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In this article, ferric ion-doped floral graphite carbon nitride (Fe–CN-3, energy donor) was used to construct the substrate of the immunosensor and copper oxide nanocubes (Cu 2 O, energy acceptor) were taken as an efficient ECL quenching probe. A sandwich quench electrochemiluminescence (ECL) immunosensor for soluble cytokeratin 19 fragment (Cyfra21-1) detection was preliminarily developed based on a novel resonant energy transfer donor-acceptor pair. Fe–CN-3, a carbon nitride that combines the advantages of metal ion doping as well as morphology modulation, is used in ECL luminophores to provide more excellent ECL performance, which makes a significant contribution to the application and development of carbon nitride in the field of ECL biosensors. The regular shape, high specific surface area and excellent biocompatibility of the quencher Cu 2 O nanocubes facilitate the labeling of secondary antibodies and the construction of sensors. Meanwhile, as an energy acceptor, the UV absorption spectrum of Cu 2 O can overlap efficiently with the energy donor's ECL emission spectrum, making it prone to the occurrence of ECL-RET and thus obtaining an excellent quenching effect. These merits of the donor-acceptor pair enable the sensor to have a wide detection range of 0.00005–100 ng/mL and a low detection limit of 17.4 fg/mL (S/N = 3), which provides a new approach and theoretical basis for the clinical detection of lung cancer. [Display omitted] • A quenched ECL immunosensor prepared based on novel nanocomposites. • Fe3+ was introduced into the "nitrogen tank" of g-C 3 N 4 to improve the ECL performance. • Cu 2 O nanocubes were firstly used as efficient quenching prober of ECL signal. • The designed immunosensor exhibited low detection limit of 17.4 fg/mL for Cyfra21-1. [ABSTRACT FROM AUTHOR]

For the diagnosis and therapy of small cell lung cancer (SCLC), the accurate and sensitive determination of neuron-specific enolase (NSE) content is crucial. This work outlines a dual-quenching electrochemiluminescence resonance energy transfer (ECL-RET) immunosensor based on the double quenching effects of iron base metal organic frameworks (FeMOFs) loaded with small sized CuO nanoparticles (FeMOFs-sCuO) towards CoPd nanoparticles (CoPdNPs) enhanced porous g-C 3 N 4 (P–C 3 N 4 -CoPdNPs). To be specific, we prepared a porous g-C 3 N 4 (P–C 3 N 4) which has a rich porous structure, and significantly increased the specific surface area and the number of reaction sites of P–C 3 N 4. Meanwhile, the CoPdNPs were loaded onto P–C 3 N 4 to improve the ECL luminescence property of P–C 3 N 4 /K 2 S 2 O 8 system through acting as a coreaction accelerator. In addition, the ultraviolet–visible (UV–vis) absorption spectra of FeMOFs and small sized CuO nanoparticles (sCuO) showed considerable overlap with the ECL emission spectra of P–C 3 N 4 appropriately. Therefore, FeMOFs with high specific surface area were prepared and well combined with sCuO to effectively dual-quenching the ECL emission of P–C 3 N 4 based on resonance energy transfer. Hence, a new type ECL-RET couple made up of P–C 3 N 4 -CoPdNPs (donor) and FeMOFs-sCuO (acceptor) were developed for the first time. A certain amount of P–C 3 N 4 -CoPdNPs, Ab 1 , BSA, NSE were modified layer by layer onto the electrode surface. Then FeMOFs-sCuO-Ab 2 bioconjugates was incubated through the immune recognition binding. As a result, a sandwich-type ECL biosensor was manufactured successfully for NSE immunoassay. Under optimal experimental conditions, the limit of detection (LOD) and the limit of quantitation (LOQ) of the prepared ECL sensor for NSE analysis was 20.4 fg mL−1 and 7.99 fg mL−1, respectively, with the relative standard deviation (RSD) of 1.68%. The linear detection range was 0.0000500–100 ng mL−1. The studied immunosensor had satisfactory sensitivity, specificity and reproducibility, manifesting the suggested sensing strategy might offer a good technical means and theoretical basis for the sensitivity analysis of NSE and has a potential application in clinical diagnosis analysis. [ABSTRACT FROM AUTHOR]

This work presents a dual-quenching electrochemiluminescence resonance energy transfer (ECL-RET) immunosensor on account of the double quenching effects of polydopamine coated ZnO nanoflowers (ZnONFs@PDA) loaded with small-sized copper oxide nanoparticles (sCuO), named ZnONFs@PDA-sCuO, towards gold dendrite@polypyrrole core–shell nanoparticles (AuD@PPy) enhanced g-C 3 N 4 (g-C 3 N 4 -AuD@PPy) for sensitive analysis of procalcitonin (PCT). To be specific, AuD@PPy with core-shell structure were loaded onto g-C 3 N 4 to enhance the emission performance of g-C 3 N 4. In addition, the ultraviolet absorption spectra of ZnONFs@PDA and sCuO showed considerable overlap with the ECL emission spectra of g-C 3 N 4 appropriately. So sCuO and ZnONFs@PDA were combined and designed as an efficient dual-quencher of ECL luminescence of g-C 3 N 4 by RET interaction. The biosensor showed superior linear detection range from 0.00005 to 50 ng mL−1, with a sensitive detection limit of 17.2 fg mL−1 (S/N = 3). It is worthy to note that a new type ECL-RET couple made up of g-C 3 N 4 -AuD@PPy (donor) and ZnONFs@PDA-sCuO (acceptor) was developed to construct a sandwich ECL biosensor for PCT detection. The studied immunosensor had satisfactory sensitivity, specificity and reproducibility, indicating the proposed sensing method could provide a good technical means and theoretical basis for the diagnosis of serious diseases. • A new ECL-RET donor-receptor was proposed and fabricated for ultrasensitive detection of PCT. • AuD@PPy nanocomposites with core-shell structure were loaded onto g-C3N4 to enhance the ECL emission performance. • ZnONFs@PDA-sCuO was firstly used as an efficient dual-quenching prober of ECL signal. • The designed immunosensor exhibited low detection limit of 17.2 fg mL-1 for PCT. [ABSTRACT FROM AUTHOR]

• A new ECL-RET donor-receptor was proposed and fabricated for ultrasensitive detection of PCT. • IRMOF-3 not only acted as a carrier for N-GQDs by internal encapsulation and external decoration, but also a coreaction accelerator. • ZnO@Au nanorod was firstly applied as a dual-quenching prober of ECL signal. • The designed immunosensor exhibited low detection limit of 12.58 fg mL−1 for PCT. Herein a novel electrochemiluminescence resonance energy transfer (ECL-RET) pair of isoreticular metal organic framework-3 (IRMOF-3) enriched nitrogen-doped graphene quantum dots (N-GQDs) luminescent material (N-GQDs@IRMOF-3@N-GQDs, donor) and Au nanoparticles modified zinc oxide nanorod (ZnO@Au, acceptor) were firstly designed to fabricate a dual-quenching sandwich-type ECL immunosensor for ultrasensitive analysis of procalcitonin (PCT). IRMOF-3 not only acted as a carrier for abundantly enriching luminescent N-GQDs by internal encapsulation and external decoration, but also a coreaction accelerator which could boost the transformation of persulfate ion S 2 O 8 2− to generate more anion radical SO 4 −, so as to promote the ECL emission of N-GQDs. Additionally, Au nanoparticles were loaded onto the ZnO nanorods through in-situ modification to obtain ZnO@Au, which was firstly applied as a dual-quencher of ECL signal. In the best test environment, a wide detection range from 0.0001 to 100 ng mL−1 was obtained and the limit of detection is 12.58 fg mL−1 (S/N = 3). With excellent reproducibility and sensitivity, the practical test consequence of PCT in human serum samples was satisfactory. These results suggested that this sensing system could provide a reference model for effective detection of disease markers in clinical medicine. [ABSTRACT FROM AUTHOR]