Preparation And Application Of 3D Graphene Network/Nano-Materials Biosensors

Booming with the development of biology and medicine, biosensing is research direction full of opportunities. To meet the requirements of the next generation of medical diagnoses and environmental detections, there still exist some challenges and problems within this field. This article is to preliminarily address three key issues:(1) We designed and synthesized a 3D biosensor, which are favourable for biological adherence and can mimick in vivo environment. When the in vitro researches of biosensing begin to mimic in vivo conditions, some certain three-dimensional (3D) structures of the biosensors are needed to accommodate biomolecules, bacteria or even cells to resemble the in vivo 3D environment. To meet this end, a novel method of synthesizing cuo nanoflowers on the 3D graphene foam (GF) was first demonstrated. The 3DGF/cuo nanoflowers composite was used as a monolithic free-standing 3D biosensor for electrochemical detection of ascorbic acid (AA). The synergetic combination of 3DGF/CuO endows this biosensor with outstanding sensing properties such as an ultrahigh sensitivity of 2.06 ma mm-1 cm-2 to AA and 3 s response time. It is expected that the unique hierarchical 3D structure of 3DGF/CuO composite would be used not only as a real-time biosensor to detect analytes, but also as the a smart 3D bioactive platform supporting and monitoring cells or bacteria living condition in the in vitro or even in vivo research.(2) The peroxidase-like activity of 3DGN@WOs was firstly found, solving the problems of separation and aggregation. It has been found that some nanomaterials possess intrinsic capability to catalyse the redox of H2O2 as peroxidase mimics. However, to most nanomaterials, once dispersed into the solution, the recycle of the peroxidase mimics is always a challenge. Worse still, those nanoparticles are more vulnerable to aggregation which as a result deteriorates their catalytic efficiency. To simplify the separation procedure and maximize the peroxidase-like activity, a structure of 3D network with high catalytic nanomaterials embedded would be favourable. For the first time we demonstrated the hydrothermal synthesized WO3 nanowires have the intrinsic peroxidase-like activity and the successful anchoring of WO3 on 3DGN solve the problems of seperation and aggregation.(3) Two complementary sensing methods were integrated into one device, which can detect multiple targets. In most practical detections or diagnoses, a fast and cheap qualitative test is often preferable before a more elaborate and quantitative test. Transforming the detection events into colour changes, colorimetric biosensing are fast responding, low-cost and readable to naked eyes. These advantages gain colorimetric sensors great popularity in qualitative self-help tests. However, the sensitivity and linearity of colorimetric sensors are still not competitive to electrochemical sensors which though, are often delicate, requiring the connection to signal analysis instruments. Until now, there is still no single device can combine the advantages of colorimetric and electrochemical sensors and integrate both techniques in one device. We synthesize a sensing platform which not only possesses a freestanding 3D structure, peroxidase-like activity and high electrochemical sensitivity, but also integrates the two complementary sensing methods:colorimetric and electrochemistry.