title: Au nanoparticle monolayers covered with sol-gel oxide thin films: optical and morphological study.
abstract: In this work, we provide a detailed study of the influence of thermal annealing on submonolayer Au nanoparticle deposited on functionalized surfaces as standalone films and those that are coated with sol-gel NiO and TiO(2) thin films. The systems are characterized through the use of UV-vis absorption, X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and spectroscopic ellipsometry. The surface plasmon resonance peak of the Au nanoparticles was found to red-shift and increase in intensity with increasing surface coverage, an observation that is directly correlated to the complex refractive index properties of Au nanoparticle layers. The standalone Au nanoparticles sinter at 200 °C, and a relationship between the optical properties and the annealing temperature is presented. When overcoated with sol-gel metal oxide films (NiO, TiO(2)), the optical properties of the Au nanoparticles are strongly affected by the metal oxide, resulting in an intense red shift and broadening of the plasmon band; moreover, the temperature-driven sintering is strongly limited by the metal oxide layer. Optical sensing tests for ethanol vapor are presented as one possible application, showing reversible sensing dynamics and confirming the effect of Au nanoparticles in increasing the sensitivity and in providing a wavelength dependent response, thus confirming the potential use of such materials as optical probes.
authors.affiliation: Dipartimento di Ingegneria Meccanica Settore Materiali, Università di Padova, Via Marzolo, 9, 35131 Padova, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Della Gaspera
authors.forename: Matthias
authors.initials: M
authors.lastname: Karg
authors.forename: Julia
authors.initials: J
authors.lastname: Baldauf
authors.forename: Jacek
authors.initials: J
authors.lastname: Jasieniak
authors.forename: Gianluigi
authors.initials: G
authors.lastname: Maggioni
authors.forename: Alessandro
authors.initials: A
authors.lastname: Martucci
mesh_terms: D005782:Gels; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D010087:Oxides / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D020349:Surface Plasmon Resonance; D014961:X-Ray Diffraction
chemical_list: D005782:Gels; D010087:Oxides; D006046:Gold