Fluorographene: Synthesis and sensing applications
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Venkatesan Renugopalakrishnan Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA; and Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115, USA (Received 14 December 2016; accepted 27 March 2017)
This article features the recent developments in fluorographene (FG) and its other functional forms such as fluorographene oxide—their synthesis, fluorination, defluorination, and applications. FG is identified as an important functional derivative of graphene, and FG’s multifunctionalities make it as an ideal candidate for diverse fields, say from photovoltaic to bio-medical diagnosis, imaging, sensing, and therapy. Here the possibilities of FG as a biomedical sensing platform is discussed in detail and the potentials of FG based electrochemical and conductometric sensing platforms are unraveled. The importance of fluorine control as well as the other key factors need to be considered while choosing FG based bio-sensing platforms are also discussed.
I. INTRODUCTION TO ENGINEERING OF GRAPHENE—DOPING
The vital aim of all chemical sensors is single atom/ molecule level sensitivity, and such a level of sensitivity was far from the reach of practical sensors, including in solid state gas sensors.1 The limitations for reaching such an extreme sensitivity was the thermal fluctuations of charges and defects in the sensing platform, leading to increased noise levels.2,3 This intrinsic noise levels in a sensing platform can be circumvented by the use of low electronic noise systems such as graphene, where it combines the following exceptional properties to increase the signal to noise ratio: (i) a truly two-dimensional (2D) material where the whole volume is available (all the atoms are exposed) for interactions with the adsorbent or analyte, (ii) low Johnson–Nyquist noise due to its very high conductivity, (iii) low level crystals defects and hence low Flicker noises, and (iv) high precision conductivity measurements with low contact resistances are possible due to its large area, high crystallinity and low level defects.1,4–6 These properties make graphene as a unique platform for single quanta (atom/molecule) detection of analyte to a level of monitoring the changes of its local carrier concentration by less than one electron charge with ultra low noises at room temperature. The operational principle of most of the graphene based sensors is the changes in the electrical conductivity due to the adsorbed molecules, where the molecules act as electron acceptors or donors. Further, all the above properties along with high carrier mobility of graphene bring Contributing Editor: Gary L. Messing a) Address all correspondence to this author. e-mail: [email protected], [email protected] DOI: 10.1557/jmr.2017.135
exceptionally enhanced sensing possibilities. But, the experiments on pristine graphene demonstrating its ultrahigh signal to noise ratio showing single molecule level detection is limited to only a few molecules such as NO2. It is also found to be un
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