Study On Materials For Surface Modification Of Silicon Resonant Micro/Nano Sensors For Heavy Metal Detection

With the rapid development of industry,environmental pollution problems have become more and more serious.Particularly,the accumulation of heavy metals in the water has become one of the most harmful water pollution problems.Heavy metals have characteristics of refractory degradation,high toxicity,and irreversible damage,which will be passed along the food chain step by step in the organism.Nowadays,most of the methods to detect heavy metal ions in water have disadvantages of low selectivity,non-real-time detection,etc.Therefore,the micro/nano electromechanical systems are applied to micro mass measurement to achieve high selectivity and real-time detection of heavy metal ions in water.In this paper,the micro/nano beam resonator was used as the core sensor element of the micro/nano electromechanical system.The mesoporous silicon was modified onto the micro/nano beam to achieve specific adsorption of cadmium and mercury ions in water.The micro/nano beam were drived by piezoelectric ceramics and the resonance frequency of the beam was measured by a laser Doppler vibration detector.Then,the mass of heavy metal ions adsorbed could be calculated by the shift of resonance frequency of the beam before and after the adsorption,thus realizing the function of real-time trace detection of heavy metal ions in water.The main research results are as follows:In this paper,the functionalized mesoporous silica balls were prepared by the improved soft template method and co-condensation reaction.In addition,the functionalized mesoporous silica balls has good uniformity in size and the diameters of which are in the range of 20-30nm.The specific surface areas of sulfhydryl-functionalized mesoporous silica and amino-functionalized mesoporous silica are as high as 926.0099m²/g and 851.1374 m²/g,respectively.In this paper,an energy spectrum analyzer was used to detect the adsorption of functionalized mesoporous silicon in mixed heavy metal ion solutions and the adsorption of gradient cadmium ion concentration solutions,verifying that the Sulfhydryl functionalized mesoporous silicon（MSS-30^b）has the ability of selective adsorption of heavy metal Cd²⁺,and its limit of detection has reached 0.8μg/L,which is lower than the maximum permissible concentration of Cd²⁺in water set by AQSIQ.In this paper,through the comparison experiment of mercury ion adsorption,it is concluded that amino-functionalized mesoporous silica and amino-containing nucleic acid aptamer mesoporous silica both could specifically adsorb mercury ions,but the amino-containing nucleic acid aptamer had a higher selective adsorption capacity for mercury ions.The micro-beams processed by the research group in the past have been used to realize the function of trace detection of mercury ions in water.In order to ensure the uniform distribution of mesoporous silicon on the micro/nano beams,the method of atomization was used to modify the amino-functionalized mesoporous silicon onto the beam.The mercury concentration of the mercury standard solution used in the adsorption experiment is 2μg/L.A laser Doppler vibrometer was used to measure the resonant frequency of the micron beam.The content of mercury ions adsorbed on the micron beam was calculated to be at the nanogram level by frequency shift.