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This work developed a sensitive electrochemiluminescence (ECL) biosensor based on a cyclometalated iridium(III) complex ((bt)2Irbza), which was synthesized for the first time. Annihilation, reductive-oxidative, and oxidative-reductive ECL behaviors of (bt)2Irbza were investigated, respectively. The oxidative-reductive ECL intensity was the strongest compared with the other two, which showed 16.7 times relative ECL efficiency compared with commercial [Ru(bpy)3]2+ under the same experimental conditions. Therefore, an ECL biosensing system with (bt)2Irbza as the anodic luminophore was established for miRNA detection based on a closed bipolar electrode (BPE). Combined with both steric hindrance and catalytic effects induced by hemin/G-quadruplex in the cathodic reservoir of BPE that changed the Faraday current of the cathode and thus mediated the ECL intensity of (bt)2Irbza in the anode of BPE, the ECL sensor stated an ultrahigh sensitivity for microRNA (miRNA-122) analysis with a detection limit of 82 aM.

This paper describes a bidirectional electrochemiluminescence (ECL) biosensor for the detection of microRNA-141 (miRNA-141) with aM level detection limit and two-segment 8 orders of magnitude linear range. Hemin/G-quadruplex DNAzyme was assembled on carbon nitride nanosheets and Au nanoparticles modified electrode. The ECL of carbon nitride nanosheets could be enhanced by the right amount of H2O2 (no more than 10 mM) and then inhibited by excessive H2O2 when 0.1 M K2S2O8 acted as coreactant. In the presence of excessive H2O2 (20 mM), a recovery of ECL intensity was obtained due to the catalytic reduction of H2O2 caused by hemin/G-quadruplex DNAzyme at lower target concentrations, and then an ECL decrease occurred mainly by biocatalytic precipitation (BCP)-induced charge transfer resistance on the electrode surface at higher target concentrations. Therefore, based on the change of the ECL intensity caused by the catalytic reduction of H2O2 and BCP, a highly sensitive bidirectional miRNA sensor with ultralow detection limit of 7.9 aM and wide linear range from 10-17 to 10-9 M was obtained. This work could attract more attention on the study of multiple mechanisms and also provides a more sensitive and precise method for the analysis of nucleic acids.

As a highly toxic and widely used chemical, phosgene has become a serious threat to humankind and public security because of its potential use by terrorists and unexpected release during industrial accidents. For this reason, it is an urgent need to develop facile, fast, and selective detection methods of phosgene. In this Article, we have constructed a highly selective fluorescent sensor o-Pab for phosgene with a BODIPY unit as a fluorophore and o-phenylenediamine as a reactive site. The sensor o-Pab exhibits rapid response (∼15 s) in both colorimetric and turn-on fluorescence modes, high selectivity for phosgene over nerve agent mimics and various acyl chlorides and a low detection limit (2.7 nM) in solutions. In contrast to most undistinguishable sensors reported, o-Pab can react with phosgene but not with its substitutes, triphosgene and biphosgene. The excellent discrimination of o-Pab has been demonstrated to be due to the difference in highly reactive and bifunctional phosgene relative to its substitutes. Furthermore, a facile testing paper has been fabricated with poly(ethylene oxide) immobilizing o-Pab on a filter paper for real-time selective monitoring of phosgene in gaseous phase.

Improving the detection sensitivity of enzyme-linked immunosorbent assay (ELISA) is of utmost importance for meeting the demand of early disease diagnosis. Herein we report an ultrasensitive ELISA system using horseradish peroxidase (HRP)-loaded nanospherical poly(acrylic acid) brushes (SPAABs) as labels. HRP was covalently immobilized in SPAABs with high capacity and activity via an efficient "chemical conjugation after electrostatic entrapment" (CCEE) process, thus endowing SPAABs with high amplification capability as labels. The periphery of SPAAB-HRP was further utilized to bind a layer of antibody with high density for efficient capture of analytes owing to the three-dimensional architecture of SPAABs. Using human chorionic gonadotrophin (hCG) as a model analyte, the SPAAB-amplified system drastically boosted the detection limit of ELISA to 0.012 mIU mL(-1), a 267-fold improvement as compared to conventional ELISA systems.

This article describes the utilization of laminar microflows for time-resolved emission measurements with steady-state excitation and detection. Passing a laminar flow through a short illuminated section of a microchannel provided a means for pulsed-like photoexcitation of the moieties carried by the fluid. Imaging the microchannel flows carrying thus photoexcited chelates of lanthanide ions allowed us to extract their excited-state lifetimes from the spatial distribution of the changes in the emission intensity. The lifetime values obtained using this space-domain approach agreed well with the lifetimes from time-domain measurements. This validated space-domain microfluidic approach reveals a means for miniaturization of time-resolved emission spectroscopy.