Translation of the highly promising electrogenerated chemiluminescence (ECL) properties of Ir(
iii
) complexes (with tri-
n
-propylamine (TPrA) as a co-reactant) into a new generation of ECL labels ...for ligand binding assays necessitates the introduction of functionality suitable for bioconjugation. Modification of the ligands, however, can affect not only the photophysical and electrochemical properties of the complex, but also the reaction pathways available to generate light. Through a combined theoretical and experimental study, we reveal the limitations of conventional approaches to the design of electrochemiluminophores and introduce a new class of ECL label, Ir(C^N)
2
(pt-TOxT-Sq)
+
(where C^N is a range of possible cyclometalating ligands, and pt-TOxT-Sq is a pyridyltriazole ligand with trioxatridecane chain and squarate amide ethyl ester), which outperformed commercial Ir(
iii
) complex labels in two commonly used assay formats. Predicted limits on the redox potentials and emission wavelengths of Ir(
iii
) complexes capable of generating ECL
via
the dominant pathway applicable in microbead supported ECL assays were experimentally verified by measuring the ECL intensities of the parent luminophores at different applied potentials, and comparing the ECL responses for the corresponding labels under assay conditions. This study provides a framework to tailor ECL labels for specific assay conditions and a fundamental understanding of the ECL pathways that will underpin exploration of new luminophores and co-reactants.
A new strategy to create iridium(
iii
)-based ECL labels reveals limitations of conventional approaches.
Alzheimer's disease is the most common form of age-related neurodegenerative dementia. The disease is characterised by the presence of plaques in the cerebral cortex. The major constituent of these ...plaques is aggregated amyloid-β peptide. This review focuses on the molecular aspects of metal complexes designed to bind to amyloid-β. The development of radioactive metal-based complexes of copper and technetium designed as diagnostic imaging agents to detect amyloid burden in the brain is discussed. Separate sections of the review discuss the use of luminescent metal complexes to act as non-conventional probes of amyloid formation and recent research into the use of metal complexes as inhibitors of amyloid formation and toxicity.
Controlling electrochemiluminescence (ECL) color(s) is crucial for many applications ranging from multiplexed bioassays to ECL microscopy. This can only be achieved through the fundamental ...understanding of high-energy electron-transfer processes in complex and competitive reaction schemes. Recently, this field has generated huge interest, but the effective implementation of multicolor ECL is constrained by the limited number of ECL-active organometallic dyes. Herein, the first self-enhanced organic ECL dye, a chiral red-emitting cationic diaza 4helicene connected to a dimethylamino moiety by a short linker, is reported. This molecular system integrates bifunctional ECL features (
i.e.
luminophore and coreactant) and each function may be operated either separately or simultaneously. This unique level of control is enabled by integrating but decoupling both molecular functions in a single molecule. Through this dual molecular reactivity, concomitant multicolor ECL emission from red to blue with tunable intensity is readily obtained in aqueous media. This is done through competitive electron-transfer processes between the helicene and a ruthenium or iridium dye. The reported approach provides a general methodology to extend to other coreactant/luminophore systems, opening enticing perspectives for spectrally distinct detection of several analytes, and original analytical and imaging strategies.
Controlling electrochemiluminescence (ECL) color(s) is crucial for many applications ranging from multiplexed bioassays to ECL microscopy.
Surface initiated electro-polymerization of acrylamide on carbon fiber with methodically varied amounts of acrylamide monomer and N,N′-methylene bis-acrylamide crosslinker is explored in this study. ...The effect of the polymer coating on tensile strength, Young's modulus, and interfacial properties of carbon fibre in an epoxy resin was determined. A significant improvement in tensile strength, tensile modulus, and interfacial shear strength (IFSS) across all modified samples was observed, with the most notable improvements to tensile strength, tensile modulus and IFSS being 38%, 15% and 192.5%, respectively. This covalently bound polymer coating provides the best kind of solution for the two most crucial limitations of carbon fibre, with the minimum amount of effort, time, and cost.
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Iridium(III) complexes, exhibiting high luminescence quantum yields and a wide range of emission colours, are promising alternatives to tris(2,2ʹ-bipyridine)ruthenium(II) for chemiluminescence (CL) ...and electrochemiluminescence (ECL) detection. This emerging class of reagent, however, is limited by the poor solubility of many iridium(III) complexes in aqueous solution, and lack of understanding of their remarkably variable selectivities towards different analytes.
Seven Ir(C^N)2(pt-TEG)+ complexes, exhibiting a wide range of reduction potentials and emission energies, were examined with six model analytes. For CL, cerium(IV) was used as the oxidant. The alkylamine analytes generally produced greater CL and ECL with the more readily oxidised Ir(III) complexes (C^N = piq, bt, ppy), predominantly through the ‘direct’ pathway requiring oxidation of both metal complex and analyte. Aniline derivatives that did not also contain secondary or tertiary alkylamines elicited CL from the less readily oxidised complexes (C^N = df-ppy-CF3, df-ppy) via energy transfer. The most difficult to oxidise complexes (C^N = df(CF3)-ppy-Me, df(CN)-ppy) gave poor responses due to the limited potential window of the solvent and inefficiency of energy transfer to their high energy excited states. Greater CL and/or ECL intensities were generally obtained for each analyte with at least one Ir(III) complex than with Ru(bpy)32+; superior limits of detection for two analytes were demonstrated.
This exploration of CL/ECL in which the properties of luminophore, analyte and oxidant are all varied provides a new understanding of the influence of the metal-complex potentials and excited state energy on the light-producing and quenching pathways, and consequently, their distinct selectivity towards different analytes. These findings will guide the development of water-soluble Ir(III) complexes as CL and ECL reagents.
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•Chemiluminescence of seven water-soluble Ir(III) complexes with six analytes explored.•Selectivity determined in part by the availability of different reaction pathways.•Superior limits of detection were obtained compared to the conventional Ru(II) complex.•Complexes with highest oxidation potentials were poor (electro)chemiluminophores.
Inverse vulcanization of waste or renewable dienes has generated materials with phenomenal properties across a spectrum of applications. Nevertheless, the use of these materials for structural ...applications remains a challenge. Here, the use of an inverse vulcanized cyclopentadiene polymer as a resin for carbon fiber reinforced composites is explored. The dynamic S─S bonds in the polymer matrix are used to repair composite specimens over 5 generations by heating the material to 140 °C. A range of composites are manufactured and evaluated for their flexural properties, using a range of fiber orientations. Finally, this polymer is used to reinforce a carbon fiber fabric composed entirely of reclaimed materials, constituting a composite entirely composed of waste materials and second life carbon fibers.
With the ability to synthesis shelf stable, rehealable sulfur‐based copolymers in hand, this paper aims to highlight a means to improve their structural integrity using carbon fiber reinforcements in hopes to further widen the scope of applications these polymers can have. Furthermore, the repair capabilities of these composites over 5 consecutive generations are assessed and reported.
Preliminary explorations of the annihilation electrogenerated chemiluminescence (ECL) of mixed metal complexes have revealed opportunities to enhance emission intensities and control the relative ...intensities from multiple luminophores through the applied potentials. However, the mechanisms of these systems are only poorly understood. Herein, we present a comprehensive characterisation of the annihilation ECL of mixtures of tris(2,2'-bipyridine)ruthenium(ii) hexafluorophosphate (Ru(bpy)
(PF
)
) and
-tris(2-phenylpyridine)iridium(iii) (Ir(ppy)
). This includes a detailed investigation of the change in emission intensity from each luminophore as a function of both the applied electrochemical potentials and the relative concentrations of the two complexes, and a direct comparison with two mixed (Ru/Ir) ECL systems for which emission from only the ruthenium-complex was previously reported. Concomitant emission from both luminophores was observed in all three systems, but only when: (1) the applied potentials were sufficient to generate the intermediates required to form the electronically excited state of both complexes; and (2) the concentration of the iridium complex (relative to the ruthenium complex) was sufficient to overcome quenching processes. Both enhancement and quenching of the ECL of the ruthenium complex was observed, depending on the experimental conditions. The observations were rationalised through several complementary mechanisms, including resonance energy transfer and various energetically favourable electron-transfer pathways.
Electrochemiluminescence (ECL) is a highly sensitive mode of detection utilised in commercialised bead-based immunoassays. Recently, the introduction of a freely diffusing water-soluble Ir(
iii
) ...complex was demonstrated to enhance the ECL emission of Ru(bpy)
3
2+
labels anchored to microbeads, but a comprehensive investigation of the proposed 'redox-mediated' mechanism was not carried out. In this work, we select three different water-soluble Ir(
iii
) complexes by virtue of their photophysical and electrochemical properties in comparison with those of the Ru(bpy)
3
2+
luminophore and the TPrA co-reactant. A systematic investigation of the influence of each Ir(
iii
) complex on the emission of the Ru(
ii
) labels on single beads by ECL microscopy revealed that the heterogeneous ECL can be finely tuned and either enhanced up to 107% or lowered by 75%. The variation of the Ru(bpy)
3
2+
ECL emission was correlated to the properties of each Ir(
iii
)-based mediator, which enabled us to decipher the mechanism of interaction and define guidelines for the future design of novel Ir(
iii
) complexes to further enhance the ECL emission of bead-based immunoassays. Ultimately, we showcase the potential of this technology for practical sample analysis in commercial instruments by assessing the enhancement of the collective ECL intensity from a bead-based system.
Redox mediated mechanism in electrochemiluminescence (ECL) beads-based assay: the influence of Ir(
iii
) redox mediators increases the ECL signal up to 107%.
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•Sensitive and amplification-free microRNA (miRNA) detection using a portable electrochemiluminescence biosensor.•Electrochemiluminescence sensing of miRNA with a mobile phone ...camera.•A rapid electrochemiluminescence sensor for miRNA‑21 detection combining a molecular beacon with magnetic extraction.
microRNAs (miRNAs) have emerged as important biomarkers for numerous diseases, but their widespread use has been hampered by the lack of point-of-care testing solutions. Herein, we demonstrate a sensitive, rapid and portable electrochemiluminescence (ECL) based sensor for miRNA-21 combining a switch-on ECL molecular beacon with magnetic bead based extraction of the miRNA target sequence. Streptavidin coated magnetic beads were functionalised with a hairpin molecular beacon; one stem of the beacon was functionalised with an ECL active label and the opposing stem was functionalised with a quencher. When the target miRNA was present, the hairpin opened, separating the label and quencher, generating an intense ECL signal. The sensor provides a simple and robust strategy for miRNA detection without the need for intercalating labels, reporter probes for detection, added enzymes or hairpin primers for target amplification. The detection limit of the sensor is 500 attomoles of miRNA-21 when using a photomultiplier tube for ECL detection. The potential of the developed sensor for point-of-care applications has been demonstrated by combining the molecular beacon ECL sensor with a portable potentiostat for ECL generation and a mobile phone camera for ECL detection of miRNA-21.
The classic and most widely used co-reactant electrochemiluminescence (ECL) reaction of tris(2,2′-bipyridine)ruthenium(
ii
) (Ru(bpy)
3
2+
) and tri-
n
-propylamine is enhanced by an order of ...magnitude by
fac
-Ir(sppy)
3
3−
(where sppy = 5′-sulfo-2-phenylpyridinato-
C
2
,
N
), through a novel 'redox mediator' pathway. Moreover, the concomitant green emission of Ir(sppy)
3
3−
* enables internal standardisation of the co-reactant ECL of Ru(bpy)
3
2+
. This can be applied using a digital camera as the photodetector by exploiting the ratio of R and B values of the RGB colour data, providing superior sensitivity and precision for the development of low-cost, portable ECL-based analytical devices.
A water-soluble Ir(
iii
) complex is shown to enhance the 'remote' mechanism of the most widely used co-reactant ECL reaction of tris(2,2′-bipyridine)ruthenium(
ii
) with tripropylamine.
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