Speaker
Description
Ntokozo G. Cebekhulua, Ceboliyazakha L. Ndlangamandlaa, Prince S.Mkwaea, Donald D. Hilea,b, Sipho E. Mavudlac, Siphamandla C. Masikanec
aDepartment of Physics, University of Zululand, Private Bag X1001, KwaDlangezwa ZA3886, South Africa
bDepartment of Physics, Joseph Sarwuan Tarka University, Makurdi, Nigeria
cDepartment of Chemistry, University of Zululand, Private Bag X1001, KwaDlangezwa ZA3886, South Africa
*Correspondence: ntokozongc200@gmail.com
Abstract
Hematite nanoparticles (HNPs) doped with rare earth ions (Sm, La, and Dy) were synthesized successfully using a cost-effective and environmentally friendly co-precipitation method. A variety of characterization techniques were employed to examine the structural, morphological, and optical properties of the materials, as well as the influence of doping. X-ray diffraction confirmed that the HNPs crystallize in a hexagonal rhombohedral structure within the R3c space group. Crystallite sizes were estimated using the Scherrer equation, yielding values of 46, 25, 33, and 30 nm, respectively. SEM analysis, combined with energy-dispersive X-ray spectroscopy (EDS), revealed the surface morphology and elemental composition. While undoped hematite displayed spherical particles, the doped samples exhibited morphological variations depending on the rare-earth ion incorporated.Optical properties were investigated using UV-Vis spectroscopy, with band gaps determined via the Tauc plot method. The measured band gaps were 2.135, 2.285, 2.495, and 2.445 eV, respectively. Undoped hematite showed lower band gaps compared to the doped samples, confirming that rare-earth doping significantly alters the optical behavior of the material. FT-IR spectroscopy was employed to identify functional groups and chemical bonding, while BET analysis provided information on specific surface area, pore size, and pore volume.Gas-sensing studies demonstrated that Sm-doped HNP sensors exhibit superior performance, achieving a sensitivity of 133 towards hydrogen sulfide (H₂S) gas at 175 °C. Stability tests conducted over seven days showed that the sensor maintained reliable performance at lower H₂S concentrations but became unstable at higher concentrations. Humidity was found to negatively affect sensitivity and selectivity. Repeatability tests confirmed sharp memory and consistent detection of 150 ppm H₂S. The limit of detection (LOD) was determined to be 0.1 ppm, which complies with NIOSH guidelines.In summary, the results highlight that synthesis conditions, rare-earth doping, and optimal operating temperature are critical factors influencing the performance of HNP-based gas sensors.
Keywords: Optimal temperature of the sensor, Doping, Sensitivity, Humidity, Response, and recovery time
| Apply for student award at which level: | PhD |
|---|---|
| Consent on use of personal information: Abstract Submission | Yes, I ACCEPT |