Research On Self-enhanced Electrochemiluminescence Aptasensing Of Hg²⁺in Water

Water is the source of life that closely related to people’s life.With the rapid development of industry and agriculture,the use of heavy metals as raw material is becoming more and more extensive.Due to the substandard treatment of various types of waste water,the accumulation of heavy metals discharged into water has deepened,resulting in great ecological pollution.Among them,mercury（Hg）is one of the most toxic heavy metals in the environment.Bivalent mercury(Hg²⁺)is an important factor affecting the water safety due to their fast transfer,strong stability,and easy accumulation in the body.In response to the problem of low luminous efficiency in traditional electrochemiluminescence（ECL）,a new type of self-enhanced electrochemicalluminescence（ECL）material was prepared using nitrogen-doped graphene quantum dots（NGQDs）as co-reactant of Ru（bpy）₃²⁺in this paper.At the same time,Hg²⁺aptamer was introduced to improve the selectivity.Two kinds of novel self-enhanced ECL aptasensors were constructed to perform sensitive and selective analysis of Hg²⁺in tap and canal water.The main work contents can be divided into the following two parts:（1）Ru（bpy）₃²⁺-doped silica nanoparticles（Ru@SiO₂）was firstly prepared by the inverse microemulsion method,and then the aminated Ru@SiO₂（NH₂-Ru@SiO₂）and NGQDs were combined together to prepare a novel self-enhanced ECL material（NH₂-Ru@SiO₂-NGQDs）.Secondly,the amino-modified Hg²⁺aptamer combined with NH₂-Ru@SiO₂-NGQDs through amide reaction to form composite（NH₂-Ru@SiO₂-NGQDs-apt）that integrated the signal emitter and the specific recognition element together.On this basis,a new type of self-enhanced ECL aptasensor was constructed.When Hg²⁺was added,a stem-ring structure of T-Hg²⁺-T was formed which made the luminescent material close to the electrode surface and the ECL signal was increased.Under the optimal conditions,the prepared ECL aptasensor performed sensitive and specific detection of Hg²⁺.The linear range was between 5.00×10^-11 M and 1.00×10^-6 M with the detection limit was 1.00×10^-12 M（S/N=3）.Finally,the aptaseneor was successfully used for the detection of Hg²⁺in tap and canal water,which provided a new strategy for the detection of Hg²⁺in the ecological environment by ECL sensing technology.（2）In order to further improve the sensitivity and expand the linear range,a new type of self-enhanced aptasensor based on resonance energy transfer（RET）was constructed.The luminescent material（NH₂-Ru@SiO₂-NGQDs-DNA）was prepared through the reaction between NH₂-Ru@SiO₂-NGQDs and the single-stranded DNA modified with amino,and acted as ECL-RET electron donor.Gold nanoparticles（AuNPs）was synthesized by oil bath reflux method and combined with Hg²⁺aptamer through gold-sulfur bond to form apt-AuNPs,which acted as ECL-RET electron acceptor.ECL-RET occured when apt and DNA were paired through base complementation to form a double helix structure.At the meanwhile,the ECL signal decreased because that AuNPs was close to the ECL luminescent material.However,the ECL-RET was blocked and the ECL signal was restored due to the formation of T-Hg²⁺-T structure when Hg²⁺was present.The detection of Hg²⁺by this ECL aptasensor had more wider linear range than the previous work.According to the optimization results of experimental conditions,the linear range for Hg²⁺detection was 1.00×10^-14-1.00×10^-6 M with the detection limit of 3.30×10^-15 M（S/N=3）.The constructed ECL aptasensor was used to detect the Hg²⁺in different water samples,the recovery was between 93.3%and 101%,and the relative standard deviation was from 0.13%to 1.33%.