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A new carboxylation of graphene oxide is possible using succinic anhydride, exploiting an unexampled reactivity of epoxide groups. The carboxyl-enriched GO can then be chemically reduced obtaining an unprecedented water-dispersible RGO material.

p-Cu2O/n-TiO2 photoanodes were produced by electrodeposition of octahedral p-type Cu2O nanoparticles over n-type TiO2 nanotubes. The photoresponse of the composite p-n photoanodes was evaluated in photoelectrochemical cells operating at "zero-bias" conditions under either visible or UV-vis irradiation. In both operating conditions, the produced electrodes invariably followed the p-n-based photoanode operations but exhibited lower photoelectrochemical performance as compared to the bare n-TiO2 photoanode under UV-vis light. The reported experimental analysis evidenced that such decreased photoactivity is mainly induced by the scarce efficiency of the nanosized p-n interfaces upon irradiation. To overcome such limitation, a restructuring of the originally electrodeposited p-Cu2O was promoted, following a photoelectrochemical post-treatment strategy. p-Cu2O, restructured in a 2D leaf-like morphology, allowed reaching an improved photoelectrochemical performance for the p-n-based photoanode under UV-vis light. As compared to the bare n-TiO2 behavior, such improvement consisted of photoanodic currents up to three times larger. An analysis of the mechanisms driving the transition from compact (∼100 nm) octahedral p-Cu2O to wider (∼1 μm) 2D leaf-like structures was performed, which highlighted the pivotal role played by the irradiated n-TiO2 NTs.

A novel process is reported which produces an asymmetric supercapacitor through the complete recycling of end-of-life lithium ion batteries. The electrodic powder recovered by industrial scale mechanical treatment of spent batteries was leached and the dissolved metals were precipitated as mixed metals carbonates. Nanowires battery-type positive electrodes were produced by electrodeposition into nanoporous alumina templates from the electrolytic baths prepared by dissolution of the precipitated carbonates. The impact of the different metals contained in the electrodic powder was evaluated by benchmarking the electrochemical performances of the recovered nanowires-based electrodes against electrodes produced by using high-purity salts. Presence of inactive Cu in the nanowires lowered the final capacitance of the electrodes while Ni showed a synergistic effect with cobalt providing a higher capacitance with respect to synthetic Co electrodes. The carbonaceous solid recovered after leaching was in-depth characterized and tested as negative electrode. Both the chemical and electrochemical characterization indicate that the recovered graphite is characterized by the presence of oxygen functionalities introduced by the leaching treatment. This has led to the obtainment of a recovered graphite characterized by an XPS C/O ratio, Raman spectrum and morphology close to literature reports for reduced graphene oxide. The asymmetric supercapacitor assembled using the recovered nanowires-based positive electrodes and graphite as negative electrodes has shown a specific capacitance of 42 F g−1, computed including the whole weight of the positive electrode and recovered graphite, providing a maximum energy density of ~9 Wh kg−1 and a power density of 416 W kg−1 at 2.5 mA cm−2.

A first comparison of the behavior of N-acetyl cysteine (NAC) and ascorbic acid (H2A) towards reduction of graphene oxide (GO) is reported, along with the novel proposition of the associated reaction mechanisms. NAC and H2A are green multi-valent reducing agents, which lead to a mild and biocompatible chemical reduction of oxygenated functional groups in GO. Such reduction has been demonstrated to significantly improve the suitability of GO as a substrate in biomedical applications. A sequence of electrochemical and spectroscopic experiments, theoretical computations and biological tests has been applied to two related series of GO samples mildly reduced with NAC and H2A. These display a downshift of the electrochemical reduction potential characteristic of epoxyl and carbonyl functional groups, associated with an increase in the electron affinity of the substrates. This potential shift, in turn, makes visible a not previously reported reduction feature, associated with hydroxyl groups. Theoretical modelling unveils the reduction mechanisms operating for H2A and NAC on the GO surface, showing their similarity, but also evidencing that NAC remains permanently bonded to the GO surface after reduction, altering the overall reactivity of the reduced GO samples. The mild reduction effect exerted by NAC is stronger in generating attractive biochemical characteristics on GO when compared to H2A. In fact, while administration of NAC to eukaryotic cell lines does not affect the cell viability, this is instead reduced in the case of H2A. The resulting mildly reduced GO materials represent a new step in the direction of GO derivatives with tailored functionalities and oxidation degree for optimized biomedical applications.

Catalytic electroreduction of carbon dioxide represents a promising technology both to reduce CO2 emissions and to store electrical energy from discontinuous sources. In this work, electrochemical deposition of copper on to a gas-diffusion support was tested as a scalable and versatile nanosynthesis technique for the production of catalytic electrodes for CO2 electroreduction. The effect of deposition current density and additives (DAT, DTAB, PEG) on the catalysts’ structure was evaluated. The selectivity of the synthesized catalysts towards the production of CO was evaluated by analyzing the gaseous products obtained using the catalysts as cathodes in electroreduction tests. Catalyst morphology was deeply influenced by the deposition additives. Copper nanospheres, hemispherical microaggregates of nanowires, and shapeless structures were electrodeposited in the presence of dodecyltrimethylammonium bromide (DTAB), 3,5-diamino-1,2,4-triazole (DAT) and polyethylene glycol (PEG), respectively. The effect of the deposition current density on catalyst morphology was also observed and it was found to be additive-specific. DTAB nanostructured electrodes showed the highest selectivity towards CO production, probably attributable to a higher specific surface area. EDX and XPS analysis disclosed the presence of residual DAT and DTAB uniformly distributed onto the catalysts structure. No significant effects of electrodeposition current density and Cu(I)/Cu(II) ratio on the selectivity towards CO were found. In particular, DTAB and DAT electrodes yielded comparable selectivity, although they were characterized by the highest and lowest Cu(I)/Cu(II) ratio, respectively.

The direct synthesis of high-value products from end-of-life Li-ion batteries (LIBs), avoiding the complex and costly separation of the different elements, can be reached through a competitive recycling strategy. Here, we propose the simultaneous synthesis of reduced graphene oxide (rGO) and lithium-manganese-rich (Li1.2Mn0.55Ni0.15Co0.1O2 - LMR) cathode material from end-of-life LIBs. The electrode powder recovered after LIBs mechanical pretreatment was directly subjected to the Hummers’ method. This way, quantitative extraction of the target metals (Co, Ni, Mn) and oxidation of graphite to graphene oxide (GO) were simultaneously achieved, and a Mn-rich metal solution resulted after GO filtration, owing to the use of KMnO4 as an oxidizing agent. This solution, which would routinely constitute a heavy-metal liquid waste, was directly employed for the synthesis of Li1.2Mn0.55Ni0.15Co0.1O2 cathode material. XPS measurements demonstrate the presence in the synthesized LMR of Cu2+, SO42–, and SiO44– impurities, which were previously proposed as effective doping species and can thus explain the improved electrochemical performance of recovered LMR. The GO recovered by filtration was reduced to rGO by using ascorbic acid. To evaluate the role of graphite lithiation/delithiation during battery cycling on rGO production, the implemented synthesis procedure was replicated starting from commercial graphite and from the graphite recovered by a consolidated acidic–reductive leaching procedure for metals extraction. Raman and XPS analysis disclosed that cyclic lithiation/delithiation of graphite during battery life cycle facilitates the graphite exfoliation and thus significantly increases conversion to rGO., Starting from the electrodic powder of end-of-life Li-ion batteries, lithium- manganese-rich cathode material and reduced graphene oxide were obtained.

A combined experimental and theoretical investigation approach has been applied to the electrochemical reduction of graphene oxide (GO) in order to unravel the corresponding reaction mechanism, so far scarcely addressed in the literature. Reduced graphene oxide (rGO) layers were prepared via electrochemical reduction of GO drop-casted onto hydrogenated Si(111) wafers in aqueous medium. A cyclic potential variation programme was applied at different scan rates, followed by an ex-situ characterization of the obtained rGO deposits by means of X-ray photoelectron spectroscopy (XPS). Elaboration of the cyclic voltammetric curves by deconvolution analysis put in evidence a 2:1 ratio between the reduction charges associated to the first and second reduction event, respectively. By means of density functional theory (DFT) based calculations, focused on the fate of epoxyl and carbonyl groups upon electrochemical reduction, an interpretation of the reduction path of the GO layers has been proposed, consistently with both XPS and CV results. Such interpretation is based on the sequential reduction of epoxyl and carbonyl moieties of GO through a two-electron and one-electron mechanism, respectively.

Hydrogels based on short peptide molecules are interesting biomaterials with wide present and prospective use in biotechnologies. A well-known possible drawback of these materials can be their limited mechanical performance. In order to overcome this problem, we prepared Fmoc-Phe3self-assembling peptides by a biocatalytic approach, and we reinforced the hydrogel with graphene oxide nanosheets. The formulation here proposed confers to the hydrogel additional physicochemical properties without hampering peptide self-assembly. We investigated in depth the effect of nanocarbon morphology on hydrogel properties (i.e. morphology, viscoelastic properties, stiffness, resistance to an applied stress). In view of further developments towards possible clinical applications, we have preliminarily tested the biocompatibility of the composites. Our results showed that the innovative hydrogel composite formulation based on FmocPhe3 and GO is a biomaterial with improved mechanical properties that appears suitable for the development of biotechnological applications.

Despite the efforts devoted to the development of new cathodic materials, cobalt-based lithium-ion batteries (LIBs) remain the first choice for many applications, turning cobalt into a critical raw material. Here, we report a method for the selective recovery of cobalt from mixed LIBs electrode materials. The method relies on the application of a green deep eutectic solvent (DES) and yields an extraction of 90% for cobalt and only 10% for nickel. A solvent extraction procedure was optimized to recover cobalt as cobalt oxalate, which was employed to produce lithium cobalt oxide cathode material. This produced cathode material delivered a discharge capacity of 150 mAh g−1 and a capacity retention between 10 and 100 galvanostatic cycles of 83%. Remarkably, the residual DES solution was reused delivering the same cobalt extraction attained using the fresh DES. Cobalt separation constitutes one of the major bottleneck during LIBs recycling, requiring costly and complex hydrometallurgical operations. The demonstrated selectivity of the implemented leaching method, along with the possibility to reuse the residual DES solution, paves the way to a green recycling alternative allowing for the reintroduction of strategic materials into the LIBs production chain.

A novel family of nanocarbon‐based materials was designed, synthesized, and probed within the context of charge‐transfer cascades. We integrated electron‐donating ferrocenes with light‐harvesting/electron‐donating (metallo)porphyrins and electron‐accepting graphene nanoplates (GNP) into multicomponent conjugates. To control the rate of charge flow between the individual building blocks, we bridged them via oligo‐p‐phenyleneethynylenes of variable lengths by β‐linkages and the Prato–Maggini reaction. With steady‐state absorption, fluorescence, Raman, and XPS measurements we realized the basic physico‐chemical characterization of the photo‐ and redox‐active components and the multicomponent conjugates. Going beyond this, we performed transient absorption measurements and corroborated by single wavelength and target analyses that the selective (metallo)porphyrin photoexcitation triggers a cascade of charge transfer events, that is, charge separation, charge shift, and charge recombination, to enable the directed charge flow. The net result is a few nanosecond‐lived charge‐separated state featuring a GNP‐delocalized electron and a one‐electron oxidized ferrocenium., Nanocarbon‐based charge‐transfer cascades were designed by integrating electron‐donating ferrocenes with light‐harvesting/electron‐donating (metallo)porphyrins and electron‐accepting graphene nanoplates. The building blocks were bridged through oligo‐p‐phenyleneethynylenes. Physico‐chemical characterization of the multicomponent conjugates revealed a selective photoexcitation triggered cascade of charge transfer events.

Detonation nanodiamonds (DNDs) were functionalized by ruthenium porphyrins and used as catalysts in the cyclopropanation reaction of olefins. The heterogeneous catalyst was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and XPS (X-ray photoelectron spectroscopy). The XPS was used to control the binding of the ruthenium porphyrin to the DNDs’ surface. This catalyst was used in the cyclopropanation reactions of simple olefins and was reused with no loss of activity in four consecutive cycles, after recovering each time by simple centrifugation.

We probed a series of multicomponent electron donor2-donor1-acceptor1 conjugates both experimentally and computationally. The conjugates are based on the light harvester and primary electron-donor zinc-porphyrin (ZnP, donor1) to whose β positions a secondary electron-donor ferrocene (Fc, donor2) and the primary electron-acceptor C60-fullerene (C60, acceptor1) are attached. Linking all of them via p-phenylene-acetylene/acetylene bridges of different lengths to gain full control over shuttling electrons and holes between C60, ZnP, and Fc is novel. Different charge-separation, charge-transfer, and charge-recombination routes have been demonstrated, both by transient absorption spectroscopy measurements on the femto, pico-, nano-, and microsecond time scales and by multiwavelength and target analyses. The molecular wire-like nature of the p-phenylene-acetylene bridges as a function of C60-ZnP and ZnP-Fc distances is decisive in the context of generating distant and long-lived C60•--ZnP-Fc•+ charge-separated states. For the first time, we confirm the presence of two adjacent charge-transfer states, a C60-ZnP•--Fc•+ intermediate in addition to C60•--ZnP•+-Fc, en route to the distant C60•--ZnP-Fc•+ charge-separated state. Our studies demonstrate how the interplay of changes in the reorganization energy and the damping factor of the molecular bridges, in addition to variation in the solvent polarity, affect the outcome of the charge-transfer and corresponding rate constants. The different regions of the Marcus parabola are highly relevant in this matter: The charge recombination of, for example, the adjacent C60•--ZnP•+-Fc charge-separated state is located in the inverted region, while that of the distant C60•--ZnP-Fc•+ charge-separated state lies in the normal region. Here, the larger reorganization energy of Fc relative to ZnP makes the difference.

Poly (triaryl amine) (PTAA) is one of the promising hole transport materials (HTM) for perovskite solar cells. Highly efficient PTAA-devices have been demonstrated in both direct (n-i-p) and inverted (p-i-n) architectures. In the inverted structures, the device suffers from poor coverage of the perovskite film over the hydrophobic PTAA surface. To address this issue, we exploited an easy and efficient approach utilizing a short-time UV treatment of the PTAA layer prior to the perovskite deposition. The UV-treatment improved the optical properties of PTAA layers, which synergistically helps the light harvesting of the perovskite. Enhanced grain sizes, together with the decrease of recombination centers in the UV treated dopant-free PTAA, lead to efficient perovskite solar cell with PCE reaching 19.17% for 0.09 cm2 active area. Moreover, the device retains over 75% of its initial efficiency after 1400 h storage in ambient condition with average relative humidity (RH) of 50%. Additionally, the effect of UV light was studied on PTAA with different molecular weights. Non-destructive UV exposure more predominantly improved the efficiency of lower molecular weight PTAA-based device. A maximum PCE of 12.3% for 1 cm2-sized cells using 5 min-UV PTAA with low MW is achieved. This investigation points to the main roles of the HTL quality for the development of high-efficiency photovoltaic solar cells and provides a fast, easy and cost-effective method toward upscaling.

Hydrothermal carbonization (HTC) is a promising technology for producing char material (hydrochar) from waste biomass. In the present work, a two-stage process was applied and optimized to obtain a composite Fe-loaded hydrochar effective in removing arsenic from water. The first stage of carbonization of the biomass in acid conditions was followed by loading Fe3O4 in the second stage into the hydrochar by alkaline co-precipitation. The effect on the kinetics and on the final yield of HTC induced by a variation of the initial acid pH (5.6, 2.0, and 0.5) was tested. Biomass hydrolysis initially decreased the hydrochar yield and released soluble organic species, responsible for the observed pH variation. This effect was more remarkable at the lower initial pH tested. Soluble organic compounds eventually underwent polymerization, with secondary char formation, an inversion of the pH trend and an increase of hydrochar yield and C%. The final pH attained was linearly related to the hydrochar C%, O/C ratio, and initial pH. Better carbonization performances were achieved at pH = 0.5, 200 °C, and 30 min reaction time, which resulted in 53% mass yield and 72 C%. This value is larger than those previously reported for processes conducted at higher temperatures, and it shows how the addition of acid allows working at lower operative temperatures. Fe loading gave better yields at lower hydrochar concentrations, producing an adsorbent with up to 74% Fe3O4, which adsorbed 2.67 mg/g arsenic. Its adsorption capacity was remarkably affected by the stirring method used, indicating that particle-to-particle interactions considerably influence the process. This effect should be better studied for improved applications in fixed-bed columns.

In this study, polythiophene copolymers have been used as modifier for electrode surfaces in order to allow the immobilization of active pyrroloquinoline quinone dependent glucose dehydrogenase (PQQ-GDH) and to simultaneously improve the direct electrical connection of the enzyme with the electrode. Polymer films are electrosynthesized in aqueous solution without the need of surfactants onto carbon nanotubes modified gold electrodes from mixtures of 3-thiopheneacetic acid (ThCH2CO2H) and 3-methoxythiophene (ThOCH3) using a potentiostatic pulse method. Polythiophene deposition significantly improves the bioelectrocatalysis of PQQ-GDH: the process starts at − 200 mV vs. Ag/AgCl and allows well-defined glucose detection at 0 V vs. Ag/AgCl with high current density. Several parameters of the electro-polymerization method have been evaluated to maximize the anodic current output after enzyme coupling. The polymer deposited by this new procedure has been morphologically and chemically characterized by different methods (SEM, EDX, FT-IR, UV–Vis, XPS and Raman spectroscopy). The bioelectrocatalytic response towards increasing glucose concentrations exhibits a dynamic range extending from 1 μM to 2 mM. The low applied potential allows to avoid interferences from easily oxidizable substances such as uric acid and ascorbic acid. Short and long-term stability has been evaluated. Finally, the PQQ-GDH electrode has been coupled to a bilirubin oxidase (BOD)- and carbon nanotube-based cathode in order to test its performance as anode of a biofuel cell. The promising results suggest a further investigation of this kind of polymers and, in particular, the study of the interaction with other enzymes in order to employ them in building up biosensors and biofuel cells.

Nanoporous NiO thin films were prepared onto FTO glass substrates by means of screen-printing and were sensitized with Erythrosine B (EryB) dye. The obtained material was electrochemically treated and characterized with ex-situ X-ray photoelectron spectroscopy in order to gain information beneficial to the application of sensitized NiO as photocathodes of p-type dye-sensitized solar cells (p-DSCs). In particular, EryB-sensitized NiO films underwent a series of electrochemical treatments in LiClO4/Acetonitrile (ACN) electrolyte devised so as to simulate possible conditions the electrode might encounter during operation in the photoelectrochemical cell. Upon potential-cycling in a range where the two NiO faradic events Ni(II) → Ni(III) and Ni(III) → Ni(IV) occur, X-ray photoelectron spectroscopy revealed that Erythrosine B dye experiences a partial detachment from the NiO surface. This detachment seems to be paralleled by the formation of stable (Ni)+(ClO4)− couples. Overall, the EryB dye displayed an acceptable electrochemical stability onto the surface of NiO electrode up to 50 cyclic voltammetries in the range −0.27 ÷ +1.13 V vs. Ag/AgCl. These results are useful for the evaluation of electrochemical stability of the dye when this is immobilized onto an electrode surface and are beneficial for a better comprehension of the degradation phenomena operating in real photoconversion device.

The establishment of a polythiophene-supported electron transfer of PQQ-dependent glucose dehydrogenase (PQQ-GDH) at multiwalled carbon nanotubes is reported. For this purpose, thiol-functionalized MWCNTs are deposited on a gold electrode, which is further modified by on-top electropolymerization of different thiophene monomers. The enzyme is covalently bound to such an electrode by activating the carboxy groups of the polymer. The presence of the polythiophene copolymers allows for electrochemical wiring of PQQ-GDH that can subsequently transfer the electrons from the glucose oxidation to the electrode. Bioelectrocatalysis starts just at −0.2 V vs. Ag/AgCl and the anodic current reaches high values already at 0 V vs. Ag/AgCl. In order to improve the catalytic response, different parameters in the electropolymerization process are evaluated and buffer effects are investigated. The modified electrode surface is characterized by SEM-EDX, FTIR, UV–vis and XPS. The bioelectrocatalytic response towards increasing glucose concentrations is measured at 0 V vs. Ag/AgCl, showing a dynamic range extending from 1 μM to 500 μM.

We demonstrate that N-acetyl cysteine (NAC) reduces graphene oxide (GO) at room temperature. This represents a new green method to produce reduced GO (rGO). NAC adheres to the rGO surface as demonstrated by several spectroscopy techniques and avoids GO-mediated oxidation of glutathione. This method offers new opportunities for the production of green biocompatible rGO and NAC-based therapies.

A novel process is proposed to produce nanostructured batteries anodes from spent lithium-ion batteries. The electrodic powder recovered by the mechanical treatment of spent batteries was leached and the dissolved metals were precipitated as cobalt carbonates. Two different precipitation routes were separately tested producing cobalt carbonates with different Cu and Fe contents. Nanowire anodes were produced by electrodeposition into nanoporous alumina templates from the electrolytic baths prepared by dissolution of the precipitated carbonates. The electrochemical performances of the produced anodes were evaluated as compared to nanowire anodes produced with the same electrodeposition method but using a synthetic cobalt bath. The application of the carbonates produced by directly precipitating all the leached metals gave nanowires with capacity about halved as compared to the nanowires electrodeposited from the synthetic bath. Selectively removing Cu and Fe prior cobalt carbonate precipitation yielded, in contrast, nanowires with capacity initially larger and then gradually approaching that attained by the nanowire electrodeposited from the synthetic bath. A detailed analysis is presented describing the role of metallic impurities in determining the capacity of the produced nanowires. The impact of the illustrated results for the development of sustainable recycling processes of lithium-ion batteries is discussed.

Electrodeposition of NiOOH is an attracting route toward nanosized films of NiO, a p-type semiconductor used in many advanced applications. In this paper, the deposition mechanism is thoroughly investigated aiming at the clarification of the deposition dynamics and the chemical nature of the deposit. We focused on initial stages of the potentiostatic deposition on ITO, which yields a nanostructured film. In the potential range investigated the process is mass transport controlled and strongly overlaps with oxygen evolution reaction. The nucleation regime, which is finely tunable, correlates with the surface extension of the film. Supporting electrolytes are found to suppress the deposition, likely by modifying the nickel speciation in the aqueous electrolyte. Further, through XPS investigation we shed light on the mixed γ − β NiOOH nature of the deposited film and its electrochemistry. This work provides precious understanding for future exploitations of anodic electrodeposited NiO, especially in applications where a strict control on surface morphology and thickness at the nanoscale level is mandatory.

Integration of graphene on flexible and transparent supports, such as ITO/PET, represents a challenging goal for the realization of next-generation optoelectronic materials. In this context, reduce...

In this work, an electrochemical approach to synthesize Metal-MetalOxide/Hydroxide core-shell nanowires electrodes (NWE) is illustrated. NWE electrodes were obtained by electrodeposition of a targeted metal into the nanopores of nanoporous alumina templates generated by one-step anodization of aluminum. Following metal electrodeposition, the alumina template was selectively etched to obtain an array of free-standing metal nanowires. The imposed electrodeposition conditions allowed directly attaining a core-shell nanostructure, with a metal core covered by a thin metal oxide/hydroxide film. NWE electrodes produced by the proposed synthesis route were tested for the application as electrodes in lithium batteries and supercapacitors. To this purpose, an array of cobalt nanowires (CoNWs) supported by a nanostructured copper current collector was produced by sequential electrodeposition of cobalt and copper, and it was employed as anode in a lithium battery, while a NWE based on Ni-NiO/OH2 (NiNWs) was obtained by nickel electrodeposition and tested as electrode in a supercapacitor. A thorough analysis and characterization of the produced electrodes were performed. The experiments with the lithium cell evidenced the positive effect of metallic core on stability, while the electrochemical characterization of the supercapacitor showed the presence of both NiO and NiOH2 leading, when cycled, to a capacity close to the best literature value.

Wafer-scale integration of reduced graphene oxide with H-terminated Si(1 1 1) surfaces has been accomplished by electrochemical reduction of a thin film of graphene oxide deposited onto Si by drop casting. Two reduction methods have been assayed and carried out in an acetonitrile solution. The initial deposit was subjected either to potential cycling in a 0.1 M TBAPF6/CH3CN solution at scan rates values of 20 mV s−1 and 50 mV s−1, or to a potentiostatic polarization at Eλ,c = −3 V for 450 s. The resulting interface has been characterized in its surface composition, morphology and electrochemical behavior by X-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy and electrochemical measurements. The results evidence that few-layer graphene deposits on H-Si(1 1 1) were obtained after reduction, and use of organic instead of aqueous medium led to a very limited surface oxidation of the Si substrate and a very low oxygen-to-carbon ratio. The described approach is fast, simple, economic, scalable and straightforward, as one reduction cycle is already effective in promoting the establishment of a graphene-Si interface. It avoids thermal treatments at high temperatures, use of aggressive chemicals and the presence of metal contaminants, and enables preservation of Si(1 1 1) surface from oxidation.

Aim: Fabrication of graphene oxide (GO)-based medical devices coatings that limit adhesion of Candida albicans, a main issue of healthcare-associated infections. Methods: The GO composites noncovalently functionalized with curcumin (CU), a hydrophobic molecule with active antimicrobial action, polyethylene glycol (PEG) that hinders the absorption of biomolecules or a combination of CU and PEG (GO–CU–PEG) were drop-casted on surfaces and antifungal efficacy was assessed. Results: We demonstrate that GO–CU–PEG coatings can reduce fungal adhesion, proliferation and biofilm formation. Furthermore, in an aqueous environment, surfaces release curcumin–PEG nanocomposites that have a minimum inhibitory concentration of 9.25 μg/ml against C. albicans. Conclusion: Prevention of early cell adhesion and creation of a proximal environment unfavorable for growth make these GO-supported biomaterials attractive for innovative medical device manufacturing. [Formula: see text]

A novel electrochemical method is proposed to synthesize nanostructured cobalt electrodes for lithium-ion batteries (LIBs). An array of cobalt nanowires (CoNWs) supported by a nanostructured copper current collector was obtained by the sequential electrodeposition of cobalt and copper into the nanopores of alumina templates and selective etching of alumina. The illustrated method can be implemented with one-side open alumina templates generated by one-step aluminium anodization, thus excluding the application alumina membranes and their coating by sputter metal deposition. The cobalt electrodeposition conditions allow to directly form Co-CoO core-shell nanowires, with metallic cobalt nanowires covered by a thin cobalt oxide film. The direct electrochemical growth of copper nanowires connected to CoNWs ensured high electronic conductivity and specific surface area of the resulting electrode, leading to a low interfacial impedance when used in lithium cell. This nanostructure and the enhanced lithium diffusion enabled by the nanowires morphology contributed to achieve a specific capacity of 1500 mAhg −1 after 200 cycles at 2 Ag -1 , and complete restore of the capacity at 2 Ag -1 after cycling at the ultra-high current density of 450 Ag -1 . The faradaic and capacitive contributions to charge storage were estimated by the analysis of cyclic voltammetry experiments carried out at different scan rates. Based on this latter analysis, pseudo-capacitive effects appear to play a pivotal role in determining the total recorded capacity. The advantages of the proposed method to sustain the large scale application of nanowires electrodes in lithium batteries are thoroughly discussed.

Meso-tetraphenylporphyrin connected with a ferrocene molecule in the beta-position of the macrocycle through a triple carbon@carbon bond has been bound to carbon spheres using the Prato@Maggini reaction. The ethynyl or/and phenylene ethynylene subunits were chosen as a linking bridge to give a high conjugation degree between the donor (i. e., ferrocene), the photoactive compound (i. e., porphyrin), and the acceptor (i. e., carbon spheres). The molecular bridges have been directly linked to the beta-pyrrole positions of the porphyrin ring, generating a new example of a long-range donor@acceptor system. Steady-state fluorescence studies together with Raman and XPS measurements helped understanding the chemical and physical properties of the porphyrin ring in the new adduct. The spectroscopic characteristics were also compared with those obtained from a similar compound bearing fullerene instead of carbon spheres. &nbsp

Biocompatible and degradable poly(α-hydroxy acids) are one of the most widely used materials in scaffolds for tissue engineering. Nevertheless, they often need surface modification to improve interaction with cells. Aminolysis is a common method to increase the polymer hydrophilicity and to introduce surface functional groups, able to covalently link or absorb, through electrostatic interaction, bioactive molecules or macromolecules. For this purpose, multi-functional amines, such as diethylenediamine or hexamethylenediamine are used. However, common drawbacks are their toxicity and the introduction of positive charges on the surface. Thus, these kind of modified surfaces are unable to link directly proteins, such as collagens, a promising substrate for many cell types, in particular chondrocytes and osteoblasts. In this work, poly(L-lactide) (PLLA) film surface was labelled with negatively charged sulfonate groups by grafting taurine (TAU) through an aminolysis reaction. The novel modified PLLA film (PLLA-TAU) was able to interact directly with collagen. The reaction was carried out in mild conditions by using a solution of tetrabutylammonium salt of TAU in methanol. ATR-FTIR, XPS and contact angle measurements were used to verify the outcome of the reaction. After the exchange of tetrabutylamonium cation with Na+, collagen was absorbed on the TAU grafted PLLA film (PLLA-TAU-COLL). In vitro biological tests with human primary chondrocytes showed that PLLA-TAU and PLLA-TAU-COLL improved cell viability and adhesion, compared to the unmodified polymer, suggesting that these modifications make PLLA substrate suitable for cartilage repair.

A novel experimental approach to produce graphene/silicon interface is reported, which consists of electrochemically reduced graphene oxide directly in contact with Si(111). The utilized procedure makes use of differently concentrated graphene oxide solutions drop-casted onto a flat crystalline hydrogenated Si(111) surface. Such modified surface was utilized as a working electrode in an electrochemical cell with aqueous electrolyte and subject to cyclic voltammetry in different conditions. After the electrochemical treatments, the electrodes were characterized by means of field-emission scanning electron microscopy microscopy and Raman and X-ray photoelectron spectroscopies. The overall results demonstrate the transformation of graphene oxide into electrochemically reduced graphene oxide over the silicon surface, as evidenced by the abatement of the spectroscopic features associated with oxidized carbon groups and by the increase in the number of graphene-like sp2 carbon domains. These outcomes are new an...

Superhydrophobic surfaces are attracting increasing attention in different fields such as energy, transportation, building industry and electronics, as they exhibit many interesting properties such as high water repellence, anti-fogging, anti-corrosion, anti-fouling and self-cleaning abilities. Here, superhydrophobic nanostructured hybrid materials obtained by depositing alumina nanoparticles on copper surfaces via dip coating in Al 2 O 3 sol are presented. Two different preparation routes were explored, based on either an alcoholic or an aqueous Al 2 O 3 sol, and the resulting wetting properties were compared. Wettability measurements showed that when the alcoholic sol is used superhydrophobicity is attained, with values of water contact angle very close to the upper limit of 180°, while highly hydrophobic coatings are obtained with the aqueous sol. These findings were further supported by electron microscopy and X-ray photoelectron spectroscopy, which revealed that the surface layer deposited on Cu is more homogenous and richer in alumina nanoparticles when the alcoholic sol was used. Durability of the superhydrophobic coating was assessed by performing ageing tests in chemically aggressive environments. A remarkable resistance is displayed by the superhydrophobic coating in acid environment, while alkaline conditions severely affect its properties. Such behaviors were investigated by XPS and FE-SEM measurements, which disclosed the nature of the surface reactions under the different conditions tested. The present results underline that a thorough investigation of surface morphology, chemical composition and wetting properties reveals their strongly connection and helps optimizing the combination of substrate nanostructuring and suitable chemical coating for an improved durability in different aggressive environments.

In the frame of the much debated issue of photostimulated reaction mechanisms on Si-oriented surfaces, the first report is presented here where the presence of saturated anchoring arms in organometallic and organic molecules unexpectedly leads to covalent bonding on H-terminated Si(100). The molecular substrates tested (methyl-, ethyl-, and n-propylferrocene, 4-chlorotoluene, and 1-chloro-4-ethylbenzene) were chosen considering that the carbon atom directly attached to the benzene ring, C1, sits at a peculiar state of charge also by virtue of σ–π hyperconjugation effect and that it can be sterically hindered in its interaction to a surface if it becomes part of a longer chain. The anchoring reaction was conducted via exposure to low-intensity white light, and the resulting hybrid species were characterized by means of X-ray photoelectron spectroscopy (XPS), electrochemical measurements by cyclic voltammetry (CV), atomic force microscopy (AFM), and density functional theory (DFT) calculations. At variance ...

Electrodeposition from ZnCl2 aqueous solution was performed to grow ZnO thin films on the surface of polycrystalline copper plates. Electrochemical parameters for deposition were optimized by means of cyclic voltammetry (CV). The morphology of the deposits was studied via scanning electron microscopy (SEM), and their chemical composition was ascertained by means of X-ray photoelectron spectroscopy (XPS). The effects of changing the deposition bath temperature (T bath) and the role played by post-deposition treatments, such as temperature and time of annealing in air, were studied. SEM images of freshly deposited vs. annealed samples have shown that in the former case the films display a rough morphology with mixed grain/hexagonal platelets structures and in the latter smaller but more uniformly dispersed cubic grains. T bath is found to be the key parameter to induce the different morphology in the deposited films, which reflects in a different chemical reactivity of surface species, as found on the basis of the binding energies and relative quantitative ratios between Zn 2p and O 1s peaks. In fact, a higher T bath favours a more efficient desorption of OH groups upon annealing, the O 1s peak resulting to much more drastically modified oxide/hydroxide intensity ratio with respect to the case of the sample deposited at lower T bath.

The assembly of gold nanoparticles (AuNPs) on a hydrogenated Si(100) surface, mediated by a series of hierarchical and reversible complexation processes, is reported. The proposed multi-step sequence involves a redox-active ditopic guest and suitable calix[n]arene-based hosts, used as functional organic monolayers of the two inorganic components. Surface reactions and controlled release of AuNPs have been monitored by application of XPS, atomic force microscopy (AFM), field-emission scanning electron microscopy (FESEM) and electrochemistry.

Introduction Recently, we introduced a new deposition method, based on Ion Plating Plasma Assisted technology, to coat titanium implants with a thin but hard nanostructured layer composed of titanium carbide and titanium oxides, clustered around graphitic carbon. The nanostructured layer has a double effect: protects the bulk titanium against the harsh conditions of biological tissues and in the same time has a stimulating action on osteoblasts. Results The aim of this work is to describe the biological effects of this layer on osteoblasts cultured in vitro. We demonstrate that the nanostructured layer causes an overexpression of many early genes correlated to proteins involved in bone turnover and an increase in the number of surface receptors for alpha 3 beta 1 integrin, talin, paxillin. Analyses at single-cell level, by scanning electron microscopy, atomic force microscopy, and single cell force spectroscopy, show how the proliferation, adhesion and spreading of cells cultured on coated titanium samples are higher than on uncoated titanium ones. Finally, the chemistry of the layer induces a better formation of blood clots and a higher number of adhered platelets, compared to the uncoated cases, and these are useful features to improve the speed of implant osseointegration. Conclusion In summary, the nanostructured TiC film, due to its physical and chemical properties, can be used to protect the implants and to improve their acceptance by the bone.

Cobalt hexagonal nanoplatelets and cobalt nanoflakes were produced by electrodeposition onto aluminium from cobalt sulphate solutions. The dependence of the nanostructure morphology on cobalt ion concentration and potential was investigated under potentiostatic and pulsed-electrodeposition. Under potentiostatic electrodeposition, cobalt hexagonal nanoplatelets were obtained with cobalt ion concentration equal to 0.01 and 0.1 M, while cobalt hydroxide nanoflakes were formed as the cobalt ion concentration was increased to 0.2 M. Under pulsed electrodeposition, both hexagonal nanoplatelets and hydroxide nanoflakes could be obtained with cobalt ion concentration equal to 0.1 M by modulation of the imposed current/potential wave. The analysis of the current transients recorded under potentiostatic electrodeposition and the microscopic analysis of the deposits indicate that three-dimensional diffusion control cannot adequately describe the growth of the cobalt nanostructures. We propose that an aggregative growth mechanism involving the formation and the surface diffusion of cobalt nanoclusters can explain the influence of electrodeposition parameters on the morphology of the cobalt nanostructures.

The results of an X-ray Photoelectron Spectroscopy study conducted on a series of gold nanoparticles recently reported by us, stabilized by monodentate, bidentate, tridentate and tetradentate thiolate calix[n]arene ligands, are presented here. By virtue of the different denticity of the ligands, the nuclearity of the resulting particles can be tuned down to the subnanometric range. From the present XPS results, a clear correlation among the experimental binding energy of single Au 4f peak components and the specific Au state of charge is proposed, where the smaller (i.e., nanometer) fraction of the series selectively shows negatively charged Au atoms. Our findings are relevant for the open discussion of a specific role played by negatively charged Au atoms in catalytic reactions, especially at low temperatures.

CsI thin film photocathodes of 600 nm thickness deposited on polished Al surfaces by resistive evaporation technique were studied by angle-resolved X-ray photoelectron spectroscopy (ARXPS), before and after UV-irradiation under vacuum. It is shown that the "UV-irradiated" sample keeps the stoichiometric ratio Cs:1 unchanged (1:1) while it shows a higher concentration of carbon in comparison with "as-deposited" samples. The morphology of the "as-deposited" sample is strongly affected after VUV-irradiation. The consequence of such effects on the physical and chemical properties of the "as-deposited" and "UV-irradiated" CsI thin film photocathodes is discussed. (C) 2009 Elsevier B.V. All rights reserved.

The spatial self-organization of molecular species on an Si oriented surface can be less ideal than that of an SAM on a metal, likely affecting the electronic structure of the resulting hybrids and their electrochemical response as electrodes in solution. In order to investigate such effects, a series of molecular precursors was investigated, consisting of three substituted ferrocenes with a lateral C–C group fully saturated (ethylferrocene) or with a single (vinylferrocene) or double unsaturation (ethynylferrocene). The corresponding functionalized Si(100) wafers were produced following new or literature recipes, starting from hydrogenated Si surfaces. The relationship between the degree of unsaturation in the anchored arm of each adduct and its electronic structure and electrochemical behaviour was investigated by comparing experimental (XPS, electrochemical) and ab initio results of the redox potentials in the series. Density functional theory (DFT) was applied, with inclusion of solute–solvent interactions. Different bond arrangements of the C–C arm with Si surface dimer atoms have been produced theoretically within the series of ferrocenes. Distinct values of redox potentials were displayed by the hybrids, which can be consistently related to the structural differences presented. In fact, measured and computed potentials showed a very satisfactory match only for specific adduct isomers, providing strong indications that the carbon–carbon unsaturation initially present in the anchoring arm is preserved upon addition reaction, an unprecedented result. The demonstrated tunability of a well-defined switching potential in these molecules on silicon can be beneficial to the development of Si-based memory devices.

Metalloporphyrins bound to silicon wafers exhibit a redox behaviour useful for information storage and resist the conditions of temperature required for processing real devices. An XPS and AFM study has been undertaken to evidence and understand the electronic states of different free bases and metalloporphyrins on Si(100) and (111). Both carbosilane (RC–Si) and alkoxysilane (RO–Si) bonds have been produced via thermal and electrochemical routes. In the resulting hybrids XPS has revealed, for the first time, that porphyrins exist as two distinct species on silicon. The behaviour of Co, Cu and Zn(II) porphyrinates has been evidenced, and a strategy to improve the molecular coverage by use of an organic spacer has been also proposed. The results will assist in the choice of suitable candidates for molecular electronics.

Three distinct wet chemistry recipes were applied to hydrogen-terminated n- and p-Si(100) surfaces in a comparative study of the. covalent grafting of two differently substituted 2.2'-bipyridines. The applied reactions require the use of heat, or visible light under a controlled atmosphere, or a suitable potential in an electrochemical cell. In this last case, hydrogen-terminated silicon is the working electrode in a cathodic electrografting (CEG) reaction, in which it is kept under reduction conditions. The resulting Si-C bound hybrids were characterized by a combination of AFM, dynamic contact-angle, and XPS analysis, with the help of theoretical calculations. The three distinct approaches were found to be suitable for obtaining ligand-functionalized Si surfaces. CEG resulted in the most satisfactory anchoring procedure, because of its better correlation between high coverage and preservation of the Si surface from both oxidation and contamination. The corresponding Si-bipyridine hybrid was reacted in a solution of CH 3 CN containing CU 1 ions coordinatively bound to the anchored ligands, as evidenced from the XPS binding-energy shift of the N atom donor functions. The reaction gave a 1:2 Cu-bipyridine surface complex, in which two ligands couple to a single Cu 1 ion. The surface complex was characterized by the Cu Auger parameter and Cu/N XPS atomic-ratio values coincident with those for pure, unsupported Cu 1 complex with the same 2,2'-bipyridine. Further support for such a specific metal-ligand interaction at the functionalized Si surface came from the distinct values of Cu2p binding energy and the Cu Auger parameter, which were obtained for the species resulting from Cu 1 ion uptake on hydrogen-terminated Si(100).

A series of lipophilic gold nanoparticles (AuNPs) circa 5 nm in diameter and having a mixed organic layer consisting of 1-dodecanethiol and 1-(11-mercaptoundecyl) pyridinium bromide was synthesised by reacting tetraoctylammonium bromide stabilised AuNPs in toluene with different mixtures of the two thiolate ligands. A bidentate ω-alkylthiolate calix[4]arene derivative was instead used as a functional protecting layer on AgNPs of approximately 3 nm. The functionalised nanoparticles were characterised by transmission electron microscopy (TEM), and by UV/Vis and X-ray photoelectron spectroscopy (XPS). Recognition of the pyridinium moieties loaded on the AuNPs by the calix[4]arene units immobilised on the AgNPs was demonstrated in solution of weakly polar solvents by UV/Vis titrations and DLS measurements. The extent of Au-AgNPs aggregation, shown through the low-energy shift of their surface plasmon bands (SPB), was strongly dependent on the loading of the pyridinium moieties present in the organic layer of the AuNPs. Extensive aggregation between dodecanethiol-capped AuNPs and the Ag calix[4]arene-functionalised NPs was also promoted by the action of a simple N-octyl pyridinium difunctional supramolecular linker. This linker can interdigitate through its long fatty tail in the organic layer of the dodecanethiol-capped AuNPs, and simultaneously interact through its pyridinium moiety with the calix[4]arene units at the surface of the modified AgNPs.

A new series of ligands, containing one (L1H 2 -L4H 2 ) or two (L5H 4 -L6H 4 ) 1,4,8,11 -tetraaza-5,7-dione units and functionalized with a propargyl group on the C atom between the C=0 moieties, has been synthesized. Protonation constants for the ligands and formation constants of their Cu 2+ complexes have been determined in water, and the coordination geometry of the complexes existing at various pH values has been investigated by coupled pH-metric and spectrophotometric titrations. Ligands capable of simple uptake of Cu 2+ with the formation of neutral, square-planar complexes containing the -2-charged diamino-diimido donor sets and ligands containing further coordinating groups (quinoline or pyridine) capable of single and double cation translocation have been investigated. The role of the substituents on the amino groups and the structural role played by the propargyl group have been examined as regards Cu 2+ complexation and translocation. In the double-translocating ligand L6H 4 , when the two Cu 2+ ions move inside the diamino-diamido donor set, the slim propargyl group allows an unprecedented folding of the whole ligand with apical coordination of one pyridine to form a five-coordinate, square-pyramidal Cu 2+ ion. The crystal and molecular structures of this unusual [L6Cu 2 ] complex have been determined by X-ray diffraction. Finally, oxidation of Cu 2+ to Cu 3+ has been studied by cyclic voltammetry in water, which revealed that the redox reaction occurs only when the copper cation is within the diamino-diimido compartment. Moreover, both functionalization of the primary amines with bulky substituents and apical coordination of Cu 2+ make access to the 3+ oxidation state more difficult and disrupt the reversibility of the electrochemical process.

A reversible electrochemical behavior is demonstrated on a specially prepared redox-functionalized H-Si(100) surface, obtained via an extra-mild grafting procedure from vinylferrocene. The results of a detailed XPS and electrochemical characterization of the resulting hybrid are reported and discussed to propose it as a reference system for high-quality electroactive monolayers on Si. The investigated ferrocene derivative bears a functional group suitable for a mild route to covalent anchoring on Si, which is based on a photoinduced reaction with visible light under an inert atmosphere. Electrochemical reversibility is shown by sharp symmetric voltammograms on freshly prepared p-Si electrodes. Anodic oxide growth is responsible for the progressive degradation of the electrochemical response. Still, fast electron transfer to the surface redox species is maintained during several thousands cycles.