Versatile Growth of Freestanding Orthorhombic α-Molybdenum Trioxide Nano- and Microstructures by Rapid Thermal Processing for Gas Nanosensors

Abstract

We demonstrate a new technique that requires a relatively low temperature of 670–800 °C to synthesize in 10–20 min high crystalline quality MoO3 nano- and microbelts and ribbons. The developed technological process allows rapid synthesis of large amounts of MoO3 nano- and microsheets, belts, and ribbons, and it can be easily scaled up for various applications. Scanning electron microscopy (SEM) studies revealed that the MoO3 nano- and microbelts and ribbons are synthesized uniformly, and the thickness is observed to vary from 20 to 1000 nm. The detailed structural and vibrational studies on grown structures confirmed an excellent agreement with the standard data for orthorhombic α-MoO3. Also, such freestanding nano- and microstructures can be transferred to different substrates and dispersed individually. Using focused ion beam SEM, MoO3-based 2D nano- and microsensors have been integrated on a chip and investigated in detail. The nanosensor structures based on MoO3 nano- and microribbons are quite stable and moderately reversible with respect to rises and drops in ethanol vapors. It was found that MoO3 nano- and microribbons of various sizes exhibit different sensitivity and selectivity with respect to ethanol, methanol, and hydrogen gases. The developed technique has great potential for further studies of different metal oxides, nano- and microsensor fabrication, and especially for multifunctional applications.

Single and networked CuO nanowires for highly sensitive p-type semiconductor gas sensor applications

“…The experimental details on investigation techniques and gas sensing measurements are presented in text SI-2 from the Supporting Information. For the gas sensing measurements the fabricated devices were placed in a measuring apparatus as reported in our previous works [14,16,17]. Figure 1a-c and Supporting Information SI-1 show SEM images of thermally annealed Cu micro-particles (see Supplementary information SI-2a) at 400 °C, 425 °C and 450 °C for periods of 5 h. As can be observed, an annealing temperature of 425 °C yielded the highest density of very fine NWs on the surface of micro-particles with lengths up to 15 µm and diameters in the range of 20-90 nm.…”

“…More details on fabrication of nanodevices can be found in previous works [14,[27][28][29]. The connection configuration for electrical and gas sensing measurements is schematically presented in the inset of Fig.…”

Multifunctional device based on ZnO:Fe nanostructured films with enhanced UV and ultra-fast ethanol vapour sensing

“…Thus, rapid thermal annealing is an attractive technique from an industrial point of view, since it may be easily scaled-up to industrial production of gas sensors without the need of complicated vacuum systems. Additionally, it allows the speed up of production processes when combined with a simple chemical synthesis (SCS) approach from solutions [34].…”

Three‐Dimensional SnO2 Nanowire Networks for Multifunctional Applications: From High‐Temperature Stretchable Ceramics to Ultraresponsive Sensors

“…Initially, the oxygen molecules from the ambient air are chemisorbed onto the surface of the tin dioxide structures by capturing a free electron from the nano-and microwires/belts surface {(O 2(gas) → O 2(ads) ; O 2(ads) + e − ↔ O − 2(ads) ; O − 2(ads) + e − ↔ 2O − (ads) ; O − (ads) + e − ↔ O 2− (ads) )}. [ 28 ] It produces a decrease of majority charge carriers present in the tin dioxide near-surface regions. [ 29 ] When the SnO 2 sensor network is illuminated with UV radiation, then two processes take place.…”