Equipment-free chromatic determination of formaldehyde by utilizing pararosaniline-functionalized cellulose nanofibrous membranes

Determination of environmental contaminants such as trace formaldehyde mostly relies on bulky and costly analytical equipment. However, a particular demand for portable, rapid, and sensitive method that can be used in resource-limited settings has received paramount concern. Towards this need, we are presenting here a rational design of colorimetric sensor strips using electrospun cellulose nanofibrous membrane-immobilized pararosaniline. Based on the specific reaction between formaldehyde and pararosaniline, the strips could undergo a distinct color transition from light pink to purple, specifically in the presence of trace-level formaldehyde over other possible interferential volatile organic compounds. Benefiting from the large specific surface area and high porosity of nanofibrous membranes, the strips achieved ultralow naked eye detection limit of 0.06   mg   m −3 (below the regulatory level of 0.1   mg   m −3 ), wide linear range from 0.12 to 6   mg   m −3 , and short response time (15   min) in the absence of advanced instrumentation. Additionally, the sensing responses were visualized quantitatively by HSI coordinates which are presented with lightness and chromatic values and analyzed by a principal component analysis method. Furthermore, the strips exhibited remarkably improved analytical performance compared to commercial filter paper-based ones. With its cost-effective design and portability, this sensitive and specific colorimetric strips could potentially be used for providing air contamination information.