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Bent-core liquid crystals, a class of mesogenic compounds with non-linear molecular structures, are well known for their unconventional mesophases, characterized by complex molecular (and supramolecular) ordering and often featuring biaxial and polar properties. In the nematic phase, their unique behavior is manifested in the formation of nano-sized biaxial clusters of layered molecules (cybotactic groups). While this prompted their consideration in the quest for nematic biaxiality, experimental evidence indicates that the cybotactic order is only short-ranged and that the nematic phase is macroscopically uniaxial. By combining atomic force microscopy, neutron reflectivity and wide-angle grazing-incidence X-ray scattering, here, we demonstrate that multilayer films of a bent-core nematic, deposited on silicon by a combined Langmuir–Blodgett and Langmuir–Schaefer approach, exhibit macroscopic in-plane ordering, with the long molecular axis tilted with respect to the sample surface and the short molecular axis (i.e., the apex bisector) aligned along the film compression direction. We thus propose the use of Langmuir films as an effective way to study and control the complex anchoring properties of bent-core liquid crystals. [ABSTRACT FROM AUTHOR]

Bio‐inspired and biodegradable quantum optics scenarios constitute a pathway toward environmentally friendly front‐end technologies. Such an inspiring perspective necessitates the replacement of classic gain materials with a biological counterpart like photoluminescent bacteria. It is easy to imagine that, in this case, a planar and cell‐viable substitute of classic bulk solid‐states resonators can be highly beneficial. In this paper a micro‐ and nano‐photonic structuration of both a standard and a functionalized version of a typical bacterial growth medium (Luria‐Bertani Agar – LBA) is successfully realized. Three structures belonging to the categories of photonic crystals are replicated, such as quasi‐crystals and meta‐surfaces, demonstrating how the proposed media can be used as templates for high‐end photonic applications. The optical quality of the replicated structures is confirmed by far‐field diffraction measurements. The structured growth media allow for a broad control of the surface wettability by accessing a so‐called Wenzel state, in which the original hydrophilicity of a material is increased due to the photonic structuration. Finally, the suitability of the nano‐structured LBA as a plasmonic platform is evidenced. The proposed micro‐and nano‐structured photonic growth media constitute the first, fundamental step toward quantum optical frameworks from biological media. [ABSTRACT FROM AUTHOR]

Keratin proteins extracted from wool fibers by sulfitolysis were electrospun for the production of active nanofiber membranes (NFMs). The keratin NFMs were composited with nylon woven fabric for improving their mechanical properties as a filtration material. The prepared membranes were characterized in terms of morphology, pore size, contact angle, and performance of water and air permeability. Experimental data showed that most of investigated parameters were affected by the electrospinning time: that is, roughness rose by increasing the electrospinning time, while the narrowest pore size distribution was obtained at the longest electrospinning time (2 h). The pure water permeability (PWP) was greater for the produced NFMs than for the commercial microfiltration membranes and decreased by increasing the electrospinning time. At the longest electrospinning time, the produced NFMs showed a PWP of about 45.7 [m.sup.3]/[m.sup.2] h bar, which is a value greater than those obtained by conventional materials used in water filtration, including microfiltration membranes. According to the data of contact angle measurements, the high hydrophobicity of NFMs membranes could reinforce their stability in water. Other potential applications could be venting, adsorption of VOCs, and separation of oils from oil/water emulsions., INTRODUCTION Keratins are naturally fibrous proteins found in animal tissues, including hair, wool, and horns, characterized by high chemical stability due to the presence of many cysteine residues (7-20%) forming [...]

In this study, a method is presented to fabricate optical fingerprint‐like patterns. The method relies on the use of commercially available chiral nematic liquid crystals (CNLCs) confined in microspheres. The peculiar optical texture is obtained by applying a high‐frequency voltage to the micrometric objects able to distort the molecular director orientation. The texture can be stabilized by doping the CNLC with photosensitive materials. Each microsphere shows a different fingerprint‐like pattern that is generated in a completely random manner making this procedure suitable to create physical unclonable functions (PUFs) keys. The optical patterns can be stored to create an artificial fingerprints database or they can be used to fabricate electroluminescent labels to be exploited as complex anti‐counterfeiting devices. An authentication software is developed and used to test the robustness of the proposed anti‐counterfeiting system. [ABSTRACT FROM AUTHOR]

Chromonic liquid crystals have recently received a lot of attention due to their spontaneous self-assembly in supramolecular columnar structures that, depending on their concentration in water, align to form a nematic liquid crystalline phase. The chirality may be induced in chromonics by adding chiral moieties to the nematic phase or enhanced by confining them in curved geometrical constraints. This review summarizes the recent research developments on chiral chromonic liquid crystals confined in spherical geometry, relating the results to what was observed for thermotropic liquid crystals in the same conditions. The review focuses on the studies carried out on commercially available nematic chromonics, investigating the effects on their topologies in different anchoring conditions and different chiral dopants and suggesting an application in the sensor field. [ABSTRACT FROM AUTHOR]

Anticounterfeiting of goods is an urgent need both for luxury and cheap everyday life products. Their identification is usually based on overt technologies as printed codes, easy to produce but to be cloned as well. In this work, a standard QR‐code printed on office paper but hidden by a plasmonic multilayer system is exploited. The covert label is then protected by a peculiar reading mechanism, which is only possible in specific illumination conditions. The overall photonic structure consisting of the metal –insulator –metal –insulator, the printed random QR code and the paper substrate results in a strong physical unclonable function (PUF) that provides a multi‐level identification and authentication of goods ensuring uniqueness of nominally quasi‐identical tags and resistance to tampering/cloning attacks. The proposed paper‐based camouflage physical unclonable function (PC‐PUF) can be easily fabricated by low cost and large area techniques paving the way for an easy integration in an industrial supply‐chain as tags devoted to protect consumer merchandises. [ABSTRACT FROM AUTHOR]

Bent-core mesogens (BCMs) are a class of thermotropic liquid crystals featuring several unconventional properties. However, the interpretation and technological exploitation of their unique behavior have been hampered by the difficulty of controlling their anchoring at surfaces. To tackle this issue, we report the nanoscale structural characterization of BCM films prepared using the Langmuir–Blodgett technique. Even though BCMs are quite different from typical amphiphilic molecules, we demonstrate that stable molecular films form over water, which can then be transferred onto silicon substrates. The combination of Brewster angle microscopy, atomic force microscopy, and X-ray reflectivity measurements shows that the molecules, once transferred onto a solid substrate, form a bilayer structure with a bottom layer of flat molecules and an upper layer of upright molecules. These results suggest that Langmuir–Blodgett films of BCMs can provide a useful means to control the alignment of this class of liquid crystals. [ABSTRACT FROM AUTHOR]

Multilevel anticounterfeiting Physical Unclonable Function (PUF) tags based on thin film of silver (Ag), Zinc Oxide (ZnO) and PolyVinylPyrrolidone (PVP), are experimentally demonstrated and validated. We exploit the low adhesion of silver to glass and consequent degradation during ZnO deposition to induce morphological randomness. Several photographs of the tag surfaces have been collected with different illumination conditions and using two smartphones of diverse brand. The photos were analyzed using an image recognition algorithm revealing low common minutiae for different tags. Moreover, the optical response reveals peculiar spectra due to labels of plasmonic nature. The proposed systems can be easily fabricated on large areas and represent a cost-effective solution for practical protection of objects. [ABSTRACT FROM AUTHOR]

Induced or spontaneous chirality in natural systems is an intriguing issue. In recent years, a lot of attention has been focused on chirality of chromonic liquid crystals, a class of materials that is able to self-assemble in columnar structures. However, the mechanism involved in the arising of chirality in these materials, that starts at the molecular level and controls the supramolecular structure, is poorly understood; however, it is certainly affected by ionic strength. In this work we present the results obtained doping Cromolyn, a chromonic material, with a strong helical-twisting-power peptide, and confining it in a spherical geometry. We demonstrate, by means of optical polarized microscopy and structural analysis, that both the geometrical constraint and the presence of the chiral dopant enhance the chiral effect; we also demonstrate that they favor the rise of a highly ordered helical superstructure, that may be optimized upon adding an ionic dye to the system. Finally, we report a procedure for the preparation of free-standing polymeric films, embedding and preserving the microspheres, and paving the way for the creation of biocompatible and eco-friendly optical devices to be used in the sensor and anticounterfeiting fields. [ABSTRACT FROM AUTHOR]

Chirality emergence in biological systems is common but the chiral expression from the molecular to macroscopic level in water‐based systems is poorly understood. Among water‐based systems, chromonic liquid crystals have recently received a lot of attention due to the spontaneous chirality they show when confined in curved geometries. Confinement of chiral‐induced chromonics is not trivial since they are three component systems whose time stability is a delicate thermodynamic balance. In this work, a well‐defined periodic Frank–Pryce texture, typical of chiral thermotropic liquid crystals, is observed in microspheres of a chiral induced chromonic embedded in a poly(dimethylsiloxane) matrix. This texture slowly degrades in time and a possible mechanism behind the degradation process is suggested via X‐ray diffraction and atomic force microscopy measurements on thin chromonic films. To stabilize this texture and to control the structure periodicity, cations are added to the three components system in an attempt to tune the non‐covalent interactions between molecules and supramolecular stacks. The study of the effects of this addition allows for better insight into the molecular interactions that occur in the chiral induced mesophase. This is a crucial point in view of possible biocompatible technological applications. [ABSTRACT FROM AUTHOR]

Objective: To investigate if epigenome of sperm cells could be dynamically affected by nutrition. Design and Methods: We assessed 40 healthy volunteers with different dietary habits and collected their demographic characteristics, as well as clinical and anthropometric parameters. We compared methylation profiles in sperm quantified by bisulfite pyrosequencing, at promoter-associated CpG sites of genes involved in metabolism including fat mass and obesity-associated (FTO) and melanocortin-4 receptor (MC4R) from six vegans and 34 omnivores. In addition, the FTO rs9939609 (T>A) was genotyped. Results: Higher DNA methylation levels were detected in the sperm of vegan at FTO gene CpG1 (p=0.02), CpG2 (p=0.001), CpG3 (p=0.004), and CpG4 (p=0.003) sites and at MC4R -CpG2 site [p=0.016] as compared to sperm of omnivores. This association was not related to FTO genotype. Conclusions: Although limited by the small number of investigated cases, our data provide insight into the role of diet on sperm DNA methylation in genes involved in metabolism. [ABSTRACT FROM AUTHOR]

In the past three decades, several conventional methods have been employed for characterizing the bitumen ageing phenomenon, such as rheological testing, ultraviolet testing, gel permeation chromatography (GPC), gas chromatography (GC), atomic force microscopy (AFM), X-ray scattering, and Fourier transform infrared spectroscopy (FTIR). Nevertheless, these techniques can provide only limited observations of the structural micro-modifications occurring during bitumen ageing. In this study, Fourier transform nuclear magnetic resonance self-diffusion coefficient (FT-NMR-SDC) spectroscopy, as a novel method, was employed to investigate and compare the microstructural changes between virgin bitumen (pristine bitumen) and aged bitumen. The virgin bitumen was aged artificially using two standard ageing tests: Rolling Thin-Film Oven Test (RTFOT) and Pressure Ageing Vessel (PAV). For a comprehensive comparison and an assessment of the validity of this method, the generated samples were studied using various methods: rheological test, atomic force microscopy, and optical microscopy. Significant differences were obtained between the structure and ageing patterns of virgin and aged bitumen. The results indicate that the modification of maltenes to asphaltenes is responsible for the ageing character. When compared with the other methods' findings, FT-NMR-SDC observations confirm that the asphaltene content increases during ageing processes. [ABSTRACT FROM AUTHOR]

Nature has evolved several molecular strategies to ensure adhesion in aqueous environments, where artificial adhesives typically fail. One recently‐unveiled molecular design for wet‐resistant adhesion is the cohesive cross‐β structure characteristic of amyloids, complementing the well‐established surface‐binding strategy of mussel adhesive proteins based on 3,4‐l‐dihydroxyphenylalanine (Dopa). Structural proteins that self‐assemble into cross β‐sheet networks are the suckerins discovered in the sucker ring teeth of squids. Here, light is shed on the wet adhesion of cross‐β motifs by producing recombinant suckerin‐12, naturally lacking Dopa, and investigating its wet adhesion properties. Surprisingly, the adhesion forces measured on mica reach 70 mN m−1, exceeding those measured for all mussel adhesive proteins to date. The pressure‐sensitive adhesion of artificial suckerins is largely governed by their cross‐β motif, as evidenced using control experiments with disrupted cross‐β domains that result in complete loss of adhesion. Dopa is also incorporated in suckerin‐12 using a residue‐specific incorporation strategy that replaces tyrosine with Dopa during expression in Escherichia coli. Although the replacement does not increase the long‐term adhesion, it contributes to the initial rapid contact and enhances the adsorption onto model oxide substrates. The findings suggest that suckerins with supramolecular cross‐β motifs are promising biopolymers for wet‐resistant adhesion. [ABSTRACT FROM AUTHOR]

Ag(I)‐containing ethylcellulose (EC) films suitable as antbacterial packaging materials have been prepared and fully characterized. Different preparation methods, including the use of green casting solvents, are proposed. The Ag(I) acylpyrazolonato complexes, [Ag(Qpy,CF3)(L)], L=benzylimidazole (Bzim) and L=ethylimidazole (EtimH), used as active additives, display different modes of interactions with EC, depending on their structural features. A thorough investigation of the EC liquid‐crystalline lyotropic phase and its changes with the introduction of silver additives, has been conducted, revealing either the inclusion of complex molecules into the inner structure of the EC matrix or their dispersion on its surface. Moreover, the bactericidal activity of the prepared Ag(I) films seems to be related to the interaction between silver additives and the polymeric EC matrix. Indeed, the EC‐2b films show a particularly good performance even with a low silver content, with a relative bacterial killing of about 100 %. Tests for Ag(I) migration have been performed by using three food stimulants under two assay conditions. Low values of silver release are recorded, particularly at low concentration of silver content, in the case of all new prepared Ag(I) films. [ABSTRACT FROM AUTHOR]

In the last decade, the possibility to use liquid crystal droplets as optical micro-cavities and lasers has attracted much attention since it paves the way for many applications in the field of sensors or tunable photonics. Several techniques can be used to obtain small micro-resonators as, for example, dispersing a cholesteric liquid crystal inside an immiscible isotropic fluid to create an emulsion. Since liquid crystals are extremely sensitive to external factors as temperature or external fields, laser tuning can be easily achieved. Here, we report on the possibility to tune the laser emission from dye doped cholesteric liquid crystals microdroplets dispersed in a glycerol matrix in presence of nitric acid molecules in the emulsion. Using a fluorescent dye with pH dependent optical properties, the emitted laser wavelength can be tuned in a range of 60 nm. This effect could find applications for the development of spectroscopy based sensors. [ABSTRACT FROM AUTHOR]

Tuning the rheological properties of bitumens is extremely important for applicative purposes. This can be achieved by the use of chemical additives tuning the asphaltene-asphaltene and asphaltene-maltene interactions. We propose the use of an epoxy-resin to give more rigid and thermally stable bitumens on the basis of its tendency to form polymeric networks which would bridge asphaltene clusters. Rheometry confirmed this hypothesis and showed that a load of epoxy-resin as low as 0.1% gives the highest rigidity. Atomic Force Microscopy highlighted the structural changes at the basis of the observed effects. The small amount of epoxy resin needed and its low-cost are elements deserving monitoring. [ABSTRACT FROM AUTHOR]

Keratoconus is the primary cause of corneal transplantation in young adults worldwide. Riboflavin/UV‐A corneal cross‐linking may effectively halt the progression of keratoconus if an adequate amount of riboflavin enriches the corneal stroma and is photo‐oxidated by UV‐A light for generating additional cross‐linking bonds between stromal proteins and strengthening the biomechanics of the weakened cornea. Here we reported an UV‐A theranostic prototype device for performing corneal cross‐linking with the ability to assess corneal intrastromal concentration of riboflavin and to estimate treatment efficacy in real time. Seventeen human donor corneas were treated according to the conventional riboflavin/UV‐A corneal cross‐linking protocol. Ten of these tissues were probed with atomic force microscopy in order to correlate the intrastromal riboflavin concentration recorded during treatment with the increase in elastic modulus of the anterior corneal stroma. The intrastromal riboflavin concentration and its consumption during UV‐A irradiation of the cornea were highly significantly correlated (R = 0.79; P = .03) with the treatment‐induced stromal stiffening effect. The present study showed an ophthalmic device that provided an innovative, non‐invasive, real‐time monitoring solution for estimating corneal cross‐linking treatment efficacy on a personalized basis. [ABSTRACT FROM AUTHOR]

Abstract: In the aim to get high quality graphene films, with large domains and free from impurities, minimizing also the manufacturing costs, we investigate the graphene grown on copper (Cu) foil by chemical vapor deposition at ambient pressure conditions, by using methane (CH4) as carbon source, diluted in a suitable mixture of argon (Ar) and hydrogen (H2). Several graphene samples were synthesized, for variable exposure times to hydrocarbon precursor, in the range from 1 min to 1 hr. The quality of the graphene films and their structural, morphological, and electronic properties were evaluated by micro‐Raman spectroscopy and other techniques, including, scanning tunneling microscopy, atomic force microscopy, and scanning electronic microscopy. In particular, samples obtained with shorter growth time (less than 10 min) exhibit a non‐uniform coverage of the Cu surface, whereas those synthesized with exposure time between 10 and 30 min show a prevalence of well‐ordered monolayer graphene domains. For longer deposition, the amount of disordered domains increases, as revealed by Raman analysis, and the resulting film shows a nonself‐limiting growth behavior for chemical vapor deposition at atmospheric conditions. In addition, we observed 2 kinds of monolayer graphene, in terms of coupling with the Cu surface, for the samples synthesized between 10 and 30 min. To the best of our knowledge, “coupled” and “decoupled” graphene regions have never been reported at the same time on Cu surface. Furthermore, a Raman statistical analysis has been performed on the G and 2D bands measured in both the kinds of regions, gaining evidence of a bimodal behavior for the graphene spots, corresponding to “coupled” and “decoupled” configurations. This difference, which is appreciable also by the optical microscopy inspection, could be related to the local Cu oxidation and to oxygen intercalation after graphene growth. [ABSTRACT FROM AUTHOR]

Due to the wide variation in geographic and climatic conditions, the search for high-performance bituminous materials is becoming more and more urgent to increase the useful life of pavements and reduce the enormous cost of road maintenance. Extensive research has been done by testing various bitumen modifiers, although most of them are petroleum-derived additives, such as polymers, rubbers and plastic, which in turn do not prevent oxidative aging of the binder. Thus, as an alternative to the most common polymeric rheological modifiers, selected binder additives falling in the categories of organosilane (P2KA), polyphosphoric acid (PPA) and food grade phospholipids (LCS) were homogeneously mixed to a base bitumen. The goal was to analyse the micro-morphology of the bitumens (neat and modified) subjected to different cooling rates and to find the corresponding correlations in the mechanical response domain. Therefore, microstructural investigations carried out by Atomic Force Microscopy (AFM) and fundamental rheological tests based on oscillatory dynamic rheology, were used to evaluate the effect of additives on the bitumen structure and compared with pristine binder as a reference. The tested bitumen additives have been shown to elicit different mechanical behaviours by varying the cooling rate. By comparing rheological data, analysed in the framework of the "weak gel" model, and AFM images, it was found that both P2KA and PPA altered the material structure in a different manner whereas LCS revealed superior performances, acting as "mechanical buffer" in the whole explored range of cooling rates. [ABSTRACT FROM AUTHOR]

Measuring temperatures at small scales, especially around nanoparticles, is a crucial step for a variety of applications in biomedicine and in optics. Here, we report on a novel method to map temperature in the medium surrounding silver nanoparticles dispersing them in a thermochromic mixture prepared using an organic dye and a polymer. When the nanocomposite is irradiated with visible light, nanoparticles convert light into heat and the nanocomposite changes its colour. The temperature around silver nanoparticles can be, then, easily evaluated from this colour variation. The proposed method can be implemented in temperature monitoring devices of the nanoparticles surrounding media. [ABSTRACT FROM AUTHOR]

Rewritable optical storage has been obtained in a spiropyran doped liquid crystal polymer films. Pictures can be recorded on films upon irradiation with UV light passing through a grayscale mask and they can be rapidly erased using visible light. Films present improved photosensitivity and optical contrast, good resistance to photofatigue, and high spatial resolution. These photochromic films work as a multifunctional, dynamic photosensitive material with a real-time image recording feature. [ABSTRACT FROM AUTHOR]

The gold nanoparticle (GNP) aggregation growth induced by deoxyribonucleic acid (DNA) is studied by laser scanning confocal and environmental scanning electron microscopies. As in the investigated case the direct light scattering analysis is not suitable, we observe the behavior of the fluorescence produced by a dye and we detect the aggregation by the shift and the broadening of the fluorescence peak. Results of laser scanning confocal microscopy images and the fluorescence emission spectra from lambda scan mode suggest, in fact, that the intruding of the hydrophobic moiety of the probe within the cationic surfactants bilayer film coating GNPs results in a Förster resonance energy transfer. The environmental scanning electron microscopy images show that DNA molecules act as template to assemble GNPs into three-dimensional structures which are reminiscent of the DNA helix. This study is useful to design better nanobiotechnological devices using GNPs and DNA. [ABSTRACT FROM AUTHOR]