Electroless Metal Deposition Method Research Articles

The Dependence of NiMo/Cu Catalyst Composition on Its Catalytic Activity in Sodium Borohydride Hydrolysis Reactions.

The production of high-purity hydrogen from hydrogen storage materials with further direct use of generated hydrogen in fuel cells is still a relevant research field. For this purpose, nickel-molybdenum-plated copper catalysts (NiMo/Cu), comprising between 1 and 20 wt.% molybdenum, as catalytic materials for hydrogen generation, were prepared using a low-cost, straightforward electroless metal deposition method by using citrate plating baths containing Ni2+-Mo6+ ions as a metal source and morpholine borane as a reducing agent. The catalytic activity of the prepared NiMo/Cu catalysts toward alkaline sodium borohydride (NaBH4) hydrolysis increased with the increase in the content of molybdenum present in the catalysts. The hydrogen generation rate of 6.48 L min-1 gcat-1 was achieved by employing NiMo/Cu comprising 20 wt.% at a temperature of 343 K and a calculated activation energy of 60.49 kJ mol-1 with remarkable stability, retaining 94% of its initial catalytic activity for NaBH4 hydrolysis following the completion of the fifth cycle. The synergetic effect between nickel and molybdenum, in addition to the formation of solid-state solutions between metals, promoted the hydrogen generation reaction.

Non-Precious Metals Catalysts for Hydrogen Generation

In this paper, the generation of hydrogen from alkaline sodium borohydride solution by hydrolysis is studied. To obtain catalysts for efficient hydrogen generation, Ni, Mn, Mo, and Co metals were deposited on the Cu surface by the simple electroless metal deposition method using morpholine borane as a reducing agent. Depending on the peculiarities of the deposition of each metal, the coating thickness was ca. 1 μm for all catalysts. The deposited coatings were compact and crack-free, with multilayer characteristics and a cauliflower-like structure. The prepared Ni/Cu, NiMn/Cu, NiMo/Cu, NiCo/Cu, NiCoMn/Cu, NiCoMo/Cu, and NiCoMoMn/Cu catalysts showed an efficient catalytic activity for sodium borohydride hydrolysis reaction. The lowest activation energy of 45.3 kJ mol−1 for sodium borohydride hydrolysis reaction was obtained using the NiCoMoMn/Cu catalyst. The highest hydrogen generation rate of 3.08 mL min−1 was also achieved using this catalyst at 303 K. With a further increase in temperature to 343 K, the hydrogen generation rate catalyzed by the NiCoMoMn/Cu increased 7.7 times and reached 23.57 mL min−1.

Selective catalytic reduction of NO by NH3 using Mn-based catalysts supported by Ukrainian clinoptiolite and lightweight expanded clay aggregate

ABSTRACT In this study, Mn-based multicomponent catalysts supported by two different carriers (lightweight expanded clay aggregate and the Ukrainian clinoptiolite) were prepared by electroless metal deposition method and tested for the selective catalytic reduction of NO with ammonia (NH3-SCR de-NO). Prior to the activity test, all the catalysts prepared were characterized by inductively coupled plasma optical emission spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray mapping, X-ray photoelectron spectroscopy, H2-TPR and NH3-TPD techniques. The particular interest of the present study was focused on the investigation of the carrier’s role in the NO catalytic reduction and the promoting effect provided by the incorporation of the small amount of Pt (0.1 wt.%) in the Mn-based catalytic layer. The results revealed that the carrier’s role in the NO catalytic conversion can be considered as a factor determining the effectiveness of the conversion process. Ukrainian clinoptiolite was proved to be a more attractive carrier for the preparation of the effective SCR de-NO catalysts due to its intrinsic sorption capacity, surface acidity and the redox potential. The high NO conversion efficiency provided by the Mn-based clinoptiolite-supported catalysts can be explained by the synergistic effect between the carrier and the active species deposited. It was shown that both the Mn97.6Cu2.4/clinoptiolite and the Mn97.5Co2.5/clinoptiolite catalysts can be successfully applied as the low-temperature (100–300°C) catalysts for NH3-SCR de-NO. When the NO removal efficiency varies in the range of 86–91%, the additional incorporation of Pt in the active layer in the amount of 0.1 wt.% can enhance the NO reduction by about 5% on average.

Hydrogen Generation from an Alkaline NaBH4 Solution Using Different Cobalt Catalysts

The effective Co, CoB and CoBM, where M = Mo, Zn, and Fe, catalysts have been deposited on the Cu surface by a simple electroless metal deposition method using morpholine borane as a reducing agent and used as catalysts for hydrogen generation from an alkaline NaBH4 solution. The catalytic activity of different cobalt alloys catalysts towards the hydrolysis of NaBH4 has been investigated by measuring the amount of generated hydrogen from an alkaline solution contained 5 wt. % NaBH4 and 0.4 wt. % NaOH. The rate of H2 generation has been measured at solution temperatures in the range from 298 to 318 K in order to determine the activation energy.It has been determined that the synthesized Co/Cu, CoB/Cu and CoBM (M=Mo,Zn,Fe)/Cu catalysts demonstrate the catalytic activity for the hydrolysis reaction of NaBH4. The lowest obtained activation energy of the hydrolysis reaction of NaBH4 has been 27 kJ mol-1 for the CoBMo/Cu catalyst. The hydrogen generation rate has been achieved 15.30 ml min-1 using the CoBMo/Cu catalyst at a temperature of 313 K and it increases ~3.5 times with the increase of temperature to 343 K. Moreover, the CoBMo/Cu catalyst shows a highest catalytic activity for hydrogen generation from the alkaline NaBH4 solution as compared with that for other Co/Cu, CoB/Cu, CoBZn/Cu, and CoBFe/Cu catalysts.

Electrosorptive disinfection of Escherichia coli (E. coli) aqueous solutions by activated carbon monolith electrodes

Abstract Electrosorption, which can be defined as adsorption onto the surfaces of charged electrodes, has been developing as an efficient and environmentally friendly technology for removing toxic pollutants from aqueous solutions. In this study, an industrial process was used for the fabrication of activated carbon electrodes (ACEs). An electroless metal deposition method was used for the modification of activated carbon granules with silver (Ag) for antibacterial activity of electrodes. The antibacterial activity of Ag-modified–ACEs (Ag–ACEs) for Escherichia coli (E. coli) bacteria commonly found in water was tested. Adsorption and electrosorption behaviors of E. coli aqueous solutions onto ACEs and Ag–ACEs were examined in a cyclic electrosorption system. It has been concluded that the performance of Ag–ACEs is better than ACEs as an electrode for electrosorption of E. coli. Moreover polarization can significantly enhance the removal efficiency of E. coli on both ACEs and Ag–ACEs. Finally, electrosorption capacity of the system for E. coli was determined.

Flue gas purification from NO using supported Cu–Mn and Cu–Mn–Nb catalysts synthesized by electroless metal deposition method

In the present work, granular fixed-bed catalysts with active Cu–Mn and Cu–Mn–Nb layers synthesized by electroless metal deposition method were prepared and tested for purification of a flue gas from nitrogen monoxide (NO) by CO. Lightweight expanded clay aggregate with i.d. of 2–4 mm and 8–10 mm was used as a substrate for deposition of the active layer. Elemental composition of the prepared catalytic layers was determined by means of inductively coupled plasma optical emission spectroscopy and energy-dispersive X-ray analysis. Field emission scanning electron microscopy and X-ray photoelectron spectroscopy were applied to investigate morphology of the active layers and the oxidation state of the main components (Mn, Cu and Nb), respectively. Additionally, X-ray diffraction analysis and energy-dispersive X-ray mapping were conducted to provide comprehensive information about the structure and dispersion of active components on the surface of the catalysts prepared. It was demonstrated that electroless metal deposition method allows preparation of a relatively uniform active layer with highly distributed active sites on the substrate surface, while the Cu0.012–Mn0.986Nb0.0012 active layer synthesized by electroless metal deposition can be successfully applied for selective catalytic reduction of NO with the use of CO as a reductant. The effective NO conversion (90–95%) was observed at temperatures of 300–400 °C and higher. X-ray photoelectron spectroscopy revealed that significant amount of Mn3+ and Mn4+ species and predominance of chemisorbed oxygen over the lattice oxygen should be responsible for NO conversion efficiency of the catalyst prepared.

Development of Metal-Enhanced Fluorescence-Based Aptasensor for Thrombin Detection Using Silver Dendritic Nanostructures

Metal-enhanced fluorescence (MEF) phenomenon has shown a promising potential in the field of fluorescence-based biological sensing. In this study, we optimized the electroless metal deposition method to fabricate silver dendritic nanostructures as effective MEF active substrates. Then, an aptasensor was developed for thrombin detection using the established surfaces. For this purpose, thiolated 29-mer thrombin-binding aptamers (TBA29 (12T) SH) as capturing aptamer were immobilized on the surface of silver dendritic nanostructures, then thrombin was sandwiched between the capturing aptamer and Cy5-labeled 15-mer thrombin aptamer (TBA15-Cy5). Quantitative analysis was performed through fluorescence signal measurement. The established aptasensor presented satisfactory sensitivity and selectivity and exhibited a limit of detection (LOD) as low as 32 pM. This aptasensor was also able to detect thrombin in the human serum at picomolar levels. Furthermore, the ease and relatively low-cost of fabrication of this platform introduce it as a tool with great potential for the clinical diagnosis of diseases and also for improving sensitivity of a variety of technologies which exploit fluorescent dyes for analyte detection, at ultra-trace levels, in complex matrices.

A coaxial structure of multiwall carbon nanotubes on vertically aligned Si nanorods and its intrinsic characteristics

We present a unique process for fabricating silicon nanorods wrapped with a graphitic material on a silicon substrate by the chemical vapor deposition method with no metal catalyst, as well as characterization of their intrinsic properties. First, well-ordered silicon nanorod axes were grown via an electroless metal deposition method, followed by chemical vapor deposition to wrap the axes with a carbon nanotube. Interestingly, the use of ethanol treatment before chemical vapor deposition prevents the formation of SiOx layers, which may be necessary as seed layers for carbon nanotube growth. Since this method for carbon nanotube growth does not involve a metal catalyst, the intrinsic properties of the Si NRs were well characterized. A few characterization methods (XPS, Raman spectroscopy, and EELS) were carried out to prove that the Si NRs were completely surrounded by CNTs. In addition, the conductance results (by terahertz time-domain spectroscopy) show that the charge carrier transport characteristics of the multiwall carbon nanotubes are found mainly in the outermost shell, and that the Si NR surface was well passivated by the multiwall carbon nanotube structure. This coaxial structure, which does not require a metal catalyst, represents a significant step forward for realizing applications for carbon nanotube devices.

Magnetic metal nanoparticles coated polyacrylonitrile textiles as microwave absorber

Polyacrylonitrile (PAN) textiles with 2mm thickness are coated with magnetic nanoparticles in coating baths with Ni, Co and their alloys via an electroless metal deposition method. The crystal structure, morphology and magnetic nature of composites are investigated by X-ray Powder diffraction, Scanning Electron Microscopy, and dc magnetization measurement techniques. The frequency dependent microwave absorption measurements have been carried out in the frequency range of 12.4–18GHz (X and P bands). Diamagnetic and ferromagnetic properties are also investigated. Finally, the microwave absorption of composites is found strongly dependent on the coating time. One absorption peak is observed between 14.3 and 15.8GHz with an efficient absorption bandwidth of 3.3–4.1GHz (under −20dB reflection loss limit). The Reflection loss (RL) can be achieved between −30 and −50dB. It was found that the RL is decreasing and absorption bandwidth is decreasing with increasing coating time. While absorption peak moves to lower frequencies in Ni coated PAN textile, it goes higher frequencies in Co coated ones. The Ni–Co alloy coated composites have fluctuating curve of absorption frequency with respect to coating time. These results encourage further development of magnetic nanoparticle coated textile absorbers for broadband applications.

Coaxial-structured ZnO/silicon nanowires extended-gate field-effect transistor as pH sensor

An extended-gate field-effect transistor (EGFET) of coaxial-structured ZnO/silicon nanowires as pH sensor was demonstrated in this paper. The oriented 1-μm-long silicon nanowires with the diameter of about 50nm were vertically synthesized by the electroless metal deposition method at room temperature and were sequentially capped with the ZnO films using atomic layer deposition at 50°C. The transfer characteristics (IDS–VREF) of such ZnO/silicon nanowire EGFET sensor exhibited the sensitivity and linearity of 46.25mV/pH and 0.9902, respectively for the different pH solutions (pH 1–pH 13). In contrast to the ZnO thin-film ones, the ZnO/silicon nanowire EGFET sensor achieved much better sensitivity and superior linearity. It was attributed to a high surface-to-volume ratio of the nanowire structures, reflecting a larger effective sensing area. The output voltage and time characteristics were also measured to indicate good reliability and durability for the ZnO/silicon nanowires sensor. Furthermore, the hysteresis was 9.74mV after the solution was changed as pH 7→pH 3→pH 7→pH 11→pH 7.

Electron Field Emission Properties of Nanomaterials on Rough Silicon Rods

Highly porous, individually separated, and vertically aligned rough silicon rods (r-SiRs) were formed via a modified electroless metal deposition (EMD) approach. Despite inheriting the length of crowded silicon nanowires (NWs) obtained by the conventionally adopted EMD method, the r-SiRs are distributed sparsely, subsequently forming an excellent field emitter substrate. The electron field emission (EFE) of carbon nanotubes (CNTs) grown on r-SiRs can be turned on at (E0)CNTs/r-SiRs = 2.3 V/μm, yielding a high EFE current density, (Je)CNTs/r-SiR = 3.7 mA/cm2 in an applied field of 5.1 V/μm. Additionally, a cactuslike structure consisting of zinc oxide NWs on r-SiRs can be turned on at 2.9 V/μm. The absence of a high-temperature or expensive photolithographic process makes r-SiRs a promising alternative as a silicon base field emitter substrate.

Deep ultraviolet and near infrared photodiode based on n-ZnO/p-silicon nanowire heterojunction fabricated at low temperature

n -ZnO / p -silicon nanowire (SiNW) photodiodes were prepared by radio frequency reactive magnetron sputtering of n-type zinc oxide at room temperature on photoresist filled p-SiNWs, which were fabricated by electroless metal deposition method at 323 K. Our n-ZnO/p-SiNW photodiodes showed good temperature- and light-intensity dependence. They exhibited strong responsivities of 19.2 and 2.5 A/W for 254 and 1000 nm photons, respectively, under a reverse bias of 2 V with a strong peak of responsivity near 390 nm, the wavelength corresponding to the band gap of ZnO. These results present potential applications of n-ZnO/p-SiNW photodetectors in deep ultraviolet and near infrared regions.

Fabrication and electrical and photosensitive properties of silicon nanowire p–n homojunctions

AbstractGraded silicon nanowire (SiNW) p–n homojunctions were prepared by an electroless metal deposition method on as‐prepared planar Si p–n junctions made by the B+ diffusion method. The nanowire p–n junctions show good rectifying behavior and their turn‐on voltages (0.78 V at room temperature) are found to be independent of the nanowire length. Temperature‐dependent current–voltage properties in the range of 223–363 K were investigated and we demonstrated that the turn‐on voltage decreases from 0.87 V to 0.60 V and the ideality factor n reduces from 8.5 to 3.5 with increasing operating temperature. The results comply very well with the existing p–n junction electron transport mechanism. The potential barrier of a typical SiNW p–n junction obtained through capacitance–voltage measurement accords with its turn‐on voltage. Through I –V and C –V measurements, the nanowire homojunction shows good sensitivity toward visible light and a responsivity of 1.39 A/W under a 5 V reverse bias was obtained. These results present potential applications in future nano‐electronic and photonic devices based on SiNW p–n homojunction arrays. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Selective hydrogenation of citral over a novel platinum/MWNTs nanocomposites

Pt was introduced into pure and polyacrylic acid (PAA) grafting multi-walled carbon nanotubes (MWNTs) by electroless metal deposition method and used as catalysts for hydrogenation of citral. The catalysts exhibited higher activity in the hydrogenation of citral when compared with Pt impregnated active carbon (AC) catalyst, while the selectivity of the catalysts on different MWNTs supports were quite different. The catalyst characterization results reveal that the selectivity of products is related with the morphology of the MWNTs and Pt(1 1 1) facet, functionalized carbon nanotubes will orient Pt facet and facilitate its dispersion on support.

Ag microparticles embedded in Si nanowire arrays: a novel catalyst for gas-phase oxidation of high alcohol to aldehyde

A novel catalyst of silver microparticles embedded in a silicon nanowire array support (Ag@SiNW) was prepared by an in situ electroless metal deposition method; it exhibited high selectivity and stability for gas-phase oxidation of high alcohol to its corresponding aldehyde.

Fabrication and electrical, photosensitive properties of p-poly(9,9-diethylfluorene)/n-silicon nanowire heterojunction

P -poly(9, 9-diethylfluorene)/n-silicon nanowire (SiNW) heterojunctions were prepared by spin coating p-type conductive organic polymer on as-prepared n-SiNWs, which were fabricated by electroless metal deposition method. This hybrid nanowire p-n heterojunction shows good rectifying behavior with turn-on voltage of about 1V at room temperature. Temperature-dependent current-voltage properties in the range of 253–413K were investigated and they follow the standard p-n heterojunction electron transport mechanism. The hybrid nanowire heterojunction shows good photovoltaic properties and good sensitivity toward visible light, and a responsivity of 3.23mA∕W under a reverse bias of 10V was obtained. These results present potential applications in the future nanoelectronic and photonic devices based on organic and inorganic p-n heterojunction arrays.

Copper patterned polystyrene panels by reducing of surface bound Cu (II)-sulfonyl hydrazide complex

A modified electroless metal deposition method has been developed for copper plating of polystyrene (PS) surfaces. The modified procedure avoids the plasma conditioning and surface activation steps in the classical electroless metal plating process. First step of the present procedure is chlorosulfonation of PS surface by soaking into chlorosulfonic acid, yielding chlorosulfonated surface with density of 0.046–0.110 mmolcm − 2 depending on contact time (10–60 min). In the second step chlorosulfone groups on the surface are converted to sulfonyl hydrazides almost quantitatively by reaction with hydrazine solution (80%). Green Cu (II)-sulfonylhydrazide complex is formed at the surface, in the third step, by interaction with ammoniacle Cu (II) solution at room temperature. The copper in the complex is reduced rapidly in the fourth step, by immersing the specimen into 5% of hydrazine solution. The elemental copper deposited onto the surface serves activating sites to accumulate more (5–7 mg per cm 2) elemental copper from electroless copper solutions in the final step. The present method avoids the surface activation with palladium and allows preparing copper patterns with reasonably high pull-off strengths (3.77 Nmm − 2 ) on PS panels. In the study the copper deposition has been investigated using standard analytical procedures, X-ray photoelectron spectrometry (XPS) and Scanning Electron Microscopy.

Self-organized synthesis of silver dendritic nanostructures via an electroless metal deposition method

Unique silver dendritic nanostructures, with stems, branches, and leaves, were synthesized with self-organization via a simple electroless metal deposition method in a conventional autoclave containing aqueous HF and AgNO3 solution. Their growth mechanisms are discussed in detail on the basis of a self-assembled localized microscopic electrochemical cell model. A process of diffusion-limited aggregation is suggested for the formation of the silver dendritic nanostructures. This nanostructured material is of great potential to be building blocks for assembling mini-functional devices of the next generation.