Internalization of Pegylated Er:Y2O3 Nanoparticles inside HCT-116 Cancer Cells: Implications for Imaging and Drug Delivery.

Lanthanide-doped nanoparticles, featuring sharp emission peaks with narrow bandwidth, exhibit high downconversion luminescence intensity, making them highly valuable in the fields of bioimaging and drug delivery. High-crystallinity Y2O3 nanoparticles (NPs) doped with Er3+ ions were functionalized by using a pegylation procedure to confer water solubility and biocompatibility. The NPs were thoroughly characterized using transmission electron microscopy (TEM), inductively coupled plasma mass spectrometry (ICP-MS), and photoluminescence measurements. The pegylated nanoparticles were studied both from a toxicological perspective and to demonstrate their internalization within HCT-116 cancer cells. Cell viability tests allowed for the identification of the "optimal" concentration, which yields a detectable fluorescence signal without being toxic to the cells. The internalization process was investigated using a combined approach involving confocal microscopy and ICP-MS. The obtained data clearly indicate the efficient internalization of NPs into the cells with emission intensity showing a strong correlation with the concentrations of nanoparticles delivered to the cells. Overall, this research contributes significantly to the fields of nanotechnology and biomedical research, with noteworthy implications for imaging and drug delivery applications.

Effect of the Oxidation Process on Carrier Lifetime and on SF Defects of 4H SiC Thick Epilayer for Detection Applications.

The aim of this work was a deep spectroscopical characterization of a thick 4H SiC epitaxial layer and a comparison of results between samples before and after a thermal oxidation process carried out at 1400 °C for 48 h. Through Raman and photoluminescence (PL) spectroscopies, the carrier lifetimes and the general status of the epilayer were evaluated. Time-resolved photoluminescence (TRPL) was used to estimate carrier lifetime over the entire 250 µm epilayer using different wavelengths to obtain information from different depths. Furthermore, an analysis of stacking fault defects was conducted through PL and Raman maps to evaluate how these defects could affect the carrier lifetime, in particular after the thermal oxidation process, in comparison with non-oxidated samples. This study shows that the oxidation process allows an improvement in the epitaxial layer performances in terms of carrier lifetime and diffusion length. These results were confirmed using deep level transient spectroscopy (DLTS) measurements evidencing a decrease in the Z1/2 centers, although the oxidation generated other types of defects, ON1 and ON2, which appeared to affect the carrier lifetime less than Z1/2 centers.

Temperature Investigation on 3C-SiC Homo-Epitaxy on Four-Inch Wafers.

In this work, results related to the temperature influence on the homo-epitaxial growth process of 3C-SiC is presented. The seed for the epitaxial layer was obtained by an innovative technique based on silicon melting: after the first step of the hetero-epitaxial growth process of 3C-SiC on a Si substrate, Si melts, and the remaining freestanding SiC layer was used as a seed layer for the homo-epitaxial growth. Different morphological analyses indicate that the growth temperature and the growth rate play a fundamental role in the stacking faults density. In details, X-ray diffraction and micro-Raman analysis show the strict relationship between growth temperature, crystal quality, and doping incorporation in the homo-epitaxial chemical vapor deposition CVD growth process of a 3C-SiC wafer. Furthermore, photoluminescence spectra show a considerable reduction of point defects during homo-epitaxy at high temperatures.

Visible emission from bismuth-doped yttrium oxide thin films for lighting and display applications.

Due to the great development of light sources for several applications from displays to lighting, great efforts are devoted to find stable and efficient visible emitting materials. Moreover, the requirement of Si compatibility could enlarge the range of applications inside microelectronic chips. In this scenario, we have studied the emission properties of bismuth doped yttrium oxide thin films grown on crystalline silicon. Under optical pumping at room temperature a stable and strong visible luminescence has been observed. In particular, by the involvement of Bi ions in the two available lattice sites, the emission can be tuned from violet to green by changing the excitation wavelength. Moreover, under electron beam at low accelerating voltages (3 keV) a blue emission with high efficiency and excellent stability has been recorded. The color is generated by the involvement of Bi ions in both the lattice sites. These peculiarities make this material interesting as a luminescent medium for applications in light emitting devices and field emission displays by opening new perspectives for the realization of silicon-technology compatible light sources operating at room temperature.

Tyrosine capped silver nanoparticles: A new fluorescent sensor for the quantitative determination of copper(II) and cobalt(II) ions.

Nanoparticles have been increasingly used as sensors for several organic and inorganic analytes. In this work, we report a study on the synthesis of novel highly fluorescent l-Tyr capped silver nanoparticles (AgNPs) and their use for the determination of metal ions. The AgNPs have been characterized by TEM, UV-Vis and Photoluminescence (PL) spectroscopy and dynamic light scattering (DLS) measurements and used for the quantitative determination of Co(II) and Cu(II) ions. In the l-Tyr capped AgNPs, the α-amino and α-carboxyl groups of the surface-confined amino acid can coordinate the entitled metal ions, giving rise to a decrease of the silver surface plasmon absorption, that is linearly correlated with the metal ions concentrations. The addition of Co(II) and Cu(II) solutions to the l-Tyr AgNPs also induces a paramagnetic quenching of the fluorescence in the PL spectra and the related Stern Volmer plots highlight a linear correlation over the whole concentration range for both metal ions, with a more pronounced effect for the copper(II) ion.

Silicon nanowire and carbon nanotube hybrid for room temperature multiwavelength light source.

The realization of an innovative hybrid light source operating at room temperature, obtained by embedding a carbon nanotube (CNT) dispersion inside a Si nanowire (NW) array is reported. The NW/CNT system exhibits a peculiar photoluminescence spectrum, consisting of a wide peak, mainly observed in the visible range, due to quantum confined Si NWs, and of several narrower IR peaks, due to the different CNT chiralities present in the dispersion. The detailed study of the optical properties of the hybrid system evidences that the ratio between the intensity of the visible and the IR emissions can be varied within a wide range by changing the excitation wavelength or the CNT concentration; the conditions leading to the prevalence of one signal with respect to the other are identified. The multiplicity of emission spectra obtainable from this composite material opens new perspectives for Si nanostructures as active medium in light sources for Si photonics applications.