We report the functionalization of Si/SiO2 Quantum Dots (QDs) synthesised by laser ablation. Our interest has been to
increase the affinity of the QDs surface for organic substances, in order to obtain QD-immunoglobulin conjugates,
particularly for biolabeling. We have studied the UV-induced graft polymerization of the freestanding nanoparticles.
High resolution transmission electron microscopy and laser granulometry, were used to obtain information on particle
and cluster size distribution, degree of agglomeration, etc. The polymer-dot complexes appeared as relatively well-defined
clusters, QDs being surrounded by a polymer layer with thickness 3-10 nm. The size of the primary clusters was
in the range 60-500 nm. The polymerization and filtration process (0.1 μm pores) involved a diminution of the clusters
size in the range of 18-65 nm, and moreover, by a subsequent dialyses process the cluster size decreased to 5-15 nm.
Despite of the fact that in the last years a significant effort have been devoted to pulsed laser ablation (PLA), the problem of micro and nanoparticles have not been unambiguous presented (to our knowledge). In this work, we studied the size, size distribution and structure of the particles produced by laser ablation and luminescence as well. Scanning and transmission electron microscopy, X-ray diffraction and optical spectroscopy have been used. The investigations were made on Si/SiO2 nanopowders as produced, without any post-treatment (chemical, thermal, etc.). The experimental parameters were: silicon target, laser wavelength 355/532 nm, pulse duration 5 ns, repetition rate 10 Hz, fluence 4-8 J/cm2, argon/helium, 250-550 mbar, flow rate 1 l/min. Our investigations have shown that the particles are distributed in two main classes: one, with the size 0.1-1 μm, and the other with the diameter less than 14 nm. Our evaluation for optimal experimental conditions shown that around 78% (vol.) of particles are < 10 nm and almost 50% have diameters in the range 2-5 nm. The photo and cathodoluminescence were in the range 400-1000 nm, with main peak at 690-725 nm.
We have investigated thin films of Ni, Pt, Pd, Ni-Pt and Ni-Pd deposited by pulsed laser ablation. Our study was focused on the correlation of layer morphology and composition vs. synthesis parameters (material, laser fluence and wavelength). In order to obtain bimetallic films we alternatively irradiated two different metal targets. A Nd:YAG laser (λ = 355 and 532 nm, 5 ns pulse duration, fluence 15 - 30 J/cm2) was used. Film analysis was made by AFM and RBS. The synthesized layers had a roughness (Ra) between 15 and 40 nm for Pt and Pd and between 80 and 120 nm for Ni. The rate deposition was in the range of 0.04 - 0.8 Å. In the composite layers, in condition of equally radiated targets, the Ni/Pd at. concentration was 50/50%, while for the Ni/Pt layer was 30/70%.