Reduced Graphene Oxide/Carboxymethyl Cellulose Nanocomposites: Novel Conductive Films.

Herein, carboxymethyl cellulose nanocomposite films incorporated with graphene oxide and reduced graphene oxide were successfully prepared by a novel approach for the first time, and their alternative properties compared with the original carboxymethyl cellulose films were disclosed. For carboxymethyl cellulose/reduced graphene oxide film preparation, sodium borohydride was used as a chemical reducing agent. The carboxymethyl cellulose films were prepared by using a solvent casting method, followed by an acid treatment to decrease the water solubility (98%) while enhancing the tensile strength (15%) and elastic modulus (32%) of the original carboxymethyl cellulose films. Overall, the addition of 1.0 wt% graphene oxide and reduced graphene oxide to the treated films increased the water solubility, water absorption, tensile properties and electrical conductivity. Particularly, the electrical conductivity was predominantly enhanced 1.3×105 times with graphene oxide and 2.2×105 times with reduced graphene oxide compared to the treated carboxymethyl cellulose film. The electrical conductivity of the treated carboxymethyl cellulose film also increased with an increase in reduced graphene oxide. The effects of reduced graphene oxide on the water solubility, water absorption, tensile properties and electrical conductivity of the treated carboxymethyl cellulose film were more pronounced than those of graphene oxide, especially for the electrical conductivity. In conclusion, graphene oxide and reduced graphene oxide might be alternative nanofillers for improving the carboxymethyl cellulose film properties. For the future applications, carboxymethyl cellulose/reduced graphene oxide films prepared by using this approach might be employed as alternative materials in electronic packagings and electrochemical biosensors.

Non-invasive textile based colorimetric sensor for the simultaneous detection of sweat pH and lactate.

A non-invasive textile-based colorimetric sensor for the simultaneous detection of sweat pH and lactate was created by depositing of three different layers onto a cotton fabric: 1.) chitosan, 2.) sodium carboxymethyl cellulose, and 3.) indicator dye or lactate assay. This sensor was characterized using field emission scanning electron microscopy and fourier transform infrared spectroscopy. Then, this sensor was used to measure pH and lactate concentration using the same sweat sample. The sensing element for sweat pH was composed of a mixture of methyl orange and bromocresol green while a lactate enzymatic assay was chosen for the lactate sensor. The pH indicator gradually shifted from red to blue as the pH increased, whereas the purple color intensity increased with the concentration of lactate in the sweat. By comparing these colors with a standard calibration, this platform can be used to estimate the sweat pH (1-14) and the lactate level (0-25 mM). Fading of the colors of this sensor was prevented by using cetyltrimethylammonium bromide (CTAB). The flexibility of this textile based sensor allows it to be incorporated into sport apparels and accessories hence potentially enabling real-time and continuous monitoring of sweat pH and lactate. This non-invasive sensing platform might open a new avenue for personal health monitoring and medical diagnosis as well as for determining of the physiological conditions of endurance athletes.