Co nanoparticles decorated with N-doped carbon nanotubes as high-efficiency catalysts with intrinsic oxidase-like property for colorimetric sensing

Abstract

In this work, we designed a Co@N-CNTs hybrid nanocomposite as an oxidase mimic for the colorimetric detection of ascorbic acid with the naked eye.

Cobalt Nanoparticles Encapsulated with N-Doped Bamboo-Like Carbon Nanofibers as Bifunctional Catalysts for Oxygen Reduction/Evolution Reactions in a Wide pH Range

“…Figure c,f shows narrow spectra of Co 2p of Co–N/C and Co–N/C fiber that illustrate two typical 2p 1/2 and 2p 3/2 peaks. , The Co 2p 3/2 can be further deconvoluted into Co–N x , Co­(II), Co(0), and satellite at about 782.3, 780.3, 778.6, and 786.5 eV, respectively. , Metal-coordinated nitrogen (i.e., M–N x ), which is reported as the most active site toward ORR, − presents in a larger portion in Co–N/C fiber (22.92% Co–N x ), compared to 15.84% in Co–N/C. With the presence of N-doped carbon nanofiber-encapsulated Co nanoparticle and a high amount of active sites (i.e., graphitic-N, pyridinic-N, and Co–N x ), the Co–N/C fiber is likely to produce a higher ORR performance than Co–N/C in a wide pH range.…”

“…The deconvolution of N 1s spectra shows three peaks at around 402.1, 400.7, and 398.9 eV (Figure b,e). These peaks correspond to graphitic-N, pyrrolic-N, and pyridinic-N, respectively. , The relative percentage of these N-moieties is described in Table S1. Among the metal-free N-moieties, pyridinic-N and graphitic-N are found as the ORR active sites .…”

“…Figure 4c,f shows narrow spectra of Co 2p of Co−N/C and Co−N/C fiber that illustrate two typical 2p 1/2 and 2p 3/2 peaks. 49,50 The Co 2p 3/2 can be further deconvoluted into Co−N x , Co(II), Co(0), and satellite at about 782.3, 780.3, 778.6, and 786.5 eV, respectively. 49,54 Metal-coordinated nitrogen (i.e., M−N x ), which is reported as the most active site toward ORR, 55−58 Three different electrolytes, 0.1 M KOH, 0.1 M PBS, and 0.5 M H 2 SO 4 , which correspond to pH values of about 13, 7, and 0.6, were used to evaluate the universality of catalyst performance in alkaline, neutral, and acidic conditions, respectively.…”

“…49,50 The Co 2p 3/2 can be further deconvoluted into Co−N x , Co(II), Co(0), and satellite at about 782.3, 780.3, 778.6, and 786.5 eV, respectively. 49,54 Metal-coordinated nitrogen (i.e., M−N x ), which is reported as the most active site toward ORR, 55−58 Three different electrolytes, 0.1 M KOH, 0.1 M PBS, and 0.5 M H 2 SO 4 , which correspond to pH values of about 13, 7, and 0.6, were used to evaluate the universality of catalyst performance in alkaline, neutral, and acidic conditions, respectively. To evaluate the ORR activity, ORR polarization curves of both samples were assessed using RDE in O 2 - Noticeably, the ORR activity of Co−N/C fiber outperforms Co−N/C in all pH conditions.…”

CeO2–Co3O4 nanocomposite with oxidase-like activity for colorimetric detection of ascorbic acid

“…However, TMB in the buffer containing CeO 2 –Co 3 O 4 NC results in a blue solution, and strong absorbance at 652 nm is observed, which is similar to MnO 2 NSs, 33 Pd cube@CeO 2 (ref. 34 ) and Co@N-CNTs 35 catalyzed TMB oxidation. All these results reveal that the obtained CeO 2 –Co 3 O 4 NC exhibits oxidase-like catalytic activity toward TMB oxidation.…”