Systematic Exploration of the Synthetic Parameters for the Production of Dynamic VO2(M1).

Thermochromic dynamic cool materials present a reversible change of their properties wherein by increasing the temperature, the reflectance, conductivity, and transmittance change due to a reversible crystalline phase transition. In particular, vanadium (IV) dioxide shows a reversible phase transition, accompanied by a change in optical properties, from monoclinic VO2(M1) to tetragonal VO2(R). In this paper, we report on a systematic exploration of the parameters for the synthesis of vanadium dioxide VO2(M1) via an easy, sustainable, reproducible, fast, scalable, and low-cost hydrothermal route without hazardous chemicals, followed by an annealing treatment. The metastable phase VO2(B), obtained via a hydrothermal route, was converted into the stable VO2(M1), which shows a metal-insulator transition (MIT) at 68 °C that is useful for different applications, from energy-efficient smart windows to dynamic concrete. Within this scenario, a further functionalization of the oxide nanostructures with tetraethyl orthosilicate (TEOS), characterized by an extreme alkaline environment, was carried out to ensure compatibility with the concrete matrix. Structural properties of the synthesized vanadium dioxides were investigated using temperature-dependent X-ray Diffraction analysis (XRD), while compositional and morphological properties were assessed using Scanning Electron Microscopy, Energy Dispersive X-ray Analysis (SEM-EDX), and Transmission Electron Microscopy (TEM). Differential Scanning Calorimetry (DSC) analysis was used to investigate the thermal behavior.

Influence of the ion size on the stability of the smectic phase of ionic liquid crystals.

The thermotropic phase behavior of ionic liquids and ionic liquid crystals based on novel N-alkyl-3-methylpyridinium halides, trihalides and dichloroiodates was experimentally studied by polarized optical spectroscopy (POM) and differential scanning calorimetry (DSC) as well as by molecular dynamics (MD) simulation. In the experiments, the existence and thermal range of stability of the smectic phase of these ionic liquid crystals are found to strongly depend on the volume ratio between the cation and anion, that is their relative size. Only compounds with a relatively large volume ratio of the cation to anion, i.e., those with longer cationic alkyl chains and monoatomic halide anions, have a stable smectic A phase. Both melting points and clearing points increase with such a ratio. The MD simulation results qualitatively agree very well with the experimental data and provide molecular details which can explain the experimentally observed phenomena: the stronger van der Waals interactions from the longer alkyl chains and the stronger electrostatic interactions from the smaller anions with a higher charge density increase the stability of both the crystal phase and the smectic phase; this also prevents the ionic layers from easily mixing with the hydrophobic regions, a mechanism that ultimately leads to a nanosegregated isotropic liquid phase.

Composition-Thermometric Properties Correlations in Homodinuclear Eu3+ Luminescent Complexes.

A family of homodinuclear Ln3+ (Ln3+ = Gd3+, Eu3+) luminescent complexes with the general formula [Ln2(ß-diketonato)6(N-oxide)y] has been developed to study the effect of the ß-diketonato and N-oxide ligands on their thermometric properties. The investigated complexes are [Ln2(tta)6(pyrzMO)2] (Ln = Eu (1·C7H8), Gd (5)), [Ln2(dbm)6(pyrzMO)2] (Ln = Eu (2), Gd (6)), [Ln2(bta)6(pyrzMO)2] (Ln = Eu (3), Gd (7)), [Ln2(hfac)6(pyrzMO)3] (Ln = Eu (4), Gd (8)) (pyrzMO = pyrazine N-oxide, Htta = thenoyltrifluoroacetone, Hdbm = dibenzoylmethane, Hbta = benzoyltrifluoroacetone, Hhfac = hexafluoroacetylacetone, C7H8 = toluene), and their 4,4'-bipyridine N-oxide (bipyMO) analogues. Europium complexes emit a bright red light under UV radiation at room temperature, whose intensity displays a strong temperature (T) dependence between 223 and 373 K. This remarkable variation is exploited to develop a series of luminescent thermometers by using the integrated intensity of the 5D0 → 7F2 europium transition as the thermometric parameter (Δ). The effect of different ß-diketonato and N-oxide ligands is investigated with particular regard to the shape of thermometer calibration (Δ vs T) and relative thermal sensitivity curves: i.e.. the change in Δ per degree of temperature variation usually indicated as Sr (% K-1). The thermometric properties are determined by the presence of two nonradiative deactivation channels, back energy transfer (BEnT) from Eu3+ to the ligand triplet levels and ligand to metal charge transfer (LMCT). In the complexes bearing tta and dbm ligands, whose triplet energy is ca. 20000 cm-1, both deactivation channels are active in the same temperature range, and both contribute to determine the thermometric properties. Conversely, with bta and hfac ligands the response of the europium luminescence to temperature variation is ruled by LMCT channels since the high triplet energy (>21400 cm-1) makes BEnT ineffective in the investigated temperature range.

Robust and Biocompatible Functionalization of ZnS Nanoparticles by Catechol-Bearing Poly(2-methyl-2-oxazoline)s.

Zinc sulfide (ZnS) nanoparticles (NPs) are particularly interesting materials for their electronic and luminescent properties. Unfortunately, their robust and stable functionalization and stabilization, especially in aqueous media, has represented a challenging and not yet completely accomplished task. In this work, we report the synthesis of colloidally stable, photoluminescent and biocompatible core-polymer shell ZnS and ZnS:Tb NPs by employing a water-in-oil miniemulsion (ME) process combined with surface functionalization via catechol-bearing poly-2-methyl-2-oxazoline (PMOXA) of various molar masses. The strong binding of catechol anchors to the metal cations of the ZnS surface, coupled with the high stability of PMOXA against chemical degradation, enable the formation of suspensions presenting excellent colloidal stability. This feature, combined with the assessed photoluminescence and biocompatibility, make these hybrid NPs suitable for optical bioimaging.

Next-Generation Polymer Shells for Inorganic Nanoparticles are Highly Compact, Ultra-Dense, and Long-Lasting Cyclic Brushes.

Cyclic poly-2-ethyl-2-oxazoline (PEOXA) ligands for superparamagnetic Fe3 O4 nanoparticles (NPs) generate ultra-dense and highly compact shells, providing enhanced colloidal stability and bio-inertness in physiological media. When linear brush shells fail in providing colloidal stabilization to NPs, the cyclic ones assure long lasting dispersions. While the thermally induced dehydration of linear PEOXA shells cause irreversible aggregation of the NPs, the collapse and subsequent rehydration of similarly grafted cyclic brushes allow the full recovery of individually dispersed NPs. Although linear ligands are densely grafted onto Fe3 O4 cores, a small plasma protein such as bovine serum albumin (BSA) still physisorbs within their shells. In contrast, the impenetrable entropic shield provided by cyclic brushes efficiently prevents nonspecific interaction with proteins.

Viologen-based ionic liquid crystals: induction of a smectic A phase by dimerisation.

The stability of thermotropic ionic liquid crystals is essentially due to micro-phase segregation between the ionic heads and the long alkyl chains. Here we show, using newly synthesized viologen dimers, that the structure of the central core is another key parameter to play with in order to tune the mesomorphic behaviour.

Thermal behaviour and electrochemical properties of bis(trifluoromethanesulfonyl)amide and dodecatungstosilicate viologen dimers.

We report the synthesis and characterization of dimeric viologen salts (1',1''-(alkane-1,n-diyl)bis(1-ethyl-4,4'-bipyridinium) with n = 4-10) with bis(trifluoromethanesulfonyl)amide (bistriflimide, Tf(2)N(-)) as a counteranion. For n = 4, 5 and 6, and for the nonylviologen cation (1,1'-dinonyl-4,4'-bipyridinium) we also prepared salts with the totally inorganic dodecatungstosilicate anion, SiW(12)O(40)(4-), featuring a poly-charged surface and nanosized dimensions. The materials have been characterized by means of calorimetric techniques, X-ray diffraction and solid state NMR and a comparison is made with analogous monomeric viologen salts exhibiting smectic mesophases. A strong odd-even effect is observed in the melting points and in the thermal behaviour of the bistriflimide dimeric systems, similar to what was reported for dipolar calamitic liquid crystal dimers, although the studied viologen dimers are not mesomorphic. By increasing the size of the counteranion we have observed a destabilization of the crystal phases and of the mesophases in favour of a glassy amorphous state. Implications on the design of novel ionic liquid crystals are discussed. The electrochemical behaviour in solution has been investigated by cyclic voltammetry measurements: interestingly, the odd-even effect is clearly visible also in the redox potentials. The spin-pairing of the viologen radical cations formed at each end of the dimer is responsible for the observed redox trend. Insights on the structure of the spin-paired dimer have been obtained by DFT calculations.

Structure-property relationships in heterophasic thermoplastic elastomers filled with montmorillonite.

Polypropylene (PP)/ethylene-propylene rubber (EPR)/Montmorillonite ternary nanocomposites with a phase separated morphology were studied in this work. Wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to investigate the samples. One of the aim of this work was to separate the effects of rubber and clay content on the structure, morphology and mechanical properties of the samples. The presence of clay favored the formation of gamma phase and disrupted the lamellar framework. Clay had moreover a major role in shaping the phase separated morphology of the samples. Atomic Force Microscopy showed that the shear exerted by the clay layers was key for inducing a shish kebab morphology in the polymer matrix. Rubber content decreased the degree of crystallinity at a crystalline cell level and induced the formation of a double population of lamellar stacks. The mechanical properties of the samples primarily depended on rubber content, and they were secondarily tuned by the effect of clay. This synergistic effect allowed to obtain composites with increased stiffness, ductility and toughness, oppositely to what is frequently found.

New Directions in Aesthetic Medicine: A Novel and Hybrid Filler Based on Hyaluronic Acid and Lactose Modified Chitosan.

Fillers based on crosslinked hyaluronic acid (HA) are becoming increasingly important in the field of aesthetic medicine, for example for treating wrinkles or for volumizing purposes. However, crosslinking agents are usually associated with toxicity and adverse reactions. The aim of this study is the development of an innovative technology to manufacture high performance HA-based fillers using minimal amounts of crosslinking agent. In this work, new fillers based on HA, functionalized with different amounts of 1,4-butanediol diglycidyl ether (BDDE) (degree of modification ranging between 3.5% and 8.8%) and formulated with a lactose modified chitosan (CTL), were investigated. The relative quantities of these polymeric building blocks in the formulations were 20-25 and 5 mg/mL for HA and CTL, respectively. Due to its cationic nature, CTL could interact with the anionic HA and enhance the elastic properties of the filler. Fillers manufactured with this novel technology (HACL-CTL) were characterized and compared with several fillers available in the market. In particular, resistance against hyaluronidase, swelling, cohesivity and rheological properties were investigated. Cohesivity, resistance to hydrolysis and swelling of HACL-CTL were comparable to commercial products. However, HACL-CTL fillers showed excellent elastic performance that reached 94% of elasticity in response to shear stresses. Surprisingly, these fillers also showed a resistance to compression higher than that of currently marketed products, making them very promising for their lifting effect.

Fish-Waste-Derived Gelatin and Carbon Dots for Biobased UV-Blocking Films.

The fish industry produces every year huge amounts of waste that represent an underutilized source of chemical richness. In this contribution, type I collagen was extracted from the scales of Mugil cephalus and carbon dots (CDs) were synthesized from the scales of Dicentrarchus labrax. These materials were combined to make hybrid films with UV-blocking ability, by casting a mixture of gelatin, glycerol (15%), and CDs (0, 1, 3, and 5%). The films were fully characterized from the mechanical, morphological, and optical point of view. Here, 40 µm thick films were obtained, characterized by a high water solubility (70%); moreover, the presence of CDs improved the film mechanical properties, in particular increasing the tensile strength (TS) up to 17 MPa and elongation at break (EAB) up to 40%. The CDs also modulated water vapor permeability and the thermal stability of the films. From the optical point of view, with just 5% loading of CDs the films blocked almost 70% of the UV radiation with negligible change in transparency (88.6% for the nonloaded vs 84.4% for 5% CDs) and opacity (1.32 for nonloaded vs 1.61 for 5% CDs). These types of hybrid biobased films hold promise for the production of sustainable UV-shields both for human health and for prolonging the shelf life of food.

Characterisation of plastic wads: A useful approach for elucidating shooting accidents and homicides involving shotguns.

Wads are components of shotgun cartridges used for transferring to pellets or slugs the kinetic energy produced during the combustion chain which takes place as the trigger is pulled by the shooter. The hull of the cartridge falls in the vicinities of the gun, so it is easy for a malicious shooter to cancel this particular trace from a crime scene. However, the wad is projected to an intermediate point between the shooter and the victim, it is easily lost, and so it can be useful as a trace containing information on the type of ammunition used by a shooter and possibly a convenient item for comparison with analogous objects found in the premises of a suspect. In this paper, various analytical approaches, such as thermal analysis, infrared spectroscopy and X-ray diffraction were employed in order to discriminate apparently similar commercial wads. Samples that had previously been fired and pristine samples were examined, verifying that the energy, temperature and pressure associated to the combustion of the powder in the bore does not bring about appreciable changes in the polymer structure, thus allowing to use this approach in casework.

Water-soluble peptide-coated nanoparticles: control of the helix structure and enhanced differential binding to immune cells.

The stabilizing action of C(α)-tetrasubstituted α-amino acids inserted into a sequence of short peptides allowed for the first time the preparation of water-soluble nanoparticles of different materials coated with a helix-structured undecapeptide. This peptide coating strongly favors nanoparticle uptake by human immune system cells.

Development of Quebracho (Schinopsis balansae) Tannin-Based Thermoset Resins.

One of the major challenges currently in the field of material science is finding natural alternatives to the high-performing plastics developed in the last century. Consumers trust synthetic products for their excellent properties, but they are becoming aware of their impact on the planet. One of the most attractive precursors for natural polymers is tannin extracts and in particular condensed tannins. Quebracho (Schinopsis balansae) extract is one of the few industrially available flavonoids and can be exploited as a building block for thermoset resins due to its phenol-like reactivity. The aim of this study was to systematically investigate different hardeners and evaluate the water resistance, thermal behavior, and chemical structure of the quebracho tannin-based polymers in order to understand their suitability as adhesives. It was observed that around 80% of the extract is resistant to leaching when 5% of formaldehyde or hexamine or 10% of glyoxal or furfural are added. Additionally, furfuryl alcohol guarantees high leaching resistance, but only at higher proportions (20%). The quebracho-based formulations showed specific thermal behavior during hardening and higher degradation resistance than the extract. Finally, these polymers undergo similar chemistry to those of mimosa, with exclusive reactivity of the A-ring of the flavonoid.

Does Eumelanin Oxidation Play a Role on the Photostability of Ethyl Glucuronide in Hair Exposed to Simulated Solar Radiation?

The action of solar radiation on the concentration of the ethanol metabolite ethyl glucuronide (EtG) in 40 hair samples of nonabstinent subjects was investigated. Hair samples of different colors were analyzed before and after irradiation with artificial sunlight under a light dose corresponding to 3 months of sun exposure. After irradiation, an increase of EtG concentration was detected in 55% of the samples ranging from 5% to 141%. In 16 cases, a concentration reduction ranging from -2% to -74% was observed. The measure of the level of pyrrole-2,3,5-tricarboxylic acid (PTCA), a marker of eumelanin oxidation, demonstrated the largest increase in oxidation in light brown hair where the greatest degradation of EtG was observed after irradiation. However, the rise of PTCA in all hair tested was accompanied by increase in EtG concentration in 8/10 samples and by decrease in 2/10, suggesting no correlation between the two markers. To verify if hair structure was modified by light, scanning electron microscopy (SEM) analysis was performed on irradiated hair of different colors and compared with the dark samples. SEM revealed modification of hair structure in all samples showing partial shaft exfoliation and reduction of hair thickness under the treatment with solar radiation.

Crystallization of a (1-butene)-ethylene copolymer in phase I directly from the melt in nanocomposites with montmorillonite.

Nanocomposites based on a copolymer of 1-butene and ethylene filled with montmorillonite (Cloisite 15A) were studied, obtaining for the first time crystallization from the melt directly into phase I. The polymorphism of the polymer and the dispersion of the filler in the matrix were investigated. The effect of the compatibilizer (PB-g-MA) on these properties was also singled out. The dramatic increase in the rate of the II --> I phase transition due to montmorillonite was attributed to the alteration in the phase stability diagram of the matrix, due to the introduction of defects and to induction of local pressure on the crystalline domains.

Firing pin impressions: a valuable feature for determining the orientation of the weapon at the time of shooting.

Sometimes the firearm forensic examiner is required to provide information useful to discriminate between suicide, homicide or accident, or between contradictory reconstructions of the events (like attempted murder versus accidental discharge). In such situations, knowledge of the position and orientation of the firearm at the time of firing can be of fundamental help for the reconstruction of events. To achieve these goals, the analysis of the firing impressions is very important. In this study, the cartridge cases shot with three different revolvers aiming at three different spatial orientations (vertical upwards, horizontal or vertical downwards) were studied. The depth and morphology of the firing pin impression was characterised by optical microscopy and quantified by a surface topography analysis. The orientation of the firearm significantly modified the morphology and depth of the firing pin impression: ammunition fired upwards had the deepest firing pin impression, those fired downwards had the shallowest. Such behaviour was attributed to the different geometry of the firing pin-primer cup interaction and to the different pressure exerted by the primer as the orientation of the weapon changes. Therefore, this work has shown that a suitable protocol of morphological and topographical analysis can be set up to understand if a shot by a revolver was fired holding the weapon upwards, downwards or horizontally.

Combined Statistical Analyses of Forensic Evidence in Sexual Assault: A Case Report and Brief Review of the Literature.

DNA analysis has been widely used in the forensic field in order to contribute to identifying the perpetrator of a crime. Forensic investigation in sexual assaults usually focuses on locating and identifying biological fluids, followed by DNA analysis. The identification of certain compounds present in condoms can be useful to reconstruct the occurred event, especially in cases of sexual assaults where the DNA analysis did not show the presence of a male profile and where RNA analysis did not show the presence of sperm markers. Herein we describe the case of a woman reporting to be victim of sexual assault, who was not able to provide accurate information concerning the dynamics of the event; she remembered only forced penile-vaginal penetration by a single perpetrator. We performed short tandem repeat (STR) analyses and mRNA typing for forensic genetics testing on vaginal and rectal swabs collected on the victim, and Fourier-transform infrared spectroscopy (FTIR) followed by chromatographic analyses for the detection of condom compounds on the same swabs. The STR analysis showed only the victim's genetic profile, and RNA analysis showed only the presence of vaginal and skin markers. In this situation, the identification of condom compounds residues on vaginal swabs became important as it complemented other collected evidences allowing the Court to reconstruct the events. A proposal of likelihood ratio (LR) calculation for the assessment of the weight of evidence in this case is described.

Perkalite as an innovative filler for isotactic polypropylene-based nanocomposites.

Perkalite, an organically modified synthetic layered double hydroxide, was used as a filler in the preparation of nanocomposites based on isotactic polypropylene. The polymorphism of the polymer matrix was investigated, finding that Perkalite favors beta phase in certain conditions and is not a nucleant for the gamma polymorph. Perkalite promoted the formation of a dual population of lamellae, as evidenced by SAXS data. The dispersion of the filler was studied by WAXD, SAXS, and TEM. Perkalite was intercalated by the polymer and formed small, rather disordered tactoids, that determined an increase in physical mechanical properties, such as modulus, impact strength, thermal stability and heat deflection temperature. The Tm(0) of the materials was calculated by the method proposed by Marand, the kinetics of crystallization was evaluated by the Avrami analysis and also the Hoffman-Lauritzen theory of crystallization regimes was applied. Perkalite was found to depress Tm(0), to greatly enhance the rate of crystallization and to ease the chain folding of macromolecules.

The effect of composition and morphological features on the striation of .22LR ammunition.

In this paper, the effect of the chemical composition of .22LR bullets was studied and correlated to the extent and quality of the markings left after shooting them with the same gun. Scanning electron microscopy and optical comparator microscopy equipped with 3D and profilometry modules were used as non destructive techniques with two main purposes. The first is to assist the firearm examiner in the choice of the ammunition most suitable for preparing the test bullets. The second is to propose an approach, crossing data from optical microscopy, profilometry and space-resolved chemical analysis, for explaining the morphology of striae, whether continuous or interrupted. Among the most notable results is the finding that commercial .22LR ammunition show very wide interbrand, interlot and intralot variability. A selection of test ammunition solely based on the same brand and model used on the crime scene is therefore not suitable, urging the need for a more accurate choice, based on a preliminary chemical analysis.

Structure-property relationship in polyethylene reinforced by polyethylene-grafted multi-walled carbon nanotubes.

Polyethylene-grafted multiwalled carbon nanotubes (PE-g-MWNT) were used to reinforce polyethylene (PE). The nanocomposites possessed not only improved stiffness and strength, but also increased ductility and toughness. The effects on the structure and morphology of composites due to pristine multiwalled carbon nanotubes (MWNT) and PE-g-MWNT were studied and compared using small angle X-ray scattering (SAXS), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The SAXS long period, crystalline layer thickness and crystallinity of polymer lamellar stacks were found to decrease significantly in MWNT composites, while the decreases were much smaller in PE-g-MWNT composites. PE-g-MWNT allowed a more efficient and unhindered crystallization at a lamellar level, while MWNT disrupted the order of lamellar stacks, probably because of their tendency to aggregate. The SAXS crystallinity and the mechanical properties of the composites showed similar trends as a function of MWNT content. This suggested that the improvement of the interfacial strength between polymer and carbon nanotubes was a result of synergistic effects of better dispersion of the filler, better stress transfer, due to the grafting of polymer and MWNT, and the nucleation of a crystalline phase around MWNT. The latter effect was confirmed by measurements of kinetics of non-isothermal crystallization.