Search

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. [ABSTRACT FROM AUTHOR]

We developed a simple and efficient method to construct 3D and 2D opal and inverse opal cellulose photonic crystal films (CPCF) by embedding 3D or 2D polymethyl methacrylate (PMMA) colloidal arrays into carboxymethyl cellulose (CMC), respectively. The morphology and optical performance of CPCFs were characterized by SEM, diffraction spectra, Debye rings, and structural color. The brilliant structural colors of CPCFs are visible to the eye in the entire visible spectrum, and can be tuned by changing the particle diameters or the pore sizes. Attributed to decreased particle spacing and lower average refractive index caused by air spheres instead of polymer spheres, the stopbands of the inverse opal CPCFs blue-shifted. To the contrary, the particle spacing of 2D inverse opal CPCFs increased due to the losing of the connection force of 2D arrays, along with decreasing of Debye ring diameters. By alternately being exposed to organic solvents of methanol, acetonitrile, butanol, dioxane, and carbon tetrachloride, the 3D inverse opal CPCFs displayed an excellent sensing performance with instantaneously reversible color changes from violet to red. Their high stability and flexibility, efficient visual detection, and wide range of analytes promises a new opportunity for optical switching and sensing applications. [ABSTRACT FROM AUTHOR]

A novel hydrogel film with a highly ordered macropore monolayer on its surface was prepared by templated photo-polymerization of hydrogel monomers on a two-dimensional (2D) polystyrene colloidal array. The 2D inverse opal hydrogel has prominent advantages over traditional three-dimensional (3D) inverse opal hydrogels. First, the formation of the 2D array template through a self-assembly method is considerably faster and simpler. Second, the stable ordering structure of the 2D array template makes it easier to introduce the polymerization solution into the template. Third, a simple measurement, a Debye diffraction ring, is utilized to characterize the neighboring pore spacing of the 2D inverse opal hydrogel. Acrylic acid was copolymerized into the hydrogel; thus, the hydrogel responded to pH through volume change, which resulted from the formation of the Donnan potential. The 2D inverse opal hydrogel showed that the neighboring pore spacing increased by about 150 nm and diffracted color red-shifted from blue to red as the pH increased from pH 2 to 7. In addition, the pH response kinetics and ionic strength effect of this 2D mesoporous polymer film were also investigated. [ABSTRACT FROM AUTHOR]

A colorimetric sulfur dioxide (SO 2 ) 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 (SiO 2 @MCM-41), and further loaded with a mixture of zinc chloride (ZnCl 2 ), sodium nitroprusside (SNP) and hexamine as an SO 2 indicator. The sensing properties of SiO 2 @MCM-41 toward SO 2 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 SO 2 . The limit of detection (LOD) is 2 ppm for SiO 2 @MCM-41 discs, which indicates high sensitivity to SO 2 . The performance of GDT suggested a linear relationship between the SO 2 concentration and the response length of the red portions in a range of 100-1000 ppm. This work shows promising potential of SiO 2 @MCM-41 as an easy, effective and rapid response sensing material for the in situ detection of SO 2 .