Heavy Metal Ion Detection Technology Based On Carbon Quantum Dots Optics

Excessive heavy metal ions will cause irreversible toxic damage to organisms through the enrichment of the food chain,which is a long-term potential environmental pollutant.Therefore,accurate and effective measurement of metal ion concentration is of great significance.Carbon Quantum Dots(CQDs)have good environmental friendliness and excellent optical properties,and are becoming the key nanomaterials in the design of metal ion detection devices,showing great potential in the application of metal ion sensing and optical devices.As a result,it has attracted the attention of many researchers since it was first discovered in 2004.Starting from the optical properties of carbon quantum dots,this paper explores the influence of different kinds of metal ions and different concentrations of metal ions on the optical properties of carbon quantum dots,and detects the concentration of metal ions through the changes in the optical properties of carbon quantum dots.The main research contents of this paper are as follows:Firstly,this paper systematically explains the currently accepted photoluminescence mechanism of carbon quantum dots,including size effect photoluminescence mechanism,surface state photoluminescence mechanism,molecular state photoluminescence mechanism and carbon core state photoluminescence mechanism,and introduces two kinds of synthesis strategies of carbon quantum dots in recent years: From top to bottom and from bottom to top,it also shows the main application fields of carbon quantum dots,including ion detection,anti-counterfeiting,biological imaging,food safety,sensors,lubricants,etc.In this paper,a low-cost and efficient hydrothermal/solvothermal method is selected for the synthesis of carbon quantum dots,and the main application field is focused on the detection of metal ions.Considering that the preparation cycle of carbon quantum dots is several hours long and the volume of carbon quantum dots solution extracted from each synthesis is limited,digital microfluidic technology is introduced in this paper,which can effectively reduce the reagent consumption of carbon quantum dots and improve the degree of automation and fusion speed.Secondly,the driving principle of carbon quantum dots on digital microfluidic chips is analyzed in detail in this paper,including the principle of surface wetting,surface tension and its regulation,the basic theoretical description of dielectric wetting,contact angle saturation and basic droplet operation,so as to provide theoretical support for the movement and fusion of carbon quantum dots on digital microfluidic chips.Thirdly,in order to directly measure the influence of metal ions on the optical properties of carbon quantum dots in deionized water environment,two aspects were explained: fluorescence intensity detection analysis and absorbance detection analysis.In the analysis of fluorescence intensity detection,it was found that the presence of metal ions would weaken the effective fluorescence peak of carbon quantum dots,and the degree of weakening effect was slightly different.However,the fluorescence peak of carbon quantum dots gradually decreased with the increase of the concentration of metal ions.The change of the concentration of metal ions in a certain range will lead to a greater change in the fluorescence peak of carbon quantum dots.However,in the analysis of absorbance detection,it is found that the presence of metal ions can enhance the absorbance of carbon quantum dots,and the degree of enhancement is slightly different.However,the absorbance peak of carbon quantum dots increases with the increase of metal ion concentration.It shows that the fluorescence intensity and absorbance of carbon quantum dots can be used as effective means to detect metal ions.Finally,in order to further broaden the application scenarios of carbon quantum dots,the effects of metal ions on the optical properties of carbon quantum dots were tested in artificial saliva environment.It is found that carbon quantum dots still have the function and sensitivity to detect metal ions in artificial saliva environment,which also provides the possibility for human oral health ion detection.After verifying the metal ion detection ability of carbon quantum dots,this paper combined with the dielectric wetting theory of digital microfluidic technology,and simulated the macroscopic movement of carbon quantum dot droplets with the help of COMSOL simulation software,explored the driving effect of different voltage and electrode gap on carbon quantum dot droplets,and solved the optimal solution.And a digital microfluidic chip is prepared to realize the rapid movement and fusion of carbon quantum dot droplets.