Rationalizing Molecular Design in the Electrodeposition of Anisotropic Lamellar Nanostructures

Abstract

Previous work has shown that nanoscale lamellar inorganic−organic hybrid materials can be synthesized on transparent conductive substrates via the electrodeposition of Zn(OH) 2 in the presence of conjugated surfactants. These surfactants introduce p-type semiconducting supramolecular phases; thus, following conversion of the Zn(OH) 2 phase to the n-type semiconductor ZnO, the lamellar hybrids exhibit high photoconductive gains and can exhibit photovoltaic activity. We report here on a family of carboxylated terthiophene-based surfactants designed with systematic modifications to molecular geometry, valency, and flexibility to investigate how these features affect the synthesis of the p-type/n-type semiconducting hybrid materials. We use scanning electron microscopy (SEM) and two-dimensional (2D) grazing-incidence X-ray diffraction (2D-GIXD) to correlate molecular features of the surfactants with growth and orientation of the nanoscale lamellae that form during electrodeposition on either hydrophilic or hydrophobic substrates. We find that molecularly flexible, monovalent terthiophene amphiphiles with linear geometries generate highly oriented and homogeneous films of the nanoscale hybrids, whereas T-shaped geometries, rigid molecules, or divalent surfactants tend to produce more heterogeneous and isotropically oriented lamellae under the same conditions. The critical aggregation concentrations (CAC) of the amphiphiles are higher than the concentrations used during electrodeposition, indicating that the growth and orientation of lamellar structures are mediated by surfactant−substrate interactions, rather than the assemblies they form in bulk solutions. Molecular design in these hybrid systems is a key factor in optimizing function, since dense and macroscopically oriented growth is necessary in both photoconductivity and photovoltaic efficiency of solar cells.

Oriented Multiwalled Organic–Co(OH)2 Nanotubes for Energy Storage

“…Between 20 and 40 µg cm −2 , discrete flakes grow vertically from these rounded structures on the flat dense base layer (Figure d,e). This is the typical structure for electrodeposited Co(OH) 2 thin films with organic surfactants previously reported in the literature as well as in the Zn(OH) 2 studies from our group . The GIXS pattern for the flake‐dominant films shows a stronger lamellar ordering compared to dense films, with nearly isotropic (00 l ) rings corresponding to a d ‐spacing of 2.99 nm (Figure f, Figure S4, Supporting Information).…”

“…In situ synthesis of inorganic–organic hybrids has been an area of great interest as a strategy to generate unique morphologies, inspired by biomineralization processes . Electrodeposition can lead to synthesis of high surface area hybrid nanostructures with tunable interlayer spacing and controllable orientation of the inorganic layers with respect to the substrate . Applying this technique to Co(OH) 2 materials can yield high specific capacity electrodes with direct conduction pathways through the inorganic layers allowing for additive‐free operation.…”

Thiophene-Based Trimers and Their Bioapplications: An Overview

“…Various trimer carboxylic acids have been prepared, directly connected to the thiophene rings [ 342 , 343 , 344 , 345 ] or linked through a spacer. In fact, spacers of one [ 346 , 347 , 348 , 349 , 350 , 351 , 352 ], two [ 279 , 353 , 354 ], three [ 355 ], four [ 354 ], five [ 356 ] or six [ 350 ] carbon atoms are reported ( Scheme 18 , I and II). Benzoic acid, connected in para on position 3′, is also reported ( Scheme 18 , III) [ 249 , 357 ].…”

“…Furthermore, in order to avoid the esterification and the hydrolysis steps, in some works the carboxylic acid is obtained by hydrolysis of nitrile [ 313 , 342 , 345 ]. The negative charge of carboxylic acid is widely exploited for promoting attractive interactions between the trimer and other molecules, materials or surfaces [ 349 , 350 , 355 , 358 , 359 ]. Additionally, trimers carrying a carboxylic acid can be easily functionalized by esterification or amidation [ 343 , 346 , 347 , 360 ].…”

Electrodeposited Organic–Inorganic Nanohybrid as Robust Bifunctional Electrocatalyst for Water Splitting

“…Emerging as new class of advanced functional materials with nanoscale architectures and redox properties, organic–inorganic nanohybrids have been reported for several applications such as gas separation and storage, energy storage, sensors, and catalysis. − Organic–inorganic nanohybrids with an organic component cross-linked with an inorganic component through different covalent and noncovalent interactions lead to additional synergistic properties for diverse areas of applications. , Organic components such as biomolecules, π-conjugated molecules with various functionalities, offer molecular self-assembly and redox properties. , Molecular self-assembly in organic–inorganic nanohybrids with balanced hydrophobic–hydrophilic character of the organic component enables the formation of a cross-linked network with various nanoscale architectures. − However, the inorganic component provides various electrochemical properties and physical properties such as thermal stability. Therefore, organic–inorganic nanohybrid-based electrodes can be used as electrocatalysts for energy conversion .…”