Fabrication of a highly enhanced H2S gas sensor via infusion of Ag nanoparticles into the inner grain boundaries of NiO nanofibers

초록

Nickel oxide (NiO) nanofibers were fabricated through an electrospinning-calcination methods using a polyvinylpyrrolidone (PVP) solution containing nickel(II) nitrate as the spinning precursor. After calcination process, the fibers exhibited a porous and polycrystalline morphology with an average fiber diameter of 100 nm and primary grain size of 10 nm. To evaluate their gas sensing performances, the nanofibers were employed as the channel material of chemoresistive type sensor devices patterned with interdigital electrode (IDE) with an inter-electrode gap of 50 mu m. The sensors were exposed to 0.1-10 ppm hydrogen sulfide (H2S). To maximize the sensing performance, silver nanoparticles were in situ incorporated by adding AgNO3 directly into the precursor solution, yielding Ag-decorated NiO nanofibers in a single step. Compared with pristine NiO nanofibers, the Ag-functionalized devices exhibited a six-fold enhancement in response: the resistance-based response (R-g/R-a) at 10 ppm H2S increased from 11.17 to 81.28, while the resexponse and recovery times were shortened by 55 s and 87 s, respectively. For comparison, Ag functionalization performed ex situ via sputtering and post-annealing afforded only a moderate response of 27.32 under the same conditions, underscoring the superiority of the one-step in situ approach that embeds Ag nanoparticles both inside and on the surface of the fibers. The Ag-decorated sensors also demonstrated robust humidity reliability (response >30 maintained at 80 % RH), excellent long-term stability within +/- 5 % variation over 30 days, and superior selectivity factors (2.96-16.86) against various interfering gases, confirming their practical suitability for H2S monitoring. These findings highlight a facile synthesis strategy and provide insight into the role of noble metal decoration in boosting the performance of NiO-based nanofiber gas sensors.

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