Organic-Inorganic Hybrid Material

The aim of this publication is to present a general strategy to engineer more efficient photoluminescent dendritic molecules based on polyhedral oligomeric silsesquioxane (POSS) cores. A series of chromophores were grafted
on POSS cores to form dendritic molecules for which steric hindrance was used as a trigger to tune their photophysical properties. For fluorescence in the blue/near-UV spectral ranges, 4-vinylbiphenyl molecules were chosen as model chromophores to present a general approach based on stable chemistry and bulky groups grafted to the chromophores to enhance photoluminescence efficiency of the dendritic molecules.
Photoluminescence quantum yields as well as steady-state and time-resolved solution spectroscopy along with molecular dynamics investigation and electronic structure calculations on a family of new materials are reported. We highlight an apparent contrast between free chromophore and dendritic molecules photophysical properties and show that chromophores’ engineering and confinement around an inorganic core allows the design of more efficient photoluminescent dendritic molecules relevant to sensors and hybrid light-emitting diodes.

A nanoscopic scale organic/inorganic hybrid Field Effect Transistor created by Pulsed Laser Deposition or Molecular Beam Epitaxy, with layers sized as a single (4 nm), double (8 nm) or quadruple (16 nm) cristal lattice. Surfaces tested with Scanning Electron Microscope, X-ray diffraction and Atomic Force Microscope.

The sensing parameters of previously reported PFO-DBT:MEH-PPV:PC71BM ternary blend-based organic photodetector have been improved in the present study. Improvement has been successfully demonstrated by doping TiO2 nanoparticles in the PEDOT:PSS thin film. TiO2 nanoparticles of 50, 100 and 250 nm diameters have initially been dispersed in PEDOT:PSS, and the resulting suspension has been spun coated on glass substrates and subjected to UV/vis and PL study. Thin film of PEDOT:PSS–TiO2 (100 nm) has shown maximum quenching in PL spectra, along with fairly good visible-light absorption. For further studies, 5 wt% TiO2 (100 nm) nanoparticles dispersion in PEDOT:PSS has been utilized for the fabrication of ITO/PEDOT:PSS–TiO2/PFO-DBT:MEH-PPV:PC71BM/Al photodiode. The PEDOT:PSS–TiO2 suspension has been spun coated onto the ITO substrates primarily and annealed to densify the film by vaporizing water contents in the film. A ternary blend of PFO-DBT:MEH-PPV:PC71BM in optimized volumetric ratio has been sequentially spun-cast to serve as a photoactive film. Significantly improved values of the sensing parameters such as responsivity (4 mA/W) and photo-to-dark current ratio (~6.4 × 104) have also been found. Response/recovery times of the fabricated sensor remain almost the same (<1 s) as previously reported for PFO-DBT:MEH-PPV:PC71BM ternary blend.

Nome: centrocongressiunical password: unical72 IX Congresso Nazionale AIAr Un ponte tra Arte e Scienza: passato, presente e prospettive future Arcavacata di Rende 9-11 Marzo 2016 Mercoledì 9 marzo 8.(a)TecnArt S.r.l. e INFN Torino,(b)Univ. di Torino e INFN Torino,(c)Univ. di Firenze (d)INFNFirenze, (e)WoodIdLab,Torino,(f)Sopr. per i beni e le attività culturali, Patrimonio archeologico, Valle d'Aosta, (g)Archeos S.a.s., Aosta 12.00-12.20

Heavy metal toxicity and device instability are prominent limitations in the push for commercialization of photovoltaics based on low-cost, solution-processed materials. In this study, a hybrid organic–inorganic material containing trivalent bismuth and dicationic 1,6-hexanediammonium was used as the photoactive layer in solution-processed photovoltaics. These proof-of-concept photovoltaics demonstrated a stable open-circuit photovoltage of 384 ± 12 mV and steady-state short-circuit photocurrent density of 0.101 ± 0.020 mA cm−2. In comparison to the widely studied lead-halide-based perovskites, the bismuth-based materials had superior coverage on mesoporous TiO2 layers as determined by scanning electron microscopy. Moreover, thermal stability tests demonstrated that these bismuth-based materials were more stable at higher temperatures than comparable lead-based materials.

The formamidinium lead iodide hybrid perovskite is studied using first principles molecular dynamics simulations and further analyzed using group theory. The simulations are performed on large supercells containing 768 atoms under isothermal and fully anisotropic isobaric conditions. Two trajectories, one at 300 K and another at 450 K, were extended for over 50 ps in order to perform a detailed assessment of the rotational dynamics of organic cations. The characteristic rotations of the cation are analyzed by defining two rotation axes. It is found that the formamidinium molecules rotate preferentially around the direction parallel to the line connecting the two nitrogen atoms. The rotational dynamics shows some characteristics already observed in methylammonium lead iodide, like the heterogeneous dynamics at room temperature that disappears at 450 K. The orientational probability of the molecules is explored in terms of an expansion in cubic harmonics up to the 12th order. It reveals a strong directionality at room temperature that relaxes when increasing the temperature. These findings are further rationalized using Landau and group theories suggesting a mixed displacive/order–disorder structural instability at lower temperatures.

A new [P 2 V 3 W 15 O 62 ] 9− cluster based covalent polyoxometalate-organic hybrid (P1) containing a naphthol-amide-Tris derivative has been synthesized and characterized using standard analytical and spectroscopic techniques including single crystal X-ray diffraction analyses. P1 exhibits interesting self-assembly behaviour leading to the generation of ~200 nm spherical aggregates in solutions as revealed by DLS and TEM analyses. Standard in vitro experiments revealed that P1 is capable of exhibiting moderate antioxidant properties under standard experimental conditions.

A polyhedral oligomeric silsesquioxane (POSS) has been decorated with eight peripheral 40-vinylbiphenyl-3,5-dicarbaldehyde groups. Although this macromolecule is not fluorescent, reducing agents such as NaBH4 and LiAlH4 activate its fluorescence by turning the aldehydic functions into primary alcohols. Molecular dynamics calculations demonstrated similar spherical structures for both macromolecules regardless of whether the terminal functions were aldehyde or alcohol.

Organic-inorganic hybrids composed of polyfluoroalkyl azobenzene surfactant (abbreviated as C3F-Azo-C6H) and inorganic layered compounds are able to undergo reversible three-dimensional morphology changes such as interlayer space changes and nanosheet sliding in a giant scale due to reversible trans-cis isomerization of the azobenzene moiety upon photo-irradiation. In this paper, we have systematically studied the relationship between the layered hybrid microstructures of C3F-Azo-C6H-clay and their photoreactivity for understanding the mechanism of the photo-induced morphology change. The photoreactivity was found to be very much affected by the surrounding microenvironments. As compared with it in solution, the cis-trans photo-isomerization in C3F-Azo-C6H-clay nano-layered film was substantially enhanced with the quantum yield exceeding unity (F = 1.9), while the trans-cis isomerization was rather retarded. The corresponding hydrocarbon analogue of the azobenzene surfactant (C3H-Azo-C6H) did not show such an enhancement. The enhancement was discussed in terms of a cooperative effect among adjacent azobenzene moieties along with polyfluoroalkyl chains and the inorganic clay nanosheet to prevent a dissipation of the excess energy being liberated during the photo-isomerization within the nano-layered microenvironment.

Grubbs cross-metathesis has been used to functionalize octavinylsilsesquioxane with fluorescent vinylbiphenyl-modified chromophores to design new hybrid organic-inorganic nanomaterials. Those macromolecules have been characterized by NMR, microanalyses, MALDI-TOF mass spectrometry and photoluminescence. This last method was shown to be an interesting tool in the analysis of the purity of the cube derivatives.