preparation-use-photocatalytically-active-segmented-agzno-coaxial

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO<sub>2</sub>-Ag Nanowires Made by Templated Electrodeposition

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and ...

University of Twente

A cost-effective and versatile methodology for bottom-up patterned growth of inorganic and metallic materials on the micro- and nanoscale is presented. Pulsed electrodeposition was employed to deposit arbitrary patterns of Ni, ZnO, and FeO(OH) of high quality, with lateral feature sizes down to 200-290 nm. The pattern was defined by an oxygen plasma-treated patterned PDMS mold in conformal contact with a conducting substrate and immersed in an electrolyte solution, so that the solid phases were deposited from the solution in the channels of the patterned mold. It is important that the distance between the entrance of the channels, and the location where deposition is needed, is kept limited. The as-formed patterns were characterized by high resolution scanning electron microscope, energy-dispersive X-ray analysis, atomic force microscopy, and X-ray diffraction.

Electrodeposition in capillaries: bottom-up micro- and nanopatterning of functional materials on conductive substrates.

Hydrogen generation from photocatalytic silver|zinc oxide nanowires: towards multifunctional multisegmented nanowire devices.

A simple and cost-effective methodology for large-area micrometer-scale patterning of a wide range of metallic and oxidic functional materials is presented. Self-assembled monolayers (SAM) of alkyl thiols on Au were micropatterned by channel-diffused oxygen plasma etching, a method in which selected areas of SAM were protected from plasma oxidation via a soft lithographic stamp. The patterned SAMs were used as templates for site-selective electrodeposition, electroless deposition and solution-phase deposition of functional materials such as ZnO, Ni, Ag thin films, and ZnO nanowires. The patterned SAMs and functional materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and tunneling AFM (TUNA).

Patterning functional materials using channel diffused plasma-etched self-assembled monolayer templates.

We present a general methodology to pattern functional materials on the nanometer scale using self-assembled molecular templates on conducting substrates. A soft lithographic gas phase edge patterning process using poly(dimethylsiloxane) molds was employed to form electrically isolating organosilane patterns of a few nanometer thickness and a line width that could be tuned by varying the time of deposition. Electrodeposition was employed to deposit patterns of Ni and ZnO on these prepatterned substrates. Deposition occurred only on patches of the substrate where no organosilane monolayer was present. The process is simple, inexpensive, and scalable to large areas. We achieved formation of metallic and oxide material patterns with a lateral resolution of 80 nm.

Nanopatterning of functional materials by gas phase pattern deposition of self-assembled molecular thin films in combination with electrodeposition.

A method for the reproducible formation of Ni and Cu2O nanocubes with dimensions of 200-500 nm and a small size distribution is introduced. For this, the well-known templated electrodeposition technique was extended to cubic PMMA templates made by nanoimprint lithography. When making cubic templates in larger quantities, this method has the potential to become simple and cost-effective. This method was successfully used for the formation of Ni and p-Cu2O nanocubes as well as for the formation of segmented nanobars containing both phases. The lateral dimensions of the nanocubes exactly resembled the dimensions of the template, and the height could be varied by adjusting the deposition time. Nanocubes formed via this method can remain attached to the substrate or can be dispersed in solution. p-Cu2O is considered to be one of the most promising photocathode materials for solar water splitting. It is demonstrated that the activity of the p-Cu2O nanocubes for photocatalytic water splitting can be measured, and it was found that the nanocube morphology enhances the photocatalytic activity compared to thin films.

Ni and p-Cu2O nanocubes with a small size distribution by templated electrodeposition and their characterization by photocurrent measurement.

Core-shell PMMA-Au nanocube structures made by a combination of nanoimprint lithography and sidewall deposition were used as template for electrodeposition of MoS2, Ni, and Pt. Linear sweep voltammetry experiments obtained in an aqueous solution containing 0.29 M H2SO4 (pH 0.24) showed that the onset potential of the core-shell-shell PMMA-Au-MoS2 nanocube electrode for the hydrogen evolution reaction (HER) was shifted to the positive direction (i.e., requiring a lower overpotential) by 20-40 mV compared to planar MoS2 films. This indicates that the nanocube electrodes have a significantly increased HER activity, which is probably because of a higher density of catalytically active edge sites available at the nanocube surface. It was also found that the HER activity initially increased with increasing MoS2 deposition time, but decreased after deposition for 60 min because the edges of the nanocubes became rounded, thereby decreasing the number of active edge sites. By depositing Ni and Pt on top of PMMA-Au nanocubes, it was shown that this method can also be used for the synthesis of nanocube structures with varying compositions.

Article	Year
Electrodeposition in capillaries: bottom-up micro- and nanopatterning of functional materials on conductive substrates. ACS applied materials & interfaces\| PubMed ID: 21838239	2011
Hydrogen generation from photocatalytic silver\|zinc oxide nanowires: towards multifunctional multisegmented nanowire devices. Small (Weinheim an der Bergstrasse, Germany)\| PubMed ID: 21842477	2011
Patterning functional materials using channel diffused plasma-etched self-assembled monolayer templates. Langmuir : the ACS journal of surfaces and colloids\| PubMed ID: 21859121	2011
Nanopatterning of functional materials by gas phase pattern deposition of self-assembled molecular thin films in combination with electrodeposition. Langmuir : the ACS journal of surfaces and colloids\| PubMed ID: 21875090	2011
Ni and p-Cu2O nanocubes with a small size distribution by templated electrodeposition and their characterization by photocurrent measurement. ACS applied materials & interfaces\| PubMed ID: 24083805	2013
MoS₂ nanocube structures as catalysts for electrochemical H₂ evolution from acidic aqueous solutions. ACS applied materials & interfaces\| PubMed ID: 24444817	2014

A. Wouter Maijenburg

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