| Bimetallic nanomaterial is a new type of nanomaterial which is composed of two different metals through a certain synthetic method.It has been widely used in optics,electronics,biomedicine,sensors and other special catalytic fields because of its unique micro-morphology,high atomic utilization rate,good stability and excellent photocatalytic performance.Graphene(Gr)is a two-dimensional nanomaterial with only one carbon atom thickness,which contributes to promote conductivity and increase specific surface area.However,due to its poor dispersion and easy agglomeration,it is usually functionalized to overcome this disadvantage.In this study,we used poly(diallyldimethylammonium chloride)(PDDA)functionalized graphene as the substrate and loaded the different bimetallic nanoparticles(Pt-Pd,Pt-Cu,Co-Ni)onto the graphene surface to construct three different sensitive electrochemical sensors,realizing the determination of azo dye sunset yellow(SY)with high sensitivity.In addition,in order to improve the selectivity of electrochemical sensors,a special electrochemical sensor was developed based on molecularly imprinted polymer(MIP),which was loaded on the surface of Pd-Cu bimetallic nanomaterial functionalized PDDA-Gr.This sensor takes advantages of molecularly imprinted technique with specific recognition to realize the determination of amaranth with high selectivity and sensitivity.The detailed studies are as follows: 1.Construction of novel electrochemical sensors based on bimetallic nanoparticle(Pt-Pd,Pt-Cu,Co-Ni)functionalized graphene for determination of sunset yellow in soft drinkThree novel bimetallic nanomaterials with different composition and morphology including Pt-Pd bimetallic nanocages,Pt-Cu bimetallic nanoframes and Co-Ni bimetallic nanoflowers were synthesized and loaded onto the PDDA functionalized graphene.The obtained PDDA-Gr-(Pt-Pd),PDDA-Gr-(Pt-Cu)and PDDA-Gr-(Co-Ni)nanocomposites remarkably increased the electrochemical response towards sunset yellow.The nanocomposites were characterized by Ultraviolet and visible spectrometry(UV-vis),X-ray diffraction(XRD),energy-dispersive X-ray spectroscopy(EDX)and transmission electron microscopy(TEM).The electrochemical properties of the developed sensors were investigated and compared by cyclic voltammetry(CV),electrochemical impedance spectroscopic(EIS)techniques and differential pulse voltammetry(DPV).Under optimal experimental condition,the anodic peak currents of sunset yellow on three modified electrodes were linearly correlated with the concentration of sunset yellow in the ranges of 0.02–10.0 μM,0.02–10.0 μM,0.008–10.0 μM,respectively.The limits of detection(LOD)of SY were 6.0,4.0 and 2.0 nM,respectively.The three new proposed sensors in this study were successfully applied to determine SY in real soft drink samples.In addition,the design provides the reference for a new platform for designing sensitive electrochemical sensor based on non-noble metals with low cost.Especially the Co-Ni bimetallic nanomaterial with distinct nanoflower structure displayed excellent electrochemical properties over Pt-Pd and Pt-Cu,which indicate the possibility of non-noble metals with better property over noble metals.This also opens the possibility to design more non-noble nanomaterials with excellent properties.2.Construction of sensitive and selective molecularly imprinted electrochemical sensor based on Pd-Cu bimetallic alloy functionalized graphene for detection of amaranth in soft drinkA special electrochemical sensor was developed based on molecularly imprinted polymer(MIP),which was formed by the dopamine(DA)self-polymerization on the surface of Pd-Cu bimetallic alloy functionalized PDDA-Gr.This sensor takes advantages of molecularly imprinted technique and nanocomposite to realize the application of amaranth determination with high selectivity and sensitivity.After optimization,the anodic peak current showed a linear relationship with the concentration of amaranth in the range of 0.006-10 μM,and the limit of detection(LOD)was 2 nM.The proposed sensor distinguished amaranth from other structurally similar substances such as sunset yellow and tartrazine with high sensitivity and selectivity.In addition,the molecularly imprinted sensor proposed in this study was successfully applied to determine amaranth in the soft drink with satisfactory recoveries.The combination of molecularly imprinted technique and nanocomposite provides high selectivity and sensitivity for electrochemical sensors design. |
