A porphyrin-based electro-photodynamic imaging system was fabricated for monitoring the concentration of oxygen. Distinct from the electrochemiluminescent (ECL) inability of numerous organic species in aqueous solutions, a strong and stable red irradiation at 634 nm could be stimulated electrochemically on zinc(II) meso-tetra(4-carboxyphenyl) porphine (ZnTCPP)/tetraoctylammonium bromide (TOAB) in the physiological condition. In terms of in situ electron paramagnetic resonance and ECL spectroscopies, the nature of ECL was thoroughly investigated, being exactly the chemiluminescence from singlet oxygen (O) produced during the successive electro-reduction of ZnTCPP. Meanwhile, the excellent film-making capacity of amphiphilic TOAB as a potent ion barrier granted the luminophores a micro-order and patternable electrode modification. Such platform was exceptionally tolerant of pH variation, facilitating a durable solid-state ECL visualization under potentiostatic electrolysis and time exposure in the charge-coupled device (CCD) camera. For flow-injection and real-time detection, a chip-mounted microfluidic cell was customized and manufactured. A sensitive and simple vision-sensing of O was further achieved with a real determination limit as low as a few micromolar level. The developed ECL imaging system is a good prototype and an eco-friendly technique in the cathodic range, and thus, it would supplement the primary anodic imaging library, showing great promise for multiplexed and colorimetric assays as well as oxygen-involved activity studies in the future.

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This work proposed a label-free, cost-effective and fairly sensitive electrogenerated chemiluminescence (ECL) strategy for the specific detection of lysozyme based on the hemin/G-quadruplex hybrid. Gold nanoparticles were spread onto the chitosan thin-film as substrate to adsorb thiolated captures: a hairpin-structured DNA, integrating dual head-tail connected functional domains: one aptamer sequence for lysozyme and the other for hemin (iron(III) proto-porphyrin IX). In the presence of the both, the hairpin conformation unfolded and transformed into the hemin/ G-quadruplex motif, which quenched the ECL emission of underlaid quantum dots significantly via the consumption of dissolved oxygen as endogenous coreactant. This construction enabled a wide linear response to lysozyme, ranging from 20 pg•mL 1 to 5 μg• mL 1 , with a detection limit as low as 4.95 pg• mL 1 (e.g. 9.4 pmol•L 1 ), demonstrating the prospective utilization of DNA technologies in bioanalysis.