[Show abstract][Hide abstract] ABSTRACT: Statement of significance:
The pharmacological activities of the flavonoid quercetin include anti-oxidant and antiinflammatory properties, as well as capability to prevent bone loss. In this paper, we demonstrate that it is possible to synthesize hydroxyapatite functionalized with different amounts of quercetin and obtain new composite materials which display both the good bioactivity of the inorganic phase and the therapeutic properties of the flavonoid. The innovative in vitro model developed in this study, which involves co-culture of osteoblast, osteoclast and endothelial cells, allows to state that the new materials exert a beneficial action onto bone repair microenvironment, stimulating osteoblast proliferation and activity, downregulating osteoclastogenesis, and supporting microangiogenetic processes necessary for new bone formation.
Full-text · Article · Dec 2015 · Acta biomaterialia
[Show abstract][Hide abstract] ABSTRACT: By the combination of prepolymers with very different physical/chemical properties, better performance materials can be obtained. In the present study, three hydroxyl-terminated fully aliphatic polyesters have been chain extended to prepare new multiblock poly(ester urethane)s (PEU) displaying thermoplastic elastomeric characteristics. Poly(butylene succinate), poly(1,4-cyclohexylenedimethylene-1,4-cyclohexanedicarboxylate), and poly(neopentyl glycol adipate) have been respectively used as soft-hard, hard and soft segment. The evaluation of molecular, thermal, and mechanical properties and hydrolytic degradation profile permitted to correlate the behavior of the so-obtained materials with their molecular structure, and highlighted that it is possible to nicely tune the final characteristics of this class of PEUs by just varying the mutual amount of the three segments.
[Show abstract][Hide abstract] ABSTRACT: This paper describes the electrosynthesis, characterization and electrocatalytic properties towards oxygen evolution reaction (OER) of four layered double hydroxides (LDHs) containing cobalt or nickel as divalent cation and aluminum or iron as trivalent metal. The electrochemical behaviour of the LDH modified electrodes was studied by cyclic voltammetry (CV), and the LDHs were characterized by XRD and SEM/EDS. Two materials, i.e., platinum and glassy carbon (GC), were investigated as electrode supports recording polarization and chronopotentiometric curves, with a rotating disk electrode in alkaline solutions. LDHs containing iron exhibited higher activity for OER and all the materials showed a good stability and durability in alkaline media. When GC was used as electrode support the performances of the OER catalysts resulted to be even better than those exhibited by the same LDHs electrodeposited on Pt.
[Show abstract][Hide abstract] ABSTRACT: Highly soluble air-stable conjugated decamers and polymers (compounds 1-6) with alternating "sulfur-overrich" bis(3,4′-S-alkyl)-2,2′-bithiophenes as the donor units and 2,1,3-benzothiadiazoles as the acceptor units were designed and expediently synthesized with the aid of microwave and ultrasound enabling technologies. Solid-state cyclovoltammetry showed that 1-6 had oxidation and reduction potentials in the range 0.6-0.9 V and -1/-1.2 V (vs SCE), respectively, with energy gaps below 2 eV. The electronic properties of spin-coated films of pure 1-6 were investigated with nanoscale resolution by Kelvin probe force microscopy (KPFM). KPFM measurements showed that charge generation and separation were obtained for all films under illumination. Consequently, 1-6 were tested on single-material organic solar cells (SMOCs). In agreement with KPFM results, photovoltaic behavior was observed for all compounds with power conversion efficiencies in line with the best results obtained so far for the few donor-acceptor molecules already shown to perform in single-component solar cells. To our knowledge, this is the first time in which thiophene-benzothiadiazole co-oligomers and copolymers are shown to be photoactive materials in SMOCs.
Full-text · Article · Nov 2015 · The Journal of Physical Chemistry C
[Show abstract][Hide abstract] ABSTRACT: We investigated the influence of surfaces in the formation of different crystal structures of a spin crossover compound, namely [Fe(L)2] (LH: (2-(pyrazol-1-yl)-6-(1H-tetrazol-5-yl)pyridine), which is a neutral compound thermally switchable around room temperature. We observed that the surface induces the formation of two different crystal structures, which exhibit opposite spin transitions, i.e. on heating them up to the transition temperature, one polymorph switches from high spin to low spin and the second polymorph switches irreversibly from low spin to high spin. We attributed this inversion to the presence of water molecules H-bonded to the complex tetrazolyl moieties in the crystals. Thin deposits were investigated by means of polarized optical microscopy, atomic force microscopy, X-ray diffraction, X-ray absorption spectroscopy and micro Raman spectroscopy; moreover the analysis of the Raman spectra and the interpretation of spin inversion were supported by DFT calculations.
No preview · Article · Nov 2015 · Dalton Transactions
[Show abstract][Hide abstract] ABSTRACT: Literature values of the enthalpy of melting (Δhm°) of 100% crystalline poly(L-lactic acid) (PLLA) vary in a wide range (82-203 J g-1). In most cases, such values were determined without taking into account the presence of α′- or α-crystal modifications, or the influence of D-lactic acid units in the analyzed poly(lactic acid). The bulk enthalpy of melting was determined for the stable orthorhombic α form in only few studies, and thermodynamic properties of the metastable α′-modification are not available yet. In the present work, the temperature dependence of Δhm° for both the α′- and α-crystal polymorphs of PLLA are determined, by combining differential scanning calorimetry and X-ray diffraction. It is proven that the enthalpies of melting of α′- and α-crystals of 100% crystalline PLLA are different. At the respective melting temperatures of 150 °C and 180 °C, the Δhm° values of the α′- and α-forms are 107 and 143 J g-1. At identical temperature, the enthalpy of melting of α′-crystals is approximately 25 J g-1 lower than that of the α-form. This observation is rationalized taking into account the presence of conformational defects in the disordered α′-modification.
No preview · Article · Jul 2015 · European Polymer Journal
[Show abstract][Hide abstract] ABSTRACT: Simultaneous SAXS-WAXD measurements are carried out to gain information about the microstructure and the molecular orientation developed by polymeric chains during the electrospinning process. Three semicrystalline polymers were studied, namely polyacrylonitrile, Nylon 6,6, and poly(ethylene oxide), as non-woven mats with either randomly arranged or aligned electrospun fibers. Mat thermal and morphological properties are investigated, together with their structural details in order to derive their hierarchical structure from the macro to the nano-scale. SAXS patterns have an elliptical shape with the main axis along the equator direction. No reflections are noticeable along the meridional direction, suggesting that the investigated electrospun fibers have a fibrillar structure with no trace of lamellar morphology. Combining the values of the unit cell and of the crystal size it can be concluded that in the fibers the ordered domains are organized into a bundle of fibrils due to the lateral aggregation of roughly 10 unit cells and the regular ordering of about either 50 (Nylon 6,6 and polyacrylonitrile) or 25 (poly(ethylene oxide)) cells in the chain direction.
[Show abstract][Hide abstract] ABSTRACT: We describe the production of graphene-based composites for energy storage, obtained by a combination of electrochemical and solution processing techniques. Electrochemically exfoliated graphene oxide sheets (EGO) are produced using an original setup that allows fast expansion of graphite flakes and efficient exfoliation of expanded graphite via an electrochemical route. The sheets are deposited on a sacrificial nickel foam together with an iron hydroxide colloidal precursor. Calcination treatment simultaneously renders the EGO foam conductive and transforms Fe(OH)3 into hematite (α-Fe2O3), yielding a nanoporous Fe2O3 layer on the surface of the mesoporous EGO foam, creating an ideal structure for lithium storage. The obtained graphene/metal oxide hybrid is a continuous, electrically conductive three-dimensional (3D) composite featuring a hierarchical meso-nano porous structure. A systematic study of these composites, varying the Fe2O3:EGO ratio, is then performed to maximize their performance as nanostructured electrodes in standard coin cell batteries.
[Show abstract][Hide abstract] ABSTRACT: By reacting 4,4′-bipyridine (bpy) with selected trinuclear triangular CuII complexes, [Cu3(μ3-OH)(μ-pz)3(RCOO)2(LL′)] [pz = pyrazolate anion; R = CH3, CH3CH2, CH2═CH, CH2═C(CH3); L, L′ = Hpz, H2O, MeOH] in MeOH, the substitution of monotopic ligands by ditopic bpy was observed. Depending on the stoichiometric reaction ratios, different compounds were isolated and structurally characterized. One- and two-dimensional coordination polymers (CPs), as well as two hexanuclear CuII clusters were identified. One of the hexanuclear clusters self-assembles into a supramolecular three-dimensional structure, and its crystal packing shows the presence of two intersecting channels, one of which is almost completely occupied by guest bpy, while in the second one guest water molecules are present. This compound also shows a reversible, thermally induced, single-crystal-to-single-crystal transition.
No preview · Article · Jan 2015 · Crystal Growth & Design
[Show abstract][Hide abstract] ABSTRACT: We report a successful chemical design strategy based on the even-odd alkyl end tailoring, which allows us to promote and control conformational polymorphism in single crystal and thin deposits of thienoimide-based molecular semiconductors (Cx-NT4N).
No preview · Article · Jan 2015 · Chemical Communications
[Show abstract][Hide abstract] ABSTRACT: 2,3-Thieno(bis)imide (N) ended oligomers are emerging as valuable molecular materials for application in organic electronics. Here, we report the synthesis and characterization of three new 2,3-thieno(bis)imide ended oligothiophenes (T) bearing unsaturated ethylene (E), azomethine (I) and ethinyl (A) inner bridges (NTE, NTI and NTA respectively). The effect of the unsaturated bridge on the π-conjugation extent, molecular conformation and overall aromaticity is related to the functional optoelectronic and morphology properties and compared to the properties of the linear analogue (NTT) with a bithiophene inner moiety. Optical spectroscopy and cyclovoltammetry analysis show a strong red shift of the absorption and a decreased energy band gap on going from NTI to NTE to NTA. The HOMO level decreases in the order NTE>NTI>NTA. Moreover, while the LUMO of NTE and NTA have almost the same energy, NTI has a LUMO energy about 0.1 eV lower, likely due to the electron withdrawing effect of the azomethine moiety. Morphologic investigation of solution cast thin deposits shows that the unsaturated bridges promote the formation of concomitant polymorphs with simultaneous presence of microcrystals with different morphology and fluorescence properties. Moreover, irreversible conversion of one polymorph to the other was achieved by thermal treatments for NTA and NTE and by exploiting this feature we realized a time temperature integrator (TTI) device based on NTE material. This device allowed to monitor temperature evolutions in the range between RT and 200°C by means of a red to yellow fluorescence switch that was detectable by optical microscopy.
[Show abstract][Hide abstract] ABSTRACT: In this contribution a new class of aliphatic poly(butylene succinate) (PBS)-based poly(ester urethane)s has been synthesized and characterized from the molecular, thermal and mechanical point of view. Hydrolytic degradation studies under physiological conditions have been conducted to assess their biodegradation rate. To obtain copolymers showing both thermoplastic and elastomeric properties, the chain-linking strategy has been considered. In particular, two hydroxyl-terminated oligomers have been synthesized by melt polycondensation: poly(butylene succinate) (PBS), as “hard segment”, and two poly(butylene adipate/diglycolate) (P(BAmBDGn) random copolymers as “soft segment”. The introduction of ether-linkages along the PBA chain permitted to depress its crystallinity degree and to enhance the wettability. Multiblock copolymers were finally obtained by chain extending with hexamethylene diisocyanate each P(BAmBDGn) copolymer with two different mass percentages of PBS: 30% and 50%. All copolymers maintained good thermal stability and were characterized by melting temperatures above 100°C. Elastic modulus (E) and stress at break (σb) varied with the chemical composition: the higher the PBS amount, the higher E and σb. No yield and very high elongations at break were observed. Hydrolytic degradation studies highlighted an increase of the degradation rate with the increase of the BDG content.
No preview · Article · Oct 2014 · Polymer Degradation and Stability
[Show abstract][Hide abstract] ABSTRACT: Herein is described a multidisciplinary approach to understand the performance limitations of small molecule organic light emitting transistors (OLETs) based on a layered architecture, an innovative architecture potentially competitive with the state of the art and more flexible for spectral emission control. The processes of charge injection and field-effect transport at metal/organic and organic/organic interfaces are analysed using microscopic and spectroscopic techniques in coordination. Atomic force microscopy and ultrasonic force microscopy are employed to characterize the interface morphology and the initial growth stages of organic films where charge transport actually occurs. X-ray diffraction and near edge X-ray dichroic absorption with linearly polarised light allow to determine the unit cell packing and the molecular orientation at the active organic interfaces, as well as the amount of non-ordered domains. Moreover, chemical reactivity at the interfaces are measured by X-ray photoelectron spectroscopy. It is found that a strong reaction occurs at the metal-organic interfaces, with molecular fragmentation. Additionally, the transport properties strongly depend on the nature of the materials forming the organic stack. Specifically, amorphous conjugated films as bottom layers can promote an increased molecular disorder in the upper active layer, with a concomitant deterioration of the conduction properties.
[Show abstract][Hide abstract] ABSTRACT: Polymorphic crystalline microfibers from an achiral octithiophene with one S-hexyl substituent per ring are separately and reproducibly grown with the same characteristics on various solid surfaces, including the interdigitated electrodes/SiO2 surface of a bottomcontact field-effect transistor. The arrangement of the same molecule in two diverse supramolecular structures leads to markedly different electronic, optical, and charge mobility properties. The microfibers—straight and yellow emitting or helical and red emitting—exhibit p-type charge transport characteristics, with the yellow ones showing a charge mobility and on/off current ratio of one and three orders of magnitude, respectively, greater than the red ones. Both forms show circular dichroism signals with significant differences from one form to the other. DFT calculations show that the octithiophene exists in two different quasi-equienergetic conformations aggregating with diverse orientations of the substituents. This result suggests that the observed polymorphism is conformational in nature. The self-assembly, driven by sulfur–sulfur non-bonding interactions, amplifies the small property differences between conformers, leading to quite different bulk properties.
Full-text · Article · Aug 2014 · Advanced Functional Materials
[Show abstract][Hide abstract] ABSTRACT: In this study, we propose a new class of multiblock copolyesters containing butylene 1,4-cyclohexanedicarboxylate (BCE) and diethylene glycol 1,4-cyclohexanedicarboxylate (DGCE) sequences. The two parent homopolymers were prepared by the usual two-stage melt polycondensation. On the other hand, the multiblock copolyesters, characterized by the same chemical composition but different block lengths, were synthesized by reactive blending. Physicochemical characterization (DSC, WAXS, tensile tests, WCA, hydrolysis experiments) demonstrated that the block length controls the polymer crystallinity, the thermal and mechanical properties, the wettability and the degradation rate. The copolymers displayed different stiffnesses, mainly depending on the crystallinity degree and macromolecular chain flexibility, a tunable range of degradation rates, and different surface hydrophilicity. Biocompatibility assays showed the absence of potentially cytotoxic products released into the culture medium by the investigated samples, and demonstrated that our substrates support a physical environment where cells can adhere and proliferate, confirming their potential for biomedical applications.
[Show abstract][Hide abstract] ABSTRACT: Poly(hexane dodecanoate) (PHD) based random copolyesters containing ether-linkages (P(HDxTEDy)) have been synthesized and characterized from the molecular and thermomechanical point of view. Gas permeability and biodegradability in compost have been also evaluated. The polymers showed good thermal stability and appeared as semicrystalline materials at room temperature. The main effect of copolymerization was a lowering in the crystallinity degree and a decrease of Tm with respect to homopolymers. Different surface hydrophilicity has been also displayed: water contact angle decreased with TED increasing mol %. Moreover, all the copolymers showed very high elongation at break, while the elastic modulus (E) and the stress at break (σb) were found strictly dependent on the composition: E and σb decreased with the increase of the TED content. Both permeability to CO2 and O2 and biodegradation rate evidenced a relationship with the chemical composition: the higher the TED mol %, the higher the permeability and the biodegradation extent.
No preview · Article · Jul 2014 · Industrial & Engineering Chemistry Research
[Show abstract][Hide abstract] ABSTRACT: A series of novel random copolymers of poly(butylene 1,4-cyclohexanedicarboxylate) (PBCE) containing triethylene glycol sub-unit (P(BCEmTECEn)) were synthesized and characterized in terms of molecular and solid-state properties, among these barrier properties to different gases (oxygen and carbon dioxide). In addition, biodegradability studies both in soil and in compost and ecotoxicological analysis, by means of the Lepidium sativum test, have been conducted.
The copolymers displayed a high and similar thermal stability with respect to PBCE. At room temperature, all the copolymers appeared as semicrystalline materials: the main effect of copolymerization was a lowering of crystallinity degree (χc) and a decrease of the melting temperature compared to the parent homopolymer. The Baur’s equation well described the Tm-composition data. Final properties and biodegradation rate of the materials under study were strictly dependent on copolymer composition and χc. As a matter of fact, hydrophilicity regularly increased with the increasing of TECE mol%, due to the PEG-like portion. The elastic modulus and the elongation to break decreased and increased, respectively, as TECE unit content was increased. As to the barrier properties, the selectivity ratios for the examined samples increased with the increasing of TECE mol%, confirming the correlation between the permeability and the chemical composition. The copolymers with lower TECE unit content (up to 30 mol%) showed improved barrier properties with respect to polylactide films tested under the same conditions.
Lastly, the biodegradation rate of P(BCEmTECEn) copolymers increased with the increasing of TECE mol%, while PBCE remained almost undegraded in the explored conditions.
[Show abstract][Hide abstract] ABSTRACT: The influence of the simultaneous presence of the two inhibitors of bone degradation, strontium and zoledronate, on the direct synthesis of hydroxyapatite was explored in the range of Sr concentration up to 50 atom% at two different bisphosphonate concentrations (ZOL7 and ZOL14). The results of structural analysis indicated that HA can be obtained as a single crystalline phase up to a Sr concentration in solution of 20 and 10 atom% within the ZOL7 and ZOL14 series respectively. Both Sr substitution and ZOL incorporation affect the length of the coherently scattering crystalline domains and the dimensions of HA nanocrystals. At greater Sr content, XRD full profile fitting data indicate that zoledronate provokes the segregation of Sr in two crystalline apatitic phases, at different strontium content. Co-cultures of osteoblast-like MG63 cells and human osteoclast show that ZOL displays a greater inhibitory influence than Sr on osteoclast proliferation and activity. On the other hand, the results obtained on osteoblast surnatant and on gene expression indicate that Sr exerts a greater promotion on osteoblast proliferation and differentiation. The co-presence of Sr and ZOL has a combined effect on the differentiation markers, so that HA containing about 4 wt% ZOL and 4 Sr atom%, and even more HA containing about 4 wt% ZOL and 8 Sr atom%, result the best compromise for osteoblast promotion and osteoclast inhibition.
[Show abstract][Hide abstract] ABSTRACT: The formation of gold nanoparticles (GNPs) within mesoporous silica matrices by means of irradiation
techniques is reported. The xerogels were impregnated with solutions of two different gold precursors:
(Ph3P)AuCl for Au(I) and [nBu4N]AuCl4 for Au(III). The irradiations were performed with two continuous
wave laser sources (266 and 532 nm), with a femtosecond pulsed laser (800 nm), and with a mercury
vapour lamp emitting in the UV region. It has been shown that no reducing agent was ever required to
obtain GNP formation. XRD data exhibited the typical patterns of fcc gold, except for two cases involving
the Au(I)-doped matrices, where a preferential crystallographic orientation was observed. Excluding the
case of the UV irradiations performed on Au(III)-doped samples, we always obtained the formation of
roughly spherical and well dispersed GNPs of relatively small size (6–60 nm). The gold-reduction
mechanisms proposed depend on the chosen irradiation technique. Moreover, when laser sources are
employed, GNP formation can be selectively limited to the irradiated areas, thus making it possible to
obtain reproducible patterns of GNPs.