Fabrication and Application of All-solid-state Potentiometric Sensors Based on Carbon and Gold Nanomaterial

Author:An Qing Bo

Supervisor:niu li


Degree Year:2019





Potentiometric chemical sensors are widely concerned for their advantages such as easy to miniaturization and operation,simple structure,convenient to carry and high selectivity to target ions.As one of the important branch of potentiometric chemical sensors,all-solid-state ion-selective electrodes have been widely used in many fields,such as environmental monitoring,water quality analysis,marine investigation,agriculture,food and drug analysis.At present,there have been studies on wireless wearable devices for real-time remote analysis and monitoring of human health condition.Their outstanding features are that non-invasive to human body,convenient and fast which improve the time and space efficiency in monitoring,also enable the pre-alarm system of human health.Therefore,preparation and study of high performance ion-selective electrodes have great scientific significance and social value.Based on this,a series of research work has been carried out in this paper,starting from the fabrication of all-solid-state ion sensors with high sensitivity and low detect limitaion and applicated in marine environmental monitoring and human health analysis.1.We used hollow carbon microspheres in the core-shell structure of zinc oxide as solid-state transducer for the first time.The carbon microspheres with uniform size and regular shape as precursors to prepare zinc oxide with carbon core by simple pretreatment and programmed heating.Three kinds of all-solid-state ion-selective electrodes were fabricated by using self-made glassy carbon electrodes as conductive substrate and polymer ion-selective membrane.The addition of hollow carbon microspheres in the core-shell structure of zinc oxide increased the electron transfer efficiency,as well as the ion-electron conversion efficiency.The characteristics of large specific surface area and large capacitance also stabilized the electrode potential.The ion-selective electrodes can detect K+,NH4+and NO3-ions in artificially simulated seawater with a response range of 1.0×10-1-1.0×10-6 M,which conformed to the requirements to seawater testing.Besides that,we simulated the deep-sea environment and tested the long-term stability of the electrodes.During the test period of seven weeks,the prepared electrodes showed Nernst linear response to the target ion,and had good stability.2.A method to improve the hydrophobicity of all-solid-state ion-selective electrodes has been proposed to solve the problem of water layer which existed between ion selective membrane and conductive substrate.Firstly,a fluoroalkyl trichlorosilane was modified on the surface of cellulose paper to make cellulose paper superhydrophobic.Then,high-quality graphene dispersion was sprayed on the hydrophobic paper surface as electrodes and solid-state transducer to prepare all-solid-state ion selective electrodes.Compared with chemically reduced graphene oxide,high-quality graphene peeled directly from graphite has better conductivity and hydrophobicity.As far as we know,this is the first time to improve the hydrophobicity of electrodes by chemically modified substrates.The synergistic effect of modified paper substrates and hydrophobic transducer material has greatly improved the influence of water layer on the stability of electrodes potential.3.A flexible and wearable multi-channel paper-based all-solid-state ion-selective electrode has been developed by using the above-mentioned methods.The real-time on-line analysis of various ions concentration in human sweat has been realized.The experimental results showed that the prepared multi-channel paper-based all-solid-state ion selective electrode can simultaneously analyze potassium ion,sodium ion,chloride ion and pH value of human sweat in situ.The results are consistent with those obtained by inductively coupled plasma-mass spectrometry(ICP-MS),which indicated that the multi-channel all-solid-state wearable ion selective electrode developed by us has good real-time on-line analysis ability and has expected to be applied in health detection and clinical analysis.4.In view of the hydrophobicity and capacitance of carbon-based conversion materials,we also developed a sp2 hybrid porous carbon nanosphere as an ideal ion to electron transducer material to prepare all-solid-state potassium ion selective electrode.Using conventional industrial raw materials such as dopamine and ammonia,carbon nanospheres with uniform particle size and porous were obtained by calcination at high temperature.Simple synthesis method is conducive to mass production.The static contact angle of carbon microsphere film to water reaches 1370,which was one order of magnitude higher than graphene,carbon nanotubes and other similar carbon materials.The detection limit of all solid-state K selective electrode based on carbon nanospheres is 1.0×10-6 M.And because of its good hydrophobicity,it has good long-term stability and eliminated water layer interference in the testing process.5.In addition to carbon-based materials with double-layer capacitance potential stabilization mechanism,we have developed a gold nanocluster material with pseudocapacitance stabilization mechanism.The gold nanoclusters have mixed valence,good conductivity and high pseudocapacitance.Due to the strong and hydrophobic surface modification of mercaptan,these unique properties make it possible to be used as an ion-electron transducer material.We prepared a single-piece all-solid-state potassium ion selective electrode by adding 2.0%hexathiol-modified gold nanoclusters into the K+selective membrane.The addition of hexathiol-modified gold nanoclusters can effectively improve the ion-electron conversion efficiency,reduce the response time,stabilize the electrode potential and decrease the detect limitation.In addition,because of the chemical stability of hexathiol-modified gold nanoclusters,the single piece all-solid-state potassium ion selective electrode has well anti-interference performance.