Small-diameter magnetic and metallic nanowire arrays grown in anodic porous alumina templates anodized in selenic acid

Mahdieh Ahmadzadeh,Abdolali Ramazani,Mohammad Almasi Kashi,Mohammad Noormohammadi

doi:10.1007/s00339-021-04571-0

Abstract

Despite the introduction of selenic acid for anodic porous alumina (APA) preparation with small nanopore diameters (< 20 nm), no attempt has been made to use it in the fabrication of small-diameter magnetic and metallic nanowire arrays. In this paper, considering the high cost of selenic acid, it has been attempted to initially use oxalic acid in preparation of an ordered pattern in the first anodization step and then employ selenic acid for the second anodization step by matching the appropriate voltage. By investigating the nanopore formation pattern in both acids, it was shown that the nanopores formed in the selenic acid had considerably smaller diameter (13 nm) than that of oxalic acid (35 nm). Under optimized conditions of electrodeposition, various metals were then grown in the selenic APA templates in order to fabricate nanowires with small diameters. The pore-filling percentage and crystalline properties were also investigated.

Highlights

The fabrication method of nanostructures and nanomaterials such as nanorods, nanowires, nanotubes, and nanodots based on the template is a combination technique, employing different metals, semiconductors and oxides [1,2,3]
The templates used for the fabrication of these nanostructures include anodic porous alumina (APA) [4], porous silicon template [5], carbon nanotubes [6], polymeric membranes [7] etc., among which the APA template has been mostly used in the preparation of nanotubes and nanowires
The first anodization step of both samples has been performed in oxalic acid to form an ordered pattern on the Al substrate after dissolving the oxide layer

Summary

Introduction

The fabrication method of nanostructures and nanomaterials such as nanorods, nanowires, nanotubes, and nanodots based on the template is a combination technique, employing different metals, semiconductors and oxides [1,2,3]. APA templates are fabricated by anodizing aluminum (Al) in several acidic electrolytes so that their nanostructural characteristics can be tailored by appropriate selection of the electrolyte and anodization voltage [1214]. In this regard, three electrolyte types have been used for anodizing Al under various applied voltages, resulting in the following self-ordered APAs: sulfuric acid (19–27 V), oxalic acid (40 V), and phosphoric acid (160–195 V). The aforementioned anodization electrolytes have been employed for the surface finishing of Al and its alloy compounds, enhancing their chemical and physical properties [15] while being used for self-ordered fabrication of APAs [16]

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