Reversible down-regulation and up-regulation of catalytic activity of poly(N-isopropylacrylamide)-anchored gold nanoparticles

2022 ◽  
Author(s):  
Yufen Han ◽  
Jiaqian Li ◽  
Xiaojin Zhang ◽  
Fan Xia ◽  
Yu Dai

Abstract Regulating catalytic activity plays an important role in further optimizing and developing multifunctional catalysts with high selectivity and high activity. Reversible dual regulation of catalytic activity has always been a challenging task. Here, we prepared poly(N-isopropylacrylamide)-anchored gold nanoparticles (AuNP@CDs-Azo-PNIPAM) through host-guest interaction of cyclodextrin capped gold nanoparticles (AuNP@CDs) and azobenzene-terminated poly(N-isopropylacrylamide) (Azo-PNIPAM). Azo-PNIPAM as thermal and light responsive ligand allows reversible dual regulation of catalytic activity. When the temperature is higher than the lowest critical solution temperature (LCST), the PNIPAM chain shrinks rapidly, increasing the steric hindrance around AuNPs and reducing the catalytic activity. Under ultraviolet light irradiation, cis-azobenzene disassembles from cyclodextrin and the number of surface active sites of AuNPs increases, which improves the catalytic activity. The reaction rate of UV irradiation is almost 1.3 times that of visible light irradiation. This work provides a simple and effective strategy for the construction of reversible catalysts.

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4066
Author(s):  
David Herrera Robalino ◽  
María del Mar Durán del Amor ◽  
Carmen María Almagro Gómez ◽  
José Ginés Hernández Cifre

The adsorption of the thermoresponsive positively charged copolymer poly(N-isopropylacrylamide)-block-poly(3-acrylamidopropyl)trimethylammonium chloride, PNIPAAM48-b-PAMPTMA6(+), onto negatively charged gold nanoparticles can provide stability to the nanoparticles and make the emerging structure tunable by temperature. In this work, we characterize the nanocomposite formed by gold nanoparticles and copolymer chains and study the influence of the copolymer on the expected aggregation process that undergoes those nanoparticles at high ionic strength. We also determine the lower critical solution temperature (LCST) of the copolymer (around 42 °C) and evaluate the influence of the temperature on the nanocomposite. For those purposes, we use dynamic light scattering, UV-vis spectroscopy and transmission electron microscopy. At the working PNIPAAM48-b-PAMPTMA6(+) concentration, we observe the existence of copolymer structures that trap the gold nanoparticles and avoid the formation of nanoparticles aggregates. Finally, we discuss how these structures can be useful in catalysis and nanoparticles recovery.


2010 ◽  
Vol 663-665 ◽  
pp. 1049-1052
Author(s):  
Xin De Tang ◽  
Xin Wang ◽  
Yuan Yuan Dou

A serious of triply-responsive poly(N,N-dimethylaminoethyl methacrylate) (PMAEMA) containing an azobenzene group as the terminal group were synthesized by atom transfer radical polymerization (ATRP). The ATRP process of DMAEMA was initiated by an azobenzene derivative substituted with a 2-bromoisobutyryl group (Azo-Br) using CuCl/Me6TREN as catalyst and the mixture of DMA and H2O (v/v = 3:1) as solvent. The molecular weights and their distributions of the resulting homopolymers (Azo-PDMAEMA) were characterized by gel permeation chromatography (GPC). The polymers are soluble in aqueous media and exhibit a lower critical solution temperature (LCST) that alternated reversibly in response to pH and photoisomerization of the terminal azobenzene moiety. It was found that the LCST increased as pH decreased in the range of testing. Under UV light irradiation, the trans-to-cis photoisomerization of the azobenzene moiety resulted in a higher LCST, while it recovered under visible light irradiation.


2014 ◽  
Vol 955-959 ◽  
pp. 647-650
Author(s):  
Yu Liang Zhao ◽  
Lan Xiang Hou ◽  
Li Zhou ◽  
Wen Zhi Zhang

In this paper, propylene oxide has been first used to modify octylpolyglycol phenylene phosphite (OPGPP). A novel thermoregulated ligand OPGPP-Rh was synthesized for enlarging the application range of thermoregulated phase separable catalysis (TPSC) proposed by us. The ligands being studied have distinct critical solution temperature (CST) in some organic solvents. The CST of OPGPP (EO+PO=26+6) is 70°C in heptane. The authors further investigated the catalytic activity, separation and recycling efficiency of rhodium complex for hydroformylation of 1-octene in the catalytic system with CST. The optimal reaction conditions were as follows: T=100 °C, p=6.0MPa, CO:H2=1:1, reaction time of 5 hours, n (substrate to Rh)=1000, the solvent of heptane. Under the above conditions, the conversion of 1-octene and yield reached 90% and 88%, respectively. The catalyst could be recycled for five times without obvious loss in catalytic activity.


Soft Matter ◽  
2021 ◽  
Author(s):  
M. Ali Aboudzadeh ◽  
Joscha Kruse ◽  
Maria Sanromán-Iglesias ◽  
Daniele Cangialosi ◽  
Ángel Alegría ◽  
...  

The colloidal stability of metal nanoparticles is tremendously dependent on the thermal behavior of polymer brushes. Neat polyethylene glycol (PEG) presents an unconventional upper critical solution temperature in ethanol, where...


2020 ◽  
Vol 10 (20) ◽  
pp. 6935-6947
Author(s):  
P. Gairola ◽  
Y. Millot ◽  
J.-M. Krafft ◽  
F. Averseng ◽  
F. Launay ◽  
...  

The combination of spectroscopically characterized bulk- and surface-active zirconium sites makes Zr-MOF crystals efficient catalysts for alcohol dehydrogenation under mild conditions.


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