Preparation of Graphene by Liquid Phase Exfoliation of Graphite and its Application in Electrochemical Biosensing

Abstract

Graphene, a wonder material, has open door in science and technology for numerous modern applications. However full exploitation of its novel properties requires production at large scale. Liquid phase exfoliation of graphite is one of the promising ways for rapid and economical production of pristine graphene at mass scale. Here, we prepare graphene in organic solvents NMP and DMF with different surfactants for example decanol, dodecanol and tetradecanol. Graphite exfoliation was assisted by ultrasonication in 3h. Using UV-Visible spectroscopic analysis we observed that increase in the chain length of alkyl alcohols improves the yield of graphene dispersion. Similarly moderate concentration of surfactants (0.5 mg/mL) was found to be optimum for improve yield. Highest yield of graphene dispersion obtained was 1.76 mg/mL in NMP with tetradecanol of 0.5 mg/mL. FTIR study shows the formation of unfunctionalized graphene. We determined the delamination of graphite through XRPD and confirm the formation of few (<5) layer graphene by Raman spectroscopy. The observed low ID/IG ratio indicates the formation of defect free graphene. SEM micrographs show few layer graphene flakes of various sizes from sub μm to few μm. We utilized graphene in the synthesis of graphene-polyaniline-copper oxide based nanocomposites for electrochemical nonenzymatic glucose biosensing applications. Four different nanocomposites graphene/polyaniline (GP), polyaniline/copper oxide (PC), graphene/polyaniline/copper oxide-1 (GPC1) and graphene/polyaniline/copper oxide-2 (GPC2) were prepared for comparative study. XRPD and SEM analysis revealed the homogeneous composition of nanocomposites with copper nanoparticles in various phases (mainly Cu2O) and particle size in the order of ~70 nm. We performed cyclic voltammetry and chronocoulometry in order to observe electrochemical response and surface area of nanocomposites. The nanocomposites were drop casted over glassy carbon electrode (GCE) in standard solution of 2 mM K3[Fe(CN)6] in 2M KCl solution. Chronocoulometry study showed improved surface area of modified GCE compared to the bare GCE. Cyclic voltammetry study of modified electrodes in 2 mM glucose in 0.1M NaOH show lowest response of bare GCE and highest response of GPC2/PVB/GCE. Electrochemical sensing of GPC2/PVB/GCE toward various concentrations of glucose shows linear range of detection 0.01 to 5 mM (R = 0.9781), sensitivity of 179.18 μA mM-1cm-2 and limit of detection (LOD) as low as 6.26 μM.