Preparation And Application Of Layer-by-layer Assembled Graphene/Polyaniline Multilayer Thin Films

Owing to graphene’s unique properties, the development of graphene-based functionalhybrids is currently attracting intense interest, of which the hybrids of graphene andconducting polymers such as polyaniline (PANI) have received much attention. It is expectedthat the combination of graphene with PANI will bring about some intriguing properties inview of their synergy effects. In this work, several novel graphene/polyaniline composite thinfilm was prepared by layer-by-layer assembly of graphene sheets and polyaniline.(1) A new kind of graphene/polyaniline multilayer film was fabricated through LBLassembly technique using negatively charged chemically converted graphene (CCG) andpositively charged polyaniline (PANI) as building blocks. By alternately immersing ITOsubstrate in negatively charged graphene solution and positively charged polyaniline solution,(CCG/PANI)nhybrid multilayer film was obtained. The structure characterization and surfacemorphology were investigated using ultraviolet-visible absorption spectrum (UV-vis), X-raydiffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), demonstratingthe successful fabrication of the CCG/PANI hybrid multilayer films. The electrochemicalperformance of the multilayer films was evaluated by cyclic voltammetry (CV). The resultsshowed that the (CCG/PANI)nfilm still presents a redox activity at neutral pH, which isattributed to the presence of carboxylic acid groups on the surface of grapheneacting as dopant of PANI and maintain an acidic micro-environment of thePANI chains. In addition, the multilayer film is very stable and it maintained itselectrochemical activity up to90.7%over100cycles. Furthermore, the multilayer filmsshows high electrocatalytic ability toward ascorbic acid with the linear range from1×10-4~1.2×10-3M and the detection limit of5×10-6M(signal/noise=3).(2) A new class of graphene/polyaniline multilayer film was constructed bylayer-by-layer self-assembly, using poly(sodium4-styrenesulfonate) stabilized graphenesheets (PSS-GS) and polyaniline (PANI) as building blocks. Poly(sodium4-styrenesulfonate)(PSS) was used not only to stabilize the graphene sheets, but also facilitate the growth of the(PSS-GS/PANI)nmultilayer films via electrostatic interactions between PSS-GS and PANI.Furthermore, PSS can also act as a dopant for PANI during redox reactions.Ultraviolet-visible absorption spectrum (UV-vis), Fourier transform infrared spectroscopy(FTIR), Raman spectroscopy and scanning electron microscopy (SEM) results demonstratethe successful fabrication of the (PSS-GS/PANI)nhybrid multilayer films. Electrochemicalexperiments show that PSS-GS inside the multilayer film can dope PANI effectively and themultilayer film still presents a redox activity at neutral pH. In addition, the obtainednanostructured (PSS-GS/PANI)nmultilayer film is very stable and shows high electrocatalyticability toward H2O2with the linear range from1×10-4~1.5×10-3M and the detection limit of6×10-6M (signal/noise=3), which makes it an ideal substrate for H2O2detection and offersgreat promise for sensing.(3) A novel graphene/polyaniline nanocomposite thin film was prepared bylayer-by-layer assembling the positive charged graphene sheets functionalized by the ionic liquid (IL-GR) and negative charged sulfonated polyaniline (s-PANI). The usage of IL notonly enhanced the dispersibility of graphene sheets, but also provided positive charge tographene and thus facilitate the growth of the multilayer films. More importantly, it enhancedthe electron transport pathway between graphene sheet and PANI, which is beneficial to theelectrocatalytic properties of (IL-GR/s-PANI)nhybrids. Ultraviolet-visible absorptionspectrum(UV-vis), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy,scanning electron microscopy (SEM) and cyclic voltammetry (CV), results demonstrated thesuccessful fabrication of the IL-GR/s-PANI hybrid multilayer films. Application of the(IL-GR/s-PANI)nfilm in electrochemical sensing was further demonstrated by use of H2O2asa model analyte. The IL-GR/s-PANI hybrid film showed excellent electrocatalytic activitytoward the reduction of H2O2, leading to an enzymeless H2O2sensor with a fast amperometricresponse time of less than2s. The proposed (IL-GR/s-PANI)nfilm based sensor exhibited awide linear detection of H2O2over the range of5×10-7M to2×10-3M, with an ultralowdetection limit of6×10-8M (signal/noise=3), which outperformed the most of reported H2O2electrochemical sensors. In addition, good anti-interference and stability was alsodemonstrated.