title: Fluorescent hydrogels with tunable nanostructure and viscoelasticity for formaldehyde removal.
abstract: Hydrogels with ultrahigh water content, ∼99 wt %, and highly excellent mechanical strength were prepared by 4'-para-phenylcarboxyl-2,2':6',2″-terpyridine (PPCT) in KOH aqueous solution. The self-assembled structure, rheological properties, and the gel-sol transformation temperature (Tgel-sol) of PPCT/KOH hydrogels that depend on PPCT and KOH concentrations were studied, indicating easily controllable conditions for producing hydrogels in PPCT and KOH mixtures. An important finding was that the hydration radius (Rh) of cations (M(+) = Li(+), Na(+), K(+), Cs(+), NH4(+), (CH3)4N(+), (CH3CH2)4N(+), (CH3CH2CH2)4N(+), (CH3CH2CH2CH2)4N(+)) plays a vital role in gelation of PPCT/MOH systems. To produce hydrogels in PPCT/MOH systems, the Rh of M(+) must be in a suitable region of 3.29 to 3.58 Å, e.g., K(+), Na(+), Cs(+), and the capability of M(+) for inducing PPCT to form hydrogels is K(+) > Na(+) > Li(+), which is followed by the Hofmeister series. The hydrogels of PPCT and KOH mixtures are responsive to external stimuli including temperature and shearing force, and present gelation-induced enhanced fluorescence emission property. The states of being sensitive to the stimuli can readily recover to the original hydrogels, which are envisaged to be an attracting candidate to produce self-healing materials. A typical function of the hydrogels of PPCT and KOH mixtures is that formaldehyde (HCHO) can speedily be adsorbed via electrostatic interaction and converted into nontoxic salts (HCOOK and CH3OK), making it a promising candidate material for HCHO removal in home furnishings to reduce indoor environmental pollutants.
authors.affiliation: Key Laboratory of Colloid and Interface Chemistry & Key Laboratory of Special Aggregated Materials, Shandong University , Ministry of Education, Jinan 250100, China.
authors.forename: Shasha
authors.initials: S
authors.lastname: Song
authors.forename: Aixin
authors.initials: A
authors.lastname: Song
authors.forename: Lei
authors.initials: L
authors.lastname: Feng
authors.forename: Guangcheng
authors.initials: G
authors.lastname: Wei
authors.forename: Shuli
authors.initials: S
authors.lastname: Dong
authors.forename: Jingcheng
authors.initials: J
authors.lastname: Hao
keywords: HCHO removal; Hofmeister series; mechanical strength; molecular self-assembly; stimuli-responsive; viscoelastic hydrogels