| The rise of the internet of things and artificial intelligence industries has put forward urgent requirements for the sensors(or the detection instruments)with low-power consumption and miniaturization.Optical or electrical method is usually adopted for trace analysis of liquid samples.Among them,spectrophotometer acting as a representative optical detection method,has the advantages of simple operation,low cost and fast analysis speed;Semiconductor biosensor acting as a representative electrical detection method,has the advantages of low power consumption and easy integration.For spectrophotometer,cuvettes are equipped as the sample pool generally,and its sensitivity mainly depends on the optical path length of the cuvettes.The width of cuvette times the refractive index of the liquid to be measured equals the optical path length of the cuvette.Due to the limit of the width of cuvette,the sensitivity of the spectrophotometer is restricted.Moreover,the deuterium lamp or tungsten lamp is usually adopted as the light source,and power consumption of the instrument is relatively high.For semiconductor biosensors,nanomaterials are usually adopted as sensitive materials.Semiconductor nanowires are the smallest conductive channels,and single nanowire can act as an independent device itself,which is of great significance for reducing size and power consumption of sensors.In addition,nanowires can be easily arranged to form nanowire device arrays,and the integration is high.However,nanowire biosensors have the disadvantages of poor stability and short service life.Based on the problems above,the portable metal waveguide capillary(MWC)photometer with high sensitivity and low power consumption has been developed in this paper.Besides,sensors based on InAs/InP core/shell nanowires have also been developed.The introduce of InP shell could delay the surface oxidation and enhance the stability of InAs nanowires(Due to the limited time,gas sensitive properties have been studied at present,and liquid detection work will be carried out in the future).The main achievements are as follows:1.The effect of optical path multiplier inside MWC is studied.The inner wall of the MWC can maintain high reflectivity in a very wide range of the incident angle,and there are micro shrinkages at both ends of the MWC.Therefore,the detection beam can be confined inside the MWC by multiple reflections.As a result,the optical path reaches 3.4 times of the physical length.2.The MWC photometer has been developed,in which cuvettes are replaced by MWC to improve sensitivity;LED has been adopted as the light source to reduce power consumption.When the physical length of MWC is 7 cm,the detection limit of trace glucose,diesel and heavy metal Cr(Ⅵ)in water is 5.12 nM,2.14 μg/L and 0.1 μg/L,respectively.Compared with Agilent Cary 300 spectrophotometer(equipped with two cuvettes of 1 cm),the detection limit of MWC photometer is improved by more than 125 times,125 times and 100 times,respectively.Besides,the size of MWC photometer(13×14×22 cm3)is smaller.3.The InAs/InP core/shell nanowire sensors have been developed,and the effects of InP shell on stability and sensitivity of the sensors are studied.The experimental results show that when the thickness of InP shell is more than 3.3 nm,the InP shell can slow down the surface oxidation of InAs nanowires effectively,which makes the InAs/InP nanowires maintain high sensitivity after being placed in air for 6 years;Moreover,the detection limit of InAs/InP nano wires for NO2 reaches 3 ppb,which is more than 300 times better than that for bare InAs nanowires.The improvement on sensitivity is attributed to the InAs/InP heterojunction barrier on the surface of the nanowires.This work lays a foundation for the follow-up research on nanowire biosensors. |
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