Ultrathin Nanoribbons Research Articles

Solution Synthesis of Ultrathin Single-Crystalline SnS Nanoribbons for Photodetectors via Phase Transition and Surface Processing

We report the solution-phase synthesis and surface processing of ~2-5 μm long single-crystalline IV-VI tin(II) sulfide (SnS) ultrathin nanoribbons, with thicknesses down to 10 nm, and their use in single nanoribbon based photodetectors. The SnS nanoribbons grow via a metastable-to-stable phase transition from zinc blende (ZB) nanospheres to orthorhombic nanoribbons; dual-phase intermediate heterostructures with zinc blende nanosphere heads and orthorhombic nanoribbon tails were observed. Exchange of long, insulating organic oleylamine ligands by short, inorganic HS(-) ligands converts the organic SnS nanoribbons into completely inorganic, hydrophilic structures. Field-effect transistor (FET) devices were made from single SnS nanoribbons, both before and after ligand exchange, which exhibit p-type semiconductor behavior. The SnS single nanoribbon based photodetector devices showed highly sensitive and rapid photocurrent responses to illumination by blue, green, and red light. The switching behavior of photocurrent generation and annihilation is complete within approximately 1 ms and exhibits high photoconductivity gains (up to 2.3 × 10(4)) and good stability. The ON/OFF ratio of the photodetector can be engineered to 80 (4 nA/50 pA) using a small drain current (10 mV) for the all inorganic SnS nanoribbons. This work paves the way for the colloidal growth of low-cost, environmentally benign, single-crystalline narrow band gap semiconductor nanostructures from abundant elements for applications in photodetectors and other nanoscale devices.

Hyperbranched microspheres formed by an EDTA-based coordination polymer with ternary architectures assembled by ultrathin nanoribbons and their tricolor luminescent properties

Here we report a novel structure of hierarchical coordination polymers with hyperbranched microspheres. The microspheres were formed by the automatic piling of ultrathin nanoribbons with a thickness of 3.5 ± 0.1 nm, which resulted from the prior self-assembly of the molecules in a ternary architecture. Briefly, the ultrathin nanoribbons of the lanthanide–EDTA coordination polymers were prepared via an Ostwald ripening process, by a simple hydrothermal treatment in an aqueous mixture of lanthanide cations and EDTA-2Na ligands. To satisfy the requirement of a low surface/interface energy, these ultrathin nanoribbons were then self-assembled into multi-layer nanoribbons, followed by the formation of hyperbranched microspheres. Finally, tricolor (red, green and blue, known as RGB) fluorescent hyperbranched microspheres were also prepared by doping with Eu3+, Tb3+ and Zn2+ as luminescent centers, respectively. Our work shows a simple method to fabricate complex structures of coordination polymers and may inspire further studies on hierarchical architectures of coordination polymers.

Ultrathin Topological Insulator Bi2Se3 Nanoribbons Exfoliated by Atomic Force Microscopy

Ultrathin topological insulator nanostructures, in which coupling between top and bottom surface states takes place, are of great intellectual and practical importance. Due to the weak van der Waals interaction between adjacent quintuple layers (QLs), the layered bismuth selenide (Bi(2)Se(3)), a single Dirac-cone topological insulator with a large bulk gap, can be exfoliated down to a few QLs. In this paper, we report the first controlled mechanical exfoliation of Bi(2)Se(3) nanoribbons (>50 QLs) by an atomic force microscope (AFM) tip down to a single QL. Microwave impedance microscopy is employed to map out the local conductivity of such ultrathin nanoribbons, showing drastic difference in sheet resistance between 1-2 QLs and 4-5 QLs. Transport measurement carried out on an exfoliated (<or=5 QLs) Bi(2)Se(3) device shows nonmetallic temperature dependence of resistance, in sharp contrast to the metallic behavior seen in thick (>50 QLs) ribbons. These AFM-exfoliated thin nanoribbons afford interesting candidates for studying the transition from quantum spin Hall surface to edge states.

Ultrathin n-Type Organic Nanoribbons with High Photoconductivity and Application in Optoelectronic Vapor Sensing of Explosives

Well-defined ultrathin nanoribbons have been fabricated from an amphiphilic electron donor-acceptor (D-A) supramolecule comprising perylene tetracarboxylic diimide as the backbone scaffold to enforce the one-dimensional intermolecular assembly via strong pi-stacking. These nanoribbons demonstrated high photoconductivity upon illumination with white light. The high photoconductivity thus obtained is likely due to the optimal molecular design that enables a good kinetic balance between the two competitive processes, the intramolecular charge recombination (between D and A) and the intermolecular charge transport along the nanoribbon. The photoconduction response has also proven to be prompt and reproducible with the light turning on and off. The photogenerated electrons within the nanoribbon can be efficiently trapped by the adsorbed oxygen molecules or other oxidizing species, leading to depletion of the charge carriers (and thus the electrical conductivity) of the nanoribbon, as typically observed for n-type semiconductor materials as applied in chemiresistors. Combination of this sensitive modulation of conductivity with the unique features intrinsic to the nanoribbon morphology (large surface area and continuous nanoporosity when deposited on a substrate to form a fibril film) enables efficient vapor sensing of nitro-based explosives.

Cutting Gallium Oxide Nanoribbons into Ultrathin Nanoplates

Good quality gallium oxide/gallium sulfide nanoplates having an ultrathin thickness, via reaction of gallium oxide nanoribbons with sulfur solution, were prepared. The cutting of the ultrathin nanoribbons into plates originated from the lattice mismatch between the gallium oxide and gallium sulfide, which was quite dependent on the concentration of the sulfur solution used.

Dimensional Effects on Ferroelectrics: Ultra-Thin Single Crystals, Nanotubes, Nano-Rods, and Nano-Ribbons

A discussion is presented of nano-scale ferroelectric devices. Nano-ribbons exhibit an “extra” relaxation process with an 0.20 ± 0.01 eV activation energy attributed to OH hydroxyl ion reorientation. Barium titanate single crystals down to 65-nm are characterized by bulk properties, and broadening of dielectric peaks ϵ(T) versus temperature attributed by others to intrinsic depolarization effects are instead shown to be extrinsic, due to oxygen vacancy gradients, in accord with the recent models of Catalan et al. and of Bratkovsky and Levanyuk. Similar transitions in barium strontium titanate (BST) thin films are shown to be reentrant (only upon warming from T < 50 K) and limited by kinetics, not thermodynamic equilibria.

An ultrathin carbon nanoribbon study as a component of nanoelectromechanical devices

We investigated a carbon nanoribbon (CNR) using atomistic simulations based on Tersoff–Brenner potential function. The CNR was obtained from a compressed (5,5) carbon nanotube (CNT). The obtained CNR had a cross-sectional view as a binocular telescope structure composed of both sp2 and sp3 bonds. One carbon atom per ten carbon atoms had sp3 bond. For the optimized structures, the residual forces on the CNR were 3-order higher than that on the CNR and the lattice constant of the CNR was higher 0.0624 Å than that of the CNT along the tube axis. The Young's modulus of the CNR was the same as that of the CNT whereas the critical strain of the CNR was significantly lower than that of the CNT because the residual stresses on the CNR was very higher than those on the CNT. The tensile force curve vs. the strain of the CNT was slightly higher than that of the CNR.