Abstract
Although equipment-based gas sensor systems (e.g., high-performance liquid chromatography) have been widely applied for formaldehyde gas detection, pre-treatment and expensive instrumentation are required. To overcome these disadvantages, we developed a colorimetric sensor based on polymer-based core–shell nanoparticles (PCSNPs), which are inexpensive, stable, and exhibit enhanced selectivity. Spherical and uniform poly(styrene-co-maleic anhydride) (PSMA)/polyethyleneimine (PEI) core–shell nanoparticles were prepared and then impregnated with Methyl Red (MR), Bromocresol Purple (BCP), or 4-nitrophenol (4-NP) to construct colorimetric sensors for formaldehyde gas. The intrinsic properties of these dyes were maintained when introduced into the PCSNPs. In the presence of formaldehyde, the MR, BCP, and 4-NP colorimetric sensors changed to yellow, red, and gray, respectively. The colorimetric response was maximized at a PEI/PSMA ratio of four, likely owing to the high content of amine groups. Effective formaldehyde gas detection was achieved at a relative humidity of 30% using the MR colorimetric sensor, which exhibited a large color change (92%) in 1 min. Advantageously, this stable sensor allowed sensitive and rapid naked-eye detection of low formaldehyde concentrations (0.5 ppm). Hence, this approach is promising for real-time formaldehyde gas visualization and can also be adapted to other colorimetric gas sensor systems to improve sensitivity and simplicity.
Highlights
Colorimetric sensors are considered as potentially efficient detection methods for environmental monitoring of harmful gases, such as SOx, NOx, formaldehyde, and CO2
Indicator dye that undergoes a pH shift in the nanoparticles presence of In this study, doped a formaldehyde detector was developed based on poly(styrene-co-maleic anhydride) (PSMA)/PEI
It was found that the PEI/PSMA ratio influenced the structure of the core–shell nanoparticles
Summary
Colorimetric sensors are considered as potentially efficient detection methods for environmental monitoring of harmful gases, such as SOx , NOx , formaldehyde, and CO2. Equipment-based systems (e.g., HPLC and IC) typically require pre-treatment processes and expensive instrumentation, which complicates the detection of formaldehyde gas in real time [14,15,16,17,18] To overcome these disadvantages, researchers have suggested colorimetric pH sensors based on a solid matrix (e.g., polymer and sol–gel materials) and nanostructured particles. Immobilization by covalent binding requires the presence of appropriate functional groups and both the adsorption and entrapment methods are limited by leaching of the indicator dye [19] For this reason, various nanostructured particles (e.g., organic, inorganic, and hybrid materials) have been suggested as potential colorimetric pH sensors because of their high sensitivities, large surfaces, large volume ratios, and high specific surface areas [20,21,22,23,24,25]. The current work describes, for the first time, a core–shell-type PSMA/PEI sensor that acts as an efficient formaldehyde gas detection system that can be used as the basis for developing a colorimetric gas sensor
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