Four different graphene-based temperature sensors were prepared, and their temperature and humidity dependences were tested. Sensor active layers prepared from reduced graphene oxide (rGO) and graphene nanoplatelets (Gnp) were deposited on the substrate from a dispersion by air brush spray coating. Another sensor layer was made by graphene growth from a plasma discharge (Gpl). The last graphene layer was prepared by chemical vapor deposition (Gcvd) and then transferred onto the substrate. The structures of rGO, Gnp, and Gpl were studied by scanning electron microscopy. The obtained results confirmed the different structures of these materials. Energy-dispersive X-ray diffraction was used to determine the elemental composition of the materials. Gcvd was characterized by X-ray photoelectron spectroscopy. Elemental analysis showed different oxygen contents in the structures of the materials. Sensors with a small flake structure, i.e., rGO and Gnp, showed the highest change in resistance as a function of temperature. The temperature coefficient of resistance was 5.16⁻³·K⁻¹ for Gnp and 4.86⁻³·K⁻¹ for rGO. These values exceed that for a standard platinum thermistor. The Gpl and Gcvd sensors showed the least dependence on relative humidity, which is attributable to the number of oxygen groups in their structures.

An ammonia gas sensor material based on sulf- onic functionalized single-wall carbon nanotubes modified by poly(3,4-ethylenedioxythiophene), namely, PEDOT/SWCNT-SO ₃ H, was prepared via in situ polymerization. A thin active layer of PEDOT/SWCNT-SO ₃ H was deposited on a polyimide substrate with interdigital electrodes by air-brush spray coating. The morphology of the prepared material was studied by scanning electron microscopy, and the presence of PEDOT in the structure of SWCNT-SO ₃ H was examined with Raman spectroscopy. The obtained results showed that PEDOT was successfully bound to SWCNT-SO ₃ H and that this modification significantly improved the NH ₃ sensing performance of the sensor. The sensor exhibited a strong response to ammonia (102% at 50 ppm), minimal drift in the electrical resistance during cyclic exposure, and good spontaneous desorption, all at room temperature. In the range from 20 ppm to 100 ppm ammonia, the calibration curve is considered linear, with a sensitivity of a 0.7% resistance change per 1 ppm ammonia. Furthermore, the sensor shows the ability to detect ammonia at sub-ppm concentration, and the response is 4.4% at 300 ppb. With regard to the material structure, the sensing mechanisms of both materials, i.e., PEDOT/SWCNT-SO ₃ H and SWCNT-SO ₃ H, are discussed in the article.

This article addresses reliability under the sweat of interconnection techniques for the mounting surface mounted device (SMD) components and fully printed humidity sensors onto conductive stretchable textile ribbons. Samples underwent testing for the effect of ageing by artificial sweat on their electrical resistance using both alkaline and acidic artificial sweat. The best results in terms of electrical resistance change were obtained for samples soldered to the conductive fibers interwoven in the ribbon. However, this method can damage the ribbon due to the high temperature during soldering and significantly reduce the mechanical properties and flexibility of the ribbon, which can lead to a limited service life of samples. On the other hand, adhesive bonding is a very interesting alternative, where the above-mentioned properties are preserved, but there is a significant effect of sweat ageing on electrical resistance. The results of fully printed graphene-based humidity sensors show that, for the intended use of these sensors (i.e., detection of changes in moisture on the human body), usage of the samples is possible, and the samples are sufficiently reliable in the case of sweat degradation. In addition, the response of the sensor to humidity is quite high: 98% at a relative humidity of 98%.

Temperature monitoring and regulation are essential in various environments, including modern industry and living and storage spaces. The growing demand for temperature sensors calls for affordable, efficient, interference‐resistant, and eco‐friendly solutions. The challenge of humidity interference in constructing temperature sensors often leads to compromising on the dynamic sensor properties in particular due to the need for encapsulation. To this end, this study introduces a temperature sensor leveraging a carefully designed graphene derivative to mitigate the humidity interference. The material, synthesize through scalable fluorographene chemistry with benzylamine, is optimized in order to enhance its properties, which led to achieving peak efficiency with a minimal humidity impact. The sensor demonstrated full functionality across a temperature range from 10 to 90 °C, with a temperature coefficient of resistivity 8.63 × 10⁻³ K⁻¹, which is more than twice as high as that of conventional platinum thermometers. Remarkably, the sensor exhibited only a 2% change in resistance when exposed to relative humidity in the range of 20 to 70%. Notably, the sensor continues to give a consistent performance even after six months, which proved its stability. The presented device holds promise for evolving into a fully printed, cost‐effective and reliable next‐generation temperature sensors.

An ammonia gas sensor based on nanostructured polypyrrole functionalised by carboxylic groups (PPy-COOH) was prepared and characterised. The active layer was deposited on a ceramic substrate with gold interdigital electrodes by a low-cost airbrush-spray coating technique and the sensor exhibited a strong response to ammonia (Z/Z ₀ = 5.48 at 100 ppm) in comparison with pure polypyrrole (Z/Z ₀ = 1.5 at 100 ppm). Cross-sensitivity measurement showed a more significant response to relative humidity and so two approaches were used to reduce this undesirable humidity dependence: (i) the creation of a hydrophobic metal-organic framework (so-called MAF-6) on the PPy-COOH layer, and (ii) the fabrication of a heterostructure of PPy-COOH with multi-wall carbon nanotubes (MWCNT). Both approaches resulted in a significant reduction in the humidity dependence of the sensor, from the value Z/Z ₀ = 0.02 (PPy-COOH) to 0.404 and 0.427 for PPy-COOH-MAF-6 and PPy-COOH/MWCNT, respectively. However, the samples coated with MAF-6 showed a smaller decrease in response to ammonia. In addition, the proposed approach with MAF-6 functionalisation allowed ammonia detection within a broader RH range (up to 60% RH) compared to the PPy-COOH sensing layer. The presence of MAF-6 on the surface of PPy-COOH was further verified by infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), and scanning electron microscopy (SEM). The sensing mechanisms of ammonia and relative humidity of the PPy-COOH material are also discussed in the paper.