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In this work, we present a low-cost, fast and simple fabrication of resistive-type humidity sensors based on the graphene quantum dots (GQDs) and silver nanoparticles (AgNPs) nanocomposites. The GQDs and AgNPs were synthesized by hydrothermal method and green reducing agent route, respectively. UV–Vis spectrophotometer, X-ray photoelectron spectroscopy and field-emission transmission electron microscopy were used to characterize quality, chemical bonding states and morphology of the nanocomposite materials and confirm the successful formation of core/shell-like AgNPs/GQDs structure. According to sensing humidity results, the ratio of GQDs/AgNPs 1 : 1 nanocomposite exhibits the best humidity response of 98.14% with exponential relation in the humidity range of 25–95% relative humidity at room temperature as well as faster response/recovery times than commercial one at the same condition. The sensing mechanism of the high-performance GQDs/AgNPs humidity sensor is proposed via Schottky junction formation and intrinsic synergistic effects of GQDs and AgNPs.

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Growth of helical carbon coils can be achieved by sputtered Inconel® 600 films on silicon (Si) substrates followed by thermal chemical vapor deposition (CVD) using acetylene as a carbon source along with the injection of sulfur hexafluoride (SF6). The coils were used to prepare electronic ink for fabrication of flexible room temperature gas sensors. The ink as a sensing film was deposited onto silver-screen printed plastic substrates using a droplet coating technique. Before dripping the sensing film, the coils were purified using oxidation and acid treatments. The purified coils were then dispersed in different solvents such as deionized water (DI water), ethanol and dimethyl sulfoxide (DMSO) for comparisons. The performance of sensors was investigated for its response to ammonia (NH3) and volatile organic compounds (VOCs) including ethanol, methanol, and dimethylformamide (DMF) in concentration of 1000 ppm at room temperature. Because the baseline resistance of sensor falls within the working range (i.e. kΩ), the coils dispersed in DI water are performed to show the highest selectivity and sensitivity to NH3. The sensing mechanism of helically coiled carbon gas sensors has been also discussed based on the reducing reaction process between NH3 and chemisorbed oxygen on the surface of purified carbon coils.

Granular Co100-xCux films with different compositions of x = 19, 40, 54, 65 and 76 were deposited on glass substrates using sputter deposition. Co (HCP) and Cu (FCC) phases were observed in all deposited Co-Cu films. Film thickness was increased with increasing Cu-composition. The minimum and maximum values of electrical resistance measured using a four-point probe were observed on the Co24Cu76 and Co46Cu54 films, respectively, which confirmed that the electrical property of the films is a function of the film thickness and composition. The morphological and magnetic properties of all deposited films were clearly dependent on film composition. The AFM result confirmed the dependence of surface morphology and magnetic properties on the film composition because of the difference in the deposition rate between Co and Cu atoms during the sputtering process. The VSM results showed that all films had a ferromagnetic phase when the magnetic field was applied perpendicular to the film plane. All results confirmed that the desired morphological, electrical and magnetic properties of Co-Cu granular film can be achieved by manipulating its chemical composition.