In this work, a novel self-enhanced solid state electrochemiluminescence (ECL) platform, based on polyethyleneimine (PEI) capped CdS quantum dots (PEI-CdS QDs) as coreactant and [email protected] 2 @Ru(bpy) 3 2+ doped silica ( [email protected] 2 @RuDS) nanocomposite as ECL emitter, was constructed. The PEI-CdS QDs integrated double coreactant of PEI and CdS QDs, thus significantly promoted the ECL of [email protected] 2 @RuDS. Polyaniline hydrogel was introduced to boost the electron transfer and to improve the immobilization of PEI-CdS/ [email protected] 2 @RuDS. In addition, creatinine imprinted poly(o-aminophenol) film was electrodeposited on the PEI-CdS/ [email protected] 2 @RuDS surface as recognition element. Thus, the obtained sensor possessed high sensitivity, stability, reproducibility and selectivity for creatinine sensing. The change of ECL intensity and logarithm of creatinine concentration showed a good linear relationship in the range of 0.05 nM to 5 μM, and the detection limit was low to 0.02 nM. The sensor was applied to detect creatinine in human serum and urine samples, and the results were in good agreement with those of commercial enzyme-linked immunosorbent assay kit.
CdTe quantum dots (QDs) were integrated with polyethyleneimine-coated carbon dots (PEI-CDs) to form a dually emitting probe for heparin. The red fluorescence of the CdTe QDs is quenched by the PEI-CDs due to electrostatic interactions. In the presence of heparin, the blue fluorescence of PEI-CDs remains unaffected, while its quenching effect on the fluorescence of CdTe QDs is strongly reduced. A ratiometric fluorometric assay was worked out. The ratio of the fluorescences at 595 and 436 nm serves as the analytical signal. Response is linear in the concentration range of 50–600 ng·mL −1 (0.1–1.2 U·mL −1 ) of heparin. The limit of detection is 20 ng·mL −1 (0.04 U·mL −1 ). This makes the method a valuable tool for heparin monitoring during postoperative and long-term care. This assay is relatively free from the interference by other analogues which commonly co-exist with heparin in samples, and it is more robust than single-wavelength based assays.
In the presence of heparin, the fluorescence of polyethyleneimine-coated carbon dots (PEI-CDs) at 436 nm remains unaffected, while its quenching effect on the fluorescence of CdTe at 595 nm is strongly reduced.
In this study, a novel potential-resolved ratiometric electrochemiluminescence (ECL) sensor, using Ru(bpy) 3 2+ doped TiO 2 nanoparticles (TiO 2 -Ru(bpy) 3 2+ NPs) with polyethyleneimine (PEI) capped CdS quantum dots (PEI-CdS QDs) as new ECL emitter unit and molecularly imprinted polymer (MIP) as recognition element, was proposed for the first time. Owing to the large specific surface area and porosity of TiO 2 NPs plentiful Ru(bpy) 3 2+ was well immobilized on them. The obtained TiO 2 -Ru(bpy) 3 2+ NPs were able to catalyze the reduction of coreactant H 2 O 2 of PEI-CdS QDs, while the PEI-CdS QDs could serve as the coreactant of TiO 2 -Ru(bpy) 3 2+ NPs, thus their ECL was promoted by each other. Additionally, graphene oxide (GO) was used to facilitate the electron transfer and sialic acid (SA) imprinted poly(3-aminophenylboronic acid) was electrodeposited on the resulting GO/TiO 2 -Ru(bpy) 3 2+ @PEI-CdS/GCE. When SA concentration increased the anodic ECL signal from TiO 2 -Ru(bpy) 3 2+ NPs increased, while the cathodic ECL signal from PEI-CdS QDs declined. The sensor exhibited high sensitivity, selectivity and stability. Under the optimized conditions, the linear range was 1.0 nM - 0.1 mM and the detection limit was low to 0.017 nM (S/N = 3). Its good practical feasibility was confirmed by detecting SA in real samples with satisfactory results.
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