Equal intensity double plasmon resonance of bimetallic quasi-nanocomposites based on sandwich geometry

Plasmonic Metaparticles on a Blackbody Create Vivid Reflective Colors for Naked-Eye Environmental and Clinical Biodetection

Plasmonic dipoles are famous for their strong absorptivity rather than their reflectivity. Here, the as-yet unknown specular reflection and the Brewster effect of ultrafine plasmonic dipoles, metaparticles, are introduced and exploited as the basis of new design rules for advanced applications. A configuration of "Plasmonic metaparticles on a blackbody" is demonstrated and utilized for the design of a tailored perfect-colored absorber and for visual detection of environmental dielectrics that is not readily done by extinction plasmonics. Moreover, the Plasmonic Brewster Wavelength (PBW) effect is introduced as a new platform for the naked-eye and bulk biodetection of analytes. The technique operates based on slight changes of molecular polarizability which is not detectable via conventional plasmon resonance techniques. As a specific highlight, the clinical applicability of the PBW method is demonstrated while addressing the transduction plasmonic techniques' challenge in detection of bulk refractive index changes of the healthy and diseased human serum exosomes. Finally, the sputtering-based fabrication method used here is simple, inexpensive, and scalable, and does not require the sophisticated patterning approach of lithography or precise alignment of light coupling for the biodetection.

Fluorocarbon Thin Films Fabricated using Carbon Nanotube/Polytetrafluoroethylene Composite Polymer Targets via Mid-Frequency Sputtering

Carbon nanotube/polytetrafluoroethylene composite polymer targets are proposed for use in the fabrication of fluorocarbon thin films using the mid-frequency sputtering process. Fluorocarbon thin films deposited using carbon nanotube/polytetrafluoroethylene composite targets exhibit an amorphous phase with a smooth surface and show a high water contact angle, optical transmittance, and surface hardness. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy studies reveal that as the carbon nanotube concentration increased in the composite target, a carbon cross-linked structure was formed, which enhanced the film hardness and the modulus of the fluorocarbon thin film. Large-area fluorocarbon thin films with a substrate width of 700 mm were successfully fabricated by a pilot-scale roll-to-roll sputtering system using a carbon nanotube/polytetrafluoroethylene composite target.

The unusual visible photothermal response of free standing multilayered films based on plasmonic bimetallic nanocages

An unusual photothermal response in the visible region has been observed in free standing multilayered films based on the plasmonic bimetallic Au and Ag nanocages (Ag@AuNCs).

Thermo-Plasmonics for Localized Graphitization and Welding of Polymeric Nanofibers

There is a growing interest in modulating the temperature under the illumination of light. As a heat source, metal nanoparticles (NPs) have played an important role to pave the way for a new branch of plasmonics, i.e., thermo-plasmonics. While thermo-plasmonics have been well established in photo-thermal therapy, it has received comparatively less attention in materials science and chemistry. Here, we demonstrate the first proof of concept experiment of local chemistry and graphitization of metalized polymeric nanofibers through thermo-plasmonic effect. In particular, by tuning the plasmonic absorption of the nanohybrid through a change in the thickness of the deposited silver film on the fibers, the thermo-plasmonic effect can be adjusted in such a way that high enough temperature is generated enabling local welding and graphitization of the polymeric nanofibers.

Surface segregation in TiO2-based nanocomposite thin films

The morphology of nanocomposites plays a pivotal role in understanding their functionality and determines their capabilities for applications. The use of nanocomposite coatings requires a study of the size effects on their functional properties. Noble metal nanoparticles are promising candidates for nanocomposite thin film applications due to their antibacterial, plasmonic and photocatalytic properties. In this contribution, the morphology of Ag-TiO(2) and Au-TiO(2) nanocomposite thin films has been investigated experimentally using electron tomography in transmission electron microscopy in combination with UV/vis spectroscopy. Based on the additional 3D information obtained from tomography, we propose a two-step model towards the observed bimodal particle size in these nanocomposite thin films prepared by co-sputtering from two different sources. Furthermore, we show that the optical properties exhibit a well-defined relation with the morphology of the nanocomposite thin films. The present investigations demonstrate the potential of electron tomography for revealing the complex structure and formation processes of functional nanocomposites.

Simulation of optical properties of layered metallic nanoparticles embedded inside dielectric matrices: interference method or Maxwell Garnett effective-medium theory?

Optical characterization of composite films consisting of a ceramic matrix with embedded layered metal nanoparticles have recently received increasing interest. In particular, two methods have been mainly proposed in order to obtain optical performances of dielectric matrices containing layered nanoclusters (NCs): the first method is based on the simulation of the layered system as composed of alternated films of dielectric material and effective-medium material. Therefore, the optical response of the multilayer stack is calculated, assigning to the effective-medium layers the dielectric constant epsilon(f)(Yama), obtained by the Yamaguchi theory, and calculating the interference between the beams reflected and refracted at each interface inside the stack. The second method considers the multilayer stack as a single-layer effective-medium film whose dielectric constant is calculated by the Maxwell Garnett (MG) theory. In particular, this second method is recognized to be valid in the case of nanoparticles uniformly distributed inside a dielectric matrix. The present study shows that the interference method, as it has been applied up to now, does not allow reproducing reflectance and transmittance spectra calculated by the MG theory in the case of a uniform distribution of NCs.

Surface plasmon resonance of metal nanoparticles sandwiched between dielectric layers: theoretical modelling

Composite films consisting of a ceramic matrix with embedded metal nanoparticles have received increased interest due to their numerous potential applications in the field of optics and optoelectronics. Numerous studies have been dedicated to the fabrication of these composite materials and it has been shown that nanocermet films can be obtained by successive deposition of alternate dielectric and metal films of thicknesses opportunely chosen. In this case, stacks of dielectric layers alternated with layers of metal nanoclusters (NCs) are obtained. However, until now, optical characterization of these kinds of multilayer stack has been used to retrieve mainly qualitative information on the dimension, shape, and geometric distribution of nanoparticles inside the dielectric matrix. An easy-to-handle model that quantitatively links the optical properties to the main features of the NCs embedded in the matrix is presented. This model can be applied to multilayer stacks of dielectric layers alternated with metal NC layers and is shown to be a valid alternative to a recently published model [Nanotechnology 19, 125709 (2008)NNOTER0957-448410.1088/0957-4484/19/22/225302] that was applied to the case of a three-layer structure (dielectric/metal:dielectric/dielectric).