NiCo‐LDH Hollow Nanocage Oxygen Evolution Reaction Promotes Luminol Electrochemiluminescence

Abstract

Conventional luminol co‐reactant electrochemiluminescence (ECL) systems suffer from low stability and accuracy due to factors such as the ease of decomposition of hydrogen peroxide and inefficient generation of reactive oxygen species (ROS) from dissolved oxygen. Inspired by the luminol ECL mechanism mediated by oxygen evolution reaction (OER), the nickel‐cobalt layered double hydroxide (NiCo‐LDH) hollow nanocages with hollow structure and defect state are used as co‐reaction promoters to enhance the ECL emission from the luminol‐H2O system. Thanks to the hollow structure and defect state, NiCo‐LDH hollow nanocages show excellent OER catalytic activity, which can stabilize and efficiently produce ROS and enhance the ECL emission. Additionally, mechanistic exploration suggests that the ROS involved in the co‐reaction of the luminol‐H2O system are derived from the OER reaction process, and there is a positive correlation between ECL intensity and the OER catalytic activity of the co‐reaction promoter. The selection of catalysts with excellent OER catalytic activity is a key factor in improving ECL emission. Finally, a dual‐mode immunosensor is constructed for the detection and analysis of alpha‐fetoprotein (AFP) based on the promoting effect of NiCo‐LDH hollow nanocages on the luminol‐H2O ECL system.

Bright Luminescence of Free Radical TEMPO Enabled by Electrochemiluminescence Technique

“…As a milestone discovery for ECL, coreactant is some substance that can significantly produce intermediates and then assist luminophores to output amplified ECL signals. − Consequently, many ECL research efforts have been directed toward the development of outstanding coreactants. − In view of this, the coreaction ECL of TEMPO was explored in the presence of some elegant coreactants including oxalate ion (C 2 O 4 2– ), hydrogen peroxide (H 2 O 2 ), tri- n -propylamine (TprA), and potassium persulfate (K 2 S 2 O 8 ) under different measurement conditions.…”

Enhanced Electrochemiluminescence at the Gas/Liquid Interface of Bubbles Propelled into Solution

“…•− ), produced during H 2 O 2 decomposition, water oxidation, 65,66 or reduction of dissolved oxygen, 64,67 ultimately populating the excited state and emitting blue light upon decay. 15,64,68 Enhancing the ECL intensity, duration, and spatial extension in the luminol/H 2 O 2 coreactant system depends significantly on understanding the underlying mechanisms for ECL generation.…”

“…15,64,68 Enhancing the ECL intensity, duration, and spatial extension in the luminol/H 2 O 2 coreactant system depends significantly on understanding the underlying mechanisms for ECL generation. 15,53 Common strategies for modulating the luminol ECL response involve designing more efficient ECL emitters such as substituted luminol derivates, 56,69−71 employing materials [64][65][66][67]72 and experimental conditions 15,73 that facilitate the generation of radical intermediates and using reagents that lead to prolonged ECL generation. 71,74 Another approach toward accelerating the rates of chemical reactions and improving their efficiency involves conducting the reactions within confined environments, 20,23,72,75 such as micropores, 15,76,77 droplets, 26,27,78 or interface 79 of bubbles, 6,28,80 leading to enhanced ECL intensities.…”

“…Luminol (and its derivatives) emits light upon oxidation in the presence of H 2 0 2 in alkaline aqueous solutions. The luminescence intensity is linearly dependent on the H 2 O 2 concentration. − The mechanism of this ECL generation is complex, involving luminol oxidation to yield diazaquinone radicals (L•−). , These radicals subsequently react with hydrogen peroxide anion (HO 2 – ) or other reactive oxygen species (ROS), namely hydroxyl radicals (OH • ) and superoxide radicals (O 2 •– ), produced during H 2 O 2 decomposition, water oxidation, , or reduction of dissolved oxygen, , ultimately populating the excited state and emitting blue light upon decay. ,, …”

“…Enhancing the ECL intensity, duration, and spatial extension in the luminol/H 2 O 2 coreactant system depends significantly on understanding the underlying mechanisms for ECL generation. , Common strategies for modulating the luminol ECL response involve designing more efficient ECL emitters such as substituted luminol derivates, ,− employing materials − , and experimental conditions , that facilitate the generation of radical intermediates and using reagents that lead to prolonged ECL generation. , Another approach toward accelerating the rates of chemical reactions and improving their efficiency involves conducting the reactions within confined environments, ,,, such as micropores, ,, droplets, ,, or interface of bubbles, ,, leading to enhanced ECL intensities. Moreover, within microscopic bubbles and droplets, which possess a high surface-to-volume ratio, interfacial effects can significantly stimulate chemical reactivity, as already mentioned. ,, For instance, Ciampi and coworkers demonstrated that the elevated self-ionization constant of water at the gas–water interface leads to the accumulation of hydroxide ions, resulting in the electrically charged corona of the bubble-promoting oxidative processes (specifically ROS generation) at the electrode-gas–water interface …”