An enhanced gas sensor based on SiO₂@mesoporous MCM-41 core-shell nanocomposites for SO₂ visual detection

A colorimetric sulfur dioxide (SO₂) gas sensor based on a core-shell composite was developed. The composite was fabricated with a silicon dioxide core and a mesoporous MCM-41 shell (SiO₂@MCM-41), and further loaded with a mixture of zinc chloride (ZnCl₂), sodium nitroprusside (SNP) and hexamine as an SO₂ indicator. The sensing properties of SiO₂@MCM-41 toward SO₂ were measured in solid powder, discs and a gas detection tube (GDT), respectively. Each of these sensing configurations showed a distinct color change from pale yellow to red, which indicates good potential for naked-eye detection of SO₂. The limit of detection (LOD) is 2 ppm for SiO₂@MCM-41 discs, which indicates high sensitivity to SO₂. The performance of GDT suggested a linear relationship between the SO₂ concentration and the response length of the red portions in a range of 100-1000 ppm. This work shows promising potential of SiO₂@MCM-41 as an easy, effective and rapid response sensing material for the in situ detection of SO₂.