Biomolecule-nanoparticle hybrid systems for bioelectronic applications

Recent advances in nanobiotechnology involve the use of biomolecule-nanoparticle (NP) hybrid systems for bioelectronic applications. This is exemplified by the electrical contacting of redox enzymes by means of Au-NPs. The enzymes, glucose oxidase, GOx, and glucose dehydrogenase, GDH, are electrically contacted with the electrodes by the reconstitution of the corresponding apo-proteins on flavin adenine dinucleotide (FAD) or pyrroloquinoline quinone (PQQ)-functionalized Au-NPs (1.4 nm) associated with electrodes, respectively. Similarly, Au-NPs integrated into polyaniline in a micro-rod configuration associated with electrodes provides a high surface area matrix with superior charge transport properties for the effective electrical contacting of GOx with the electrode. A different application of biomolecule-Au-NP hybrids for bioelectronics involves the use of Au-NPs as carriers for a nucleic acid that is composed of hemin/G-quadruplex DNAzyme units and a detecting segment complementary to the analyte DNA. The functionalized Au-NPs are employed for the amplified DNA detection, and for the analysis of telomerase activity in cancer cells, using chemiluminescence as a readout signal. Biomolecule-semiconductor NP hybrid systems are used for the development of photoelectrochemical sensors and optoelectronic systems. A hybrid system consisting of acetylcholine esterase (AChE)/CdS-NPs is immobilized in a monolayer configuration on an electrode. The photocurrent generated by the system in the presence of thioacetylcholine as substrate provides a means to probe the AChE activity. The blocking of the photocurrent by 1,5-bis(4-allyldimethyl ammonium phenyl)pentane-3-one dibromide as nerve gas analog enables the photoelectrochemical analysis of AChE inhibitors. Also, the association CdS-NP/double-stranded DNA hybrid systems with a Au-electrode, and the intercalation of methylene blue into the double-stranded DNA, generates an organized nanostructure of switchable photoelectrochemical functions. Electrochemical reduction of the intercalator to the leuco form, -0.4 V vs. SCE, results in a cathodic photocurrent as a result of the transfer of photoexcited conduction-band electrons to O(2) and the transport of electrons to the valance-band holes by the reduced intercalator units. The oxidation of the intercalator, E 0 V (vs. SCE), yields in the presence of triethanolamine, TEOA, as sacrificial electron donor, an anodic photocurrent by the transport of conduction-band electrons, through intercalator units, to the electrodes, and filling the valance-band holes with electrons supplied by TEOA. The systems reveal potential-switchable directions of the photocurrents, and reveal logic gate functions.     

Efficient and stable photo-oxidation of water by a bismuth vanadate photoanode coupled with an iron oxyhydroxide oxygen evolution catalyst

BiVO(4) films were prepared by a simple electrodeposition and annealing procedure and studied as oxygen evolving photoanodes for application in a water splitting photoelectrochemical cell. The resulting BiVO(4) electrodes maintained considerable photocurrent for photo-oxidation of sulfite, but generated significantly reduced photocurrent for photo-oxidation of water to oxygen, also decaying over time, suggesting that the photoelectrochemical performance of BiVO(4) for water oxidation is mainly limited by its poor catalytic ablity to oxidize water. In order to improve the water oxidation kinetics of the BiVO(4) electrode, a layer of FeOOH was placed on the BiVO(4) surface as an oxygen evolution catalyst using a new photodeposition route. The resulting BiVO(4)/FeOOH photoanode exhibitied significantly improved photocurrent and stability for photo-oxidation of water, which is one of the best among all oxide-based phoatoanode systems reported to date. In particular, the BiVO(4)/FeOOH photoanode showed an outstanding performance in the low bias region (i.e., E < 0.8 V vs RHE), which is critical in determining the overall operating current density when assembling a complete p-n photoelectrochemical diode cell. The photocurrent-to-O(2) conversion efficiency of the BiVO(4)/FeOOH photoanode is ca. 96%, confirming that the photogenerated holes in the BiVO(4)/FeOOH photoanode are indeed excusively used for O(2) evolution.     

Quantitative Photoelectrochemical Detection of Biotin Conjugated CdSe/ZnS Quantum Dots on the Avidin Immobilized ITO Electrodes

Photocurrent generation from CdSe/ZnS (core/shell) quantum dots (QDs) in a photoelectrochemical cell was proposed to perform a bioaffinity biosensor in this study. The photocurrent of QDs is reversible and methylene blue as an electron transfer mediator causes a four‐fold increase in the photocurrent. We further present quantitative photoelectrochemical detection of biotin conjugated QDs on the avidin immobilized ITO electrodes. A linear calibration graph was obtained in the range of 4 and 18 nM of biotin conjugated QDs with a coefficient of determination of 0.997. Results imply that QDs can be successfully used as photoelectroactive labels for the photoelectrochemical biosensor systems.     

Visible light induced photoelectrochemical biosensing based on oxygen-sensitive quantum dots

A visible light induced photoelectrochemical biosensing platform based on oxygen-sensitive near-infrared quantum dots (NIR QDs) was developed for detection of glucose. The NIR QDs were synthesized in an aqueous solution, and characterized with scanning electron microscopy and X-ray photoelectron spectroscopy. The as-prepared NIR QDs were employed to construct oxygen-sensitive photoelectrochemical biosensor on a fluorine-doped tin oxide (FTO) electrode. The oxygen dependency of the photocurrent was investigated at as-prepared electrode, which demonstrated the signal of photocurrent is suppressed with the decreasing of oxygen. Coupling with the consumption of oxygen during enzymatic reaction, a photoelectrochemical strategy was proposed for the detection of substrate. Using glucose oxidase (GOx) as a model enzyme, that is, GOx was covalently attached to the surface of CdTe QDs, the resulting biosensor showed the sensitive response to glucose. Under the irradiation of visible light of a wavelength at 505 nm, the proposed photoelectrochemical method could detect glucose ranging from 0.1 mM to 11 mM with a detection limit of 0.04 mM. The photoelectrochemical biosensor showed a good performance with high upper detection limit, acceptable stability and accuracy, providing an alternative method for monitoring biomolecules and extending the application of near-infrared QDs.     

Fabrication of glutathione photoelectrochemical biosensor using graphene-CdS nanocomposites

A novel glutathione (GSH) photoelectrochemical biosensor was fabricated using the newly synthesized graphene-CdS (GR-CdS) nanocomposites. The GR-CdS nanocomposites were prepared by a fast, one-step, aqueous reaction. The as-prepared GR-CdS structure inherited the excellent electron transport of GR and facilitated the spatial separation of photo-generated charge carrier, therefore resulting in the enhanced photocurrent, and making it a promising candidate for developing photoelectrochemical biosensors. The proposed GSH sensor displays satisfactory analytical performance with an acceptable linear range from 0.01 to 1.5 mmol L(-1) with a detection limit of 0.003 mmol L(-1) at a signal-to-noise ratio of 3, and also shows an excellent specificity against anticancer drugs and can be successfully applied for GSH detection in real samples. The as-synthesized GR-CdS nanocomposites exhibited obviously enhanced photovoltaic properties, which could be extended to the detection of other enzymes and biomolecules, thus providing a promising platform for the development of photoelectrochemical biosensors.     

Structure and photoelectrochemical properties of phthalocyanine and perylene diimide composite clusters deposited electrophoretically on nanostructured SnO2 electrodes

Clusters of phthalocyanine and phthalocyanine-perylene diimide have been prepared and electrophoretically deposited on nanostructured SnO2 electrodes. The structure and photoelectrochemical properties of the clusters have been investigated by using UV-visible absorption, dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM), and photoelectrochemical and photodynamical measurements. Enhancement of the photocurrent generation efficiency in the composite system has been achieved relative to that in the phthalocyanine reference system without the perylene diimide. Such information will be valuable for the design of molecular photoelectrochemical devices that exhibit efficient photocurrent generation.     

Stabilization of oxygen evolution and primary electron transport reactions in photosystem II against heat stress with glycinebetaine and sucrose

The protective action of co-solutes, such as sucrose and glycinebetaine, against the thermal inactivation of photosystem II function was studied in untreated and Mn-depleted photosystem II preparations. It was shown that, in addition to the reactions that depend on the oxygen evolving activity of the photosystem, those that implicate more intimately the reaction center itself are protected by high concentrations of osmolytes. However, the temperature required to inhibit oxygen evolution totally in the presence of osmolytes is lower than that required to eliminate reactions, such as P680 (primary electron donor in photosystem II) photo-oxidation and pheophytin photo reduetion, which only involve charge separation and primary electron transport processes. The energy storage measured from the thermal dissipation yield during photoacoustic experiments and the yield of variable fluorescence are also protected to a significant degree (up to 30%) at temperatures at which oxygen evolution is totally inhibited. It is suggested that a cyclic electron transport reaction around photosystem II may be preserved under these conditions and may be responsible for the energy storage measured at relatively high temperatures. This interpretation is also supported by thermoluminescence data involving the recombination between reduced electron acceptors and oxidized electron donors at - 30 and - 55 °C. The data also imply that a high concentration of osmolyte allows the stabilization of the photosystem core complex together with the oxygen-evolving complex. The stabilization effect is understood in terms of the minimization of protein-water interactions as proposed by the theory of Arakawa and Timasheff (Biophys. J., 47 (1985) 411--414).     

Titania nanocomposite films derived by modified sol-gel process for photovoltaic application

Titania nanocomposite films were fabricated by spin-coating from sol-gel derived pastes of TiO₂ powder in titanium isopropoxide sol. The thin films were characterized for structural, optical and hydrophilic properties and evaluated as electrodes in a photoelectrochemical cell. Addition of TiO₂ powder increased film thickness, reduced transmittance, water contact angle and electrochemical impedance, and promoted photocurrent generation. Increasing Triton X-100 surfactant loading in the composite slurry influenced film texture and transmittance, and the resultant films exhibited a lower photocurrent yield but were more hydrophilic to favor charge transfer at the electrode/electrolyte interface. The aggregation of TiO₂ particles of different sizes in the composite film facilitates light-scattering and electron transport to enhance quantum efficiency. The addition of Triton X-100 surfactant influences the distribution of scattering centers to increase transparency.     

Graphene–CdS Nanocomposites: Facile One‐Step Synthesis and Enhanced Photoelectrochemical Cytosensing

Graphene–CdS (GR–CdS) nanocomposites were prepared in a one‐step synthesis in aqueous solution. The synthetic approach was simple and fast, and it may be extended for the synthesis of other GR–metal‐sulfide nanocomposites. The as‐prepared GR–CdS nanocomposite films inherited the excellent electron‐transport properties of GR. In addition, the heteronanostructure of the GR–CdS nanocomposites facilitated the spatial separation of the charge carriers, thus resulting in enhanced photocurrent intensity, which makes it a promising candidate for photoelectrochemical applications. This strategy was used for the fabrication of an advanced photoelectrochemical cytosensor, based on these GR–CdS nanocomposites, by using a layer‐by‐layer assembly process. This photoelectrochemical cytosensor showed a good photoelectronic effect and cell‐capture ability, and had a wide linear range and low detection limit for Hela cells. The as‐synthesized GR–CdS nanocomposites exhibited obviously enhanced photovoltaic properties, which could be an efficient platform for many other high‐performance photovoltaic devices.     

后处理对TiO_2纳米晶膜电极光电性能的改善(英文)

利用TiCl4 水溶液处理TiO2 纳米晶膜电极 ,可以提高光电流 ,改善电极的光电转换性能 .对未经处理和处理后电极的比表面、孔分布 ,以及瞬态光电流分析表明 ,后处理改善了电荷在电极中的传输 ,从而提高了光电流     

Exploitation of a photoelectrochemical sensing platform for bisphenol A quantitative determination using Cu/graphitic carbon nitride nanocomposites

The photoelectrochemical sensor basedon Cu/g-CN composites modified electrodeis firstly used to monitor bisphenol Awith high sensitivity. This work opens theway for the application of Cu/g-CN composites in photoelectrochemical field, and simultaneously contributed to broadening the application of graphitic carbon nitride-based materials. In addition, it can provide a convenient and rapid analysis method for the detection of other organic compounds in the future.     

LIGHT-INDUCED ELECTRON TRANSPORT ACROSS SEMICONDUCTOR ELECTRODE/REACTION-CENTER FILM/ELECTROLYTE INTERFACES

Abstract— Reaction center (RC) complexes isolated from the photosynthetic bacterium Rhodopseudomonas sphaeroides R-26 were dried as a film onto platinum and semiconductor (SnO₂) electrodes. The light-induced primary charge separation which occurs across the biological complex couples electrically with the SnO₂ but not with the metal electrode on the time scale of observation. As the working electrode in a two-electrode photoelectrochemical cell, RC-coated SnO₂ generated photovoltages as high as 80 mV and photocurrents as high as 0.5µA·cm² when exposed to light of λ >600nm. The number of quinone molecules per RC strongly influences the photovoltage and photocurrent observed. Photo-effects generated by RC electrodes persist after several days of storage; however, the kinetics and polarity of the effects are subject to change. The potential use of RC electrodes lies more as a new probe of photosynthetic electron transport rather than as a solar energy conversion device because modification to the RCs and their environment affect the electrical properties of the cell. An energy-level model is proposed to explain how the photoelectrochemical cell functions.     

Single‐Nanoparticle Photoelectrochemistry at a Nanoparticulate TiO2‐Filmed Ultramicroelectrode

An ultrasensitive photoelectrochemical method for achieving real‐time detection of single nanoparticle collision events is presented. Using a micrometer‐thick nanoparticulate TiO₂‐filmed Au ultra‐microelectrode (TiO₂@Au UME), a sub‐millisecond photocurrent transient was observed for an individual N719‐tagged TiO₂ (N719@TiO₂) nanoparticle and is due to the instantaneous collision process. Owing to a trap‐limited electron diffusion process as the rate‐limiting step, a random three‐dimensional diffusion model was developed to simulate electron transport dynamics in TiO₂ film. The combination of theoretical simulation and high‐resolution photocurrent measurement allow electron‐transfer information of a single N719@TiO₂ nanoparticle to be quantified at single‐molecule accuracy and the electron diffusivity and the electron‐collection efficiency of TiO₂@Au UME to be estimated. This method provides a test for studies of photoinduced electron transfer at the single‐nanoparticle level.     

CYCLIC VOLTAMMETRY MEASUREMENTS OF THE PHOTOELECTROGENIC REACTIONS OF THYLAKOID MEMBRANES

Abstract— In this paper, the technique of cyclic voltammetry has been used in a photoelectrochemical cell in order to follow the redox species formed in solution by the photo-induced electron transfer between the thylakoids and various acceptors and donors. The photoelectrochemical behavior of artificial electron acceptors (such as 2,5-dichlorobenzoquinone and methylviologen) and donors (such as sym -diphenylcarbazide and durohydroquinone) specific for either Photosystem I or Photosystem II has been investigated. The influence of inhibiting agents (such as 3-(3,4-dichlorophenyl)-1,1-dimethylurea and Tris) on the cell photoresponse has also been characterized, together with the capability of donors to restore the photocurrent. Evidence for H₂O₂ formation by way of a Mehler-type reaction has been provided and an electrochemical model of its coupled photochemical and electrochemical reactions in solution is reported.     

Dependence of the photoelectrochemical performance of sensitised ZnO on the crystalline orientation in electrodeposited ZnO thin films

The influence of the crystal orientation in porous crystalline films of ZnO electrodeposited on the photoelectrochemical characteristics of the films is studied. For differently oriented ZnO thin films following removal of the respective structure-directing agent (SDA) and adsorption of a sensitiser, time-resolved photocurrent measurements, intensity modulated photocurrent spectroscopy (IMPS), intensity modulated photovoltage spectroscopy (IMVS) and current-voltage curves were measured in acetonitrile-based electrolytes containing I(3)(-)/I(-) as the redox electrolyte. The crystal orientation has a significant influence on the charge transport across such films and hence is reflected in the observed electrode kinetics. Films originally grown in the presence of, e.g., Coumarin 343 as a SDA, showed a significantly faster response to illumination. Increased electron diffusion coefficients and diffusion lengths were calculated from the results of IMPS and IMVS, caused by a faster electron movement in the films. Implications of these findings on further improvements of sensitised ZnO films prepared by electrochemical deposition are discussed.     

Time-resolved photocurrent generation in a photoelectrochemical cell with phthalocyanine

The kinetics of photocurrent generated in the photoelectrochemical cell (PEC) with phthalocyanine (Pc) dyes in the microsecond time scale was discussed. The shape of the kinetics is rather complex and it was discussed in terms of molecular phenomena and electrochemical processes occurring after laser flash illumination. Time constants were calculated from the photocurrent decay curves and at least three time components were well recognized (rise in 0.40 micros, declining in 0.40-0.45 micros and secondary increase in about 2 micros). The shape of the kinetics was discussed in terms of dye singlet and triplet state participation in photocurrent generation and also in terms of creation of the Helmholtz-Goy double layer at the dye layer-semiconductor interface. The alteration in shape of the Helmholtz-Goy double layer in photoelectrochemical cell after laser pulse was also discussed.     

Quantum dot solar cells. Tuning photoresponse through size and shape control of CdSe-TiO2 architecture

Different-sized CdSe quantum dots have been assembled on TiO2 films composed of particle and nanotube morphologies using a bifunctional linker molecule. Upon band-gap excitation, CdSe quantum dots inject electrons into TiO2 nanoparticles and nanotubes, thus enabling the generation of photocurrent in a photoelectrochemical solar cell. The results presented in this study highlight two major findings: (i) ability to tune the photoelectrochemical response and photoconversion efficiency via size control of CdSe quantum dots and (ii) improvement in the photoconversion efficiency by facilitating the charge transport through TiO2 nanotube architecture. The maximum IPCE (photon-to-charge carrier generation efficiency) obtained with 3 nm diameter CdSe nanoparticles was 35% for particulate TiO2 and 45% for tubular TiO2 morphology. The maximum IPCE observed at the excitonic band increases with decreasing particle size, whereas the shift in the conduction band to more negative potentials increases the driving force and favors fast electron injection. The maximum power-conversion efficiency 相似文献   

Electron Interaction Among the Noncovalently Engineered Graphene-methylene Blue Nanocomposites

The electron interaction among the noncovalently engineered graphene-methylene blue(MB) nanocomposite with a dipolar pull-push hybrid model was studied. The π-π interaction between reduced graphene oxide(rGO) and MB molecule was studied by ¹HNMR spectroscopy. The electrochemical investigation indicates MB has a stronger electron transfer interaction with rGO than with GO. The ability of graphene-MB nanocomposites to undergo photoinduced electron transfer was confirmed from the capability of the nanocomposites coated electrode to generate photocurrent in a photoelectrochemical cell. The role of graphene as electron acceptor in the opto-electronic assembly was discussed.     

石墨烯氧化物薄膜电极的光电化学特性

采用浸渍-提拉法制备了一系列石墨烯氧化物(GO)薄膜,并通过X射线衍射(XRD),扫描电镜(SEM),傅里叶变换红外光谱,紫外-可见吸收光谱和光电化学测量等技术对样品进行了表征.在GO电极上观察到阴极光电流,且光电流密度受薄膜的厚度影响.GO薄膜电极厚度为27nm时,光电流密度为0.25μA·cm-2.此外,GO电极的光电响应还受紫外光照影响,随着紫外光照时间的延长,阴极光电流逐渐减小.该工作提供了简便的通过控制薄膜厚度或紫外光照时间来控制GO薄膜半导体光电化学性能的方法.     

Photosensitization of TiO2 nanoparticulate thin film electrodes by CdS nanoparticles

Surface photovoltage spectra (SPS) measurements of TiO₂ show that a large surface state density is present on the TiO₂ nanoparticles and these surface states can be efficiently decreased by sensitization using CdS nanoparticles as well as by suitable heat treatment. The photoelectrochemical behavior of the bare TiO₂ thin film indicates that the mechanism of photoelectron transport is controlled by the trapping/detrapping properties of surface states within the thin films. The slow photocurrent response upon the illumination can be explained by the trap saturation effect. For a TiO₂ nanoparticulate thin film sensitized using CdS nanoparticles, the slow photocurrent response disappears and the steady-state photocurrent increases drastically, which suggests that photosensitization can decrease the effect of surface states on photocurrent response. Electronic Publication