Study On The Electrochemiluminescence Enhancement Mechanism And Application Of Semiconductor Nanomaterials

Electrochemiluminescence?ECL?has become a powerful analytical technique that combined the unique advantages of electrochemistry and chemiluminescence such as rapidity,high sensitivity,and simplified optical setup.Recently,semiconductor nanomaterials,as a new kind of ECL emitters,have been widely used in ECL biosensors and induced number of new detection theories and methods due to their various types,easy synthesis and controllable luminescence-electrocity properties.Compared with conventional molecule emitters,semiconductor nanomaterials usually suffer from weak ECL emissions.Our group has established several kinds of methods to improve ECL properities of semiconductor nanomaterials and has proposed various ECL biosensors based on resonance energy transfer.Here,we try to develop new ways to enhance ECL of semiconductor nanomaterials or fabricate innovative ECL system,which will be benefit for building sensitive biosensors.Therefore,this paper will focus too much on the studying the mechanism of related ECL system.1.General Strategy for Enhancing Electrochemiluminescence of SemiconductorNanomaterials by Hydrogen Peroxide and Potassium Persulfate as Dual-coreactantsSemiconductor nanomaterials usually suffer from weak electrogenerated chemiluminescence?ECL?emissions compared with conventional emitters like Ru?TPrA?2?.In this work,we proposed,for the first time,a very conveuient but effective way to greatly enhance ECL emission of semiconductor TiO2 nanotubes?NTs?by H2O2 and K2S2O8 as dual-coreactants,generating the strongest ECL emission with ca.6.3 and 107 times that of KZS2O8 or H2O2 as coreactant,respectively.Scanning electron microscopy?SEM?,X-ray diffraction?XRD?and electron paramagnetic resonance?EPR?spectra studies were carried out to investigate the ECL enhancement mechanism.The ECL enhancement of TiO2 NTs by KZS2O8-H2O2 system was supposed to originate from the coordination of H2O2 to TiO2 surface and the synergy effect between H2O2 and K2S2O8 in the ECL process.The coordination of H2O2 to surface of TiO2 could stabilize the electrogenerated coreactant-related radical OH·?hydroxyl radical?,which could obviously promote the amount of sulfate radical anion?SO4·-?near the electrode surface by inducing decomposition of K2S2O8 into SO4·-or inhibiting the consumption of SO4·-by its reaction with H2O.The holes?h+?released from SO4·-were injected into the valence band of TiO2,resulting more TiO2*+,which combined with the electrons coming from the conduction band with an enhanced light emission.Moreover,this enhancement effect was also applicable to ECL of CdS nanocrystals?NCs?film on glass carbon electrode?CdS NCs/GCE?,with ca.2.8 and 148.3 times enhanced ECL intensity correspondingly,indicating wide applications in the development of semiconductor nanocrystals-based ECL biosensors.2.In Situ Activation of Coupled Semiconductor by Filling ID TiO2 Nanotubes with thioglycolic acid-stabilized CdS nanocrystals and Its Application in H2O2 DetectionA coupled semiconductor material is prepared by filling one-dimensional?ID?TiO2 nanotubes NTs with thioglycolie acid?TGA?-stabilized CdS NCs.After in situ activation of the coupled semiconductor material in an activation solution containing HZOZ and citric acid,a greatly enhanced ECL emission is achieved in the presence of coreactant H2O2,resulting in?265-fold enhancement of ECL intensity as that of the original TiO2 NTs electrode.The reason of the strong ECL emission lies in three aspects:First,in ECL progress,the coupling of CdS NCs with a small band gap and TiO2 with a large band gap semiconductor material gives rise to an efficient and faster charge transfer from the conduction band of CdS NCs to that of TiO2,and efficient h+transfer from the valence band of TiO₂ NTs to that of CdS NCs,promoting the formation of TiO2*and CdS*;Second,the stabilizers-capped CdS NCs can not only effectively remove the nonradiative surface states and deep surface traps for enhanced ECL efficiency,but also be favorable for the electrochemical involved electron and hole injection processes;Third,a strong coordination of H2O2 to TiO2 NTs and surface S vacancies resulted from in situ activation,can stabilize the electrogenerated radicals HO',resulting in an enhanced ECL.Generally speaking,the activated CdS NCs/TiO2 NTs electrode is highly sensitive to H2O2.Based on this,an easy but sensitive ECL sensor for determining H2O2 without any signal amplification techniques was fabricated.At last,we evaluate the performance of this activated electrode by determining H2O2 released from HL-60 cancer cell.The satisfactory results indicated that this strategy is promising for developing ECL biosensors by using H2O2 in biological sample as coreactant.3.CdS Nanocrystal-based electlrochemiluminescence sensor for cancer cell detection with Au nanoparticles and isothermal circular double-assisted signal amplificationHere we have developed a sensitive cancer cell amplified detection method which combined Au NPs enhanced electrochemiluminescence?ECL?of CdS NCs film,with isothermal circular amplification reaction of polymerase.In DNA circular amplification detection system,hairpin DNA beacon/Au NPs composite modified CdS NCs film was used as ECL emitter.Messenger DNA is hybridized with the aptamer modified on magnetic beads?MBs?to form MB-Au bioconjugates.In the presence of HL-60 cell,the aptaner would conjugate with the glycoprotein at cell surface and messenger DNA sequence would be released.The released messenger DNA sequence was then introduced into the cycle amplification system to tigger circular polymerizations.This assay allows us to determine the released messenger DNA equivalent to 10 cells and exhibits a significant specificity for HL-60 cells.