Low-Cost Gas Sensors Produced by the Graphite Line-Patterning Technique Applied to Monitoring Banana Ripeness

A low-cost sensor array system for banana ripeness monitoring is presented. The sensors are constructed by employing a graphite line-patterning technique (LPT) to print interdigitated graphite electrodes on tracing paper and then coating the printed area with a thin film of polyaniline (PANI) by in-situ polymerization as the gas-sensitive layer. The PANI layers were used for the detection of volatile organic compounds (VOCs), including ethylene, emitted during ripening. The influence of the various acid dopants, hydrochloric acid (HCl), methanesulfonic acid (MSA), p-toluenesulfonic acid (TSA) and camphorsulfonic acid (CSA), on the electrical properties of the thin film of PANI adsorbed on the electrodes was also studied. The extent of doping of the films was investigated by UV-Vis absorption spectroscopy and tests showed that the type of dopant plays an important role in the performance of these low-cost sensors. The array of three sensors, without the PANI-HCl sensor, was able to produce a distinct pattern of signals, taken as a signature (fingerprint) that can be used to characterize bananas ripeness

Eco-friendly gelatin films with rosin-grafted cellulose nanocrystals for antimicrobial packaging

We report on gelatin films incorporating rosin-grafted cellulose nanocrystals (r-CNCs), which fulfill the most relevant requirements for antimicrobial packaging applications. Transparent gelatin/r-CNCs bionanocomposite films (0.5–6 wt% r-CNCs) were obtained by solution casting and displayed high UV-barrier properties, which were superior to the most used plastic packaging films. The gelatin/r-CNCs films exhibited a moderate water vapor permeability (0.09 g mm/m2 h kPa), and high tensile strength (40 MPa) and Young's modulus (1.9 GPa). The r-CNCs were more efficient in improving the optical, water vapor barrier and tensile properties of gelatin films than conventional CNCs. Grafting of rosin on CNCs resulted in an antimicrobial nanocellulose that inhibited the growth of Staphylococcus aureus and Escherichia coli. The antibacterial properties of r-CNCs were sustained in the gelatin films, as demonstrated by agar diffusion tests and proof-of-principle experiments involving cheese storage. Overall, the incorporation of r-CNCs as active fillers in gelatin films is a suitable approach for producing novel eco-friendly, antimicrobial packaging materials.This research was made possible thanks to the facilities of the Laboratory of Pulp and Paper 479 Science and Graphic Arts (LGP2) that is part of the LabEx Tec 21 (Investissements d'Avenir - grant 480 agreement n°ANR-11-LABX-0030) and of PolyNat Carnot Institute (Investissements d'Avenir - 481 grant agreement n° ANR-16-CARN-0025- 0), and Plant Macromolecule Research Center 482 (CERMAV) for the support to this work. This study was financed in part by CNPq, SISNANO 26 483 (MCTI), FINEP, Embrapa AgroNano research network (Embrapa), Coordenação de 484 Aperfeiçoamento de Pessoal de Nível Superior - Brazil (CAPES) [Finance Code 001] and by the 485 São Paulo Research Foundation (FAPESP) [grant numbers 2016/03080-2, 2017/18725-2 and 486 2018/00278-2, 2018/10899-4, 2018/22214-6, 2018/18953-8]. We would like to thank Berthine 487 Khelifi , Cécile Sillard and Thierry Encinas from Grenoble Institute of Technology for their 488 expertise in providing SEM imaging, XPS and XRD analyses, respectively