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• 3D Th ing -g-C 3 N 4 had extended π-conjugated system and accelerated electron transfer. • 3D Th ing -g-C 3 N 4 exhibited excellent cathodic ECL performance under lower potential. • The constructed ECL system used dissolved O 2 as the coreactant. • Multiple HCR based cascade amplification strategy was constructed to detecte miRNA. The low electrochemiluminescence (ECL) efficiency and poor ECL stability of graphitic carbon nitride (g-C 3 N 4) under high excitation potential due to obvious electrode passivation seriously restrict its further wider application. Here, construction of intramolecular donor–acceptor (D-A) structure had proposed to well resolve above problems, which had been rarely reported. As a research model, thiophene ring (electron donor, D) with strong electron donating property was doped into the heptazine (electron acceptor, A) of 3D g-C 3 N 4. An intramolecular D-A structure of 3D Th ing -g-C 3 N 4 was obtained, which had extended π-conjugated system and high-speed intramolecular electron transfer. As a result, 3D Th ing -g-C 3 N 4 with intramolecular D-A structure exhibiting excellent cathodic ECL performance with endogenous dissolved O 2 as coreactant under lower potential. Based on the above ECL system, an ultrasensitive biosensor was assembled for microRNA-221 detection with multiple HCR based cascade amplification strategy. The target-like DNA obtained through the initial HCR process induced by target could trigger multiple HCR processes again to realize the effective amplification of the target. The constructed biosensor had excellent detection performance for microRNA-221 and the detection limit was calculated as 5.25 aM. In conclusion, construction of intramolecular D-A structure was a novel and effective way to improve the ECL performance of g-C 3 N 4 , and the newly proposed multiple HCR based cascade amplification strategy paved provided new opportunities for the detection of cancer marker in early cancer diagnosis. [ABSTRACT FROM AUTHOR]

The efficiency of aggregation-induced electrochemiluminescence (AIECL) in tetraphenylethene (TPE) derivatives were significantly enhanced by combining the regulation of molecular structure and solvent. Firstly, the linear increase of the benzene ring resulted in enhanced molecular aggregation and promoted the electrochemical reaction of the anode, due to increased molecular conjugation and higher lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO). The ECL efficiency of 4,4,4,4-(Ethene-1,1,2,2-tetrayl) tetrakis (([1,1,4,1-terphenyl]-4-carbaldehyde)) (T3) nanoparticles (NPs) with more benzene rings were 5558 times that of 4,4,4,4-(ethene-1,1,2,2-tetrayl) tetrabenzaldehyde (T1) NPs, and its relative ECL efficiency of T3 NPs reached 55.58% compared to the [Ru (bpy) 3 ]2+/tripropylamine (TPrA) system. Furthermore, solvents with different polarities played a crucial role in modulating the degree of molecular aggregation, which also effectively facilitated the AIE process and reduced the aggregation-caused quenching (ACQ) effect caused by excessively dense aggregation. This aspect had often been overlooked in previous AIECL studies. T3 NPs demonstrated optimal ECL performance at f w = 70% (f w was the H 2 O content in tetrahydrofuran (THF)/H 2 O), and its ECL efficiency was 232 times greater than f w = 100% and 1853 times greater than f w = 0%. Additionally, it was found that melatonin (MT), one of the hormones widely used to treat insomnia, exhibited antioxidant and free radical scavenging properties, which exerted a significant quenching effect on the ECL of the T3 NPs/TPrA system. Consequently, a sensitive sensing platform was developed for MT with a low detection limit of 8.78 × 10−10 mol L−1, which promoted the application of AIECL in efficient ultra-sensitive biosensing. [ABSTRACT FROM AUTHOR]

• [-TPE-(COOH) 4 -Al-] n with lamellar nanostructure was synthesized through strong chelate effect and π-π stacking. • The obtained [-TPE-(COOH) 4 -Al-] n LNs exhibited excellent AIECL performance. • Combining [-TPE-(COOH) 4 -Al-] n LNs and CSDA strategy with high efficiency, an ultrasensitive ECL biosensor was constructed for miRNA-141 detection. In this work, [-TPE-(COOH) 4 -Al-] n LNs with lamellar nanostructures (LNs) were conveniently synthesized through the high affinity coordination between Al3+ and carboxyl groups of 1,1,2,2-tetra(4-carboxylphenyl)ethylene (TPE-(COOH) 4). As there was a strong chelate effect and π-π stacking, the [-TPE-(COOH) 4 -Al-] n LNs could extend not only on a flat surface, but also in a spatial stack. The obtained [-TPE-(COOH) 4 -Al-] n LNs exhibited excellent aggregation-induced electrochemiluminescence (AIECL) which was much stronger than that of the TPE-(COOH) 4 monomer. Furthermore, through stacking and adjustment of Al3+, they also possessed higher electrochemiluminescence (ECL) efficiency compared to the crystal structure based on TPE-(COOH) 4 , which has a denser aggregation structure that causes aggregation-caused quenching (ACQ) phenomenon. Meanwhile, the [-TPE-(COOH) 4 -Al-] n LNs with Al3+ as the coordination center were superior to the coordination aggregation structures with heavy metal or rare metal ions as the coordination centers in terms of cost and biocompatibility. Using [-TPE-(COOH) 4 -Al-] n LNs as a luminescent material, an ultrasensitive ECL biosensor was fabricated for miRNA-141 detection combined with the cascaded strand displacement amplification (CSDA) strategy. Compared to traditional strand displacement amplification (SDA) reaction, the output DNA usually obtained in the first cycle could further return to attend multiple cycle amplification, resulting in the generation of more output DNA and an obvious signal amplification. The constructed biosensor showed excellent detection performance with a linear range from 1 × 10-18 M to 1 × 10-9 M and a detection limit of 1.2 × 10-19 M. This study provided a more convenient and effective AIECL strategy for tetraphenylethylene (TPE) derivatives and broadened the application of ECL technology in ultra-sensitive biochemical detection. [ABSTRACT FROM AUTHOR]

In this work, the electrochemiluminescence (ECL) phenomenon of three-dimensional graphitic carbon nitride (3D g-C 3 N 4) was reported. Firstly, the proposed 3D g-C 3 N 4 possessed 3D porous interconnected open-framework which enabled faster charge transport and efficient penetration of co-reactants due to "pore confinement effect". Then, we found that the dissolved O 2 could serve as an excellent co-reactant for cathodic ECL of 3D g-C 3 N 4. And the high specific surface area was beneficial to better adsorbing and gathering of dissolved O 2 and reactive oxygen species (ROSs), which made them full contact on the surface or inside of 3D g-C 3 N 4 , giving a more sufficient ECL reaction and higher ECL signal. Based on the proposed 3D g-C 3 N 4 -O 2 ECL system, a sensitive biosensor was constructed for microRNA-21 (miRNA-21) detection with assistance of 3D spherical tracks assisted 3D DNA walking machine, which exhibited superior performance for miRNA-21 with detection limit of 0.22 fM. The proposed 3D g-C 3 N 4 -O 2 ECL system with high ECL efficiency and the effective target conversion and amplification strategies were beneficial to construct ultra-sensitive ECL sensing platform, which would be better applied to clinical bioanalysis. [ABSTRACT FROM AUTHOR]

Here, 3D g-C 3 N 4 with dense N vacancy in its 3D porous interconnected open-framework was synthesized, and the co-reactive 3-(dibutylamino)propylamine (DBAPA) was further covalently coupled onto the surface, resulting in a strong self-enhanced anodic electrochemiluminescence (ECL). Through introduction of high-density N vacancy, for the obtained 3D g–C 3 N 4 –NV, the band gap was broadened and the electrical conductivity was enhanced, realizing an obvious ECL improvement. Moreover, after the covalent binding of co-reactive DBAPA, the obtained 3D g–C 3 N 4 –NV-DBAPA exhibited a more intensive self-enhanced ECL signal due to the higher co-reaction efficiency originated from shorter electron transfer distance and lower energy loss. Based on the high initial signal of the proposed 3D g–C 3 N 4 –NV-DBAPA, a sensitive ECL biosensor with signal "on-off" was fabricated in assistance with multiple horizontal ordered hybridization chain reaction (HO-HCR). Through orderly fixing the reacted DNA chains on the Y-shape DNA structure on the electrode could effectively decrease diffusion process and improve the reaction efficiency of HCR process, resulting in the formation of numerous long horizontal double-strand DNA that could immobilize abundant ferrocene-doxorubicin (Fc-Dox) with ECL quenching effect. Meanwhile, compared to the traditional vertical HCR, the HO-HCR could make the quench reagent closer to the ECL emitter on the electrode surface and obtain a more effective quenching effect to enhance the sensing sensitivity. As a result, the proposed ECL biosensor archived the sensitive measurement of staphylococcus aureus with a detection limit of 10.3 aM. The anodic ECL of 3D g-C 3 N 4 was firstly explored, which is greatly improved by introducing high-density N vacancy to change its electron structure and intramolecular self-enhanced path to enhance co-reaction efficiency. Using the proposed 3D g–C 3 N 4 –NV-DBAPA as ECL emitter, a sensitive "on-off" ECL biosensor for staphylococcus aureus was fabricated in assistance with multiple horizontal ordered hybridization chain reaction for high effective signal amplification. [Display omitted] • High-density N vacancy was induced to improve the anodic ECL of 3D g-C 3 N 4. • 3D g–C 3 N 4 –NV-DBAPA has high self-enhanced anodic ECL by intramolecular catalysis. • Multiple horizontal ordered HCR was designed for signal amplification. • An ECL biosensor for sensitive staphylococcus aureus detection was constructed. [ABSTRACT FROM AUTHOR]