| Carbon nanotubes (CNTs) and graphene are high-performance carbon nanomaterials. Their excellent electron transfer and electrocatalytic properties have attracted much interest in the field of electrochemistry. In this thesis, carbon nanotubes, graphene and graphene related nanomaterials were applied to study the electrochemical sensing of pharmaceuticals. The main contents were described as follows.In the first chapter, literature reviews about the properties of carbon nanotubes, graphene and graphene-based composites were presented. The various applications of sensors based on carbon nanotubes, graphene or doped-graphene nanocomposites were also supplemented.In the second chapter, the electrochemical behavior of ketoconazole (KC) on a multi-walled carbon nanotubes (MWCNTs)-modified glassy carbon electrode (GCE) was investigated. The MWCNTs remarkably promoted the electrochemical response of KC on the GC electrode To achieve a sensitive voltammetric determination of KC, experimental conditions such as solution pH, amount of MWCNTs, accumulation time as well as scan rate were systematically studied and optimized. Under optimized conditions, the differential pulse voltammetric (DPV) response on the MWCNTs-modified electrode was proportional to the KC concentration in the range of1.0x10-6-3.0x10-5mol L-1with linear regression equation exressed as I(μA)=2.08x106c (mol L-1)+0.8887,(R=0.9982), and detection limit of4.4x10-7mol L-1. Based on this MWCNTs-modified electrode, KC in a pharmaceutical drug was successfully determined.In the third chapter, the films of MWCNTs and DNA were assembled on the surface of a GCE to prepare DNA-based electrochemical sensor. The assembling of DNA was characterized by employing electrochemical methods, and the fabricated sensor was used as an electrochemical tool, to detect the damage of DNA caused by griseofulvin (GF) molecules. The effects of incubation time, as well as concentration of GF on the damage effect of DNA were studied. The result showed, that DNA helix structure could be disturbed greatly when it was incubated in the mixture of GF, with the effect further confirmed by UV-Vis spectroscopy method. It proves, that GF molecules intercalate into double helix structure of DNA, causing its uncoiling. The proposed electrochemical method using dsDNA/MWCNTs/GCE not only exhibits high-sensitivity, but also is suitable for preliminary study for detecting the interaction mode between GF and DNA, as well as other systems.The fourth chapter focuses on the fabrication of novel hybrid nanomaterial, composed of nitrogen-doped graphene (N-G) sheets and gold nanoparticles (AuNPs). The N-G was syntesized by simple hydrothermal process, with ammonia and hydrazine hydrate solution used as a dopant of nitrogen atoms and reducing agent, respectively. The N-G nanosheets decorated with AuNPs (Au/N-G) were synthesized by the reduction of HAuCl4on the surface of N-G using ethylene glycol as the reducing agent. The as-prepared hybrid material was characterized with various surface analysis techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results show that many AuNPs were effectively loaded on the surface of N-G via the proposed synthesis route. The electrochemical impedance analysis indicated that Au/N-G was an excellent electrode material possessing outstanding electrochemical features for electron transfer. Using developed Au/N-G modified GCE, the electrochemical response of chloramphenicol (CAP) were investigated, and it was found that Au/N-G can improve the sensing of CAP, with the reduction peak current linearly proportional to the concentration of CAP over the range of2.0x10-6-8.0x10-5mol L-1. The linear regression equation is expressed as I(A)=2.13c (mol L-1)+1.99x10-5,(R=0.9985), with limit of detection (LOD) estimated to be5.9x10-7mol L-1. Thus, a high-performance electrochemical sensor for CAP based on Au/N-G was developed.The fifth chapter deals with one-pot synthesis of graphene decorated with AuNPs, carried out in the presence of poly(diallyldimethylammonium chloride) solution (PDDA), as well as NaBH4served as reducing agent. The as-prepared hybrid nanocomposite (Au/PDDA/G) was characterized with various surface analysis techniques such as SEM, XRD and EIS. The electrochemical performance of Au/PDDA/G-modified GCE was investigated by studying the voltammetric behavior of levofloxacin (LV). Under optimized experimental conditions, at Au/PDDA/G/GCE, the detection limit of LV was estimated to be4.4x10-6mol L-1. The developed sensor was successfully applied for its sensitive determination in pharmaceutical tablets. Additionally, the investigation of interaction between LV and RNA moleculecules was carried out.In the sixth chapter, the boron-doped graphene (B-G) nanocomposite was prepared by NaBH4used as reductant and dopant of boron atoms during hydrothermal treatment of graphene oxide (GO), in the presence of PDDA. Hydrothermal reaction environment provides an efficient and facile approach to yield boron atoms incorporated into the structure of GNs, covered with PDDA polymer chains. At the synthesized PDDA/B-G nanocomposite modified GCE the electrochemical behavior of guanine was investigated. The results show, that the incorporation of B atoms into the structure of graphene significantly improved the electrocatalytic activity and voltammetric responses towards guanine in comparison with GCE modified with undoped graphene. The PDDA/B-G based electrochemical sensor exhibits linear relationship between guanine concentration and anodic peak current responses in the range from1x10-6to7.5x10-5mol L-1. The regression equation could be expressed as I(A)=0.5344c(mol L-1)+1.5O3x10-6,(R=0.9990), with LOD of3.9x10-7mol L-1for guanine determination. The excellent performance of this electrochemical sensor can be attributed to the high electrocatalytic properties of B-G nanocomposite, which provides an efficient platform for this purine base electrochemical sensing. |
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