In this work, boron and nitrogen-codoped carbon dots (BN-CDs) as highly efficient electrochemiluminescence (ECL) emitters with advantages of low excitation potential and high ECL efficiency were prepared to establish a novel ternary ECL system for ultrasensitive detection of HBV-DNA. Especially, both platinum nanoflowers (Pt NFs) and boron radicals (B • ) from the BN-CDs could accelerate the reduction of coreactant S 2 O 8 2− to abundant SO 4•− simultaneously, making the BN-CDs have outstanding ECL performance. Impressively, the ECL efficiency of BN-CDs is much higher than that of nondoped CDs and singledoped CDs. In addition, by combining the novel ECL ternary system with the exonuclease III (Exo III)-induced target DNA amplification strategy, an ECL biosensor was constructed to realize the ultrasensitive detection of HBV-DNA from 100 aM to 1 nM, while the limit of detection was 18.08 aM. Therefore, a promising highly efficient ECL emitter was offered to develop a novel ECL detection method for clinical disease analysis.

Herein, the novel alloyed silver gold sulfur quantum dots (AgAuS QDs) with highly efficient near-infrared (NIR) electrochemiluminescence (ECL) emission at 707 nm were successfully prepared to construct a biosensing platform for ultrasensitive detection of microRNA-222 (miRNA-222). Interestingly, AgAuS QDs revealed excellent ECL efficiency (34.91%) compared to that of Ag2S QDs (10.30%), versus the standard [Ru­(bpy)3]2+/S2O8 2– system, which benefited from the advantages of abundant surface defects and narrow bandgaps by Au incorporation. Additionally, an improved localized catalytic hairpin self-assembly (L-CHA) system was developed to display an increased reaction speed by improving the local concentration of DNA strands, which addressed the obstacles of time-consuming traditional CHA systems. As a proof of concept, based on AgAuS QDs as an ECL emitter and improved localized CHA systems as a signal amplification strategy, a “signal on–off” ECL biosensor was developed to exhibit a superior reaction rate and excellent sensitivity with a detection limit of 10.5 aM for the target miRNA-222, which was further employed for the analysis of miRNA-222 from cancer cell (MHCC-97L) lysate. This work advances the exploration of highly efficient NIR ECL emitters to construct an ultrasensitive biosensor for the detection of biomolecules in disease diagnosis and NIR biological imaging.

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In this study, nitrogen-, sulfur-, and fluorine-codoped carbon dots (NSF-CDs) with high electrochemiluminescence (ECL) efficiency were developed as novel emitters to fabricate an ECL biosensor for sensitive detection of matrix metalloproteinase 2 (MMP-2). Impressively, compared to previously reported CDs, NSF-CDs with narrow band gap not only decreased the excitation voltage to reduce the side reaction and the damage on biomolecules but also had hydrogen bonds to vastly enhance the ECL efficiency. Furthermore, an improved exonuclease III (Exo III)-assisted nucleic acid amplification method was established to convert trace MMP-2 into a mass of output DNA, which greatly improved the target conversion efficiency and ECL signal. Hence, the ECL biosensor has realized the sensitive detection of MMP-2 proteins from 10 fg/mL to 10 ng/mL with a limit of detection of 6.83 fg/mL and has been successfully applied in the detection of MMP-2 from Hela and MCF-7 cancer cells. This strategy offered neoteric CDs as ECL emitters for sensitive testing of biomarkers in medical research.

Herein, Zn 2+ -induced gold cluster aggregation (Zn 2+ -GCA) as a high-efficiency electrochemiluminescence (ECL) emitter is first employed to construct an ECL biosensor to ultrasensitively detect microRNA-21 (miRNA-21). Impressively, Zn 2+ not only can induce the aggregation of monodispersed gold clusters (Au NCs) to limit the ligand vibration of Au NCs for improving ECL emission but also can be utilized as a coreaction accelerator to catalyze the dissociation of coreactant S 2 O 8 2− into sulfate radicals (SO 4•− ) to improve the interaction efficiency between Zn 2+ -GCA and S 2 O 8 2− , resulting in further intense ECL emission. Compared to Au NCs stabilized by bovine serum albumin with ECL efficiency of 0.40%, Zn 2+ -GCA possessed high ECL efficiency of 10.54%, regarding the [Ru(bpy) 3 ] 2+ /S 2 O 8 2− system as a standard. Furthermore, output DNA modified with poly adenine (polyA) obtained from enzyme-free target recycling amplification can be efficiently immobilized on the surface of gold nanoparticles (Au NPs) to reduce the defect of special design, cumbersome operation, and low stability. Thus, an ultrasensitive ECL biosensor based on the Zn 2+ -GCA/S 2 O 8 2− ECL system and enzyme-free target recycling amplification achieved ultrasensitive detection of miRNA-21 with the detection limit of 44.7 aM. This strategy presents a new idea to design highly efficient ECL emitters, which is expected to be used in the field of bioanalysis for clinical diagnosis.