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

Abstract

effectively used for multifunctional applications ranging from light-weight space technologies, high-temperature fl exible sensors to stretchable implants on or into human bodies. [ 1b , 5 ] The utilization of Q1D nanostructures from metal oxide semiconductors (ZnO, Fe 2 O 3 , Al 2 O 3 , TiO 2 , etc.) as building units of macroscopic 3D networks is advantageous due to the fact that mechanical fl exibility and excellent electrical/sensing properties [ 3a , 4a , 6 ] of these Q1D nanostructures may be additionally implemented in the 3D networks. The successful fabrication of such multifunctional 3D networks is still a very challenging task and simply not possible with every nanowire synthesis technique. A variety of growth methods starting from conventional vapor-liquid-solid [ 7 ] to advanced lithography [ 8 ] techniques has been utilized for synthesizing the Q1D nanostructures from several metal oxides in different forms, but they still lack with key issues, e.g., appropriate integration, formation of fl exible networks, and others with regard to device applications. To overcome latter integration diffi culties, different strategies for direct fabrication of Q1D nano-and microstructures on microchips have been investigated and the corresponding devices have demonstrated high performances, too. [ 9 ] The 3D fl exible networks made from Q1D nanostructures, in this context, could become better alternates for an easy and direct realization of applications based on the nanoscale materials. However, typical availability of simple, cost-effective, and versatile synthesis techniques of fl exible networks, which is an equally important aspect amongst other listed above, is still not reported extensively.For the fabrication of macroscopic 3D interconnected nanowire networks, some advanced and multistep fabrication techniques have already been utilized. [ 10 ] Although these methods have shown their abilities to fabricate macroscopic 3D networks, they still involve high cost and complex synthesis steps which limit the mass scale production of such networks and hence their appropriate applications. In this regard, the fl ame transport synthesis (FTS) [ 4b ] approach demonstrated an enormous potential for metal oxide nanostructuring in a versatile and cost-effective manner. Structures ranging from singlecrystal ZnO nanoscale rods to centimeter size 3D interconnected network consisting of ZnO nano-and microtetrapods have been successfully synthesized by the FTS approach. The 3D networks have shown various possible and very promising applications in different fi elds. [ 11 ]

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

“…The lower gas response of these samples can be explained by the lower density of CuO NWs on the surface of particles and a smaller aspect ratio (see Fig. 1a-c) decreasing the possibility of interconnections and junctions between NWs and thus the overall concentration of adsorbed oxygen on their surfaces [9][10][11]. Figure 3b shows the dependence of the gas response (to EtOH, H 2 , CO and CH 4 ) on the operating temperature of the sensor structure for samples annealed at 425 °C, and demonstrates the bell-shape gas response, which is quite common for sensors based on semiconducting oxides [4].…”

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

“…It is therefore possible to improve the adsorption of gas molecules on the oxide surface and accelerate the oxidizing process [16,19,21]. Extensive studies were performed on the development of ultra-fast responding and recovering gas sensors based on doped oxide semiconductors [2,3,14,[26][27][28][29][30]. However, the high operating temperatures (400-450°C) for such gas sensors limit their possibilities in some applications, since they require higher power consumption for the heating element.…”

Rapid switching and ultra-responsive nanosensors based on individual shell–core Ga2O3/GaN:O @SnO2 nanobelt with nanocrystalline shell in mixed phases

“…The experiments were performed in a temperature interval from 30 to 300 K, the samples being mounted in the ARS-DE-202 optical cryogenic system as describe previously. [43,48] 3. Results and discussion…”

“…[43] The @Ga 2 O 3 /GaN:O x shells on SnO 2 nano-and microbelts/wires have been prepared directly on the tin oxide networks by RF A c c e p t e d M a n u s c r i p t 6 magnetron sputtering in a high vacuum chamber equipped with a turbomolecular pump and a mechanical pump. The samples were mounted on a rotary support, and the distance from the target to the substrate was 8 cm.…”

“…For investigation of sensing performances, a sensor was placed in a measuring apparatus as described below and in our previous works. [43,48,62] The photodetection performances of an as-grown and annealed individual nanowire individual nano-or micro-cable photodetectors at 10 V as UV radiation was switched on and off periodically. According to the experimental data presented in Figure 6(b-c), it is obvious that dynamic responses of these shell@core Ga 2 O 3 /GaN:O x @SnO 2 nano-and micro-cables photodetectors were quite stable over the whole lifetime of the device.…”