The commercialization of the Direct Methanol Fuel Cell (DMFC) is limited due to the high cost and low efficiency of the electrocatalysts. In this context, the development of new electrocatalysts able to efficiently oxidize the methanol and to have at the same time low price and high stability is one of the researcher’s milestones. In this work, CoPt alloys with different Pt content were prepared, and the efficiency of the alloys to be used as electrocatalysts for the methanol oxidation reaction (MOR) was investigated. Our data show that the electrocatalytic performance of the CoPt electrodeposited alloys is strongly influenced by the synthesis conditions, mainly by the potential applied during the synthesis. The best electrocatalytic activity was obtained for the samples prepared at −0.8 V/SCE.

In this study, we report the influence of the Pt concentration in CoxPt100−x alloys on the catalytic activity of the alloys for 4-nitrophenol (4-NP) reduction. More precisely, a series of CoxPt100−x alloys with a Pt concentration ranging between 60% and 95% were prepared using electrodeposition at controlled potentials from stable hexachloroplatinate aqueous solution. The Pt concentration was tuned by varying the electrodeposition potential from −0.6 to −0.9 V. The changes in the CoxPt100−x alloy microstructure and crystalline structure have been investigated using SEM and TEM analysis. Our results show that the microstructure and the crystalline structure of the as-prepared materials do not depend on the electrodeposition potential. However, the catalytic activity of CoxPt100−x alloys is closely correlated with the potential applied during electrochemical synthesis, hence the Pt content. We demonstrated that the synthesized materials present a high catalytic activity (approx. 90%) after six cycles of reusability despite the fact that the Pt content of the as-prepared alloys decreases. The easy preparation method that guarantees more than 97% catalytic activity of the CoxPt100−x alloys, the easy recovery from solution, and the possibility of reusing the CoxPt100−x alloys are the benefits of the present study.

Increasing interest has been given in recent years to alternative physical therapies for cancer, with a special focus on magneto-mechanical actuation of magnetic nanoparticles. The reported findings underline the need for highly biocompatible nanostructures, along with suitable mechanical and magnetic properties for different configurations of alternating magnetic fields. Here, we show how the biocompatibility of magnetic nanowires (MNWs), especially CoFe, can be increased by gold coating, which can be used both in cancer therapy and magnetic resonance imaging (MRI). This study provides a new approach in the field of theranostic applications, demonstrating the capabilities of core–shell nanowires to be used both to increase the cancer detection limit (as T2 contrast agents) and for its treatment (through magneto-mechanical actuation). The MNWs were electrodeposited in alumina templates, whereas the gold layer was electroless-plated by galvanic replacement. The gold-coated CoFe nanowires were biocompatible until they induced high cellular death to human osteosarcoma cells via magneto-mechanical actuation. These same MNWs displayed increased relaxivities (r1, r2). Our results show that the gold-coated CoFe nanowires turned out to be highly efficient in tumor cell destruction, and, at the same time, suitable for MRI applications.

CoPt nanowires with low Pt content and optimized catalytic properties for the methanol oxidation reaction (MOR) are synthetized by electrodeposition, and their morphology and composition are investigated. By controlling the synthesis conditions, an increase in the Co concentration from 7% up to 90% is achieved, thus leading to a reduced Pt content. Saccharine was used to control the crystalline structure of the CoPt nanowires. X-ray diffraction investigations revealed that the face-centered cubic crystalline structure transforms into the hcp crystalline structure when saccharine is added into the electrochemical bath. The electrocatalytic performance of CoPt nanowires increases even though the Pt content in the samples decreases due to the change in the crystalline structure. A dramatic increase in the catalytic activity is obtained, from 10 to 85 mA cm(-2) (almost two times higher than the best value reported in the literature on CoPt nanoparticles), making these nanowires the best catalyst candidates for the MOR.

Magnetic nanowires (MNWs) can have their moments reversed via several mechanisms that are controlled using the composition, length, diameter, and density of nanowires in arrays as-synthesized or as individual nanoparticles in assays or gels. This tailoring of magnetic reversal leads to unique properties that can be used as a signature for reading out the type of MNW for applications as nano-barcodes. When synthesized inside track-etched polycarbonate membranes, the resulting MNW-embedded membranes can be used as biocompatible bandaids for detection without contact or optical sighting. When etched out of the growth template, free-floating MNWs are internalized by cells at 37 °C such that cells and/or exosomes can be collected and detected. In applications of cryopreservation, MNWs can be suspended in cryopreservation agents (CPAs) for injection into the blood vessels of tissues and organs as they are vitrified to -200 °C. Using an alternating magnetic field, the MNWs can then be nanowarmed rapidly to prevent crystallization and uniformly to prevent cracking of specimens, for example, as grafts or transplants. This invited paper is a review of recent progress in the specific bioapplications of MNWs to barcodes, biocomposites, and nanowarmers.

Magnetic nanoparticles (MNPs) are playing an increasing role in medical applications, becoming an important tool for cancer detection. In this study, magnetic core-shell CoFe@Au nanowires with optimized biocompatibility, as well as multilayered Au/CoFe/Au nanowires are synthetized by using electrodeposition and electroless-plating techniques. Their morphology and composition are investigated, the materials being tested for their use as T2 contrast agents in MRI. A dramatic increase of r1 and r2 relaxivity values was obtained for the CoFe@Au core-shell nanowires, making these materials best candidates as new MRI contrast agents.

CoPt alloys with Pt contents from 15 to 90% were prepared using low-cost electrochemical deposition. Different samples were synthesized from electrochemical baths at pH = 2.5 and 5.5 in a solution with and without saccharin as an additive. The morphology, composition and crystalline structure of the as-prepared samples were investigated by High Resolution-Scanning Electron Microscopy (HR-SEM), Atomic Force Microscopy (AFM), Ultra-high Resolution-Transmission Electron Microscopy (UHR-TEM), Energy-Dispersive X-ray Spectroscopy (EDX), and X-ray Diffraction (XRD). XRD investigations revealed that fcc crystalline structure transforms into hcp crystalline structure when the pH of the electrochemical bath is increased from 2.5 to 5.5 as well as when saccharin is added to the electrochemical bath. The catalytic performance of the CoPt alloys for the nitro to amino phenol compounds conversion was investigated for all the prepared samples, and the results show that the conversion degree increases (from 11.4 to 96.5%) even though the Pt content in the samples decreases. From the samples prepared from the electrochemical bath with saccharin, a study regarding the effect of contact time was performed. The results indicated that after only 5 min, the CoPt sample prepared at pH = 5.5 in the presence of saccharin completely converted the nitro compound to an amino compound.

Ferromagnetic Co35Fe65, Fe, Co, and Ni nanowires have high saturation magnetizations (Ms) and magnetic anisotropies, making them ideal for magnetic heating in an alternating magnetic field (AMF). Here, Au-tipped nanowires were coated with polyethylene glycol (PEG) and specific absorption rates (SAR) were measured in glycerol. SAR increased when using metals with increasing Ms (Co35Fe65 > Fe > Co > Ni), reaching 1610 ± 20 W g-1 metal at 1 mg metal per ml glycerol for Co35Fe65 nanowires using 190 kHz and 20 kA m-1. Aligning these nanowires parallel to the AMF increased SAR up to 2010 W g-1 Co35Fe65. Next, Co35Fe65 nanowires were used to nanowarm vitrified VS55, a common cryoprotective agent (CPA).Nanowarming rates up to 1000 °C min-1 (5 mg Co35Fe65 per ml VS55) were achieved, which is 20× faster than the critical warming rate (50 °C min-1) for VS55 and other common CPAs. Human dermal fibroblast cells exposed to VS55, and Co35Fe65 nanowire concentrations of 0, 1 and 2.5 mg Fe per ml all showed similar cell viability, indicating that the nanowires had minimal cytotoxicity. With the ability to provide rapid and uniform heating, ferromagnetic nanowires have excellent potential for nanowarming cryopreserved tissues.

In this paper we describe the "composition gradient" effect in polycrystalline CoPt films, which results from an initial increase of Co content during the controlled potential electrochemical deposition at short pulses (10-100 s) from quiescent solutions. At longer times of electrodeposition (100-300 s) the CoPt composition reaches steady-state values. The electrodeposition of Co/Pt represents a case of magnetic alloy deposition of the type FM/NM with a ferromagnetic metal (FM = Fe, Co, Ni) and a nonmagnetic metal (NM = Pt, Au, Ag, Pd, Cu) with widely separated reduction potentials. The measurements of partial current densities provided a key insight to understanding the origin of the "composition gradient". The results show: (i) practically independent cobalt (iCo) partial current density throughout deposition, and (ii) decrease of platinum (iPt) and hydrogen (iH) partial current densities. The theoretical analysis of CoPt electrodeposition at the controlled potential was used to compare experimental and calculated data. The electrochemical behavior of hexachloroplatinate solutions, as well as the crystal structure and morphology of CoPt films have been studied. (C) The Author(s) 2016. Published by ECS. All rights reserved.

In this paper, magnetic properties of CoPt thin films electrodeposited from an aqueous hexachloroplatinate solution at pH 5.5, in presence of saccharin as an additive, are reported. The electrodeposition was carried out on a sputtered Ru-substrate at controlled potential. X-ray diffraction measurements revealed that CoPt thin films prepared in these specific conditions crystallize in the hexagonal close packing (hcp) phase. The variations of the magnetic properties of 15-500 nm CoPt thin films are explained by taking into account the changes in the elemental composition, thickness, dynamics of the surface roughening during the early stages of deposition, and under-layer structure of the Ru-substrate. The structure and the width of the magnetic domains of electrodeposited CoPt thin films were examined by MFM and found to be thickness dependent. (C) 2017 Elsevier B.V. All rights reserved.

Among all transition metals magnetic alloys, Co35Fe65 possesses the highest saturation magnetization B-S = 2.45 T at room temperature given by the so-called "Slater-Pauling limit". For controlled electrodeposition of Co35Fe65 nanowire arrays the following parameters were found to be optimal: electrolyte solution with 1-2 mM malonic acid (MA), ionic ratio Fe+2/Co+2 = 2.0, growth rate, and pulsed potential deposition with time-on (2.5 s) at the potential of -1.15 V/SCE and time-off (1.0 s) at -0.70 V/SCE. These arrays were deposited inside anodic aluminum oxide (AAO) templates that contained columnar nanopores with diameters either 35 or 200 nm. Cyclic voltammetry was used in solution with and without MA and reaction mechanism was proposed to explain the critical role of MA in electrodeposition of CoFe alloys. In addition to uniform deposition of stechiometric Co35Fe65 alloys, a selectivity ratio, (SR) similar to 1.0, were achieved, which means that the atomic ratio of Fe/Co in the nanowire matched the molar ratio of Fe+2/Co+2 in the electrolyte. The magnetic behavior of the subsequent 2.45 T Co35Fe65 nanowire arrays showed that the shape and magnetostatic anisotropies dominated the effective anisotropy, and the impact of magnetocrystalline and magnetelastic anisotropies field was very small. (C) The Author(s) 2016. Published by ECS. All rights reserved.

The results of reverse pulse electrodeposition of CoFeNi films with ultra-high magnetic saturation, i.e. B-s values between 2.4 and 2.59 T, are presented in this work. Based on valence-bond theory (Hund's rule) it was assumed that the electronic configuration of MOH obtained by one electron reduction of electroactive intermediate (MOHads+ + e -> MOHads) or oxidation of metal (M - e + HOH -> MOH + H+) would result with larger number of spins per atom for each of transition metals in MOH-precipitated in CoFeNi deposit-with one more spin than their respective neutral metal in the order: Fe > Co > Ni. The experimental results showed that the increase of B-s value above Slater-Pauling curve was not observed for CoFe alloys, thus FeOH and CoOH compounds were not present in deposit. However, the increase of the B-s values above the Slater-Pauling curve (B-s = 2.4-2.59 T) was observed, for CoFeNi films obtained by reverse pulse electrodeposition. Therefore, NiOH as a stable compound is probably formed in a one-electron oxidation step during anodic pulse oxidation reaction precipitated presumably at the grain boundaries, giving rise to the ultra-high magnetic saturation of CoFeNi films. The effects of experimental conditions on elemental composition, magnetic properties, crystal structure, and thermal stability of CoFeNi films were studied. (C) 2017 Elsevier B.V. All rights reserved.

Electrodeposition of NiP film used as a thin nanomagneic spacer in laminated multilayer (2.4T CoFe/NiP) (n) perpendicular writer pole for recording magnetic heads is described. The electrodeposition of laminated multilayers was carried out in a dual-bath automated electroplating tool. The thin NiP films with thickness from 2 to 5 nm were obtained as nonmagnetic amorphous NiP alloys with P-content higher than 18 at. %. The problem of composition gradient at the CoFe/NiP interface was solved by using a p-hydroxybenzhydrazide organic additive in the plating solution. The details of the electrodeposition of NiP films, the role of p-HBHy and properties of electrodeposited NiP films and CoFe/NiP multilayers are discussed. (C) The Author(s) 2016. Published by ECS. All rights reserved.

The CoPt films with 9.7-91 at% Co and thicknesses of 15-20 nm were obtained from a new designed stable hexachloroplatinate solution at a controlled potential deposition. The effects of the substrate (Ru and Cu) and an organic additive (saccharin) on composition, crystal structure and magnetic properties of the CoPt films were studied. It was demonstrated that a Ru electrode substrate provides well-defined surface for the epitaxial growth of hcp phase, resulting in high perpendicular anisotropy. The addition of saccharin (Sacc) as an organic additive into the plating solution caused a dramatic improvement of the epitaxial growth of CoPt film on the Ru substrate. At the film thickness of interest, for bit-patterned media BPM (15-20 nm), the out-of-plane coercivity showed the highest value of 6700 Oe and the squarness M-r/M-s similar to 1. (C) The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.

The composition gradients of 5–500nm thin NiFe films on Cu and NiP substrates obtained by electrodeposition in stirred plating solutions at pH 3.0 on 8 in wafers were studied. It was found that the average elemental composition of the NiFe changes during electrodeposition with steep downturns of Fe-content, from 58 to 50wt% Fe, in composition gradient zone near the substrate interface in the thickness range 5–250nm depending on the electrode substrate (Cu and NiP). The increase of Fe-content in the composition gradient zone is accompanied by the increase of coercivity, Hc, magnetic flux saturation, Bs, saturation magnetostriction, λs, increase of dimensionless roughness, ρrms, and change of stress, σ. The coercivity (easy and hard axis) follows the Neel's relation Hc=ct−n (t is thickness and c is a constant). The mechanisms related to the change of coercivity of the NiFe films deposited on different substrates (Cu and NiP) are discussed in terms of material properties of these films.

The electrodeposition of NiFe nanowires-with the length similar to 3.0 mu m and diameter 200 nm-using the porous anodized aluminum oxide (AAO) templates on the sputtered Au-back electrode (300 nm) using sulfate/chloride electrolyte solution and potential pulsed deposition. The electrode area of Au-AAO template, determined by the reversible one-electron transfer oxidation of K4Fe(CN)(6), used as a probe in CV, was found to be similar to 2.4 times larger than Au-thin film electrode. The anomalous codeposition phenomenon known as a "volcano" type curve-with a maximum in Fe-content in NiFe as a function of the applied potential-was observed in the literature. The observed results were explained through the limited mass transport of Fe+2 ions after the peak. This explanation is partially correct, but not complete. The electrodeposition of NiFe nanowire in this work resulted in a similar "volcano" type curve. The alternative explanation of anomalous codeposition-through the surface concentration of H+ dependent adsorption/desorption of FeOH+ and NiOH+ electroactive species-was proposed. The electrodeposition of NiFe nanowire arrays using a designed pulse potential method produced fcc NiFe nanowires with 5-55% Fe with controlled composition, length, and uniformity. The distinct decrease of parallel coercivity of NiFe nanowire arrays having the same length was observed with increase of Fe-content in NiFe, which also correlates with the increase of their magnetic saturation. The process of magnetization reversal in NiFe nanowires arrays was investigated. We have found two sets of magnetic behavior of NiFe nanowires depending on composition (Ni92Fe8 and Ni79Fe21 vs. Ni60Fe40, Ni56Fe44, and Ni45Fe55). (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons. org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem. org. All rights reserved.

Advanced reader technology requires high reader annealing temperature (300-450°C) to achieve good TMR ratio, to realize high density and low noise reader performance. 1) However, during the reader stack anneal, the bottom shield will also be exposed to the high temperature and possibly a cross magnetic field. Generally, the bottom shield is regular electrodeposited Permalloy Ni80Fe20 prepared from an electrodeposition solution containing saccharin additive. The significant grain growth of the NiFe bottom shield would cause deterioration of the magnetic properties as annealing temperature increases over 300°C, resulting in disordered shield domain structures and high reader noise. As one of the paths to improve the thermal stability, we have been studying and developing by using a third element to pin the grain growth caused by thermal annealing, while still keeping good magnetic softness. In this work nanocrystalline NiFeX (X=Co, Mo, O etc) films were prepared by electrodeposition, which can be stable up to 450°C. The relationship between preparation method and magnetic properties, domain structure, microstructure, crystal structure, corrosion resistance, and their thermal stability were studied. Figure 1 shows the comparison of the microstructure and domain structure of regular Permalloy and the thermally stable NiFeO after 400C 2hr annealing. Reference: 1) S. Ikeda, J. Hayakawa, Y. Ashizawa, Y. M. Lee, K. Miura, H. Hasegawa, M. Tsunoda, F. Matsukura, and H. Ohno, Appl. Phys. Lett., 93, 082508 (2008). Figure 1

A novel plating solution for CoPt alloys electrodeposition containing CoSO4 as a source of Co and H2PtCl6 as a source of Pt, has been developed. The solution was stable for more than one year. It was proposed that the most abundant six-coordinate (PtL62-)-L-IV electroactive complex in new plating solution is PtCl5(OH)(2-). The electrochemical conversion of (PtL62-)-L-IV -> (PtL42-)-L-II, occurring through two electron transfer and two ligand loss, was studied by using several electroanalytical techniques. It was concluded that the mechanism of the electron-transfer-PtL-bond-breaking process in the electrochemical reduction of (PtL62)-L-IV- complex is a function of electrode materials (Pt, Ru). On a Pt electrode the reduction through stepwise pathway occurs, while on Ru the concerted mechanism prevails. The composition of CoPt alloys is strongly dependent on potential and agitation of the solution. Electrodeposition of CoPt alloys is demonstrated at a potential positive to that required to deposit elemental Co, which is attributed to the negative enthalpy of CoPt formation. (C) 2015 The Electrochemical Society. All rights reserved.