Controllable Preparation Of Ag / SiO <2> Photonic Crystal Coding Microspheres And Its SERS Application

Surface enhanced Raman scattering has been more and more widely used in the environmental monitoring, biological analysis because of its advantages of unique narrow band, high sensitivity, fast and non-destruction. A high quality of the SERS spectrum is dependent on the active substrates which provide efficient and stable. So the preparation of the SERS active substrates with high sensitivity and excellent reproducibility is the focus of our research. With the rapid development of nanoscience, SERS technique and remarkable progress of material preparation technology, people have no longer satisfied with the SERS active substrate of single enhancement function, but to consider the substrate with multi-function, operability, cost, sensitivity and practical applications. In this paper, silica photonic crystal beads (SPCBs) will be combined with SERS technology. Highly ordered silver nanoshells silica photonic crystal beads was be prepared by building a complex system of silver nanoparticles with silica photonic crystal beads. These SERS active substrates were high sensitivity, stable and orderly structure because of the electromagnetic enhancement effect of silver nanoparticles and the structure characteristics of the photonic crystal beads. Besides, the SERS active substrates could used for multiplex bioassay by coding silica photonic crystal beads and detecting SERS signal. This work provided a promising approach for the fabrication of efficient encoded SERS substrates and further development of high-throughput biological assays.(1) Based on the preparation of silica nanoparticles by improving the Stober method, SPCBs were synthesized by a microfluidic device.The codes of SPCBs were stable and accuracy. After the surface of SPCBs was functionalized with NH2 group, AgNPs were in situ deposited onto the SPCBs (reflection peaks at 470,538 and 625 nm), which were used to detecting SERS performance by 4-MBA. The SERS active substrates were successfully used in the detection of malachite green,which demonstrated high sensitivity and wide linear range.(2) Using CEA and AFP as models, an efficient multiplex SERS bioassay was constructed for detection of two tumor markers using one Raman label. Two kinds of encoded Ag/SPCBs (reflection peaks at 538 and 625 nm) were chosen to immobilize CEA and AFP antibodies, respectively. These two kinds of antibody immobilized beads were mixed with the mixture of CEA and AFP for the first incubation step. SERS signal-amplified probe (4-MBA/antibody/AgNPs) were then added to the system for the second incubation step. By selecting the appropriate molecular markers and a certain measure of AgNPs, antigen detection sensitivity can be achieved 10-15g/mL in our system. Single type of antigen and multiple types of antigens both have been detected by encoded Ag-SPCBs. The proposed method is expected to be a good tool in rapid biomolecular screening and highly sensitive detection.(3) We obtained non-close packed FCC SPCBs by chemical etching in the solution of pH=12.0, the nanogaps of the SPCBs became larger with the increase of the corrosion temperature and etching time.With the AgNPs in situ deposited onto the beads, lots of SERS "hot spots"were produced. It was showed higher SERS repeatability and stability for 4-MBA and The SERS active substrate were successfully used in the detection of biomolecule (human-IgG),which showed high sensitivity and wide linear range.