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We designed and controllably prepared ZnO/ZnFe2O4 with a novel Janus hollow nanofiber (ZnO/ZFO JHNF) structure as an efficient photocatalyst. First, Fe­(NO3)3/Zn­(NO3)2/PVP composite nanofibers were prepared by an electrospinning technique. Next, ZnO layers were layer by layer deposited on the above nanofibers via the atomic layer deposition (ALD) method, forming Fe­(NO3)3/Zn­(NO3)2/PVP@ZnO nanofibers. Then, ZnO/ZFO JHNFs with uniform heterostructural distributions were obtained after calcination. The ratio of ZnO to ZnFe2O4 in the Janus structure, which affected the internal electric field, could be controlled by adjusting the ALD cycle numbers of the ZnO layers. The Janus hollow structure could efficiently separate the photogenerated carriers, as well as the surface reduction and oxidation processes. For the degradation of methylene blue under visible light, the apparent first-order rate constant (k app) of the ZnO/ZFO JHNFs was about 2 and 17 times greater than those of electrospun ZnO/ZnFe2O4 nanofibers with randomly distributed heterojunctions and pure ZnFe2O4 hollow nanofibers (ZFO HNFs). The effect of the Janus heterojunctions was also experimentally studied by using Al2O3 as a barrier layer between ZnFe2O4 and ZnO, forming ZnO/Al2O3/ZnFe2O4 hollow nanofibers with a sandwich structure (ZnO/Al2O3/ZFO SHNFs). The k app of ZnO/Al2O3/ZFO SHNFs was only 1/12 that of ZnO/ZFO JHNFs and only slightly higher than that of ZFO HNFs, suggesting that the electron transfer process in the Janus heterojunction was the key for promoting the photocatalytic performance. Moreover, the ZnO/ZFO JHNFs could be easily separated under magnetic field after the photocatalytic tests due to the ferromagnetic property of ZnFe2O4. The ZnO/ZFO JHNFs with good solar light utilization and magnetically separable ability may be suitable for application prospects in the environmental restoration and energy conversion fields. Moreover, the oxide-based Janus heterojunctions may provide new ideas for designing novel photocatalysts with high efficiencies.

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Z-scheme narrow bandgap heterojunctions could efficiently absorb solar light and provide high reduction and oxidation ability for photocatalysis. However, it is difficult to tune the Z-scheme interface charge transfer to...

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.