选择巯基化并含有PW17碱基序列的DNA在金电极上自组装,在10μmol/L Pb2+存在下,Pb2+诱导自组装的DNA形成Pb2+稳定的G-四联体.通过微分脉冲伏安法发现Pb2+稳定的G四联体在-0.365 V vs.Ag/AgCl出现一Pb2+的还原峰.依据Pb2+与EDTA的强配位作用,EDTA可以与G-四联体中的Pb2+作用,并伴随G-四联体的构型转变为自由态的DNA.以组装在电极上的DNA为工作单元,Pb2+和EDTA作为输入信号,-0.365 V处的还原峰为输出信号,根据Pb2+和EDTA加入顺序的不同,键盘锁处于"开"或"关"的状态.在Pb2+与EDTA的交替作用下,G-四联体和自由态DNA可以互相转化,同时电化学的输出信号在循环5次后基本保持不变,键盘锁呈现出良好的可重置性.
Incorporating fluorophores into polymeric nanoparticles has been testified as a feasible way to improve the emitting property and bio-compatibility of nano-emitters, which can be applied as fluorescent probes in labeling cells for imaging. Plenty of efforts have been made on the above direction. However, the size effect of nano-emitters has not been addressed yet mainly given the difficulties in controlling morphology and size of the assemblies. In our preceding study, we employed post-polymerization modification method for preparing amphiphilic copolymers, and obtained core-shell(the hydrophobic fluorophores are wrapped inside the nanoparticle to form the core) assemblies in aqueous solution. By this method, we are able to regulate the ratio of the hydrophilic/hydrophobic moieties, and thus alternate the size of the assemblies in a rather simple way. In this study, we synthesized a series of random copolymers by changing the ratio of poly(ethylene glycol) to tetraphenylethylene groups. Notably, the number of repeating units of the polymer was controlled constant for all the copolymers. The self-assembly of these copolymers resulted in different sizes of nanoparticles, and the size decreased with the decreasing fraction of poly(ethylene glycol). Interestingly, the emission of the nanoparticles showed size dependence, and smaller diameter corresponded to stronger emission. Being cultured with HeLa cells, either the large(diameter of ~300 nm) or the small(diameter of ~180 nm) nano-emitters allowed for very high cell viabilities up to 25 μg·mL-1. Both of them can be applied in cell imaging and provide high contrast fluorescent images.
Xiao-Cheng WangShi-Xin ZhouLan DingYu-Han ZhaoShen-Xi MinBin DongBo Song
High-performance white light-emitting diodes (WLEDs) hold great potential for the next-generation backlight display applications.However,achieving highly efficient and stable WLEDs with wide-color-gamut has remained a formidable goal.Reported here is the first example of pure red narrow bandwidth emission triangular CQDs (PR-NBE-T-CQDs) with photoluminescence peaking at 610 nm.The PR-NBE-T-CQDs synthesized from resorcinol show high quantum yield (QY) of 72% with small full width at half maximum of 33 nm.By simply controlling the reaction time,pure green (PG-) NBE-T-CQDs with high QY of 75% were also obtained.Highly efficient and stable WLEDs with wide-color-gamut based on PR- and PG-NBE-T-CQDs was achieved.This WLED showed a remarkable wide-color gamut of 110% NTSC and high power efficiency of 86.5 lumens per Watt.Furthermore,such WLEDs demonstrate outstanding stability.This work will set the stage for developing highly efficient,low cost and environment-friendly WLEDs based on CQDs for the next-generation wide-color gamut backlight displays.
Fanglong YuanPing HeZifan XiXiaohong LiYunchao LiHaizheng ZhongLouzhen FanShihe Yang
Sulfur(S)-doped graphene sheets were prepared by a facile electrochemical method, which effectively combined exfoliation of graphite and in situ S doping of graphene together. The metal-free S-doped graphene sheets exhibit high electrocatalytic activity, long-term stability, and excellent tolerance to cross-over effects of methanol in alkaline media for the oxygen reduction reaction(ORR), indicating that these S-doped graphene sheets possess great potential for a substitute for Pt-based catalysts in fuel cells.
