Atom-Anchoring Strategy with Metal-Organic Frameworks for Highly Efficient Solid-State Electrochemiluminescence

Dual-wavelength electrochemiluminescence biosensor based on a multifunctional Zr MOFs@PEI@AuAg nanocomposite with intramolecular self-enhancing effect for simultaneous detection of dual microRNAs

Rapid parallel detection of multi-targets has always been an exploration aim in electrochemiluminescence (ECL) assays. Herein, a multifunctional nanocomposite of Zr metal-organic frameworks (MOFs) @PEI@AuAg nanoclusters (NCs) with intense and stable dual-wavelength ECL was synthesized for the first time, and used to construct a new ECL biosensor for rapid simultaneous detection of dual targets. Notably, the novel ECL emitter Zr MOFs with high-performance was not only integrated with a co-reactant polyethyleneimine (PEI) to form a unique intramolecular self-enhancing structure, but also loaded a large number of another ECL emitter AuAg NCs, furthermore, AuAg NCs with superior electron transfer property can much enhance the electrical conductivity of the composites, thus achieving the goal of "killing three birds with one stone". Moreover, a unique stable and rigid three-dimensional DNA tetrahedron (TDN) structure was connected with two quenching probes BHQ1 and BHQ3 and immobilized on the composites-modified electrode, so ECL emission of the nanocomposites at two wavelengths of 535 nm and 644 nm were both quenched by resonance energy transfer (RET). In the presence of target miRNAs, the efficient DNA cycling double-amplification processes were performed by using exonuclease (T7 Exo) combined with DNA Walker, thus both quenching groups were separated to restore the ECL at two wavelengths, achieving simultaneous and rapid ECL detection of two miRNAs. Therefore, this present work not only opens a unique nanocomplex with dual wavelength ECL and self-enhancing performance, but also develops a highly sensitive ECL biosensor with promising value for rapid multi-target analysis in clinical fields.

Enhancing Electrochemiluminescence Efficiency through Introducing Atomically Dispersed Ruthenium in Nickel-Based Metal-Organic Frameworks

The successful application of electrochemiluminescence (ECL) in various fields required continuous exploration of novel ECL signal emitters. In this work, we have proposed a pristine ECL luminophor named NiRu MOFs, which owned extremely high and stable ECL transmission efficiency and was synthesized via a straightforward two-step hydrothermal pathway. The foundation framework of pure Ni-MOFs with the initial structure was layered-pillared constructed by the coordinated octahedrally divalent between nickel and terephthalic acid (BDC). The terephthalates were coordinated and pillared directly to the nickel hydroxide layers and the three-dimensional framework was formed, which had a weak ECL response strength. Then, the ruthenium pyridine complex was recombined with pure Ni-MOFs to produce NiRu MOFs and part of the introduced ruthenium was atomically dispersed in the layered-pillared structure through an ion-exchange method, which led to the ECL luminous efficiency being significantly boosted more than pure Ni-MOFs. In order to verify the superiority of this newly synthesized illuminant, an ECL immunoassay model has been designed, and the results demonstrated that it had extremely strong and steady signal output in practical application. This study realized an efficient platform in ECL immunoassay application with the limit of detection of 0.32 pg mL^-1 for neuron-specific enolase (NSE). Therefore, the approach which combined the pristine pure Ni-MOFs and the star-illuminant ruthenium pyridine complex would provide a convenient and meaningful solution for exploring the next-generation ECL emitters.

Polymer Carbon Nanodots: A Novel Electrochemiluminophore for Dual Mode Detection of Ferric Ions

The development of simple and effective dual-mode analytical methods plays crucial regulatory roles in the discrimination of relevant target species, because of their built-in cross reference correction and high accuracy. In this work, a novel polymer carbon nanodots (PCNDs) prepared from a facile one-pot hydrothermal procedure using readily available l-tryptophan and l-phenylalanine as precursors, showed excellent aqueous solubility and blue fluorescence property with a high quantum yield of 29%. Moreover, the PCNDs was demonstrated to be a robust luminophore with electrochemiluminescence (ECL) efficiency of 43% was achieved by using K₂S₂O₈ as a coreactant. The spooling ECL spectroscopy was employed to take insight into excited states responsible for the potential-dependent ECL emissions. Most importantly, when introduced into construction of the fluorescence and ECL dual mode sensing platform, for the first time, the PCNDs displayed prominent performance for the detection of ferric ions (Fe³⁺). The ferric ions could be quantified ranging from micromolar to millimolar with a detection limit of 0.22 and 5.3 μM, respectively. Such a dual-functional sensing platform also exhibits excellent selectivity, reproducibility and stability. Results from this work indicate that PCNDs showing great promise as a bright luminophore for the fabrication of low-cost, high-performance dual-signal readout platforms for ferric ions determination.

A fluorescence nanoplatform for the determination of hydrogen peroxide and adenosine triphosphate via tuning of the peroxidase-like activity of CuO nanoparticle decorated UiO-66

A novel nanocomposite of CuO nanoparticle-modified Zr-MOF (CuO/UiO-66) was synthesized and developed as a fluorescence nanoplatform for H₂O₂ and adenosine triphosphate (ATP) via the "turn-on-off" mode in the presence of terephthalic acid (TA). The structure of CuO/UiO-66 was thoroughly characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and other techniques. The CuO/UiO-66 with enhanced peroxidase-like (POD) activity obtained due to the Zr⁴⁺ in UiO-66 is beneficial to the aggregation of CuO NPs on its surface. As a result, the strengthened fluorescence at 425 nm with the excitation of 300 nm was found due to the highly fluorescent species of TAOH. This is produced by the oxidation of TA by ·OH that came from the catalysis of H₂O₂ via the peroxidase mimic of CuO/UiO-66. Hence the modification of CuO NPs on porous UiO-66 can provide a friendly and sensitive physiological condition for H₂O₂ detection. However, upon addition of ATP, the fluorescence intensity of TAOH at 425 nm effectively declined owing to the formation of complexation of Zr⁴⁺-ATP and the interaction of CuO to ATP which hampers the catalytic reaction of CuO/UiO-66 to H₂O₂. The specific interaction induced "inhibition of the peroxide-like activity" endows the sensitive and selective recognition of ATP. The detection limits were 16.87 ± 0.2 nM and 0.82 ± 0.1 nM, and linear analytical ranges were 0.02-100 μM and 0.002-30 μM for H₂O₂ and ATP, respectively. The novel strategy was successfully applied to H₂O₂ and ATP determination in serum samples with recoveries of 97.2-103.8% for H₂O₂ and 97.6-101.7% for ATP, enriching the avenue to design functional MOFs and providing new avenue of multicomponent bioanalysis.

Au25 Nanoclusters Exhibit Superhigh Catalytic Activity in Electrochemical Detection of As(III)

An atomic-level Au nanocluster, as an excellent photocatalyst, is generally not considered as an efficient electrocatalyst due to its poor stability. Herein, a method is proposed to stabilize abundant Au₂₅ on Fe₂O₃ nanoplates (Au₂₅/OV-Fe₂O₃) successfully with oxygen vacancies (OV) created. Au₂₅/OV-Fe₂O₃ shows superhigh catalysis in the electrochemical reduction toward As(III). The record-breaking sensitivity (161.42 μA ppb^-1) is two orders of magnitude higher than currently reported, where an ultratrace limit of detection (9 ppt) is obtained, suggesting promising applications in the analysis of organic and bioactive substances. The stability of Au₂₅ is attributed to the Au-Fe bond formed after loading Au₂₅ nanoclusters on Fe₂O₃ nanoplates through "electron compensation" and bond length (Au-S) shortening. Moreover, the ligand S atoms in Au₂₅ nanoclusters significantly contribute to the reduction of As(III). The fantastic stability and superior catalytic ability of Au₂₅/OV-Fe₂O₃ provide guidelines to stabilize Au nanoclusters on metal oxides, indicating their potential electroanalytical applications.