Nanocomposite thin films formed by noble metal nanoparticles embedded in a dielectric matrix show attractive optical properties at the surface plasmon resonance (SPR) wavelength due to dielectric and quantum confineme...Nanocomposite thin films formed by noble metal nanoparticles embedded in a dielectric matrix show attractive optical properties at the surface plasmon resonance (SPR) wavelength due to dielectric and quantum confinements effects. When such a metal-dielectric nanocomposite is excited by light, photons are coupled to the metal-dielectric interface, causing an induced charged density oscillation and showing a strong absorption maximum at a particular wavelength, called the SPR wavelength. Such pronounced resonance lines shown by noble-metal nanoparticles caused by collective excitations of conduction electrons are also known as particle plasmons (PPR) or Mie plasmons [1]. Many applications of these metal nanoparticle composite materials have been proposed taking advantage of the optical response at the SPR/PPR, including their use in surface enhanced Raman spectroscopy, surface enhanced second harmonic generation, and for the developement of color filters, sensors and all-optical switching devices. Polymer-metal nanocomposites are promising candidates for such optical functional applications. In these systems, very small particle sizes enhance the optical properties while the polymer matrix materials will act to stabilize the particle size and growth besides providing the required transparent medium. Of great significance is the ability to tune and extend the plasmon resonance wavelength, which is highly desirable in various applications of metallic nanoparticles. Since the plasmon resonance depends on the particle size, shape, filling factor (i.e. volume fraction of the metallic nanoparticles), dielectric properties of the metallic nanoparticles itself, as well as the surrounding dielectric medium, there are several approaches towards the ability to tune plasmon resonance wavelengths by varying these parameters. In this regard, a multicomponent optical system equipped with several plasmon resonance wavelengths and equally tunable response over a spectral range would be of interest for potential multifunctional operations at many wavelengths. However, no optical system exists with tunable multiple PPR wavelengths without affecting the geometry of the nanoparticles or the materials system. We demonstrate a simple method of vapor phase co-deposition at elevated target temperature [2] coupled with a novel selective masking technique [3] to produce a multicomponent optical material with as many as seven different ultraviolet-visible optical active planes. Such system consists of different nanocomposites of Teflon AF/Ag, Teflon AF/Au and Teflon AF/Cu with sharp interfaces. The fabricated system has regions of single nanocomposite plane together with multilayer structures facilitating tunable multiple particle plasmon resonance wavelength response from a single system. Distinct double and triple plasmon wavelength resonance absorptions could be obtained from such interfaces forming multilayers of either two or three nanocomposite structures. Production of ultra-thin (50 - 100 nm) polymer-metal color filters are also shown.展开更多
文摘Nanocomposite thin films formed by noble metal nanoparticles embedded in a dielectric matrix show attractive optical properties at the surface plasmon resonance (SPR) wavelength due to dielectric and quantum confinements effects. When such a metal-dielectric nanocomposite is excited by light, photons are coupled to the metal-dielectric interface, causing an induced charged density oscillation and showing a strong absorption maximum at a particular wavelength, called the SPR wavelength. Such pronounced resonance lines shown by noble-metal nanoparticles caused by collective excitations of conduction electrons are also known as particle plasmons (PPR) or Mie plasmons [1]. Many applications of these metal nanoparticle composite materials have been proposed taking advantage of the optical response at the SPR/PPR, including their use in surface enhanced Raman spectroscopy, surface enhanced second harmonic generation, and for the developement of color filters, sensors and all-optical switching devices. Polymer-metal nanocomposites are promising candidates for such optical functional applications. In these systems, very small particle sizes enhance the optical properties while the polymer matrix materials will act to stabilize the particle size and growth besides providing the required transparent medium. Of great significance is the ability to tune and extend the plasmon resonance wavelength, which is highly desirable in various applications of metallic nanoparticles. Since the plasmon resonance depends on the particle size, shape, filling factor (i.e. volume fraction of the metallic nanoparticles), dielectric properties of the metallic nanoparticles itself, as well as the surrounding dielectric medium, there are several approaches towards the ability to tune plasmon resonance wavelengths by varying these parameters. In this regard, a multicomponent optical system equipped with several plasmon resonance wavelengths and equally tunable response over a spectral range would be of interest for potential multifunctional operations at many wavelengths. However, no optical system exists with tunable multiple PPR wavelengths without affecting the geometry of the nanoparticles or the materials system. We demonstrate a simple method of vapor phase co-deposition at elevated target temperature [2] coupled with a novel selective masking technique [3] to produce a multicomponent optical material with as many as seven different ultraviolet-visible optical active planes. Such system consists of different nanocomposites of Teflon AF/Ag, Teflon AF/Au and Teflon AF/Cu with sharp interfaces. The fabricated system has regions of single nanocomposite plane together with multilayer structures facilitating tunable multiple particle plasmon resonance wavelength response from a single system. Distinct double and triple plasmon wavelength resonance absorptions could be obtained from such interfaces forming multilayers of either two or three nanocomposite structures. Production of ultra-thin (50 - 100 nm) polymer-metal color filters are also shown.
