low background interference, and easy operation. [4][5][6][7] Nowadays, ECL with these favorable benefits has become one powerful analytical technique applied in biomarkers, food safety, and environmental pollutants analyses. [8][9][10][11] As it is well known, the high sensitivity for the ECLbased immunoassays was mainly attributable to the excellent luminophores. [12] At present, most of the reported methods used nanomaterials like multi-porous nanoparticles (NPs) [13,14] or metal−organic frameworks (MOFs) [15][16][17] as carriers to immobilize the typical ECL emitters, including luminol, tris-bipyridyl ruthenium (Ru(bpy) 3 2+), and their derivatives. [1] In particular, MOFs have received intense attention in ECL analysis because of their high poriness, easy functionalization, and ultrahigh surface area. [18][19][20] Nonetheless, these nanomaterials based strategies for luminophores immobilization by postmodification or encapsulation, still exist some shortcomings when used in aqueous phase. For instance, the poor stability of MOFs in water would result in leakage of ECL chromophores, and the large steric hindrance of organic luminophores limited the loading capacity to some extent, which both abridged their in-depth application in ECL bioassays. Thus, without the trivial post-synthetic steps, it seems an ideal way to design innovative ECL luminophores based MOFs that emitted light by themselves.Currently, some groups have reported that the Ru(bpy) 3 2+ derivatives, could be employed as organic ligands to fabricate MOFs with self-luminescent properties. [21,22] To some extent, the aggregation-caused quenching (ACQ) effect [23,24] was unavoidable due to the π-π stacking of the aggregated luminescent centrosome. Fortunately, aggregation-induced emission (AIE), which was proposed by Tang and co-workers in 2001, [25] paved a new avenue to resolve this problem. So far, a variety of AIE luminogens (AIEgens)-based nanomaterials have been widely applied in the fields of solid-state optoelectronic devices, [26,27] fluorescence imaging, [28] and biosensors, [29][30][31] because the AIEgens displayed strong emission in aggregated state but almost nonemissive in diluted solution with molecule-free state. [32] Inis widely known that high-performance electrochemiluminescence (ECL) emitters play a crucial part in improving the detection sensitivity of the ECL strategy. Through the combination of aggregation-induced emission luminogens (AIEgens), 1,1,2,2-tetra(4-carboxylbiphenyl)ethylene (H 4 TCBPE) with Zr(IV) cations, a dumbbell plate-shaped metal−organic framework (MOF) with high luminous efficiency is synthesized as ECL tags. The resultant MOF exhibits stronger ECL activity than those of H 4 TCBPE monomers and aggregates. Herein, this phenomenon is defined as the coordination-triggered electrochemiluminescence (CT-ECL) enhancement effect. Furthermore, the nearly matched ECL and photoluminescence (PL) spectra imply the bandgap emission mechanism. Remarkably, polyethyleneimine (PEI) as the coreactant is covalently connected ...

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The combination of fluorescent nanoparticles and specific molecular probes appears to be a promising strategy for developing fluorescent nanoprobes. In this work, L-cysteine (L-Cys) capped Fe3O4@ZnO core-shell nanoparticles were synthesized for the highly selective detection of Fe3+. The proposed nanoprobe shows excellent fluorescent property and high selectivity for Fe3+ due to the binding affinity of L-Cys with Fe3+. The binding of Fe3+ to the nanoprobe induces an apparent decrease of the fluorescence. Thus a highly selective fluorescent chemosensor for Fe3+ was proposed based on Fe3O4@ZnO nanoprobe. The magnetism of the nanoprobe enables the facile separation of bound Fe3+ from the sample solution with an external magnetic field, which effectively reduces the interference of matrix. The detection limit was 3 nmol L−1 with a rapid response time of less than 1 min. The proposed method was applied to detect Fe3+ in both serum and wastewater samples with acceptable performance. All above features indicated that the proposed fluorescent probe as sensing platform held great potential in applications of biological and analytical field.

The evolution of electrochemiluminescence (ECL) emission amplified by coreaction accelerator in near-infrared (NIR) area has been overwhelmingly anticipated for ultrasensitive detection of disease biomarkers. Herein, the hollow double-shell CuCo 2 O 4 @Cu 2 O (HDS-CuCo 2 O 4 @Cu 2 O) heterostructures were conveniently prepared and utilized as an attractive coreaction accelerator to improve the NIR ECL performance of gold nanoclusters (AuNCs) for the first time. Benefiting from perfectmatched lattice spacing, unique Cu 2 O nanoparticles (NPs) were formed in situ on the layered-hollow CuCo 2 O 4 nanospheres (NSs) to obtain HDS-CuCo 2 O 4 @Cu 2 O heterostructures. The formed heterojunctions supplied shorter charge transfer distance and better interfacial charge transfer efficiency as well as more effective separation performance. Consequently, HDS-CuCo 2 O 4 @Cu 2 O heterostructures as an admirable electroactive substrate could significantly promote the formation of sufficient coreactant intermediate radicals to react with AuNCs cationic radicals, realizing about 3-folds stronger NIR ECL response than that of individual AuNCs. In addition, the AuNCs templated by L-methionine (L-Met) exhibited NIR ECL emission around 830 nm, which could decrease the photochemical damage to even realize a nondestructive detection with improved susceptibility and circumambient adaptability. Subsequently, a well site-oriented fixation strategy utilizing HWRGWVC heptapeptide as the specific antibody immobilizer was introduced to further preserve the bioactivity of antibody on the HDS-CuCo 2 O 4 @Cu 2 O and AuNCs surface along with enhancing the incubation performance markedly. In view of the progressive sensing mechanism, a NIR immunosensor was obtained for the ultrasensitive analysis of CYFRA21−1, which achieved a broad linear ranging from 2 fg/mL to 50 ng/mL and a low limit of detection (LOD) of 0.67 fg/mL (S/N = 3).

An innovative self-powered microfluidic photoelectrochemical (PEC) aptasensor was developed that uses photoactive AgBr/CuBi2O4 (ACO) composites as the photocathode matrix for ultrasensitive detection of ciprofloxacin (CIP) and ofloxacin (OFL). The formation of direct Z-scheme heterojunctions in ACO composites greatly aided electron/hole pair separation. Meanwhile, ZnIn2S4-decorated CdS nanorod arrays (CZIS) as the photoanode were used instead of a platinum counter electrode to provide electrons. The “signal-off” CIP detection was accomplished through the steric hindrance effect in the photoanode due to the combination of aptamer(CIP) and CIP. To increase the cathodic photocurrent intensity for OFL determination, controlled release of luminol was first used. Luminol molecules were successfully embedded in the porous structure of silicon dioxide nanospheres (PSiO2) by the electrostatic adsorption between PSiO2 and aptamer(OFL). The luminol released by specific recognition between OFL and aptamer(OFL) could not only react with •O2 – but also produce chemiluminescence emission, resulting in the “signal-on” state. Because of the signal “on–off–on”, the proposed aptasensor exhibited wide linear ranges for CIP (0.001–100 ng/mL) and OFL (0.0005–100 ng/mL) detection. Furthermore, the low detection limits of CIP (0.06 pg/mL) and OFL (0.022 pg/mL) could achieve the ultrasensitive analysis.