Preparation And Application Of Graphene-inorganic Nanocomposite For Electrochemical Sensors

Electrochemical methods have received considerable attention due to their greatadvantages, such as simple operation, fast response, good sensitivity and in situdetection. Graphene, a two-dimensional sheet of sp2-hybridized carbon atoms packedinto a honeycomb lattice, has led to an explosion of interest in the field of materialsscience, physics, chemistry, and biotechnology since the few-layers graphene flakeswere isolated from graphite in2004. This unique nanostructure material has lowmanufacturing cost, high surface area, excellent electrical conductivity, uniquegraphitized basal plane structure, and strong mechanical strength. Such propertiesindicate that graphene may be a good electrocatalyst or a support for electrocatalysts.Graphene can be combined with various inorganic nanomaterials through differentarchitecture types and synthesis techniques. The graphene–inorganic nanocompositesare expected to not only preserve the favorable properties of graphene and theinorganic nanocomposites, but also greatly enhance the intrinsic properties due to thesynergetic effect between them. Compared with the conventional electrode,ultramicroelectrodes has excellent intrinsic characteristics, such as temporal resolution,high current densities and reduced ohmic drop. They can be applied in organicsolvents with low conductivity and in vivo analysis. This work synthesizedgraphene-inorganic nanocomposites with green reduced reagents. We used them onthe carbon fiber disk ultramicroelectrode for the determination of pollutants.1. Because of the ability of forming film, chitosan was widely used inelectrochemistry. AgNO3and graphene oxide can be reduced by chitosan. Uniformlydispersed Ag-AgCl nanocubes (Ag-AgCl NCs) were successfully obtained ongraphene through the simultaneous reduction of AgNO3and graphene oxide bychitosan in the presence of little HCl. Hydroquinone (HQ) and catechol (CT) widely exist in environment as a kind of important pollutant because they are toxic to humansand difficult to be degraded. We found carbon fiber disk ultramicroelectrode (CFME)can simultaneously determine HQ and CT, directly. Conjugated polymers derivedfrom heterocyclic compounds have emerged as promising materials for immobilizingnanomaterials due to their conducting nature and high stability. In order to improvesensitivity, as-synthesized Ag-AgCl NCs/GN was immobilized on the surface ofpoly(5-amino-1,3,4-thiadiazole-2-thiol) modified CFME for the simultaneousdetermination of HQ and CT with good sensitivity.2. A new composite derived from a new porous organic matrix materials MsMOP-1and truncated triangular silver nanoplates (AgTP) was used as electrode material forthe determination of p-nitrophenol (p-NP) and o-nitrophenol (o-NP). The synthesis ofMsMOP-1had been reported and applied in organic reactions. But it has not beenused in electrochemistry. The purification of wastewater polluted by nitrophenols is avery hard task because of the high stability of these molecules in terms of chemicaland biological degradation. The prepared MsMOP-1/AgTP/CFME can be used for thedetection of p-NP and o-NP in the lake water and tap water.3. Chemical reduction of graphene oxide is the most common method for preparinggraphene. However, many reducing agents are toxic. Mushrooms are rich in aminoacids, vitamins, polysaccharides and proteins. Because of their antioxidant,antimicrobial, antiinflammatory, antitumor and anticancer abilities, they received theattention of researchers. Mushroom extracts can be obtained by heating. The reducingability of mushroom extracts had been reported, we used the mushroom extracts torestore the graphene oxide to graphene. Studies show that continuous overuse of kojicacid is carcinogenic and tumorigenic. Cu(salen)/GN/GCE was used to determine kojicacid with satisfactory results.4. Mushroom extracts can reduce potassium ferricyanide with the production ofprussian blue nanocubes (PBNCs), but they were aggregated. The reduction ofgraphene oxide and K3[Fe(CN)6] with mushroom extracts provided a green and facilemethod to produce PBNCs/GN. Due to the formation of inclusion complex betweenp-nitrophenol and β-CD, the β-CD/PBNCs/GN/GCE system showed linear behaviorin the range from0.01to700μmol L-1for p-Nitrophenol with a low detection limit of2.34nmol L-1(S/N=3).