Thermosensitive Au-PNIPA yolk-shell nanoparticles with tunable selectivity for catalysis.
ABSTRACT Selectivity in nanoreactors: A hybrid yolk-shell nanostructure that contains gold nanoparticles in the core and thermosensitive microgel poly(N-isopropylacrylamide) (PNIPA) as shell is presented. The catalytic selectivity of Au-PNIPA nanoparticles for the reduction of hydrophilic 4-nitrophenol and more hydrophobic nitrobenzene with NaBH(4) can be tuned through the volume transition of PNIPA shell.
- Zeitschrift für Physikalische Chemie 07/2012; · 1.18 Impact Factor
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ABSTRACT: Thermoresponsive core-shell microgels with degradable core are synthesized via surfactant based free radical polymerization using N,N'-(1,2-dihydroxy-ethylene)bis(acrylamide) (DHEA) as a cross-linker for core preparation. The 1,2-glycol bond present in DHEA is susceptible to NaIO4 solution, and thus, the structure can be cleaved off resulting in hollow microgel. Ultrathin membranes are prepared by suction filtration of a dilute suspension of core-shell microgels over a sacrificial layer of Cd(OH)2 nanostrand coated on track etched membrane. After removal of the degraded cores from microgels, the membranes are cross-linked with glutaraldehyde and the nanostrands are removed by passing a 10 mM HCl solution. The prepared membranes are thoroughly characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), dynamic light scattering (DLS), and dynamic contact angle for morphology, thermoresponsive, and hydrophilic properties, respectively. The prepared membranes showed thermoresponsive permeation behavior and remarkable separation performance for low molecular weight dyes and lysozyme protein. These membranes are also used to synthesize gold nanoparticles and immobilize lactate dehydrogenase enzyme for catalytic and biocatalytic application. The results for water permeation, solute rejection, and ability to immobilize gold nanoparticles and enzymes showed its wide range of applicability. Furthermore, the synthesis of hollow microgel is simple and environmentally friendly, and the membrane preparation is easy, scalable, and other microgel systems can also be used. These responsive membranes constitute a significant contribution to advanced separation technology.ACS Applied Materials & Interfaces 10/2014; · 5.90 Impact Factor
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ABSTRACT: Developing hydrogel systems featured by catalytic active is of importance to construct highly effective platforms for removing environmental pollutants/hazardous substances or for bio-/chemosensing. Reported herein are our recent finding that Au nanoparticles could be in situ prepared in chitosan-AuIII hydrogel system via photoreduction, and the as-prepared Au nanoparticles could be employed for the catalytic reduction of a series of nitroaromatic compounds by sodium borohydride (NaBH4). Experimental conditions of synthesizing Au nanoparticles, including pH, concentration of AuIII, and light irradiation time were systematically investigated. The as-prepared Au nanoparticles were characterized by UV–vis absorption spectroscopy, X-ray diffraction (XRD), transmission and field emission scanning electron microscopy (TEM and FESEM). This is the first example for in situ formed metal nanoparticles in chitosan hydrogel systems via photoreduction. The effectiveness of the as-prepared Au nanoparticles as nanocatalysts was evaluated by employing the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 as a model reaction. The catalytic reduction reaction was found to be very efficient and to follow a pseudo-first-order kinetics. The as-prepared Au nanoparticles demonstrated good reusability and stability. The reduction of a series of other nitroaromatic compounds including highly explosives 2,4,6-trinitrophenol (2,4,6-tNP) and 2,4,6-trinitrotoluene (2,4,6-tNT) was achieved by means of this catalytic system.Applied Surface Science 03/2015; 331. · 2.54 Impact Factor