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The convolution of two physical entities, denoted as f and g, delineates the manner in which one entity undergoes modification in response to the other. This transformative process is mathematically represented by the expression f ⨂ g, symbolizing the convolution of the two entities in a resultant function h. Frequently, it becomes imperative to comprehend the magnitude of the induced modifications. From the derived function h, a crucial step involves the separation of the two original signals, a process commonly referred to as deconvolution. Various techniques have been proposed to facilitate the calculation of the deconvolution, with one notable approach originating in 1931 by van Cittert. The algorithm, based on an iterative method, has been scrutinized over time, notably by Bracewell and, more recently, by Jansson. This work represents the current state-of-the-art, focusing specifically on the analysis of Auger spectra obtained through XPS. Emphasis is placed on delineating the procedural aspects of the analysis, and the algorithm utilized in the open-source software RxpsG is comprehensively described. [ABSTRACT FROM AUTHOR]

Recently, the scientific community experienced two revolutionary events. The first was the synthesis of single-layer graphene, which boosted research in many different areas. The second was the advent of quantum technologies with the promise to become pervasive in several aspects of everyday life. In this respect, diamonds and nanodiamonds are among the most promising materials to develop quantum devices. Graphene and nanodiamonds can be coupled with other carbon nanostructures to enhance specific properties or be properly functionalized to tune their quantum response. This contribution briefly explores photoelectron spectroscopies and, in particular, X-ray photoelectron spectroscopy (XPS) and then turns to the present applications of this technique for characterizing carbon nanomaterials. XPS is a qualitative and quantitative chemical analysis technique. It is surface-sensitive due to its limited sampling depth, which confines the analysis only to the outer few top-layers of the material surface. This enables researchers to understand the surface composition of the sample and how the chemistry influences its interaction with the environment. Although the chemical analysis remains the main information provided by XPS, modern instruments couple this information with spatial resolution and mapping or with the possibility to analyze the material in operando conditions at nearly atmospheric pressures. Examples of the application of photoelectron spectroscopies to the characterization of carbon nanostructures will be reviewed to present the potentialities of these techniques. [ABSTRACT FROM AUTHOR]

Advanced materials could bring about fundamental improvements in the evolution of innovative analytical devices, i.e., biosensors or lab-on-a-chip devices, in particular in the context of liquid biopsies. Here, plasma deposition processes were tested for the introduction of primary amines on silicon surfaces by tuning the amounts and availability of amino-charged residues. Different binary (CH4/NH3) and ternary (CH4/NH3/H2 and CH4/NH3/N2) mixtures of gases were used as feeds for the plasma treatments. The obtained surfaces were fully characterized for their chemical and physical properties before their use as capture materials in a functional test. Synthetic and fluorescently conjugated microRNA-21 (miR-21) was selected as the target molecule. The capture of miR-21 increased linearly with the increase in amino nitrogen measured on surfaces. The surface showing the most promising performance was further analyzed in different conditions, i.e., varying pH and time of incubation, incubation with different microRNAs, and possible elution of captured microRNAs. The apparent pH range of primary amines present on the surfaces was around 3.5–4. Positively charged surfaces prepared via PE-CVD were, therefore, demonstrated as being suitable materials for the capture of microRNA biomarkers, paving the way for their inclusion in biomedical devices for the purification and analysis of circulating biomarkers. [ABSTRACT FROM AUTHOR]

The effect of the electrolyte composition and the deposition potential range on the physical properties and possible corrosion protection effect of polypyrrole coatings on rheocast aluminum–2.5 % silicon alloy is investigated. Solutions with different concentrations of sodium nitrate and an electron transfer mediator reagent were used for the electrodeposition. Polypyrrole coating is able to hinder the entrance of electrolyte. Upon the penetration of chloride ions, the coating can induce passivation of the alloy's surface by its reduction. The thickness of the coating and its ion‐barrier properties, controlled by the electrodeposition conditions, are shown as the important factors influencing the protection efficiency. However, localized drastic galvanic coupling at the polypyrrole/aluminum interface forms blisters, causes failure, and limits the possible protection. [ABSTRACT FROM AUTHOR]

Recently, plasma deposited amorphous carbon films have been the subject of extensive experimental and theoretical investigations aimed at correlating their electronic, structural, and mechanical properties to growth parameters. To investigate these properties, different spectral parameters reflecting the electronic structure of carbon-based materials are proposed in literature. The effects of various electronic configurations on the carbon photoelectron spectra are analyzed here with particular attention to C1s core line with the aim to better interpret its structure. The latter is commonly fitted under the assumption that it can be described by using just two spectral components related to sp2 and sp3 hybrids. Their relative intensities are then used to estimate the sp2 and sp3 phases. We show that, in the presence of an amorphous network, the C1s line shape is the result of a more complex mixture of electronic states. Ar+ irradiated graphite and successive oxidation was used to identify spectral features to better describe the C1s line shape. [ABSTRACT FROM AUTHOR]

Little has been published so far on the fabrication of porous ceramic films by using the Breath Figure method. In this work we explored the Breath Figure method to obtain ceramics with patterned surfaces. A UV cross-linkable polysiloxane was used to produce Breath Figures with tunable pore size. Pores formation, in terms of size and distribution on the polysiloxane films, were studied as a function of the concentration of the starting solution and time before UV irradiation. The polymeric breath figures were then pyrolyzed in controlled atmosphere to obtain, through the polymer-derived ceramic, PDCs, route the corresponding ceramic preserving the original porous surface. Pyrolysis under different gases, in particular air, nitrogen and ammonia, allows obtaining films of three different ceramic materials: silicon dioxide, SiO 2 , silicon oxycarbide, SiOC and silicon oxynitride, SiON respectively. [ABSTRACT FROM AUTHOR]

Osteo-integration and tissue regeneration are vital for the longevity, durability, and unremitting functionality of medical implants/scaffolds implanted in vivo . It's essential for biomaterials used for in vivo implantation to induce the cellular secretion of growth factors, necessary for the desired tissue generation, since the administration of artificial growth factors, in vivo , is largely prohibited. Plasma functionalized (N 2 and O 2 ) and stabilized Graphene Oxide (GO) thin layers in a hybrid with amorphous carbon (aC) induced the expression of vascular endothelial growth factor (VEGF) and osteoprotegerin (OPG) growth factors in fibroblasts (hGF) and, more remarkably, in osteoblasts (hFOB) cells confirming the suitability for tissue regeneration and osteo-integration applications. We also observed a negative trend between hGF fibroblasts, but not hFOB osteoblasts, cellular viability and GO presence in the hybrid films that might indicate the phenomenon of oxidative stress. We traced that back to the presence of higher concentrations of carboxyl and the carbonyl groups on the surface of the GO rich coatings. The above described properties provided by GO coatings might be desirable for bio-selectivity applications and for the reduction of the undesired fibrosis process that is associated with medical implants in vivo environment. Moreover, novel plasma functionalized GO/polymer hybrid thin coating hybrid compositions are promising candidates for tissue engineering and bioengineering applications as excellent antimicrobial and anticancer platforms. [ABSTRACT FROM AUTHOR]

Abstract: Polymeric membranes used in bioreactors for bioartificial livers are generally chosen for their transport and separation properties to provide liver cells with adequate nutrients supply and avoid rejection. Possible effects of membrane surface properties on cell metabolism are generally given little consideration. The reported effects of membrane surface wettability on adherent liver cells are qualitative and inconsistent, possibly due to the variation of other surface properties and the culture in Petri dishes, often at confluence, under uncontrolled time- and space-varying metabolite concentrations. In this investigation, rat liver cells were cultured in sub-confluent adhesion on model membranes hydrophilized by physical treatment featuring varying surface wettability in a continuous-flow recycle bioreactor. Bioreactor optimization permitted to culture cells at uniform and measurable pericellular concentrations of metabolic substrates, and to challenge them with controlled increasing ammonia concentrations. Membrane surface wettability was characterized in terms of water sorption, dynamic contact angle, and oxygen content by XPS. The kinetics of oxygen consumption, ammonia elimination and urea synthesis of cells adherent on membranes with increasing wettability was characterized at increasing ammonia concentrations. Cells exhibited increasingly better metabolic functions on membranes with increasing surface wettability. Metabolic reaction rate differences were increasingly more evident at increasing ammonia concentrations. Membrane surface wettability appeared to mainly affect cell capacity to respond to the ammonia challenge. [Copyright &y& Elsevier]

Atoms characterized by nonequivalent electronegativities form chemical bonds by exchanging electrical charge. The fraction of charge exchanged is dictated by the electronegativity differences among the system atoms. In the electronegativity equalization method, the charge distribution is estimated by forcing the system to relax to a common chemical potential, which corresponds to its configuration of energy minimum. By definition, this method cannot be applied to homonuclear bonds. A model is proposed to estimate the charge shared in molecular orbitals of homonuclear molecules. The model expands upon the electronegativity equalization method by adding formalism to describe the spin coupling characteristic of homonuclear bonds. Results are in excellent agreement with other quantum mechanical estimations of the charge distributions. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Recent advances in nanomaterial design and synthesis has resulted in robust sensing systems that display superior analytical performance. The use of nanomaterials within sensors has accelerated new routes and opportunities for the detection of analytes or target molecules. Among others, carbon-based sensors have reported biocompatibility, better sensitivity, better selectivity and lower limits of detection to reveal a wide range of organic and inorganic molecules. Carbon nanomaterials are among the most extensively studied materials because of their unique properties spanning from the high specific surface area, high carrier mobility, high electrical conductivity, flexibility, and optical transparency fostering their use in sensing applications. In this paper, a comprehensive review has been made to cover recent developments in the field of carbon-based nanomaterials for sensing applications. The review describes nanomaterials like fullerenes, carbon onions, carbon quantum dots, nanodiamonds, carbon nanotubes, and graphene. Synthesis of these nanostructures has been discussed along with their functionalization methods. The recent application of all these nanomaterials in sensing applications has been highlighted for the principal applicative field and the future prospects and possibilities have been outlined. [ABSTRACT FROM AUTHOR]

Recent advances in technology are expected to increase our current understanding of neuroscience. Nanotechnology and nanomaterials can alter and control neural functionality in both in vitro and in vivo experimental setups. The intersection between neuroscience and nanoscience may generate long-term neural interfaces adapted at the molecular level. Owing to their intrinsic physicochemical characteristics, gold nanostructures (GNSs) have received much attention in neuroscience, especially for combined diagnostic and therapeutic (theragnostic) purposes. GNSs have been successfully employed to stimulate and monitor neurophysiological signals. Hence, GNSs could provide a promising solution for the regeneration and recovery of neural tissue, novel neuroprotective strategies, and integrated implantable materials. This review covers the broad range of neurological applications of GNS-based materials to improve clinical diagnosis and therapy. Sub-topics include neurotoxicity, targeted delivery of therapeutics to the central nervous system (CNS), neurochemical sensing, neuromodulation, neuroimaging, neurotherapy, tissue engineering, and neural regeneration. It focuses on core concepts of GNSs in neurology, to circumvent the limitations and significant obstacles of innovative approaches in neurobiology and neurochemistry, including theragnostics. We will discuss recent advances in the use of GNSs to overcome current bottlenecks and tackle technical and conceptual challenges. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) decorated CNTs are promising materials for photocatalytics and biosensors. However, the synthesis of AuNPs chemically linked to the walls of MWCNTs is challenging and toxic products such as thionylchloride (SOCl2) or [1-ethyl-3(dimethyl-amino) propyl] carbodiimide hydrochloride (EDAC) need to be used. This work reports a new approach to prepare gold nanoparticles decorated multiwalled carbon nanotubes (MWCNTs) by using cysteaminium chloride via the formation of a Zwitterionic acide-base bond. The grafting process consists of 3 mains steps: oxidation, thiolation and decoration of AuNPs on the surface of MWCNTs. The completion of each step has been verified out by both spectroscopic (Raman, UV-Vis, FT-IR) and Scanning Electron Miscroscopy (SEM). The chemical bonding states of synthesized products have been proven by X-ray photoelectron spectroscopy (XPS). [ABSTRACT FROM AUTHOR]

In this paper, we discuss the progression of flash sintering in 10mol% gadolinium-doped ceria specimens. Flash transition is correlated with the generation of n-type electronic conductivity in air under direct-current bias. Its origin is attributed to partial reduction of the material which propagates from the cathodic-to-anodic region. The phenomenon was observed, in-situ , by monitoring the development of electrochemical blackening during the incubation period of the flash-experiment. Anomalous features, including shift in the valence band edge, shrinkage of the band-gap and change in the oxidation state of Ce in flashed samples was confirmed by X-ray photoelectron spectroscopy and diffuse reflectance measurements. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Herein, we explored the possibility to develop hybrid graphene oxide/amorphous carbon (GO/a-C) coatings with different oxidation degree and analysed the influence of surface oxygen composition on biocompatibility. GO/a-C films were obtained by plasma treatment of GO-coated PEEK substrates using different relative amounts of methane and oxygen as gaseous precursors. The chemical surface composition of the coatings, including oxygen abundance and nature of the oxygen-containing groups, was analysed by X-ray photoelectron spectroscopy, and cell response to the sample materials was assessed by viability and cytotoxicity assays on two different cell types, including human osteoblasts (hFOB) and human gingiva fibroblasts (hGF). The cells presented partially decreased viability on plasma-treated samples respect to the untreated PEEK substrate, but no significant evidence of cell toxicity was shown, with LDH release largely below 20% for all the materials. A distinct cell-specific cytotoxicity response was observed. No significant effects were registered on hGF cells, suggesting that hGF cells were not sensitive to the different oxygen surface content of the coatings. On the other side, hFOB showed relatively higher toxicity when cultured on the samples with high surface oxygen concentration. Human osteoblasts cell toxicity increased considerably with increasing content of carbonyl and carboxyl groups on the surface, suggesting that these functional groups had an important role in inducing oxidative stress in hFOB cells. • Hybrid graphene oxide/amorphous carbon (GO/a-C) films were deposited on PEEK substrates. • Surface oxygen content was modulated using different plasma treatments. • The amount of oxygen-containing functional groups was significantly increased using O2 as precursor gas in the plasma treatment. • Cell viability and toxicity on the sample surfaces was analysed as a function of surface chemical composition. • We identified the mechanism leading to increased osteoblast cell toxicity in the coatings with high O/C and O-C=O surface abundance. [ABSTRACT FROM AUTHOR]

Cerium-based conversion coatings were deposited on Rheo-High Pressure Die Cast (HPDC) Al-Si alloys by immersion in cerium nitrate aqueous solutions. Rheocast Al-Si alloys have a heterogeneous microstructure and present a challenge for the conversion treatment. Different parameters were studied to optimize the conversion coating, and NaCl or H 2 O 2 were also added to the solution to modify or accelerate the deposition process. The mechanism of the coating formation was studied by means of focused ion beam milling (FIB) assisted SEM. The results show that applying cerium-based conversion coating to Al-Si alloys, is possible and a preferential deposition is obtained due to the presence of iron-rich intermetallic particles inside the eutectic region. The formation mechanism of selectively deposited cerium-based conversion coating includes dissolution of aluminium matrix, selective dissolution of aluminium from the noble intermetallic particles, oxidation of iron from the intermetallic particles, and the deposition of cerium hydroxide/oxide layer. The results reveal that the improvement in corrosion resistance in the presence of selectively deposited cerium-based conversion coating is more significant compared to the homogenous coating deposited from the conversion solution containing H 2 O 2 . [ABSTRACT FROM AUTHOR]

Silicon plays an important role in bone formation and maintenance, improving osteoblast cell function and inducing mineralization. Often, bone deformation and long bone abnormalities have been associated with silica/silicon deficiency. Diatomite, a natural deposit of diatom skeleton, is a cheap and abundant source of biogenic silica. The aim of the present study is to validate the potential of diatom particles derived from diatom skeletons as silicon-donor materials for bone tissue engineering applications. Raw diatomite (RD) and calcined diatomite (CD) powders were purified by acid treatments, and diatom microparticles (MPs) and nanoparticles (NPs) were produced by fragmentation of purified diatoms under alkaline conditions. The influence of processing on the surface chemical composition of purified diatomites was evaluated by X-ray photoelectron spectroscopy (XPS). Diatoms NPs were also characterized in terms of morphology and size distribution by transmission electron microscopy (TEM) and Dynamic light scattering (DLS), while diatom MPs morphology was analyzed by scanning electron microscopy (SEM). Surface area and microporosity of the diatom particles were evaluated by nitrogen physisorption methods. Release of silicon ions from diatom-derived particles was demonstrated using inductively coupled plasma optical emission spectrometry (ICP/OES); furthermore, silicon release kinetic was found to be influenced by diatomite purification method and particle size. Diatom-derived microparticles (MPs) and nanoparticles (NPs) showed limited or no cytotoxic effect in vitro depending on the administration conditions. [ABSTRACT FROM AUTHOR]

Hybrid core–shell nanodiamond-gold nanoparticles were synthesized and characterized as a novel multifunctional material with tunable and tailored properties for multifunctional biomedical applications. The combination of nanostructured gold and nanodiamond properties afford new options for optical labeling, imaging, sensing, and drug delivery, as well as targeted treatment. ND@Au core–shell nanoparticles composed of nanodiamond (ND) core doped with Si vacancies (SiV) and Au shell were synthesized and characterized in terms of their biomedical applications. Several bioimaging modalities based on the combination of optical and spectroscopic properties of the hybrid nano-systems are demonstrated in cellular and developing zebrafish larvae models. The ND@Au nanoparticles exhibit isolated ND's Raman signal of sp3 bonded carbon, one-photon fluorescence of SiV with strong zero-phonon line at 740 nm, two-photon excited fluorescence of nanogold with short fluorescence lifetime and strong absorption of X-ray irradiation render them possible imaging agent for Raman mapping, Fluorescence imaging, two-photon Fluorescence Lifetime Imaging (TP-FLIM) and high-resolution hard-X-ray microscopy in biosystems. Potential combination of the imaging facilities with other theranostic functionalities is discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Si 3 N 4 aerogel can be easily synthesized from preceramic precursors with no catalyst. • Infiltration of phase change material is spontaneous and immediate. • Thermal performances can be optimized tailoring shape-stabilizer pore distribution. • Si 3 N 4 aerogel withstand oxidation over 1000 °C in air. This work presents a new skeleton material for thermal energy storage (TES), a silicon nitride aerogel obtained through the pyrolysis of a pre-ceramic polymer. Silicon nitride offers a good combination of thermal conductivity, high-temperature resistance, and chemical inertness. The aerogel porosity can be spontaneously infiltrated with molten NaNO 3 , which is a typical phase change material (PCM) in high-temperature TES. The Si 3 N 4 /NaNO 3 composite exhibits excellent thermal properties with a thermal energy storage efficiency of 82 %, a limited molten salt leakage, and good stability to thermal cycling. The aerogel withstands oxidation up to high temperature and is chemically inert even in contact with salts. This novel aerogel shows also a notable paraffin absorption ability (used in room temperature TES) with negligible leakage even when in contact with absorbent paper. The so-obtained composite reached ≈ 82.4 vol % of organic PCM and a thermal energy storage efficiency of ≈ 62 % compared to neat paraffin. [ABSTRACT FROM AUTHOR]

The low quality of adhesion performance on polymeric surfaces has forced the development of specific pretreatments able to toughen the interface between substrate and adhesive. Among these methods, atmospheric pressure plasma treatment (APPT) appears particularly suitable for its environmental compatibility and its effectiveness in altering the chemical state of the surface. In this work, an experimental study on adhesively bonded joints realized using polyamide as substrates and polyurethane as the structural adhesive was carried out with the intent to characterize their fatigue behavior, which represents a key issue of such joints during their working life. The single lap joint (SLJ) geometry was chosen and several surface pretreatments were compared with each other: degreasing, abrasion (alone and followed by APPT) and finally APPT. The results show that the abrasion combined with APPT presents the most promising behavior, which appears consistent with the higher percentage of life spent for crack propagation found by means of DIC on this class of joints with respect to the others. APPT alone confers a good fatigue resistance with respect to the simple abrasion, especially at a low number of cycles to failure. [ABSTRACT FROM AUTHOR]

Ceramic aerogels possess intriguing thermophysical properties which make them excellent candidates for high temperature thermal insulators. However, their properties can degrade at high temperature because of crystallization phenomena or because of densification (causing a sensible reduction of their specific surface area and porosity). The polymer derived ceramic (PDC) route is a relatively new way of developing ceramic aerogels. Several aspects influence the properties of the final product when dealing with preceramic polymers, among them their chemical composition and molecular architecture. In this work, we investigated the possibility of producing aerogels belonging to the SiCN system from polysilazanes mixtures, namely perhydropolysilazane (PHPS) and a methyl/vinyl-containing polysilazane, namely Durazane 1800®, thus changing the C/Si ratio of the amorphous pyrolyzed products. It is shown that the chemical composition of the ceramic aerogel affects the main properties of the porous materials, such as thermal stability and specific surface area (SSA). Results show that the presence of carbon in the aerogels inhibits crystallization of Si 3 N 4 up to 1600 °C in N 2 and allows to maintain a SSA of ~90 m2/g up to this temperature. [ABSTRACT FROM AUTHOR]

Clinically, there is an urgent need to identify new therapeutic strategies for selectively treating cancer cells. One of the directions in this research is the development of biocompatible therapeutics that selectively target cancer cells. Here, we show that novel aminated graphene oxide (haGO-NH2) nanoparticles demonstrate increased toxicity towards human hepatocellular cancer cells compared to pristine graphene oxide(GO). The applied novel strategy for amination leads to a decrease in the size of haGO-NH2 and their zeta potential, thus, assuring easier penetration through the cell membrane. After characterization of the biological activities of pristine and aminated GO, we have demonstrated strong cytotoxicity of haGO-NH2 toward hepatic cancer cells—HepG2 cell line, in a dose-dependent manner. We have presented evidence that the cytotoxic effects of haGO-NH2 on hepatic cancer cells were due to cell membrane damage, mitochondrial dysfunction and increased reactive oxygen species (ROS) production. Intrinsically, our current study provides new rationale for exploiting aminated graphene oxide as an anticancer therapeutic. [ABSTRACT FROM AUTHOR]

The feasibility of flash joining conductive ceramics using spark plasma sintering is demonstrated. It is shown that graphite disks can be joined in a few seconds (6–10 s electric discharge time) using a SiOC precursor (methyl silicone resin) as an interlayer. Differently from usual flash experiments, the process does not require any pre-heating, allowing a dramatic reduction of the processing time. XPS analysis of the joint revealed a clear evolution of the chemical environment of silicon with a progressive transition from SiOC to SiO 2 /SiC. Mechanical tests were performed to determine the fracture toughness (1.0 ± 0.2 MPa m0.5) and fracture energy (40.6 ± 9.8 J/m2) of the interface Flash joining can be applied beyond graphite joining, and opens a novel and flexible processing route for many conductive ceramics, as demonstrate by preliminary work on Kanthal® Super MoSi 2 and C f -reinforced SiC. [ABSTRACT FROM AUTHOR]

Antibacterial surfaces are crucial to hinder the spread of pathogens infections, especially when high-touch surfaces (HTS) are involved, as in the case of food packaging. Nature can be inspiring, offering plenty of nanotextured surfaces with high antibacterial activity. Herein, poly(butylene succinate) (PBS), one of the most reliable biodegradable plastic used in food packaging, was nanotextured by a low pressure plasma oxygen etching. Moreover, the deposition of SiO X coatings ≈15 nm thick by plasma enhanced chemical vapor deposition (PECVD) was carried out to improve gas barrier properties of the nanotextured polymers. Based on experimental findings, a hypothesis for the nanotexturing mechanism in our plasma experimental set-up has been figured out. The antibacterial properties were tested against E. coli and S. aureus , showing in both cases a strong inhibitory effect by a factor of >4 log 10 CFU cm−2. Finally, the oxygen diffusion permeability coefficients (P O2) were also measured, and the oxygen transmission rates (OTR) were calculated as an indicator of the gas barrier performance of the samples. As expected, plasma etching impacted negatively on the oxygen permeability. However, by coating with SiO x , the treated PBS showed a 30 % decrease of the OTR compared even to the untreated PBS. [Display omitted] • Low pressure plasma oxygen etching was employed to nanotexture poly(butylene succinate) (PBS). • Surface nanotexturing is achieved without relying on the contamination by metallic impurities. • The PBS semicrystalline structure is the reason for the surface nanotexturing • Nanotextured PBS SiOx shows high antibacterial activity combined to a decreased OTR. [ABSTRACT FROM AUTHOR]

As being only one atom thick, most of the device applications require graphene to be partially or fully supported by a substrate, which is typically silicon dioxide (SiO 2). According to a common understanding, graphene interacts with SiO 2 through weak, long-range van der Waals forces, emerging between instantaneous/induced dipoles, in contrast to the experimental evidence that reveals a surprisingly high interaction between graphene and SiO 2. In order to get further insight into this phenomenon, we carried out diverse physical measurements on SiO 2 substrates, prepared via different fabrication protocols, with and without graphene on top. As a result, the role of the oxide surface charges is recognized for the first time as a main factor causing graphene to strongly interact with SiO 2. Our findings provide guidelines for designing 2D materials interaction with a substrate through modulation of surface charges. This, in turn, can facilitate the development of new graphene based microelectronic devices. Image 1 [ABSTRACT FROM AUTHOR]

Abstract Nickel oxide is a cheap and efficient water oxidation catalyst (WOC). However, its application as anodic co-catalyst in photoelectrochemical cells (PECs) is limited by poor optical properties: it becomes black at positive biasing. Here a pulsed laser deposition (PLD) method is used to produce amorphous nickel oxide thin films with optical and catalytic properties tailored for PECs. The procedure, based on the laser ablation of pure nickel in oxygen at relatively high pressure, allows obtaining a porous or compact layer by simply varying the substrate temperature. The film transmittance is higher than 90% in the visible range for a porous coating. The improved optical properties can solve the issue of parasitic light absorption when Ni oxides are used to functionalize photoanodes. A thin, porous coating of Ni oxides operated as a WOC also shows electrode metrics on-par with the best results in literature, with an overpotential of 355 mV at 1 mA cm−2 and a 62 mV/decade Tafel slope. These results thus open the way for the use of Ni oxides as WOC for photoanodes. An in-depth study of the interplay between the morphological, optical and catalytic features of Ni oxides highlights the versatility of PLD in tuning materials properties. [ABSTRACT FROM AUTHOR]

Coatings of graphene oxide over two substrates of glass-fibre and polystyrene were obtained by electrophoretic deposition (EPD). A chemical reduction of graphene oxide by exposure to hydrazine hydrate at 100 °C significantly changes the interfacial interaction with the substrate as well as the tribology. Spectroscopic techniques like Fourier transform infrared, Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction showed that the treatment with hydrazine replaces oxygen functional groups and also induces roughness, a structural disorder and decreases the interlayer separation in the transition from graphene oxide (GO) to reduced graphene oxide (rGO). Treatment with hydrazine reduces adhesion and friction force against diamond like carbon coated Si probe (DLC AFM) at the basal plain of the coatings. Investigation at the edges revealed that the presence of oxygenic functional groups leads to higher shear strength with glass-fibre and polystyrene which reduces after treatment with hydrazine. [ABSTRACT FROM AUTHOR]

The interaction of air bubbles with surfaces immersed in water is of fundamental importance in many fields of application ranging from energy to biology. However, many aspects of this topic such as the stability of surfaces in contact with bubbles remain unexplored. For this reason, in this work, we investigate the interaction of air bubbles with different kinds of dispersive surfaces immersed in water. The surfaces studied were polydimethylsiloxane (PDMS), graphite, and single layer graphene/PDMS composite. X-ray photoelectron spectroscopy (XPS) analysis allows determining the elemental surface composition, while Raman spectroscopy was used to assess the effectiveness of graphene monolayer transfer on PDMS. Atomic force microscopy (AFM) was used to study the surface modification of samples immersed in water. The surface wettability has been investigated by contact angle measurements, and the stability of the gas bubbles was determined by captive contact angle (CCA) measurements. CCA measurements show that the air bubble on graphite surface exhibits a stable behavior while, surprisingly, the volume of the air bubble on PDMS increases as a function of immersion time (bubble dynamic evolution). Indeed, the air bubble volume on the PDMS rises by increasing immersion time in water. The experimental results indicate that the dynamic evolution of air bubble in contact with PDMS is related to the rearrangement of surface polymer chains via the migration of the polar groups. On the contrary, when a graphene monolayer is present on PDMS, it acts as an absolute barrier suppressing the dynamic evolution of the bubble and preserving the optical transparency of PDMS. [ABSTRACT FROM AUTHOR]

Biologically compatible coatings that provide hermetic seal could resolve a major technological hurdle in the attempt to replace metals with polymers for biochips and active medical implants. The use of amorphous carbon/diamond like carbon (a-C:H) coatings to hermetically seal and biologically enhance polyether-ether-ketone (PEEK) for biomedical device integration in the human body was investigated. The PEEK coating functionality (sp3/sp2 ratio), hardness and thickness (70–200 nm) were controlled, by varying H 2 and N 2 concentration during the plasma operation with CH 4 . a-C:H coatings having the highest indentation modulus of 13.5 GPa, originate out of a CH 4 (90%) rich composition. Even in a mixture of 70/30 H 2 /CH 4 the hardness is 4.76 GPa, corresponding to hard and dense coatings. In all tested conditions of deposition coatings hardens was sufficient for the purpose of PEEK implants modification. The synthesized (a-C:H) nanoscale coatings were not water permeable as measured by the hydrolysis test, resolving the traditional challenge of swelling in wet environment. The hardness of the coatings showed strong correlations with the thickness, surprisingly however, with no correlations with the sp3/sp2 ratio. Selected non water permeable nanoscale coating on PEEK showed strong bioactivity by being viable for human osteoblast (hFOB) and human fibroblast (hGF) cells without toxicity issues. No correlation was observed between the coatings sp3/sp2 ratio and biological performance. [ABSTRACT FROM AUTHOR]

This work investigates the lithium doping effect on the structural and thermal behavior of (Mg 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2)O high entropy oxide (HEO) obtained by co-precipitation. The powders are characterized by differential thermal and thermogravimetric analyses (DTA-TG), mass spectroscopy, dilatometry, X-ray diffraction (XRD), magic angle spinning nuclear magnetic resonance (MAS NMR), Raman spectroscopy, X-ray photoelectron spectra (XPS) and electron spin resonance (ESR). The results point out that Co3+ ions (within a spinel phase) are reduced to Co2+ before the formation of the high entropy oxide in the absence of Li. Conversely, no reduction is observed in the case of Li-doping, thus indicating the presence of Co3+ within the high entropy rock salt lattice. At high temperature (>1050–1150 °C), the HEO phase loses oxygen changing the charge compensation mechanism for Li incorporation (mostly based on the presence of 3 + cations and oxygen vacancies at low and high temperatures, respectively). Moreover, it is found that lithium lies in two well-distinct chemical environments in HEO, which cannot be completely explained by assuming a random organization of the high entropy phase. This suggests the existence of some short-range order and possible M3+-Li+ pairs. • Li dissolves into the rock salt HEO phase in substitutional positions. • Single-phase HEO is formed without the Co3+ reduction in the case of Li-doping. • Li sits in two well-distinct chemical environments within the HEO structure. • The presence of some kind of short-range order within the Li-doped HEO is hypothesized. [ABSTRACT FROM AUTHOR]

Graphene and graphene oxide (GO)-based coatings are of great interest due to their mechanical, electrical and/or thermal performance that add functionalities to materials employed in many industrial and biomedical applications. Hybrid diamond-like carbon (DLC)/GO coatings on poly ether etherketone (PEEK) devices, e.g. orthopaedic implants, can add multiple functionalities, such as an enhanced bioactivity. In this work, we describe the mechanical stability and tribological behaviour of such coating, comparing it to a DLC-coated bare PEEK. The GO functionalisation of PEEK is realised from a water solution, whereas the DLC coatings are obtained through plasma-enhanced chemical vapour deposition, using various combinations of different precursor gases. We employ atomic force microscopy to investigate the morphology and interfacial adhesion characteristics of the materials. Then, the scratch coefficient of friction of the samples is measured under both constant-load and progressive-load conditions, also in combination with acoustic emission signals. We identify the most effective and promising plasma treatments to ensure stable coating, and discuss the effect of the presence of an intermediate GO layer. • Hybrid DLC/GO nanocoatings are deposited on PEEK via plasma-enhanced chemical vapour deposition. • The objective is to tune the tribological performance (e.g. wear) and mechanical stability of PEEK. • The scratch coefficient of friction under constant and progressive load is evaluated. • The plasma treatment influences the structure and property of the nanocoatings. • The presence of GO as intermediate layer improves the mechanical stability of the surface. [ABSTRACT FROM AUTHOR]

Transparent conductive materials are important in many applications such as flat panel displays, solar cells, touch screen and smartphones. Films today generally rely on indium tin oxide (ITO). However, indium is rare and its price is rising as demand soars. For this reason, reduced graphene oxide (RGO) is gaining deep interest for its potential to replace ITO to fabricate transparent conductive films. Unfortunately, obtaining well-dispersed RGO flakes is difficult and generally, toxic solvents and heat treatments are employed. In this work, we demonstrate a simple approach to produce reduced graphene oxide (RGO) thin films on glass substrate at room temperature by using a nontoxic solvent. The films RGO colloidal suspensions were deposited on simple and plasma treated glass substrates by drop casting. The results indicate that the transmittance and the conductivity of the films have a linear relationship with the films thickness deposited on the substrates. The conductivity of RGO films deposited on plasma treated glass is higher with respect to substrate without any grafted functional group. The best conductivity obtained for RGO depositions on piranha cleaned glass, treated in an ammonia plasma is 10.4 S cm −1 and the transmittance is 70% at 550 nm which are among the best results if compared to similar non annealed RGO films. [ABSTRACT FROM AUTHOR]

Highlights: [•] Gold nanostars were synthesized by a one-step reduction process. [•] The effect of the pH on the reduction mechanism was investigated. [•] Gold nanostars showed an intense absorption band in the red in agreement with theoretical simulation. [•] Gold nanostars showed a higher Raman enhancement respect to spherical nanoparticles of the same dimension. [ABSTRACT FROM AUTHOR]

Surface Enhanced Raman Scattering (SERS) active gold nanostars represent an opportunity in the field of bioimaging and drug delivery. The combination of gold surface chemical versatility with the possibility to tune the optical properties changing the nanoparticles shape constitutes a multimodal approach for the investigation of the behavior of these carriers inside living cells. In this work, SERS active star-shaped nanoparticles were functionalized with doxorubicin molecules and covered with immuno-mimetic thiolated polyethylene glycol (PEG). Doxorubicin-conjugate gold nanoparticles show an intense Raman enhancement, a good stability in physiological conditions, and a low cytotoxicity. The strong adsorption of the anticancer drug doxorubicin in close contact with the gold nanostars surface enables their use as SERS tag imaging probes in vivo. Upon laser irradiation of the nanoparticles, a strong SERS signal is generated by the doxorubicin molecules close to the nanostars surface, enabling the localization of the nanoparticles inside the cells. After long time irradiation, the SERS signal drops, indicating the thermally driven delivery of the drug inside the cell. Therefore, the combination of SERS and laser scanning confocal microscopy is a powerful technique for the real-time analysis of drug release in living cells. [ABSTRACT FROM AUTHOR]

Abstract: A major application of polyfunctional acid materials is the fabrication of solid electrolytes exhibiting high proton conductivity in the solid state for operation in fuel cells at medium temperature (<160°C) and low humidity (RH). A most recent trend of research in this field is the search of low vapour pressure doping agents designed to provide liquid-like proton transfer in perflurosulfonic acid membranes. A new polyfunctional acid material made of Nafion doped with difluoromethandiphosphonic (DFMDP) acid is reported in the present work. The DFMDP doping agent, melting at 146°C and stable up to 160°C, has been found to enhance by two orders of magnitude the conductivity of neat Nafion in dry environment at 120°C, and to be stable at this temperature even in the presence of 30% RH. The material chemistry responsible of the enhanced conductivity has been studied by several techniques: i.e., potentiometric titration (PT), scanning electron microscopy, wide (WAXS)- and small (SAXS)-angle X-ray scattering, and X-ray photoelectron spectroscopy (XPS). The results allow a number of conclusions. The PT data prove that a multilevel proton acidity wide gradient is present in the DFMDP doped Nafion samples constituting the driving force for proton mobility through the membrane phase. The WAXS and SAXS data prove that the DFMDP molecules are incorporated into the Nafion SO3H ionic domains. The XPS data provide direct evidence of the interaction between the DFMDP PO3H2 and Nafion SO3H groups which allows the proposition of the establishment of H-bonding network between the proton acceptor P=O and P–OH sites and the proton donor SO3H group. The conductivity data for the DFMDP membranes, compared to other data obtained for membranes made by other sulfonated polymers doped with H3PO4, offer intriguing perspectives for the design of solid electrolytes exhibiting enhanced conductivity in dry or low humidity environment. [Copyright &y& Elsevier]

The results of in vitro studies of single-walled carbon nanohorn (SWCNH) oxidized materials' cytotoxicity obtained by the cell membrane integrity (Neutral Red Uptake (NRU)) and metabolic activity (by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)) on A549 and human dermal fibroblasts (HDF) cell lines are presented. We also present hemocompatibility studies on human and porcine blood, and an erythrocyte concentrate to prove that the obtained samples will not interfere with blood components. Characterization of the materials is supplemented by ζ-potential measurements, Transmission Electron Microscope (TEM) imaging, and thermogravimetric studies (TG). The presented results show the correlation between the specific surface area of materials and the platelet aggregation, when the ID/IG ratio determined from Raman spectra correlates with hemoglobin release from the erythrocytes (in whole blood testing). A plausible mechanism explaining the observed correlations is given. The cytotoxicity and hemocompatibility studies prove that the studied materials are acceptable for use in biomedical applications, especially a sample SWCNH-ox-1.5 with the best application potential. [ABSTRACT FROM AUTHOR]

Electrophoretic production of anticorrosion carbonaceous coatings on copper could be successfully performed by anodic oxidation of negatively charged graphene platelets suspended in an aqueous solution. The various platelets were synthesized by Hummer's method followed by a hydrothermal reduction in the presence of NH4SCN which was expected to substitute some parts of graphene structure with nitrogen and sulfur groups. X-ray photoelectron spectroscopy analysis confirmed that the graphene precursors, as well as the coatings, contained typical nitrogen groups, such as pyridinic and pyrrolic, and sulfur groups, such as thiol, thiophene, or C-SO2. However, due to oxidation during deposition, the qualitative and quantitative composition of the graphene coatings changed relative to the composition of the precursors. In particular, the concentration of nitrogen and sulfur dropped and some thiophene groups were oxidized to C-SO2. Studies showed the functionalized coatings had a uniform, defect-free, hydrophobic, more adhesive surface than nonmodified films. The corrosion measurements demonstrated that these coatings had better protective properties than the ones without these heteroatoms. This behavior can be assigned to the catalytic activity of nitrogen towards oxidation of C-SO2 groups to C-SO3H with oxygen. [ABSTRACT FROM AUTHOR]

The effects induced by microwave field upon tungsten wires of different diameters were investigated. Tungsten wires with 0.5 and 1.0 mm diameters were placed in the focal point of a single-mode cylindrical cavity linked to a microwave generator and exposed to microwave field in ambient air. The experimental results showed that the 0.5 mm diameter wire was completely vaporized due to microwaves strong absorption, while the wire with 1 mm diameter was not ignited. During the interaction between microwaves and tungsten wire with 0.5 mm diameter, a plasma with a high electronic excitation temperature was obtained. The theoretical analysis of the experiment showed that the voltage generated by metallic wires in interaction with microwaves depended on their electric resistance in AC and the power of the microwave field. The physical parameters and dimension of the metallic wire play a crucial role in the ignition process of the plasma by the microwave field. This new and simple method to generate a high-temperature plasma from a metallic wire could have many applications, especially in metal oxides synthesis, metal coatings, or thin film deposition. [ABSTRACT FROM AUTHOR]

This study investigates the effect of graphene scaffold on morphology, viability, cytoskeleton, focal contacts, mitochondrial network morphology and activity in BALB/3T3 fibroblasts and provides new data on biocompatibility of the "graphene-family nanomaterials". We used graphene monolayer applied onto glass cover slide by electrochemical delamination method and regular glass cover slide, as a reference. The morphology of fibroblasts growing on graphene was unaltered, and the cell viability was 95% compared to control cells on non-coated glass slide. There was no significant difference in the cell size (spreading) between both groups studied. Graphene platform significantly increased BALB/3T3 cell mitochondrial activity (WST-8 test) compared to glass substrate. To demonstrate the variability in focal contacts pattern, the effect of graphene on vinculin was examined, which revealed a significant increase in focal contact size comparing to control-glass slide. There was no disruption in mitochondrial network morphology, which was branched and well connected in relation to the control group. Evaluation of the JC-1 red/green fluorescence intensity ratio revealed similar levels of mitochondrial membrane potential in cells growing on graphene-coated and uncoated slides. These results indicate that graphene monolayer scaffold is cytocompatible with connective tissue cells examined and could be beneficial for tissue engineering therapy. [ABSTRACT FROM AUTHOR]

Hybrid nanomaterials fabricated by the heterogeneous integration of 1D (carbon nanotubes) and 2D (graphene oxide) nanomaterials showed synergy in electrical and mechanical properties. Here, we reported the infiltration of carboxylic functionalized single-walled carbon nanotubes (C-SWNT) into free-standing graphene oxide (GO) paper for better electrical and mechanical properties than native GO. The stacking arrangement of GO sheets and its alteration in the presence of C-SWNT were comprehensively explored through scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. The C-SWNTs bridges between different GO sheets produce a pathway for the flow of electrical charges and provide a tougher hybrid system. The nanoscopic surface potential map reveals a higher work function of the individual functionalised SWNTs than surrounded GO sheets showing efficient charge exchange. We observed the enhanced conductivity up to 50 times and capacitance up to 3.5 times of the hybrid structure than the GO-paper. The laminate of polystyrene composites provided higher elastic modulus and mechanical strength when hybrid paper is used, thus paving the way for the exploitation of hybrid filler formulation in designing polymer composites. [ABSTRACT FROM AUTHOR]

Recently, several chemical and physical treatments were developed to improve different properties of wood. Such treatments are applicable to many types of cellulose-based materials. Densification leads the group in terms of mechanical results and comprises a chemical treatment followed by a thermo-compression stage. First, chemicals selectively etch the matrix of lignin and hemicellulose. Then, thermo-compression increases the packing density of cellulose microfibrils boosting mechanical performance. In this paper, in comparison with the state-of-the-art for wood treatments we introduce an additional nano-reinforcemeent on densified giant reed to further improve the mechanical performance. The modified nanocomposite materials are stiffer, stronger, tougher and show higher fire resistance. After the addition of nanoparticles, no relevant structural modification is induced as they are located in the gaps between cellulose microfibrils. Their peculiar positioning could increase the interfacial adhesion energy and improve the stress transfer between cellulose microfibrils. The presented process stands as a viable solution to introduce nanoparticles as new functionalities into cellulose-based natural materials. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) thin films and coatings are regarded as superior in quality to other materials especially for biomedical applications. However, the lack of stability and understanding of their structure and defects hinder their use in value added applications. Here, we describe our successful attempt at stabilizing, reducing and functionalizing GO through multiple plasma treatments with polymerizing (to deposit a crosslinking and compressing layer of diamond like carbon, DLC) and non‐polymerizing precursors (H2, O2, and N2). The hybrid GO and DLC coatings on semi crystalline PEEK were evaluated using AFM, SEM, and XPS. The GO deposited layer showed roughness around 70 nm and, despite care, resulted in several wrinkles and particle aggregations. The hybrid coatings conformed to the roughness and crystalline features of PEEK. XPS showed that the DLC layer cross‐linked the GO nano‐flakes while not completely masking which enable the partial exposure of GO. The GO‐DLC hybrid interface is higher in thickness than the PEEK‐GO and is dominating the overall thickness of the hybrid structure ≈13 ± 1 μm. XPS measurements showed that the often unstable CO functional groups on the surface of the hybrid coating can be reduced by effective plasma treatment. Plasma treatments also generated CO functional groups that probably originated from the decomposed carboxyl groups. The plasma treatment also contributed to the reduction of GO. Treatment with H2 was more effective in oxygen reduction than with the N2, however, treatment with N2 increased the reactants on GO as N2 is heavier tending to deposit more on a surface. Plasma treatment with O2 increased the surface oxygen content further and hence more defects on the hybrid surface. Schematic view for the arrangement of GO andDLC layers over PEEK substrate. SEM image of the cross sectionof the hybrid GO/DLC on the PEEK substrate. The arrows areshowing the thickness of the corresponding layers. The present imageis from sample no. 2d. [ABSTRACT FROM AUTHOR]