Response of inverse-opal hydrogels to alcohols

Abstract

A polyacrylamide inverse-opal hydrogel (IOH PAM ) film was synthesized by in situ polymerization in a polystyrene colloidal crystal template. The IOH PAM has a periodically ordered interconnecting porosity that endows the film with a band gap and structural color. The IOH PAM film exhibits a rapid reversible change in volume and in refractive index in response to alcohols and, consequently, the structural color and reflection peak of the IOH PAM film are quickly synchronized with these changes. The reflection peak of the IOH PAM film shows obvious blue or red-shifts that depend on the structure of the alcohols. The extent of the shift not only depends on the number of -OH groups, but also on the chain length, structure and concentration of the alcohols. The IOH PAM film is also sensitive to polyethylene glycol (PEG) and displays different blue-shift responses to PEGs with different molecular weights. Since the IOH PAM films have different reflectance spectra and structural colors in response to different types and concentrations of alcohols, this provides a potential way to visually detect alcohols.

Photonic Crystal Based Sensor for Organic Solvents and for Solvent-Water Mixtures

“…However, an arrangement of four differently functionalized inverse opal films is necessary in order to detect mixtures in the 85 to 100% ethanol range with a precision of 5% (which is moderate anyway). In yet another approach [26], an inverse opal polyacrylamide film was applied to sense the fraction of alcohols, but these PhCs also contain water and therefore cannot be used to detect small water fractions in almost pure alcohols. We believe that the sensing scheme presented here is not limited to the species and mixtures investigated here, but also envision that such (or similar) sensor films would enable the detection of traces of water in gasoline fuels.…”

“…The system described by Pan et al . [26], (which is based on a polyacrylamide hydrogel inverse opal) also was used for the identification of various ethanol-methanol mixtures. However, it is limited by the fact that neither pure ethanol nor pure methanol can be detected.…”

Cellulose photonic crystal film sensor for alcohols

“…Recently, colloidal arrays incorporated with hydrogel have been reported for the sensing of alcohols [10,17,18]. For example, Zeng et al developed a polyacrylamide inverse opal hydrogel to detect liquid alcohols [19]. However, the inverse opal hydrogels were synthesized by the templated hydrogel preparation, which uses colloidal array as nanoscale template at first, and then etches away the template to obtain an interconnected porous structure.…”

Responsive photonic crystal for the sensing of environmental pollutants

“…In general, PhCs are composed of a periodic arrangement of regularly shaped materials with different dielectric constants, and have a photonic band gap (PBG) in which light cannot propagate and can only diffract or reflect. If the PBG is located in the visible light region, the iridescent structural color exhibited by PhCs can be observed by naked eye [9,10].…”