University of Groningen Layer-by-Layer Assembly of Clay-Carbon Nanotube Hybrid Superstructures Chalmpes, Nikolaos; Kouloumpis, Antonios; Zygouri, Panagiota; Karouta, Niki; Spyrou, Konstantinos; Stathi, Panagiota; Tsoufis, Theodoros; Georgakilas, Vasilios; Gournis, Dimitrios; Rudolf, Petra Published in: ACS Omega DOI: 10.1021/acsomega.9b01970 IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2019 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Chalmpes, N., Kouloumpis, A., Zygouri, P., Karouta, N., Spyrou, K., Stathi, P., ... Rudolf, P. (2019). Layer- by-Layer Assembly of Clay-Carbon Nanotube Hybrid Superstructures. 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Article Cite This: ACS Omega 2019, 4, 18100−18107 http://pubs.acs.org/journal/acsodf Layer-by-Layer Assembly of Clay−Carbon Nanotube Hybrid Superstructures † ∥ † ‡ ∥ † † Nikolaos Chalmpes, , Antonios Kouloumpis,*, , , Panagiota Zygouri, Niki Karouta, † ‡ ‡ ⊥ ‡ # § Konstantinos Spyrou, , Panagiota Stathi, , Theodoros Tsoufis, , Vasilios Georgakilas, † ‡ Dimitrios Gournis,*, and Petra Rudolf*, † Department of Materials Science and Engineering, University of Ioannina, GR-45110 Ioannina, Greece ‡ Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747AG Groningen, The Netherlands § Department of Materials Science, University of Patras, GR-26504 Patras, Greece ABSTRACT: Much of the research effort concerning layered materials is directed toward their use as building blocks for the development of hybrid nanostructures with well-defined dimensions and behavior. Here, we report the fabrication through layer-by-layer deposition and intercalation chemistry of a new type of clay-based hybrid film, where functionalized carbon nanotubes are sandwiched between nanometer-sized smectite clay platelets. Single-walled carbon nanotubes (SWCNTs) were covalently functionalized in a single step with phenol groups, via 1,3-dipolar cycloaddition, to allow for stable dispersion in polar solvents. For the production of hybrid thin films, a bottom-up approach combining self- assembly with Langmuir−Schaefer deposition was applied. Smectite clay nanoplatelets act as a structure-directing interface and reaction media for grafting functionalized carbon nanotubes in a bidimensional array, allowing for a controllable layer-by-layer growth at a nanoscale. Hybrid clay/SWCNT multilayer films deposited on various substrates were characterized by X-ray reflectivity, Raman, and X-ray photoelectron spectroscopies, as well as atomic force microscopy. ■ INTRODUCTION thermal conductivities; therefore, they are an ideal nanoma- Over the last decades, the industrial and scientific interest in terial for light-emitting diodes, smart windows, solar cells, nanofillers, self-healing thermoset/CNT nanocomposites, layered materials has been mainly driven by their physical and 9−11 chemical properties, resulting from the reduced dimensionality etc. The integration of CNTs within two-dimensional (2D) materials (such as graphene and MoS2) generates hybrid Downloaded via UNIV GRONINGEN on November 26, 2019 at 13:10:32 (UTC). of the individual layers. Their structural characteristics and in particular their high surface area, combined with their unique superstructures with improved mechanical stability and enhanced thermal and electrical properties due to the (opto)electronic properties, render layered materials ideal for a 12−15 1 2 ff See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles. wide range of applications in electronics, nanosensing, gas synergistic e ects of 2D and one-dimensional materials. separations,3 and energy storage,4 as well as in biomedical Thus, the synthesis of hybrid nanomaterials, combining the technology and drug delivery.5,6 properties of carbon nanotubes and layered materials with high fi Layered aluminosilicate minerals (smectite clays) consisting surface area, has great potential for applications in the elds of catalysis,16,17 sensing,12,16,18 optoelectronics,15,19 and biomedi- of platelets, where an aluminum oxide octahedral sheet is 16,20 sandwiched between two silicon oxide tetrahedral sheets, cine. − belong to the phyllosilicate family and exhibit a unique Studies reported so far on the development of clay CNT combination of properties including the ability to swell when hybrid superstructures concern mainly their use as additives to 21 put in contact with water, to adsorb molecules and organic/ increase the mechanical properties of polypropylene and 22,23 − inorganic cationic moieties from solutions and to exchange epoxy resin, as well as in styrene butadiene rubber 7,8 24 fi cations located between the platelets. The cation storage nanocomposites and as additives in Na on polymer matrixes 25 ability renders clay minerals an excellent template for for electrolyte nanocomposite membranes. In addition, clay− embedding molecules and nanomaterials and forms the basis CNT hybrids reduce significantly the electrical percolation for the development of hybrids and nanocomposites with well- defined dimensions and behavior.7 Received: June 30, 2019 On the other hand, carbon nanotubes (CNTs) are unique in Accepted: September 27, 2019 their aspect ratio, mechanical strength, and electrical and Published: October 23, 2019 © 2019 American Chemical Society 18100 DOI: 10.1021/acsomega.9b01970 ACS Omega 2019, 4, 18100−18107 ACS Omega Article Scheme 1. Schematic Representation of the Synthetic Procedure Followed for the Development of the Hybrid DODA−Clay/ SWCNTs-f-OH Multilayer Film Figure 1. (Left) Schematic representation of SWCNT functionalization via 1,3-dipolar cycloaddition and photographs of suspensions of the two types of SWCNTs in DMF. (Top) FT-IR (center) and Raman (right) spectra of pristine SWCNTs (a) and SWCNTs-f-OH (b). (Bottom) Differential thermal analysis/thermogravimetric (DTA/TG) curves of pristine SWCNTs (a) and SWCNTs-f-OH (b). threshold26 and improve the electrical conductivity when based on the combination of Langmuir−Schaefer (LS) − incorporated in polypropylene and epoxy matrixes.27 More- deposition and self-assembly.31 33 SWCNTs, functionalized over, due to the synergistic effect of clay nanoplatelets and with phenol groups by 1,3-dipolar cycloaddition (SWCNTs-f- carbon nanotubes, these hybrid structures have been proposed OH), were sandwiched between natural nanometer-sized clay as flame retardants in unsaturated polyester resins and platelets through layer-by-layer deposition to yield novel poly(methyl methacrylate)28,29 as well as adsorbents for the pillared structures with structural control at the molecular removal of bacterial contaminants from different water scale. An amino surfactant (dimethyldioctadecylammonium 30 + − supplies. (DODA) bromide, [CH3(CH2)17]2(CH3)2N Br ) was in- In this work, we propose a simple and low-cost method for jected on top of an aqueous suspension of Na-montmorillonite the development of hybrid clay multilayers accommodating (Kunipia-F) in the Langmuir−Blodgett trough to induce the functionalized single-walled carbon nanotubes (SWCNTs) formation of a hybridized Langmuir film at the air-suspension 18101 DOI: 10.1021/acsomega.9b01970 ACS Omega 2019, 4, 18100−18107 ACS Omega Article Figure 2. (Left) Π−A isotherms of DODA Langmuir films on pure water and on Kunipia aqueous suspensions. (Right) Atomic force microscopy (AFM) height images and cross-sectional analysis of DODA−clay monolayers deposited with the LS technique onto Si wafers at surface pressures of (a) 5 mN m−1, (b) 10 mN m−1, (c) 15 mN m−1, and (d) 20 mN m−1 during the compression process. interface. After the transfer of the compressed Langmuir film Raman spectra of SWCNTs-f-OH and pristine SWCNTs are by horizontal dipping (Langmuir−Schaefer method), the shown in Figure 1 (top right panel). For both materials, the substrate was immersed in a dispersion of SWCNTs-f-OH to defect-induced D band appears at 1335 cm−1 and the G band fi ω− −1 ω+ −1 prompt self-assembly. Hybrid multilayer lms hosting splits into two modes, G at 1545 cm and G at 1590 cm , SWCNTs within the interlayer space between clay platelets resulting from the characteristic confinement and curvature of were fabricated by repeating this cycle for numerous times 42−49 carbon nanotubes. The ID/IG ratio of pristine SWCNTs (Scheme 1) with the help of a robotic arm. These novel clay- and SWCNTs-f-OH was calculated to amount to 0.07 and fi based hybrid