Progress in Nanoporous Templates: Beyond Anodic Aluminum Oxide and Towards Functional Complex Materials

Successful synthesis of ordered porous, multi-component complex materials requires a series of coordinated processes, typically including fabrication of a master template, deposition of materials within the pores to form a negative structure, and a third deposition or etching process to create the final, functional template. Translating the utility and the simplicity of the ordered nanoporous geometry of binary oxide templates to those comprising complex functional oxides used in energy, electronic, and biology applications has been met with numerous critical challenges. This review surveys the current state of commonly used complex material nanoporous template synthesis techniques derived from the base anodic aluminum oxide (AAO) geometry

A review on one dimensional perovskite nanocrystals for piezoelectric applications

AbstractIn recent years, one-dimensional piezoelectric nanomaterials have become a research topic of interest because of their special morphology and excellent piezoelectric properties. This article presents a short review on one dimensional perovskite piezoelectric materials in different systems including Pb(Zr,Ti)O3, BaTiO3 and (K,Na)NbO3 (KNN). We emphasize KNN as a promising lead-free piezoelectric compound with a high Curie temperature and high piezoelectric properties and describe its synthesis and characterization. In particular, details are presented for nanoscale piezoelectricity characterization of a single KNN nanocrystal by piezoresponse force microscopy. Finally, this review describes recent progress in applications based on one dimensional piezoelectric nanostructures with a focus on energy harvesting composite materials

High-Efficiency Electrodeposition of Large Scale ZnO Nanorod Arrays for Thin Transparent Electrodes

In the present work an effective technique to synthesize large-scale c-axis oriented ZnO nanorod (NR) arrays is presented. The manuscript reports a single-step cathodic electrodeposition, either in aqueous and organic electrolytes, to fill up ultra-thin anodic nanoporous alumina templates. Prior to growing, self-ordered hexagonal array of cylindrical nanopores have been fabricated by anodizing Al thin films previously deposited onto ITOglass substrates. The diameter and the aspect ratio of the vertically aligned nanopores are about 60 nm and 8:1, respectively. The results of this work demonstrate that using dimethyl sulfoxide (DMSO) as an electrolyte leads to a growth more homogeneous in shape and crystallinity, and with 60 deposition efficiency - the highest by now in literature. This fact is most probably due to a better infiltration of the alumina nanopores by this electrolyte. SEM and XRD analysis were employed for the study of morphology and crystalline structure of the obtained ZnO NR. These measurements showed furthermore that ZnO nanorod arrays are uniformly embedded into the hexagonally ordered nanopores of the anodic alumina membrane. DMSO proved to be an optimal electrolyte to obtain single-crystalline ZnO NR arrays, highly transparent in visible light range (80 transmittance). © 2011 The Electrochemical Society.The authors thank for the financial support by the European Commission, DG Research through the program PEOPLE, by the project no. MRTN-CT-2006-035884.Pullini, D.; Pruna, AI.; Zanin, S.; Busquets Mataix, DJ. (2012). High-Efficiency Electrodeposition of Large Scale ZnO Nanorod Arrays for Thin Transparent Electrodes. Journal of The Electrochemical Society. 159(2):45-51. doi:10.1149/2.093202jesS4551159

Tube Formation in Nanoscale Materials

The formation of tubular nanostructures normally requires layered, anisotropic, or pseudo-layered crystal structures, while inorganic compounds typically do not possess such structures, inorganic nanotubes thus have been a hot topic in the past decade. In this article, we review recent research activities on nanotubes fabrication and focus on three novel synthetic strategies for generating nanotubes from inorganic materials that do not have a layered structure. Specifically, thermal oxidation method based on gas–solid reaction to porous CuO nanotubes has been successfully established, semiconductor ZnS and Nb2O5nanotubes have been prepared by employing sacrificial template strategy based on liquid–solid reaction, and an in situ template method has been developed for the preparation of ZnO taper tubes through a chemical etching reaction. We have described the nanotube formation processes and illustrated the detailed key factors during their growth. The proposed mechanisms are presented for nanotube fabrication and the important pioneering studies are discussed on the rational design and fabrication of functional materials with tubular structures. It is the intention of this contribution to provide a brief account of these research activities

Recent advances in multistep solution nanosynthesis of nanostructured three-dimensional complexes of semiconductive materials

AbstractConstructing simply nanostructured zero-, one-, and two-dimensional crystallites into three-dimensional multifunctional assemblies and systems at low-cost is essential and highly challenging in materials science and engineering. Compared to the simply nanostructured components, a three-dimensional (3D) complex made with a precisely controlled spatial organization of all structural nanocomponents can enable us to concert functionalities from all the nanocomponents. Methodologically, so doing in nm-scales via a solution chemistry route may be much easier and less expensive than via other mechanisms. Hence, we discuss herein some recent advances in multistep solution syntheses of nanostructured 3D complexes of semiconductors with a focus mainly on their synthetic strategies and detailed mechanisms

Three-dimensional nanotube arrays for solar energy harvesting and production of solar fuels

Over the past decade extensive research has been carried out on photovoltaic semiconductors to provide a solution towards a renewable energy future. Fabricating high-efficiency photovoltaic devices largely rely on nanostructuring the photoabsorber layers due to the ability of improving photoabsorption, photocurrent generation and transport in nanometer scale. Vertically aligned, highly uniform nanorods and nanowire arrays for solar energy conversion have been explored as potential candidates for solar energy conversion and solar-fuel generation owing to their enhanced photoconversion efficiencies. However, controlled fabrication of nanorod and especially nanotube arrays with uniform size and shape and a pre-determined distribution density is still a significant challenge. In this research work, we demonstrate how to address this issue by fabricating nanotube arrays by confined electrodeposition on lithographically patterned nanoelectrodes defined through electron beam as well as nanosphere photolithography. This simple technique can lay a strong foundation for the study of novel photovoltaic devices because successful fabrication of these devices will enhance the ability to control structure-property relationships. The nanotube patterns fabricated by this method could produce an equivalent amount of photocurrent density produced by a thin film like device while having less than 10% of semiconducting material coverage. This project also focused on solar fuel generation through photoelectrocatalytic water splitting for which efficient electrocatalysts were developed from non-precious elements. Lastly, a protocol was developed to disperse these electrocatalysts into a butadiene based polymeric catalytic ink and further processing to yield free-standing catalytic film applicable for water electrolysis”--Abstract, page iv

Fabrication of ZnO Nanorod-Based Hydrogen Gas Nanosensor

The nanofabrication of a hydrogen nanosensor from single ZnO branched nanorods using in-situ lift-out technique, performed in the chamber of a focused ion beam (FIB) system is disclosed. A self-assembled ZnO branched nanorod has been grown by a cost-effective and fast synthesis route using an aqueous solution deposition method and rapid thermal processing. The properties of the ZnO nanorod structures were analyzed by X-ray difhction, scanning electron microscopy, energy dispersion X-ray spectroscopy, transmission electron microscopy and micro-Raman spectroscopy. High quality ZnO nanorods were obtained with a 90% success rate for building nanodevices. The fabricated nanosensor can gauge 150 ppm hydrogen gas in the air at room temperature. The nanosensor has selectivity for other gases such as oxygen, methane, carbon monoxide and liquid propane gas. The single ZnO branched nanorod sensor also operates at low power of less than 5 microwatts

Nanowired electrodes as outer membrane cytochrome-independent electronic conduit in Shewanella oneidensis

Extracellular electron transfer (EET) from microorganisms to inorganic electrodes is a unique ability of electrochemically active bacteria. Despite rigorous genetic and biochemical screening of the c-type cytochromes that make up the EET network, the individual electron transfer steps over the cell membrane remain mostly unresolved. As such, attempts to transplant entire EET chains from native into non-native exoelectrogens have resulted in inferior electron transfer rates. In this study we investigate how nanostructured electrodes can interface with Shewanella oneidensis to establish an alternative EET pathway. Improved biocompatibility was observed for densely packed nanostructured surfaces with a low cell-nanowire load distribution during applied external forces. External gravitational forces were needed to establish a bioelectrochemical cell-nanorod interface. Bioelectrochemical analysis showed evidence of nanorod penetration beyond the outer cell membrane of a deletion mutant lacking all outer membrane cytochrome encoding genes that was only electroactive on a nanostructured surface and under external force