Chemical reactions on surfaces for applications in catalysis, gas sensing, adsorption-assisted desalination and Li-ion batteries: opportunities and challenges for surface science.

The study of chemical processes on solid surfaces is a powerful tool to discover novel physicochemical concepts with direct implications for processes based on chemical reactions at surfaces, largely exploited by industry. Recent upgrades of experimental tools and computational capabilities, as well as the advent of two-dimensional materials, have opened new opportunities and challenges for surface science. In this Perspective, we highlight recent advances in application fields strictly connected to novel concepts emerging in surface science. Specifically, we show for selected case-study examples that surface oxidation can be unexpectedly beneficial for improving the efficiency in electrocatalysis (the hydrogen evolution reaction and oxygen evolution reaction) and photocatalysis, as well as in gas sensing. Moreover, we discuss the adsorption-assisted mechanism in membrane distillation for seawater desalination, as well as the use of surface-science tools in the study of Li-ion batteries. In all these applications, surface-science methodologies (both experimental and theoretical) have unveiled new physicochemical processes, whose efficiency can be further tuned by controlling surface phenomena, thus paving the way for a new era for the investigation of surfaces and interfaces of nanomaterials. In addition, we discuss the role of surface scientists in contemporary condensed matter physics, taking as case-study examples specific controversial debates concerning unexpected phenomena emerging in nanosheets of layered materials, solved by adopting a surface-science approach.

Near Room Temperature Light-Activated WS2-Decorated rGO as NO2 Gas Sensor.

The NO2 response in the range of 200 ppb to 1 ppm of a chemoresistive WS2-decorated rGO sensor has been investigated at operating temperatures of 25 °C and 50 °C in dry and humid air (40% RH) under dark and Purple Blue (PB) light conditions (λ = 430 nm). Few-layers WS2, exfoliated by ball milling and sonication technique, with average dimensions of 200 nm, have been mixed with rGO flakes (average dimension 700 nm) to yield WS2-decorated rGO, deposited on Si3N4 substrates, provided with platinum (30 µm gap distance) finger-type electrodes. TEM analysis showed the formation of homogeneous and well-dispersed WS2 flakes distributed over a thin, continuous and uniform underlying layer of interconnected rGO flakes. XPS and STEM revealed a partial oxidation of WS2 flakes leading to the formation of 18% amorphous WO3 over the WS2 flakes. PB-light irradiation and mild heating of the sensor at 50 °C substantially enhanced the baseline recovery yielding improved adsorption/desorption rates, with detection limit of 400 ppb NO2 and reproducible gas responses. Cross sensitivity tests with humid air interfering vapor highlighted a negligible influence of water vapor on the NO2 response. A charge carrier mechanism between WS2 and rGO is proposed and discussed to explain the overall NO2 and H2O response of the WS2-rGO hybrids.

Pyrrolidone Modification Prevents PAMAM Dendrimers from Activation of Pro-Inflammatory Signaling Pathways in Human Monocytes.

The biological features of dendrimers are affected by the character of highly reactive terminal moieties. In some polyamine dendrimer types the surface charge makes them bioincompatible and prevent their direct medical application. Moreover, foreign particles can induce the immune response which is undesirable due to the adverse side effects in vivo. The reduction of cytotoxicity of positively charged macromolecules is possible through chemical modifications of terminal groups. In our study, we have developed new derivatives of PAMAM dendrimers modified with 4-carbomethoxypyrrolidone and evaluated their immunomodulatory properties. The experiments were conducted on two human cancer myeloid cell lines: THP-1 and U937. To evaluate the cytotoxicity of dendrimers, the reasazurin assay was applied. The expression level of NF-κB targets (NFKBIA, BTG2) and cytokine genes (IL1B, TNF) was determined by quantitative real-time RT-PCR. The measurement of binding of NF-κB to a consensus DNA probe was determined by electrophoretic mobility shift assay. The ELISA cytokine assay was performed to measure protein concentration of IL-1ß and TNFα. We have found that PAMAM-pyrrolidone dendrimers did not impact THP-1 and U937 viability even at high concentrations (up to 200 µM). The surface modification prevented PAMAM dendrimers from stimulating NF-κB-related signal transduction, which have been determined on the level of nuclear translocation, gene expression and protein secretion. Pyrrolidone modification efficiently prevents PAMAM dendrimers from stimulating pro-inflammatory response in human cancer myeloid cell lines, thus it can be used to improve the biocompatibility of positively charged dendrimers and to broaden the scope of their biological applications.

Evaluation of tetraether lipid-based liposomal carriers for encapsulation and retention of nucleoside-based drugs.

Although liposomal nanoparticles are one of the most versatile class of drug delivery systems, stable liposomal formulation of small neutral drug molecules still constitutes a challenge due to the low drug retention of current lipid membrane technologies. In this study, we evaluate the encapsulation and retention of seven nucleoside analog-based drugs in liposomes made of archaea-inspired tetraether lipids, which are known to enhance packing and membrane robustness compared to conventional bilayer-forming lipids. Liposomes comprised of the pure tetraether lipid generally showed improved retention of drugs (up to 4-fold) compared with liposomes made from a commercially available diacyl lipid. Interestingly, we did not find a significant correlation between the liposomal leakage rates of the molecules with typical parameters used to assess lipophilicity of drugs (such logD or topological polar surface area), suggesting that specific structural elements of the drug molecules can have a dominant effect on leakage from liposomes over general lipophilic character.

Probing DNA-stabilized fluorescent silver nanocluster spectral heterogeneity by time-correlated single photon counting.

DNA-stabilized silver nanoclusters (DNA-AgNCs) are promising fluorophores whose photophysical properties and synthesis procedures have received increased attention in the literature. However, depending on the preparation conditions and the DNA sequence, the DNA-AgNC samples can host a range of different emitters, which can influence the reproducibility of the optical response and the evolution over time of the populations of these emitters. We have developed a simple method to characterize the spectral heterogeneity and time evolution of these emissive species at any given point in time after preparation, by plotting the average decay time as a function of emission wavelength. These so-called average decay time spectra were acquired for different excitation wavelengths of AgNCs stabilized by an oligonucleotide containing 24 cytosines (C24-AgNCs). The average decay time spectra allowed the comparison of sample preparation and the judgment of reproducibility. Therefore, we propose the use of the average decay time spectra as a robust and easy tool to characterize and compare different as-synthesized DNA-AgNC samples. The average decay time spectra can in general also be used to characterize the spectral heterogeneity of other fluorophores, such as luminescent colloidal nanoparticles, and to assess the reproducibility of a synthetic procedure containing an unknown distribution of emissive species.

[Dermatoses in the grocery industry]. / Dermatosi nella grande distribuzione.

Dermatological risks in supermarkets are largely comparable to those found in other workplaces such as food industry and trade in general Using two Pubmed search strings (one more specific, the other more sensitive) 11 papers were found (5 pertinent). The reasons for the little information may be the particular employment conditions that occur , in large-scale distribution. From this derives the difficulty in defining the epidemiology of skin diseases in the field and the need to refer to the literature on skin diseases in food handlers and cashiers. The most frequent dermatological disease in food handlers is irritant contact dermatitis, while the protein contact dermatitis seems to be more widespread than previously thought. Hand eczema together with nickel contact allergy is not rare in cashiers, but it can be difficult to assess if nickel allergy was occupationally acquired.

Skin photoaging in farmers occupationally exposed to ultraviolet radiation.

BACKGROUND: Most personal exposures to UV radiations occur from outdoor activities and several studies detected a significant association between skin cancer and outdoor occupation. OBJECTIVE: The aim of the study was to ascertain the prevalence of photoaging signs in a population of Italian farmers and in a population of indoor workers taking account of confounding factors. METHODS: 169 farmers and 198 indoor workers were classified for skin phototype and for skin photoaging, moreover 13 variables were taken into account. Marginal permutation tests were adopted for statistical analysis. RESULTS: Farmers were significantly older than the indoor workers. In workers occupationally exposed to UV photoaging increased with increasing age and years of occupational exposure to sunlight The distribution of skin phototype did not show significant differences in the two populations, while farmer showed a higher degree of photoaging than indoor workers. CONCLUSIONS: Even if farmers were older than the in door workers it seems that outdoor work produces a higher degree of photoaging.

Bidimensional SnSe2-Mesoporous Ordered Titania Heterostructures for Photocatalytically Activated Anti-Fingerprint Optically Transparent Layers.

The design of functional coatings for touchscreens and haptic interfaces is of paramount importance for smartphones, tablets, and computers. Among the functional properties, the ability to suppress or eliminate fingerprints from specific surfaces is one of the most critical. We produced photoactivated anti-fingerprint coatings by embedding 2D-SnSe2 nanoflakes in ordered mesoporous titania thin films. The SnSe2 nanostructures were produced by solvent-assisted sonication employing 1-Methyl-2-pyrrolidinone. The combination of SnSe2 and nanocrystalline anatase titania enables the formation of photoactivated heterostructures with an enhanced ability to remove fingerprints from their surface. These results were achieved through careful design of the heterostructure and controlled processing of the films by liquid phase deposition. The self-assembly process is unaffected by the addition of SnSe2, and the titania mesoporous films keep their three-dimensional pore organization. The coating layers show high optical transparency and a homogeneous distribution of SnSe2 within the matrix. An evaluation of photocatalytic activity was performed by observing the degradation of stearic acid and Rhodamine B layers deposited on the photoactive films as a function of radiation exposure time. FTIR and UV-Vis spectroscopies were used for the photodegradation tests. Additionally, infrared imaging was employed to assess the anti-fingerprinting property. The photodegradation process, following pseudo-first-order kinetics, shows a tremendous improvement over bare mesoporous titania films. Furthermore, exposure of the films to sunlight and UV light completely removes the fingerprints, opening the route to several self-cleaning applications.

Determinants of bone mineral density, bone mineral content, and body composition in a cohort of healthy children: influence of sex, age, puberty, and physical activity.

Interventions directed to the recognition of abnormal bone mineral density, bone mineral content, and body composition in the pediatric age require the definition of factors influencing bone mass acquisition during growth. We have evaluated in a cross-sectional manner by dual-energy X-ray absorptiometry the impact of sex, age, puberty, and physical activity on total body areal bone mineral density, regional (lumbar and femoral) bone mineral densities, bone mineral content, and body composition (fat mass and lean mass) in a cohort of 359 healthy Italian children aged 3-14 years and investigated their specific contribution to bone mass accrual. Statistical multiple regression analysis was performed dividing the population in pre- and post-pubertal groups. Bone mineral density at the lumbar spine has resulted equally distributed in both sexes before puberty while has resulted higher at the femoral necks in males at whatever age. A significant effect on bone mass acquisition was exerted by male sex and lean mass. In the areas where the cortical bone is prevalent, males of the pre-pubertal group have presented the highest values; in the areas where the cancellous bone is prevalent, both sexes were equivalent until the age of 9 years, but after this age, females have presented higher increases, probably related to the inferior dimensional development of lumbar vertebrae. Conclusively, male sex and lean mass seem to represent independent predictors of bone mass accrual in the cortical bone of the examined children, while female sex and pubertal maturation are independent predictors of bone mass accrual in the trabecular bone.

Vestibular evoked myogenic potentials in children affected by myelomeningocele.

PURPOSE: The aim of the present study is to establish if the vestibular evoked myogenic potentials (VEMPs) could be used as a clinical test for the evaluation of vestibular function in children affected by myelomeningocele (MMC). MATERIALS AND METHODS: Fifteen children, aged between 3 and 17 years, who had been affected by MMC were investigated. Data obtained from these children were compared with normal data from healthy children of the same age. Electromyographic activity of sternocleidomastoid muscle was recorded, while children were laid supine and asked to raise their head off the bed in order to activate their neck flexors bilaterally. The saccular receptors were acoustically stimulated with a logon of 500 Hz at an intensity of 130 dB peSPL presented monaurally through earphones. In each recording, we analyzed latencies and amplitudes of the p13-and n23 waves and the amplitude ratio between the two ears. RESULTS: VEMPs were detected to be normal in 13 patients. In particular, the mean p13 and mean n23 latencies were 15.7 (±1.4) and 21.7 (±1.1) ms, respectively; the mean amplitude value was 84.7 (±36.6), while the mean amplitude ratio was 17.4 (±12). A comparison of latencies and amplitude ratios between the children and healthy control group did not reveal any significant difference. On the contrary, a comparison of amplitude values between the two groups showed significant differences. CONCLUSION: In conclusion, vestibulocollic reflex is normal in patients affected by MMC, and VEMPs could represent a valid and noninvasive technique eligible to investigate the vestibular functions in these children.

Improving the Photocatalytic Activity of Mesoporous Titania Films through the Formation of WS2/TiO2 Nano-Heterostructures.

Heterostructures formed by anatase nanotitania and bidimensional semiconducting materials are expected to become the next-generation photocatalytic materials with an extended operating range and higher performances. The capability of fabricating optically transparent photocatalytic thin films is also a highly demanded technological issue, and increasing the performances of such devices would significantly impact several applications, from self-cleaning surfaces to photovoltaic systems. To improve the performances of such devices, WS2/TiO2 heterostructures obtained by incorporating two-dimensional transition metal dichalcogenides layers into titania mesoporous ordered thin films have been fabricated. The self-assembly process has been carefully controlled to avoid disruption of the order during film fabrication. WS2 nanosheets of different sizes have been exfoliated by sonication and incorporated in the mesoporous films via one-pot processing. The WS2 nanosheets result as well-dispersed within the titania anatase mesoporous film that retains a mesoporous ordered structure. An enhanced photocatalytic response due to an interparticle electron transfer effect has been observed. The structural characterization of the heterostructure has revealed a tight interplay between the matrix and nanosheets rather than a simple additive co-catalyst effect.

Bidimensional Engineered Amorphous a-SnO2 Interfaces: Synthesis and Gas Sensing Response to H2S and Humidity.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) and metal chalcogenides (MCs), despite their excellent gas sensing properties, are subjected to spontaneous oxidation in ambient air, negatively affecting the sensor's signal reproducibility in the long run. Taking advantage of spontaneous oxidation, we synthesized fully amorphous a-SnO2 2D flakes (≈30 nm thick) by annealing in air 2D SnSe2 for two weeks at temperatures below the crystallization temperature of SnO2 (T < 280 °C). These engineered a-SnO2 interfaces, preserving all the precursor's 2D surface-to-volume features, are stable in dry/wet air up to 250 °C, with excellent baseline and sensor's signal reproducibility to H2S (400 ppb to 1.5 ppm) and humidity (10-80% relative humidity (RH)) at 100 °C for one year. Specifically, by combined density functional theory and ab initio molecular dynamics, we demonstrated that H2S and H2O compete by dissociative chemisorption over the same a-SnO2 adsorption sites, disclosing the humidity cross-response to H2S sensing. Tests confirmed that humidity decreases the baseline resistance, hampers the H2S sensor's signal (i.e., relative response (RR) = Ra/Rg), and increases the limit of detection (LOD). At 1 ppm, the H2S sensor's signal decreases from an RR of 2.4 ± 0.1 at 0% RH to 1.9 ± 0.1 at 80% RH, while the LOD increases from 210 to 380 ppb. Utilizing a suitable thermal treatment, here, we report an amorphization procedure that can be easily extended to a large variety of TMDs and MCs, opening extraordinary applications for 2D layered amorphous metal oxide gas sensors.

[Asthma induced by chloramine T in nurses: case report]. / Asma da cloramina T nel personale sanitario: descrizione di un caso.

BACKGROUND: Chloramine T is used in hospitals as a disinfectant and for sterilization of endoscopy instruments. OBJECTIVES: A case of a nurse suffering from asthma due to Chloramine T is presented in order to focus attention on this occupational disease. METHODS AND RESULTS: The patient (male, 43 years) had been a nurse since 1993, working in various departments and operating rooms where he was exposed to glutaraldehyde and Chloramine T to disinfect surgical and endoscopy instruments. In 2007 he noticed the beginning of asthmatic reactions after exposure to the disinfectant. Skin tests with common allergens gave positive reactions and a skin test with Chloramine T gave a positive result. An inhalation test with glutaraldehyde gave negative results for both asthma and rhinitis. During the inhalation test with Chloramine T 0.5%, a significant biphasic decrease in FEVI was observed. The score of subjective symptoms for rhinitis was negative, CONCLUSIONS: The case confirms the current difficulty in diagnosing occupational asthma due to Chloramine T in health care workers, which is due to the frequent presence of late reactions and to exposure to several respiratory allergens and irritants in the workplace. The specific inhalation challenge is thus confirmed as the gold standard for the diagnosis of asthma induced by Chloramine T and in occupational asthma in general. It may very well be that the frequency of occupational asthma due to sensitization to Chloramine T in nurses is underestimated.

Self-Assembled SnO2/SnSe2 Heterostructures: A Suitable Platform for Ultrasensitive NO2 and H2 Sensing.

By means of experiments and theory, the gas-sensing properties of tin diselenide (SnSe2) were elucidated. We discover that, while the stoichiometric single crystal is chemically inert even in air, the nonstoichiometric sample assumes a subnanometric SnO2 surface oxide layer once exposed to ambient atmosphere. The presence of Se vacancies induces the formation of a metastable SeO2-like layer, which is finally transformed into a SnO2 skin. Remarkably, the self-assembled SnO2/SnSe2-x heterostructure is particularly efficient in gas sensing, whereas the stoichiometric SnSe2 sample does not show sensing properties. Congruently with the theoretical model, direct sensing tests carried out on SnO2/SnSe2-x at an operational temperature of 150 °C provided sensitivities of (1.06 ± 0.03) and (0.43 ± 0.02) [ppm]-1 for NO2 and H2, respectively, in dry air. The corresponding calculated limits of detection are (0.36 ± 0.01) and (3.6 ± 0.1) ppm for NO2 and H2, respectively. No detectable changes in gas-sensing performances are observed in a time period extended above six months. Our results pave the way for a novel generation of ambient-stable gas sensor based on self-assembled heterostructures formed taking advantage on the natural interaction of substoichiometric van der Waals semiconductors with air.

Sustainable Liquid-Phase Exfoliation of Layered Materials with Nontoxic Polarclean Solvent.

Liquid-phase exfoliation is the most suitable platform for large-scale production of two-dimensional materials. One of the main open challenges is related to the quest of green and bioderived solvents to replace state-of-the-art dispersion media, which suffer several toxicity issues. Here, we demonstrate the suitability of methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (Rhodiasolv Polarclean) for sonication-assisted liquid-phase exfoliation of layered materials for the case-study examples of WS2, MoS2, and graphene. We performed a direct comparison, in the same processing conditions, with liquid-phase exfoliation using N-methyl-2-pyrrolidone (NMP) solvent. The amount of few-layer flakes (with thickness <5 nm) obtained with Polarclean is increased by ∼350% with respect to the case of liquid-phase exfoliation using NMP, maintaining comparable values of the average lateral size, which even reaches ∼10 µm for the case of graphene produced by exfoliation in Polarclean, and of the yield (∼40%). Correspondingly, the density of defects is reduced by 1 order of magnitude by Polarclean-assisted exfoliation, as evidenced by the I(D)/I(G) ratio in Raman spectra of graphene as low as 0.07 ± 0.01. Considering the various advantages of Polarclean over state-of-the-art solvents, including the absence of toxicity and its biodegradability, the validation of superior performances of Polarclean in liquid-phase exfoliation paves the way for sustainable large-scale production of nanosheets of layered materials and for extending their use in application fields to date inhibited by toxicity of solvents (e.g., agri-food industry and desalination), with a subsequent superb impact on the commercial potential of their technological applications.

Charge Redistribution Mechanisms in SnSe2 Surfaces Exposed to Oxidative and Humid Environments and Their Related Influence on Chemical Sensing.

Tin diselenide (SnSe2) is a van der Waals semiconductor, which spontaneously forms a subnanometric SnO2 skin once exposed to air. Here, by means of surface-science spectroscopies and density functional theory, we have investigated the charge redistribution at the SnO2-SnSe2 heterojunction in both oxidative and humid environments. Explicitly, we find that the work function of the pristine SnSe2 surface increases by 0.23 and 0.40 eV upon exposure to O2 and air, respectively, with a charge transfer reaching 0.56 e-/SnO2 between the underlying SnSe2 and the SnO2 skin. Remarkably, both pristine SnSe2 and defective SnSe2 display chemical inertness toward water, in contrast to other metal chalcogenides. Conversely, the SnO2-SnSe2 interface formed upon surface oxidation is highly reactive toward water, with subsequent implications for SnSe2-based devices working in ambient humidity, including chemical sensors. Our findings also imply that recent reports on humidity sensing with SnSe2 should be reinterpreted, considering the pivotal role of the oxide skin in the interaction with water molecules.

Two-Step Exfoliation of WS2 for NO2, H2 and Humidity Sensing Applications.

WS2 exfoliated by a combined ball milling and sonication technique to produce few-layer WS2 is characterized and assembled as chemo-resistive NO2, H2 and humidity sensors. Microstructural analyses reveal flakes with average dimensions of 110 nm, "aspect ratio" of lateral dimension to the thickness of 27. Due to spontaneous oxidation of exfoliated WS2 to amorphous WO3, films have been pre-annealed at 180 °C to stabilize WO3 content at ≈58%, as determined by X-ray Photoelectron Spectroscopy (XPS), Raman and grazing incidence X-ray Diffraction (XRD) techniques. Microstructural analysis repeated after one-year conditioning highlighted that amorphous WO3 concentration is stable, attesting the validity of the pre-annealing procedure. WS2 films were NO2, H2 and humidity tested at 150 °C operating Temperature (OT), exhibiting experimental detection limits of 200 ppb and 5 ppm to NO2 and H2 in dry air, respectively. Long-term stability of the electrical response recorded over one year of sustained conditions at 150 °C OT and different gases demonstrated good reproducibility of the electrical signal. The role played by WO3 and WS2 upon gas response has been addressed and a likely reaction gas-mechanism presented. Controlling the microstructure and surface oxidation of exfoliated Transition Metal Dichalcogenides (TMDs) represents a stepping-stone to assess the reproducibility and long-term response of TMDs monolayers in gas sensing applications.

Asbestos exposure biomarkers in the follow-up of asbestos-exposed workers.

Health surveillance of asbestos exposed workers should be stratified according to the exposure level. Unfortunately there is a lack of information regarding asbestos exposure in many working places and markers of asbestos exposure are often needed. The aim of the study was to assess the reliability of different dose and effect biomarkers in the follow up of asbestos-exposed workers. Mineralogical analysis of bronchoalveolar lavage fluid (BALF) as a biomarker of asbestos fibre burden was performed in a population of 307 male subjects occupationally exposed to asbestos. Using nonparametric statistical methods 8 variables were analyzed with respect to asbestos-related diseases and working sectors. The existence of a relationship between serum soluble mesothelin-related peptides (SMRP) and asbestos exposure levels was also investigated. Concentrations of amphiboles, chrysotile and asbestos bodies in BALF were higher in patients with asbestosis as well as in railway industry workers. A correlation between the onset of non malignant asbestos-related diseases and the levels of SMRP concentration was not found. This study confirms that fibre concentration in BALF may be considered as a reliable biomarker of previous asbestos exposure, whereas SMRP does not appear to be influenced by asbestos exposure levels.