Self-Standing 3D-Printed PEGDA-PANIs Electroconductive Hydrogel Composites for pH Monitoring.

Additive manufacturing (AM), or 3D printing processes, is introducing new possibilities in electronic, biomedical, sensor-designing, and wearable technologies. In this context, the present work focuses on the development of flexible 3D-printed polyethylene glycol diacrylate (PEGDA)- sulfonated polyaniline (PANIs) electrically conductive hydrogels (ECHs) for pH-monitoring applications. PEGDA platforms are 3D printed by a stereolithography (SLA) approach. Here, we report the successful realization of PEGDA-PANIs electroconductive hydrogel (ECH) composites produced by an in situ chemical oxidative co-polymerization of aniline (ANI) and aniline 2-sulfonic acid (ANIs) monomers at a 1:1 equimolar ratio in acidic medium. The morphological and functional properties of PEGDA-PANIs are compared to those of PEGDA-PANI composites by coupling SEM, swelling degree, I-V, and electro-chemo-mechanical analyses. The differences are discussed as a function of morphological, structural, and charge transfer/transport properties of the respective PANIs and PANI filler. Our investigation showed that the electrochemical activity of PANIs allows for the exploitation of the PEGDA-PANIs composite as an electrode material for pH monitoring in a linear range compatible with that of most biofluids. This feature, combined with the superior electromechanical behavior, swelling capacity, and water retention properties, makes PEGDA-PANIs hydrogel a promising active material for developing advanced biomedical, soft tissue, and biocompatible electronic applications.

Ultrafast optical spectroscopy of semiconducting and plasmonic nanostructures and their hybrids.

The knowledge of the carrier dynamics in nanostructures is of fundamental importance for the development of (opto)electronic devices. This is true for semiconducting nanostructures as well as for plasmonic nanoparticles (NPs). Indeed, improvement of photocatalytic efficiencies by combining semiconductor and plasmonic nanostructures is one of the reasons why their ultrafast dynamics are intensively studied. In this work, we will review our activity on ultrafast spectroscopy in nanostructures carried out in the recently established EuroFEL Support Laboratory. We have investigated the dynamical plasmonic responses of metal NPs both in solution and in 2D and 3D arrays on surfaces, with particular attention being paid to the effects of the NP shape and to the conversion of absorbed light into heat on a nano-localized scale. We will summarize the results obtained on the carrier dynamics in nanostructured perovskites with emphasis on the hot-carrier dynamics and in semiconductor nanosystems such as ZnSe and Si nanowires, with particular attention to the band-gap bleaching dynamics. Subsequently, the study of semiconductor-metal NP hybrids, such as CeO2-Ag NPs, ZnSe-Ag NPs and ZnSe-Au NPs, allows the discussion of interaction mechanisms such as charge carrier transfer and Förster interaction. Finally, we assess an alternative method for the sensitization of wide band gap semiconductors to visible light by discussing the relationship between the carrier dynamics of TiO2 NPs and V-doped TiO2 NPs and their catalytic properties.

A Study of Photoinduced Coherent Vibrations in Gold-Nanorod Dispersions.

Upon photoexcitation with a femtosecond laser pulse, the plasmonic resonance of a nanorod can couple with coherent vibrational modes generating a regular oscillating pattern in the transient absorbance of the nanostructure. The dynamics of the plasmon resonances of these materials are probed through femtosecond transient absorption spectroscopy in the spectral region between 400 nm and 1600 nm. Whereas in the visible range the spectra are comparable with the findings reported in the literature, the analysis of the transient NIR spectra revealed that their oscillation frequencies vary with wavelength, resulting in a strong distortion of the transient features that can be related to the specific lengths distribution of the nanorods contained in the sample. These findings suggest that in the design of efficient and highly sensitive gold-nanorod based plasmonic sensors a narrow size distribution of nanostructures is required.

Gold nanoparticles functionalized by rhodamine B isothiocyanate: A new tool to control plasmonic effects.

Gold nanoparticles with an average diameter of 10 nm, functionalized by the dye molecule rhodamine B isothiocyanate, have been synthesized. The resulting material has been extensively characterized both chemically, to investigate the bonding between the dye molecules and the nanoparticles, and physically, to understand the details of the aggregation induced by interaction between dye molecules on different nanoparticles. The plasmonic response of the system has been further characterized by measurement and theoretical simulation of the static UV-Vis extinction spectra of the aggregates produced following different synthesis procedures. The model parameters used in the simulation gave further useful information on the aggregation and its relationship to the plasmonic response. Finally, we investigated the time dependence of the plasmonic effects of the nanoparticles and fluorescence of the dye molecule using an ultrafast pump-probe optical method. By modulating the quantity of dye molecules on the surface of the nanoparticles it was possible to exert fine control over the plasmonic response of nanoparticles.

Carbon nanotubes/polydimethylsiloxanes systems for thermal management of miniaturized electronic components.

The thermal performances of nanocomposite layers formed by Single-walled Carbon Nanotubes (SWCNT) dispersed in 2 different kind of polydimethyl-siloxane (PDMSO) matrices has been investigated by measuring the thermal resistance under conditions similar to the ones used for thermal management in microelectronics. A series of nanocomposite samples with thickness in the range 25 microm(-1) cm have been tested. The nanocomposites were prepared varying the amounts of nanotubes embedded in the matrix (from 0.1 to 5%w). In some cases also microsized graphites were mixed to the nanotube's fillers. For 25 micron thick layers, the thermal resistance of the neat silicone specimen can be reduced of 54% with the addition of 2%w carbon nanotubes. The variation of thermal conductivity as a function of the SWCNT's loading is reported and discussed. Furthermore the dispersion's effects of the nanotubes in the layers and the effects on the realization of a net-like system have been investigated.