Construction of network-like cross-linked cellulose aerogel films with water-responsive properties for visualization of pH changes

Using epichlorohydrin as a cross-linking agent for cellulose and red radish pigment (R) as a pH-smart response indicator, a network-like cross-linked cellulose aerogel film (R-CEF) with water-responsive properties for visualizing pH changes was constructed by a simple method. In R-CEF, epichlorohydrin cross-linked cellulose aerogel film (CEF) as a smart responsive substrate provides a cross-linked structure with high porosity and good compatibility with R. XPS and FTIR structural analysis elucidate the objective fact of the existence of hydrogen bonds and intermolecular interactions between R and CEF. SEM showed that the addition of R changed the network cross-linked structure of CEF, making the original sponge structure into a layered structure after absorbing water, showing the intelligent response characteristics of R-CEF-7 in contact with water. The color change of the manufactured indicator (R-CEF-7) is evident from red to pink in acidic (pH=3 to pH=5) and from pink to yellow in alkaline (pH=10 to pH=13). Furthermore, R-CEF-7 showed good antibacterial properties and intelligent response characteristics to different pH values due to the contribution of R. This study provides new insights into the design and construction of pH-responsive and water-responsive cellulose-based smart composites.