Study On Dimethylamine Sensor Based On Two Kinds Of Acid-base Indicator

Dimethylamine is a volatile,organic amine,which has been converted to strong carcinogenic substances.Trace amounts of dimethylamine in water can cause serious impact on the ecological environment and human health,while in the existing detection methods present various disadvantageous,such as complex pretreatment precedure,expensive testing equipment,or environmental pollution problems and other issues.It is very important to establish a rapid,accurate and inexpensive method for the detection and analysis of trace dimethylamine in water.In this paper,cresol red and bromothymol blue two kinds of acid and alkali indicator were used as the maternal chemical,They were fixed in the ethyl orthosilicate?TEOS?after the formation of three-dimensional network structure of the sol,the successful preparation of the two kinds of sensitive materials,and used as the core to develop four different sensitivity of the sensor components,then performed its basic research.The research results can provide a new idea for the detection of trace pollutants in water by using planar thin film type optical waveguide sensor.The established test system has the advantages of easy operation,on-line detection and low cost,and has certain application potential.The specific research contents and conclusions are as follows:?1?using bromothymol blue indicator?BTB?as the parent,ethyl orthosilicate?TEOS?as a support material.The effects of four factors?the volume ratio of ethyl orthosilicate to distilled water,the heating temperature,the volume of ethanol and the rotation speed of the separator?were investigated by orthogonal experiment.The optimum conditions were selected to prepare sensitive materials.A series of planar thin film type optical waveguide sensor elements were prepared by rotating spin coating method,and the performance of the sensing elements was tested.The results showed that the sensing element had relatively good selectivity to the dimethylamine aqueous solution.The response time and recovery time were 8 s and 17 s,respectively.The detection limit?S/N= 6.5?was 0.4 ?g/L.And the stability measurement of the sensing element after a month suggests the stability has declined.?2?Preparation of TiO₂ sol,the TiO₂ sol was immobilized on the surface of Sn-doped substrate by impregnation method.Then,the sensitive materials were fixed in the TiO₂ thin film by rotating spin coating method to construct high sensitive composite optical waveguide elements,and the sensing performance was studied at room temperature.The results showed that the sensing element had good stability,reversibility and repeatability to the dimethylamine aqueous solution.The response time and recovery time were 6 s and 21 s,respectively.The detection limit?S/N= 5.29?was 0.004 ?g/L,and parallel test,with the relative standard deviation RSD<3%,proved the test accuracy of the sensing element on the dimethylamine aqueous solution.Compared with the traditional method,the detection limit is increased by at least two orders of magnitude.Such sensors provide new ideas for the detection of trace substances in aqueous solution.?3?Select cresol red?CR?as the sensitive reagent,ethyl orthosilicate?TEOS?as the supporting material,The mass of CR and the volume of ethanol and the rotation speed of the separator were selected.The optimum conditions were used to prepare the sensitive materials,and characterized by FT-IR.The series of sensing elements were prepared by spin coating method,and the sensing performance was tested.The results showed that the sensing element had relatively good selectivity to dimethylamine aqueous solution.The response time and recovery time were 4 s and 18 s,respectively.The detection limit?S/N= 4.2?was 0.04 ?g/L.The stability of the sensing element was tested after four months,and the stability was good.These results shows the advantages of short response time and quick recovery.?4?to obtain high sensitivity,a composite optical waveguide technique was used by forming a high refractive index on the surface of a tin-doped glass optical waveguide element TiO₂ film and the CR indicator on the surface of the film.the test of the sensing performance shows that: the sensing element detection concentration was lower,and had good stability,reversibility and?S/N= 3.47?was 0.0008 ?g/L,and the relative standard deviation?RSD?was less than 3% in the parallel test,showing brilliant accuracy,and the sensitivity and response time were 5 s and 14 s,respectively.And the stability measurement of the sensing element after four months interval indicate that the stability is good.