A photoelectrochemical device with a nanostructured SnO2 electrode modified with composite clusters of porphyrin-modified silica nanoparticle and fullerene

A silica nanoparticle has been successfully employed as a nanoscaffold to self-organize porphyrin and C60 molecules on a nanostructured SnO2 electrode. The quenching of the porphyrin excited singlet state on the silica nanoparticle is suppressed significantly, showing that silica nanoparticles are promising scaffolds for organizing photoactive molecules three-dimensionally in nanometer scale. Marked enhancement of the photocurrent generation was achieved in the present system compared with the reference system, where a gold core was employed as a scaffold of porphyrins instead of a silica nanoparticle. The rather small incident photon-to-current efficiency relative to a similar photoelectrochemical device using a silica microparticle may result from poor electron and hole mobility in the composite film due to poor connection between the composite clusters of a porphyrin-modified silica nanoparticle and C60 in micrometer scale.     

Structure and photoelectrochemical properties of nanostructured SnO2 electrodes deposited electrophoretically with the composite clusters of porphyrin-modified gold nanoparticle with a long spacer and fullerene

Structure and photoelectrochemical properties of nanostructured SnO₂ electrodes deposited electrophoretically with the composite clusters of porphyrin-modified gold nanoparticle with a long, flexible spacer and C₆₀ molecules have been examined to obtain basic information on the development of organic solar cells with a high performance. The photoelectrochemical system with the long, flexible spacer between the porphyrin and the gold nanoparticle in the porphyrin-modified gold nanoparticle exhibited comparable external quantum yield in the UV-vis regions relative to porphyrin-modified gold nanoparticle with a relatively short spacer—C₆₀ composite reference system. These results demonstrate that a suitable spacer to incorporate C₆₀ molecules efficiently between the porphyrins in porphyrin-modified gold nanoparticles is a prerequisite for improving the performance of porphyrin and fullerene-based organic solar cells.     

Effects of porphyrin substituents on film structure and photoelectrochemical properties of porphyrin/fullerene composite clusters electrophoretically deposited on nanostructured SnO2 electrodes

We have systematically examined the substituent effects of meso-tetraphenylporphyrins on film structures and the photoelectrochemical properties of the composite clusters of free-base porphyrin and C(60) electrophoretically deposited on nanostructured SnO(2) electrodes. The photocurrent generation efficiency was found to correlate with the complexation ability of the porphyrin for C(60). Basically, the incident photon-to-current efficiency (IPCE) value was increased with increasing relative amounts of the porphyrin versus C(60) in the films. The unique molecular arrangement of the porphyrin with the simple, specific substituents (i.e., methoxy groups at the meta-positions of the meso-phenyl rings of tetraphenylporphyrins (3,5-OMeTPP; TPP=tetraphenylporphyrin)) and C(60) on SnO(2) electrodes resulted in the largest IPCE value (ca. 60 %) among this type of photoelectrochemical device. The rapid formation of the composite clusters and microcrystals from the combination of 3,5-OMeTPP and C(60) in a mixed solvent is unique as the association is accelerated by intermolecular interactions (i.e., hydrogen-bonding and CH-pi interactions) between the methoxy groups of the porphyrins and the porphyrin/C(60), in addition to the pi-pi interactions between the porphyrins/C(60) and C(60) molecules. Both the films and single crystals composed of the porphyrin and C(60) exhibited remarkably high electron mobility (7x10(-2) and 0.4 cm(2) V(-1) s(-1)), which is comparable to the value for highly efficient bulk heterojunction solar cells. Our experimental results have successfully demonstrated the importance of nanostructured electron- and hole-transporting pathways in bulk heterojunction solar cells. Such a finding will provide basic and valuable information on the design of molecular photovoltaics at the molecular level.     

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.     

Effects of fullerene substituents on structure and photoelectrochemical properties of fullerene nanoclusters electrophoretically deposited on nanostructured SnO2 electrodes

Two kinds of fullerene derivatives have been designed to examine the effect of the fullerene substituents on the structure and photoelectrochemical properties of fullerene clusters electrophoretically deposited on nanostructured SnO(2) electrodes. The cluster sizes increase and the incident photon-to-current efficiencies decrease with introduction of large substituents into C(60). The trend for photocurrent generation efficiency as well as surface morphology on the electrode can be explained by the steric bulkiness around the C(60) molecules. A C(60) molecule with two alkoxy chains is suggested to give a bilayer vesicle structure, irrespective of the hydrophobic nature of both the C(60) and alkoxy chain moieties. Such information will be valuable for the design of photoactive molecules, which are fabricated onto electrode surfaces to exhibit high energy conversion efficiency.     

Adsorption of midmolecular peptides by fullerene modified silica gel

The adsorption properties of raw and processed silica gels and of silica gels modified with fullerene (fullerene-silica gel nanosystems) toward serum midmolecular peptides of ischemic origin were examined. A high adsorption capacity of the nanosorbents was found. The influence of fullerenes on the condition of silica gel was studied by solid-state NMR, and an increase in the silanol fraction at the adsorbent surface was demonstrated. It was shown that presence of fullerene C₆₀ in nanosorbents enables oxidation reaction of the adsorbed peptides, i.e., sorption of metabolites.     

Light-harvesting and photocurrent generation by gold electrodes modified with mixed self-assembled monolayers of boron-dipyrrin and ferrocene-porphyrin-fullerene triad

Three different kinds of mixed self-assembled monolayers have been prepared to mimic photosynthetic energy and electron transfer on a gold surface. Pyrene and boron-dipyrrin were chosen as a light-harvesting model. The mixed self-assembled monolayers of pyrene (or boron-dipyrrin) and porphyrin (energy acceptor model) reveal photoinduced singlet-singlet energy transfer from the pyrene (or boron-dipyrrin) to the porphyrin on the gold surface. The boron-dipyrrin has also been combined with a reaction center model, ferrocene-porphyrin-fullerene triad, to construct integrated artificial photosynthetic assemblies on a gold electrode using mixed monolayers of the respective self-assembled unit. The mixed self-assembled monolayers on the gold electrode have established a cascade of photoinduced energy transfer and multistep electron transfer, leading to the production of photocurrent output with the highest quantum yield (50 +/- 8%, based on the adsorbed photons) ever reported for photocurrent generation at monolayer-modified metal electrodes and across artificial membranes using donor-acceptor linked molecules. The incident photon-to-current efficiency (IPCE) of the photoelectrochemical cell at 510 and 430 nm was determined as 0.6% and 1.6%, respectively. Thus, the present system provides the first example of an artificial photosynthetic system, which not only mimics light-harvesting and charge separation processes in photosynthesis but also acts as an efficient light-to-current converter in molecular devices.     

Photoelectrochemical properties of supramolecular composite of fullerene nanoclusters and 9-mesityl-10-carboxymethylacridinium ion on SnO2

[structure: see text] The photovoltaic cell composed of both fullerene nanoclusters and 9-mesityl-10-carboxymethylacridinium ion exhibits significant enhancement in the photoelectrochemical performance as well as broader photoresponse in the visible and near-infrared regions as compared with the reference system containing only each component.     

Hydrogen bonding effects on the surface structure and photoelectrochemical properties of nanostructured SnO2 electrodes modified with porphyrin and fullerene composites

Hydrogen bonding effects on surface structure, photophysical properties, and photoelectrochemistry have been examined in a mixed film of porphyrin and fullerene composites with and without hydrogen bonding on indium tin oxide and nanostructured SnO2 electrodes. The nanostructured SnO2 electrodes modified with the mixed films of porphyrin and fullerene composites with hydrogen bonding exhibited efficient photocurrent generation compared to the reference systems without hydrogen bonding. Atomic force microscopy, infrared reflection absorption, and ultraviolet-visible absorption spectroscopies and time-resolved fluorescence lifetime and transient absorption spectroscopic measurements disclosed the relationship between the surface structure and photophysical and photoelectrochemical properties relating to the formation of hydrogen bonding between the porphyrins and/or the C60 moieties in the films on the electrode surface. These results show that hydrogen bonding is a highly promising methodology for the fabrication of donor and acceptor composites on nanostructured semiconducting electrodes, which exhibit high photoelectrochemical properties.     

Highly sensitive deoxynivalenol immunosensor based on a glassy carbon electrode modified with a fullerene/ferrocene/ionic liquid composite

We describe a sensitive electrochemical immunosensor for the detection of deoxynivalenol (DON). It is based on a glassy carbon electrode modified with a composite made from fullerene (C₆₀), ferrocene and the ionic liquid. The components were immobilized on the surface of the electrode using chitosan cross-linked with epichlorohydrin. Then, the antibody to DON was covalently conjugated to the surface which then was blocked with serum albumin. The performance of the immunosensor was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. It offers good repeatability (RSD?=?1.2%), selectivity, a stability of more than 180?days, an impedimetric response to DON in the range of 1?pgmL^?1 to 0.3?ng?mL^?1, and a detection limit (at S/N?=?3) of 0.3?pgmL^?1. The limit of detection is better than that of GC, HPLC, GC-MS, HPLC-MS and LC-MS-MS. The effects of omitting C₆₀ or the ionic liquid were also examined. The results indicate that the sensitivity of the biosensor is 2-fold better if C₆₀ and ionic liquids are used. This demonstrates that C₆₀ facilitates electron transfer on the surface of the modified electrode due to its unique electrochemical properties, while the ionic liquid provides a biocompatible microenvironment for the antibody. This results in increased sensitivity and stability. The method was satisfactorily applied to the determination of DON in food samples.

Efficient CO2 capture on low-cost silica gel modified by polyethyleneimine

In this work,a series of polyethyleneimine(PEI) functionalized commercial silica gel were prepared by wet impregnation method and used as CO 2 sorbent.The as-prepared sorbents were characterized by N 2 adsorption,FT-IR and SEM techniques.CO 2 capture was tested in a fixed bed reactor using a simulated flue gas containing 15.1% CO 2 in a temperature range of 25-100 C.The effects of sorption temperature and amine content on CO 2 uptake of the adsorbents were investigated.The silica gel with a 30 wt% PEI loading manifested the largest CO 2 uptake of 93.4 mg CO 2 /g adsorbent(equal to 311.3 mg CO 2 /g PEI) among the tested sorbents under the conditions of 15.1%(v/v) CO 2 in N 2 at 75 C and atmospheric pressure.Moreover,it was rather low-cost.In addition,the PEI-impregnated silica gel exhibited stable adsorption-desorption behavior during 5 consecutive test cycles.These results suggest that the PEI-impregnated silica gel is a promising and cost-effective sorbent for CO 2 capture from flue gas and other stationary sources with low CO 2 concentration.     

Electrochemical determination of maltol in beverages with glassy carbon electrode and its silica sol-gel modified electrode

The electrochemical behavior of maltol on a glassy carbon (GC) electrode was investigated. The results were applied to differential pulse voltammetric determination of maltol in beverages pretreated by ultrafiltration. Under the optimum experimental conditions, the linear range is 1×10⁻⁵ to 6×10⁻⁴ mol l⁻¹ maltol and the relative standard deviation for 0.4 mmol l⁻¹ maltol is 0.6% (n=9). The detection limit was 5 μmol l⁻¹. Furthermore, silica sol-gel film on GC electrode could be used as suitable selective membrane, which integrated selective membrane on the electrode and substituted for the pretreatment of ultrafiltration. Under the above conditions, maltol was determined by semi-differential linear sweep voltammetry at a silica sol-gel modified GC electrode in the concentration range of 5×10⁻⁶ to 5×10⁻⁴ mol l⁻¹. The detection limit was 2 μmol l⁻¹ and the relative standard deviation for 0.1 mmol l⁻¹ maltol was 0.7% (n=7). The proposed method is of sensitivity, simplicity, rapidness and no contamination. It had been applied to the direct determination of maltol in beverages such as grape wines, drinks and beers without any pretreatment. The results obtained with the present method were satisfactory with those obtained by spectrophotometry. It could be used as a simple and practical method for the determination of the flavor enhancer maltol in beverages.     

A glassy carbon electrode modified with SnO2 nanofibers,polyaniline and hemoglobin for improved amperometric sensing of hydrogen peroxide

Microchimica Acta - The authors describe a glassy carbon electrode (GCE) modified with a multiporous nanofibers prepared from SnO2, polyaniline and hemoglobin, and its application to the...     

XPS study of the SnO2 films modified with Rh

In this paper, we have analyzed the effect of the rhodium surface modification on the surface state of SnO₂ films. SnO₂ films, subjected for the surface modification, were deposited by spray pyrolysis, while Rh was deposited by using a microelectron beam evaporation. The thickness of the Rh coating varied in the range 0 to 0.1 monolayer. An explanation of the observed effects was proposed. Basing on the results of X‐ray photoelectron spectroscopy, it was assumed that at a small thickness of the rhodium covering, Rh was in a the well‐dispersed state, close to atomically dispersed state. The growth in the size of the nanoparticles began mainly when the thickness of the Rh covering exceeeded 0.01 monolayer. The size of clusters did not exceed 0.5 to 1.0 nm.     

铜卟啉-L-半胱氨酸自组装复合膜修饰电极的制备及电化学性能研究

利用电化学扫描法在L 半胱氨酸(Cys)自组装单分子膜修饰金电极表面现场制备了金属卟啉复合膜,对其进行SEM和ATR FTIR表征。修饰电极的支持电解质以及pH值对膜的稳定性和灵敏度有很大影响。铜卟啉 L Cys膜对H2O2具有良好的电催化还原特性,催化电流与H2O2浓度在1 0×10 6到3 0×10 5mol·L 1范围内线性关系,相关系数0 9995,检测限达1 0×10 7mol·L 1。     

Supramolecular design of a porphyrin-[60]fullerene photocurrent generation system on a DNA scaffold fabricated by a conjugate polymer film

DNA which binds monocationic [60]fullerene (1) and tetracationic porphyrin (TMPyP) was readily fabricated by electrochemical oxidative polymerization of 3.4-ethylenedioxythiophene (EDOT) and the resultant poly(EDOT) composite was deposited on an ITO electrode as a stable thin film. Spectral and CV analyses established that one 1 and one TMPyP are bound per 57 nucleobase units, that is, every three pitches of DNA. Photoirradiation of this 1/TMPyP/DNA-poly(EDOT) film generated a photocurrent in 3.8% quantum yield, which was much higher than those obtained from 1/DNA and TMPyP/DNA systems. One can conclude, therefore that the photoexcited energy of TMPyP is transferred to 1, which is collected by the electron-conducting poly(EDOT) film. The present paper shows that DNA is useful as a scaffold to arrange redox-active couples in a one-dimensional matrix.     

Quaternary self-organization of porphyrin and fullerene units by clusterization with gold nanoparticles on SnO2 electrodes for organic solar cells

Novel organic solar cells prepared using quaternary self-organization of porphyrin (donor) and fullerene (acceptor) dye units by clusterization with gold nanoparticles on SnO2 electrodes exhibit the remarkable enhancement of the photoelectrochemical properties relative to the reference systems.     

Detection of H_2O_2 at a composite film modified electrode with highly dispersed Ag nanoparticles in Nafion

Ag nanoparticles were prepared by using the ion-exchange of Nafion combined with electrochemical reduction on the electrode. Ag nanoparticles are highly dispersed in Nafion film with an average size of 4.0±0.2 nm.The amount of Ag nanoparticles can be readily controlled by the amount of Nafion coated on the electrode.Thus obtained Ag nanoparticles exhibit good catalytic activity for the reduction of H₂O₂ with a linear response to H₂O₂ in the concentration range of 0.04-8.0 mmol/L with a sensitivity of 0.34μA/mmol/L and a detection limit of 1.0×10^-8 mol/L.     

石墨烯/碳纳米管复合膜修饰电极检测亚硝酸根

本研究先采用滴涂法制备了多壁碳纳米管修饰电极,然后采用电化学沉积技术从含有氧化石墨烯的溶液中制备了石墨烯(GR)/多壁碳纳米管(MWCNT)复合膜修饰电极(GR/MWCNT/GCE)。研究了亚硝酸根(NO2-)在该修饰电极上的电化学行为。结果表明,该修饰电极对亚硝酸根的电氧化具有高的催化活性。在pH 7.00的PBS缓冲溶液中,微分脉冲伏安法测定亚硝酸根的线性范围为1.0×10-7mol·L-1~1.7×10-3mol·L-1,检出限为5.0×10-8mol·L-1(S/N=3)。用该法测定了土壤中亚硝酸根的含量,结果令人满意。