Graphene based nanocomposites and nanostructures: Analytical applications

Metal oxides and carbon nanoparticles are an important group of nanomaterials playing essential role in the development of analytical techniques. A large amount of research is devoted to improve an analytical method from view point of linear response range, limit of detection, sensitivity, selectivity and simplicity. This lecture was aimed to discuss the last scientific achievements in our laboratory in the two subsections:In the first section, development of cost-effective and simple procedures for immobilization of graphene quantum dots and/or graphene nanosheets to the natural bio-wastes like egg shell calendula (ESC), egg shell membrane, ESM, [22], soluble egg shell proteins (SEP) are described. In some cases the mentioned adsorbents were combined to Fe3O4 magnetic nanoparticles to facilitate extraction procedures. The resulting nanocomposites were used as new adsorbents for removal of textile dyes like Congo red [1], extraction, preconcentration and determination of some organic pollutants such as organophosphate pesticides (OPPs) and polycyclic aromatic hydrocarbons (PAHs) by high performance liquid chromatography, HPLC-UV method. Capability of all proposed methods for analysis of some real samples were thoroughly investigated and compared with other similar methods [2-5].The second section was devoted to direct electrochemical synthesis of graphene nanosheets as a thin film on the carbon material surface like pencil lead substrates. The resulting probe was referred as graphenized electrode. Various parameters effecting the quality and stability of graphenized carbon substrate were optimized. Graphene coated pencil lead was tested as solid phase microextraction (SPME) fiber for preconcentration and chromatographic analysis of PAHs. When this fiber was coated with polyaniline (PANI) by electro-polymerization procedure, the figures of merits were remarkably improved.In the third section graphenized pencil lead was used as working electrode and its catalytic properties were surveyed for electroanalysis of amino acids (L-Tyrosine and Tryptophan). This electrode was used for electro-deposition of cobalt oxide nanoparticles (CoOx). CoOx nanoparticles anchored on the graphene nanosheets showed excellent electrocatalytic activity toward the oxidation of insulin. Linear response range and limit of detection were obtained as 0.46 – 100 nM and 0.11 nM respectively.