Two electrodeposition strategies for the morphology-controlled synthesis of cobalt nanostructures

In this contribution, two different strategies are discussed to synthesize cobalt nanostructures: direct cobalt electrodeposition on a planar aluminum electrode and cobalt electrodeposition into nanoporous alumina templates generated by aluminum anodization (template electrodeposition). In the direct electrodeposition of cobalt on aluminum, cobalt nanoparticles are formed during the early stage of electrodeposition, which causes the depletion of cobalt ions near the electrode. Water reduction then takes place catalyzed by electrodeposited cobalt nanoparticles, which increases the pH near the electrode and can induce cobalt hydroxide precipitation. By varying the electrode potential and the cobalt ion concentration, the interplay between electrochemical growth of cobalt and water reduction could be controlled to induce transition from cobalt hexagonal nano-platelets to nanostructured films composed of cobalt nanoparticles and cobalt hydroxide nano-flakes. Cobalt nanowires can be synthesized by electrodeposition into nanoporous alumina templates generated by aluminum anodization. This approach typically involves the application of alumina templates produced by a two-step anodization procedure: the alumina nanoporous layer generated by a first anodization is dissolved in a chromic acid solution while a very ordered alumina nanoporous layer is produced by a second anodization stage. In accordance with previous studies, this procedure is fundamental to achieve uniform filling of the nanopores in the subsequent electrodeposition stage. In the present study, uniform filling of the nanoporous alumina generated by one-step anodization could be achieved by the electrodeposition of cobalt nanowires. This result was made possible by the application of a novel pulsed electrodeposition strategy

Synthesis of cobalt nanoparticles by electrodeposition onto aluminium foils

In this contribution a study of electrochemical deposition of cobalt nanoparticles onto aluminium foils is presented. The study is aimed at deriving information required for design and control of cobalt nanoparticles electrodeposition onto aluminium foams employed as catalysts support in ethanol reforming. A thorough experimental analysis was in this perspective conducted to determine the influence of applied potential and amount of electric charge passing thorough the cell (amount of charge), on number density and size of the synthesized nanoparticles. Chronoamperometric tests were for this purpose performed in a three electrode cell to determine the current responses to variations in the selected operating parameters. Mathematical models accounting for charge transfer and diffusion limitations were implemented to attain fitting of the derived data, leading to an estimation of the number density of active sites. Scanning electron microscopy of cathode aluminium foils was performed to validate the predictions of the employed mathematical models and characterize the influence of the considered operating parameters on the size and number density of the electrodeposited nanoparticles

Full recycling of spent lithium ion batteries with production of core-shell nanowires//exfoliated graphite asymmetric supercapacitor

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 Fg-1, computed including the whole weight of the positive electrode and recovered graphite, providing a maximum energy density of ∼9 Whkg−1 and a power density of 416 Wkg−1 at 2.5 mA cm-

Ti/TiO2/Cu2O electrodes for photocatalytic applications: synthesis and characterization

Energy from renewables (solar, photovoltaic, geothermal), is a major challenge for researchers' efforts in reason of the intermittent nature of these energy sources. Systems like photoelectrochemical (PEC) cells are promising devices that allow the direct conversion of solar energy into electric power and/or chemical fuels. The direct conversion of solar energy in fuels can be achieved using photocatalysts, based on semiconductors like TiO2. In this work TiO2 nanotubes were achieved through “one-step” anodization of titanium, a low cost and accurate method which allowed to control dimensions and morphology of the nanostructured Ti/TiO2 electrodes. Central limit for TiO2 photoconversion efficiency is its wide bandgap (i.e. a3.2eV), which limits light absorption to the ultraviolet region (3-5% of the solar radiation). Composite Cu2O/TiO2 systems have attracted much attention: Cu2O is a promising semiconductor material (bandgap 2.0-2.6eV), suitable to absorb visible light. Traditionally, Cu2O deposition techniques include the impregnation of TiO2 with a copper salt and subsequent calcination, but offers little control on sizes, shape and deposit's composition. In this work we developed an electrodeposition method in order to control Cu2O morphology and sizes in the composed Ti/TiO2/Cu2O electrodes

Electrochemical pretreatments of carbon paper and their effect on the electrodeposition of metallic nanostructures

Gas diffusion electrodes (GDEs) represent a fundamental element for the development of gaseous electrochemical cells like water electrolysis reactors and fuel cells. Various technologies and materials are employed in order to obtain a conductive, stable and gas permeable structure. Among them, carbon-based structures such as carbon paper are widely used: their composition allows the diffusion of gaseous reagents and products and simultaneously does not permit the flooding of the gas-diffusion structure by aqueous electrolytes. However, the hydrophobicity of this material may represent a drawback to water-based electrode synthesis like galvanic deposition, and various chemical or thermal pretreatments were developed in the last decades. A new kind of pre-treatment based on electrical oxidation of the carbon paper surface is here described and evaluated. The electro-oxidative method allows a rapid and localized pre-treatment of the carbon paper, avoiding the use of highly reactive chemicals or long thermal treatments, reducing treatment wastes, time loss and electrical consumption. Surface wettability of the carbon paper before and after pretreatment was compared by contact angle analysis. Pre-treated and virgin carbon paper were subsequently electroplated from a copper deposition bath and deposition morphologies were compared, in order to establish the effect of the pre-treatment. Electroplated supports were analyzed by scanning electron microscopy (SEM) in order to analyze both micro and nanomorphology of the metallic structure

Magnetic force microscopy characterization of cobalt nanoparticles: a preliminary study

In order to characterize magnetic properties of cobalt-based nanoparticles synthesized through electrodeposition on metal substrates, methods must be employed which enable the imaging of sample surface, the selection of a specific nanoparticle, and the accurate evaluation of local magnetic parameters, such as magnetic moment or saturation magnetization. Due to the combination of imaging capability and quantitative probing of ultra-low magnetic field through the use of a nanometer sized tip with a magnetic coating, magnetic force microscopy (MFM) is a promising tool to characterize Co-based nanoparticles directly on substrates. In this work, the report the preliminary results of the use of MFM to analyze Co nanoparticles electrodeposited on an Al substrate. The aim wa to assess the effective capability of this technique to investigate this kind of nanomaterials, foresee offered possibilities, and highlight current limitations to overcome

TiO2nanotubes in lithium-ion batteries

In this contribution we report on electrochemical approaches in TiO2 based electrodes synthesis. TiO2 nanotubes (NTs) were synthesized following a facile anodization of titanium sheets. Optimizing the experimental conditions two electrodes with NTs lengths of ∼10 μm (Long) and ∼2 μm (Short), were obtained. At the end of the anodization the amorphous TiO2 (a-TiO2) was thermally treated to promote the conversion in the anatase crystal phase (c-TiO2). Both the Long and Short NTs electrodes were tested for their applications as anodes in lithium-ion batteries (LIBs). A preliminary comparison was performed to evaluate the role of a-TiO2 and c-TiO2 phases. Here, Short a-TiO2 NTs exhibited a fast storage rate respect to Short c-TiO2. Comparing the NTs length, Long a-TiO2 electrodes exhibited the highest specific capacity, close to the theoretical value. Furthermore, all the electrodes tested showed an excellent capacity retention proceeding with Discharge/Charge cycles

First steps to define murine amniotic fluid stem cell microenvironment

Stem cell niche refers to the microenvironment where stem cells reside in living organisms. Several elements define the niche and regulate stem cell characteristics, such as stromal support cells, gap junctions, soluble factors, extracellular matrix proteins, blood vessels and neural inputs. In the last years, different studies demonstrated the presence of cKit+ cells in human and murine amniotic fluid, which have been defined as amniotic fluid stem (AFS) cells. Firstly, we characterized the murine cKit+ cells present both in the amniotic fluid and in the amnion. Secondly, to analyze the AFS cell microenvironment, we injected murine YFP+ embryonic stem cells (ESC) into the amniotic fluid of E13.5 wild type embryos. Four days after transplantation we found that YFP+ sorted cells maintained the expression of pluripotency markers and that ESC adherent to the amnion were more similar to original ESC in respect to those isolated from the amniotic fluid. Moreover, cytokines evaluation and oxygen concentration analysis revealed in this microenvironment the presence of factors that are considered key regulators in stem cell niches. This is the first indication that AFS cells reside in a microenvironment that possess specific characteristics able to maintain stemness of resident and exogenous stem cells

Practical aspects related to the measurement of the diffuse field absorption coefficient in scaled reverberation rooms

The scaled reverberation room has proven to be an excellent tool for acoustic consultants and professionals alike to carry out comparison tests between acoustic materials and 3D systems or structures. The suitability of a scaled reverberation room is currently under investigation for the evaluation of the frequency-dependent sound absorption. At present, no standard is available on the methods that could be used to derive acoustic absorption coefficients from scaled measurements. In this work practical aspects of ISO 354 have been investigated within a 1:5 scaled reverberation room: a balance has been sought between reducing sample size, to reduce the manufacturing costs of materials, and finding the appropriate sample area, thickness, orientation and edges treatment, to obtain reliable values at mid and high frequencies. Four different materials have been tested. The paper discusses some of the findings of the measurements conducted on the same materials in a full-scale reverberation room according to ISO 354, in a 1:5 scaled reverberation room and in an impedance tube according to ISO 10534-2. The absorption coefficients data collected have been effective in proving that small reverberation room tests can provide compatible results compared to standard ones in 400-5000 Hz frequency range

Comparison of anogenital distance and correlation with vulvo-vaginal atrophy: a pilot study on premenopausal and postmenopausal women

OBJECTIVES: Anogenital distance (AGD) represents the space between labia posterior commissure and anus. This was pilot study to investigate how menopause and so lack of oestrogens affects AGD. METHODS: A total of 109 patients were enrolled. AGD was measured in lithotomy position using sterile paper ruler. Anogenital index (AGI) was used to control 2 variables of height and weight (body mass index, kg/m2). Vaginal health index (VHI) was used to evaluate vaginal wellness. Female sexual function index (FSFI) questionnaire was administered to all women to evaluate the impact of menopause on their sexual function. RESULTS: AGD (30.87 ± 2.98 vs. 17.57 ± 2.18; P = 0.0001) and AGI (1.40 ± 0.21 vs. 0.70 ± 0.15; P = 0.0001) were both significantly lower in the postmenopausal group. Postmenopausal women were affected by vulvovaginal atrophy (VVA) significantly. Thus, VHI scores were dramatically worse in postmenopausal group (23.95 ± 1.28 vs. 10.75 ± 3.41; P = 0.0001) as well as FSFI results (32.68 ± 2.25 vs. 19.78 ± 5.46; P = 0.0001). CONCLUSIONS: This study confirms that AGD in post-menopausal women was significantly shorter than AGD in premenopausal women, correlating with an increase of VVA and sexual impairment. Changes of AGD and AGI demonstrated to predict hormonal changes that may occur after menopause