Fabrication Of Graphene Nanoribbons Functional Hybrid Nanomaterials Based Electrochemical Sensors And Their Applications In Genetically Modified Soybean Detection

With the increaseing of transgenic soybean varieties and planting area,its security has become the focus of attention.Therefore,it is of great significance to establish a sensitive,rapid and convenient method of transgenic soybean in order to promote product safety regulation and guarantee citizens health.Due to the advantages of high analysis speed,high sensitivity and easy to operate,electrochemical sensors have become a hot research topic in the field of food safety regulatory analysis.In this thesis,the novel,convenient and label-free of electrochemical sensors were constructed for the detection of transgenic soybean CaMV 35 S promoter?P35S?based on the excellent electrochemical properties of graphene nanoribbons functional nanomaterials,details of which are described below:1.The gold nanoparticles/multiwalled carbon nanotube-reduced graphene oxide nanoribbons?Au NP/MWCNT-rGONR?nanocomposites were synthesized by a one-pot reaction.Electrochemical impedance sensor interface was constructed based on fixing capture probe on the surface of hybrid material through the ?-? interaction between capture probe and hybrid material.The proposed sensor was realized the target gene detection because of increaseing of electronegativity density when a DNA complex was formed between target genes and capture probe.The platfom showed a good linear relationship between impedance change value and P35 S concentration from 0.1 fM to 500 pM with a limit of detection of 0.03 fM?S/N = 3?.Moreover,the sensor has good selectivity,stability and reproducibility,which couble be applied totransgenic soybean sample identification.2.Nitrogen doped graphene nanoribbons doped titanium dioxide?TiO₂/NGNRs?hybrid materials were prepared via a facile one-pot heat treatment method.The photocurrent intensity of TiO₂/NGNRs nanocomposites exhibited 5 times higher than that of TiO₂.The introduction of NGNRs can improve the electrical conductivity of hybrid materials,promote the photoinduced carriers separation efficiency and suppress recombination of the electron-holes.Further,a novel photoelectrochemical?PEC?sensor was fabricated based on TiO₂/NGNRs nanocomposites as the carrier and fixed gene probes through the chemical crosslinking glutaraldehyde method.The target gene detection was realized through the attenuation of photocurrent because inert double-stranded DNA between capture probe and P35 S target gene suppressesthe ascorbic acid?AA?capture hole.Under the optimal conditions,the proposed sensor displayed a wide linear range from 0.5 to 1.3 nM with a low detection limit of0.17 nM?S/N = 3?.In addition,the sensor has good selectivity,stability and could be implemented the identification of the soybean samples.3.Further,ternary Ag-TiO₂/NGNRs nanocomposites have been synthesized by a facile one-step heat treatment method.The Ag-TiO₂/NGNRs nanocomposites exhibited enhanced PEC performance,about 2-fold of TiO₂/NGNRs and 10-fold of TiO₂ monomer,indicating that the Ag can improve the ternary PEC performance of TiO₂ nano hybrid material due to the surface plasma resonance effect of Ag.Transgenic soybean P35 S PEC sensor was constructed by fixing thiol probe on the surface of nanometer Ag.On the basis of the above PEC detecting mechanism,the target gene detection realized.Under the optimal conditions,the PEC genosensor displayed a wide linear range?0.01 nM 500 nM?,a low detection limit?0.0033 nM,S/N = 3?,high stability and reliability to identify transgenic soybean samples.