Fast Conductance Switching in Single‐Crystal Organic Nanoneedles Prepared from an Interfacial Polymerization‐Crystallization of 3,4‐Ethylenedioxythiophene

Abstract

Science at the nanoscale has been one of the most exciting areas of recent investigation, with activities that are of both fundamental and technological significance. New physical phenomena and revolutionary nanoeletronic devices based on novel nanomaterials are anticipated. Organic conjugated systems have been successfully applied to electronics because of their versatile electronic properties and their adaptability to a broad range of processing methods. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] However, the development of polymer electronics at the nanoscale is in its infancy.Here we report the first synthesis of polythiophene nanoneedles that exhibit fast, field-induced conductance switching in a single nanocrystalline element.Most of the bulk conducting-polymer systems studied contain regions that are inhomogeneous. The investigation of processes in a nanodomain of a single crystal is critical in ascertaining the inherent electronic properties of polymer nanoelements. Single nanocrystals of conducting polymers have not been reported, although needle-shaped bulk crystals of the quarterphenyl cation radical salt have previously been studied, [15,16] and highly ordered polymer structures have been prepared by methods including electrochemical epitaxial polymerization, [10] solution spin-coating on functionalized surfaces, [17] and solid-state polymerization of monomer crystals. [18] To date, polythiophenes, together with polyanilines and polypyrroles, represent the most important classes of conducting polymers. [19] Applying an interfacial polymerizationcrystallization process, we have prepared single crystals of poly(3,4-ethylenedioxythiophene) (PEDOT) as nanoneedles.The aqueous/organic interface used consists of 3,4-ethylenedioxythiophene (EDOT) in an organic solvent and an oxidant, ferric chloride, in deionized (DI) water. The use of ferric chloride as an oxidant in the precipitation polymerization of thiophenes has been documented. [20][21][22] In these reactions, polymer chains are generally formed first, followed by the precipitation of crystals. Our system uses, for the first time, ferric chloride in the interfacial polymerization of thiophenes.As the crystal growth is simultaneous with polymerization, more ordered crystal packing can be expected. In a typical synthesis, EDOT dissolved in dichloromethane (DCM, 5 mL, 1 mg mL -1 ) served as the lower organic layer, and FeCl 3 dissolved in DI water (5 mL, 1 mg mL -1 ) formed the upper layer. After 2 days, the aqueous layer was carefully collected for purification. To prevent the hydrolysis of FeCl 3 , 5 drops of concentrated HCl (37 %) were added to the collected suspension. The nanoneedle suspension was then centrifuged, and the precipitate was re-suspended. This process was repeated twice and was followed by a final dialysis step in ultrapure water (resistivity 18.2 MX cm, total organic carbon level 10 ppb) for 10 h. The oxidative coupling polymerization of EDOT at the aqueous/organic interface was facilitated by FeCl 3 [23] and is an example of a s...

One‐Dimensional Conducting Polymer Nanostructures: Bulk Synthesis and Applications

“…The interfacial polymerization technique has also been applied to the polymerization of EDOT which results in short nanorodlike structures of PEDOT. [80,81] The PEDOT nanorods possess an average diameter of 30 nm and appear to display a high degree of structural order.…”

Organic single crystals or crystalline micro/nanostructures: Preparation and field-effect transistor applications

“…One-dimensional polymer nanostructures could be fabricated via hard template methods [47][48][49][50][51][52][53], soft template method [54][55][56][57], and self-assembly process [58][59][60][61][62][63]. As one of the most special cases of one-dimensional polymer nanostructures, single-crystalline polymer is of great significance because it reveals the intrinsic charge-transport properties of polymer semiconductors and it has great advantages in large-area device fabrications, solution-process, mechanical flexibility, and the incorporation of functionality by molecular design.…”

Preparation and characterization of conductive chitosan-poly[N-(3-trimethoxysilylpropyl)aniline] hybrid submicrostructures

“…1,2 Compared to saturated polymers, CPs contain abundant π-conjugated system, responsible for their amazing electronic properties such as electrical conductivity, low energy optical transitions, low ionization potential, and high electron affinity. 3,4 Among the conjugated polymers, polyaniline (PANI) is the remarkable CP that has been studied for electronic and optical applications.…”