Construction Of Functionalized Inorganic Nanomaterials And Investigation Of Their Applications In Optical Assays

Optical assays represent an important type of analytical method that has been widely used in the detection of disease marker,food safety testing,water quality monitoring and dangerous goods inspection.This type of analytical method utilizes a variety of signal transmission pathways based on optical signals,including fluorescence intensity,reflectivity,absorbance,transmission and refractive index.Based on the change of optical signals,information ranging from concentration and structure can be provided with the appearance of analyst.In recent years,there is an increasing demand for the detection of chemical and biomolecules with high sensitivity and quick response.This demand also put forward a great challenge for optical assays in signal output and molecular recognition.With the development of nanotechnology,the emergence of inorganic nanomaterials has provided new ideas and development directions for the optical assays.Inorganic nanomaterials exhibit unique physical and chemical properties and have been widely used in biology,medicine,energy and chemistry.Among them,upconvertion nanomaterials and photonic crystal materials have received increasing attention in the field of optical assays due to their unique optical properties.However,these inorganic nanomaterials with special optical properties can only meet the requirement of signal output in optical assay.In order to meet the requirement of molecular recognition,endowing these inorganic nanomaterials with the capacity of targeted recognition is also required.In this work,we have constructed two types of optical sensors through combining surface functionalization with upconversion nanomaterials and photonic crystal materials.We further explored the applications of these developed optical sensors in the analysis of chemical and bioactive substances.The main contents of this dissertation are as follows:（1）We have developed a visual biosensor combining duplex molecular recognition and a signal-amplified substrate for simultaneous quantitation of two kinds of steroid hormones.Due to the different luminescence emissions and specific recognition properties of the aptamer-functionalized upconversion nanoprobes immobilized on the photonic crystal substrate,the simultaneous and specific assay of multiple hormones was realized.Because of the luminescence enhancement ability of the photonic crystal substrate,this method exhibited excellent capacity for hormone detection with high sensitivity,and the output optical signals can be observed visually for portable operation.Based on these unique merits,this luminescence-based biosensor showed superior detection performance in buffer solution as well as in complex serum samples.（2）The polyethyleneimine coated triiron tetroxide（Fe₃O₄@PEI）colloidal photonic crystal nanoparticles were firstly synthesized by hydrothermal reaction and ligand exchange progress.With the assistance of external magnetic field,Fe₃O₄@PEI nanoparticles can quickly self-assemble into Fe₃O₄@PEI photonic crystal and the structure colors of the photonic crystal can be flexibly turned by regulating the external magnetic field.Furthermore,we developed Fe₃O₄@PEI photonic crystal visual sensor by the fixed magnetic field strength.When the ionic strength increased gradually,the brilliant structure colors of the photonic crystal changed from red to blue with fast response and high sensitivity.In addition,this ionic strength sensor was not affected by the p H and the type of electrolyte,exhibiting high practicality in a wide range of applications.