| With the rapid development of industry and agriculture,more and more environmental pollutants are discharged into the environment,which poses a great threat to the environment and human health.Therefore,it is of great importance to establish relevant analytical techniques with high accurate and sensitivity for the detection of the harmful substances in the environment.In recent years,the morden electrochemical sensing techniques based on nano materials chemically modified electrodes have been widely studied and applied in the environmental analysis due to its unique features including high sensitivity,good selectivity,as well as low cost.Among the nano materials,carbon and metal nano materials have been widely studied and applied in the field of electrochemical sensing due to their unique physical and chemical properties.In order to further expand the application of these nano materials in electrochemical sensing,design and synthesis of carbon-metal composite nano materials with special morphology and properties,using the synergistic action of all components in composite to further improve the analytical performance of the sensor has become a hot research field.In this paper,the application of carbon nano materials,including of graphene?GR?and carbon nano tubes?CNTs?,the metal nano particles?including gold and platinum?,as well as their nano composite in the electrochemical sensing has been firstly reviewed carefully.Based on this,several kinds of chemically modified electrodes based on carbon-metal composite nano materials have been fabricated through the dropping and electrochemical deposition techniques.These as-prepared modified electrodes had also been used for the detection of hydroquinone?HQ?,catechol?CC?,hydrazine,as well as hydroxylamine in environmental samples.The details are as follows:1.The platinum nano particels loaded on reduced oxide graphene?Pt NPs-RGO?were synthesized by one-step chemical reduction strategy using sodium citrate as reducing anddispersion agent in ethylene glycol?EG?system.The X-ray powder diffraction?XRD?,scanning electron microscopy?SEM?,energy dispersive spectroscopy?EDS?,as well as the electrochemical methods were used for the characterization of this composite.Benefiting from the strong interaction between Pt NPs and RGO,this nano composites had some excellent characteristics such as small particle size,good dispersion as well as high electrocatalytic activity.Based on this,a new electrochemical sensor with low detection limit,high sensitivity and wide linear range for the determination of hydrazine had been fabricated.Under the optimum conditions,the linear range of hydrazine by amperometry in p H 7.0 B-R buffer was from 5.0 × 10-8to 8.0 × 10-4mol·L-1.The detection limit and sensitivity was 1.0 ×10-8mol·L-1?3sb?and 333 ?A·m M-1,respectively.Compared to other sensors reported previously,the resulting modified electrode exhibited some attractive analytical features such as the wide linear range,low detection limits,as well as the high sensitivity.2.A glass carbon electrode was modified with a composite film made from gold nano particles?Au NPs?,zinc oxide?Zn O?and multi-walled carbon nano tubes?MWCNTs?by two steps procedure.Firstly,MWCNTs were modified on the GCE surface by dropping method.Then,gold nano particels and Zn O were electrochemically co-deposited on the surface of MWCNTs by cyclic voltammetry from a solution containing zinc nitrate and auric chloride acid and an Au NPs-Zn O/MWCNTs/GCE modified electrode was obtained.The element composition and electrochemical properties of this modified electrode were studied in detail.Furthermore,the electrochemical behaviors of hydroxylamine hydrochloride?HH?and hydrazine were also investigated in 0.10 mol·L?1phosphate buffer solution?PBS??p H = 7.0?and in B-R buffer?p H = 8.0?.The result showed that this modified electrode had high electrochemical activity for the oxidation of hydroxylamine hydrochloride and hydrazine with the synergic action of Au NPs,Zn O and MWCNTs.Under the optimized conditions,the linear range for the determination of hydroxylamine hydrochloride and hydrazine using amperometry was 2.0 × 10?7 4.9 × 10?4mol·L?1?6.6 × 10?4 2.3 × 10?3mol·L?1and 9.7 ×10?9 2.2 × 10?4mol·L?1,respectively.The detection limits?3sb?was 8.0 × 10?8mol·L?1and3.8 × 10?9mol·L?1,respectively.The sensitivity of the resulting modified for hydroxylamine hydrochloride and hydrazine was 90.0 ?A·(mmol·L-1)-1? 46.0?A·(mmol·L-1)-1)and 338?A·(mmol·L-1)-1,respectively.3.A carbon ceramic electrode?CCE?was modified with a composite film composed of gold nano particels?Au NPs?,overoxidized polypyrrole?OPpy?,and multi-walled carbon nano tubes?MWCNTs?by two steps procedure.Firstly,MWCNTs were modified on the CCE surface by dropping method.Then,OPpy and gold nano particels were electrochemically deposited on the surface of MWCNTs from layer by layer.The surface morphology and electrochemical properties of this modified electrode was studied in detail.Furthermore,the electrochemical behaviors of hydroquinone?HQ?and catechol?CC?were also investigated in 0.10 mol·L-1phosphate buffer solution?PBS??p H 7.0?using this modified electrode.The results showed that this modified electrode had high electrochemical activity and good selectivity for the oxidation of HQ and CC.Under the optimum conditions,the linear range for the simultaneous determination of HQ and CC by first derivative voltammetry is from 2.0 × 10-7to 1.0 × 10-4mol·L-1,respectively.The detection limit for HQ and CC is 6.0 × 10-8and 8.0 × 10-8mol·L-1?3sb?,respectively.4.A carbon ceramic electrode?CCE?was modified with a composite film composed of copper oxide?Cu O?,gold nano particels?Au NPs?,overoxidized polypyrrole?OPpy?,and multi-walled carbon nano tubes?MWCNTs?by two steps procedure.Firstly,MWCNTs were dropped on the surface of CCE.Then,Cu O,Au NPs and overoxidized polypyrrole OPpy were electrodeposited on the surface of MWCNTs from layer-by-layer.The electrochemical behavior and the electrocatalytic activity for the oxidation of glucose of this modified electrode had also been investigated carefully.The results showed that the anti-interfence ability and the atability of this modified electrode were improved with the presence of OPPy in composite.Moreover,the electrocatalytic activity of the as-prepared electrode were improved with the presence of Au NPs,Cu O nano particles and MWCNTs in composites.Under the optimum conditions,the linear range for the determination of glucose by amperometry in 0.10 mol·L-1Na OH is from 2.0 × 10-7mol·L-1to 1.4 × 10-3mol·L-1.The detection limits and the sensitivity for the determination of glucose is 8.0 × 10-8mol·L-1?3sb?,and 176 ?A·(mmol·L-1)-1,respectively.Compared to other sensors reported previously,theresulting modified electrode exhibited some attractive analytical features such as the wide linear range,low detection limits,as well as the high sensitivity,and can be used for the determination of glucose in human serum sample. |
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