Investigation On Electrochemiluminescence Signal Enhancement Strategies And Its Application For Flexible Sensors

With the development of nano-science,flexible electronics and micro/nano-fabrication technologies,flexible and wearable sensors have been widely applied in human health,environmental monitoring,energy storage and biosensing fields due to their high flexibility,portability and adaptability to non-planar special environment.Following many physical wearable devices fabricated for sensing vital signs(e.g.,heart rate,body temperature and blood pressure),flexible chemical sensors gradually arouse widespread concern for dynamically evaluation of the wearers'wellness at a molecular level.Thereinto,wearable electrochemical(EC)sensors fruitfully endeavors to detect the specific chemical constituents.On one side,recent research activity has aimed at mechanotransduction detection by developing stretchable EC sensors to monitor chemical messengers released from mechanical deformation of cells and tissues.On the other side,wearable EC sensors hold considerable promise in non-invasively retrieving health metrics by reliable detection of metabolites in bio-fluids,such as tears,saliva,and sweat.Despite that,the current flexible EC sensors have to employ enzyme or enzyme-like catalytic system for non-electroactive biomarkers detection,resulting in some shortcomings such as,low stability,cumbersome modifications or unsatisfied sensitivity on ultratrace analysis.Electrochemiluminescence(ECL)is an analytical technique combining electrochemical and chemiluminescence.Due to its free background,accurate control and high sensitivity,ECL method is widely applied for food safety,clinical diagnosis and human health monitoring.For a given ECL system,diversified strategies such as coreactant,resonance energy transfer(RET)or localized surface plasmon resonance effect can significantly enhance the ECL signal.Especially,comparing with EC sensors,ECL sensors exhibit excellent sensitivity for non-electroactive target molecule while eliminating the possible interference from the electro-active compounds.In this regard,it can be predicted that flexible ECL devices have great potential in wearable technology innovation.However,despite the progress in fabrication of flexible electroluminescent devices for wearable lighting,designing and fabricating wearable ECL sensors capable of retrieving physiologically relevant information has not been reported.Based on this,this thesis mainly targets to develop efficient ECL-enhanced system using composite nano-materials with high ECL efficiency and then construct flexible ECL sensor for real-time monitoring of metabolites in human sweat.The detailed work of this thesis is summarized as follows:1.The ECL intensity can be significantly improved by the overlapping spectra of donor emission and acceptor absorption.The RET efficiency depends on the distance of donor to acceptor.When the donor or acceptor is separately dispersed in the solution medium,RET could be greatly impeded.To solve this problem,we encapsulated plenty of[Ru(bpy)₃]²⁺and CdTe QDs inside a single nanosphere.This design greatly shortens the electron-transfer path and increases the RET probability,therefore significantly enhancing the luminous efficiency.Combined with molecular imprinting technique,a molecularly imprinted ECL sensor was constructed for ochratoxin A detection with extremely low detection limits of sub-fg/m L.This strategy represents a versatile ECL platform toward ultrasensitive and highly selective detection of diverse target molecules.2.Electrochemiluminesence(ECL)intensity of a given ECL system strongly relies on the quantity and availability of luminophores on the electrode.Generally,the compact deposition of luminescent nanomaterials on electrodes usually causes problems such as poor permeability of the co-reactant solution and low mass transfer rate,resulting in weak ECL signal.In view of this problem,a novel kind of luminescent materials denoted as C-Au-luminol nanospheres(C-Au-Lum NSs)were facilely prepared by in situ reduction of chloroauric acid with luminescent reagent luminol(Lum)on the nano-pores of porous carbon nanospheres(PCNSs).Au-Lum NPs are highly dispersed and concentrated inside the numerous pores of PCNSs,improving the mass transfer of H₂O₂ coreactant and accelerates the electron transfer rate and endowing the composite C-Au-Lum NSs with excellent ECL emission.Combined with the double amplification strategy of enzyme-assisted target cycle and strand displacement in aptamer-based technologies,biosensors was constructed for specifically detection of tumor marker mucin 1 with a low detection limit of 46.7 fg/m L.This design provides new ideas for preparation of high performance ECL nanomaterials.3.ECL method has great potential for monitoring the molecular information in living organisms due to its high sensitivity and resistance to electroactive substances,but it has rarely been reported.Based on this,we designed and fabricated a flexible ECL sensor by immobilizing highly luminescent Ru-PEI@SiO₂ nanospheres on gold nanotubes(Au NTs)network with a large aspect ratio,subsequent coating an elastic molecularly imprinting polymer(MIP)thereon.As prepared flexible ECL platform possessed successive and desirable mechanical compliance while granting very stable ECL signal during deformation.This successfully allows on-body sampling and subsequent detection of lactate and urea levels in sweat from different parts of the body.The study incorporates the ECL sensing models into flexible wearable devices,broadening the detection models and targets of flexible sensors.