Good Electron Transfer Ability Research Articles

3D graphene aerogel composite of 1D-2D Nb2O5-g-C3N4 heterojunction with excellent adsorption and visible-light photocatalytic performance

A novel three-dimensional graphene aerogel composite Nb2O5-g-C3N4/rGA was prepared, with a composition of nanorods-nanosheets Nb2O5-g-C3N4 (NbNR-CN) heterojunction and graphene aerogel (rGA). The 1D-2D NbNR-CN heterojunction was first prepared by a simple grinding and calcination method. Afterwards, different amounts of NbNR-CN (30%, 60%, 90%) were loaded onto graphene nanosheets by chemical reduction self-assembly method to obtain the 3D composites Nb2O5-g-C3N4/rGA (NbNR-CN/rGA). The compositions, morphologies, and optical properties of all materials were characterized. The results showed that the obtained 1D-2D heterojunctions were uniformly loaded onto rGA and the NbNR-CN/rGA composites had good visible light response. Compared with g-C3N4, NbNR and NbNR-CN, NbNR-CN/rGA showed the lowest charge transfer resistance and the highest photocurrent density. Photodegradation experiments indicated that the NbNR-CN/rGA composites exhibited remarkably enhanced visible-light photocatalytic activity for degradation of Rhodamine B (RhB). The removal rate for the 60%NbNR-CN/rGA composite was 94.8% within 100 min. The enhanced photoactivity could be explained by prolonged lifetime of photogenerated carriers due to the formation of heterojunction as well as the good electron transfer ability of rGA. Our research demonstrated that the NbNR-CN/rGA composite is a promising candidate for visible-light photocatalyst.

Amperometric sarcosine biosensor based on hollow magnetic Pt–Fe3O4@C nanospheres

Sarcosine is a recently identified biomarker for prostate cancer. However, the rapid detection methods for sarcosine are relatively lack because of the low concentration and the presence of complicated interfering substances in serum or urine. In this manuscript, hollow nanospheres of Fe3O4 was synthesized and used as carrier to disperse Pt (Pt) nanoparticles. In order to achieve excellent electron transfer ability, we use polyaniline to coat Pt–Fe3O4 nanoparticles, and pyrolyze the polyaniline to carbon (C). Thus, hollow magnetic Pt–Fe3O4@C nanocomposites with good electron transfer ability are formed. The Pt–Fe3O4@C nanocomposites have high catalytic activity and stability. The nanocomposites were immobilized on glassy carbon electrode (GCE) to construct a nonenzyme hydrogen peroxide (H2O2) sensor (Pt–Fe3O4@C/GCE). We further construct a sensitive sarcosine biosensor by immobilizing sarcosine oxidase (SOx) on the Pt–Fe3O4@C/GCE. The high catalytic activity and good biocompatibility of Pt–Fe3O4@C nanocomposites greatly retained the bioactivity of immobilized SOx, and the prepared sarcosine biosensor has good electrocatalytic performance towards sarcosine. It has a linear detection range between 0.5 and 60 μM with a limit of detection (LOD) of 0.43 μM (the signal to noise ratio is 3), and the sensitivity is 3.45 nA μM−1 (48.8 nA μM−1 cm−2), which has the potential to be used for rapid screening of prostate cancer.

A highly sensitive electrochemiluminescence sensor for the detection of l-cysteine based on the rhombus-shaped rubrene microsheets and platinum nanoparticles

We present a highly sensitive platinum nanoparticles (PtNPs), rhombus-shaped rubrene microsheets (RubRMs) and dissolved oxygen (O2) system for the monitoring of l-cysteine by the quenched electrochemiluminescence (ECL) signals. Firstly, RubRMs has been prepared through reprecipitation method, then the metal organic composites of PtNPs-RubRMs was synthesized by a simple in situ reduction of PtNPs on RubRMs surface. The composites combined the high ECL characteristic of RubRMs, the wonderful catalytic efficiency and good electron transfer ability of PtNPs. With the synergistic effect between RubRMs and PtNPs, the proposed ECL sensors exhibited excellent responses for l-cysteine. Under the optimum conditions, the linear range was from 1.0 × 10−9 mol L-1 to 5.0 × 10-4 mol L-1 with a detection limit of 3.3 × 10-10 mol L-1 (S/N = 3). And the results shows high sensitivity, excellent stability, and low background signal. It is simple to prepare and operate for the practical application.

In-situ preparation and properties of gold nanoparticles embedded polypyrrole composite

A composite was formed by polypyrrole (Ppy), gold nanoparticles (AuNPs) and multi-walled carbon nanotubes (MWCNT) using chloroauric acid (HAuCl4). MWCNT were carboxy functionalized by oxidation resulting into oxidized MWCNT (OMWCNT). The composite was characterized spectroscopically, structurally and morphologically by Fourier transform infrared (FT-IR) spectroscopy, Ultraviolet-visible (UV-Vis) spectroscopy, X-ray photoelectron spectrocopy (XPS), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and High-resolution transmission electron microscopy (HRTEM) studies which revealed about its successful formation. UV-Vis spectroscopy suggested the in-situ formation of AuNPs, their dispersion into the composite and presence of OMWCNT. XPS analysis revealed the existence of Au, C, N and O elements, signifying the desired formation of the composite. Morphological studies depicted the wrapping of OMWCNT by Ppy along with the presence of dispersed AuNPs. Its electrochemical examination suggested good electron transfer ability of AuNPs and OMWCNT. The interaction of composite with Cd2+ ions was investigated both optically and electrochemically, making it a potential candidate for Cd2+ sensing. Furthermore, its catalytic activity was also shown, by reduction of methylene blue dye.

Electrochemical immunosensor for ochratoxin A detection based on Au octahedron plasmonic colloidosomes

The accurate and rapid fungaltoxin detection at early stage can prevent people from getting cancer to a great extent. Here, an ultrasensitive electrochemical immunosensor for the detection of ochratoxin A was reported. Octahedral gold nanoparticles (Oct Au NPs) with edge and sharp corners as substrate materials can connect more primary antibodies and Au octahedron plasmonic colloidosomes (Au Oct PCs) were formed by the natural settlement of the Oct Au NPs in the inverse emulsion system. Au Oct PCs with high specific surface area and good electron transfer ability can hybridize with electron mediator toluidine blue to act as labels to amplify the output signal and ameliorate the stability of the immunosensor. The immunoassay was performed via the square wave voltammetry and showed a strong current response. The proposed immunosensor obtained a wide linear range from 0.1 pg mL−1 to 10 ng mL−1 and a low detection limit of 39 fg mL−1. This new strategy achieved favorable stability, reproducibility and selectivity, which had potential application in real sample analysis.

Effect of Germanium on the TiO2 Photoanode for Dye Sensitized Solar Cell Applications. A Potential Sintering Aid

Anatase titanium-germanium (TiO2-Ge) nanocomposite has been prepared by using colloidal suspension process and investigated for photoanode to be used in dye sensitized solar cell. Ge possesses lower band gap energy compared to TiO2 and has the capability to absorb infrared region of solar spectrum. Its remarkable absorption and good electron transfer ability due to lower band gap energy makes it a potential candidate material in the field of DSSCs to counter important disadvantages such as high probability of electron recombination reactions and absorption of small region (UV region) of solar spectrum. Another advantage is its low sintering temperature which proved to be an added advantage to increase inter-particle contact which in turn leads to improved electron transfer. Scanning electron microscopy (SEM), uv-vis spectroscopy and electron impedance spectroscopy (EIS) have been employed to evaluate the effect of Ge on TiO2photoanode.

A facile strategy for ZnFe2O4 coating preparing by electrophoretic deposition and its supercapacitor performances

The development of low-cost and efficient coating technology for ZnFe2O4 in the application of supercapacitor, electronic devices, chemical sensors, is desirable but remains a challenge. In this study, a facile fabrication of ZnFe2O4 coatings via electrophoretic deposition (EPD) methods has been realized by employing hydrothermal synthesized ZnFe2O4 nanoparticles as starting materials. Benefiting from systematic investigation for the deposition kinetic of ZnFe2O4 nanoparticles in the dispersion system of ethanol-acetylacetone with the addition of nitric acid, smooth ZnFe2O4 coating with good film characteristics was successfully and rapidly fabricated. With a preliminary study of ZnFe2O4 coatings as supercapacitor electrode, the specific capacitance decayed from 198 to 17.1 F g−1 when the deposition time increased from 0.5 to 10 min because of the poor electric conductivity. Therefore, an electrophoretic codeposition of ZnFe2O4 and conductive carbon material is necessary in the given application with desire of good electron transfer ability.

Ionic liquid-employed synthesis of Bi2E3 (E = S, Se, and Te) hierarchitectures: The case of Bi2S3 with superior visible-light-driven Cr(VI) photoreduction capacity

A general ionic-assisted microwave-ultrasonic combined synthetic strategy was developed to fabricate Bi2E3 (E=S, Se, and Te) hierarchitectures. To understand the crystal phase transformation and morphological evolution of Bi2S3 hierarchical nanostructures, the fabrication of Bi2S3 hierarchitectures was investigated by varying sulfidation time and chlorination time. A topotactic transformation from BiOCl microsphere to Bi2S3 hierarchitectures was proposed. It was found that the structure, size, and morphology of Bi2S3 hierarchitectures could be delicately engineered by varying chlorination time, alkyl chain length, and concentration of ionic liquid. Moreover, the as-prepared Bi2S3 hierarchitectures displayed superior capacity of Cr(VI) photoreduction to P25 and irregular Bi2S3 nanostructures under visible light irradiation. Effects of morphology, pH value of reaction system, Cr(VI) concentration, and catalyst dosage on the Cr(VI) photoreduction capacity of Bi2S3 hierarchitectures were also discussed. The enhancement of photoreduction capacity is not only attributed to the intrinsic good electron transfer ability of Bi2S3, but also to synergetic effects of special architectures, wide photoresponse range, high light photoadsorption, high BET surface area and good electron-hole separation performance. The systematic condition experiments and Cr(VI) photoreduction in electroplating and tannery wastewater experiments further demonstrated that the hierarchical Bi2S3 nanospheres can be used in the actual Cr(VI)-containing wastewater treatment.

Electrochemical sensor for sensitive detection of triclosan based on graphene/palladium nanoparticles hybrids

In this paper, poly (diallyldimethylammonium chloride) functionalized graphene/palladium nanoparticles (PDDA-Gr/PdNPs) have been successfully synthesized through a simple one-pot method with the use of PDDA as stabilizing agents. The electrochemical response of triclosan on the PDDA-Gr/PdNPs modified glassy carbon electrode (GCE) is greatly enhanced comparing to the PDDA-Gr/GCE or the bare GCE. It is suggested that the nanocomposite exhibited good electron transfer ability and catalytic activity. Under the optimal conditions, the oxidation current increased linearly with the concentration of triclosan in the range of 9.0nM to 20.0μM. The detection limit was estimated to be 3.5nM (S/N=3). Besides, the electrochemical sensor presented superior reproducibility, excellent anti-interference performance and long-term stability. What is more, the method is promising for the determination of trace amounts of triclosan in water samples.

Graphene oxide-polydopamine derived N, S-codoped carbon nanosheets as superior bifunctional electrocatalysts for oxygen reduction and evolution

Engineering carbon materials as the bifunctional catalysts for both electrocatalytic oxygen reduction/evolution reactions (ORR/OER) is highly promising for the large-scale commercialization of regenerative fuel cells and rechargeable metal-air batteries. Codoping carbons with heteroatoms can achieve unique electronic structures and show tailored electrocatalytic capabilities by rationally regulating their dopants. Sulfur is one of the most important dopants from both experimental and theoretical perspectives. In this work, a novel, highly efficient and environmentally benign method for sulfur incorporation into carbon framework has been developed facilely on the basis of graphene oxide-polydopamine (GD) hybrids to derive the N, S-codoped mesoporous carbon nanosheets. 16.7at% S can be conjugated to the GD hybrids associated with the S doping efficiency up to 6.1% after 800°C pyrolysis, which is higher than most previous S doping approaches. The resultant N, S-codoped mesoporous carbon nanosheets exhibit superior performance with favorable kinetics and excellent durability as a bifunctional ORR and OER catalyst, which is much better than that of most reported metal-free doped carbon, even transition metal and noble metal catalysts. The high concentrations of multiple dopants, abundant porous architecture and good electron transfer ability are believed to significantly expedite the ORR and OER catalytic processes. In the light of physicochemical versatility and structural tunability of polydopamine (PDA), this work provides a universal platform towards further development of PDA-based carbon materials with heteroatom dopants as the highly efficient electrocatalysts.

Electrochemical immunosensor based on Pd–Au nanoparticles supported on functionalized PDDA-MWCNT nanocomposites for aflatoxin B1 detection

This paper reports a label-free electrochemical immunosensor for the determination of aflatoxin B1 (AFB1), which is based on a gold electrode modified by a biocompatible film of carbon nanotubes/poly(diallyldimethylammoniumchloride)/Pd–Au nanoparticles (CNTs/PDDA/Pd–Au). The nanocomposite was characterized by transmission electron microscopy and the electrochemical behavior of modified electrodes was investigated by cyclic voltammetry. The CNTs/PDDA/Pd–Au nanocomposites film showed good electron transfer ability, which ensured high sensitivity to detect AFB1 in a range from 0.05 to 25 ng mL−1 with a detection limit of 0.03 ng mL−1 obtained at 3σ (where σ is the standard deviation of the blank solution, n = 10). The proposed immunosensor provides a simple tool for AFB1 detection. This strategy can be extended to any other antigen detection by using the corresponding antibodies.

Magnetic electrode-based label-free electrochemical impedance spectroscopy immunosensor for sensitive detection of human malignant melanoma markers using gold nanoparticles functionalized magnetic graphene sheets as signal amplifier

Cluster of differentiation 146 antigen (CD146) is a specific biomarker in the diagnosis of human malignant melanoma. In this work, a novel magnetic electrode-based label-free electrochemical impedance spectroscopy (EIS) immunosensor for quantitative detection of CD146 was established. Gold nanoparticles functionalized magnetic graphene sheets (Au@Fe3O4@GS) with good biocompatibility and electron transfer ability were used as transducing materials to achieve efficient conjugation of capture antibodies and signal amplification of the proposed immunosensor. For the facile and firm immobilization of magnetic transducing materials, the proposed immunosensor was fabricated on a magnetic glassy carbon electrode (MGCE). The effective immobilization of Au@Fe3O4@GS through the magnetic force of MGCE played a significant role in improving the stability and sensitivity of the proposed immunosensor. The EIS method was employed to record the impedance change of electrodes modified with different concentrations of CD146. The label-free EIS immunosensor exhibited a wide linear range from 5 pg mL−1 to 500 ng mL−1 with a low detection limit of 2.5 pg mL−1 for CD146. The proposed immunosensor displayed an electrochemical performance with good reproducibility, selectivity and stability, which could provide potential applications in the clinical diagnosis of biomarkers.

A novel reduction approach to fabricate quantum-sized SnO2-conjugated reduced graphene oxide nanocomposites as non-enzymatic glucose sensors

Quantum-sized SnO2 nanocrystals can be well dispersed on reduced graphene oxide (rGO) nanosheets through a convenient one-pot in situ reduction route without using any other chemical reagent or source. Highly reactive metastable tin oxide (SnO(x)) nanoparticles (NPs) were used as reducing agents and composite precursors derived by the laser ablation in liquid (LAL) technique. Moreover, the growth and phase transition of LAL-induced SnO(x) NPs and graphene oxide (GO) were examined by optical absorption, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and high-resolution transmission electron microscopy. Highly dispersed SnO(x) NPs can also prevent rGO from being restacked into a multilayer structure during GO reduction. Given the good electron transfer ability and unsaturated dangling bonds of rGO, as well as the ample electrocatalytic active sites of quantum-sized SnO2 NPs on unfolded rGO sheets, the fabricated SnO2-rGO nanocomposite exhibited excellent performance in the non-enzymatic electrochemical detection of glucose molecules. The use of LAL-induced reactive NPs for in situ GO reduction is also expected to be a universal and environmentally friendly approach for the formation of various rGO-based nanocomposites.

Sensitive detection of gallic acid based on polyethyleneimine-functionalized graphene modified glassy carbon electrode

A new electrochemical sensor was developed based on polyethyleneimine-functionalized graphene oxide (PEI-rGO) modified glassy carbon electrode (PEI-rGO/GCE). The synthetic positive charged PEI-rGO had good electron transfer ability, large specific surface area, prominent biocompatibility, and excellent adsorption. Its morphology and microstructure was characterized by scanning electron microscopy. The new electrode was firstly used for the detection of gallic acid, which exhibits superior performance in comparison to the bare glassy carbon electrode and graphene oxide modified glassy carbon electrode. The experimental conditions such as pH, adsorption time, and scan rate were optimized for the determination of gallic acid. Under optimum conditions, the linear regression equation of gallic acid was ip=12.76c−11.44 (ip: μA, c: mg/L, R=0.9887) from 0.1 to 10mg/L with a detection limit (S/N=3) of 0.07mg/L. The method has been successfully applied to the determination of gallic acid in samples of green tea and black tea.

Label-free immunosensor for the detection of kanamycin using Ag@Fe3O4 nanoparticles and thionine mixed graphene sheet

A highly sensitive label-free immunosensor for the detection of kanamycin had been developed using silver hybridized mesoporous ferroferric oxide nanoparticles (Ag@Fe3O4 NPs) and thionine mixed graphene sheet (TH-GS). TH was used as an electron transfer mediator. The electrical signal was greatly improved in the presence of GS due to its good electron-transfer ability. With the advantages of large specific surface area and excellent electrical conductivity, Ag@Fe3O4 NPs could immobilize more antibodies of kanamycin and promote the electron transfer. Cyclic voltammetry and square wave voltammetry were used to characterize the recognition of kanamycin. The proposed immunosensor showed good performances such as low detection limit (15pgmL−1), wide linear range (from 0.050 to 16ngmL−1), short analysis time (3min), high stability, and good selectivity in the detection of kanamycin. The immunosensor was evaluated for pork meat sample, receiving satisfactory results.

Label-free electrochemical immunosensors for the detection of zeranol using graphene sheets and nickel hexacyanoferrate nanocomposites

In this study, a novel label-free electrochemical immunosensor has been developed by immobilizing graphene sheets (GS) and nickel hexacyanoferrate nanocomposites (NiNPs) for the detection of zeranol (ZER). NiNPs were used as electron transfer mediators, and electroactivity was greatly enhanced in the presence of GS, which was ascribed to the good electron-transfer ability of GS. The modification procedure was characterized by cyclic voltammetry (CV). The detection is based on the current change of the modified electrode before and after the antigen–antibody reaction. Under optimum conditions, the detection of ZER demonstrated that the immunosensor exhibited a wide linear range of 0.05–10.0 ng mL−1 with a low detection limit of 6 pg mL−1. The proposed immunosensor also showed good performances such as high sensitivity, good selectivity and stability. The reliability of the developed immunosensor has been proved by the detection of ZER in river water samples with satisfactory results.

Ultrasensitive detection of kanamycin in animal derived foods by label-free electrochemical immunosensor.

A label-free amperometric immunosensor based on graphene sheet(GS)-nafion(Nf)/thionine(TH)/Pt nanoparticles modified electrode is proposed for the ultrasensitive detection of kanamycin. The anti-kanamycin antibody was immobilised onto the GS-Nf/TH/Pt modified glassy carbon electrode (GCE) through electrostatic adsorption. TH was selected as an electron transfer mediator, and the synergistic effects among GS, TH and Pt were investigated. The electroactivity of TH was greatly improved in the presence of GS and Pt due to their good electron-transfer ability. The proposed immunosensor shows good performance such as low detection limit (5.74 pg/mL), wide linear range (from 0.01 to 12.0 ng/mL), high stability, and good selectivity in the detection of kanamycin. The reliability of the developed immunosensor was proved by determination of kanamycin in animal derived foods with satisfactory results.

An electrochemical amperometric immunobiosensor for label-free detection of α-fetoprotein based on amine-functionalized graphene and gold nanoparticles modified carbon ionic liquid electrode

A sensitive label-free amperometric immunosensor was developed based on the amine-functionalized graphene (GR-NH 2) and gold nanoparticles (AuNPs) composite modified carbon ionic liquid electrode (CILE). CILE was fabricated by using an ionic liquid of 1-octyl-3-methylimidazolium hexafluorophosphate as binder. The nanocomposite AuNPs/GR-NH 2 had prominent biocompatibility, good electron transfer ability, large specific surface area, and primarily excellent adsorption. The negatively charged AuNPs could be adsorbed on the positively charged GR-NH 2 modified CILE surface by electrostatic adsorption, and then to immobilize α-fetoprotein antibody (anti-AFP) for the assay of α-fetoprotein (AFP). The fabricated procedures and electrochemical behaviors of the immunosensor were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The anti-AFP/AuNPs/GR-NH 2 modified CILE was sensitive to AFP in linear relation between 1 and 250 ng mL −1 with the correlation coefficient of 0.995, and the detection limit ( S/ N = 3) was 0.1 ng mL −1 under the optimal conditions. In addition, the proposed immunosensor exhibited good sensitivity, selectivity, stability and long-term maintenance of bioactivity and it may be used to immobilize other biomoleculars to develop biosensor for the detection of other antigens or biocompounds.

Synthesis, optical and electrochemical properties of novel hole-blocking poly(biphenylene-1,3,4-oxadiazole) containing electron-withdrawing trifluoromethyl groups

New poly(biphenylene-1,3,4-oxadiazole) P1 and poly(biphenylene hydrazide) P2 containing electron-withdrawing trifluoromethyl group at the 2 and 2′ positions of biphenyl moiety were synthesized. The biphenyl is forced to adapt a non-coplanar conformation due to the bulky trifluoromethyl group. High quality polymer P1 thin film can be easily obtained by thermal cyclodehydration from its soluble polyhydrazide precursor P2. The polymer P1 exhibited good thermal stability with glass transition temperature of 234 °C and 5% decomposition temperature of 469 °C. The optical and electrochemical properties were investigated by UV–vis spectroscopy, photoluminescence spectroscopy and cyclic voltammetry. For polymer P1 film, two absorption peaks at 370 and 414 nm were observed. It also exhibited a photoluminescent peak at 555 nm when excited by 414 nm light. The cyclic voltammetric studies revealed that polymer P1 had extremely low HOMO (−6.85 eV) and LUMO (−3.71 eV) energy levels due to the presence of strong electron-withdrawing trifluoromethyl group. It also exhibited a large energy gap (3.14 eV) which is an indication of short conjugation length resulted from non-coplanar biphenyl structure. Its HOMO energy was even lower than that of widely used hole-blocking material, 2-(4-biphenyl)-5-(4- tert-butylphenyl)-1,3,4-oxadiazole PBD (−6.30 eV). The low LUMO energy of polymer P1 could allow the easier electron injection from air-stable cathode such as aluminum. The good electron transfer ability was also shown by measuring the current density of electron-only devices with the structures of Al/ P1 (150 nm)/Alq 3 (50 nm)/Al and Al/Alq 3 (200 nm)/Al. Combined with high thermal stability and amorphous morphology, polymer P1 would be a promising candidate as the hole-blocking material for organic light-emitting diodes.

Fabrication of Fe(CN)63− Functionalized PDDA/CdTe Layer‐by‐layer Film with Good Electron Transfer Ability

Abstract(PDDA/CdTe)n layer‐by‐layer (LBL) film immobilized with Fe(CN)63− was fabricated on the gold electrode. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to investigate the electrochemical properties of this film. The peak current of the immobilized Fe(CN)63− increased as the number of the bilayers increased and was proportional to the scan rate. Compared with pure (PDDA/CdTe)n and (PDDA/PSS)n LBL film, Fe(CN)63− immobilized (PDDA/CdTe)n LBL film had good electron transfer ability. The immobility of Fe(CN)63− into the film was attributed to its interaction with Cd2+ on the surface of CdTe QDs. Fe(CN)63− also can interact with other metal ions, which would make Fe(CN)63− release from the film. The concentrations of metal ions will affect the CV response of Fe(CN)63− immobilized LBL film. It has provided a novel prototype of device or sensor for quantitative detection of metal ions.