Nitrogen-doped Porous 3D Graphene Aerogel Composites Preparation And Their Application In Electrochemical Sensors

Graphene?GR?has been aroused significant attention since discovered in 2004and has been used in the electronic devices,catalytic processes,and other fields because of its excellent electric and mechanical properties.GR is a 2D nanosheets of the sp²-hybridized carbon atom.In order to overcome GR shortcomings such as the irreversible stacking between GR layers because of the strong?-?bonding and van der Waals forces,several functional modifications on GR such as preparation of three-dimensional?3D?porous graphene aerogel have been achieved.Graphene aerogel?GA?which known as ultra-low-density porous graphene formed by carefully replacing the liquid in the pores of the wet gel with air.GA has many exceptional properties such as a low density,high porosity,large specific surface area,excellent electrical conductivity,very fast charged carrier mobility,low cost,low dielectric constant and refractive index.Therefore,it can be employed in the electrochemical field as electrode materials for electrochemical devices such as sensors or biosensors.For the purpose of making GA suitable for several applications,some functional modifications have been achieved on its structure by introducing pores and heteroatoms doping.Porous GA?PGA?is a GA sheet with some pores/holes within the atomic plane.It is a modified GA sheet where the absence of carbon atoms within the plane creates some holes/pores.The presence of pores in GA acts to increase the specific surface area,and alleviation of the Van Der Waals interactions between the inter-sheets,thus reduces the stacking of GR nanosheets layers and provides more surface active sites for catalysts and also favors ion transport.On the other hand,the doping by heteroatoms?e.g.N,B,P,and S?could change the electronic properties of PGA and produce additional functional groups on the GR surface,leading to enhance the electrochemical performance and electron transport efficiency of PGA.Furthermore,in order to improve properties and increase the activity of N-doped PGA?NPGA?,the nanoparticles?NPs?like noble metals were deposited.This strategy has been attracted a lot of attention and achieved valuable results.Based on the previous studies,we have prepared and studied the electrochemical properties of nitrogen-doped porous 3D graphene aerogel?3D-NPGA?and Au Pd/NPGA and then used them as sensors to determine Gallic acid?GAL?and H₂O₂,respectively.In chapter two,we have determined GAL via the electrochemical technique by the prepared 3D-NPGA as sensors via a facile and effective approach via hydrothermal reduction.The NPGA composite showed a 3D pore structure with a large specific surface area and highly exposed active sites.The fabricated NPGA electrode showed an excellent electrocatalytic performance towards GAL oxidation compared to the previous studies with regard to the limit of detection?0.067?M?and linear range?2.5-1000?M?.The NPGA electrode provides a new way for GAL determination with high selectivity,excellent stability,and good reproducibility.In addition,it is highly suitable for the detection of GAL concentration in real samples with excellent reliability.In chapter three,the electrochemical properties of Au Pd/NPGA with the atomic ratio?1:1?of?Au:Pd?was prepared and use as nonenzymatic detection of H₂O₂.The nonenzymatic H₂O₂ sensor exhibited low LOD?0.038?M?,wide linear range?1-1000?M?,high sensitivity(12235?A mM^-1 cm^-2),quick response?t<1s?,excellent reproducibility,good selectivity,and excellent long-term stability as well as it can be employed to determine H₂O₂ in the human serum samples.