Quantitative Detection Of Molecular Based On Laser Back-scattering Interferometry

In recent years,water pollution,unsafe food,disease and other issues have become serious threats to human health.The conventional atomic absorption spectrometry and other quantitative detection methods exhibit the characteristics of high accuracy and high sensitivity,but with the disadvantages of large volume,high cost and complicated operation.So it is very important to develop a biochemical detection method with low cost and high sensitivity,and it has become one of the research hotspots.Back-scattering interferometry(BSI)technique with the properties of free label,small sample volume needed,low detection limit and high sensitivity,is expected to be used in food detection,environmental monitoring,clinical diagnosis and biochemical analysis.When light of laser incident into the capillary contained the material to be tested,interference fringes generated around the tube axis,due to the interference among the lights reflected and refracted from the inside and outside interface of the capillary,which is named as “Back-scattering interferometry”.When the refractive index of the liquid in the tube changes,the interference fringe pattern does not change,but it will show a movement with respect to the initial interference fringes,according to the relationship between the values of movement and refractive index changes,refractive index changes,antigen-antibody and other intermolecular interaction can be measured.In this thesis,a high sensitivity quantitative analysis and detection system are built based on BSI,combining the temperature control and fast Fourier transform,and the quantitative detection of micro-volume non-absorptive material with high sensitivity is realized.The laser can produce a photothermal effect and cause a change in the refractive index of the solution,so the system can also be used for highly sensitive quantitative detection of micro-volume light-absorbing analyte.The main contents of this thesis are as follows:1.The temperature control system and the insulation device were used to control of the temperature of the environment in which the sample is to be tested,so as to ensure the temperature of the sample can not be affected by the fluctuation of the ambient temperature during the experiment process.The temperature fluctuation is only ±0.007 ? during the experiment,and the resolution of the detection and the stability of the system were improved,the real-time data collection and automated processing were carried out by using LabVIEW.2.The detection sensitivity of the detection system for the non-absorptive analyte was verified by the detection of glycerol solution of different concentrations and ultrapure water at different temperatures.Based on the photothermal effect,the photothermal signals of magenta ink solution with different concentrations were measured,which show that this detection system could be used to quantitatively detect the light-absorbing material.3.Excess nitrite is very harmful to human health,so it is of great significance to quantitatively detect nitrite.The nitrite can be transformed into purple compounds through modified Grice diazotization reaction,the compound absorb green laser and then induce significant photothermal effect.Using the laser with the wavelength of 532 nm as the excitation light source,the concentration of nitrite was measured by the photothermal effect and the BSI technique.The nitrite in the tap water and spiked water samples were tested by photothermal effect and the BSI technique,and were compared with UV-vis method,The 3? detection limits can reach to 0.05 mg / L.