Metal nanoclusters (NCs), consisting of a few to few hundred atoms with dimensions comparable to Fermi wavelength of electrons, exhibit significant molecular behavior. As a result of quantum confinement effect, electrons which freely move in bulk metals become confined to the spaces that can be as small as a few atom spacings. This confinement of electrons gives rise to unique properties such as discrete energy levels, strong photoluminescence, and considerable chemical reactivity. Therefore, synthesis of stable NCs could open the door to engineer novel nanomaterials with tunable characteristics with a potential for numerous scientific and industrial applications. However, NCs are not realized in practice as they are less stable than nanoparticles (NPs). Hence, using proper stabilizer matrices is a requirement for synthesis of NCs. NCs can be formed and stabilized in solutions by reducing dissolved metal ions in the presence of organic molecules such as proteins, and polymers. Moreover, direct laser writing (DLW) is shown to be a promising technique in fabrication and stabilization of metal NCs in polymer and glass matrices. In this thesis, we demonstrate the fabrication of highly fluorescent microstructures containing silver NCs in polyvinyl alcohol (PVA) thin films using DLW technique. Polymer thin films were prepared by spin-coating aqueous solutions of PVA containing silver nitrate on glass substrates. Single-photon DLW were performed on silver-polymer films by tightly focusing the continuous-wave (CW) laser beam of wavelength 405 nm, and scanning the sample against the constant laser beam. Photoluminescence of the structures, dependence of the fluorescence intensity on silver concentration and writing laser power, and photostability of the fabricated microstructures were studied by using different optical characterization methods. Atomic force microcopy (AFM) was used to estimate the thickness of the film, investigate the surface topology, and measure the line width of the written structures.The results showed broadband photostable fluorescence emissions from NCs at visible wavelengths. Dependence of the fluorescence intensity on silver concentration confirmed that the presence of silver in the polymer film is the cause of the bright luminescence. AFM analysis of the written structures depicted the formation of grooves with depths of 35 ± 3 nm in a thin film of 58 nm thickness. Moreover, it was observed that the breadth of the grooves, as well as the emitted fluorescence intensity, increased with the writing power. The silver NCs fabricated in this method were similar in character to NCs stabilized in organic solutions. Moreover, the results were consistent with those obtained from the silver NCs fabricated in Poly-methacrylic Acid (PMAA) films by using two-photon DLW technique. The outcomes of this work indicated that single-photon DLW can be a useful method to sythesize highly fluorescent metal NCs with any desired pattern in various kinds of polymer resins.
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