Pulsed electrodeposition and unique properties of one-dimensional Bi-based nanostructures in porous alumina membranes

Abstract

One-dimensional (1D) Bi-based nanostructures are promising thermoelectric materials and, furthermore, are very interesting systems for studying physical and chemical properties in the nanoscale, owing to their anisotropic character. The main challenges in this area are to control the diameter, orientation, and alloy composition with precision, and thereby to gain ready access to junction and superlattice structures. Here, we review our recent contributions toward advances in pulsed electrodeposition-based routes to fabricate Bibased nanostructures. As a main theme, porous anodic alumina membranes (AAMs) have been employed as effective templates to fabricate Bi elementary, alloy, junction, and superlattice structures, and unique properties are demonstrated.The maximum efficiency of a thermoelectric material is determined by its dimensionless figure of merit (ZT): ZT = S 2 σT/κ, where S, σ, T, and κ are, respectively, the Seebeck coefficient, electrical conductivity, temperature, and thermal conductivity. The quantities S, σ, and κ for conventional threedimensional (3D) crystalline systems are interrelated, so it is very difficult to control these variables independently to increase ZT, which is due to the fact that conventional 3D crystalline systems follow the Wiedemann−Franz law that an increase in S usually results in a decrease in σ and produces a decrease in the electronic contribution to κ. In the 1990s, theoretical predictions suggested that the thermo electric efficiency could be greatly enhanced in one-dimensional (1D) and two-dimensional (2D) systems compared to the bulk materials, owing to both a sharper density of states in low-dimensional systems for enhanced thermopower (S 2 σ) and an increased phonon scattering for reduced lattice thermal conductivity (κ). Recent experiments further showed that heterostructures and superlattices may result in higher ZT, because heterogeneous interfaces can reduce lattice thermal conductivity by increasing phonon scattering at segment interfaces. The thermopower can be enhanced owing to sharper density of states than 1D homogeneous nanowires.Bismuth (Bi), with a rhombohedral crystal lattice structure, is a semimetal with a small effective electron mass, long carrier mean free path, highly anisotropic Fermi surface, and small energy overlap (about 38 meV at 77 K) between the L-point conduction band and the T-point valence band, which can lead to semimetal-semiconductor transition in Bi nanowires with decreasing diameter to a certain value (about 60 nm at 77 K) [1]. Both theoretical and experimental results showed that low-dimensional Bi could have an even larger enhancement in thermoelectric efficiency relative to the bulk one [2,3]. The combination of Bi element with antimony (Sb) and tellurium (Te) to form alloy, junction, and superlattice nanowires only starts to emerge recently, which was expected to demonstrate more excellent thermoelectric performances.In the literature, there are a large number of reviews on the progress of thermoelectric materials, which will ...

Emerging Mono‐Elemental Bismuth Nanostructures: Controlled Synthesis and Their Versatile Applications

“…44-1246). The size of 1D Bi nanostructures plays a vital role in the semimetal to semiconductor transition of Bi due to the quantum confinement effect, [55,95,96] which also significantly affects unique electrical conductivity, [97][98][99] thermoelectric, [46] and superconductivity properties. [100] Therefore, 1D Bi nanostructures are fascinating systems for studying physicochemical properties in the nanoscale owing to their anisotropic character.…”

Functional silver nanostructured surfaces applied in SERS and SIMS

“…The impact of the active nanostructured materials research on both, fundamental science and potential industrial application has been tremendous and is still growing in its broadest sense. The main challenges in electrochemical one‐dimensional nanostructures preparation are to control the diameter, orientation and alloy composition with high precision, and thereby to gain ready access to junction and superlattice structure . A lot of recent research articles deal with a preparation of functional nanostructured surfaces by applying in templates and controlled electrodeposition.…”