A thermosensitive hydrogel carrier for nickel nanoparticles

• Thermosensitive p(NIPA-co-AMPS) hydrogel with good water absorptivity was prepared.
• Uniform Ni-NPs were prepared by in-situ reduction of Ni ions in hydrogel.
• The hydrogel network was exploited as reaction vessel in the aqueous reduction.
• The catalysis of Ni-NP can be modulated by a phase transition in hydrogel.

Segments of a p(NIPA-co-AMPS) hydrogel synthesized from N-isopropyl acrylamide (NIPA) and 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) with N,N′-methylenebis(acrylamide) (BIS) acting as cross-linker stabilized nickel nanoparticles (Ni-NPs) of uniform size in an aqueous solution. The rate of catalysis of the borohydride reduction of 4-nitrophenol to 4-aminophenol by these nanoparticles shows a complex temperature variation consistent with the hydrogel changing from a contracted to an expanded state below a lower critical solution temperature, LCST, of ~ 310 K. These observations provide insights into nanoparticle stabilization and catalysis and indicate potential pathways toward stable sophisticated nanoparticle catalysts for use in aqueous solution.

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