The Graphene Nanomaterial-based Electrochemical Sensors For Biologiy And Drug Molecules

Graphene （GR） is a new type of nanometer material. It has excellent properties of largespecific surface area, good conductivity, high surface reactivity, high catalytic efficiency, andhigh adsorption ability. Based on these merits, several graphene-based modified electrodeswere prepared and used for the electrochemical determination of some biomolecules anddrugs like native DNA, acetaminophen （ACOP） and oligonucleotides. The main contents areas follows:（1） A graphene-modified glassy carbon electrode （GR/GCE） was prepared throughphysical adsorption, which was characterized through electrochemical methods. The resultsshowed that GR on GCE surface significantly enhanced the specific surface area andelectrical conductivity. The electrochemistry of double-stranded fish-sperm DNA （fsDNA） onGR/GCE was further investigated, which showed that the electrooxidation peak of guanineresidues in fsDNA was obviously enhanced and the peak potential was significantly loweredas compared to bare GCE. The electrochemical parameters and influence factors formeasurements were investigated in detail. Quatatative analysis showed that the biosensor hasa linear range of1⁵00mg mL^-1with a detection limit of0.35mg mL^-1for fsDNA.（2） A hybrid material of graphene-chitosan nanocomposite modified glassy carbonelectrode （GR-CS/GCE） was prepared. The electrochemical behaviors of acetaminophen（ACOP） on a GR-CS/GCE were investigated by cyclic voltammetry, chronocoulometry anddifferential pulse voltammetry. Electrochemical characterization showed that the GR-CScomposite revealed an excellent electrocatalytic activity and surface area effect. As comparedwith bare GCE, the redox signal of ACOP was greatly promoted on GR-CS/GCE. Theelectrochemical parameters (electrode transfer rate constant ks=0.25s^-1, diffusion coefficientD=3.61×10^-5cm²s^-1), surface adsorption amount (Γ*=1.09×10^-9mol cm^-2) andelectrochemical reaction mechanism of ACOP （2e^-/2H⁺reaction） on GR-CS/GCE were allcomplete studied. Under the optimal conditions, the ACOP could be quantified in the range of1.0×10^-61.0×10-⁴mol L^-1with a low detection limit of1.0×10^-7mol L^-1. The interference,stability, reproducibility and regeneration experiments showed that the GR-CS modifiedelectrode can be applied as construct an excellent sensor for the determination of ACOP. （3） A new organic-inorganic nanocomposite containing GR and pyrenebutyric acid （PBA）was obtained by ultrasonication, which showed the characteristic of uniform and steady. Thedispersant was further dropped onto a gold electrode surface to get a GR-PBA modifiedelectrode （GR-PBA/Au）. Electrochemical behaviors of the modified electrode werecharacterized by cyclic voltammetry and electrochemical impedance spectroscopy.Additionally, the amino modified18-mer oligonucleotides were covalently immobilized onthe electrode surface to construct a new DNA biosensor. Through using methylene blue as aredox hybridization indicator, the peak currents of MB showed good linear relationship withthe logarithm value of target concentrations in the range from5.0×10^-15to1.0×10^-12mol L^-1with the detection limit of3.8×10^-16mol L^-1.（4） A new nanocomposite （GR-AuNRs@CTAB） containing GR andcetyltrimethylammonium bromide coated gold nanorod （AuNRs@CTAB） was prepared byultrasonication dispersion, which was further modified on the surface of carbon pasteelectrode （CPE） to obtain a new GR-AuNRs@CTAB modified electrode（GR-AuNRs@CTAB/CPE）. Electrochemical characterization showed that the modifiedelectrode has high catalytic efficiency due to the synergistic effect of GR and AuNRs. Themodified electrode showed a pair of reversible redox peak. The5’-thiol modifiedoligonucleotides was immobilized on the surface of electrode via self-assembly. Additionally,it was found that the characteristic signals of the electrode changed with the hybridizationreaction, which was further used for the electrochemical detection of the target sequence. Theresults showed that the indicator-free biosensor can effectively applied for ultrasensitivequantitative analysis of target with the range between1×10^-18mol L^-1and1×10^-12mol L^-1.