Abstract
In this paper we detail a novel semi-automated method for the production of graphene by sonochemical exfoliation of graphite in the presence of ionic surfactants, e.g., sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB). The formation of individual graphene flakes was confirmed by Raman spectroscopy, while the interaction of graphene with surfactants was proven by NMR spectroscopy. The resulting graphene–surfactant composite material formed a stable suspension in water and some organic solvents, such as chloroform. Graphene thin films were then produced using Langmuir–Blodgett (LB) or electrostatic layer-by-layer (LbL) deposition techniques. The composition and morphology of the films produced was studied with SEM/EDX and AFM. The best results in terms of adhesion and surface coverage were achieved using LbL deposition of graphene(−)SDS alternated with polyethyleneimine (PEI). The optical study of graphene thin films deposited on different substrates was carried out using UV–vis absorption spectroscopy and spectroscopic ellipsometry. A particular focus was on studying graphene layers deposited on gold-coated glass using a method of total internal reflection ellipsometry (TIRE) which revealed the enhancement of the surface plasmon resonance in thin gold films by depositing graphene layers.
Highlights
Since its initial discovery and development by Novoselov et al [1] graphene has been of great interest to the scientific community due to its interesting optical and electrical properties
This method was chosen for a number of reasons; firstly, it does not require the use of hazardous chemicals such as sodium nitrate, sulfuric acid, potassium permanganate and hydrazine hydrate, which are used in the oxidation of graphite to graphite oxide and the subsequent reduction to graphene [5], and secondly it guarantees single-layer or few-layer graphene, rather than the potentially larger products or graphene sheets with an uneven size distribution that might be produced in other techniques such as mechanical exfoliation
For the LbL deposition of alternating layers of graphene(−)sodium dodecyl sulfate (SDS) and graphene(+)cetyltrimethylammonium bromide (CTAB) on gold-coated glass slides, a gold film of approximately 25 nm thickness was thermally evaporated onto a 3 nm under layer of chromium
Summary
Since its initial discovery and development by Novoselov et al [1] graphene has been of great interest to the scientific community due to its interesting optical and electrical properties. Langmuir–Blodgett and Langmuir–Schaefer deposition Both composite materials obtained, e.g., graphene(+)CTAB and graphene(−)SDS, appeared to be soluble in water due to the presence of ionic groups, NMe3+ and SO3−, respectively. For the LbL deposition of alternating layers of graphene(−)SDS and graphene(+)CTAB on gold-coated glass slides, a gold film of approximately 25 nm thickness was thermally evaporated onto a 3 nm under layer of chromium (which was used to improve adhesion between the gold and the glass).
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