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1.
Chem Rec ; 24(1): e202300105, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37222655

RESUMO

Polyaniline (PANI) has piqued the interest of nanotechnology researchers due to its potential as an electrode material for supercapacitors. Despite its ease of synthesis and ability to be doped with a wide range of materials, PANI's poor mechanical properties have limited its use in practical applications. To address this issue, researchers investigated using PANI composites with materials with highly specific surface areas, active sites, porous architectures, and high conductivity. The resulting composite materials have improved energy storage performance, making them promising electrode materials for supercapacitors. Here, we provide an overview of recent developments in PANI-based supercapacitors, focusing on using electrochemically active carbon and redox-active materials as composites. We discuss challenges and opportunities of synthesizing PANI-based composites for supercapacitor applications. Furthermore, we provide theoretical insights into the electrical properties of PANI composites and their potential as active electrode materials. The need for this review stems from the growing interest in PANI-based composites to improve supercapacitor performance. By examining recent progress in this field, we provide a comprehensive overview of the current state-of-the-art and potential of PANI-based composites for supercapacitor applications. This review adds value by highlighting challenges and opportunities associated with synthesizing and utilizing PANI-based composites, thereby guiding future research directions.

2.
Anal Chem ; 95(5): 2698-2705, 2023 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-36710448

RESUMO

Sensitive, portable methods of detection for foodborne pathogens hold great significance for the early warning and prevention of foodborne diseases and environmental pollution. Restricted by a complicated matrix and limited signaling strategies, developing a ready-to-use sensing platform with ultrahigh sensitivity remains challenging. In this work, near-infrared (NIR) light-responsive AgBiS2 nanoflowers (NFs) and Cu2O nanocubes (NCs) were introduced to construct a novel target-induced photocurrent-polarity-switchable system and verified for the development of an all-in-one, ready-to-use photoelectrochemical (PEC) immunosensor. NIR-responsive n-type AgBiS2 NFs and p-type Cu2O NCs producing anodic and cathodic photocurrents were conjugated with monoclonal (MAb1) and polyclonal antibodies (PAb2), respectively. Using a sandwich-type immunocomplex bridged by Escherichia coli O157:H7, an efficient photocurrent-polarity-switching PEC system was formed on a paper-based working electrode (PWE). Owing to the spatial separation of the photogenerated carriers and the elimination of false-positive/negative signals by the polarity-switchable photocurrent, the proposed NIR PEC immunoassay for E. coli O157:H7 exhibits a considerably low detection limit of 8 colony-forming units/milliliter (CFU/mL) with a linear range from 25 to 5 × 107 CFU/mL. The platform includes a PWE with an automatic cleaning function and a portable PEC analyzer with smartphone-compatible Bluetooth capability, thus achieving point-of-care testing of E. coli O157:H7. The sensor was applied to the analysis of pork samples artificially contaminated with E. coli O157:H7, and the detection results were in good agreement with the plate counting method, a gold standard in the field. This work aimed to investigate the photoelectric activity of the NIR-responsive p/n-type composites and to provide a new signal-reversal route for the construction of an all-in-one ready-to-use PEC immunosensor for the detection of low-concentration biomolecules.


Assuntos
Técnicas Biossensoriais , Escherichia coli O157 , Doenças Transmitidas por Alimentos , Humanos , Imunoensaio/métodos , Técnicas Biossensoriais/métodos , Anticorpos
3.
Chem Rec ; 21(1): 204-238, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33200874

RESUMO

Due to their potential applications in industry and potent toxicity to the environment, sulfides and their detection have attracted the attention of researchers. To date, a large number of controlled-potential techniques for electrochemical sulfide sensors have been developed, thanks to their simplicity, reasonable limit of detection (LOD), and good selectivity. Different researchers have applied different strategies for developing selective and sensitive sulfide sensors. However, there has been no systematic review on controlled-potential techniques for sulfide sensing. In light of this absence, the main aim of this review article is to summarize various strategies for detecting sulfide in different media. The efficiencies of the developed sulfide sensors for detecting sulfide in its various forms are determined, and the essential parameters, including sensing strategies, working electrodes, detection media, pH, LOD, sensitivity, and linear detection range, are emphasized in particular. Future research in this area is also recommended. It is expected that this review will act as a basis for further research on the fabrication of sulfide sensors for practical applications.

4.
Food Chem ; 442: 138389, 2024 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-38219569

RESUMO

In this study, a cascade nanobioreactor was developed for the highly sensitive detection of methyl parathion (MP) in food samples. The simultaneous encapsulation of acetylcholinesterase (AChE) and choline oxidase (CHO) in a zeolitic imidazole ester backbone (ZIF-8) effectively improved the stability and cascade catalytic efficiency of the enzymes. In addition, glutathione-stabilized gold nanoclusters (GSH-AuNCs) were encapsulated in ZIF-8 by ligand self-assembly, conferring excellent fluorescence properties. Acetylcholine (ATCh) is catalyzed by a cascade of AChE/CHO@ZIF-8 as well as Fe(II) to generate hydroxyl radicals (·OH) with strong oxidizing properties. The ·OH radicals then oxidize Au(0) in GSH-AuNCs@ZIF-8 to Au(I), resulting in fluorescence quenching. MP, as an inhibitor of AChE, hinders the cascade reaction and thus restores the fluorescence emission, enabling its quantitative detection. The limit of detection of the constructed nanobioreactor for MP was 0.23 µg/L. This MOF-based cascade nanobioreactor has great potential for the detection of trace hazards.


Assuntos
Nanopartículas Metálicas , Estruturas Metalorgânicas , Metil Paration , Acetilcolinesterase , Acetilcolina , Ouro , Limite de Detecção
5.
J Agric Food Chem ; 71(31): 12052-12060, 2023 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-37498892

RESUMO

To prevent the contamination of cereals by mycotoxins, establishing a sensitive and rapid method for the detection of mycotoxins is essential. In this study, a screening-capture-integrated electrochemiluminescence (ECL) aptasensor based on mesoporous silica films (MSFs) was successfully prepared for the ultrasensitive and highly selective detection of deoxynivalenol (DON) in wheat. The narrow nanochannels of MSFs can realize size screening, thereby eliminating the influence of macromolecular substances and providing a pure environment for the signal probe (tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)32+)) to reach the indium tin oxide (ITO) conductive substrate, which significantly improves the anti-interference ability of the screening-capture-integrated ECL sensor. The aptamer (Apt) attached to the surface of the MSFs can specifically capture DON, and the resulting DON-Apt complex has a gated effect on the MSFs, triggering the inhibition of Ru(bpy)32+ in the electrolyte from reaching the ITO surface. Therefore, the ECL intensity of the sensor decreased with increasing DON concentration to achieve a quantitative detection of DON. Under optimized conditions, the linear range of the screening-capture-integrated ECL aptasensor was 0.001-200 µg/kg, and the detection limit was as low as 5.27 × 10-5 µg/kg (S/N = 3). In conclusion, this study developed a screening-capture-integrated ECL aptasensor that combines size screening and specific capture for the detection of DON in wheat, providing a new approach for the early detection of wheat mildew.


Assuntos
Técnicas Biossensoriais , Micotoxinas , Dióxido de Silício/química , Triticum , Técnicas Biossensoriais/métodos , Medições Luminescentes/métodos , Técnicas Eletroquímicas/métodos
6.
Food Chem ; 418: 136012, 2023 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-36996649

RESUMO

This study reports the development of a Tb-metal-organic framework (Tb-MOF)-based fluorescent platform for the detection of propyl gallate (PG). The Tb-MOF using 5-boronoisophthalic acid (5-bop) as the ligand exhibited multiple emissions at 490, 543, 585, and 622 nm under an excitation wavelength of 256 nm. The fluorescence of Tb-MOF was selectively and significantly weakened in the presence of PG due to the special nucleophilic reaction between the boric acid of Tb-MOF and o-diphenol hydroxyl of PG, and the combined effect of static quenching and internal filtering. Furthermore, this sensor enabled the determination of PG within seconds in a wide linear range of 1-150 µg/mL, and with a low detection limit of 0.098 µg/mL, and high specificity against other phenolic antioxidants. This work provided a new route for the sensitive and selective determination of PG in soybean oil, thus was perspective to monitor and reduce the risk of PG overuse.


Assuntos
Estruturas Metalorgânicas , Galato de Propila , Limite de Detecção , Corantes Fluorescentes , Óleos
7.
Chem Asian J ; : e202300780, 2023 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-37811920

RESUMO

The increasing global energy demand, which is being driven by population growth and urbanization, necessitates the exploration of sustainable energy sources. While traditional energy generation predominantly relies on fossil fuels, it also contributes to alarming CO2 emissions. Hydrogen has emerged as a promising alternative energy carrier with its zero-carbon emission profile. However, effective hydrogen storage remains a challenge. When exposed to hydrogen, conventional metallic vessels, once considered to be the primary hydrogen carriers, are prone to brittleness-induced cracking. This has spurred interest in alternative storage solutions, particularly porous materials like metal-organic frameworks and activated carbon (AC). Among these, biomass-derived AC stands out for its eco-friendly nature, cost-effectiveness, and optimal adsorption properties. This review offers a comprehensive overview of recent advancements in the synthesis, characterization, and hydrogen storage capabilities of AC. The unique benefits of biomass-derived sources are highlighted, as is the pivotal role of chemical and physical activation processes. Furthermore, we identify existing challenges and propose future research directions in AC-based hydrogen storage. This compilation aims to serve as a foundation for potential innovations in sustainable hydrogen storage solutions.

8.
Sensors (Basel) ; 12(8): 10309-25, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-23112601

RESUMO

The effect of morphology on the plasmonic sensing of the presence of formaldehyde in water by gold nanostructures has been investigated. The gold nanostructures with two different morphologies, namely spherical and rod, were prepared using a seed-mediated method. In typical results, it was found that the plasmonic properties of gold nanostructures were very sensitive to the presence of formaldehyde in their surrounding medium by showing the change in both the plasmonic peaks position and the intensity. Spherical nanoparticles (GNS), for example, indicated an increase in the sensitivity when the size was increased from 25 to 35 nm and dramatically decreased when the size was further increased. An m value, the ratio between plasmonic peak shift and refractive index change, as high as 36.5 nm/RIU (refractive index unit) was obtained so far. An expanded sensing mode to FD was obtained when gold nanostructures with nanorods morphology (GNR) were used because of the presence of two plasmonic modes for response probing. However, in the present study, effective plasmonic peak shift was not observed due to the intense plasmonic coupling of closely packed nanorod structures on the surface. Nevertheless, the present results at least provide a potential strategy for response enhancement via shape-effects. High performance plasmonic sensors could be obtained if controlled arrays of nanorods can be prepared on the surface.


Assuntos
Formaldeído/análise , Ouro/química , Nanopartículas Metálicas/química , Ressonância de Plasmônio de Superfície/instrumentação , Água/química , Formaldeído/química , Nanotubos , Tamanho da Partícula , Ressonância de Plasmônio de Superfície/métodos
9.
ACS Omega ; 7(18): 16116-16126, 2022 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-35571801

RESUMO

Screen-printed graphene electrodes (SPGEs) have become a potential option in electrochemical applications because of their outstanding properties and disposable approach to miniaturize the electrodes for onsite analysis. Herein, the detection of para-hydroxybenzoic acid (PHBA) in cosmetics using the anodized SPGE has been pioneered and reported. The simple anodization of the SPGE surface was operated by anodic pretreatment at a constant potential on SPGE. The surface morphologies and electrochemical behaviors of anodized SPGEs in different anodization electrolytes were examined. Using anodized SPGE in a phosphate-buffered solution, a nontoxic solution, the sensitivity of PHBA detection was significantly improved compared with pristine SPGE owing to the increase of the polar oxygen-containing functional group during the anodization. The anodized SPGE could detect a PHBA down to 0.073 µmol/L. Finally, the developed anodized SPGE presented high ability and feasibility for PHBA detection in cosmetics. Furthermore, a facile electrode preparation step with a nontoxic solution can present high reproducibility and compatibility with a portable potentiostat for onsite PHBA detection during manufacturing.

10.
Food Chem ; 381: 132276, 2022 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-35121311

RESUMO

In this work, a novel and credible electrochemiluminescence immunoassay (ECLIA) was constructed for the ultrasensitive and highly selective detection of aflatoxin B1 (AFB1). Amino-functionalized 3D graphene hydrogel (NGH) served as the ECL platform with the self-enhanced ECL of luminol-palladium-graphene oxide (lum-Pd-GO) acting as a marker for the antibodies against AFB1. Pd-GO was synthesized by a self-redox method; it promotes the formation of reactive oxygen species, which are important to the ECL of luminol, from dissolved oxygen. The π-π conjunction between luminol and GO shortens their electron transfer distance, resulting in an amplified ECL signal (∼8.5 times larger than conventional luminol ECL). Moreover, 3D NGH, with its good conductivity, large surface area, and sufficient amino groups, was used to anchor gold nanoparticles (AuNPs), which subsequently immobilized bovine serum albumin (BSA)-AFB1 through Au-S bonds. The resultant, competitive ECLIA gave a relative low detection limit of 5 × 10-3 µg kg-1 and exhibited a broad linear relationship over the range of 0.05-50 µg kg-1. Finally, the proposed ECLIA was successfully used to analyze AFB1 contents in food samples. ECLIA: electrochemiluminescence immunoassay; AFs: Aflatoxins; HPLC: high-performance liquid chromatography.


Assuntos
Técnicas Biossensoriais , Grafite , Substâncias Luminescentes , Nanopartículas Metálicas , Aflatoxina B1 , Técnicas Biossensoriais/métodos , Técnicas Eletroquímicas/métodos , Ouro/química , Grafite/química , Limite de Detecção , Substâncias Luminescentes/química , Medições Luminescentes/métodos , Luminol/química , Nanopartículas Metálicas/química , Paládio/química
11.
Food Chem ; 385: 132710, 2022 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-35313194

RESUMO

The peroxide value (PV) is an important indicator to assess quality of edible oils. However, traditional methods for determining PV are complicated for operating and lack sensitivity. In this paper, we report a fast, reusable, selective and sensitive room-temperature phosphorescence (RTP)-based sensor to determine the PV of edible oils. The sensor comprises a lead-based metal-organic framework (Pb-MOF, Pb4O(TPA)3, TPA: (terephthalic acid). Luminescence studies reveal that bright RTP of Pb-MOF quenched significantly by iodide ions (I-), a classic reductant for peroxides in edible oils, thus the determination of the PV is possible. Crucially, the proposed method yields responses within 10 min and has a wide linear range of 0.35-25.62 mmol/kg, a low detection limit of 30 µmol/kg, and high selectivity for PV detection. The sensing system was successfully applied to determine the PVs of edible oils and monitor the PV of rapeseed oil during storage.


Assuntos
Estruturas Metalorgânicas , Peróxidos , Chumbo , Óleos de Plantas , Temperatura
12.
Food Chem ; 368: 130856, 2022 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-34425333

RESUMO

In this work, we present a novel dual-emissive fluoroimmunoassay for synchronous monitoring of okadaic acid (OA) and saxitoxin (STX) using multicolor fluorescent labels composed of sulfur, phosphorous co-doped graphene quantum dots (S, P-GQDs), and ovalbumin (OVA)-coated gold nanoparticles (OVA-AuNPs). The novel OVA-AuNPs were prepared by the reduction of chloroauric acid under alkaline conditions using OVA as a reducing agent. Both S, P-GQDs and OVA-AuNPs exhibit bright fluorescence, more importantly, a large emission wavelength difference (Δλ = 156 nm) under an excitation of 400 nm and relatively independent fluorescence behavior, which are essential to realizing the dual-signal marks in a directly mixing system. Using a competitive fluorescence-linked immunosorbent assay (cFLISA) format, the dual-emissive cFLISA was successfully utilized to measure OA and STX contents in Alectryonella plicatula (commonly named as fingerprint oyster) and the detection results were in good agreement with the commercial enzyme-linked immunosorbent assay (ELISA) kits.


Assuntos
Grafite , Nanopartículas Metálicas , Pontos Quânticos , Ouro , Imunoensaio , Ácido Okadáico , Saxitoxina , Frutos do Mar/análise
13.
ACS Appl Mater Interfaces ; 14(36): 41649-41658, 2022 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-36059104

RESUMO

The photoelectric response is crucial for photocatalysis, having applications in solar cells and photoelectrochemical (PEC) sensors. In this study, we demonstrate improvements in the near-infrared (NIR)-light-driven PEC response via synergism between reduced graphene oxide (rGO) and MoS2. Intriguingly, rGO modulates the morphology of MoS2, facilitating carrier generation and migration, improving the PEC performance of the resultant rGO-MoS2 sheets (GMS), and yielding an approximately 8-fold increase in the photocurrent compared to that of the pure MoS2. Based on these findings, a NIR-responsive PEC immunosensing platform for the "turn-on" analysis of Escherichia coli O157:H7 on 980 nm light irradiation is reported. Specifically, the device is a three-dimensional magnetic screen-printed paper-based electrode assembled on a home-made PEC cell, and it enables integrated separation and detection. Using a sandwich-type immunocomplex bridged by E. coli O157:H7 and a GMS PEC probe, the immunosensing platform detected E. coli O157:H7 between 5.0 and 5.0 × 106 CFU mL-1, having an extremely low detection limit of 2.0 CFU mL-1. Further, the assay enables the direct analysis of E. coli O157:H7 in milk without the need for pretreatment. Our findings suggest directions for the development of NIR-responsive paper-based PEC materials for portable biomolecule sensing.


Assuntos
Técnicas Biossensoriais , Escherichia coli O157 , Técnicas Biossensoriais/métodos , Ouro/química , Grafite , Molibdênio
14.
J Nanosci Nanotechnol ; 11(6): 4974-80, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21770130

RESUMO

We found that the gold nanoparticles with high-density and crystalline-shape, such as nanocubes, nanobricks, pentahedral nanorods, etc., can be realized on the surface by using a seed-mediated growth method with a unique seeding process, namely alcohothermal. By using a conventional growth solution that contains HAuCl4, cetyltrimethylammonium bromide, NaOH and ascorbic acid, gold nanoparticles with crystalline-morphology (gold nanocrystals) of yield up to ca. 95%, can be prepared. An alcohothermal seeding was carried out by a thermal reduction of gold ions from an alcoholic solution of gold salt on the surface through an annealing process at a moderate temperature, namely 250 degrees C. It is believed that the unique initial characteristic (presumably the structures) of the gold nanoseeds particles as the result of peculiar nanoseeds formation process, prepared using this approach, instead of a simple thermal restructuring of the as prepared nanoseeds as confirmed by the results of annealing treatment on the nanoseed prepared using the normal and in-situ reduction seeding, was as the driving factor for the projected growth of crystalline-shape gold nanoparticles on the surface. The crystalline-shape gold nanoparticles modified-surface should find a potential application in catalysis, sensors and SERS.

15.
ACS Omega ; 6(28): 18395-18403, 2021 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-34308070

RESUMO

Codeposition of Pt and Au on Ni wire was performed using a simple treatment of immersing Ni wire in aqueous solutions containing both K2PtCl4 and HAuCl4. For evaluating the electrochemical properties of the thus-prepared electrodes, cyclic voltammograms (CVs) of 1.0 M ethanol in 1.0 M NaOH aqueous solutions were recorded. Compared with Pt- or Au-deposited Ni wire electrodes prepared by treating Ni wire in aqueous solutions of a single component, e.g., 1.0 mM K2PtCl4 or 1.0 mM HAuCl4, a noteworthy increase in the electrocatalytic current was observed for the oxidation of ethanol with a PtAu-codeposited Ni (PtAu/Ni) wire electrode even when it was prepared in an aqueous solution containing both 0.10 mM K2PtCl4 and 0.10 mM HAuCl4. In addition, the shape and the peak potentials of CVs recorded using PtAu/Ni wire electrodes were found to be different from those recorded with the Pt- or Au-deposited Ni wire electrodes. Because the CV responses typical of the PtAu/Ni wire electrodes were observed even when a PtAu/Ni wire electrode was prepared in an aqueous solution containing both 0.010 mM K2PtCl4 and 1.0 mM HAuCl4, it is considered that a small amount of Pt was effectively modified or incorporated and affected the electrochemical properties significantly. The CV results for ethanol oxidation were compared with those for the electrocatalytic oxidations of methanol, 1-propanol, and 2-propanol. Besides, the CV results recorded with the present PtAu/Ni wire electrodes are discussed in comparison with some previous results obtained using other PtAu nanoelectrocatalysts.

16.
Chem Asian J ; 16(12): 1570-1583, 2021 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-33894052

RESUMO

There is an overwhelming desire to develop new sulfide oxidation electrocatalysts that perform at low potentials and exhibit high current density for the removal and efficient sensing of sulfide. This article describes a comparative electrochemical analysis of various commercially available carbon materials and polymer/surfactant composite electrocatalysts for direct electrooxidation of sulfide in an aqueous solution. The composites were prepared from five different carbon materials multiwalled carbon nanotubes, fullerene-C60 , graphene, glassy carbon, and carbon nanofibers (CNF) and four different polymers: chitosan, polyvinylidene fluoride, Nafion, and indigenously synthesized poly[2-(methacryloyloxy)ethyl] trimethylammonium chloride (PMTC). The carbon@polymer composites were prepared by a simple ultrasonication technique, and the electrodes were prepared by drop-drying the prepared composite on indium tin oxide (ITO) substrates. The CNF@PMTC showed the highest positive zeta potential that allowed an accumulation of many negatively charged sulfide ions at the CNF@PMTC surface. Cyclic voltammetry was used for the electrooxidation of sulfide in an aqueous solution of tris buffer (0.05 M; pH 8.0) and KNO3 (0.1 M). The lowest sulfide oxidation peak potential (i. e., -51 mV vs. standard hydrogen electrode) with a high catalytic current response (730 µA/cm2 ) of the CNF@PMTC-modified ITO electrode among the tested and previously reported carbon-based electrode materials make it ideal for direct sulfide electrooxidation. Taking this and its simple preparation method into account, CNF@PMTC can be considered a benchmark carbon-based electrocatalyst for sulfide oxidation.

17.
Phys Chem Chem Phys ; 12(3): 604-13, 2010 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-20066346

RESUMO

The electron transfer dynamics and electrocatalytic behaviour of ferrocene-terminated self-assembled monolayers (SAMs), co-adsorbed with single-walled carbon nanotubes (SWCNTs) on a gold electrode, have been interrogated for the first time. Ferrocene monocarboxylic acid (FMCA) or ferrocene dicarboxylic acid (FDCA) was covalently attached to the cysteamine (Cys) monolayer to form Au-Cys-FMCA and Au-Cys-FDCA, respectively. The same covalent attachment strategy was used to form the mixed SWCNTs and ferrocene-terminated layers (i.e. Au-Cys-SWCNT/FMCA and Au-Cys-SWCNT/FDCA). Using cyclic voltammetry and electrochemical impedance spectroscopy, the impact of neighbouring SWCNTs on the electron transfer dynamics of the ferrocene molecular assemblies in an acidic medium (0.5 M H(2)SO(4)) and in a solution of an outer-sphere redox probe ([Fe(CN)(6)](4-)/[Fe(CN)(6)](3-)) was explored. The electron transfer rate constants in both media essentially decreased as Au-Cys-FMCA > Au-Cys-SWCNT/FDCA > Au-Cys-FDCA > Au-Cys-SWCNT/FMCA. This trend has been interpreted in terms of several factors such as the locations of the ferrocene species in a range of environments with a range of potentials, the proximity/interactions of the ferrocenes with one another, and electrostatic interaction or repulsion existing between the negatively-charged redox probe and the modified electrodes. The thiocyanate ion (SCN(-)) was used as a model analyte to examine the influence of the neighbouring SWCNTs on the electrocatalytic ability of the ferrocene assemblies. The Au-Cys-SWCNT/FDCA showed the best catalytic activity (in terms of onset potential and catalytic peak current height) for the oxidation of SCN(-), possibly due to the repulsive interactions between the negatively charged SCN(-) and high number of surface -COOH species at the SWCNT/FDCA. This study has provided some useful insights as to how CNTs co-assembled with ferrocene-terminated thiols could impact on the electron transfer kinetics as well as the electrocatalytic detection of the self-assembled ferrocene layers.

18.
Anal Chem ; 81(2): 830-3, 2009 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-19067540

RESUMO

A colorimetric electrochemiluminescence (ECL) sensor was fabricated for the first time, based on a dual-color system including a strong red Ru(bpy)(3)(2+) ECL and a green reference light from a light emitting diode. Traditional ECL intensity information can be easily transformed into a color variation with this sensor, and the color variation can be directly monitored using the naked eye or a commercial CCD camera. The sensor has been successfully used to determine the concentration of tripropylamine, proline (enhancing system), and dopamine (quenching system). The results indicated that the color variation obtained corresponded to the concentration of target analytes. This sensor has potential application in rapid and semiquantitative ECL analysis.

19.
J Nanosci Nanotechnol ; 9(4): 2413-20, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19437984

RESUMO

Electrochemiluminescence (ECL) behavior of luminol on an indium tin oxide (ITO) electrode modified with platinum nanoparticles (PtNPs) was investigated in a neutral aqueous solution using the conventional cyclic voltammetry (CV) technique. Experimental results indicated that the ECL behaviors of luminol on the PtNPs modified electrode showed significant difference from those on the bare ITO or bulk platinum electrodes. Five ECL peaks were found at 0.60, 0.92, 0.70, -0.44 and -1.16 V versus a saturated calomel electrode (SCE), respectively. The ECL peaks were found to depend on the reaction medium conditions including the type of electrolyte, pH value, the presence or absence of O2 and the different kinds of nanoparticles, as well as the scan direction and range of the applied potential. Furthermore, ECL peaks at -0.44 and -1.16 V could only be obtained on the PtNPs/ITO electrode. The surface state of the electrode was characterized by ultraviolet-visible (UV-Vis) absorption, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). A mechanism for luminol ECL on the PtNPs/ITO electrode was proposed. The excellent ECL properties of luminol on the PtNPs/ITO electrode in the neutral medium revealed a great potential for analytical applications to biological samples.


Assuntos
Eletroquímica , Luminescência , Luminol/química , Nanopartículas Metálicas/química , Platina/química , Compostos de Estanho/química , Eletrodos , Eletrólitos/química , Concentração de Íons de Hidrogênio , Nanopartículas Metálicas/ultraestrutura , Nitrogênio/química , Oxigênio/química , Propriedades de Superfície , Água/química
20.
ACS Omega ; 3(9): 11526-11536, 2018 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31459253

RESUMO

A combinative effect of two or more individual material properties, such as lattice parameters and chemical properties, has been well-known to generate novel nanomaterials with special crystal growth behavior and physico-chemical performance. This paper reports unusually high catalytic performance of AgPt nanoferns in the hydrogenation reaction of acetone conversion to isopropanol, which is several orders higher compared to the performance shown by pristine Pt nanocatalysts or other metals and metal-metal oxide hybrid catalyst systems. It has been demonstrated that the combinative effect during the bimetallisation of Ag and Pt produced nanostructures with a highly anisotropic morphology, i.e., hierarchical nanofern structures, which provide high-density active sites on the catalyst surface for an efficient catalytic reaction. The extent of the effect of structural growth on the catalytic performance of hierarchical AgPt nanoferns is discussed.

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