Metallic nanoparticle composites electrodeposition

Figure 16.2.5 Electrochemical template deposition of metals (A) scheme of the electrochemical cell and (B) sequence of the growth of the template for the preparation of single metal continuous nanowires (sequences 1-4) or segmented nanoparticles (sequences 1, 2, 5, and 6). Detailed steps (1) metal sputtering to provide a conductive layer for the subsequent electrodeposition (2) electrodeposition of the same metal to form the fibers (3) growth of the fibers (4) etching of the template (5) electrodeposition of another metal (6) composite structure after the etching of the foundation metal. Part (B) redrawn with permission from reference (25).

The above studies suggest that electrochemical deposition provides a versatile, yet simple route for immobilizing proteins, enzymes, and bacteria in silane sol-gel films. The biological species remained active in the electrodeposited composite films, allowing their applications for biosensing. More sophisticated films with redox mediators, metal nanoparticles, and CNTs have also been constructed via the sol-gel co-electrodeposition approach. 

The LBL deposition of polymer layers incorporating metal nanoparticles was employed to study the electrochemical properties of the resultant composite films by using SECM. Wittstock and coworkers electrodeposited Pd and Pt nanoparticles in the matrix of LBL-deposited multilayers of polyelectrolytes, that is, polyfdiallyldimethylammonium) and poly(4-stylene sulfonate). The production of hydrogen peroxide during the ORR at the nanoparticle-incorporated LBL films was monitored in the SG/TC mode. The transient current at a 25 pm diameter Pt SECM tip was measured at various tip-substrate distances and quantitatively analyzed to determine effective rate constants 2, and k, for the following reactions at the film ... 

Sol-gel materials are also known as an excellent matrix for embedding other species due to their tunable physical properties (e.g., flexibility and transparency), high chemical stability, and mild operating conditions. Especially, electrochemical deposition of silane-based sol-gel Aims is usually carried out under mild acidic aqueous solutions at pH 3-6. This allows the co-electrodeposition of silane with nanoparticles [47-50], carbon nanotubes [51-53], metals [54-57], polymers [50,58], enzymes [52,53,59-65], bacteria [66,67], and more. Thus, most of the recent research worlcs also focus on the electrochemical deposition of sol-gel-based composite Aims, with the concern of improving the films performance in corrosion protection, electroanalysis, microextraction, and so on and further broadening the films applications. 

The electrodeposition process can also be combined with an AAO template for the fabrication of a metal-embedded hollow nanotube structure, that is, Ni-embedded silica nanotubes, as demonstrated by Xu et al. [79]. The fabrication starts with the electrodeposition of multiple segments of Ag/Ni/Ag (3 pm/3 pm/ 3 pm) nanowires with a diameter of 300 nm on nanoporous AAO templates (Figure 13.7d). Subsequently, a hydrolysis reaction of tetraethyl orthosiUcate was performed for 2-5 h to coat a 70 nm thick silica layer. Then, Ag was selectively etched in a mixture (4 1 1) of methanol, hydrogen peroxide, and ammonia hydroxide to produce a hollow structure. Finally, Ag nanoparticles were functionalized on the surface by the reduction of Ag ions at 70 °C for 7 h in a composite solution of PVP (2.5xlO M in ethanol), silver nitrate (0.06 M), and ammonia hydroxide (0.12 M). The synthesized silica nanotubes exhibited a Ni-embedded hollow structure with Ag nanoparticles functionalized on the surface... 

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