A. Evelyn Di Mauro

Selective confinement of oleylamine capped Au nanoparticles in self-assembled PS-b-PEO diblock copolymer templates

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.

Polyelectrolyte multilayers as a platform for luminescent nanocrystal patterned assemblies.

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.

Effect of ultrasound on the function and structure of a membrane protein: The case study of photosynthetic Reaction Center from Rhodobacter sphaeroides

Ultrasounds are used in many industrial, medical and research applications. Properties and function of proteins are strongly influenced by the interaction with the ultrasonic waves and their bioactivity can be lost because of alteration of protein structure. Surprisingly, to the best of our knowledge no study was carried out on Integral Membrane Proteins (IMPs), which are responsible for a variety of fundamental biological functions. In this work, the photosynthetic Reaction Center (RC) of the bacterium Rhodobacter sphaeroides has been used as a model for the study of the ultrasound-induced IMP denaturation. Purified RCs were suspended in i) detergent micelles, in ii) detergent-free buffer and iii) reconstituted in liposomes, and then treated with ultrasound at 30W and 20kHz at increasing times. The optical absorption spectra showed a progressive and irreversible denaturation in all cases, resulting from the perturbation of the protein scaffold structure, as confirmed by circular dichroism spectra that showed progressive alterations of the RC secondary structure. Charge recombination kinetics were studied to assess the protein photoactivity. The lifetime for the loss of RC photoactivity was 32min in detergent micelles, ranged from 3.8 to 6.5min in the different proteoliposomes formulations, and 5.5min in detergent-free buffer. Atomic force microscopy revealed the formation of large RC aggregates related to the sonication-induced denaturation, in agreement with the scattering increase observed in solution.

Morphological Study of CdSe Nanocrystals Passivated with a Low Band Gap Rod-Coil Diblock Copolymer for Hybrid Solar Cells

Different nanocomposite materials consisting of semiconducting CdSe nanocrystals (NCs) and a low band gap copolymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b:3.4-b’]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) were prepared, morphologically characterized, and tested in hybrid solar cells. In addition, a PCPDTBT-based rod-coil diblock copolymer was synthesized through a grafting-onto approach and a preliminary evaluation of the morphology of the hybrid nanocomposites with CdSe NCs was performed.

H-bonding driven assembly of colloidal Au nanoparticles on nanostructured poly(styrene-b-ethylene oxide) block copolymer templates

A facile, cost-effective, and general solution-based “bottom-up” method for nanopatterning dense arrays of colloidal Au nanoparticles (NPs) has been developed. The organization of the NPs has been successfully achieved onto a microphase-separated poly(styrene-block-ethylene oxide) (PS-b-PEO) block copolymer (BCP) thin film which acts as structural template. The NP assembly process occurs by incubating the BCP films in dispersions of the ex situ synthesized Au NPs, not requiring any chemical pre-treatment or activation step of the copolymer surface, and has demonstrated to be distinctively controlled by multiple, cooperative, and selective hydrogen bonding interactions between hydroxyl functionalities of the capping molecules coating the Au NP surface and the hydrophilic PEO block. The effect of incubation time and concentration of NPs on the selectivity of the assembly has been investigated by atomic force and scanning electron microscopy. The results show that the BCP pattern is preserved after decoration with the Au NPs. The fabricated nanopatterns are good candidates for nanostructure integration in sensing and optoelectronic applications, as well as in memory devices and photonic systems. Moreover, the proposed immobilization protocol represents a model system that can be extended to other NPs having different compositions and surface chemistries.