A Carbonate-Involved Amplification Strategy for Cathodic Electrochemiluminescence of Luminol Triggered by the Catalase-like CoO Nanorods

The lumiol-O₂ electrochemiluminescence (ECL) system constantly emits bright light at positive potential. Notably, compared with the anodic ECL signal of the luminol-O₂ system, the great virtues of cathodic ECL are that it is simple and causes minor damage to biological samples. Unfortunately, little emphasis has been paid to cathodic ECL, owing to the low reaction efficacy between luminol and reactive oxygen species. The state-of-the-art work mainly focuses on improving the catalytic activity of the oxygen reduction reaction, which remains a significant challenge. In this work, a synergistic signal amplification pathway is established for luminol cathodic ECL. The synergistic effect is based on the decomposition of H₂O₂ by catalase-like (CAT-like) CoO nanorods (CoO NRs) and regeneration of H₂O₂ by a carbonate/bicarbonate buffer. Compared with Fe₂O₃ nanorod (Fe₂O₃ NR)- and NiO microsphere-modified glassy carbon electrodes (GCEs), the ECL intensity of the luminol-O₂ system is nearly 50 times stronger when the potential ranged from 0 to -0.4 V on the CoO NR-modified GCE in a carbonate buffer solution. The CAT-like CoO NRs decompose the electroreduction product H₂O₂ into OH^· and O₂^·-, which further oxidize HCO₃^- and CO₃^2- to HCO₃^· and CO₃^·-. These radicals very effectively interact with luminol to form the luminol radical. More importantly, H₂O₂ can be regenerated when HCO₃^· dimerizes to produce (CO₂)₂*, which provides a cyclic amplification of the cathodic ECL signal during the dimerization of HCO₃^·. This work inspires developing a new avenue to improve cathodic ECL and deeply understand the mechanism of a luminol cathodic ECL reaction.

Investigating the impact of metal ions and 3D printed droplet microfluidics chip geometry on the luminol‑potassium periodate chemiluminescence system for estimating total phenolic content in olive oil

The impact of the chip design and the mixing mechanisms using six different 3D printed microfluidic chips were investigated. The study was conducted using novel 3D printed droplet based microfluidics. A multi-mixing approach was utilized to enhance the CL signal of the CL system under investigation. The approach is based on droplet formation, droplet mixing and droplets merging in the 3D printed microfluidic chip. A 154% higher CL signal intensity was obtained using this approach compared to the CL signal obtained using the serpentine chip commonly used for improving the mixing inside droplet microfluidics. This chip was exploited to study the role of three metal ions: Co²⁺, Mn²⁺ and Fe²⁺ on catalyzing the luminol‑potassium periodate chemiluminescence (CL) reaction with selected phenolic compounds in basic media was carefully investigated. Furthermore, the luminol‑potassium periodate-metal ions system was optimized for all metal ions using gallic acid as the reference standard. Despite the popularity of luminol systems in estimating antioxidant activity or total phenolic content (TPC), the results of this study revealed the necessity of careful and vigilant attention when applying it to complex matrices. The only metal ion that showed quenching behavior with all 20 of the tested phenolic compounds was Fe²⁺, while Co²⁺and Mn²⁺ showed both quenching and enhancement in the CL signal. The luminol‑potassium periodate-Fe²⁺ system was applied to estimate TPC in olive oil extracts.

Gold Nanoplate-Enhanced Chemiluminescence and Macromolecular Shielding for Rapid Microbial Diagnostics

With the global rise of antimicrobial resistance, rapid screening and identification of low concentrations of microorganisms in less than 1 h becomes an urgent technological need for evidence-based antibiotic therapy. Although many commercially available techniques are labeled for rapid microbial detection, they often require 24-48 h of cell enrichment to reach detectable levels. Here, it is shown that the widely used reducing agent tris(2-carboxyethyl)phosphine (TCEP) can also act as a powerful oxidant on gold nanoplates and subsequently lead to a strong catalysis of luminol chemiluminescence. The catalytic reaction results in up to 100-fold signal enhancement and unprecedented stable luminescence for up to 10 min. However, when TCEP is exposed to microorganisms, it is oxidized by the microbial surface proteins and loses its catalytic properties, leading to a decrease in chemiluminescence. The competitive interaction of TCEP with Au nanoplates and microorganisms is used to introduce a homogenous rapid detection method that allows microbial screening in less than 10 min with a limit of detection down to 100 cfu mL^-1 . Furthermore, the concept of microbial macromolecular shielding using antibody-conjugated polymers is introduced. The combination of TCEP redox activity and macromolecular shielding enables specific microbial identification within 1 h, without preconcentration, cell enrichment, or heavy equipment other than a hand-held luminometer. The technique is demonstrated by specific detection of methicillin-resistant Staphylococcus aureus in environmental and urine samples containing a mixture of microorganisms.

Comparison of uric Acid quantity with different food in human urine by flow injection chemiluminescence analysis

Based on the inhibitory effect of uric acid (UA) on luminol-Co(2+) chemiluminescence (CL) system, a sensitive method for the determination of UA at nanomolar level by flow injection (FI) CL was proposed. The proposed method was successfully applied to real-time monitoring of UA excretion in human 24 h urine with different food intake, showing that meats, vegetables, and porridge intake caused differential UA excretions of 879, 798, and 742 mg, respectively. It was also found that UA concentrations in urine under the three kinds of food intake simultaneously reached maximum at 2 h after meals with the values of 417, 318, and 288 μg mL(-1), respectively. The UA concentration in human serum was also determined by this approach, and the possible mechanism of luminol-Co(2+)-UA CL reaction was discussed in detail.