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A novel method of preparing reduced graphene oxide (rGO)–silicon (Si) junctions free from native silicon oxide layer at room temperature is reported. The method is based on a simultaneous reduction–dissolution reaction between graphene oxide (GO) and fresh Si atoms with the assistance of dilute hydrofluoric acid (HF). The rGO–Si junction is characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. A reaction mechanism is proposed that Si is oxidized and dissolved by HF, which transfers the electronic holes to GO and facilitates the removal of its oxygen-containing groups. The use of HF provides a unique benefit to the contact formation that native oxide on Si is removed by HF instantaneously and only fresh Si surface is in contact with rGO. Therefore, the method provides a new strategy of preparing rGO-native oxide-free Si interface, which has been a fundamental challenge in the fabrication of graphene–Si junction. Electrical tests show that rGO–Si interface has a slightly higher barrier than Al–Si. [ABSTRACT FROM AUTHOR]

The design and synthesis of novel high-performance solid phase microextraction (SPME) coatings towards organic pollutants with diverse chemical properties is still a challenge in sample preparation. Herein, a stable chitosan cross-linked graphene oxide (GOCS) aerogel was reported as a novel coating for solid phase microextraction. The interpenetrated meso- and macropores ensured the large surface area and high accessibility of the functional groups across the aerogel, resulting in high extraction performance towards target hydrophobic pollutants. The extraction capacities of the GOCS-coated SPME fiber towards analytes (e.g. polycyclic aromatic hydrocarbons, organophosphorus pesticides, organochlorine pesticides, pyrethroids, and polychlorinated biphenyls) were about 0.5–13 times as high as those obtained by the commercial fibers (30 μm polydimethylsiloxane (PDMS), 65 μm polydimethylsiloxane/divinylbenzene (PDMS/DVB)), which was attributed to the hydrophobic, π-π, halogen bond and hydrogen bond interactions between the coating and the analytes. Under the optimized extraction conditions, superior analytical performances for PAHs were achieved with a wide linearity (0.5–1000 ng L−1), high enhancement factors (311–3740), and the low limits of detection (0.03–1.28 ng L−1). Finally, the GOCS-coated SPME fiber was successfully applied to the determination of PAHs in real water samples with good recoveries (91.6%–110%). [Display omitted] • The GOCS aerogel was synthesized and fabricated as a novel SPME fiber coating. • GOCS fiber exhibited high extraction efficiency for diverse hydrophobic pollutants. • Hydrophobic, π-π, halogen bond and hydrogen bond interaction affected the extraction. • The DI-SPME method was developed for PAHs detection with high sensitivity. [ABSTRACT FROM AUTHOR]

On-skin sensors capable of capturing human electrophysiological signals are valuable for a variety of areas, such as wearable health monitoring, prosthesis, human machine interfaces (HMI). Extensive research efforts have been devoted to developing on-skin electrodes and they offer potential advantages over conventional rigid electrodes. However, those approaches usually have limitations as they require sophisticated and costly fabrication processes to produce only a small number of electrodes. Here we report the reduced graphene oxide (rGO) electrodes prepared by simultaneous room temperature reduction and patterning process for scalable fabrication of a large number of on-skin electrodes. Due to the low thickness and adhesive substrate adopted, the rGO electrodes can form conformal contact with skin even during deformation, leading to reduced impedance in skin-electrode interface. The rGO electrodes have been successfully adopted for the measurements of electromyography (EMG), electrooculogram (EOG)and electroencephalogram (EEG) signals with high fidelity. And the implementation of a HMI task is demonstrated through the recognition of five typical human hand grasping gestures via a multi-channel rGO electrode array for the control of a dexterous robotic hand to mimic the gestures. The rGO electrodes presented in this study are promising for practical applications in healthcare and HMI. This study reports the reduced graphene oxide (rGO) electrodes prepared by simultaneous room temperature reduction and patterning process for scalable fabrications of on-skin electrodes. The rGO electrodes can form conformal contact with skin even during deformation and have been successfully adopted for the measurements of EMG, EOG and EEG signals with high fidelity, as well as the implementation of a Human – Machine Interface (HMI) task. The rGO electrodes presented in this study are promising for practical applications in healthcare and HMI. Image 1 [ABSTRACT FROM AUTHOR]