Study On Electrochemiluminescence Of TiO₂ Nanomaterials And Their Analytical Applications

Electrochemiluminescence(ECL)exhibits the merits of both luminescence and electrochemistry analysis,and has been extensively employed in biosensors.Semiconductor nanocrystals(S-NCs)become one of the three main kinds of electrochemiluminescence luminophores due to their unique properties.ECL studies concerning S-NCs have attracted great attention for their unique electronic and optical properties,particularly ?-? S-NCs containing CdS,CdSe,and CdTe.One hurdle in these studies is that these cadmium chalcogenide materials for extensive application in biological systems are related to the toxicity of Cd2+ that resulted from the decomposition of the cadmium compounds,which are extremely toxic.And TiO2 nanomaterial is less toxic and more environmentally safe than cadmium chalcogenide materials.Due to its uniquely physical and chemical properties,such as high surface area,optical transparency,good biocompatibility,relatively good conductivity and the physiochemical inclination to selectively combine with some groups of molecules,it is now become an attractive material widely used in photocatalysis,watersplitting,dye-sensitized solar cells,photoelectrochemical sensors.In contrast to the broad application in photochemistry,the studies of TiO2 NPs in ECL are not energetic.The main issues are the low ECL intensity of TiO2 nanomaterials and the poor stability of the TiO2 nanomaterials film modified on electrodes.Many efforts have been made to obtain strong and stable emission from TiO2 nanomaterials.Thus,of particular interest and motivating the present work is finding the possibility of dopped TiO2 nanomaterials onto the ECL platform,with the aim to search for advanced ECL biosensing format.1.Amplified Quenching of Electrochemiluminescence from CdS Sensitized TiO2 Nanotubes by CdTe-Carbon Nanotube Composite for Detection of Prostate Protein Antigen in SerumThis work reports an ECL immunoassay method for ultrasensitive detection of prostate protein antigen(PSA)on remarkably efficient energy-transfer induced ECL quenching from the CdS nanoparticles(NPs)sensitized TiO2 nanotube array(CdS/TiO2 NTs)to the activated CdTe NPs functionalized multi-wall carbon nanotubes(CdTe/MWNTs)composite.The coupling of TiO2 and CdS NPs results in 14.7 folds cathodic ECL intensity stronger than that of pure TiO2 NTs electrode,which could be quenched by the CdTe/MWNTs efficiently.The enhanced mechanism of TiO2 NTs ECL by CdS NPs was studied by cyclic voltammetry and ECL spectroscopy in detail.The strong absorption of the CdTe/MWNTs in the wavelength range of 400?800 nm makes them to be highly efficient ECL quencher labeled on anti-PSA antibody.Based on a sandwich structure,we provided an ECL immunoassay method for the sensitive and selective detection of PSA.The ECL intensity decrement was logarithmically related to the concentration of the PSA in the range from 1.0 fg mL-1 to 10 pg mL-1 with a detection limit of 1 fg mL-1.Human serum samples were then tested using the proposed immunoassay with excellent correlations,suggesting that the proposed immunoassay method is of great promise in clinical screening of cancer biomarkers.2.A Novel DNA Aptasensor for the Detection of Adenosine Triphosphate in Cancer Cells by Electrochemiluminescence of Nitrogen Doped TiO2 NanotubesThe highly enhanced ECL intensity from nitrogen doped TiO2 NTs elelctrodes has been reported for the first time,compared with pure TiO2 NTs elelctrode,the TiO2-N NTs electrode can enhance the ECL intensity by 10.6-fold and move the onset ECL potential more positively for about 400 mV,and the ECL emission is highly stable and repeatable.To exploit the application of TiO2-N as an efficient ECL emitter in DNA-related analysis,an aptamer-based target assay was developed using adenosine triphosphate(ATP)as a model.CdTe/MNPs which functioned as ECL quenching labels were assembled onto the TiO2-N NTs surface by hybridization between aptamers and their complementary DNAs(ssDNA);when the electrode was incubated in ATP solution,the aptamer in the dsDNA on the electrode surface competitively combined with ATP to form aptamer-ATP bioaffinity complexes.The CdTe/MNPs were removed from the electrode surface.The ECL signal of the aptasensor was responsive to the amount of CdTe/MNPs bound to the dsDNA oligonucleotides,which was inversely proportional to the combined target analyte ATP.The present sensor has an extremely sensitive response to ATP in a linear range of 10 nM?1.0 mM with a detection limit of 10 nM.Sample assays of adenosine in K562 leukemia cells confirm the reliability and practicality of the protocol,which reveal a good prospect of this platform for biological sample analysis.3.Novel electrochemiluminescence of Ru(bpy)32+/TiO2 nanotube arrays electrode and its application for detecting amines in waterIn this work,the cu(bpy)32+ was effectively immobilized on the surface of TiO2 NTs by electrostatic interaction to produce a Ru(bpy)32+ modified TiO2 NTs elelctrode(Ru(bpy)32+/TiO2NTs).A novel ECL was generated on the Ru(bpy)32+/TiO2 NTs electrode at-0.40 V vs.SCE when the tripropylamine(TPA)as co-reagent.The Ru(bpy)32+/TiO2NTs electrode exhibits excellent ECL behavior,very good stability and high sensitivity.The prepared Ru(bpy)32+/TiO2 NTs electrode was used to detect the changes of concentrations of pollutant nelaminein water.The present sensor has an extremely sensitive response to melamine in a linear range of 1×10-11 M?5.0×10-11 M with a detection limit of 1×10-11,M.This study may provide new insight into the design and preparation of an advanced solid-state ECL sensor for monitoring of amines in water.4.Enhanced Electrochemiluminescence of TiO2 Nanoparticles Modified Electrode by Nafion Film and its Application in Selective Detection of DopamineIn this work,a simple and effective approach to obtain stable,nontoxic and strong ECL interfaces is provided by coating Nafion on TiO2 nanoparticles(NPs)modified glassy carbon electrode(GCE)surfaces.Unlike a decrease in the current resulting from the blocked diffusion usually displayed in electrochemical process by Nafion coating,Nafion/TiO2 NPs modified electrode not only shows a highly stable ECL,but also shows an increment of ECL intensity for 8-fold and a reduction of overpotential for ca.300 mV in the presence of K2S2O8 as coreactant,compared with those of naked TiO2 NPs modified electrodes.The roles of Nafion coating on TiO2 NPs in the ECL process are proposed to be twofold:to provide refuge for the free radicals and to enhance the electron-hole recombination.Benifiting from its excellent ECL performance,the cationic exchange function of Nafion and the susceptible to being oxidized performance of dopamine(DA)by holes,the Nafion/TiO2 composite electrode could be used to sensitively and selectively detect DA with detection limit of 1.0×10-11 M,linear range of 1.0×10-11?6.0×10-7 M.The coexisted anionic species such as excess ascorbic acid shows little interference on DA detection.