Fabrication of thermo-responsive polymer functionalized reduced graphene oxide@Fe₃O₄@Au magnetic nanocomposites for enhanced catalytic applications

Abstract

Thermo-responsive copolymer functionalized RGO@Fe3O4@Au magnetic nanocomposites with high catalytic activity to reduce nitrophenols are fabricated and show excellent recyclability and controllable catalytic performance.

Modified Nanocarbons for Catalysis

“…A novel rGO‐based nanocomposite 132 was obtained by means of the synthetic strategy depicted in Scheme . First, the thermo‐responsive copolymer 128 was synthesized via a reversible addition fragmentation chain transfer (RAFT) polymerization starting from 2,3‐epithiopropyl methacrylate (ETMA) 125 , N ‐isopropylacrylamide (NIPAM) 126 , and using S ‐1‐dodecyl‐S′‐(α, α′‐dimethyl‐ α′′‐acetic acid) trithiocarbonate (DDAT) 127 as chain transfer agent (CTA).…”

Sub‐10 nm Ag Nanoparticles/Graphene Oxide: Controllable Synthesis, Size‐Dependent and Extremely Ultrahigh Catalytic Activity

“…Interestingly, in contrast to TOF m (Figure E), TOF a in this case shows a trend in the order of 6.2‐AgNPs/GO > 4.3‐AgNPs/GO > 2.5‐AgNPs/GO, wherein the reactivity decreases with decreasing AgNP size, as illustrated in Figure F. First, the electron concentration on NMNPs is among the most substantial issues that could affect their catalytic performances toward 4‐NP reduction, where a higher concentration facilitates the uptake of electrons and thus promotes superior catalytic reactivity, and vice versa . Second, smaller nanoparticles are generally expected to display higher catalytic performances than larger nanoparticles because their higher surface‐to‐volume ratio could generally provide them with more catalytically active sites .…”

“…On the other hand, as verified by the positively shifted Ag 3d binding energy from the 6.2 and 4.3 AgNPs to the 2.5 nm AgNPs, these facts suggest that GO could withdraw more electrons from AgNPs with decreasing particle size, leading to a depressed electron concentration on AgNPs from 6.2‐AgNPs/GO and 4.3‐AgNPs/GO to 2.5‐AgNPs/GO, as schematically illustrated in Figure G. As a result, compared to those in 6.2‐AgNPs/GO and 4.3‐AgNPs/GO, the AgNPs in 2.5‐AgNPs/GO are relatively electron‐deficient, disfavoring electron uptake by 4‐NP and thus resulting in their comparatively inferior catalytic performances, although their size is the smallest among our three composites. When our 6.2‐AgNPs/GO composites are taken into consideration, their higher and lower catalytic reactivity compared to those of 2.5‐AgNPs/GO and 4.3‐AgNPs/GO, respectively, could be a consequence of the competition between their relatively higher electron concentration and lower specific surface area (resulting from the comparatively lower surface‐to‐volume ratio of the 6.2 nm AgNPs), which favors and disfavors the catalytic performances, respectively.…”

“…The decreased shift degree toward the lower frequencies from 2.5‐AgNPs/GO (30 cm −1 ) and 4.3‐AgNPs/GO (14 cm −1 ) to 6.2‐AgNPs/GO (7 cm −1 ) indicates that GO nanosheets might induce different extents of electron donation from AgNPs of different sizes. This issue could lead to a different electron concentration on the AgNPs in the 2.5‐AgNPs/GO, 4.3‐AgNPs/GO, and 6.2‐AgNPs/GO composites and accordingly is likely responsible for their size‐dependent catalytic behaviors …”

Water dispersible magnetite nanocluster coated with thermo‐responsive thiolactone‐containing copolymer

“…Hence, many researches have now focused on taking advantages of functional polymers in an attempt to improve properties of materials for use in a wide range of applications such biosensor, drug delivery systems, purification, or separation systems . Some of these polymers can also respond to external stimuli such as temperature, pH, light, electrostatic, and electrical . PNIPAAm, the most well‐known thermo‐responsive polymer, can respond to temperature changes when heated to the temperature crossing its lower critical solution temperature (LCST of PNIPAAm = 32°C) .…”