-assembled monolayers-modified gold electrode

A novel electrochemical sensor based on the immobilization of tyrosinase(tyr) onto gold nanoparticles(nano-Au) and thioctic acid amide(T-NH2) self-assembled monolayers(SAMs)-modified gold electrode has been developed for the determination of bisphenol A(BPA).It was found that the nano-Au could significantly enhance the electrochemical response of tyr/nano-Au/T-NH2/Au electrode to BPA,and the enhancement effect of nano-Au on the current response was also related to the enzyme.The results indicated that the biosensor could be used as a detector for BPA determination with a linear range from3.99 ×10-7mol/L to 2.34 ×10-4mol/L and a detection limit of 1.33×10-7mol/L.In addition,this biosensor showed good reproducibility.     

Highly-ordered dye-sensitized TiO2 nanotube arrays film used for improving photoelectrochemical electrodes

Thin titanium oxide nanotube arrays (TNAs) films were synthesized by anodization of titanium foil in an aqueous dimethyl sulfoxide solution using a platinum foil counter electrode.TNAs up to 6.8 μm in length,120 nm in inner pore diameter,and 20 nm in wall thickness were obtained by 40 V potentials anodization for 24 h.Their microstructures and surface morphologies were characterized by XRD,TEM,SAED and UV-vis spectroscopy.The photoelectrochemical properties of as-prepared unsensitized and dye-sensitized TNAs electrodes were examined under simulated solar light (AM 1.5,100 mW/cm2) illumination.The results showed that the photocurrent of the dye-sensitized TNAs electrodes reached 6.9 mA/cm2,which was 6 times more than that of the dye-sensitized TiO2 nanoparticles (TNPs) electrodes.It implied that the electron transport process and the charge recombination suppression within TNAs electrodes were much more favorable in comparison with that in the TNPs electrodes.Electrodes applying such kind of titania nanotubes will have a potential to further enhance the efficiencies of TNAs-based dye-sensitized solar cells.     

以聚吡咯和纳米金为基质基于电化学交流阻抗测试的乙肝表面抗原免疫传感器研究

A novel simple immunosensing strategy for fabrication of hepatitis B surface antigen detection has been developed via electrochemical impedance spectroscopy （EIS） as a platform. At first, the conductive polymer polypyrrole （PPy） film was electrodeposited on a platinum electrode surface to adsorb the gold nanoparticles （nano-Au） via the opposite-charged adsorption technique, and then hepatitis B surface antibodies were adsorbed onto the surface of nano-Au. The modification procedure was characterized by EIS. Such spectroscopy is attributed to the concomitant conductivity changes of the polymerized pyrrole film and gold nanoparticles. The factors influencing the performance of resulting immunoelectrode were studied in detail. The linear range of the resulting immunoelectrode is from 2.6 to 153.6 ng.mL^-1 with a detection limit of 1.3 ng·mL^-1 at 3σ. In addition, the experiment results indicate that antibody immobilized on this way exhibits a good sensitivity, selectivity, high stability and a long-term maintenance of bioactivity, implying a great promising alternative approach for reagentless immunosensing analysis in the clinical diagnosis.     

用聚(L-蛋氨酸)/纳米金修饰玻碳电极同时灵敏检测多巴胺和尿酸(英文)

A novel electrochemical sensor was fabricated by electrodeposition of gold nanoparticles on a poly(L-methionine)(PMT)-modified glassy carbon electrode(GCE) to form a nano-Au/PMT composite-modified GCE(nano-Au/PMT/GCE).Scanning electron microscopy and electrochemical techniques were used to characterize the composite electrode.The modified electrode exhibited considerable electrocatalytic activity towards the oxidation of dopamine(DA) and uric acid(UA) in phosphate buffer solution(pH = 7.00).Differential pulse voltammetry revealed that the electrocatalytic oxidation currents of DA and UA were linearly related to concentration over the range of 5.0 ×10–8 to 10–6 mol/L for DA and 7.0 × 10–8 to 10–6 mol/L for UA.The detection limits were 3.7 × 10–8mol/L for DA and 4.5 × 10–8 mol/L for UA at a signal-to-noise ratio of 3.According to our experimental results,nano-Au/PMT/GCE can be used as a sensitive and selective sensor for simultaneous determination of DA and UA.     

Oxidation and detection of L-cysteine using a modified Au/Nafion/glass carbon electrode

In this work,the electrochemical oxidation of L-cysteine(CySH)was investigated on a composite film modified electrode with Au nanoparticles dispersed in the fluorocarbon polymer(Nafion).The excellent electrocatalytic effect on CySH oxidation was attributed to the role of Au nanoparticles.The voltammetric studies revealed two anodic peaks for the oxidation of CySH in the pH range of 2.0–8.0.The electrode was used to detect cysteine at pH 2.0 and pH 7.0.At pH 2.0,a determination range of 3.0–50.0?mol/L was ob...     

Synthesis and characterization of sulfur-titanium dioxide nanocomposites for photocatalytic oxidation of cyanide using visible light irradiation

A sol-gel method was used to prepare TiO2and sulfur-TiO2(S-TiO2)nanocomposites, which were characterized by N2 adsorption-desorption, X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescene, ultraviolet visible and transmission electron microscopy measurements. The photocatalytic performance of TiO2 and S-TiO2nanocomposites, with respect to the photocatalytic oxidation of cyanide under visible light irradiation, was determined. The results reveal that S is well dispersed on the surface of TiO2 nanoparticles. Additionally, the surface area of the S-TiO2nano-composites was observed to be smaller than that of the TiO2nanoparticles because of blocked pores caused by doping with S. The S-TiO2nanocomposite (0.3 wt% S) exhibited the lowest band gap and the highest photocatalytic activity in the oxidation of cyanide. The photocatalytic performance of S-TiO2(0.3 wt% S) nanocomposites was stable, even after the fifth reuse of the nanoparticles for the oxidation of cyanide.     

A Novel Composite Electrode of Photocatalyst—TiO2／C Loading on the Surface of the Air （Oxygen） Electrode

The methods for preparing the H2O2 generating air (oxygen) electrode and the composite electrode of photocatalyst-TiO2/C loading on the surface of the air (oxygen) electrode were introduced.In the case of the composite electrode,the current efficiency of electro-generated H2O2 is higher than 80%(J≤15mA/cm^2).The degradation of aniline was used as an example to measure the influence of the composite electrode and compared with the system in which the air (oxygen) electrode and the photocatalyst-TiO2 were sqparated.The results confirmed that the composite electrode played an active role on accelerating the degradation rate of aniline.According to the measurement of the polarization curves of composite electrode and TiO2 photo anode,and of the adsorbing amount of aniline on the surface of the composite electrode,the principle of descending the recombination reta of photo-generated electron and hole and of enhancing the oxidation rate of organic molecule was described.The mechanism about the degradation of aniline was also discussed.     

Composite Electrode SnO2／TiO2 for Dye-Sensitized Solar Cells

Composite nanoporous electrode SnO2/TiO2 was fabricated for the dye sensitized solar cell (DSSC) with N3 (Cis-Ru). After introducing of TiO2, the open-circuit photovoltage (Voc) was higher than that of the pure SnO2 electrode, while short-circuit photocurrent (Isc) was varied with the ratio of the TiO2. Appropriate content of the TiO2 can be beneficial to the efficiency of the solar cell, and it gives negative impact on the composite electrode when the content of TiO2 is higher.     

低温吸附制备Au-TiO2复合薄膜及其光电化学性质

在低温条件下将预先合成的Au溶胶吸附到TiO₂薄膜上以制备纳米Au-TiO₂复合薄膜,以超高分辨率场发射扫描电镜(FESEM)、X射线衍射(XRD)及X射线光电子能谱(XPS)表征Au-TiO₂膜,并在UV辐照下测定了Au-TiO₂薄膜电极的光电化学性质。纳米Au呈金属态,平均粒径为(4.3±1.2) nm,负载量高,均匀地沉积于TiO₂薄膜表面。光电化学测试表明,沉积纳米Au后,TiO₂电极的光生电流提高近5倍,光生电压明显向负值增大,说明纳米Au可增强光生载流子的分离效率,促进电荷在电极与溶液界面间的转移。Au-TiO₂电极的电荷传递法拉第阻抗(R_ct)是TiO₂电极的一半,说明负载的纳米Au粒抑制了光生电子-空穴的复合,提高了电极中载流子浓度。     

Gold(Core)–Lead(Shell) Nanoparticle‐Loaded Titanium(IV) Oxide Prepared by Underpotential Photodeposition: Plasmonic Water Oxidation

Underpotential photodeposition of Pb yields an ultrathin shell layer on the Au(111) surface of Au nanoparticle(NP)‐loaded TiO₂ (Au/TiO₂) with heteroepitaxial nanojunctions. The localized surface plasmon resonance of Au/TiO₂ undergoes no damping with the Pb‐shell formation, and the Pb shell offers resistance to aerobic oxidation. Mesoporous films comprising the Au(core)–Pb(shell) NP‐loaded TiO₂ and unmodified Au/TiO₂ were formed on fluorine‐doped tin oxide (FTO) electrode. Using them as the photoanode, photoelectrochemical cells were fabricated, and the photocurrent was measured under illumination of simulated sunlight. The photocurrent for water splitting is dramatically enhanced by the Pb‐shell formation. The photoelectrochemical measurements of the hot‐electron lifetime and density functional theory calculations for model clusters indicate that the Pb‐shell effect originates from the charge separation enhancement.     

Interfacial electron transfer at TiO2 nanostructured electrodes modified with capped gold nanoparticles: The photoelectrochemistry of water oxidation

We have studied the photoelectrochemical behavior of nanostructured anatase electrodes modified with gold nanoparticles stabilized either with citrate (Au_cit) or with tetraoctylammonium bromide (Au_TOAB). An increase both in photocurrent and in photopotential was observed in 0.05 M NaOH upon modification with Au_TOAB. This behavior is attributed to an efficient hole consumption at the gold nanoparticles, which implies an effective hole transport to them from the TiO₂ nanostructure, probably facilitated by the capping agent. Once in the Au particles, the holes would promote an oxidation process (O₂ generation), which requires that the Au nanoparticles attain a high enough local electrode potential. This is possible as long as the Au_TOAB nanoparticles may behave as nanocapacitors with a very low capacity (ca. 1 aF) and thus the accumulation of a few holes may induce important changes in their potential. In acidic medium or in the presence of 0.1 M CH₃OH no enhancement was detected. In the case of TiO₂ modified with Au_cit, no increase of the photoelectrochemical response was observed in any case. It is suggested that a proper design of the metal/semiconductor nanojunctions may lead to an enhanced charge separation and to the eventual development of photoinduced metal electrocatalysis.     

Size‐Dependence of the Activity of Gold Nanoparticle‐Loaded Titanium(IV) Oxide Plasmonic Photocatalyst for Water Oxidation

Mesoporous TiO₂ nanocrystalline film was formed on fluorine‐doped tin oxide electrode (TiO₂/FTO) and gold nanoparticles (NPs) of different sizes were loaded onto the surface with the loading amount kept constant (Au/TiO₂/FTO). Visible‐light irradiation (λ>430 nm) of the Au/TiO₂/FTO photoanode in a photoelectrochemical cell with the structure of photoanode|0.1 m NaClO4 aqueous solution|Ag/AgCl (reference electrode)|glassy carbon (cathode) leads to the oxidation of water to oxygen (O₂). We show that the visible‐light activity of the Au/TiO₂/FTO anode increases with a decrease in Au particle size (d) at 2.9≤d≤11.9 nm due to the enhancement of the charge separation and increasing photoelectrocatalytic activity.     

Multiple plasmonic effect on photocurrent generation of metal‐loaded titanium dioxide composite/dye films on gold grating surface

We demonstrate the multiple plasmonic effect on the photocurrent properties of photoanodes containing Ag or Au nanoparticles (NPs) loaded onto titanium dioxide film (Ag–TiO₂ or Au–TiO₂) on Au grating surfaces. Ag–TiO₂ or Au–TiO₂ nanocomposite particles are prepared by a flame spray pyrolysis route. The structures and morphologies of the prepared products are characterized by high‐resolution transmission electron microscopy. The Ag–TiO₂ or Au–TiO₂ composite NPs are deposited by spin coating onto the Au grating surfaces. The photoanode electrode is a layered structure of blu‐ray disc‐recordable grating substrate/Au/Ag (or Au)–TiO₂/dye/electrolyte/indium‐tin oxide. The plasmonic effect is induced when Ag or Au NPs are located within the propagating surface plasmon (SP) field on the Au grating surface. The short‐circuit photocurrent is increased by exciting the grating‐coupled propagating SP on the Au gratings and is further enhanced by positioning the Ag or Au NPs within the grating‐coupled SP field. Copyright © 2014 John Wiley & Sons, Ltd.     

CdSeTe@CdS@ZnS Quantum‐Dot‐Sensitized Macroporous Tio2 Film: A Multisignal‐Amplified Photoelectrochemical Platform

A macroporous TiO₂ film (M‐TiO₂), which was prepared by burning off the polystyrene microsphere (PS) template from a PS/TiO₂ composite film, can provide a large active surface, improve electron‐transport performance, and increase the photocurrent. Furthermore, core–shell–shell CdSeTe@CdS@ZnS quantum dots (QDs) were introduced to sensitize the M‐TiO₂ film, which can efficiently broaden the absorption spectra range, separate and transfer charge carriers, reduce recombination loss, and improve photovoltaic response, with a sensitization shell of CdS and a passivation shell of ZnS. A multisignal‐amplified photoelectrochemical platform was fabricated by further modifying this film with a combination of biotin–DEVD–peptide (Biotin–Gly–Asp–Gly–Asp–Glu–Val–Asp–Gly–Cys) (which is specifically cleaved by caspase‐3) and streptavidin‐labeled alkaline phosphatase (SA‐ALP). Under the enzymatic catalysis of ALP with the substrate 2‐phospho‐L ‐ascorbic acid trisodium salt (AAP), ascorbic acid (AA) was generated as a better electron donor, leading to increased photocurrent output. The activity of caspase‐3, which depends on the amount of residual peptide on the electrode, was inversely proportional to the amount of AA. By monitoring the variation of photocurrent caused by AA, caspase‐3 activity and the therapeutic effect of nilotinib (a special medicine of chronic myeloid leukemia, CML) were indirectly detected and evaluated. The photoelectrochemical platform can be used as a potential evaluation system for monitoring caspase‐3 activity and drug effects.     

SrTiO3/TiO2 Hybridstructure as Photoanode in Dye‐Sensitized Solar Cell

In dye‐sensitized solar cells (DSSCs), the charge recombination at the TiO₂/dye/electrolyte interface greatly influences the photoelectron conversion efficiency. Hybrid semiconductor materials with matched band potentials are designed to reduce the charge recombination. In this study, SrTiO₃/TiO₂ hybridstructure was synthesized by using TiO₂ nanoparticles as template in a hydrothermal, showing a negative shift in the flat band potential. The DSSC with the SrTiO₃/TiO₂ anode exhibits an increased photovoltage and a reduced photocurrent. The suppression of charge recombination at the TiO₂/dye/electrolyte interface was observed in the electrochemical impedance spectroscopy, causing an improvement in the photovoltage. However, the SrTiO₃/TiO₂ system shows an obstructed electrons injection from the dye to SrTiO₃/TiO₂, limiting the photocurrent performance. The photoelectrochemical properties of the SrTiO₃/TiO₂ system are discussed in detail herein.     

Synthesis and Study of Plasmon‐Induced Carrier Behavior at Ag/TiO2 Nanowires

Nanocomposites of Ag/TiO₂ nanowires with enhanced photoelectrochemical performance have been prepared by a facile solvothermal synthesis of TiO₂ nanowires and subsequent photoreduction of Ag⁺ ions to Ag nanoparticles (AgNPs) on the TiO₂ nanowires. The as‐prepared nanocomposites exhibited significantly improved cathodic photocurrent responses under visible‐light illumination, which is attributed to the local electric field enhancement of plasmon resonance effect near the TiO₂ surface rather than by the direct transfer of charge between the two materials. The visible‐light‐driven photocatalytic performance of these nanocomposites in the degradation of methylene blue dye was also studied, and the observed improvement in photocatalytic activity is associated with the extended light absorption range and efficient charge separation due to surface plasmon resonance effect of AgNPs.     

A photoelectrochemical immunosensor based on Au-doped TiO2 nanotube arrays for the detection of α-synuclein

α‐Synuclein (α‐SYN) is a very important neuronal protein that is associated with Parkinson’s disease. In this paper, we utilized Au‐doped TiO₂ nanotube arrays to design a photoelectrochemical immunosensor for the detection of α‐SYN. The highly ordered TiO₂ nanotubes were fabricated by using an electrochemical anodization technique on pure Ti foil. After that, a photoelectrochemical deposition method was exploited to modify the resulting nanotubes with Au nanoparticles, which have been demonstrated to facilitate the improvement of photocurrent responses. Moreover, the Au‐doped TiO₂ nanotubes formed effective antibody immobilization arrays and immobilized primary antibodies (Ab₁) with high stability and bioactivity to bind target α‐SYN. The enhanced sensitivity was obtained by using {Ab₂‐Au‐GOx} bioconjugates, which featured secondary antibody (Ab₂) and glucose oxidase (GOx) labels linked to Au nanoparticles for signal amplification. The GOx enzyme immobilized on the prepared immunosensor could catalyze glucose in the detection solution to produce H₂O₂, which acted as a sacrificial electron donor to scavenge the photogenerated holes in the valence band of TiO₂ nanotubes upon irradiation of the other side of the Ti foil and led to a prompt photocurrent. The photocurrents were proportional to the α‐SYN concentrations, and the linear range of the developed immunosensor was from 50 pg mL^?1 to 100 ng mL^?1 with a detection limit of 34 pg mL^?1. The proposed method showed high sensitivity, stability, reproducibility, and could become a promising technique for protein detection.