Herein we report the study of electrochemiluminescence (ECL) generation by tris(2,2'bipyridyl)ruthenium (Ru(bpy) 3 2 + ) and five tertiary amine coreactants. The ECL distance and lifetime of coreactant radical cations were measured by ECL selfinterference spectroscopy. And the reactivity of coreactants was quantitatively evaluated in terms of integrated ECL intensity. By statistical analysis of ECL images of single Ru(bpy) 3 2 + -labeled microbeads, we propose that ECL distance and reactivity of coreactant codetermine the emission intensity and thus the sensitivity of immunoassay. 2,2-bis(hydroxymethyl)-2,2',2''-nitrilotriethanol (BIS-TRIS) can well balance ECL distancereactivity trade-off and enhance the sensitivity by 236 % compared with tri-n-propylamine (TPrA) in the beadbased immunoassay of carcinoembryonic antigen. The study brings an insightful understanding of ECL generation in bead-based immunoassay and a way of maximizing the analytical sensitivity from the aspect of coreactant.

This work reports an enzyme-free glucose sensor based on nickel nanostructures electrodeposited on a fluorine-doped tin oxide (FTO) electrode modified with a silica nanochannel membrane (SNM).

Hydrogen peroxide (H 2 O 2 ) is an important molecule that is widely used or exists in foods, medicines, detergents and human body. Therefore, fast and accurate detection of H 2 O 2 is highly important in food security, disease diagnosis, etc. In this work, we report the fabrication of platinized silica nanoporous membrane (Pt@SNM) electrodes for the detection of H 2 O 2 in complex in vitro and in vivo environments. The porous structure of SNM can effectively confine the electrodeposition of Pt nanostructures and meanwhile prevent the adsorption of fouling species on the underlying electrode. In comparison with conventional electrodes for H 2 O 2 detection, the current one exhibited excellent antifouling ability and worked well in complex real samples. As we demonstrated that the Pt@SNM modified carbon fiber microelectrode could work pretty stably in cortex of rat brain up to 90 min. We believe that this methodology can be extended for electrochemical detection of many other species in strongly fouling media.[a] X.

Herein we report the fabrication of highly sensitive solid-state pH sensors based on iridium oxide nanowires (IONWs) for a wide-range of pH measurements. IONWs were confined electrodeposits on the indium tin oxide (ITO) electrode using a highly ordered silica nanochannel membrane as the template. Subsequently removing the template produced amorphous IONWs consisting of hydrated iridium oxyhydroxides. The IONW/ITO sensor can rapidly respond to the pH of the aqueous solutions in a wide range (from 0 to 13), avoiding the acid and alkaline errors encountered by conventional pH electrodes and exhibiting a super-Nernst analytical sensitivity as high as 235.5 mV/pH in the very acidic range of ∼0–2.5 and 90.1 mV/pH beyond (pH = ∼2.5–13). The sensitivity was associated with the interconversion of oxidation states of iridium oxyhydroxides. While in the very acidic range, intercalation of Cl– was proved to be responsible for the exceptionally high pH sensitivity. Moreover, the sensor was also demonstrated to work in organic solutions too. Finally, the flexible IONW/ITO electrode was prepared and interfaced to a wireless electrochemical device for real-time epidermal pH analysis with smartphones.

Electrochemiluminescence (ECL) imaging analysis based on the ultra-high-density microwell electrode array (UMEA) has been successfully used in biosensing and diagnostics, while the studies of ECL generation mechanisms with spatial resolution remain scarce. Herein we fabricate a gold-coated polydimethylsiloxane (PDMS) UMEA using electroless deposition method for the visualization of ECL reaction process at the single microwell level in conjunction with using microscopic ECL imaging technique, demonstrating that the microwell gold walls are indeed capable of enhancing the ECL generation. For the classical ECL system involving tris(2,2′-bipyridyl)ruthenium (Ru(bpy)32+) and tri-n-propylamine (TPrA), the ECL image of a single microwell appears as a surface-confined ring, indicating the ECL intensity generated inside the well is much stronger than that on the top surface of UMEA. Moreover, at a low concentration of Ru(bpy)32+, the ECL image remains to be ring-shaped with the increase of exposure time, because of the limited lifetime of TPrA radical cations TPrA+•. In combination with the theoretical simulation, the ring-shaped ECL image is resolved to originate from the superposition effect of the mass diffusion fields at both microwell wall and bottom surfaces.

Electrochemiluminescence quantum efficiency (ECL-QE) is an important parameter to evaluate the energy conversion ability of luminophores and analytical sensitivity of corresponding ECL systems. Herein, taking tris(2,2'-bipyridine)ruthenium(II) (Ru-(bpy) 3 2 +) and tri-n-propylamine (TPrA) coreactant system as an example, the ECL-QE was evaluated in terms of a kinetic reaction model, in which Ru(bpy) 3 3 + was considered to be the key intermediate in a reaction scheme consisting of competitive oxidative reduction and catalytic reaction routes. It was calculated as the product of electrochemical excitation effi-ciency (η ex ) and light emission efficiency (i. e., photoluminescence quantum yield, PLQY). We used finite element simulations to examine the variation of η ex with the electrode material, applied potential, concentration and distance from the electrode surface. η ex was found to be largely determined by the electrochemical oxidation rate of TPrA that varied by several orders of magnitude with the electrode material. The estimation of ECL-QE helped in selecting the appropriate conditions for efficient ECL generation and sensitive analysis.

Herein we report the study of electrochemiluminescence (ECL) generation by tris(2,2'bipyridyl)ruthenium (Ru(bpy) 3 2 + ) and five tertiary amine coreactants. The ECL distance and lifetime of coreactant radical cations were measured by ECL selfinterference spectroscopy. And the reactivity of coreactants was quantitatively evaluated in terms of integrated ECL intensity. By statistical analysis of ECL images of single Ru(bpy) 3 2 + -labeled microbeads, we propose that ECL distance and reactivity of coreactant codetermine the emission intensity and thus the sensitivity of immunoassay. 2,2-bis(hydroxymethyl)-2,2',2''-nitrilotriethanol (BIS-TRIS) can well balance ECL distancereactivity trade-off and enhance the sensitivity by 236 % compared with tri-n-propylamine (TPrA) in the beadbased immunoassay of carcinoembryonic antigen. The study brings an insightful understanding of ECL generation in bead-based immunoassay and a way of maximizing the analytical sensitivity from the aspect of coreactant.