Reversible oxygen gas sensor based on electrochemiluminescence

Spontaneous formation of gold nanostructures in aqueous microdroplets

The synthesis of gold nanostructures has received widespread attention owing to many important applications. We report the accelerated synthesis of gold nanoparticles (AuNPs), as well as the reducing-agent-free and template-free synthesis of gold nanoparticles and nanowires in aerosol microdroplets. At first, the AuNP synthesis are carried out by fusing two aqueous microdroplet streams containing chloroauric acid and sodium borohydride. The AuNPs (~7 nm in diameter) are produced within 60 µs at the rate of 0.24 nm µs⁻¹. Compared to bulk solution, microdroplets enhance the size and the growth rate of AuNPs by factors of about 2.1 and 1.2 × 10⁵, respectively. Later, we find that gold nanoparticles and nanowires (~7 nm wide and >2000 nm long) are also formed in microdroplets in the absence of any added reducing agent, template, or externally applied charge. Thus, water microdroplets not only accelerate the synthesis of AuNPs by orders of magnitude, but they also cause spontaneous formation of gold nanostructures.

Reactions in aqueous microdroplets can significantly differ from those in bulk. Here, the authors report microdroplets that not only accelerate gold nanoparticle formation by several orders of magnitude but also promote spontaneous nanostructure formation with no reducing agents or template.

Electro-Photodynamic Visualization of Singlet Oxygen Induced by Zinc Porphyrin Modified Microchip in Aqueous Media

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 (¹O₂) 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 O₂ 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.

Study of oxygen effects on electrochemiluminescence using dye-doped oxygen-resisting nanobeads

Tris(4,7-diphenyl-1,10-phenanthroline)-ruthenium(II) (Rudpp) doped oxygen-resisting nanobeads were synthesized and applied in order to study the effects of oxygen on electrochemiluminescence.