Preparation Of Graphene Oxide Multilayer Quantum Dot Nanofilms And Their Application In Immunochromatography

In recent years,the outbreak of a novel coronavirus(SARS-Co V-2)has caused significant health risks and economic losses worldwide.Global pandemics have created an unprecedented demand for rapid,sensitive and inexpensive instant diagnostic tests.Currently,rapid tests have been rapidly developed in areas such as food safety analysis,environmental monitoring and clinical diagnostics.Lateral flow immunoassay(LFA)is a well-established point of care testing(POCT)method that has been widely used for the detection of small molecules and biomolecules(including tumour markers,viruses,fungal toxins,antibiotics and pesticide residues).However,a conventional LFA method based on a colourimetric signal has obvious disadvantages such as low sensitivity,limited quantitative capability and poor stability in complex samples for the detection of the target analyte.Therefore,this study have developed novel membrane-like fluorescent nanotags and introduced them into the LFA system.The extremely high quantum dot(QD)loading and thin-film structure of the membrane-like fluorescent nanotags can produce a dual signal amplification effect,thereby greatly improving the sensitivity of the LFA method.On this basis,three novel fluorescent LFA methods based on fluorescent nanomembranes were developed for the detection of a variety of target analytes.The main results are as follows:1.GO nanofilms containing double-layer quantum dot shells(GO@DQD)and GO nanofilms containing triple-layer quantum dot shells(GO@TQD)were successfully prepared by PEI-mediated self-assembly of multilayer quantum dot shells on GO nanofilms in sequence.The luminescence of the composite was greatly enhanced due to the large amount of QD aggregated on the GO nanofilm.In addition,both fluorescent nanofilms showed good stability and dispersion in complex solutions.2.We prepared a novel GO@DQD-based fluorescence LFA method.The method enabled highly sensitive quantification of S.typhi in food samples within 14 min and has a sensitivity as low as 9 cells/m L.The method was approximately 1000 and 100 times more sensitive than the colorimetric-based LFA and QD microsphere-based fluorescent LFA methods,respectively.The system also demonstrated excellent accuracy and stability in food samples(meat,egg and cabbage extracts).3.We proposed a GO@TQD-based fluorescence LFA method for the simultaneous and highly sensitive detection of three respiratory viruses(SARS-Co V-2/H1N1/HAd V).The method can analyse SARS-Co V-2,H1N1 and HAd V in saliva samples within 15 min with LOD of 8 pg/m L,488 copies/m L and 471 copies/m L respectively.It was 100 times and12.5 times more sensitive than the conventional Au NP-LFA and ELISA methods respectively.4.We developed a competitive fluorescence LFA method based on GO@TQD for the highly sensitive quantitative detection of three types of small molecule contaminants(AFB1/CLEN/KAN).The method can detect AFB1,CLEN and KAN rapidly within 15 min and the detection limits were as low as 0.87,2.04 and 0.81 pg/m L,respectively.In addition,our proposed method maintained excellent detection results in complex environmental and food samples.