Abstract
In this study, we present a comprehensive investigation of graphene’s optical and conductive properties using confocal Raman and a Drude model. A comparative analysis between experimental findings and theoretical predictions of the material’s changes and improvements as it transitioned from three-dimensional graphite is also presented and discussed. Besides spectral recording by Raman, which reveals whether there is a single, a few, or multi-layers of graphene, the confocal Raman mapping allows for distinction of such domains and a direct visualization of material inhomogeneity. Drude model employment in the analysis of the far-infrared transmittance measurements demonstrates a distinct increase of the material’s conductivity with dimensionality reduction. Other particularly important material characteristics, including carrier concentration and time constant, were also determined using this model and presented here. Furthermore, the detection of micromolar concentration of dopamine on graphene surfaces not only proves that the Raman technique facilitates ultrasensitive chemical detection of analytes, besides offering high information content about the biomaterial under study, but also that carbon-based materials are biocompatible and favorable micro-environments for such detection. Such information is valuable for the development of bio-medical sensors, which is the main application envisioned for this analysis.
Highlights
Since being discovered, graphene [1] has attracted significant research interests due to its exceptional and unique properties, such as high carrier mobility at room temperature, transparency, and conductivity
As a first step, we present in this work a detailed confocal Raman microscopic investigation that combines analysis of Raman spectra with direct visualization of graphene domains consisting of either single layers, a few layers, or multiple layers
We present and discuss an alternative method to study the conductivity of graphene using the Drude model
Summary
Graphene [1] has attracted significant research interests due to its exceptional and unique properties, such as high carrier mobility at room temperature, transparency, and conductivity. It has been investigated as a feasible candidate for use in device fabrication in numerous areas: electronics [2,3,4,5,6,7,8,9,10], optics [11,12], photonics [3,13], micro/nano-mechanics [14,15,16], and, recently, biomedical engineering [17,18,19,20]. Many efforts have been made in the last decade related to the conductivity of graphene—in finding accurate measuring methods, as well as in fabricating new graphene-based materials with improved performance [23,24,25]. Excellent optical and electric performance has been achieved with core-shell nanowires based on Cu and reduced graphene
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