Matrix Assisted Formation of Ferrihydrite Nanoparticles in a Siloxane/Poly(Oxyethylene) Nanohybrid

Matrix-assisted formation of ferrihydrite, an iron oxide hydroxide analogue of the protein ferritin-core, in a sol-gel derived organic-inorganic hybrid is reported. The hybrid network (named di-ureasil) is composed of poly(oxyethylene) chains of different average polymer molecular weights grafted to siloxane domains by means of urea cross-linkages and accommodates ferrihydrite nanoparticles. Magnetic measurements, Fourier transform infrared and nuclear magnetic resonance spectroscopy reveal that the controlled modification of the polymer molecular weight allows the fine-tuning of the ability of the hybrid matrix to assist and promote iron coordination at the organic-inorganic interface and subsequent nucleation and growth of the ferrihydrite nanoparticles whose core size (2-4 nm) is tuned by the amount of iron incorporated. The polymer chain length, its arrangement and crystallinity, are key factors on the anchoring and formation of the ferrihydrite particles.Comment: 7 pages, 6 figures. To be published in J. Mater. Che

Ionic and conformational mobility in poly(vinylidene fluoride)/ionic liquid blends: Dielectric and electrical conductivity behavior

[EN] The glass transition dynamics and the charge transport for blends composed of poly(vinylidene fluoride) (PVDF) and the ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, [Emim] [TESI] have been investigated as a function of different IL content (0, 10, 25 and 40 % wt) by differential scanning calorimetry (DSC), dynamic-mechanical analysis (DMA) and broadband dielectric relaxation spectroscopy (BDS) in wide frequency and temperature ranges (0.1 Hz-1 MHz and -120 to 150 degrees C, respectively). The inclusion of the IL in the polymer matrix affected the main relaxation process (beta-relaxation) of the amorphous phase of the polymer matrix detected with all the techniques employed. It is demonstrated, that the chain segments of PVDF and the IL are mixed at the nanometer range. The blends were homogeneous regardless of the amount of IL and the glass transition temperature (Tg) shifted to lower temperatures as the IL content was increased. A good agreement between the Tg measured by BDS and DSC was observed for all PVDF/IL samples. The conductivity formalism revealed significant contributions of the IL concentration to the conductivity behavior of the blends in that is described by charge motion and electrode polarization effects. The activation energy of all the PVDF/IL samples, calculated by Dyre model, decreased with IL addition with respect to that of neat PVDF. (C) 2018 Elsevier Ltd. All rights reserved.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013. The authors thank FEDER funds through the COMPETE 2020 Programme and National Funds through FCT under the projects PTDC/CTM-ENE/5387/2014, PTDC/EEI-SII/5582/2014 and UID/CTM/50025/2013 and Grants SFRH/BPD/121526/2016 (D.M.C.), SFRH/BPD/112547/2015 (C.M.C.). Financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including the FEDER financial support) and from the Basque Government Industry Department under the ELKARTEK and HAZITEK programs is also acknowledged. CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER Actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund.Correia, D.; Sabater I Serra, R.; Gómez-Tejedor, JA.; De Zea Bermudez, V.; Andrio Balado, A.; Meseguer Dueñas, JM.; Gómez Ribelles, JL.... (2018). Ionic and conformational mobility in poly(vinylidene fluoride)/ionic liquid blends: Dielectric and electrical conductivity behavior. Polymer. 143:164-172. https://doi.org/10.1016/j.polymer.2018.04.019S16417214

Highly conducting bombyx mori silk fibroin-based electrolytes incorporating glycerol, dimethyl sulfoxide and [Bmim]PF6

Green, transparent and flexible electrolyte films composed of a Bombyx mori silk fibroin (SF) host biopolymer doped with glycerol (G), dimethyl sulfoxide (DMSO, D) and 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6) ionic liquid (IL), were synthesized. The materials were represented by the notation SF@GD@ILx (x = 15, 20 and 30 is the mass ratio of SF/[Bmim]PF6 in %). SF@, SF@G, SF@D and SF@GD samples were also prepared. DMSO was found to play a dual-role, acting as solvent of [Bmim]PF6, and enhancing ionic conductivity. DMSO, alone or combined with [Bmim]PF6, led to the increase of the mean roughness and induced the formation of more ordered Silk II conformations (beta-sheets). No structural modifications were detected in the SF@GD@ILx samples upon increasing the temperature up to 100 degrees C. The highest ionic conductivity was exhibited by the IL-rich sample SF@GD@IL30 (1.07 and 4.61 mS cm(-1), at 22 and 100 degrees C, respectively). In the [Bmim]PF6-doped electrolytes "free" and coordinated PF6- ions coexist. The weight losses occurring below 200 degrees C involved essentially the release of adsorbed water and DMSO. The suitable mechanical properties, high ionic conductivity and good electrochemical stability suggest that these electrolytes are attractive candidates for application in electrochemical devices.Veronica de Zea Bermudez would like to express her gratitude to Professor Michel Armand who, during her PhD thesis at Grenoble (1989-1992), was an endless source of ideas that made her work productive and stimulating. His qualities, as an inspiring and extraordinary scientist, equal his kindness, generosity and great heart. This work was supported by National funds by Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/QUI/00686/2018, UID/QUI/00686/2019, UID/QUI/50006/2019 and UID/QUI/00313/2020. The authors thank FEDER funds through the COMPETE 2020 Program and National Funds through FCT under the projects PEst-OE/QUI/UI0616/2014, LUMECD (POCI-01-0145-FEDER-016884 and PTDC/CTMNAN/0956/2014), UniRCell (POCI-01-0145-FEDER-016422 and SAICTPAC/0032/2015), PORPLANTSURF (POCI-01-0145FEDER-029785 and PTDC/CTM-REF/29785/2017), and NORTE01-0145-FEDER-030858. R.F.P.P thanks FCT-UM for the researcher contract in the scope of Decreto-Lei 57/2016 and 57/2017. H.M.R. Goncalves was funded by PTDC/BTM-MAT/30858/2017

Electrochromic device composed of a Di-Urethanesil electrolyte incorporating lithium triflate and 1-Butyl-3-Methylimidazolium chloride

A di-urethane cross-linked poly(oxyethylene)/silica hybrid matrix [di-urethanesil, d-Ut(600)], synthesized by the sol-gel process, was doped with lithium triflate (LiCF3SO3) and the 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) ionic liquid. The as-produced xerogel film is amorphous, transparent, flexible, homogeneous, hydrophilic, and has low nanoscale surface roughness. It exhibits an ionic conductivity of 3.64 x 10(-6) and 5.00 x 10(-4) S cm(-1) at 21 and 100 degrees C, respectively. This material was successfully tested as electrolyte in an electrochromic device (ECD) with the glass/ITO/a-WO3/d-Ut(600)(10)LiCF3SO3[Bmim]Cl/c-NiO/ITO/glass configuration, where a-WO3 and c-NiO stand for amorphous tungsten oxide and crystalline nickel oxide, respectively. The device demonstrated attractive electro-optical performance: fast response times (1-2 s for coloring and 50 s for bleaching), good optical memory [loss of transmittance (T) of only 41% after 3 months, at 555 nm], four mode modulation [bright mode (+3.0 V, T = 77% at 555 nm), semi-bright mode (-1.0 V, T = 60% at 555 nm), dark mode (-1.5 V, T = 38 % at 555 nm), and very dark mode (-2.0 V, T = 11% and -2.5 V, T = 7% at 555 nm)], excellent cycling stability denoting improvement with time, and high coloration efficiency [CEin = -6727 cm(2) C-1 (32th cycle) and CEout = +2794 cm(2) C-1 (480th cycle), at 555 nm].The authors are grateful to Fundacao para a Ciencia e a Tecnologia (FCT) and when applicable by FEDER under the PT2020 Partnership Agreement for financial support under contracts PEst-OE/SAU/UI0709/2014, UID/Multi/00709/2013, UID/QUI/00686/2016, UID/QUI/00686/2018, UID/QUI/00686/2019, PEst-OE/QUI/UI0616/2016, FCOMP-01-0124-FEDER037271, UID/CTM/50011/2013, LUMECD project (POCI01-0145-FEDER-016884 and PTDC/CTM-NAN/0956/2014), UniRCell project (SAICTPAC/0032/2015 and POCI-01-0145FEDER-016422). RP and SN acknowledge FCT-MCTES for grants (SFRH/BPD/87759/2012 and LUMECD, respectively). RP thanks FCT-UM for the contracts in the scope of Decreto-Lei 57/2016 and 57/2017. MF acknowledges FCTUTAD for the contract in the scope of Decreto-Lei 57/2016 -Lei 57/2017. HG acknowledges projects POCI-010145-FEDER-030858 and PTDC/BTM-MAT/30858/2017 for financial support

Cationic and anionic environments in mono-urethanesil hybrids doped with magnesium triflate

Sol–gel derived poly(oxyethylene), POE/siloxane hybrids (mono-urethanesils) with a wide range of magnesium triflate (Mg(CF₃SO₃)₂) concentrations were analyzed by infrared and Raman spectroscopies with the goal of examining the cation/polymer, cation/cross-link, hydrogen bonding and cation/anion interactions. In the host matrix of these xerogels short CH₃-terminated POE segments are covalently bonded to the siliceous backbone through urethane linkages. Samples with ∞>n≥6 (where n is the molar ratio of (OCH₂CH₂) moieties per Mg²⁺ ion) were synthesized. The spectral data obtained provided conclusive evidence that the ether oxygen atoms of the polymer chains of the host structure complex the alkaline-earth ions in materials with n≤60. "Free" triflate ions and weakly coordinated anions were detected over the whole range of salt concentration examined. The coordinated triflate species are formed in two different bonding environments. Contact ion pairs appear in materials with n≤60. This work confirms previous studies that suggested that the nature of the cations added to the mono-urethanesil-type framework plays a key-role in the properties of these composites

Photoluminescent lamellar bilayer mono-alkyl-urethanesils

A new family of lamellar bilayer hierarchically structured mono-urethane cross-linked alkyl/siloxanes designated as mono-alkyl-urethanesils and represented by the notation m-Ut(CY)-ac, with Y = 14, 16 and 22 (where Y is the number of carbon atoms of the pendant polymer chains and ac is acid catalyzed) was prepared by the sol-gel process and self-assembly routes. The compounds were obtained as solid powders and are thermally stable up to 250 A degrees C. The alkyl chains adopt essentially all-trans conformations and are interdigitated. The degree of interpenetration depends non-linearly on the chain length. The intrincate morphology of the samples mimicks cabbage leaves or the desert rose. The present system allowed us to conclude that the nature of the cross-link exerts a key role on the properties of this sort of silsesquioxanes. The hydrogen bonded array in the mono-alkyl-urethanesils is considerably weaker than that formed in the analogue mono-amidosil m-A(14) incorporating alkyl chains with 15 carbon atoms. The order/disorder phase transition temperatures of the mono-alkyl-urethanesils with Y = 14 and 16 are lower than that of m-A(14), making the former samples mechanically more resistant to consecutive heating/cooling cycles. The frequency of conformational-sensitive infrared modes of m-Ut(C16)-ac exhibit hysteresis behaviour during cooling after undergoing the order/disorder phase transition, but, unlike m-A(14), the latter transition, although reversible, is apparently time-independent. The hybrids display an efficient emission at room temperature in the blue-green spectral region with a maximum emission quantum yield value of 0.11 +/- A 0.01 (excited at 350-380 nm), which is of the same order of magnitude of that reported for m-A(14)

Luminescent solar concentrators: challenges for lanthanide-based organic-inorganic hybrid materials

Luminescent solar concentrators (LSCs) are devices comprising a transparent matrix embedding optically active centres that absorb the incident radiation, which is re-emitted at a specific wavelength and transferred by total internal reflection to photovoltaic (PV) cells located at the edges of the matrix. Organic-inorganic hybrids incarcerating trivalent lanthanide ions (Ln(3+)) are a very promising class of materials for addressing the required challenges in the LSC design to improve solar energy harvesting and, then, PV energy conversion. This feature article offers a general overview of the potential of down-shifting-based Ln(3+)-containing organic-inorganic hybrids for the development of the area with special focus on (i) optically active layer design, (ii) energy conversion mechanisms, (iii) performance and geometry and (iv) figures of merit in PV cell enhancement. Finally, a prospective outlook on future progress, e.g. optically active centre alignment, geometry optimization and building integration, is provided. The use of Ln(3+)-containing hybrids in LSCs is at an infant initial research step and considerable basic knowledge is still needed to enable prototypes to become a commercial reality

Silk fibroin separators: A step toward lithium-ion batteries with enhanced sustainability

Battery separators based on silk fibroin (SF) have been prepared aiming at improving the environmental issues of lithium-ioh, batteries. SF materials with three different morphologies were produced: membrane films (SF-F), sponges prepared by lyophilization (SF-L) and: electrospuri membranes (SF-E). The latter Materials presented a suitable porons,three-dimensional microstructure and were soaked with a I M LiPF6 electrolyte: The ionic conductivities for SF-L and SF-E were 1.00 and 0.32 mS cm(-1) at 20 degrees C, respectively. A correlation between the fraction "of beta-sheet conformations and the ionic conductivity was observed. The electrochemical performance of the SF-based materials was evaluated by incorporating them in cathodic half-cells with C-LiFePO4. The discharge capacities of SF-L and SF-E were 126 and 108 mA h g(-1), respectively, at the C/Iirate and 99 and 54 mA h g(-1), respectively, at the 2C-rate. Furthermore, the capacity retention and capacity fade of the SF-L membrane after 50 cycles at the 2C-rate were 72 and 5%, respectively. These electrochemical results show that a high percentage of beta-sheet conformations, were of prime importance to guarantee excellent cycling performance. This work demonstrates that SP-based membranes are appropriate separators for the production of environmentally friendlier lithium-ion batteries.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013, ULD/QUI/00686/2013 and ULD/QUI/00686/2016. The authors thank FEDER funds through the COMPETE 2020 Programme and National Funds through FCT under the projects PTDC/CTM-ENE/5387/2014 and UID/CTM/50025/2013, PEst-OE/QUI/UI0616/2014, and LUMECD (POCI-01-0145-FEDER-016884 and PTDC/CTM-NAN/0956/2014), grants SFRH/BPD/87759/2012 (R.F.P.P.), and SFRH/BPD/112547/2015 (C.M.C.). The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry Department under the ELKARTEK program.info:eu-repo/semantics/publishedVersio

Transparent luminescent solar concentrators using Ln3+-based ionosilicas towards photovoltaic windows

The integration of photovoltaic (PV) elements in urban environments is gaining visibility due to the current interest in developing energetically self-sustainable buildings. Luminescent solar concentrators (LSCs) may be seen as a solution to convert urban elements, such as façades and windows, into energy-generation units for zero-energy buildings. Moreover, LSCs are able to reduce the mismatch between the AM1.5G spectrum and the PV cells absorption. In this work, we report optically active coatings for LSCs based on lanthanide ions (Ln3+ = Eu3+, Tb3+)-doped surface functionalized ionosilicas (ISs) embedded in poly(methyl methacrylate) (PMMA). These new visible-emitting films exhibit large Stokes-shift, enabling the production of transparent coatings with negligible self-absorption and large molar extinction coefficient and brightness values (~2 × 105 and ~104 M−1∙cm−1, respectively) analogous to that of orange/red-emitting organic dyes. LSCs showed great potential for efficient and environmentally resistant devices, with optical conversion efficiency values of ~0.27% and ~0.34%, respectively.publishe

Coordination polymers based on a glycine-derivative ligand

The combination of the glycine-derivative supramolecular salt 4,6-bis(carboxymethylamino)-2-oxo-2,3-dihydro-1,3,5-triazin-1-ium chloride (H(2)bodt center dot HCl) and lanthanide(III) chloride hydrates under hydrothermal conditions (120 degrees C, 48 h) led to the formation of a family of isotypical materials formulated as [Ln(bodt)(Hbodt)] [where Ln(3+) = La3+ (1), (La0.95Eu0.05)(3+) (2) and (La0.95Tb0.05)(3+) (3)]. The synthesis of the novel precursor H(2)bodt center dot HCl is detailed. The structures of H(2)bodt center dot HCl and its intermediate compound were unveiled by single-crystal X-ray diffraction and characterized by standard liquid-state techniques. The crystallographic details of compound 1 were unveiled in the monoclinic P2/c space group by using single-crystal X-ray diffraction, with the crystal structure of 1 comprising a one-dimensional (1)(infinity)[La(bodt)(Hbodt)] coordination polymer. All polymeric materials were fully characterized by FT-IR, electron microscopy (SEM and EDS), powder X-ray diffraction, and elemental and thermogravimetric analyses. The photoluminescent properties of 1 and of the mixed-lanthanide materials 2 and 3 were investigated at ambient and low temperatures. An excited-state intermolecular proton transfer (ESPT) process, induced by intermolecular hydrogen-bonding interactions, is proposed to account for the observed anomalous emission and excitation spectra of 1. Aiming at providing an in-depth understanding of the emission (fluorescence and phosphorescence) properties of the ligand, time-dependent density functional theory (TD-DFT) calculations were also performed