Construction And Application Of Near-Infrared Electrochemiluminescence Sensor Based On Doped Quantum Dots

Quantum dots（QDs）,also known as fluorescent semiconductor nanomaterials,have attracted wide attention due to their unique and excellent optical properties.Near-infrared QDs（650-900 nm）have the advantages of strong penetration of biological tissues and low background signal interference,so it is a potential biosensor material.However,the current synthesis method of near-infrared QDs has complicated steps,long time periods,and contains highly toxic elements of mercury and lead.Therefore,the synthesis of near-infrared QDs with low toxicity and simple and rapid steps has important research significance.In recent years,doped QDs has been favored by researchers because of its unique optical and magnetic properties.More importantly,doping other elements in QDs can well tune the fluorescence emission window of QDs,which is one of the important methods to obtain near-infrared QDs.The electrochemiluminescence of near-infrared QDs combines near-infrared light and electrochemiluminescence,and has the advantages of low background interference and fast signal response,and has a good application prospect.In addition,it is also very important to enhance the electrochemiluminescence signal of near-infrared QDs in order to improve their sensitivity in analysis and detection.（1）Construction of the near-infrared electrochemiluminescence biosensor based on Cu-doped CdTequantum dotsIn this work,we constructed an anode near-infrared electrochemiluminescence immunosensor based on Cu-doped CdTeQDs for the first time.The Cu-doped CdTeQDs were synthesized by hydrothermal method.The fluorescence emission spectrum of Cu-doped CdTeQDs could reach the near-infrared region of 730 nm in a short reflux time.Compared with CdTeQDs,the fluorescence wavelength has an obvious red shift.More importantly,after Cu doping,the ECL strength of CdTeQDs was increased by more than 2 times.The results were attributed to the mixing of Cu d orbital with the conduction and valence bands of intrinsic CdTeQDs,which changed the original exciton recombination path.A near-infrared electrochemiluminescence biosensor was constructed by coupling Cu-doped CdTeQDs with tetracycline antibody as the anode labeling signal.The tetracycline was detected by the competitive immunoassay.The detection range of the developed biosensor was 0.01 ng mL^-1-10 ng mL^-1and the detection limit was 0.003 ng mL^-1.In addition,the biosensor showed outstanding selectivity,and reproducibility,which has great potential in the field of analysis and detection.（2）Construction of the near-infrared electrochemiluminescence biosensor based on photonic crystal signal enhancementIn this study,a near-infrared electrochemiluminescence biosensor based on SiO₂photonic crystal enhanced signal was constructed.The SiO₂photonic crystal film was prepared on the ITO electrode surface by vertical deposition method.Due to the Bragg scattering of the photonic crystal,the electrochemiluminescence signal of Cu-doped CdTeQDs was enhanced by about 8 folds.The SiO₂photonic crystal film modified Zika virus antibody was as the capture probe,and the Cu-doped CdTeQDs were coupled with the Zika virus secondary antibody as the signal probe,and a sandwich structure signal-enhanced near-infrared electrochemiluminescence biosensor was constructed.It realized the sensitive detection of Zika virus,the detection line range of this immunosensor was 1 fg mL^-1-100 pg mL^-1,and the detection limit was 0.30 fg mL^-1.Compared with other methods for detecting Zika virus,this method had a lower detection limit and a wider detection range.Moreover,this sensor showed excellent selectivity,stability and reproducibility,which had great advantages in the analysis and detection of Zika virus.