Temperature- and pH-Responsive Hydrogel Nanoparticles with Embedded Au Nanoparticles as Catalysts for the Reduction of Dyes

Abstract

Here, we report a facile design and synthesis of Au nanoparticle (Au NP)-immobilized poly­(N-isopropylacrylamide-co-methacrylic acid) hydrogel nanoparticles, also referred to as hybrid microgels (Au-MGs), by employing in situ reduction of Au­(III) ions in a nanoscale polymeric network. This approach offered formation of controlled size Au NPs within the microgels with an average particle size as low as 3.3 ± 0.9 nm. The prepared hybrid microgels were shown to possess an excellent catalytic activity in the degradation of a cationic dye, methylene blue (MB). The embedded Au NPs were remarkably stable against self-aggregation thanks to the particle trapping within the polymeric network, and thus, the particles maintained their outstanding catalytic performance over a period of time. On account of the dual-responsive nature of the microgels, a tuneable catalytic activity could be achieved by adjusting the temperature and pH value of the experiments. Furthermore, other reaction parameters such as catalyst dosage, initial dye concentration, and ionic strength strongly influenced the catalytic performance of this heterostructure catalyst. The Au-MG hybrid exhibited a higher rate of MB reduction under the high Au-MG concentration (0.14 mg/mL), low MB concentration (0.05 mM), alkaline medium (pH 11), low ionic strength (no added salt), and low temperature (20 °C). The reusability of the catalyst was found to be fair enough, making it an excellent cost-effective material for dye degradation. Our strategy used herein to prepare Au-based multifunctional hybrid materials with high catalytic performance could open up new avenues for the sustainable development of materials in wastewater treatment.

Nanogels Containing Gold Nanoparticles on Cotton Fabrics for Comfort Control via Localized Surface Plasmon Resonance

“…However, the size of the hybrid nanogels containing Au NPs slightly reduces to 400 ± 50 nm. The minor decrease in particle size can be attributed to the electrostatic attraction between Au NPs and nanogel networks, which induces a slight shrinkage of the nanogels. ,, To further probe the internal structure of pure and hybrid nanogels, both are measured by TEM as well. Compared with pure nanogels showing a homogeneous structure (Figure c), a large number of small particles are observed in the hybrid nanogels (Figure d).…”

“…The preparation of hybrid nanogels containing Au NPs was according to earlier work . The nanogels were first centrifuged at 10,000 rpm for 30 min.…”

“…The preparation of hybrid nanogels containing Au NPs was according to earlier work. 32 The nanogels were first centrifuged at 10,000 rpm for 30 min. Afterward, the nanogels (40 mg) were added into a HAuCl 4 − 3H 2 O aqueous solution (40 mL, 0.1 mg mL −1 ) and stirred at 25 °C for 2 h. Then a NaBH 4 solution (1 mL, 2 mg mL −1 ) was added to the reaction mixture.…”

Fluorescent Noncovalent Organic Framework for Supporting Gold Nanoparticles as Heterogeneous Catalyst with Merits of Easy Detection and Recycle

“…(Figure 5b) AuNPs@CMC-TPEA also exhibits good catalytic activity on the reduction of methylene blue, toluidine blue, and rhodamine B by NaBH 4 , indicated by their UV-Vis absorption changes. [50,51] (Figure S20-S22, Supporting Information) By comparison with the noncatalyzed reactions, methylene blue, toluidine blue, and rhodamine B could gain higher conversions (>90%) in shorter reaction times. (Table 2, Entry 2-4) The catalytic activity of AuNPs@CMC-TPEA on the hydrogenation of uranine was also tested.…”

Green Synthesis of Gold Nanoparticles for Catalytic Reduction of 4-Nitrophenol and Methylene Blue for Sustainable Development

“…These pollutants are residues of the manufacture of herbicides, insecticides, and synthetic fibers, and have been designated as priority pollutants by the US Environmental Protection Agency (EPA) owing to their toxicity. GNPs have shown higher catalytic activity at decreasing the concentrations of these pollutants than typical catalysts [43,44]. And GNPs could be repeatly utilized for many times due to the simplicity of extraction as catalysts.…”