Giovanni Perotto

Optimized Electroless Silver Coating for Optical and Plasmonic Applications

Electroless metal deposition is a simple and convenient technique to fabricate metallic films and to provide isotropic metal functionalization of 3D structures with complex geometries. In this work, we describe the synthesis of silver coatings by means of a modified Tollens reaction and their use as optical coating. The chemical composition of the metallization bath is here addressed to optimize the metal coating deposition. The synthesis parameters have been tailored in order to deposit very smooth films which were characterized by scanning electron microscopy, atomic force microscopy, and optical spectroscopy. 2D diffraction gratings and sinusoidal plasmonic gratings were produced with the proposed method. Optical characterization confirmed the plasmonic activities of the resultant structures, proving the efficiency of the described method for optical applications. Thermal annealing was found to improve the surface roughness of the coating and therefore the optical properties of the plasmonic gratings.

Implantation damage effects on the Er 3+ luminescence in silica

The possibility to control the room temperature Er3+ photoluminescence efficiency in silica is investigated in terms of the damage produced in Er-doped silica by implantations at different fluences with Xe or Au ions. These implantations are tailored to reproduce the same level of damage in Er-doped silica. The remarkable differences in terms of the photoluminescence intensity between Xe- and Au-irradiated samples allowed to decouple the detrimental effect of the implantation damage on the photoluminescence from the beneficial broad-band energy transfer process provided by molecule-like Au clusters formed upon thermal annealing. The evolution of the implantation damage is followed by photoluminescence and correlated to the local Er-site by x-ray absorption spectroscopy.

Titanate Fibroin Nanocomposites: A Novel Approach for the Removal of Heavy-Metal Ions from water

In this study, we report the fabrication of nanocomposites made of titanate nanosheets immobilized in a solid matrix of regenerated silk fibroin as novel heavy-metal-ion removal systems. The capacity of these nanocomposite films to remove lead, mercury, and copper cations from water was investigated, and as shown by the elemental quantitative analysis performed, their removal capacity is 73 mmol/g for all of the ions tested. We demonstrate that the nanocomposites can efficiently retain the adsorbed ions, with no release of titanate nanosheets occurring even after several exposure cycles to ionic solutions, eliminating the risk of release of potentially hazardous nanosubstances to the environment. We also prove that the introduction of sodium ions in the nanocomposite formulation makes the materials highly selective toward the lead ions. The developed biopolymer nanocomposites can be potentially used for the efficient removal of heavy-metal-ion pollutants from water and, thanks to their physical and optical characteristics, offer the possibility to be used in sensor applications.

Plasmonic Nanoshell Antennas for Enhanced Sensing Bio‐Labeling

SiO2 core, Au shell nanoparticles are employed as plasmonic nanoantennas for enhanced sensing bio‐labeling. Electrodynamics calculations show that strong absorption and emission enhancements are obtained in a wide spectral range, suitable for a large variety of commonly employed bio‐labels. Furthermore, the shell geometry is able to provide high bio‐compatibility by embedding the labels in the inner cavity.

Rare-earth fluorescence thermometry of laser-induced plasmon heating in silver nanoparticles arrays

The laser-induced plasmon heating of an ordered array of silver nanoparticles, under continuous illumination with an Ar laser, was probed by rare-earth fluorescence thermometry. The rise in temperature in the samples was monitored by measuring the temperature-sensitive photoluminescent emission of a europium complex (EuTTA) embedded in PMMA thin-films, deposited onto the nanoparticles array. A maximum temperature increase of 19 °C was determined upon resonant illumination with the surface plasmon resonance of the nanoarray at the highest pump Ar laser power (173 mW). The experimental results were supported by finite elements method electrodynamic simulations, which provided also information on the temporal dynamics of the heating process. This method proved to be a facile and accurate approach to probe the actual temperature increase due to photo-induced plasmon heating in plasmonic nanosystems.