In this study, a 0-3 piezoelectric composite based on lead zirconate-titanate (PZT)/polyvinyl-butyral (PVB) was fabricated and characterized for its potential application in tactile sensing. The 0-3 composite was developed to incorporate the advantages of both ceramic and polymer. The paste of 0-3 PZT–PVB composite was printed using a conventional screen-printing technique on alumina and mylar substrates. The thickness of the prepared composite was approximately 80 μm. After printing the top electrode of the silver paste, 10 kV/mm of DC field was applied at 25 °C, 120 °C, and 150 °C for 10 min to align the electric dipoles in the composite. The piezoelectric charge coefficient of d33 and the piezoelectric voltage coefficient of g33 were improved by increasing the temperature of the poling process. The maximum values of d33 and g33 were 14.3 pC/N and 44.2 mV·m/N, respectively, at 150 °C. The sensor’s sensitivity to the impact force was measured by a ball drop test. The sensors showed a linear behavior in the output voltage with increasing impact force. The sensitivity of the sensor on the alumina and mylar substrates was 1.368 V/N and 0.815 V/N, respectively. The rising time of the sensor to the finger touch was 43 ms on the alumina substrate and 35 ms on the mylar substrate. Consequently, the high sensitivity and fast response time of the sensor make the 0-3 PZT–PVB composite a good candidate for tactile sensors.

Research on stretchable strain sensors is actively conducted due to increasing interest in wearable devices. However, typical studies have focused on improving the elasticity of the electrode. Therefore, methods of directly connecting wire or attaching conductive tape to materials to detect deformation have been used to evaluate the performance of strain sensors. Polyaniline (PANI), a p-type semiconductive polymer, has been widely used for stretchable electrodes. However, conventional procedures have limitations in determining an appropriate metal for ohmic contact with PANI. Materials that are generally used for connection with PANI form an undesirable metal-semiconductor junction and have significant contact resistance. Hence, they degrade sensor performance. This study secured ohmic contact by adapting Au thin film as the metal contact layer (the MCL), with lower contact resistance and a larger work function than PANI. Additionally, we presented a buffer layer using hard polydimethylsiloxane (PDMS) and structured it into a dumbbell shape to protect the metal from deformation. As a result, we enhanced steadiness and repeatability up to 50% strain by comparing the gauge factors and the relative resistance changes. Consequently, adapting structural methods (the MCL and the dumbbell shape) to a device can result in strain sensors with promising stability, as well as high stretchability.

Stretchable strain sensors are capable of acquiring data when in contact with human skin or equipment and are widely used in wearable applications. Most strain sensors have tensile properties of less than 20% and have limitations regarding body motion linkage, complex sensor structure, and motion nonreliability. To address these problems, we developed a high tension and high sensitivity sensor with a gauge factor over 40 and tensile stress about 50%. Polydimethylsiloxane (PDMS) was selected as the flexible substrate to ensure tensile strength, and polyaniline (PANI) was used to measure the resistance changes in the sensor. In particular, problems regarding poor uniformity of PANI on PDMS were resolved by surface treatment of the PDMS, wherein PANI polymerization was performed sequentially after forming a self-assembled monolayer (SAM) on the PDMS substrate. O2 plasma and (3-aminopropyl)triethoxysilane were used to form the SAM. It is expected that this sensor can obtain stable characteristics even under high tensile stress through the evenly formed PANI films on the surface-treated PDMS substrate and may be used in various flexible sensor applications.

Extensive investigations have been made over the past two decades on the two-dimensional molybdenum sulfide (MoS2) since their dominating characteristics for the various applications including electrocatalysis and energy storage. Albeit MoS2 possesses the plentiful active sulfur edges, but their deficient inactive facets lead the poor conductivity and low efficiency. In this work, we attempted to activate more active sites by the insertion of doping transition metals such as nickel (Ni), copper (Cu) and iron (Fe) into MoS2 matrix. A facile chemical precipitation methodology was used to prepare the greatly active Fe, Cu and Ni metal doped MoS2 nanoarrays for hydrogen evolution and supercapacitors. Microscopic studies revealed the tuned morphology composed of nanoarrays structured domains of grains for metals doped MoS2 with the vertically aligned layers and extended layer spacing. The modified morphological properties, enriched surface area and plentiful active edges were apparently established for the metal doped MoS2. Hydrogen evolution results revealed that the improved electrocatalytic activity for Fe doped MoS2 nanoarrays with the low overpotentials, small Tafel slopes and unremitting reactions over 24 h in the acid and alkaline solution. The highly porous structured Cu doped MoS2 nanostructures owned the maximum capacitance of 353 F.g(-1) at 1 A.g(-1) current density with an admirable retaining capacity of similar to 94% after 5000 cycles. (C) 2021 Elsevier B.V. All rights reserved.

The interface architectures of inorganic-organic halide perovskite-based devices play key roles in achieving high performances with these devices. Indeed, the perovskite layer is essential for synergistic interactions with the other practical modules of these devices, such as the hole-/electron-transfer layers. In this work, a heterostructure geometry comprising transition-metal dichalcogenides (TMDs) of molybdenum dichalcogenides (MoX2  = MoS2 , MoSe2 , and MoTe2 ) and perovskite- or hole-transfer layers is prepared to achieve improved device characteristics of perovskite solar cells (PSCs), X-ray detectors, and photodetectors. A superior efficiency of 11.36% is realized for the active layer with MoTe2 in the PSC device. Moreover, X-ray detectors using modulated MoTe2 nanostructures in the active layers achieve 296 nA cm-2 , 3.12 mA (Gy cm2 )-1 and 3.32 × 10-4 cm2 V-1 s-1 of collected current density, sensitivity, and mobility, respectively. The fabricated photodetector produces a high photoresponsivity of 956 mA W-1 for a visible light source, with an excellent external quantum efficiency of 160% for the perovskite layer containing MoSe2 nanostructures. Density functional theory calculations are made for pure and MoX2 doped perovskites' geometrical, density of states and optical properties variations evidently. Thus, the present study paves the way for using perovskite-based devices modified by TMDs to develop highly efficient semiconductor devices.

Rationally designed gas sensing materials have become essential for modern efficient gas sensor with enhanced performance. This study designed and prepared ordered porous, three-dimensional hierarchical NiFe2O4 (NFO) nanoarchitectures for highly selective and sensitive toluene sensors. Two hierarchical NFO nanostructures including nanospheres and microsphere were fabricated by facile hydrothermal (NFO-Hy) and temperature-programmed calcination (NFO-550), respectively. Physicochemical characterization confirmed structure, composition, and morphology for the as-prepared materials. Nitrogen adsorption-desorption revealed improved surface area and porous properties for NFO-550 compared with NFO-Hy sensing materials, and the NFO-550 sensor achieved the maximum response 5.65 higher than NFO-Hy at optimal operating temperature. Primary analyses for carcinogenic analyte detection suggest NFO as a gas-sensitive material to be potential applicants for real-world toluene gas sensing applications. (c) 2021 Elsevier B.V. All rights reserved.

Transition metal oxides with unique nanoarchitectures are being appraised as plausible candidates for the highly selective detection of contaminating organic gases due to their earth abundance, high surface area, and outstanding miniaturization potential. Here, two different nanoarchitectures of nickel molybdate (NMO), namely 3D-honeycombs (NMO-HCs) and 3D-rectangular nanosheets (NMO-RNS), are proposed and synthesized via a two-step wet-chemical process and characterized for their potential application in ethanol gas sensors. The successful formation of the different nanostructures and the even distribution of all the elements are demonstrated using various morphological and energy-dispersive X-ray spectroscopic (EDAX) analyses. In addition, N-2-adsorption/desorption analysis is performed to confirm the highly porous nature and maximum surface areas of 30.4 m(2) g(-1) and 91.3 m(2) g(-1) at 77 K for the NMO-HCs and NMO-RNS, respectively. Furthermore, gas sensing analysis reveals that the NMO-HCs-based sensor provides a maximum gas response (R-a/R-g) of similar to 15.2 while the NMO-RNS-based sensor exhibits a 5.5 times higher maximum gas response of similar to 78.9 at the optimal operating temperature. Further, using R-a/R-g = 1.2 as the detection limit point, the lower limit of ethanol gas detection is found to be 0.2 ppm for the NMO-RNS-based device. Finally, the probable gas-sensing mechanism of the NMO-RNS is discussed. The present study indicates that the NMO-RNS sensor can sense ppb-levels of ethanol and is suitable for the monitoring of outdoor and indoor air quality in practical applications.