Ultra-sensitive suspended graphene nanocomposite cancer sensors with strong suppression of electrical noise
ABSTRACT The cancer sensor based on suspended layer-by-layer self-assembled graphene reported in the paper exhibits an ultra high sensitivity due to graphene material properties in nature. By simply immersing the substrate alternatively into charged graphene suspensions and polyions, graphene nanoplatelets are self-assembled in the channel as the sensing region, followed by SF(6) dry etching to suspend the structure. Conductance shift curves demonstrate that the suspended graphene sensors functionalized with specific anti-PSA antibodies as bioreceptor are capable of detecting prostate specific antigen down to 0.4 fg/ml (11 aM), at least one order of magnitude lower than unsuspended devices. The noise spectra analysis confirms the lower level of 1/f noise in suspended graphene devices. Carbon nanotube sensor under the same conditions of design, manufacture, and measurement are implemented to compare with graphene devices, showing the prominent advantages of graphene as a sensing material.
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ABSTRACT: Carbon has a unique chemistry reflected in its wide presence in the inorganic and organic world – benzene, diamond, graphite, fullerene, carbon nano-tubes and now graphene – carbon seems to be at the centre of action in the playground of scientific research. In this review, synthesis and unique proper-ties of graphene and graphene-based composites have been discussed with particular emphasis on the envi-ronmentally benign (green) synthetic methods and their wide applications, especially in energy conver-sion, energy storage, electronics, biomedical and bio-sensing applications.Current science 08/2014; 107(3):397-418. · 0.83 Impact Factor
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ABSTRACT: In this study, an effective method was devised to synthesize amelogenin genes in solution and to amplify electrical detection of DNA hybridization based on graphene nanosheets (GNs) modified glassy carbon electrode (GCE). GNs are well known as effective biocompatible and conductive materials that can provide large surface area and a sufficient numbers of binding points for DNA immobilization. The biosensor fabrication processes and the electrochemical responses of probe immobilization and hybridization with target DNA were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) using [Fe(CN)6](3-/4-) as an electrochemical redox. Due to minimum nonspecific DNA adsorption, a very high specificity of DNA hybridization was achieved, and the hybridization rate of the target DNA in optimum conditions was increased significantly. With this approach, the target DNA could be quantified in a linear range from 1.0×10(-20) to 1.0×10(-14)molL(-1) for the first segment and from 1.0×10(-13) to 1.0×10(-6)molL(-1) for the second segment, with a detection limit of 7.1×10(-21)molL(-1) by 3sb. In addition, the biosensor exhibited a high level of stability and repeatability, even for the determination of DNA sequences in real samples without amplification. Copyright © 2015 Elsevier B.V. All rights reserved.Talanta 02/2015; 137. DOI:10.1016/j.talanta.2015.01.035 · 3.51 Impact Factor
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ABSTRACT: Rose water as a green reducing and stabilizing agent is introduced and used for the chemical reduction of exfoliated graphite oxide (GO) and the synthesis of reduced graphene oxide nanosheets (RGONs). The prepared materials are characterized with UV-visible absorption spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, atomic force microscopy (AFM), scanning electron microscopy, transmission electron microscopy and X-ray diffraction (XRD). The results of XRD analysis show that the oxygen containing functional groups of exfoliated GO have been removed remarkably after its reduction by rose water. AFM and Raman spectroscopy results indicate that the exfoliated GO has been reduced to monolayer RGONs. Electrochemical impedance spectroscopy measurements show that the rate of electron transfer of the redox probe on prepared RGONs is much higher than that observed on exfoliated GO, indicating the capability of the proposed method for the production of RGONs. Moreover, excellent electrocatalytic activity towards catechol, nicotinamide adenine dinucleotide and immobilized glucose oxidase is observed on a glassy carbon electrode modified with RGONs, indicating the applicability of the prepared RGONs for the fabrication of sensors and biosensors.RSC Advances 05/2013; 3(32):13365. DOI:10.1039/c3ra40856f · 3.71 Impact Factor