Overcoming Aggregation-Induced Quenching by Metal-Organic Framework for Electrochemiluminescence (ECL) Enhancement: Zn-PTC as a New ECL Emitter for Ultrasensitive MicroRNAs Detection.

Polycyclic aromatic hydrocarbons (PAHs) as traditional electrochemiluminescence (ECL) luminophores have been widely applied in the analysis field. However, their ECL intensity and efficiency are still limited due to the aggregation-induced quenching (ACQ) effect of PAHs. Hence, to overcome this limitation, we put forward a new strategy to increase the ECL intensity and efficiency by eliminating the ACQ effect of PAHs through the coordinative immobilization of PAHs within metal-organic frameworks (MOFs). As anticipated, the proof-of-concept experiment indicated that the coordinative immobilization of perylene-3,4,9,10-tetracarboxylate (PTC) into a Zn-PTC MOF could distinctly increase the ECL intensity and efficiency compared with H4PTC aggregates and H4PTC monomers. The reason for the ECL enhancement of Zn-PTC was that the immobilization of PTC within the MOF effectively amplified the distance between perylene rings of PTC ligands and thus eliminated the ACQ effect. Furthermore, the PTC into Zn-PTC was stacked in an edge-to-edge mode to form J-aggregation, which was also conducive to ECL enhancement. On the basis of the excellent ECL performance, we utilized Zn-PTC as a new ECL emitter combined with exonuclease III-stimulated target cycling and DNAzyme-assisted cycling dual amplification strategies to construct an ECL sensor for microRNA-21 detection, which had a wide signal response (100 aM to 100 pM) with a detection limit of 29.5 aM. Overall, this work represents a new and convenient method to overcome the ACQ effect of PAHs and boost the ECL performance, which opens a new horizon for developing high-performance ECL materials, thus offering more opportunities for building highly sensitive ECL biosensors.

An AIEgen-based 2D ultrathin metal-organic layer as an electrochemiluminescence platform for ultrasensitive biosensing of carcinoembryonic antigen.

In this work, a novel two-dimensional (2D) ultrathin metal-organic layer (MOL) based on the aggregation-induced emission (AIE) ligand H4ETTC (H4ETTC = 4',4''',4''''',4'''''''-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1'-biphenyl]-4-carboxylic acid))) was developed and used to construct a novel electrochemiluminescence (ECL) aptasensor for ultrasensitive detection of carcinoembryonic antigen (CEA). The newly synthesized AIE luminogen (AIEgen)-based MOL (Hf-ETTC-MOL) yielded a higher ECL intensity and efficiency than did H4ETTC monomers, H4ETTC aggregates and 3D bulk Hf-ETTC-MOF. This improvement occurred not only because the ETTC ligands were coordinatively immobilized in a rigid MOL matrix, which restricted the intramolecular free rotation and vibration of these ligands and then reduced the non-radiative transition, but also because the porous ultrathin 2D MOL greatly shortened the transport distances of ions, electrons, coreactant (triethylamine, TEA) and coreactant intermediates (TEA˙ and TEA˙+), which made more ETTC luminophores able to be excited and yielded a high ECL efficiency. On the basis of using the Hf-ETTC-MOL as a novel ECL emitter and rolling circle amplification (RCA) as a signal amplification strategy, the constructed ECL aptasensor exhibited a linear range from 1 fg mL-1 to 1 ng mL-1 with a detection limit of 0.63 fg mL-1. This work has opened up new prospects for developing novel ECL materials and is expected to lead to increased interest in using AIEgen-based MOLs for ECL sensing.

Diaqua-(5-carb-oxy-benzene-1,3-dicarboxyl-ato-κO(1))[8-ethyl-5-oxo-2-(piperazin-4-ium-1-yl)-5,8-dihydro-pyrido[2,3-d]pyrimidine-6-carboxyl-ato-κ(2)O(5),O(6)]zinc monohydrate.

In the title compound, [Zn(C(14)H(17)N(5)O(3))(C(9)H(4)O(6))(H(2)O)(2)]·H(2)O, the complex mol-ecule exists in a zwitterionic form. The Zn(II) ion exhibits a distorted tetra-gonal-pyramidal geometry, being coordinated by two O atoms from the zwitterionic 8-ethyl-5-oxo-2-(piperazin-4-ium-1-yl)-5,8-dihydro-pyrido[2,3-d]pyrimidine-6-carboxyl-ate (L) ligand, one O atom from the 5-carb-oxy-benzene-1,3-dicarboxyl-ate dianion, [Hbtc](2-), and two O atoms from two aqua ligands. In the crystal, N-H⋯O and O-H⋯O hydrogen bonds link the components into a three-dimensional structure. The crystal packing exhibits π-π inter-actions between the aromatic rings, with centroid-centroid distances in the range 3.466 (3)-3.667 (3) Å.