An intense photoluminescence emission was observed from noble metal nanoclusters (Pt, Ag or Au) embedded in sapphire plates, nucleated by MeV ion-implantation and assisted by an annealing process. In particular, the spectral photoluminescence characteristics, such as range and peak emission, were compared to the behavior observed from Pt nanoclusters embedded in a silica matrix and excited by UV irradiation. Correlation between emission energy, nanoclusters size and metal composition were analyzed by using the scaling energy relation E_Fermi/N^1/3 from the spherical Jellium model. The metal nanocluster luminescent spectra were numerically simulated and correctly fitted using the bulk Fermi energy for each metal and a Gaussian nanoclusters size distribution for the samples. Our results suggest protoplasmonics photoluminescence from metal nanoclusters free of surface state or strain effects at the nanoclusters-matrix interface that can influence over their optical properties. These metal nanoclusters present very promising optical features such as bright visible photoluminescence and photostability under strong picosecond laser excitations. Besides superlinear photoluminescence from metal nanoclusters were also observed under UV high power excitation showing a quadratic dependence on the pump power fluence.

Ferromagnetic-like behavior at room temperature (300 K) was observed in Pt particles embedded in ion-implanted silica matrices. Results in samples integrated by ultra-small photoluminescent Pt clusters (3 nm). The ferromagnetic behavior coexists simultaneously with a diamagnetic response. Enhanced diamagnetic response of one order of magnitude was observed compared to typical diamagnetism in pure silica, and it is increased with the mean diameter of the Pt particles. Besides, a larger sensitivity to an external field was observed in the ferromagnetic response of the nanostructures with a characteristic saturation at 20 kOe. This ferromagnetic behavior was only observed in the samples with nucleated Pt particles. The magnitude of the saturation magnetization shows up to a fivefold increase in the samples with smaller particle size and larger particle density. Saturation magnetization was observed between 3–15 × 10 ⁻⁴ emu g ⁻¹ , with remanent magnetization of 0.2–0.6 × 10 ⁻⁴ emu g ⁻¹ , measured at 300 K. Coercitive fields also decrease in samples with smaller size and particles density, with values of 114 and 300 Oe. At lower temperatures (5 K) the saturation magnetization increases, as it would be expected from a ferromagnetic state. Optomagnetic response was studied by inverse Faraday effects and induced photomagnetization with circular polarized picosecond pulsed light at 1064 nm wavelength. Results showed that samples with a stronger ferromagnetic response exhibit larger Faraday rotation up to 5.3 × 10 ³ deg cm ⁻¹ by light excitations with irradiances between 50 and 180 GW cm ⁻² . These findings have immediate applications in multifunctional solid-state magneto-optical devices such as optical isolators, high-data storage devices and ultrafast all-optical switching of magnetization.

The third-order nonlinear infrared and ultraviolet properties exhibited by silicon quantum dots irradiated by ultrashort pulses were studied. The samples were prepared by 1.5 MeV Si⁺²ion implantation processes in high-purity silica substrates. Femtosecondz-scan measurements conducted at 830 nm wavelength revealed strong self-focusing effects together with two-photon absorption that can be switched to saturable absorption as a function of the input irradiance. Changes in the main physical mechanism responsible for the picosecond absorptive nonlinearity in the sample were also observed at 355 nm, made possible by the assistance of photothermal phenomena. Ultraviolet self-diffraction explorations allowed us to estimate the Kerr effect of the nanostructures. Potential applications for developing all-optical filtering functions performed by silicon-based nanosystems can be considered.

A systematic study has been carried out to investigate photoluminescence and third order nonlinear ultraviolet properties exhibited by platinum nanoparticles nucleated in a high-purity silica matrix. The modification in the characteristic photoluminescence spectra of the nanocomposites, ranging between 400 and 600 nm, was obtained with the assistance of a thermal annealing process that changed the average size of the platinum nanoparticles. The influence of temperature, between 200 °C–1100 °C, during the thermal treatment of the nanostructures was analyzed. UV–vis spectroscopy studies corroborated changes in the optical absorption resonances of the ion-implanted samples after annealing, which could then be correlated with the average size of the nanoparticles. The estimated average size was also corroborated by transmision electron microscopy. For temperatures below 600 °C the system is mainly composed of ultra-small photoluminescent platinum nanoparticles. Larger platinum nanoparticles were formed at higher annealing temperatures but photoluminescence quenching was observed as the typical plasmonics response of larger metal nanoparticles started to emerge. The photoluminescence emission for samples with a particle size of less than 2 nm is enhanced approximately 12 fold with respect to the samples with a particle size in the range of 3–7 nm. Differences in the resulting photoluminescence spectra were revealed by substituting the participation of argon, hydrogen or nitrogen, as environmental gases for thermal annealing. A weak PL emission, featuring 1.5 nW at a laser excitation power of 800 μW, related to larger platinum nanoparticles was observed. New emission peaks emerging from the larger platinum nanoparticles were associated with possible hydrogen adsorption on the nanoparticles' surface. Third order nonlinear ultraviolet measurements were conducted using a time-resolved two-wave mixing method with self-diffraction at 355 nm wavelength. The observed self-diffraction decay time is less than 25 ps, regardless of the average size of the nanoparticles studied. The evolution of the self-diffracted intensities derived from temperature was also linked to the mean size of the nanoparticles in the samples. Comparative two-wave mixing evaluations also validated a modification in third order nonlinear susceptibility exhibited by annealed samples. An important role of the localized surface plasmon resonance phenomena associated with the platinum nanoparticles for photoluminescence and optical nonlinearities was identified. A proposed hypothetical electronic mechanism that may explain the exceptional optical transitions related to low-dimensional platinum systems is discussed.

We studied the photoluminescence (PL) of Si nanocrystals (Si-NCs) embedded in SiO₂obtained by ion implantation at MeV energy. The Si-NCs are formed at high depth (1-2 μm) inside the SiO₂achieving a robust and better protected system. After metal ion implantation (Ag or Au), and a subsequent thermal annealing at 600°C under hydrogen-containing atmosphere, the PL signal exhibits a noticeable increase. The ion metal implantation was done at energies such that its distribution inside the silica does not overlap with the previously implanted Si ion . Under proper annealing Ag or Au nanoparticles (NPs) could be nucleated, and the PL signal from Si-NCs could increase due to plasmonic interactions. However, the ion-metal-implantation-induced damage can enhance the amount of hydrogen, or nitrogen, that diffuses into the SiO₂matrix. As a result, the surface defects on Si-NCs can be better passivated, and consequently, the PL of the system is intensified. We have selected different atmospheres (air, H₂/N₂and Ar) to study the relevance of these annealing gases on the final PL from Si-NCs after metal ion implantation. Studies of PL and time-resolved PL indicate that passivation process of surface defects on Si-NCs is more effective when it is assisted by ion metal implantation.