Multilaver-Coated Functional Gold Nanoparticles And Their Applications In Biomedicine And Liquid Crystal Devices

The properties of nanoparticles are of great differences compared to bulk materials. Based on the unique optical features brought by an effect called "surface plasmon resonance (SPR)", gold nanoparticles are of great use in optics, physics, biomedicine, etc. This article proposes two innovative multilayer coating methods of gold nanoparticles, introduces their optical and chemical properties as well as functionalization, and establishes their applications in the fields of biomedicine and liquid crystal devices.We will first introduce a silica-polymer-multilayer-coated gold nanorod. Through the functionalization by fluorescence/Raman reporter molecules, it can carry multiple optical signals, forming relatively independent fluorescence and surface-enhanced Raman Scattering (SERS) channels. We will discuss its tunability in multiple dimensions and the ultra-high stability. Moreover, the photodynamic thrapy (PDT) photosensitizers could also be loaded onto this nanoparticle, giving it a great potential in biological use.Such silica-polymer-coated nanoparticles could be applied into biomedicine applications. We will introduce their circulation, metabolism and aggregation in tumor in vivo. By combining the advantages of both fluorescence imaging and SERS detection, these nanoparticles are applied to achieve fast, large area and specific tumor targeting in vivo. Photodynamic therapy can also be applied right after the detection of tumor, realizing a in vivo simultaneous tumor diagnosis and therapy (theranosis).In the second part of the article, we will introduce another fast, simple, well-controllable and well-adapted multilayer coating methods of gold nanoparticles using small molecules, together with their stability, shell thickness and optical properties. Such nanoparticles can enhance the Raman signals from external molecules without any doping procedures, or, through a very simple modification step, it can also act as a flexible SERS probe.We dope the small-molecule-multilayer-coated gold nanorods and gold nanoplatelets into a liquid crystal, in which they will be aligned and absorb light with a specific polarization, leading to an E-polarizer. We will discuss its polarization-dependent absorption and voltage response, including the measurements of multiple parameters as threshold voltage and response time. We will also discuss, according to the experimental results, the self-assemble aggregation of gold nanoparticles in liquid crystal.