Jiaxing Zhang,Hongying Shen,Wenguang Song,Guowei Wang
A series of novel linear and hyperbranched copolymers with different topological structures and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical distributions were synthesized, and their paramagnetic property was systematically investigated. Based on the ring-opening polymerization (ROP) mechanism of GTEMPO, glycidol (Gly) or ethylene oxide (EO) monomers, the linear Poly(EO-co-GTEMPO) and hyperbranched Poly(Gly-co-GTEMPO) copolymers were obtained from a bifunctional 2,2-dimethyl-1,3-propanediol initiator and a tetrafunctional pentaerythritol initiator, respectively. Alternatively, from the multifunctional macroinitiator of hyperbranched polyglycerol (HPG), the hyperbranched HPG-g-Poly(Gly-co-GTEMPO) and HPG-g-PGTEMPO copolymers were also targeted. The copolymers were characterized by GPC, DSC, and UV–vis analysis. The paramagnetic property of the copolymers was studied and compared by EPR analysis at different concentrations of copolymers and temperatures. The results displayed that the concentrations of copolymers majorly manipulated the signal intensity of EPR spectra, and the temperature majorly modulated the shape of EPR spectra. Essentially, the TEMPO radical distributions in copolymers played an important role: the higher regional density tended to give the EPR spectra with intense, broad peaks, while the lower one led to the regular, well-pronounced EPR spectra. The difference was rationalized to different intramolecular spin–spin exchange and dipole–dipole interaction modulated by the topological structures and the corresponding TEMPO radical distributions.
Haidong Li,Guangyue Zhao,Yuxin Yang,Danli Zhong,Zhenxing Yang,Chengyin Wang
In this work, a series of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) radicals bearing different functional groups were exploited as a simple catalyst to promote electrochemiluminescence (ECL) generation in luminol/H 2 O 2 system. These TEMPO radicals were found to facilitate the electrochemical oxidation of H 2 O 2 and luminol through different catalytic mechanisms, as well as the subsequent ECL generation of luminol/H 2 O 2 system. The electrochemical oxidation and luminol ECL generation could be tuned by the functional group on the para -position of TEMPO, for which the structure/activity relationship was revealed. Finally, with the combination of enzymatic system, luminol ECL enhancement up to 9.6-fold was obtained through the catalysis of 4-hydroxyl-TEMPO. The enhanced luminol ECL allows acquiring brighter ECL images in a single-electrochemical system (SEES) for multiplex detection of cholesterol, H 2 O 2 and glucose.
Bei Jiang,Mengya Xu,Ling Zhang,Wenjing Wang,Xin Qin,Shenyan Xu,Chunyu Che,Chuanqi Zhang,Wenzhong Wang
Open-shell organic radicals, characterized by their unique spin states, typically exhibit exceptional photothermal conversion efficiency. However, the development of open-shell organic radical materials with stability and high photothermal properties remains a challenge. Among these radicals, the stable and commercialized 4-OH-TEMPO radical molecule has garnered considerable attention in various organic synthesis reactions owing to its unique redox advantages, but it shows less application comparing with the other open-shell organic radicals in photo-thermal conversion. In this study, 4-OH-TEMPO exhibits favorable photothermal properties upon combination with Cu 2 + , thus it is capable of enhancing the reaction rate of HMF oxidation to DFF by a factor of 10 under LED (400 nm). Under illumination of LED, leading to the complete conversion of HMF and the generation of DFF with a yield of 99.7 % within 30 min. Mechanism study shows that the photothermal effect facilitates the kinetic process of the reaction, and accelerated conversion of 4-OH-TEMPO to the oxidatively active species 4-OH-TEMPO + under light-induced action further increased the reaction rate. This research proffers novel insights and references for 4-OH-TEMPO mediated organic synthesis reactions and the design of free-radical photothermal materials.
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