Construction Of Graphene Aerogel Composite Electrode And Electrochemical Detection Of Food Additives

With the rapid economic development and the continuous improvement of people’s living standards,food safety has increasingly become the focus and hot issue of social concern.Recently,the excessive use of food additives and the residues of vegetables,fruits and pesticides have caused a great impact on people’s lives.Therefore,it is essential to establish a fast,efficient and sensitive food analysis method.However,the complex operating procedures and the high cost have limited their further detection application.Electrochemical methods have attracted widespread attention due to their fast response,simple operation,high sensitivity,and good selectivity.For this,combined with comprehensive reports from the literature,a series of electrochemical sensor based on the graphene aerogel composites were prepared based on the characteristics of high conductivity,large effective surface area,and good stability of graphene aerogels.The details are as follows:（1）β-Cyclodextrin（β-CD）with supramolecular recognition capability is widely used as signal amplifier in the fabrication of electrochemical sensor.Unfortunately,its poor electrical conductivity limits its application.To improve its conductivity and increase the loading ofβ-CD on the modified electrode,in this paper,three-dimensional（3D）porous graphene aerogels（GAs）were introduced as substrate material.The as-preparedβ-CD/GAs composite offers high electrical conductivity,large specific surface area of 3D GAs coupled with the excellent adsorption ability ofβ-CD,and its application as electrochemical sensing platform for Ponceau 4R detection was investigated.Benefiting from the synergy betweenβ-CD and GAs,theβ-CD/GAs electrode could detect Ponceau4R in a wide linear ranging from 1.0 nmol/L to 1.0μmol/L with a low detection limit of 0.3nmol/L.Furthermore,theβ-CD/GAs electrode also exhibited good anti-interference performance and long term stability,and was capable of detecting Ponceau 4R in the food samples.（2）Molybdenum disulfide（MoS₂）,a typical two-dimensional（2D）transition metal disulfide with good electrocatalytic activity has been considered as charming sensing material due to its adequate exposed active edges.However,2D sheet-like structural MoS₂tends to aggregate,reducing its specific surface area.In addition,the poor conductivity of MoS₂limits its electrochemical application.To address these issues,in this work,graphene aerogels（GAs）,a three-dimensional（3D）nanoarchitecture with large specific surface area,rapid electron transfer and excellent electro-catalytic activity has been employed as an admirable framework support for MoS₂.By a facile one-step hydrothermal technique,the peeled MoS₂sheets were incorporated into GAs network.The MoS₂/GAs composite was investigated by scanning electron microscope（SEM）,X-ray diffraction（XRD）and X-ray photoelectron spectroscopy（XPS）.The composite combined excellent electrical conductivity and huge effective surface area of GAs,and the high catalytic activity of MoS₂nanosheets.Because of these advantages,the MoS₂/GAs composite was thus applied as electrochemical sensing platform for caffeic acid（CA）detection.The sensor performed good selectivity,wide linear ranges（1.0 nmol/L-10.0μmol/L）and low limit of detection（0.3 nmol/L）for CA detection.Furthermore,the designed sensor represented good reproducibility,stability and was successfully applied for detecting CA in red wine samples.（3）Nano-sized tungsten disulfide（WS₂）is used to improve the physicochemical properties of graphene aerogels（GAs）.The nanosheets were directly integrated into the 3D network structure of GAs by a solvothermal mixing method,and the WS₂wafers were assembled onto a conductive graphene network.WS₂with highly exfoliated and defect-rich structures allows the WS₂/GAs composite to have a rich active site that enhances the electrocatalytic properties of the composite.Introducing poorly conductive WS₂into the 3D GAs system reduces the background current when GAs is used as an electrode.This is advantageous in terms of signal to noise ratio and general analytical performance.The nitrite concentration range was 0.01-130μmol/L and the lower limit of detection was 3 nmol/L（S/N=3）.The electrode has selectivity,repeatability and stability and can be successfully applied to the determination of nitrite in bacon samples.（4）A ratiometric electrochemical strategy with dual-signal was developed to detect SY.The strategy had an intrinsic built-in correction to the effects from system,and thus reduced the influence of the environmental change.3D polyethyleneimine functionalized reduced graphene oxide aerogels@Au nanoparticles/SH-β-cyclodextrin（PEI-r GAs@Au NPs/SH-β-CD）was used as sensing material due to its 3D macroporous microstructure with high specific surface area and excellent electronic conductivity.Guest molecule methylene blue（MB）was chosen as a probe molecule,which formed inclusion host-guest complex with SH-β-CD host in advance.The target molecule SY would displace MB from CD cavities,resulting in the decrease of MB current and the increase of SY current.With the logarithmic value of I_SY/I_MBas readout signal,the detection limit of the developed ratiometric electrochemical sensor reached as low as 0.3?n M,confirming the excellent sensitivity.Furthermore,this strategy exhibited good selectivity and repeatability,and could be used for the detection of SY in real sample.