An international group of researchers from Saudi Arabia, China and the US have developed a graphene-bacterial cellulose nanofiber (GC/BCN) hybrid sensor to detect alcohol (ethanol) with great efficiency. The sensor was described as flexible, transparent, highly sensitive and with an excellent alcohol recognition performance. Electrical tests in different liquid environments were performed, with remarkable results.

The researchers created a composite thin film composed of graphene and bacterial cellulose nanofibers. In this material, the bacterial cellulose nanofibres act as the host and the graphene as the filler material. Due to its excellent conductive properties, it was reported that graphene does not require the addition of a conductive filler material, unlike many composites. The Researchers constructed the composite using a combination of wet chemical, blending, sonication (Cole-Parmer), centrifugal (Centrifuge 5810, Eppendorf), dialysis and sputtering (Equipment Support Co) methods.

The sensor exhibited an ultrahigh sensitivity of up to 12400% in the presence of pure vapor-phase ethanol compared to a 920% sensitivity in a pure water medium. The sensitivity for vapor-phase ethanol was orders of magnitude higher than using just graphene- which only exhibited a 21% to pure ethanol. The intelligent sensor was also able to distinguish between liquid-phase ethanol, vapor-phase ethanol and water, and produced a readout as a function of electrical signals within the electronic device. The sensor also exhibited fast response and recovery times, and usage across a wide range of ethanol concentrations- between 10% and 100% ethanol concentration.

The researchers characterized the samples through transmission electron microscopy (TEM, Tecnai Twin, FEI), Fourier transform-infrared (FTIR) spectroscopy (Nicolet iS10, Thermoscientific Inc.), Ultraviolet-visible (UV-vis) spectroscopy (Cary100 ConC, Agilent Technologies), profilometry (DEKTAK*8 profilometer, Veeco). The sheet resistance was measured on a CMT-SR2000N four-probe system (Materials Development Corporation); surface tensions were measured using Kruss K100 tensiometer; and the electrical resistance was calculated using a U1281A True RMS Multimeter (Keysight).

The Researchers have produced a facile, green and low-cost route for the assembly of ethanol-sensing devices with the potential to be implemented across a wide range of applications and industries.