Loading...
3 results
Search Results
Now showing 1 - 3 of 3
- Analysis of metallic nanoparticles embedded in thin film semiconductors for optoelectronic applicationsPublication . Fantoni, Alessandro; Fernandes, Miguel; Vygranenko, Yuri; Louro, Paula; Vieira, Manuela; Silva, R. P. O.; Teixeira, D.; Da Costa Ribeiro, Ana Paula; Prazeres, Duarte; Alegria, ElisabeteThis paper reports about a study of the local plasmonic resonance (LSPR) produced by metal nanoparticles embedded in a dielectric or semiconductor matrix. It is presented an analysis of the LSPR for different nanoparticle metals, shapes, and embedding media composition. Metals of interest for nanoparticle composition are Aluminum and Gold. Shapes of interest are nanospheres and nanotriangles. We study in this work the optical properties of metal nanoparticles diluted in water or embedded in amorphous silicon, ITO and ZnO as a function of size, aspect-ratio and metal type. Following the analysis based on the exact solution of the Mie theory and DDSCAT numerical simulations, it is presented a comparison with experimental measurements realized with arrays of metal nanospheres. Simulations are also compared with the LSPR produced by gold nanotriangles (Au NTs) that were chemically produced and characterized by microscope and optical measurements.
- Effect of graphene vs. reduced graphene oxide in gold nanoparticles for optical biosensors: a comparative studyPublication . Carvalho, Ana P. G.; Alegria, Elisabete; Fantoni, Alessandro; Ferraria, Ana Maria; Rego, Ana; Da Costa Ribeiro, Ana PaulaAiming to develop a nanoparticle-based optical biosensor using gold nanoparticles (AuNPs) synthesized using green methods and supported by carbon-based nanomaterials, we studied the role of carbon derivatives in promoting AuNPs localized surface plasmon resonance (LSPR), as well as their morphology, dispersion, and stability. Carbon derivatives are expected to work as immobilization platforms for AuNPs, improving their analytical performance. Gold nanoparticles (AuNPs) were prepared using an eco-friendly approach in a single step by reduction of HAuCl4·3H2O using phytochemicals (from tea) which act as both reducing and capping agents. UV–Vis spectroscopy, transmission electron microscopy (TEM), zeta potential (ζ-potential), and X-ray photoelectron spectroscopy (XPS) were used to characterize the AuNPs and nanocomposites. The addition of reduced graphene oxide (rGO) resulted in greater dispersion of AuNPs on the rGO surface compared with carbon-based nanomaterials used as a support. Differences in morphology due to the nature of the carbon support were observed and are discussed here. AuNPs/rGO seem to be the most promising candidates for the development of LSPR biosensors among the three composites we studied (AuNPs/G, AuNPs/GO, and AuNPs/rGO). Simulations based on the Mie scattering theory have been used to outline the effect of the phytochemicals on LSPR, showing that when the presence of the residuals is limited to the formation of a thin capping layer, the quality of the plasmonic resonance is not affected. A further discussion of the application framework is presented.
- A simulation study of surface plasmons in metallic nanoparticles: dependence on the properties of an embedding a-Si:H MatrixPublication . Fantoni, Alessandro; Fernandes, Miguel; Vygranenko, Yuri; Louro, Paula; Vieira, Manuela; Alegria, Elisabete; Da Costa Ribeiro, Ana Paula; Teixeira, DanielaThe development and realization of a plasmonic structure based on the LSP interaction of metal nanoparticles with an embedding matrix of amorphous silicon is proposed. As a planned application, this structure will need to be usable as the basis for a sensor device applied in biomedical applications, after proper functionalization with selective antibodies. The final sensor structure needs to be low-cost, compact, and disposable. The study reported in this paper aims to analyze varied materials for nanoparticles embedded in an amorphous silico matrix. Metals of interest for nanoparticles composition are aluminum and gold. As a comparison term, a non-plasmonic material like alumina, resulting from oxidation of Al nanoparticles, is also considered. As a preliminary approach to this device, we study in this work the optical properties of spherical metal nanoparticles embedded in an amorphous silicon matrix, as a function of size and metal type. Following an analysis based on the exact solution of the Mie theory, experimental measurements realized with arrays of metal nanoparticles are compared with the simulations.