Showing papers by "Abdollah Salimi published in 2017"

Development of a New Label-free, Indicator-free Strategy toward Ultrasensitive Electrochemical DNA Biosensing Based on Fe3O4 Nanoparticles/Reduced Graphene Oxide Composite

Abstract: Electrochemistry offers sensitivity, selectivity and low cost for fabrication of sensors capable of detection of selected DNA targets or mutated genes associated with human disease. In this work, we have developed a novel label-free, indicator-free strategy of electrochemical DNA sensor based on Fe3O4 nanoparticles/reduced graphene oxide (Fe3O4/r-GO) nanocomposite modified electrode. By using Fe3O4/r-GO nanocomposite as a substrate to immobilize probe DNA and subsequent hybridization with target sequence to form dsDNA, a great signal amplification was achieved through measuring changes in DPV peak current of underlying Fe(II)/Fe(III) redox system. With the remarkable attomolar sensitivity and high specificity and at the same time, great simplicity, the proposed strategy may find great applications in different DNA assay fields.

Potential-resolved electrochemiluminescence immunoassay for simultaneous determination of CEA and AFP tumor markers using dendritic nanoclusters and Fe3O4@SiO2 nanoparticles

Abstract: A potential-resolved electrochemiluminescence (ECL) immunoassay is presented for the simultaneous determination of the tumor markers alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA). It is making use of polyamidoamine dendrimer - quantum dots (PAMAM–QDs) and PAMAM-luminol as the signal probes and Fe3O4-SiO2 as a magnetic bead. The QDs of type CdTe@CdS and luminol in the presence of H2O2 generate ECL at an applied voltage of −1.12 V and +0.6 V (vs Ag/AgCl), respectively. The sensitivity of the method can be enhanced by using PAMAM dendrimers as a carrier for immobilizing the QDs. The assay is performed in a sandwich format, and AFP and CEA can be quantified via potential cycling from +0.6 to −1.4 V. Both tumor markers can be detected by this method in the 0.25 fg.mL−1 to 20 pg.mL−1 concentration range with a detection limit as low as 0.10 fg.mL−1. The assay was applied to the determination of both AFP and CEA in (spiked) human serum samples, and the results were found to be in acceptable agreement with the those obtained with an ELISA.

Hemin/G-Quadruplex Horseradish Peroxidase-Mimicking DNAzyme: Principle and Biosensing Application.

Abstract: Enzymes are macromolecular biological catalysts that accelerate chemical reactions. Enzyme labels are commonly used to obtain signal amplification in sensors and biosensors on the basis of reactions of some enzymes such as horseradish peroxidase (HRP). However, use of natural enzymes can encounter some challenges. Lately, nucleic acids that exhibit catalytic properties have attracted growing interest because they have certain advantages in comparison with traditional protein enzymes. DNAzymes are DNA-based catalysts, representing an important class of functional DNA, which have been widely used because of their excellent activity, programmability, signal amplification through catalytic turnover, high chemical stability, simple synthesis, and easy modification. Considering these remarkable properties, the hemin/G-quadruplex DNAzyme is extensively used in electrochemical, colorimetric, and chemiluminescence sensors and biosensors for detection of various targets.

Sulfur doped-copper oxide nanoclusters synthesized through a facile electroplating process assisted by thiourea for selective photoelectrocatalytic reduction of CO 2 .

Abstract: Development of effective methods for conversion of CO 2 to useful chemicals is considered to be a prospective way in terms of energy economy and chemical industry. Due to the thermodynamic stability of CO 2 , the application of the low-cost eco-friendly catalyst or photocatalyts for CO 2 reduction with high efficiency is a challenge. Herein, we report a simple template-free electrochemical approach for the preparation of sulfur doped copper oxide nanoclusters directly on the copper disc electrode using thiourea (TU) as sulfur precursor. The prepared Cu 2 O/CuO hybrid structures without TU exhibits photoelectrocatalytic fitness for CO 2 reduction, while the catalytic activity and stability are significantly improved after sulfur substitution. Surface study by scanning electron microscopy (SEM) and atomic force microscopy (AFM) reveals an improved surface roughness alongside the formation and distribution of uniform nanoclusters of sulfur-substituted copper oxide. Also, optical analyses show a little increasing of band gap from 1.95 eV to 2.05 eV after sulfur substitution. Based on the experimental results, methanol and acetone are the main CO 2 reduction products where, the overpotential of methanol and acetone evolution is in good agreement with the conduction band position of prepared nanoclusters. This work has a high competitive advantage of new sight to develop the novel doped materials via a simple way for high-performance photoelectrocatalysts for energy conversion.

Facile Synthesis of Ultra‐wide Two Dimensional Bi2S3 Nanosheets: Characterizations, Properties and Applications in Hydrogen Peroxide Sensing and Hydrogen Storage

Abstract: The ultra-wide two dimensional Bi2S3 nanosheets (2D Bi2S3 Ns) as non-toxic graphene-like nanomaterials have been prepared through solvothermal decomposition of a single-source precursor, Bi(S2CNEt2)3, in ethylenediamine media for 2 h in 180 °C The morphology, structure, properties and catalytic activity of prepared 2D Bi2S3 Ns were characterized with XRD, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV-Visible spectroscopy, cyclic voltammetry (CV), amperometry, electrochemical charge/discharge technique and electrochemical impedance spectroscopy (EIS) The SEM image showed the 2D Bi2S3 Ns with a thickness of 15±4 nm and lengths of several micrometers is synthesized The UV−Vis spectrum of 2D Bi2S3 Ns showed high sensitivity to visible-near infrared light with its direct energy band gap of ≈122 eV These Bi2S3 Ns showed high electron transfer ability and good electrochemical behavior and also exhibited electro-catalytic activity toward the reduction-oxidation of hydrogen peroxide It is found that Bi2S3 Ns could detect H2O2 at wide linear concentration range (500 μM–80 mM) with detection limit 8 μM, using amperometry as measuring technique Also the synthesized Bi2S3 Ns exhibited excellent electrochemical H2 storage properties As a result, based on above properties, the Bi2S3 Ns can be used as a valuable and useful nanomaterial for H2 storage, high-energy batteries, electrocatalytic fields and electrochemical sensing

Effect of support on power output of ethanol/O2 biofuel cell

Abstract: Enzymatic biofuel cells have many great usages as a small power source for medical and environmental applications. In this paper, we employed carboxylated multiwall carbon nanotube- (1-ethyl-3-methylimidazolium bis (trifluoromethyl sulfonyl) imide) ionic liquid nanocomposite on two different electrodes (glassy carbon and carbon felt) for immobilizing alcohol dehydrogenase. The properties of the two types of electrodes were characterized by cyclic voltammetry analysis. Polarization analysis and field emission scanning electron microscopy were used to show differences in the nanobiocomposite immobilization on two electrodes. Compared to glassy carbon, carbon felt achieved much more gains in electrochemical activity and power by catalyst coating. Power density of 10.027μWcm−2, has been achieved by carbon felt, but glassy carbon showed 1.7 μWcm−2 respectively.