Sm-doped SnO2 nanostructures for aqueous ammonia sensing application

This paper reports the synthesis of Sm-doped tin oxide nanostructures using a co-precipitation route to develop an aqueous ammonia sensor. The characterization of as-prepared samples was carried out by XRD, FESEM, FTIR, UV–Visible absorption spectroscopy, and energy-resolved photoluminescence, respectively. The crystallite size range is from 8 ± 0.4 nm to 17 ± 1 nm. All samples show nearly spherical morphology with a grain size range of 35–70 nm. FTIR spectra correspond to O–H, C=O, Sn-OH, and Sn–O–Sn functional groups, confirming the formation of SnO₂ nanostructures. The energy band gap varies from 2.71 eV to 3.09 eV. An increase in bandgap observed for 9at% Sm-doped SnO₂ nanostructures may be due to the Moss-Burstein effect. Photoluminescence studies show the increase in band-to-band and defect-related emission with the addition of a dopant and an increase in dopant concentration. Linear sweep Voltammetry of undoped and Sm-doped tin oxide nanostructures was done to develop an aqueous ammonia sensor. I-V characteristics show a rise in current for undoped and Sm-doped SnO₂ nanostructured layers when immersed in water containing ammonia. The analyte detection capability of the samples also increases with an increase in Sm-dopant (3% to 9%) as well as with analyte (NH₃) concentration (100 ppm to 500 ppm) in water.