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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]

Abstract This paper presents Atomic Force Microscopy (AFM) as a powerful alternative to the more commonly used tensile tests for the analysis of the mechanical properties of polymeric membranes. The Young's modulus measurements by the traditional tensile tests were compared with AFM operated in Force Spectroscopy mode. AFM measurements were carried out with nanometric and micrometric tips on dense membranes of neat Pebax®1657 and on mixed matrix membranes of Pebax®1657 with different concentrations of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF 4 ]. The use of a nanometric AFM tip enables the determination of the local Young's modulus of the individual domains of the microphase-separated block-copolymer, while a larger tip gives average values of the bulk polymer. We found excellent correlation between the data obtained with common tensile tests and those obtained in compression by AFM with the micrometric tip, with important additional information on morphological features, when using the nanometric tip. This offers good perspectives for the analysis of samples where traditional tensile tests cannot be used, for instance composite membranes or particularly small samples. Graphical abstract Image Highlights • Self-standing [BMIM][BF 4 ]/Pebax®1657 membranes were successfully prepared. • AFM force spectroscopy determines mechanical properties of membranes. • Good quantitative agreement between tensile tests and force spectroscopy. • Nano-scale and bulk properties can be analysed, depending on the tip size. • A silicon environment reduces capillary forces and improves data quality. [ABSTRACT FROM AUTHOR]

This work presents a laser spectroscopy based method to detect very small amounts of acidic molecules in concentrations down to 10 ppm. The proposed method relies on the sensitivity to acids of a fluorescent dye, which is used as the active material in a stimulated laser emission experiment. Using a cuvette, that works as a resonator, laser emission from a dye doped mixture can be observed. When an acidic species is added to the mixture, due to the solvatochromic effect, the spectral position of fluorescence shifts and, consequently, a shift in the emitted laser wavelength is observed. From the analysis of the laser lines the presence of a specific acid species and its concentration can be determined. [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]

• Observation of an evident induced chirality in Sunset Yellow (SSY) microspheres. • Explanation of the aggregation mechanism for chiral dopants in SSY. • Polarized Optical images of rich microspheres textures. • Texture modulation of SSY microspheres by ionic salts. The reflection symmetry breaking observed in chromonic liquid crystals confined in different geometries, like tactoids, microspheres or capillaries, has been the focus of researchers in the last few years. Although the assembly mechanism that drives this behavior is common to most chromonic materials, the interface phenomena and the induced chirality are strongly dependent on the chromonic molecule itself. In this work, we report advances in understanding the supramolecular arrangement and induced chirality for the chromonic molecule Sunset Yellow and its interaction with salts and l -peptides. By means of optical microscopy, X-ray diffraction and atomic force microscopy, we demonstrate the rise of enhanced chirality in Sunset Yellow microspheres and propose an explanation of this phenomenon through two possible mechanisms: intercalation of the chiral dopant or binding. Our findings on the capability to control the delicate thermodynamic balance among chromonics, ions, chiral dopants, and water and its kinetics may open new perspectives for using these microspheres in optical and sensing applications. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the viscoelastic changes of the human cornea induced by riboflavin/UV-A cross-linking using Atomic Force Microscopy (AFM) at the nano level. Methods: Seven eye bank donor corneas were investigated, after gently removing the epithelium, using a commercial AFM in the force spectroscopy mode. Silicon cantilevers with tip radius of 10 nm and spring elastic constants between 26- and 86-N/m were used to probe the viscoelastic properties of the anterior stroma up to 3 µm indentation depth. Five specimens were tested before and after riboflavin/UV-A cross-linking; the other two specimens were chemically cross-linked using glutaraldehyde 2.5% solution and used as controls. The Young’s modulus (E) and the hysteresis (H) of the corneal stroma were quantified as a function of the application load and scan rate. Results: The Young’s modulus increased by a mean of 1.1-1.5 times after riboflavin/UV-A cross-linking (P<0.05). A higher increase of E, by a mean of 1.5-2.6 times, was found in chemically cross-linked specimens using glutaraldehyde 2.5% (P<0.05). The hysteresis decreased, by a mean of 0.9-1.5 times, in all specimens after riboflavin/UV-A cross-linking (P<0.05). A substantial decrease of H, ranging between 2.6 and 3.5 times with respect to baseline values, was observed in glutaraldehyde-treated corneas (P<0.05). Conclusions: The present study provides the first evidence that riboflavin/UV-A cross-linking induces changes of the viscoelastic properties of the cornea at the scale of stromal molecular interactions. [ABSTRACT FROM AUTHOR]

Highlights: [•] The alignment of LC guanosine phases, both planar and homeotropic, could be achieved using different surface energy alignment layers. [•] LC guanosine solutions could be aligned homeotropically confining them between hydrophobic surfaces, without the help of external field. [•] Without modifying the guanine base, we observed metastable guanosine vesicles between two silicon based confining surfaces. [•] It is possible to control the pitch of the helix structure, adding salts to LC guanosine phases. [Copyright &y& Elsevier]

Abstract: We showed the capabilities and accuracy of atomic force microscopy (AFM) techniques for imaging and analyzing the corneal epithelium and the photoablated corneal stroma. Eight normal porcine corneas, half of which were ablated using a scanning-spot excimer laser, were examined. All the corneas were imaged in balanced salt solution after fixation in glutaraldehyde. In the normal untreated corneas we observed the epithelial surface showing the typical polygonal cells and presenting numerous microprojections. The superficial epithelial cells were classified in three types as a result of the anterior-surface roughness measurements. AFM images of the photoablated corneal specimens showed undulations and granule-like features on the ablated stromal surface, specific to 193-nm ArF laser irradiation. Nevertheless, the quantitative analysis confirmed the precision of excimer laser surgery in removing sub-micrometric amounts of tissue. AFM showed to be a high-resolved imaging tool for the scanning of both native as well as photoablated corneal specimens. Also, this technique permits precise topographic analysis of the corneal plane, in the nanometric scale, of which smoothness is an important physical characteristic and necessary to achieve an optimal optical quality of the eye. [Copyright &y& Elsevier]

Purpose: To analyze the surface optics of 4 currently available intraocular lenses (IOLs) with atomic force microscopy. Setting: Licryl Laboratory, University of Calabria, Rende, Italy. Methods: The surface roughness and topography of poly(methyl methacrylate) (PMMA), silicone, hydrophobic, and hydrophilic acrylic IOLs were evaluated with atomic force microscopy in contact mode. The analysis was performed in a liquid environment using cantilevers with a 0.01 Newtonw/meter nominal elastic constant. Measurements were made over areas of 10 μm2 on different locations of the posterior optic surface of the IOL. Results: Atomic force microscopy permitted high-resolution imaging of IOL optic surface characteristics. Surface topography showed different features with respect to the lens biomaterial. The root-mean-square roughness of the IOL optic surface was significantly different between lenses of various materials (P<.001). The hydrophobic acrylic and silicone IOLs had the lowest mean surface roughness, 3.8 nm ± 0.2 (SD) and 4.0 ± 0.5 nm, respectively, and the 2 PMMA IOLs had the highest mean surface roughness, 6.6 ± 0.3 nm and 7.0 ± 0.6 nm. Conclusions: Atomic force microscopy was effective and accurate in analyzing IOL optics. The surface topography of IOLs may vary with different manufacturing processes. [Copyright &y& Elsevier]

The creation of partial or complete human epidermis represents a critical aspect and the major challenge of skin tissue engineering. This work was aimed at investigating the effect of nano- and micro-structured CHT membranes on human keratinocyte stratification and differentiation. To this end, nanoporous and microporous membranes of chitosan (CHT) were prepared by phase inversion technique tailoring the operational parameters in order to obtain nano- and micro-structured flat membranes with specific surface properties. Microporous structures with different mean pore diameters were created by adding and dissolving, in the polymeric solution, polyethylene glycol (PEG Mw 10,000 Da) as porogen, with a different CHT/PEG ratio. The developed membranes were characterized and assessed for epidermal construction by culturing human keratinocytes on them for up to 21 days. The overall results demonstrated that the membrane surface properties strongly affect the stratification and terminal differentiation of human keratinocytes. In particular, human keratinocytes adhered on nanoporous CHT membranes, developing the structure of the corneum epidermal top layer, characterized by low thickness and low cell proliferation. On the microporous CHT membrane, keratinocytes formed an epidermal basal lamina, with high proliferating cells that stratified and differentiated over time, migrating along the z axis and forming a multilayered epidermis. This strategy represents an attractive tissue engineering approach for the creation of specific human epidermal strata for testing the effects and toxicity of drugs, cosmetics and pollutants. [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]

Vesicle fusion is a fundamental cell biological process similar from yeasts to humans. For secretory vesicles, swelling is considered a step required for the expulsion of intravesicular content. Here this concept is revisited providing evidence that it may instead represent a general mechanism. We report the first example that non-secretory vesicles, committed to insert the Aquaporin-2 water channel into the plasma membrane, swell and this phenomenon is required for fusion to plasma membrane. Through an interdisciplinary approach, using atomic force microscope (AFM), a fluorescence-based assay of vesicle volume changes and NMR spectroscopy to measure water self-diffusion coefficient, we provide evidence that Gi protein modulation of potassium channel TASK-2 localized in AQP2 vesicles, is required for vesicle swelling. Estimated intravesicular K+ concentration in AQP2 vesicles, as measured by inductively coupled plasma mass spectrometry, was 5.3 mM, demonstrating the existence of an inwardly K+ chemical gradient likely generating an osmotic gradient causing vesicle swelling upon TASK-2 gating. Of note, abrogation of K+ gradient significantly impaired fusion between vesicles and plasma membrane. We conclude that vesicle swelling is a potentially important prerequisite for vesicle fusion to the plasma membrane and may be required also for other non-secretory vesicles, depicting a general mechanism for vesicle fusion. [ABSTRACT FROM AUTHOR]

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]

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]

Highlights • The structural effects of additives for bitumen. • Wide Angle X ray Scattering (WAXS) explores the influence of additives on the bitumen structure. • Apolar Additive are preferentially located in the maltene phase weakening asphaltene inter-clusters interactions. Abstract Bitumens are composite materials whose complex organization hinders the rational understanding of their relationships between composition, structure and performances. So, research attempting to shed more light in this field is required. In this work Wide Angle X ray Scattering (WAXS) has been used to explore the influence of six opportunely chosen additives on the bitumen structure with the aim to ultimately correlate the findings with the bitumen performances. Diagnostic fingerprints have been observed in the WAXS profile: asphaltenes form stuck of about 18 Å and constituted by about 6 asphaltene units on average. Such stucks are, in turn, organized at higher levels of complexity forming anisotropic aggregates of about 200 Å × 28 Å which, again, are assembled to form micrometer-size elongated aggregates characterized by the so-called bee-structure. The structural effects of the six opportunely chosen additives (Organosilane, Polyphosphoric, Phospholipids, Acetamidophenol, Oleic Acid, octadecylamine) have been pointed out and, corroborated by AFM images, have been correlated with the rheological behavior and justified at the microscopic level: additive with an apolar nature are preferentially located in the maltene phase weakening asphaltene inter-clusters interactions and softening the bitumen, whereas, on the contrary more polar additives act in opposite directions. Peculiar behavior have been unveiled in the case of amphiphilic additive due to the simultaneous presence, within their molecular architecture, of both polar and apolar moieties. The knowledge of the detailed effect of appropriately chosen additives on the nanoscopic and mesoscopic structure and their correlation with the rheological properties constitute the first step for opening the door to the piloted design of new bitumens with desired properties for ad-hoc uses. [ABSTRACT FROM AUTHOR]

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]

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]

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]

Amongst emerging Transition Metal Dichalcogenides (TMDCs), molybdenum disulfide (MoS 2) has attracted a remarkable interest thanks to many possible applications. In particular, MoS 2 has potentialities not yet fully realized in solution-based applications. However, the lack of knowledge of the optical properties of MoS 2 has significantly limited its use in many exciting photonic fields. Films prepared by solution-based exfoliation methods have never been studied to our best knowledge. The optical properties of MoS 2 films prepared by solution-based exfoliation methods have never been studied to our best knowledge. Herein, the broadband optical properties of ~20 nm-thick MoS 2 films deposited by spin-coating onto Si/SiO 2 substrates were studied by means of micro-Raman spectroscopy and Variable Angle Spectroscopic Ellipsometry (VASE). •Micro-Raman measurements of spin-coated MoS 2 films. •Micro-Raman measurements reveal the possible coexistence of 2H/1T MoS 2 phases. •VASE measurements of spin-coated MoS 2 films in a broadband photon energy range. •Dielectric response of MoS 2 films described using seven Lorentz oscillators. [ABSTRACT FROM AUTHOR]

[Display omitted] • Role of molecular flexibility in chromonic self assembly. • Enhancement of chirality by spherical confinement. • Design of novel materials. Chromonic liquid crystals are a sub-category of lyotropic liquid crystalline materials whose self-assembling mechanisms in complex supramolecular structures are still not fully understood. Chirality can be induced in chromonics using chiral aminoacids with alternating results. Understanding the key factors that lead to maximize this phenomenon is important for the design of novel materials able to self-assemble in chiral macroscopic structures with tailored optical properties, as selective reflection. In this work, we present a comparative study involving a not commercial chromonic, a synthesized metal containing chromonic compound [(Bpy-OH) 2 Ag][CH 3 COO]H 2 O, and two model chromonics that behave in different manner with respect to chiral induction. Spherical confinement provides a quick way to qualitatively evaluate the elasticity properties in new materials. Also, optical textures of the metal compound, after doping the material with a chiral moiety, show that its chiral phase is more similar to one of the two model chromonics. This observation points to a role played by the flexibility of the molecular structure that it's reflected into the resistance of the columnar aggregates to undergo a twist. This last observation can be useful when selecting the most suitable building blocks in designing new materials. [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]

This research presents a laboratory study on a polymer-modified bitumens (PMBs) made with a vacuum residue (VR) as a bitumen extender. Two different PMBs were prepared, one with a plastomeric Elvaloy and the other one with an elastomeric styrene-butadiene-styrene SBS. The mechanical properties of the samples were determined by means Multi Stress Creep Recovery tests (MSCR) and temperature sweep test. The results show that polymers can improve the mechanical properties of bitumen, and the vacuum residue can be used as softening bitumen extender. However, their simultaneous presence highlights non-additive effects giving optimal mechanical properties with a lowered temperature dependence of the viscoelastic properties and a high extension of the usage temperature range. The peculiar effect of the combined action of polymers and vacuum residue was also confirmed by chemical-physical analyses. In fact, Atomic Force Microscopy (AFM) and Nuclear Magnetic Resonance (NMR) relaxometry have shown that vacuum residue and polymers are able to effectively interact with the inner structures of the bitumen to give enhanced performances, with an increased stability upon temperature changes. [Display omitted] [ABSTRACT FROM AUTHOR]

This research presents a laboratory study on a polymer-modified bitumens (PMBs) made with a vacuum residue (VR) as a bitumen extender. Two different PMBs were prepared, one with a plastomeric Elvaloy and the other one with an elastomeric styrene-butadiene-styrene SBS. The mechanical properties of the samples were determined by means Multi Stress Creep Recovery tests (MSCR) and temperature sweep test. The results show that polymers can improve the mechanical properties of bitumen, and the vacuum residue can be used as softening bitumen extender. However, their simultaneous presence highlights non-additive effects giving optimal mechanical properties with a lowered temperature dependence of the viscoelastic properties and a high extension of the usage temperature range. The peculiar effect of the combined action of polymers and vacuum residue was also confirmed by chemical-physical analyses. In fact, Atomic Force Microscopy (AFM) and Nuclear Magnetic Resonance (NMR) relaxometry have shown that vacuum residue and polymers are able to effectively interact with the inner structures of the bitumen to give enhanced performances, with an increased stability upon temperature changes. [Display omitted] [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Micro-Raman investigation of graphene on Si/SiO 2 substrate. • Optical properties of CVD graphene in a broad energy range using ellipsometry. • Discussion on the unintentional doping of the sample. Abstract Despite intensive investigations in the UV (ultraviolet) and visible range, the research on the optical properties of graphene in the extended near and mid infrared range by means of Spectroscopic Ellipsometry (SE) remains limited yet. Herein, the optical properties of a Chemical Vapor Deposition (CVD)-grown monolayer graphene, transferred from a copper substrate onto SiO 2 /Si, were studied in the broad energy range (0.38–6.2 eV) using Variable Angle Spectroscopic Ellipsometry (VASE). The morphological and the structural properties of the samples were investigated by Micro-Raman Spectroscopy, Wavelength Dispersive X-ray (WDX) analysis, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The Lorentz oscillator model proposed for the optical response of graphene fits very well the experimental data. An unintentional doping, revealed by Micro-Raman Spectroscopy and WDX, is reported. [ABSTRACT FROM AUTHOR]

The growth of graphene on copper foil has been performed, following the well-known low-pressure chemical vapor (LP-CVD) procedure. The as-deposited monolayer graphene clearly exhibits two different coupling behaviors with the metal substrate, as demonstrated by visual microscopic investigation and by other experimental techniques, like Scanning Electron Microscopy (SEM) and micro-Raman spectroscopy. The single graphene sheet shows both large areas where it is coupled to the metal substrate and others where it exhibits freestanding-like characteristics. This phenomenology appears to be related to oxidation of the copper surface. In addition, we demonstrate the possibility to induce a variation of the coupling state by visible-light irradiation above a proper power threshold. The resulting change of the coupling with the metal substrate is associated to a local variation of the work function. Applications in high-performance electronic devices can be suitably tailored by optical methods and, in principle, by any local probe producing “hot spots” such as Scanning Tunneling Microscopy (STM) tips and electron beams. [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]

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]

In the last years the potential of combining the attractive materials characteristics of graphene related materials and silver nanostructures for SERS and metamaterials has emerged. Here, we report of graphene oxide thin films deposited by dip-coating on magnetron sputtered silver thin films. Our work represents a novelty in the field of the study of graphene oxide- silver composites, since magnetron sputtering deposition is an alternative way to silver thin films fabrication; previous works used instead silver nitrate aqueous solution mixed with the graphene oxide. Micro-Raman technique, morphological analysis and variable angle spectroscopic ellipsometry were performed. The final SERS signal intensity was investigated and we found Raman peaks dependent on the intensity of the laser and the thickness of silver and GO films. These results could open somestudies on plasmonics and on the reduction of graphene oxide mediated by silver thin films. Moreover, effective medium theory calculations show the possible use of these graphene oxide/silver thin films in multilayer hyperbolic metamaterials for optical applications. [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]

Several phenolic compounds bind to proteins and show the ability to interfere with their aggregation process. The impact of the natural polyphenol resveratrol on the stability and heat induced aggregation of human serum albumin (HSA) was investigated by differential scanning calorimetry (DSC), attenuated total reflectance Fourier transform infrared (ATR-FTIR), UV–vis absorbance, ThT fluorescence, atomic force microscopy (AFM) and molecular modeling. The binding of resveratrol to HSA improves the stability of the protein to thermal unfolding, particularly for the energetic domain containing the ligand binding site, as modeled by computational techniques. The thermal unfolding is irreversible and after the melting the protein aggregates, either with or without the ligand. The kinetics of HSA aggregation between 70 and 80 °C shows an exponential growth of the absorbance change and it slows down when resveratrol is added. The aggregates have fibril-like morphology and resveratrol attenuates the formation of β-structured species. The overall results suggest that resveratrol stabilizes the protein structure and modulates the formation of fibrils along the initial stage of the HSA aggregation pathway. [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]

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]

Purpose: To analyze the interface quality of the anterior stroma after femtosecond laser flap creation using atomic force microscopy. Setting: IRCCS Fondazione G.B. Bietti, Rome, Italy. Design: Experimental study. Methods: A 110 μm depth flap was created in 20 human corneal tissues using a femtosecond laser platform (Intralase iFS). Tissues were divided into 4 groups of various cutting parameters: pulse energy and spot separation of 0.75 μJ and 6 μm (Group 1), 0.65 μJ and 5 μm (Group 2), 0.55 μJ and 4 μm (Group 3), and 0.45 μJ and 4 μm (Group 4). Four additional tissue sections were cut using a motorized microkeratome (Hansatome). Atomic force microscopy (Autoprobe CP) analysis was performed on the stromal bed of each sample. Results: The corneal tissues treated with higher pulse energies and wider spot separations (Groups 1 and 2) showed a rougher stromal bed interface (root mean square [RMS] rough = 0.23 μm ± 0.008 (SD) and 0.24 ± 0.009 μm, respectively) than tissues in Groups 3 and 4 (RMS rough = 0.18 ± 0.006 μm and 0.18 ± 0.008 μm, respectively; P<.001, 1-way analysis of variance). The stromal surface quality of tissues treated with pulse energies of 0.55 μJ or lower and 4 μm spot separation compared favorably with that of tissues cut by the microkeratome (RMS rough = 0.17 ± 0.006 μm; P>.05, Tukey). Conclusions: The femtosecond stromal interface quality was improved with pulse energy lower and spot separations narrower than those currently used in the clinical setting. The flap interface smoothness created by the femtosecond laser was comparable to that created by the microkeratome. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. [ABSTRACT FROM AUTHOR]

A new type of intrinsic photoconductor was used as a donor in bulk heterojunction solar cells, in blends with PCBM. The donor is a square planar cyclopalladated coordination complex, with a Nile red moiety and a Schiff base as ligands, coordinated by a Pd(II) metal center. The photoconducting properties of the complex were characterized. Photovoltaic devices exhibit low performance, but the analysis of the wavelength dependence of the efficiency reveals a much higher photocurrent upon absorption of the complex, when compared to the photocurrent obtained via absorption by PCBM. This effect is tied to the higher tendency of the intrinsic photoconductor towards exciton dissociation at the heterojunction. [ABSTRACT FROM AUTHOR]

Purpose: To analyze intraocular lens (IOL) optic surface adhesiveness using atomic force microscopy (AFM). Setting: LiCryL Laboratory, University of Calabria, Rende, Italy. Methods: The surface adhesive properties of poly(methyl methacrylate) (PMMA), silicone, hydrophilic acrylic, and hydrophobic acrylic IOLs were evaluated by AFM. Analysis was performed at room temperature (21°C) in a liquid environment using the force-versus-distance mode of a commercial instrument (NanoScope III). Measurements were acquired with rectangular silicon cantilevers of a nominal elastic constant of 10 Newton/m. The nominal value of the tip''s radius of curvature was 1 μm, and the scanning speed during the acquisitions ranged from 10 to 400 nm/s. Results: The adhesion force measurements showed different characteristics for the various types of IOLs (P<.001, analysis of variance). The hydrophobic acrylic IOL had the largest mean adhesive force (283.75 nanoNewton [nN] ± 0.14 [SD]) followed by the hydrophilic acrylic (84.76 ± 0.94 nN), PMMA (45.77 ± 0.47 nN), and silicone (2.10 ± 0.01 nN) IOLs. Conclusions: The surface properties of the biomaterials used to manufacture IOLs are important because they can influence the incidence and severity of posterior capsule opacification (PCO). Although further studies are necessary to elucidate the mechanism of PCO development and the interface interactions between the IOL and capsule, the results in this study may bolster the theory of manufacturing more-adhesive materials to prevent PCO. [Copyright &y& Elsevier]

Spin coated films of a chiral comb-like liquid crystalline copolymer containing azobenzene chromophores in its side chains are optically isotropic in their twisted smectic-like glassy state. In contact with a nematic liquid crystal (5CB, E7, MBBA) they provide a degenerate planar orientation. When irradiated by unpolarized UV light, they orient the same nematics homeotropically. Treated with linearly polarized UV light they orient nematics homogeneously with the director along the electric vector of the exciting light. After a combined irradiation first with unpolarized UV light and then with linearly polarized visible light, the films again provide a homogeneous liquid crystal orientation, this time with the director perpendicular to the visible light electric vector. The phenomena observed are related to the light induced optical anisotropy. Two main processes are responsible for the anisotropy (1) a UV light depletion of trans-isomers of the azobenzene chromophores from the chosen direction and (2) a reorientation of the chromophores by polarized visible light. [ABSTRACT FROM AUTHOR]

Over the years, the need for the synthesis of biodegradable materials has facilitated the drift of the asphalt industry towards eco-sustainable and cost-effective production of road pavements. The principal additives in the asphalt industry to improve the performance of road pavements and increase its lifespan are majorly rheological modifiers, adhesion promoters and anti-oxidant agents. Rheological modifiers increase physico-chemical properties such as transition temperature of asphalt binder (bitumen), adhesion promoters increase the affinity between binder and stone aggregates while anti-oxidant agents reduce the effects of oxidation caused by exposure to air, water and other natural elements during the production of asphalt pavements. In this study, we tested the effectiveness of a food grade bio-additive on these three aforementioned properties. We also sought to hypothesize the mechanisms by which the additive confers these desired features on bitumen. We present this study to evaluate the effects of turmeric, a food-based additive, on bitumen. The study was conducted through dynamic shear rheology (DSR), atomic force microscopy, scanning electron microscopy (SEM) and boiling test analysis. [ABSTRACT FROM AUTHOR]

This manuscript describes the gas separation performance of PIM-2, a partially fluorinated linear copolymer synthesized from 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethylspirobisindane (TTSBI) and decafluorobiphenyl (DFBP). As one of the early members of the family of polymers of intrinsic microporosity, it had never been tested as a gas separation membrane because of insufficient mechanical resistance. This has been solved only recently, allowing the preparation of robust self-standing films. Molecular modelling studies demonstrated a high fractional free volume (34%) and an elevated surface area (642 m2 g−1), and the latter is in good agreement with experimental BET results. Pure gas permeabilities measured on a fixed-volume time-lag instrument at 1 bar compare well with the results of mixed separation tests on a variable volume setup from 1-6 bar(a). Molecular modelling and independent sorption measurements on a gravimetric sorption balance both show strong dual-mode sorption behaviour, especially for CO 2 and to a lesser extent for CH 4. Temperature-dependent pure gas permeation measurements show typical Arrhenius behaviour, with a clear increase in the activation energy for diffusion with the increasing molecular size of the gas, indicating high size-selectivity. This is in agreement with the highly rigid PIM structure, determined by AFM force spectroscopy measurements. The dual-mode behaviour results in a moderate pressure dependence of the CO 2 permeability and the CO 2 /N 2 and CO 2 /CH 4 selectivity, all slightly decreasing with increasing pressure. The presence of humidity in the gas stream has a remarkable small effect on the membrane performance, which is probably due to the high fluorine content and the consequently low water vapour solubility in the polymer, as confirmed by gravimetric sorption measurements. The manuscript describes an extensive study on the structure-property relationships in PIM-2. Image 1 • Fluorinated PIM-2 forms robust self-standing membranes. • CO 2 /N 2 and CO 2 /CH 4 mixed gas separation data lie close to the 2008 upper bound. • Separation performance is hardly affected by the presence of humidity in the feed gas. • Water sorption is very low due to the hydrophobic nature of the fluoropolymer. • MD simulations show how halogen bond networks enhance the energetic diffusion selectivity. [ABSTRACT FROM AUTHOR]

This work describes the observation of lasing in an intermediate chiral phase of a dye-doped cholesteric liquid crystal mixture. This intermediate phase exists between cholesteric and smectic A phase and it presents anomalous selective reflection properties. The lasing was observed at the long-wavelength edge of the photonic band gap. [ABSTRACT FROM AUTHOR]

Mitochondrial DNA (mtDNA) plays a key role in the development of a competent oocyte. In this study, the complete mtDNA sequence obtained for the first time by multiple displacement amplification approach in combination with next-generation sequencing from a single human oocyte is reported (GenBank accession no. KT364276). The analysis of oocyte mitochondrial mutations could provide a better understanding of the genetic variants correlated with the oocyte quality. [ABSTRACT FROM PUBLISHER]

Three photosensitive cholesteric liquid crystal mixtures have been investigated as UV sensors. Each of them is sensitive to a well definite part of the solar UV radiation spectrum, the UV A or the UV B or the UV C range, with suitable absorption spectra. The photosensitive elements in the mixtures are either photoisomerizable nematic hosts or photoisomerizable optically active dopants. The selective reflection peaks of these cholesteric mixtures are in the visible part of the light spectrum. The UV exposure changes the cholesteric pitch and hence the position of the selective reflection peak. The consequence is that the colour reflected by each mixture varies under influence of the UV and it can be used as an indicator of the UV exposure itself. We present the mechanisms of the observed effects and possible application features. [ABSTRACT FROM AUTHOR]