Modulating Oxygen Reduction Behaviors on Nickel Single-Atom Catalysts to Probe the Electrochemiluminescence Mechanism at the Atomic Level

Abstract

Luminol-dissolved O2 electrochemiluminescence (ECL)-sensing platforms have been widely developed for sensitive and reliable detection, while their actual ECL mechanisms are still in controversy due to the involved multiple reactive oxygen species (ROS). Different from the structural complexity of nanomaterials, well-defined single-atom catalysts (SACs) as coreaction accelerators will provide great prospects for investigating the ECL mechanism at the atomic level. Herein, two carbon-supported nickel SACs with the active centers of Ni–N4 (Ni–N4/C) and Ni–N2O2 (Ni–N2O2/C) were synthesized as efficient coreaction accelerators to enhance the ECL signals of a luminol-dissolved O2 system. By modulating the surrounding environment of the center metal atoms, their corresponding oxygen reduction behaviors can be well controlled to selectively produce intermediate ROS, giving a great chance to study the following ECL process. According to the experimental and calculated results, the superoxide radical (O2 •–) acts as the main radical for the ECL reaction and the Ni–N4/C catalyst with the four-electron pathway to activate dissolved O2 is preferential to enhance ECL emission.

Platinum Janus Nanoparticles as Peroxidase Mimics for Catalytic Immunosorbent Assay

“…To further reveal the main role of free radicals in the oxidation of substrates, IPA (hydroxyl radical scavenger), KBrO 3 (electron scavenger), NaN 3 (singlet oxygen scavenger), TEA (metal blocker), and l -AA (superoxide anion scavenger) were added to the catalytic system. − As shown in Figure c,d, Pt Janus NPs oxidize substrates at a rate of 16 × 10 –8 M/s without any capture agent. In the presence of IPA and KBrO 3 , the catalytic oxidation rate of the substrate decreased to 13.8 × 10 –8 and 13.7 × 10 –8 M/s, respectively.…”

Versatile Luminol/Dissolved Oxygen/Fe@Fe2O3 Nanowire Ternary Electrochemiluminescence System Combined with Highly Efficient Strand Displacement Amplification for Ultrasensitive microRNA Detection

“…As an endogenous component existing in most biological systems, dissolved oxygen has been found to be a potential substitute for H 2 O 2 as a coreactant. 8 Nonetheless, the low decomposition rate of dissolved oxygen usually could not produce adequate intermediate radicals to achieve strong ECL intensity for biological detection. 7 In previous research studies, single-atom iron, TiO 2 , and zirconium-based porphyrinic metal−organic framework nanoparticles (NMOFs) have been used as coreaction accelerators to boost the generation of reactive oxygen species (ROS) from dissolved oxygen.…”

“…Therefore, an alternative resolution was to seek for a safe and efficient coreactant to replace H 2 O 2 . As an endogenous component existing in most biological systems, dissolved oxygen has been found to be a potential substitute for H 2 O 2 as a coreactant . Nonetheless, the low decomposition rate of dissolved oxygen usually could not produce adequate intermediate radicals to achieve strong ECL intensity for biological detection .…”

Identifying Luminol Electrochemiluminescence at the Cathode via Single-Atom Catalysts Tuned Oxygen Reduction Reaction

“…The emerging single-atom catalysts (SACs) with isolated active metal atoms stabilized on supports have been considered promising and efficient catalysts for ORR in electrochemical energy conversion systems. − During the ORR process, ROS such as superoxide (O 2 •– ), H 2 O 2 , and hydroxyl radical (OH • ) can be produced via the stepwise reduction of O 2 , which are often involved in the anodic ECL mechanism for boosting light emission. − However, ECL research on SACs has not been investigated in the cathodic domain. Moreover, the ORR activity of the SACs can be tuned by precise regulation of the active metal center and its local coordination environment. − It appears to us that the ORR catalyzed by SACs would provide a representative platform for investigating the relationship between ORR performance and ECL behavior.…”