| The discovery of graphene greatly promoted the study of two-dimensional?2D?materials with one or a few of atom layers.A new kind of 2D transition metal carbide or nitride?MXene?pioneered by Yury Gogotsi in 2011,attracted lots of attention,due to their good hydrophilicity,metallic conductivity(201?sq-1),rich composition and adjustable structure.And the MXene have already displayed potential applications in the fields of energy storage,electromagnetic shielding,sea water desalination and biotherapy.However,the sensing property of MXene remains a relatively unworked area.In this dissertation,the highly sensitive piezoresistance sensors are designed based on MXene with the uniform-size and structure-stable.By using the in-situ Transmission Electron Microscopy?TEM?,Scanning Electron Microscope?SEM?and so on,the morphology,structure and properties of the MXene-based sensor are systematically characterized and analyzed.The MXene-based sensor also demonstrates potential application in monitoring human movement and measuring pressure distribution.The main content of the thesis includes:?1?Optimizing the preparation technology of MXene:in 2011,Yury Gogotsi reported a method for fabricating accordion-like MXene by using high concentration hydrofluoric acid?HF?.On this basis,we systematically investigate the effect of the reaction temperature and HF concentration to improve the productivity and quality of the MXene during the process of synthesizing MXene.On the other hand,the single MXene nanosheet was obtained by intercalating dimethyl sulfoxide?DMSO?and then ultrasonic exfoliating,which was time-consuming and poisonous.Here,one-step method was used to synthesize single MXene nanosheet with the help of hydrochloric acid?HCl?and lithium fluoride?LiF?.The obtained MXene nanosheets uniformly disperse and have no impurities,which are easily combined with other materials.?2?A highly flexible and sensitive piezoresistive sensor based on MXene with greatly changed interlayer distances is designed.The MXene etched out by HF is firstly carried out by the treatment of Focus Ion Beam?FIB?electron microscopy,and then observed by in-situ TEM.It is found that under an external force the distances between the interlayers of MXene can be reduced,increasing the conductive path,in turn increasing the current.While the external force is removed,the interlayers of MXene reversibly recovered,as well as the current.After more than 100 loading–unloading cycles,the structure of MXene can still recover its original stage,which shows its good stability.With the help of the soft polyimide interdigital electrode,a highly flexible and sensitive piezoresistive sensor based on MXene with greatly changed interlayer distances is designed.The device also shows high sensitivity?Gauge Factor??180.1?,fast response?<30?ms?and extraordinarily reversible compressibility,which is helpful for MXene to develop other application.?3?A 3D piezoresistive sensor of synergistical MXene/Reduced graphene oxide?MXene/rGO?aerogel is elaborated.The 3D porous aerogel exhibits ultralight,superelastic and relatively stable properties,which is very suitable for pressure sensor.The high concentration MXene nanosheets synthesized by one-step solution method displays relatively small size,and are difficult to assemble stable 3D structure.And the pressure sensor based on graphene aerogel shows good stability,but low sensitivity,which hinders its future application.Here,a newly piezoresistance sensor based on the MXene/rGO aerogle is designed by firstly physically mixing MXene and GO solution,then vacuum freeze-drying and lastly low-temperature annealing.This composite material not only combines the good conductivity of MXene with the large nanosheet of GO,but has low-cost and large-scale technique.More importantly,the piezoresistive sensor based on MXene/rGO aerogel shows extremely high sensitivity(22.56(kPa-1)),fast response time?<200 ms?and good stability over 10,000 cycles.The piezoresistive sensor based on MX/rGO hybrid 3D aerogel can easily capture the signal below 10 Pa,thus clearly test the pulse of an adult at random.Based on its superior performance,it also demonstrates potential application in measuring pressure distribution,distinguishing subtle strain,monitoring healthy activity and so on. |
PDF Full Text Request