Nano Ceria as Xylene Sensor: Role of Cerium Precursor

Research summary

Xylene is a toxic aromatic hydrocarbon released by petrochemical, printing, and related industries, and even short exposures can cause headaches, dizziness, and respiratory irritation. Many metal oxide sensors already exist for detecting it, but a large share of them need elevated operating temperatures to work well, which shortens the sensor’s usable life and adds power overhead. This study looks at cerium oxide (CeO2), a rare-earth metal oxide, as a room-temperature xylene sensor, and asks how the choice of cerium precursor used during film preparation affects the film’s structure and sensing behavior.

What the study examined

• CeO2 thin films spray-deposited on glass from three different cerium precursors: cerium acetate, cerium chloride, and cerium nitrate, with deposition conditions otherwise held constant.
• Crystal structure and crystallite size (X-ray diffraction), surface morphology (electron microscopy), and chemical composition (FTIR, X-ray photoelectron spectroscopy).
• Optical absorbance and band gap, calculated from the film’s light-absorption behavior.
• Room-temperature sensing response toward xylene, alongside selectivity checks against other vapors such as acetone, ethanol, and toluene.

Main findings

All three precursors produced polycrystalline CeO2 with the same cubic fluorite crystal structure, confirming that the underlying phase was not sensitive to precursor choice. What did change was morphology: the acetate precursor produced nanosheet-like assemblies with the smallest crystallite size, while the chloride and nitrate precursors produced differently shaped nanoparticles. Optical band gap also shifted with precursor choice, consistent with the differences in particle size and defect structure.

The acetate-derived film gave the clearest advantage as a sensor. Its smaller crystallites and higher surface-to-volume ratio provided more active sites for gas molecules to adsorb onto, which translated into a stronger response toward xylene. At room temperature, this film responded to xylene concentrations from 50 to 1000 ppm, with a response time of 224 seconds and a notably fast recovery time of 13 seconds. Compared with other xylene sensors reported in the literature — many of which operate at 150-400 degrees Celsius — the room-temperature operation stood out.

Why it matters

The study shows that precursor chemistry, not just the deposition technique, is a practical variable for tuning spray-pyrolysis metal oxide sensors. Because switching precursors requires no change in equipment or process, it offers a low-cost way to improve sensitivity and recovery speed. The room-temperature response toward xylene also points toward lower-power, longer-lived sensors for detecting this pollutant.