Preparation Of 3D Graphene/gold Composite And Its Application In Electrochemical Sensor

As the first two-dimensional atomic crystal, graphene possesses many superior physical and chemical properties and justifies its nickname of “miracle material”. 3D Graphene materials have gained great attention in the recently years owing to their large specific surface area, high conductivity and unique structures. Though much progress has been made, the present 3D graphenen materials also lack the desired electrochemical properties for their applications in sensors. Here, we study on synthesis of 3D graphenen with high electrochemical activity and catalytic ability, and extend its application in electrochemical sensors.Using a novel strategy to synthesize 3D-nitrogen-doped activated graphene(3D-N-doped AG). First, the mixture of graphite oxide, 2,4,6-trihydroxybenzaldehyde, urea and potassium hydroxide were dispersed in water and subsequently heated to form a graphene oxide hydrogel. Then, the hydrogel was dried by freeze-drying and reduced by thermal annealing in an Ar/H2 environment in sequence. The resulting 3D-N-doped AG offers excellent electronic conductivity(2.69×103 S·m-1), specific surface area(1258 m2·g-1) and well-defined 3D hierarchical porous structure.Au NPs were adsorbed on the surface of the 3D-N-doped AG. The resulting 3D-N-doped AG/GNs offers apparent heterogeneous electron transfer rate constant(40.78 ± 0.15 cm·s-1), which are notably better than that of previous graphene aerogel materials. Moreover, the 3D-N-doped AG/GNs was used as a new sensing material for the electrochemical detection of hydroquinone(HQ) and o-dihydroxybenzene(DHB). Owing to the greatly enhanced electron transfer and mass transport, the sensor displays ultrasensitive electrochemical response to HQ and DHB. Its differential pulse voltammetric peak current linearly increases with the increase of HQ and DHB in the range of 5×10-8 mol·L-1 to 1.8×10-4 mol·L-1for HQ and 1×10-8 mol·L-1 to 2×10-4 mol·L-1 for DHB. The detection limit is 1.5×10-8 mol·L-1for HQ and 3.3×10-9 mol·L-1 for DHB(S/N = 3). This method provides the advantage of sensitivity, repeatability and stability compared with other HQ and DHB sensors. The sensor has been successfully applied to detection of HQ and DHB in real water samples with the spiked recovery in the range of 96.8~103.2%. The study also provides a promising approach for the fabrication of various graphene aerogel materials with improved electrochemical performances, which can be potentially applied in biosensors, electrocatalysis, and energy storage/conversion devices.The 3D-ordered nitrogen-doped activated graphene/gold composite was successfully synthesized through freeze casting of 3D nitrogen-doped activated graphene which was obtained by previous method in our research. An ordered 3D hollow structure was distinctly founded in the material, and Au NPs were dispersed on the surface of graphene uniformly. The composite not only demonstrated excellent biological compatibility but also outstanding mass transferring rate, for which it was the most appropriate candidate to construct the hydrogen peroxide biosensor. The oxidation peak intensity linearly increased with increasing concertrtion of hydrogen peroxide in the range of 5×10-8 ~ 1×10-4 mol·L-1 with a detection limit of 8.2×10-9 mol·L-1(S/N=3). Proposed method presents remarkable improvement of sensitivity, repeatability and stability when compared to present sensors. The sensor has been successfully applied to detection of hydrogen peroxide in real samples with the spiked recovery in the range of 96.1%~103.9%.