Preparation Of Novel Nanomaterials For Detection And Establishment Of Single Particle Dark-field/Raman/Fluorescence Microscopy Setup

The preparation of nanomaterials for detection has been a hot topic in nanoscience and nanotechnology. Nanomaterials have been exploited for the extensive potential applications in environmental analysis, bioanalysis, etc., due to their fascinating optical properties. The extension field is relevant directly to the preparation of nanomaterials and the investigation of optical properties. Therefore, it is necessary to prepare highly sensitive and stable nanomaterials for detection. On the basis of the functional nanomaterials, the analytical techniques can provide multiplexed images and spectra signatures of analytes on the nanomaterials, while expanding the application area of nanomaterials. On these account, the dissertation focuses on the preparation of nanomaterials for detection, as well as the coupling of surface-enhanced Raman scattering (SERS) with dark-field tecnnique and fluorescence microscopy. The details are summarized as follows:1. Synthesis of Au@SiO2@Ag nanostructure and characterization of its morphology and SERS activityA novel SERS substrate (Au@SiO2@Ag) has been fabricated by combining self-assembly and electrodeposition methods. Rhodamine B (RdB) has been used as a probe molecule to investigate the SERS activity of the substrates at different deposition times. The results show that optimum SERS substrate can be used as a SERS sensor and RdB can be detected down to 1.0×10-11 M. Moreover, the Au@SiO2@Ag can be regenerated by cyclic stripping and electrodeposition and reused for SERS analysis without the interference of previous analytes.2. Synthesis, characterization and application of a portable SERS sensor for rapid detection of environmental pollutantsA portable SERS sensor, silver-electrodeposited screen-printed electrode (Ag-SPE), is developed and applied to qualitative and quantitative detection of three aniline derivatives and three phenol derivatives with an electrostatic preconcentration technique to amplify the signals. The limit of detection for the six polar organic polutants is about 4.2×10-10 M. Furthermore, the stable and recyclable functionalities allow one to reuse the sensor in SERS analysis.3. Synthesis, characterization and application of a novel multifunctional nanomaterial in bioanalysis A multifunctional nanomaterial (CdTe@SiO2@Au) has been fabricated by combining sol-gel technology and covalent self-assembly method. Due to the surface plasmon resonance, fluorescent property and electrocatalytic activity, CdTe@SiO2@Au can serve as optical probes for dark-field light scattering imaging and fluorescence imaging. In addition, the CdTe@SiO2@Au can be used as SERS substrate and electrochemical biosensor for detection of adenosine and H2O2, respectively. The limits of detection for adenosine and H2O2 are 1.0×10×10-8 M and 1.3×10-7 M, respectively.4. Establishment of single particle dark-field/Raman/fluorescence microscopy setup and its application in imaging and spectral analysis of single gold nanoparticles (GNPs)A novel setup, single particle dark-field/Raman/fluorescence microscopy setup, has been established by coupling inverted fluorescence microscope to spectroscopy system, charge coupled devices (CCD) camera and CCD spectrography. Combining inverted fluorescence microscopy, dark-field technique, Raman spectroscopy and electrochemistry, the combined setup is capable of obtaining potential-dependant plasmon resonance scattering (PRS) spectra, Raman spectra and fluorescence emission spectra together with their images from the single particle simultaneously. The electron transfer process on the single GNPs can be monitored by the changes in PRS spectra of GNPs at different potentials. The combined setup has also been used to study the SERS spectra of cytochrome c on functionalized GNPs at different applied potentials. The changes in the in situ SERS spectra indicate that there is redox transformation of cytochrome c on the single GNPs.