Studies On Electrochemical Chiral Sensors Based On Carbon Nanocomposites And Metal Nanoparticles

Chiral phenomenon is ubiquitous in nature and represents the essential nature of life process. Plentiful chiral compounds which are closely related to the life process exist in organisms, such as sugars, amino acids, proteins and DNA molecules. Different isomers of chiral molecules have obvious differences in the physiological activities of the organism, pharmacological effects and metabolic process. However, it is very difficult to distinguish chiral enantiomers because the enantiomers have similar physical and chemical properties. Thus, the development of simple, rapid and sensitive method for chiral recognition is crucial. Electrochemical sensor is becoming a new method applied in the study of chiral recognition, due to its advantages of simple operation, low cost, high sensitivity, high selectivity and good stability. The performance of electrochemical sensor goes hand in hand with the modification material on the surface of electrodes; therefore, it has been one of the main research directions of the electrochemical sensor to seek appropriate modified materials for improvement of sensor performance. Carbon nanocomposites are of high specific surface area, high conductivity, good electric catalytic, excellent chemical stability, etc., and widely used in the fields of chemical modified electrode and electrochemical sensor. As one of the most-used nanomaterials used to modify electrode, metal nanoparticles have a lot of advantages, such as large specific surface area, good stability and surface modification, act as an ideal carrier for chiral recognition field. This paper is to build a novel electrochemical chiral sensor via combination of particular properties of carbon nanocomposites and metal nanoparticles to chiral distinguish and detect the tryptophan enantiomers and ascorbic acid enantiomers. The main works are included as follows: 1. A kind of nanohybrids, β-cyclodextrin, platinum nanoparticles and graphene(β-CD-PtNPs/GNs), was synthesized by wet-chemical method, and characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), fourier transform infrared spectroscopy(FT-IR) and electrochemical impedance spectroscopy(EIS). Then they were used to construct a simple and reliable chiral sensing platform for enantioselective recognition of tryptophan(Trp) enantiomers. Differential pulse voltammetry(DPV) was used to investigate the stereo selectivity of β-CD-PtNPs/GNs to Trp enantiomers. The results indicated that β-CD-PtNPs/GNs possessed favourable discrimination ability toward Trp enantiomers, due to the stronger enantioselective affinity of β-CD-PtNPs/GNs toward L-Trp. 2. An electrochemical chiral sensor was fabricated for recongnizing ascorbic acid(AA) and isoascorbic acid(IAA) based on new nanohybrids. The HS-β-cyclodextrin/gold nanoparticles/hollow carbon microspheres(HS-β-CD/AuNPs/HCMS) hybrids were successfully synthesized, and characterized by scanning electron microscopy(SEM), energy-dispersive X-ray spectroscopy(EDX), fourier transform infrared spectroscopy(FT-IR), cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS). A chiral sensing platform constructed by the prepared hybrids was used for distinguishing AA and IAA, and the stereo selectivity of HS-β-CD/AuNPs/HCMS to AA/IAA was investigated by differential pulse voltammetry(DPV). The results showed that obvious difference of peak currents of AA and IAA was obtained, demonstrating this strategy could be employed to enantioselectively recognize AA/IAA. 3. A chiral sensing platform has been fabricated by reduced graphene oxide(GNs), the electrodeposition of gold particles(dpAu) and ascorbic acid oxidase(AO). Scanning electron microscopy(SEM) and cyclic voltammetry(CV) were used to characterize the modified electrodes. The differential pulse voltammetry(DPV) was applied to investigate the interaction between the modified interfaces and ascorbic acid(AA)/isoascorbic acid(IAA), and a larger peak current has been obtained from IAA. The results demonstrated that the proposed sensing plateform could identify AA/IAA and had a stronger interaction toward IAA.