Synthesis Of Ratiometric Fluorescence Probe And Application In Detection Of Mercury Ion

Heavy metal ions are widely used in various fields,their pollution have become critical worldwide issues for recent years.Due to their strong toxicity and bioaccumulation,heavy metal ions cause harm to people and ecological environment.Therefore,it is important to develop a rapid method for monitoring heavy metal ions.The ratiometric fluorescence methods could eliminate the experiment error and improve the sensitivity of detection by calculating the ratio of fluorescence intensity at two different emission wavelengths.Meanwhile,the ratiometric fluorescence technique has visualization capability by displaying continuous color change,which has a certain development prospect.In this study,a facile ratiometric fluorescence nanoprobe based on carbon dots-gold nanoclusters（CDs-Au NCs）was constructed for quantitative detection of mercury ions.The research contents and results are as follows:1.Synthesis of ratiometric fluorescent probe components.Lysine functionalized carbon dots（Lys-CDs）were prepared by one-pot hydrothermal method,while gold nanoclusters（CEW-AuNCs）were synthesized via using chicken egg white（CEW）as reducing and stabilizing agent.The reaction conditions including pH,time and temperature were explored to determine the optimal synthesis conditions of the fluorescent materials.According to the results of high-resolution transmission electron microscopy,both fluorescent materials were mostly spherical,and the average diameters of Lys-CDs and CEW-AuNCs are 11 nm and 6nm,respectively.The optical properties of two fluorescent materials were studied by UV-vis spectroscopy and fluorescence spectroscopy,and the results indicated successful synthesis of Lys-CDs and CEW-AuNCs.2.Construction of a ratiometric fluorescent probe.CDs-AuNCs was prepared by simply mixing CDs and Au NCs together without the needs of cross-linking agent.The probe exhibited two strong emission peaks at 450 nm and 665 nm under 390nm excitation,and showed pink fluorescence under UV light.The probe was characterized by transmission electron microscopy,X-ray photoelectron spectroscopy,FT-IR spectroscopy and zeta potential.The result showed that good dispersion of the CDs-Au NCs system was obtained and there was no energy transfer between CDs and Au NCs,indicating the successful construction of CDs-AuNCs.3.Construction of ratiometric fluorescent sensor for mercury ions.The fluorescence of Au NCs at 665 nm was decreased when Hg²⁺was added to the solution,while the fluorescence of CDs at 450 nm stayed constant.This ratiometric fluorescent sensor could detect Hg²⁺accurately and possess a great sensitivity with a detection limit of 63 nM.In addition,this method had also been used to detect Hg²⁺in real samples（tap water and lake water）with great recoveries.In addition,CDs-AuNCs were immobilized on filter paper to prepare a fluorescent test strip which provided a possibility for on-site convenient detection of mercury ions,suggesting its potential application in practical with simplicity,environmentally friendly and low cost.