Study Of Paper-Based Sensing Technology Of Heavy Metal Ion Based On Inkjet Printing

Heavy metal ions pollution is a serious threat to human life,it is necessary to develop a rapid and accurate detection of heavy metal ions,so that human beings are away from heavy metal ions pollution as far as possible.Microfluidic paper-based analytical devices is a kind of analysis and detection technology with paper as base material.It has the advantages of low cost,simple operation,good portability and disposable use.It has attracted wide attention in life science,environmental analysis and medical health and has been widely used in the field of disease diagnosis,environmental monitoring and food quality control.The paper chip combines the advantages of traditional microfluidic chip(miniaturization,high throughput,highly integrated)and the unique advantages of paper(cheap,easy,biocompatible,no external power),its development has been from the exploration of the production method into the practical application.Colorimetric method,electrochemical method,chemiluminescence method,electrochemical luminescence method and fluorescence method have been applied in paper chip.It has the advantages of simple operation,fast detection,high sensitivity,good selectivity,miniaturization and easy operation.The paper combines the microfluidic analysis device and the ink jet printing method,as well as the traditional optical analysis method(colorimetric method and fluorescence method)is widely used in all aspects of analysis and testing.This paper presents two methods for the detection of cadmium and silver in solution and on paper-based detection,two methods for fluorescence detection of heavy metal ions cadmium and colorimetric detection of heavy metal ions silver.The main work is as follows:(1)In the south of China,cadmium rice caused by cadmium ions pollution produced great harm to people’s healthy life.We used 8-hydroxyquinoline and 2,6-bis(chloromethyl)pyridine to synthesis an organic small molecule dyes for the detection of cadmium ions.The organic small molecule dye itself has a weak fluorescence,however,they can occur complex reaction and lead to a strong fluorescence enhancement when the metal ions Cd2+ exist.By taking use of this signal changes,detection of metal ions Cd2+ achieved.It is found that metal ions Cd2+ and organic small molecules can react sensitively and selectively.In order to achieve the analysis and detection on the paper,we explored the suitable conditions for the reaction of organic small molecules and metal ions Cd2+ in solution,such as the pH value,and the complexing time.The appropriate pH range,viscosity and surface tension of ink were found for inkjet printing,and then the smart phone was used as a signal collection device to take photos of the fluorescence picture after the reaction,and the ImageJ software was used to treat the color of the picture to obtain the gray value.The relationship between the concentration of metal ions Cd2+ and gray value scale was finally analyzed.(2)In order to accurately detect the concentration of metal ions Ag+,we use 3,3’,5,5’-tetramethylbenzidine(TMB)as the substrate for the reaction.When the metal ions Ag+ are present,metal ion Ag+ can oxidize the TMB from the colorless to blue.Based on this principle,we got a good linear relationship,selectivity and sensitivity,and the more appropriate reaction conditions in the solution reaction,and then prepared a certain concentration TMB solution as printed ink,and printed in the pre-processed paper-based microfluidic channel.It is found that the test paper changed from colorless to blue after a period of reaction time.Finally use the smart phone as signal collection device,and ImageJ software was used obtain the gray value.According to the gray value,the metal ions Ag+ concentration was semi-quantitatively analyst.