Engineering Of Carbon Nitride Sensing Interface And Its Luminescent Applications

As a typical metal-free conjugated polymer,graphitic carbon nitride has been received increasing attention as a low-cost,stable materials in catalysis,photoelectric conversion,sensing and imaging,due to its appealing electronic band structure,unique chemical structure,excellent optical and electronic properties.In addition,its chemical structure and band structure are adjustable.However,the research on carbon nitride was mainly concentrated on improving the performance of photocatalytic and photoelectric conversion.Moreover,the understanding of the relationships between molecular structure and performance is still in infancy.Accordingly,the sensing and imaging applications of carbon nitride materials based on their photoluminescence(PL)and electrochemiluminescence(ECL)properties are still seriously limited by several factors,such as,synthesizing carbon nitride materials with high PL quantum yield,multi-colored PL emission or higher ECL activities,developing new and excellent coreactant ECL systems,and combining the excellent luminescent properties of carbon nitride materials with other biorecognition units for biosensing.In this dissertation,we explore interface control of carbon nitride for the design of novel sensing strategies,to further expand the sensing application of carbon nitride.The details are summarized briefly as follows:1.So far,several signal transduction pathways that rely on catalytic reactions,steric hindrance effects,resonance energy transfer,and charge transfer have inspired numerous biosensing studies.It leads to a more comprehensive understanding of each sensing mechanism.However,most previous biosensors are driven by a single sensing mechanism,and sensing systems regulated by competitive multiple mechanisms have rarely been reported.Nevertheless,signal transduction in vivo is often governed by a series of competitive multiple mechanisms.Carbon nitride were selected as the luminophor because of their biocompatibility and luminescent properties.We proposed the integration of a competitive catalytic reaction and steric hindrance effect into a single electrochemiluminescent(ECL)biosensor interface by assembling hemin/G-quadruplex on carbon nitride nanosheets(CNNS).As an example,8-OHdG was detected by the dualmechanism-driven biosensor with a much higher sensitivity and broarder calibration curve range compared with previous methods.2.According to the fundamental theory of ECL,multiple luminophores can be distinguished by the potential required for excitation or by the wavelength of emission.Therefore,wavelength-based ECL may hold great promise in the development of multivariate analysis.However,the construction of such a system is not yet popular.A high-resolution ECL spectrum acquisition system was then proposed by re-examination of coupling of the recent tabletop spectrofluorometer with much improved sensitivity and potentiostat.Notably,the proposed instruments can be realized even when only a modest budget and limited expertise are available.3.The limited number of biocompatible monochromatic ECL luminophors high performance,low cost,non-toxic and narrow spectral distribution is a bottleneck for ECL multiplex bioassay.The CNNS with different emission wavelengths were explored as metal-free monochromatic luminophores with premium properties.As there was no resonance energy transfer between them,we proposed a wavelength-resolved ECL biosensor for the simultaneous detection of multiple biomarkers at a single-electrode interface,with the same coreagent and excitation potential.The proposed ECL biosensor demonstrated good accuracy and high precision in the simultaneous detection of multiple PDAC biomarkers in spiked serum.This work would greatly pave the way for studies of less explored high-resolution wavelength-resolved ECL for multiplex bioassay with competitive performances.