Carbon dots (C-dots) are emerging as new emitting nanomaterials for optoelectronics, bioimaging, and biosensing thanks to their high quantum yield (QY), biocompatibility, low toxicity, and cost-effective sources. Although the origin of their photoluminescence (PL) mechanism (i.e., their strong blue-green emission and excitation dependent fluorescence) is still controversial, it has been demonstrated to depend on the synthetic protocols and experimental conditions, able to modify the surface properties. Here oil-dispersible C-dots, synthesized by carbonization of citric acid in the presence of hexadecylamine in high boiling organic solvent, are thoroughly investigated by systematically controlling the synthetic reaction parameters. Similarly to what was found for water-soluble C-dots, citric acid in the presence of amine-containing passivating agents improves the PL emission of C-dots via the formation of molecular fluorescent derivatives alongside the carbonization process. We demonstrate that at growth temperature of 200 °C such C-dots exhibit an interesting and intense white emission, when excited in the blue region, thus resulting in a biocompatible colloidal white emitting single nano-objects. The incorporation of the nanoparticles in a poly­(methyl methacrylate) (PMMA) host matrix, to obtain free-standing nanocomposite films, is demonstrated not to affect the color point, which still falls in the white color region of the 1931 CIE diagram. Remarkably, the emission properties are retained even after several months of films exposure to air and sunlight, thus confirming the color stability of the nanoparticles against aging.

Amphiphilic polystyrene-block-polyethylene oxide (PS-b-PEO) block copolymers (BCPs) have been demonstrated to be effective in directing organization of colloidal Au nanoparticles (NPs). Au NPs have been incorporated into the polymer and the different chemical affinity between the NP surface and the two blocks of the BCP has been used as a driving force of the assembling procedure. The morphology of the nanocomposites, prepared and fabricated as thin films, has been investigated by means of atomic force and scanning electron microscopies as a function of the NP content and BCP molecular weight. NPs have been effectively dispersed in PS-b-PEO hosts at any investigated content (up to 17 wt%) and a clear effect of the BCP properties on the final nanocomposite morphology has been highlighted. Finally, electrostatic force microscopy has demonstrated the conductive properties of the nanocomposite films, showing that the embedded Au NPs effectively convey their conductive properties to the film. The overall investigation has confirmed the selective confinement of the as-prepared surfactant-coated metal NPs in the PS block of PS-b-PEO, thus proposing a very simple and prompt assembling tool for nanopatterning, potentially suitable for optoelectronic, sensing and catalysis applications.

As-synthesized organic-capped TiO2 nanorods were incorporated into polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer to achieve TiO2/PS-b-PMMA nanocomposites with enhanced optical and conductive properties. The specific surface chemistry of TiO2 nanorods derived from the colloidal synthetic approach allowed their prompt incorporation in the PS-b-PMMA block copolymer template up to 50 wt %, which resulted in films with an extended coverage of highly dispersed nanoparticles for contents higher than 30 wt %. At such high nanorod contents, the films fabricated by the prepared nanocomposites demonstrated enhanced optical properties. Atomic force microscopy investigation of the nanocomposite films showed a cylindrical morphology for low nanorod contents. Conversely, higher nanorod contents resulted upon removal of the organic component in the nanocomposites with UV treatment in overall nanorod coverage of the film surface with the concomitant formation of charge percolation paths, which led to noticeable conductivity values. EFM and PF-TUNA measurements confirmed the conductive properties of the composites at nanoscale, whereas semiconductor analyzer measurements provided their macroscale characterization. In addition, an increase in the UV-vis absorption was observed with the increase in the nanorod content along with a remarkable conductivity of the overall film.

The fabrication of uniform and patterned nanocrystal (NC) assemblies has been investigated by exploiting the possibility of carefully tailoring colloidal NC surface chemistry and the ability of polyelectrolyte (PE) to functionalize substrates through an electrostatic layer-by-layer (LbL) strategy. Appropriate deposition conditions, substrate functionalization, and post-preparative treatments were selected to tailor the substrate surface chemistry to effectively direct the homogeneous electrostatic-induced assembly of NCs. Water-dispersible luminescent NCs, namely, (CdSe)ZnS and CdS, were differently functionalized by (1) ligand-exchange reaction, (2) growth of a hydrophilic silica shell, and (3) formation of a hydrophilic inclusion complex, thus providing functional NCs stable in a defined pH range. The electrostatically charged functional NCs represent a comprehensive selection of examples of surface-functionalized NCs, which enables the systematic investigation of experimental parameters in NC assembly processes carried out by combining LbL procedures with microcontact printing and also exploiting NC emission, relevant for potential applications, as a prompt and effective probe for evaluating assembly quality. Thus, an ample showcase of combinations has been investigated, and the spectroscopic and morphological features of the resulting NC-based structures have been discussed.