Metal-coordinated porous polydopamine nanospheres derived Fe_(3)N-FeCo encapsulated N-doped carbon as a highly efficient electrocatalyst for oxygen reduction reaction

The exploration of high-efficiency,long-durability,and cost-effectiveness transition metal doped carbon materials to replace the commercial Pt/C in oxygen reduction reaction(ORR)is greatly desirable for promoting the advancement of sustainable energy devices.Herein,the Fe_(3)N and FeCo alloy decorated N-doped carbon hybrid material(denoted Fe_(3)N-FeCo@NC)is prepared and applied as the ORR catalyst,which is derived from the two-step pyrolysis of an intriguing complex consisted of metal-coordinated porous polydopamine(PDA)nanospheres(i.e.,Fe-PDA@Co)and melamine.The resulting Fe_(3)N-FeCo@NC delivers outstanding ORR activity with an onset potential(E_(on))of 1.05 V,a half-wave potential(E_(1/2))of 0.89 V,as well as excellent long-term stability and methanol resistance over Pt/C.Interestingly,the home-made Zn-air battery with Fe_(3)N-FeCo@NC as the air-cathode demonstrates much higher open-circuit voltage(1.50 vs.1.48 V),power density(141 vs.113 mW·cm^(−2))and specific capacity(806.6 vs.660.6 mAh·g^(−1)_(Zn))than those of Pt/C counterpart.Such a remarkable ORR activity of Fe_(3)N-FeCo@NC may stem from the synergistic effect of Fe_(3)N and FeCo active species,the large surface area,the hierarchical porous structure and the exceptional sphere/sheet hybridized architecture.

pH Readout enhanced ELISA for point-of-care testing of cardiac troponin I

Enzyme-linked immunosorbent assay（ELISA） as a conventional method for protein quantification has its characteristic properties,however,it is challenging to implement excellent portability and sensitivity at the same time.In this study,we described a pH ELISA using synthetic melanin nanoparticles（SMNPs） for the co-immobilization of glucose oxidase（GOx） and second antibody（Ab_2） as signal labels,portable pH meter as signal readout device for point-of-care testing（POCT） of cardiac troponin I（cTnI）.In accordance with the varying amount of cTnI,following sandwich type immunoassay,proportional SMNPs-GOx-Ab_2 were immobilized specifically resulting in corresponding decrease of pH values owing to GOx loaded on SMNPs can high-efficiency convert glucose into gluconic acid.This assay is easy-to-use,portable,sensitive and able to realize POCT,affording a linear range from 0.5 pg/m L to 10 ng/m L and low limit of detection（LOD） of 0.15 pg/m L towards cTnI,which was demonstrated the significant promising in the early diagnosis and screening of acute myocardial infarction.