The Applications Of Plasmonic Nanoparticles In Visual Imaging Detection And Nanomotors

Localized Surface Plasmon Resonance(LSPR) is an optical phenomenon generated by light when it interacts with conductive nanoparticles that are smaller than the incident wavelength. The resonant frequency of LSPR strongly depends on the composition, size, geometry, dielectric environment and separation distance of NPs. Au and Ag are common noble metal materials, which due to the energy levels of d-d transitions exhibit LSPR in the visible range of the spectrum. However, Au is preferred for biological applications due to its biocompatibility and thiol-gold association for immobilization of biomolecules.Here we illustrated the applications of LSPR in biochemical sensing and nano-catalytic motors by using the LSPR and catalytic properties of Au NPs. The main findings are as follows:Firstly, we developed a method for imaging sebaceous Latent Fingerprints(LFPs) by using the optical advantages of Au NPs(high brightness, non-blinking and non-bleaching). Meanwhile, we designed a nanoplasmonic assay to provide quantitative information of RDX explosive residues in LFPs by exploring the competitive reduction of Cu2+ and RDX by NADH. The combination of fingerprint imaging and explosive detection might be used in forensic investigations to distinguish terrorists who carry explosives.Secondly, we report the development of an ultrasensitive nanoplasmonic probe for discriminative detection and imaging of dopamine released from living cells. This platform allows for the detection of dopamine with a detection limit down to 0.25 pM within 1 min. This nanoplasmonic assay is further applied to illustrate the mechanism of dopamine secretion, and suggested that ATP stimulated-release of dopamine is concomitant with Ca2+ influx, and the influx of Ca2+ is through ATP-activated channels instead of Voltage-gated Ca2+ channel(VGC).Thirdly, we report a chemical reaction-driven self-propulsion of Janus plasmonic nanomotor, and monitered its diffusivity by resonance light scattering correlation spectroscopy(RLSCS). The mechanism of the self-phoretic motion is explained as self-thermophoresis, which is a result of asymmetric temperature gradient of local solvent around Janus NPs in catalysis. We demonstrate a stochastic model describing the relation between the diffusion coefficients of self-thermophoresis motion with chemical reaction rate. This finding suggests a possible effect of energy conversion, from internal chemical entropy to thermal energy, and finally to kinetic energy. This observation opens a new avenue in the field of nanomotors on the basis of catalytic reaction.All above researches illustrated the applications of LSPR and catalytic properties of Au NPs in biochemical sensing, imaging and nano-catalytic motors. At last, this thesis gives a summary and an outlook of the research.