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A self-switchable polymer reactor with a hyperbranched structure for controlled catalytic chemistry processes is reported. This polymer reactor was made of silver nanoparticles and a polymer carrier consisting of hyperbranched polyethylenimine and hydroxyethyl acrylate that behaved as thermally switchable domains. Below the transfer temperature, relatively strong catalytic reactivity was demonstrated due to the leading role of hydrophilic groups in the switchable domains, which opened access to the substrate for the packaged silver nanoparticles. In contrast, it showed weak catalysis at relatively high temperatures, reducing from the significantly increased hydrophobicity in the switchable domains. In this way, the polymer reactor displays controllable, tunable, catalytic activity based on this approach. This novel design opens up the opportunity to develop intelligent polymer reactors for controlled catalytic processes. [ABSTRACT FROM AUTHOR]

Abstract: A novel electrochemical immunosensor capable of enzyme-free detection of alpha fetoprotein (AFP) is reported. This immunosensor was fabricated in a sandwich-like format where catalytic Au–Pd nanocrystals and highly conductive N-doped graphene sheets were incorporated. The significant catalysis by Au–Pd nanocrystals toward hydrogen peroxide, along with the increased electron transfer by graphene sheets, caused signal generation and increased sensitivity, which enables the enzyme-free detection of AFP. With a low detection limit at 0.005ngmL−1, this novel immunosensor worked well over the broad linear range of 0.05–30ngmL−1. Unlike previously reported enzyme-based electrochemical immunosensors, which often involve the complicated steps for enzyme loading and necessary treatments to keep the activity of enzyme, this novel immunosensor is simple in nature and employed catalytic Au–Pd nanoparticles and highly conductive graphene, which thus enables reliable and sensitive detection for clinic usage. [Copyright &y& Elsevier]

Abstract: ‘On/off’-switchable catalysis by a smart enzyme-like imprinted polymer is reported. This unique imprinted polymer was composed of poly(N-isopropylacrylamide)-containing p-nitrophenyl phosphate-imprinted networks that exhibited temperature-dependent hydrophilicity/hydrophobicity. At a relatively low temperature (such as 20°C), this polymer was capable of vigorous catalysis for the hydrolysis of p-nitrophenyl acetate due to its hydrophilic networks, which enabled access to the imprinted framework. On the contrary, at higher temperatures (such as 40°C), this polymer demonstrated poor catalysis resulting from its dramatically increased hydrophobicity, which inhibited access to the imprinted sites. Unlike previously reported imprinted polymers which lack adjustable networks, this novel imprinted polymer employed thermosensitive poly(N-isopropylacrylamide) networks, thus enabling the switchable catalysis. [Copyright &y& Elsevier]

This study aimed at the present challenge in self-controlled catalysis, addressing how to furnish the catalysts with sortable catalytic ability. This objective was reached by developing a polymer catalyst made of metal nanoparticles and a unique polymer carrier containing self-assembled hierarchical access. The hierarchical access, by closing, relaxing and opening, acted as a molecular switch for providing sequenced entrance to the encapsulated metal nanoparticles. This polymer catalyst showed poor catalytic reactivity at relatively low temperatures due to the closed access, which blocked substrate from the encapsulated metal nanoparticles. This polymer catalyst showed, however, significant reactivity for small molecules of substrate at modest temperatures, arising from relaxing of the access, which allowed small molecules to gain entrance to the catalytic metal nanoparticles. This polymer catalyst further showed significant reactivity for large molecules of substrate at relatively high temperatures, in response to the opening at the access. In this way, this polymer catalyst demonstrated the sortable catalytic ability. This suggested protocol opens up the opportunity to develop smart catalysts for controlled chemical processes. [ABSTRACT FROM AUTHOR]