Graphene (Analogous)-Based Polyaniline And Its Derivatives For DNA Sensing Interface

Graphene (analogous)-based conducting polymer has attracted many researchers’ wide interestings due to its excellent electrical conductivity and unique functional groups. In this paper, three kinds of nanocompoites were prepared through chemical polymerization aniline or its derivatives monomer on the supporting material graphene (analogous) substrate. Afterward, a series of electrochemical sensing investigations were performed based on those three kinds of nanocompoites modified electrodes. The specific work can be divided into the following three points:(1) Graphene oxide (GNO) was served as the supporting material to synthetise polyaniline-graphene oxide (PANI-GNO) nanocomposites, which possessed different morphologies and were used as platfroms for comparing the DNA sensing behavior. Owing to GNO acting as an outstanding support or template for the nucleation and growth of polyaniline (PANI), the nanostructure graphene-based polyaniline nanocomposites were successfully obtained. Nevertheless, if GNO supporting being absent, the random connected PANI nanowires would be produced. Furthermore, the morphologies of PANI-GNO nanocomposites made in ice bath can be easily controlled by adjusting the reaction time that means the different reaction time brought the various formations of PANI-GNO nanocomposites, including small horns (5 and 12 h), vertical arrays (18 h), and nanotips (24 h). The next-step electrochemical data showed that the DNA electrochemical sensors constructed on the different morphologies PANI-GNO nanocomposites exhibited different ssDNA surface coverage and hybridization efficiency. Vertical arrays (18 h) exhibited the most optimal detection limit (2.08 × 10-16 M) compared with other morphologies of PANI-GNO nanocomposites (5,12 and 24 h). Conclusions as a result, vertical arrays (18 h) with higher surface area as well as more accessible space can offer an optimal balance for the immobilization and hybridization detection of probe DNA (pDNA).(2) A variety of nanocomposites were prepared based on GNO, aniline (ANI) and m-aminobenzenesulfonic acid (ABSA) monomer, via changing the synthetic conditions (such as component, monomer composition (mole ratio of ANI to ABSA), and reaction time) for the comparison of DNA sensing behavior. Self-signals of nanocomposites were employed for evaluating the effects of preparation conditions on pDNA immobilization and hybridization detection. Then, we found herein that the mole ratio of ANI to ABSA played a lead role over other factors on hybridization efficiency. Meanwhile, the parallel experiments using methylene blue (MB) as the classic indicator verified this conclusion. By comparison with the sensitivity of other mole ratio sulfonated polyaniline-graphene oxide (SPAN-GNO) nanocomposites modified electrodes, the mole ratio (2:3) exhibited the widest dynamic detection range from 1.0 × 10-14 to 1.0 × 10"6 M, as well as the most optimal detection limit (3.06 × 10-15M).(3) A novel polyaniline-molybdenum disulfide (PANI-MoS2) nanocomposite was prepared through a facile oxidation polymerization aniline monomer on the pre-obtained thin-layer molybdenum disulfide (MoS2) matrix via a simple ultrasonic exfoliation method. It is generally appreciated that conducting polymers, e.g., PANI, can work as a direct transducer based on themselves-signal without any label or indicator. Moreover, MoS2 not only serves as an excellent conductive skeleton provided a high electrolytic accessible surface area for redox-active PANI, but also supports a direct path for electron transfer. Therefore, the hybrid of PANI and MoS2 exhibits superior electrochemical performance to pure PANI and MoS2, and can be considered as a superior candidate for direct and label-free electrochemical DNA sensing. A series of experiments were performed to investigate the effect of synthetic conditions (component, dosage of MoS2 and reaction time) on pDNA immobilization and hybridization adopted the PANI self-signal as the measure signal. The results show that the dosage of MoS2 has a more influence on pDNA immobilization and hybridization, which has been proved by the parallel experiments using MB as the external indicator. For the purpose of high sensitive DNA detection, the relationship between the dosage of MoS2 and DNA detection sensitivity was researched. With the dosage of MoS2 increasing from 0.009 to 0.072 g, at 0.054 g, the detection limit for the CaMV35S gene sequence achieves its optimal.