Microplotter Printing of Hierarchically Organized NiCo2O4 Films for Ethanol Gas Sensing

Abstract

Using a combination of chemical coprecipitation and hydrothermal treatment of the resulting dispersed system, a hierarchically organized NiCo2O4 nanopowder was obtained, consisting of slightly elongated initial oxide nanoparticles self-organized into nanosheets about 10 nm thick, which in turn are combined into hierarchical cellular agglomerates of about 2 μm. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HR-TEM) allowed to confirm the formation of NiCo2O4 powder with the desired crystal structure via additional heat treatment of the intermediate product. Energy-dispersive X-ray spectroscopy (EDX) was used to confirm the target metal ratio, and the uniform distribution of the elements (Ni, Co and O) was shown by mapping. The resulting nanopowder was employed to prepare functional inks suitable for microplotter printing of the NiCo2O4 film. It was found that an oxide film morphology is fully inherited from the hierarchically organized oxide nanopowder used. Atomic force microscopy (AFM) revealed the film thickness (15 μm) and determined the maximum height difference of 500 nm over an area of 25 μm2. Kelvin probe force microscopy (KPFM) showed that the surface potential was shifted to the depths of the oxide film, and the work function value of the material surface was 4.54 eV, which is significantly lower compared to those reported in the literature. The electronic state of the elements in the NiCo2O4 film under study was analyzed by X-ray photoelectron spectroscopy (XPS). Chemosensor measurements showed that the printed receptor layer exhibited selectivity and high signal reproducibility for ethanol detection. As the relative humidity increases from 0 to 75%, the response value is reduced; however, the sensor response profile and signal-to-noise ratio remain without significant changes.

Multiplexed Gas Sensor: Fabrication Strategies, Recent Progress, and Challenges

“…In another research, Simonenko et al synthesized and evaluated NiCo 2 O 4 functional ink for its ability to detect ethanol gas. The sensor displayed a 54% response at 300 °C, while at 275 °C, the response was significantly higher at 123% . Similarly, Mokrushin et al produced Pt-decorated ZnO functional ink and used a microplotter technique to detect benzene gas on an Al 2 O 3 substrate .…”

Microplotter Printing of a Miniature Flexible Supercapacitor Electrode Based on Hierarchically Organized NiCo2O4 Nanostructures

“…This, in turn, contributes to increasing electrochemical activity and capacitance of electrodes, improving their microstructural stability during cyclic charging–discharging. According to the literature, one of the most promising and popular methods for obtaining hierarchically organized oxide nanostructures is hydrothermal synthesis, which enables the formation of the widest range of different morphologies: hollow spheres [ 31 ], nanotubes, nanofibers and nanorods [ 25 , 32 , 33 , 34 ], nanosheets and plate-like structures [ 35 , 36 , 37 ], or nanoflowers [ 26 , 38 , 39 ], both as nanopowders and as coatings. At the same time, a number of papers [ 40 , 41 ] note the high potential of the NiCo 2 O 4 microstructure, consisting of nanorods organized in the form of spheres (“urchin-like” microstructure), with respect to improving the electrochemical characteristics of their supercapacitor electrodes (high specific capacitance values, low charge transfer resistance, and increased cyclic stability).…”

The Impact of Annealing Treatment on Ethanol Gas Sensing Performance of SnO2 Nanoflakes

“…Furthermore, ethanol sensors are commonly used in breathalyzer devices to measure the alcohol content in a person's breath. 2,3 Among the different kinds of sensors, the chemiresistive-type sensing technique is receiving attention due to its low-cost, ease of manufacturing, compact design and easy-to-use measurement system. 4,5 In chemiresistive devices, metal oxide semiconductors including SnO 2 , ZnO, TiO 2 , WO 3 , In 2 O 3 and CuO as active sensing materials have attracted significant interest due to their high response, facile production, low cost, and compact size.…”