Flexible All‐Inorganic Room‐Temperature Chemiresistors Based on Fibrous Ceramic Substrate and Visible‐Light‐Powered Semiconductor Sensing Layer

Abstract

As the most extensively used gas-sensing devices, inorganic semiconductor chemiresistors are facing great challenges in realizing mechanical flexibility and room-temperature gas detection for developing next-generation wearable sensing devices. Herein, for the first time, flexible all-inorganic yttria-stabilized zirconia (YSZ)/In 2 O 3 /graphitic carbon nitride (g-C 3 N 4 ) (ZIC) gas sensor is designed by employing YSZ nanofibers as substrate, and ultrathin In 2 O 3 /g-C 3 N 4 heterostructures as active sensing layer. The YSZ substrate possesses small nanofiber diameter (310 nm), ultrafine grain size (23.9 nm), and abundant dangling bonds, endowing it with striking mechanical flexibility and strong adhesion with In 2 O 3 /g-C 3 N 4 sensing layer. Meanwhile, the ultrathin thickness (≈7 nm) of In 2 O 3 /g-C 3 N 4 ensures that the inorganic sensing layer has tiny linear strain along with the deformation of flexible YSZ substrate, thereby enabling unusual bending capacity. To address the operating temperature issue, the gas sensor is operated by using a visible-light-powered strategy. Under visible-light illumination, the flexible ZIC sensor exhibits a perfectly reversible response/recovery dynamic process and ultralow detection limit of 50 ppb to toxic nitrogen dioxide at room temperature. This work not only provides an insight into the mechanical flexibility of inorganic materials, but also offers a valuable reference for developing other flexible inorganic-semiconductor-based room-temperature gas sensors.

Recent Progress on Flexible Room-Temperature Gas Sensors Based on Metal Oxide Semiconductor

“…Several FRT gas sensors under light-illuminated have been reported [ 66 , 70 , 75 , 99 , 102 , 105 , 160 ]. The pristine ZnO is a direct bandgap semiconductor with a bandgap of 3.35 eV [ 228 ], thus it can be activated by UV-light and generate photo-generated electron–hole pairs to effectively lower the operating temperature.…”

State of the Art of Chemosensors in a Biomedical Context

“…Depending on the type of metal oxide and dopant used, a wide range of gases can be detected, but the downsides of the system are the high operating temperature and narrow range of detectable analytes. MOx based chemical sensors are used in the detection of obnoxious gases for the purpose of environmental monitoring SO 2 [37,[81][82][83], NO x [84][85][86], NH 3 [87,88], H 2 S [89], CO [90,91] hydrocarbons [detection of oil spills], and VOCs [volatile organic compounds]. Such sensors have been light-powered and realized on flexible substrates for the detection of NO 2 by ultrathin heterostructure configuration (see Figure 6).…”

Nature-inspired preparation of self-adhesive, frost-resistant, and ion-conductive hydrogels for flexible strain sensors

“…3,4 Traditional exible sensors are usually composed of a stretchable matrix and conductive components, and include conductive polymers, 5,6 carbon nanomaterials, 7,8 metal and metal oxide nanoparticles, 9,10 and semiconductors. 11,12 Flexible sensors are ready to withstand different deformations (such as tensile, bending, and compressive deformation) and convert different deformations into recognizable electrical signals based on changes in resistance or capacitance. Recently, conductive hydrogels display promising potential in the elds of wearable devices, 13 implantable biosensors, 14 and articial skin.…”