Fluorescence Enhancement Properties And Biochip Applications Of Metal Layer/ZnO Nanorods

Fluorescence biochip is a micro sensor based on fluorescence detection,which can detect protein and other biological detection targets quantitatively and rapidly on the platformsurface.It has important applications in clinical diagnosis and pathological analysis.Fluorescence enhancement?FE?platform can significantly enhance the emission of fluorescence probes or the collection of fluorescence signal,thus greatly improving the performance of fluorescence biochip.Among all the reported FE materials,ZnO nanorods have many advantages,such as low cost,simple fabrication methods,highly controllable morphologies and orientation,large surface area,good light transmittance to visible light and near-infrared light,high biocompatibility and avoidance of fluorescence quenching,which show great application potential in the field of fluorescence biosensor.Although a lot of efforts have been devoted to explore FE properties of ZnO nanorods,the FE mechanisms of the ZnO nanorods and the FE performance optimization strategies are still unclear.Therefore,it is of great scientific significance and practical value to reveal the FE mechanism of ZnO nanorods,to optimize their FE properties and to realize their ultrahigh sensitive biochip applications.In this dissertation,the FE mechanisms and properties of metal layer/ZnO nanorod arrays and their ultrahigh sensitive fluorescence biochip applications for detection of carcinoembryonic antigen?CEA?,interleukin-6?IL-6?,and Fe³⁺ were studied.The main contents of this dissertation are as follows:The FE properties of ZnO nanorods and the CEA biochip application of Au layer/ZnO nanorods were studied.Six types of well-aligned and patterned ZnO nanorod arrays with different nanorod diameters were simultaneously fabricated on Si/Au platformwith the help of microprocessing techniques.The influence of the nanorod diameter,Au layer and the surrounding medium of nanorod on the FE properties of single ZnO nanorod were investigated.By combining the experimental studies with the finite-difference time-domain?FDTD?theoretical simulation,the effect of high-order waveguide modes,which depend on the nanorod diameter,in the FE properties of single ZnO nanorod is revealed.A typical rhodamine-6G?R6G?fluorescence probe was used to evaluate the detection capability of the optimized Au layer/ZnO nanorod array FE platform.Biochips based on Au layer/ZnO nanorod array were constructed to realize the ultra-high sensitivity detect CEA linked with cyanine-3?Cy3?fluorescein and the obtained limit of detection of CEA is 10 fg m L^-1.The IL-6 biochip application based on Ag layer/ZnO nanorod arrays was studied.Three types of highly packed ZnO nanorod arrays with different nanorod diameters were fabricated on the Ag layer in order to compare the contribution of surface area issue and the high-order waveguide modes issue to the FE properties of the nanorod arrays,and to further optimize their fluorescence enhancement performance.Through combination of the experimental studies with the FDTD simulation,it is revealed that the contribution of high-order waveguide modes on the FE performance of nanorod arrays is significantly higher than the surface area issue.The detection capability of R6 G fluorescent probe was evaluated by using optimized Ag layer/ZnO nanorod array.Based on the Ag layer/ZnO nanorod FE platform,biochips for IL-6 detection were constructed,which realized ultrahigh sensitive detection of IL-6.The limit of detection is 0.1 fg m L^-1.Such biochip can be applied to non-invasive detection of IL-6,i.e.highly sensitive detection of IL-6 in sweat.The FE properties and the Fe³⁺ ion detection applications of ZnO@SiO₂ nanorod arrays on Ag layer were studied.The Ag layer/ZnO nanorod arrays were coated with SiO₂ shell.The fluorescence enhancement properties of the Ag layer/ZnO@SiO₂ nanorods with different SiO₂ shell thicknesses were studied by using R6 G and carbon dots?CDs?as the fluorescence probes.The results show that the porous SiO₂ shell can increase the loading capacity of the fluorescent probes,which is beneficial to the fluorescence enhancement.On the other hand,FDTD simulation reveals the influence of SiO₂ shell thickness on the high-order waveguide modes-related evanescent field of the nanorods.Based on the optimized thickness of SiO₂ shell and the fluorescence sensing properties of CDs to Fe³⁺ ion,novel Ag layer/ZnO@SiO₂@CDs sensors were constructed for ultrahigh sensitive detection of Fe³⁺ ion and a significant limit of detection of Fe³⁺ as low as 0.1 n M was achieved.Excellent repeatable detection of Fe³⁺ in human serum and water was realized.