Synthesis Of Graphene Composite And Its Application In Sensor

Graphene, a two-dimensional nanomaterial with one atomic layer, has high specificsurface area and excellent mechanical, electrical, thermal and optical properties. Since its firstisolation in2004, researchers have suggested a large number of applications for this materialin the future of technological revolutions. But it has high chemical stability, inert surface state,and it is easy to agglomerate, which greatly limits its further research and application.Therefore, it is highly desirable to combine graphene with other materials with aim toimproving its performance, which shuold expand its field of application.Thereby, in this work, we designed and synthesized graphene composite material, andinvestigated their application in the sensors. The detailed contents are described as follows:Stable aqueous dispersion graphene/polyaniline (GR/PANI) composite is produced by afacile method, which involves the in situ polymerization of aniline on the surface of graphenewith the aid of polystyrene sulfonic acid (PSS). PSS is not only the dispersant of graphene,but also adsorb aniline onto the surface of graphene by the electrostatic interaction and thedopant of the aniline. The characterization of fourier transform-infrared spectrometry (FT-IR),ultraviolet-visible spectra (UV-vis), Raman spectra, atomic force microscopy (AFM),transmission electron microscopy (TEM) confrmed the successful synthesis of GR/PANIcomposite and strong interaction between PANI and GR. The prepared aqueous GR/PANIcomposite dispersion was very stable and no aggregation or precipitation was observed forseveral weeks. More interestingly, GR-PSS can dope PANI effectively and shift itselectroactivity to a neutral or even alkaline environment, making them promising candidatesfor biological application. In addition, the GR/PANI composite shows improved electricalconductivity and electrochemical stability compared to the neat polyaniline. The potential useof this composite for detection of ascorbic acid (AA) was investigated. A low detection limitof5×10-6mol L-1and a linear detection range between1×10-4mol L-1and1×10-3mol L-1was attained, indicating the high electrocatalytic ability of this composite. Furthermore,GR/PANI composite can be used for preparation of gas sensors towards ammonia, which hasgood detection sensitivity and resilience.A novel surface protein imprinted nanomaterial is synthesized by a one step approach,which employing graphene as the supporting substrate and dopamine as the polymerizingmonomer. By simply immersing graphene oxide (GO) in a weak alkaline solution of DAcontaining bovine hemoglobin (BHb), GO nanosheet was readily converted to reduced GO(RGO) by dopamine with simultaneous capping by a thin polydopamine film imprintedwith BHb, leading to the BHb imprinted PDA@RGO nanomaterials. Fourier transforminfrared (FT-IR), ultraviolet visible (UV-vis), Raman spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) andnitrogen adsorption experiments have been used to characterize the resulting imprintedPDA@RGO. the prepared imprinted PDA@RGO not only possessed high binding capacity(198mg/g), but also exhibited a fast adsorption kinetics (adsorb89%of the maximumamount within5min) and good selectivity toward template protein. Meanwhile, theimprinted material can also be applied in fabricating electrochemical sensor for detection ofBHb. The as-prepared MIPs sensor was test by DPV to investigate the relationship betweenthe response current and BHb concentration. Under experimental conditions, selectivedetection of BHb in a linear concentration range of1.0×10-9to1.0×101mg Ml-1withdetection limit of1.0×10-10mg mL-1was obtained. This new BHb electrochemical MIPssensor also exhibited excellent selectivity and good repeatability, and was used to thedetermination of BHb in urine samples with satisfactory results.