Room-Temperature Super Hydrogel as Dye Adsorption Agent

Supramolecular hydrogels were prepared in the mixtures of a chiral amphiphilic lithocholic acid (LCA) and a nonionic surfactant, dodecyldimethylamine oxide (C₁₂DMAO), in water. With the addition of LCA to C₁₂DMAO micellar solutions, a transition from micelles to gels occurs at room temperature. Hydrogels can form at very low concentrations (below 0.1 wt %), exhibiting a super gelation capability. The rheological measurements show a strong mechanical strength with an elastic modulus exceeding 5000 Pa and a yield stress exceeding 100 Pa. Microstructures determined by TEM, SEM, and AFM observations demonstrate that the gels are formed by intertwined helical fibrils. The formation of fibrils is induced by enormous cycles of units composed of two LCA molecules and four C₁₂DMAO molecules driven by comprehensive noncovalent interaction, especially the hydrogen bonds produced in two reversed LCA molecules and the C₁₂DMAOH⁺–C₁₂DMAO pairs. The xerogels show excellent adsorption capability of the toxic dye with a maximum adsorption value of 202 mg·g^–1

Fluorescent Hydrogels with Tunable Nanostructure and Viscoelasticity for Formaldehyde Removal

Hydrogels with ultrahigh water content, ∼99 wt %, and highly excellent mechanical strength were prepared by 4′-<i>para</i>-phenylcarboxyl-2,2′:6′,2″-terpyridine (PPCT) in KOH aqueous solution. The self-assembled structure, rheological properties, and the gel–sol transformation temperature (<i>T</i>_gel–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 (<i>R</i>_h) 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 <i>R</i>_h 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

Hydrogels Facilitated by Monovalent Cations and Their Use as Efficient Dye Adsorbents

Gelation behavior of lithocholate (LC^–) mixed with different monovalent cations in water was detected. The hydrogels consisting of tubular networks were formed by introducing alkali metal ions and NH₄⁺ to lithocholate aqueous solutions at room temperature. The formation of tubular structures was considered to be mainly driven by the electrostatic interaction with the assistance of a delicate balance of multiple noncovalent interactions. It is interesting that the increase in temperature can induce a significant enhancement in strength of the hydrogels, accompanied by the formation of bundles of tubules and larger size aggregates. The mechanism of the temperature-induced transition can be explained by the “salting-out” effect and the electric double layer model. The hydrogels showed very high adsorption efficiency and adsorption capability for the cationic dyes and were promising to act as toxic substance adsorbents

Multiple DNA Architectures with the Participation of Inorganic Metal Ions

Here we develop a synthetic protocol for assembling DNA with participating metal ions into multiple shapes. DNA molecules first form coordination complexes with metal ions and these coordination complexes become nucleation sites for primary crystals of metal inorganic salt, and then elementary units of space-filling architectures based on specific geometry form, and finally elementary units assemble into variously larger multiple architectures according to different spatial configurations. We anticipate that our strategy for self-assembling various custom architectures is applicable to most biomolecules possessing donor atoms that can form coordination complexes with metal ions. These multiple architectures provide a general platform for the engineering and assembly of advanced materials possessing features on the micrometer scale and having novel activity