Research On Problems Related To Detection And Enrichment Methods Of Heavy Metal Ions Based On Nano-Electromechanical Systems

With the rapid development of industry,environment has deteriorated significantly,and has caused public concern.Heavy metal pollution is one of the most concerned pollution.Even a small amount of heavy metals will have serious impacts on human health due to its high toxicity.The monitoring of heavy metal ions in water requires rapidity and convenience.In recent years,micro/nano electromechanical systems have developed rapidly,and as typical sensor devices,micro/nano resonators have incomparable advantages in the detection of small physical quantities due to their excellent properties.Based on the review of research status of nano-electromechanical systems used for trace detection,micro/nano resonators are proposed for detection of heavy metals.In order to adsorb more heavy metal ions in water,silicon beam is deposited with a film of metal(Si-Metal beam)which is used for assembly with functional material.The main results are as follows:Molecular dynamics calculations is performed by using Materials Studio software to study the vibration characteristics of Si-Metal beams.It is found that the resonant frequency of SiMetal beam with structural optimization is reduced compared to the unoptimized,but trends of the beam frequency with length and thickness do not change.In addition,the frequency of SiMetal beam is reduced after silicon beam deposited with a film of metal.Two dimensions of micro/nano resonant beams are designed and successfully fabricated.In this thesis,the beam with thickness of 25 μm is called micron-scale beam and the beam with thickness of 200 nm is called submicron-scale beam.The micron-scale beam is excited by piezoelectric ceramics and its frequency is detected optically.The micro-mass is loaded on micro-scale beam by using 3D printing technology,and the frequency shift of the beam after loading is successfully detected.The prepared cantilever beam can obtain a sensitivity of 20.983 Hz/ng.The minimum mass which can be detected is 1.5 ng.The resonance of the submicronscale beam is successfully achieved by electrostatic driving.The measured resonance frequency value agrees well with the theoretical value.The mesoporous functionalized mesoporous silicon nanoparticles are selected as the modified materials of the composite beams.The modified materials are successfully prepared by template method,and can adsorb heavy metal ions.