Fabrication Of Graphene-CdS Nanocomposites And Their Applications In Photoelectrochemical Biosensing

As a newly developed chemical analytical method, photoelectrochemical sensor is based on the photoelectrochemical properties of the materials. In the photoelectrochemical detection process, light is used to excite photoelectrochemically active species on the electrode, and current is used as the detection signal, which is just the reverse process of electrochemiluminescence. Benefiting from the effective separation of the excitation light source and detection signal, photoelectrochemical sensor has many advantages, shch as high sensitivity, low background signal, simple device and so on. In addition, the use of electronic readout makes the instrument simpler, cheaper, and easier to miniaturize than that of optical detection methods. Thus, this technique has shown promising analytical applications in DNA detection, immunoassays and other bioanalytical fields, with good prospects for development.Bulk CdS is a typical Ⅱ-Ⅵ semiconductor material with the narrow band gap of2.4eV. CdS can absorb visible light, that is one of the most widely used semiconductor materials in solar cells.. What’s more, the preparation of CdS is very convenient and cheap, so CdS nanoparticles are widely used in the photochemical, electrochemical, electroluminescent and photoelectrochemical sensor. As a new carbon nano-material, Graphene (GR) has attracted widely attention. GR owns extremely excellent conductive properties, in which electrons are able to migrate very efficiently, far beyond the traditional semiconductors and conductors. For optoelectronic devices, in introduction of GR may improve the charge separation and accelerate the charge transfer, thereby enhancing the optoelectronic properties. In this work we prepared GR-CdS nanocomposites with enhanced optoelectronic properties through a simple one-step routine. Based the as prepared GR-CdS nanocomposites, photoelectrochemical biosensors with good performance for the detection of biological molecules were constructed. The major contents are as follows:1. Graphene-CdS Nanocomposites:Facile One-Step Synthesis and Enhanced Photoelectrochemical CytosensingGraphene-CdS (GR-CdS) nanocomposites were prepared by a novel, one-step synthetic route in aqueous solution. The synthetic approach is simple and fast, which may be extended to synthesize other GR-metal sulfide nanocomposites. The as-prepared GR-CdS nanocomposite film inherited the excellent electron transport property of GR. In addition, the GR-CdS heteronanostructure facilitated the spatial separation of charge carrier, therefore resulting in enhanced photocurrent intensity, and making it a promising candidate for photoelectrochemical application. A novel photoelectrochemical cytosensor was fabricated based on the prepared GR-CdS nanocomposites via a layer-by-layer assembly process. The photoelectrochemical cytosensor showed a good photoelectronic effect and cell capture ability, and had a wide linear range and low detection limit for Hela cells. The as-synthesized GR-CdS nanocomposites exhibit obviously enhanced photovoltaic properties, which could be an efficient platform for many other high-performance photovoltaic devices.2. Fabrication of Glutathione Photoelectrochemical Biosensor Using Graphene-CdS NanocompositesWith the assistant of hydroxylamine as the complex and morphology control agent, graphene-CdS (GR-CdS) nanocomposites were synthesized in an aqueous reaction. Since the introduction of hydroxylamine, the size of CdS nanoparticals were smaller and uniformer. The obtained GR-CdS nanocomposites had better crystalline structure, size distribution and dispersion, which lead to a better photovoltaic performance. A novel photoelectrochemical biosensor for glutathione (GSH) detection was successfully constructed based on the newly synthesized graphene-CdS (GR-CdS) nanocomposites.The proposed GSH photoelectrochemical biosensor displays satisfactory analytical performance with an acceptable linear range from0.01to1.5mmol L-1with a detection limit of0.003mmol L-1at a signal-to-noise ratio of3, and also shows an excellent specificity against anticancer drugs and could be successfully applied for GSH detection in real samples. The as-synthesized GR-CdS nanocomposites exhibit obviously enhanced photovoltaic properties, which could be extended to other enzymes and biomolecules detection, thus providing a promising platform for the development of photoelectrochemical biosensors.