Iridium(III) Complexes of Bifunctional 2-(2-Pyridyl)imidazole Ligands: Electrochemiluminescent Emitters in Aqueous Media.

A series of electrochemiluminescent (ECL) iridium(III) complexes with the general formula [Ir(CN)(pim)] (where CN = cyclometalating ligands 2-phenylpyridinato (ppy) or 2-(2,4-difluorophenyl)pyridinato (dFppy), and pim = 2-(2-pyridyl)imidazole) have been synthesized. In each case, the 2-(2-pyridyl)imidazole ancillary ligand has been modified to facilitate bioconjugation and ECL label development. All complexes exhibit blue-shifted optical and electro-generated phosphorescence relative to the archetypal complex [Ir(ppy)(bpy)] (bpy = 2,2'-bipyridine).

Double-pentagon silicon chains in a quasi-1D Si/Ag(001) surface alloy.

Silicon surface alloys and silicide nanolayers are highly important as contact materials in integrated circuit devices. Here we demonstrate that the submonolayer Si/Ag(001) surface reconstruction, reported to exhibit interesting topological properties, comprises a quasi-one-dimensional Si-Ag surface alloy based on chains of planar double-pentagon Si moieties. This geometry is determined using a combination of density functional theory calculations, scanning tunnelling microscopy, and grazing incidence x-ray diffraction simulations, and yields an electronic structure in excellent agreement with photoemission measurements.

A sulphide resistant Ag|AgCl reference electrode for long-term monitoring.

Reference electrodes which demonstrate long-term potential stability are essential for many continuous monitoring applications and are commonly based on Ag|AgCl electrodes; however, these electrodes are susceptible to poisoning from aqueous sulphide species which are commonly present in wastewater and natural groundwater. This work presents a sulphide resistant solid-state reference electrode (SSRE) based on a composite material using suspended KCl electrolyte and sacrificial AgCl in a cross-linked polyvinyl acetate polymer matrix. Sulphidation of the sacrificial AgCl produces a stable AgS precipitate and prevents further ingress of the poisoning sulphide species through the composite material.

Functionalized α-Cyanostilbene Derivatives for Detection of Hypoxia or Proteostasis Imbalance in Live Cells.

α-Cyanostilbene represents one of the easily functionalized aggregation-induced emission (AIE) scaffolds. It has been widely adopted for the construction of fluorescent materials for broad applications. Here, we further expanded the utilization of α-cyanostilbene derivatives for the detection of hypoxia or proteostasis imbalance in live cells.

On-Surface Molecular Recognition Driven by Chalcogen Bonding.

Chalcogen bonding interactions (ChBIs) have been widely employed to create ordered noncovalent assemblies in solids and liquids. Yet, their ability to engineer molecular self-assembly on surfaces has not been demonstrated. Here, we report the first demonstration of on-surface molecular recognition solely governed by ChBIs.

Elucidating the Mechanism of Efficient Eu(III) and Yb(III) Sensitisation from a Re(I) Tetrazolato Triangular Assembly.

The reaction of Re(CO)Br with deprotonated 1H-(5-(2,2':6',2''-terpyridine)pyrid-2-yl)tetrazole yields a triangular assembly formed by tricarbonyl Re(I) vertices. Photophysical measurements reveal blue-green emission with a maximum at 520 nm, 32 % quantum yield, and 2430 ns long-lived excited state decay lifetime in deaerated dichloromethane solution. Coordination of lanthanoid ions to the terpyridine units red-shifts the emission to 570 nm and also reveals efficient (90 %) and fast sensitisation of both Eu(III) and Yb(III) at room temperature, with a similar rate constant k on the order of 10 s.

An extremely electron poor Au(III) trication bearing acetonitrile ligands.

The synthesis and structural characterization of an electron poor Au(III) trication bearing 2 imidazole and 2 acetonitrile ligands is described. The new complex is capable of aryl C-H metalation with the formation of a monomesitylene complex and also demonstrated to be highly oxidizing in the rapid room temperature conversion of cyclohexene to benzene.

Aggregation-Induced Emission of Naphthalene Diimides: Effect of Chain Length on Liquid and Solid-Phase Emissive Properties.

The aggregation-induced emission (AIE) properties of a systematic series of naphthalene diimides (NDIs) varying the chain length at the imide positions have been studied. A solvophobic collapse of NDI units through the flash injection of THF NDI solutions in sonicating water triggers the formation of stable suspensions with enhanced fluorescence emissions. Shorter chains favor the π-π stacking of NDI units through H-aggregation producing a strong AIE effect showing remarkably high quantum yields that have not been observed for non core-substitued NDIs previously.

More Accurate Measurement of Return Peak Current in Cyclic Voltammetry Using Diffusional Baseline Fitting.

The difficulty associated with accurately measuring the height of the back peak () in cyclic voltammetry (CV) has long plagued electrochemists. Most commonly, is measured by extrapolating a linear fit from a selected region of a voltammogram after the switching potential (), but without substantial separation between the peak potential () and , this approach always overestimates the background current and so underestimates . Moreover, experimental conditions can present challenges for this method as an appropriate region for linear fitting is often lacking due to neighboring peaks or solvent electrolysis current.

N-Heterocyclic Olefins on a Silicon Surface.

The adsorption of N-heterocyclic olefins (NHOs) on silicon is investigated in a combined scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory study. We find that both of the studied NHOs bind covalently, with ylidic character, to the silicon adatoms of the substrate and exhibit good thermal stability. The adsorption geometry strongly depends on the N-substituents: for large N-substituents, an upright adsorption geometry is favored, while a flat-lying geometry is found for the NHO with smaller wingtips.

Giant and Tunable Out-of-Plane Spin Polarization of Topological Antimonene.

Topological insulators are bulk insulators with metallic and fully spin-polarized surface states displaying Dirac-like band dispersion. Due to spin-momentum locking, these topological surface states (TSSs) have a predominant in-plane spin polarization in the bulk fundamental gap. Here, we show by spin-resolved photoemission spectroscopy that the TSS of a topological insulator interfaced with an antimonene bilayer exhibits nearly full out-of-plane spin polarization within the substrate gap.

Structural verification and new reactivity for Stang's reagent, [PhI(CN)][OTf].

The structure of Stang's reagent [PhI(CN)][OTf] is confirmed by X-ray crystallography and is determined to be best described as an ion-pair in organic solution. It is found to be a strong Lewis acid, but reaction with pyridine ligands gives [Pyr-CN][OTf] salts oxidation of pyridine giving a new derivative of the CDAP reagent widely used as an activation agent for polysaccharides.

Longitudinal measures of labour time-use on pasture-based dairy farms, incorporating the impact of specific facilities and technologies.

The seasonal workload on pasture-based dairy farms, combined with increased herd sizes, have led to an increased focus on farm labour time-use and techniques that can reduce farm labour demand. The objective of this study was to measure labour time-use over time on a sample of pasture-based dairy farms and examine the impact that specific facilities and technologies could have on labour demand in real farm situations. Fifty-seven farms completed two labour time-use studies in spring 2019 and 2021 (1st February to 30th April).

Electrochemiluminescence Amplification in Bead-Based Assays Induced by a Freely Diffusing Iridium(III) Complex.

Heterogeneous electrochemiluminescence (ECL) assays employing tri--propylamine as a co-reactant and a tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)]) derivative as an emissive label are integral to the majority of academic and commercial applications of ECL sensing. This model system is an active research area and constitutes the basis of successfully commercialized bead-based ECL immunoassays. Herein, we propose a novel approach to the enhancement of such conventional ECL assays the incorporation of a second metal coordination complex, [Ir(sppy)] (where sppy = 5'-sulfo-2-phenylpyridinato-,), to the experimental system.

The impact of work organisation on the work life of people on pasture-based dairy farms.

The seasonal workload combined with increased dairy herd sizes and a declining workforce have created social sustainability challenges for pasture-based dairy farms. Effective work organisation can build productive capacity that may have a positive impact on this scenario. Our objective was to develop a framework to characterise and examine the effect of work organisation on the working situations of the people involved in a sample of 55 pasture-based dairy farms in Ireland.

A simple, low-cost instrument for electrochemiluminescence immunoassays based on a Raspberry Pi and screen-printed electrodes.

A powerful, yet low-cost and semi-portable electrochemiluminescence (ECL) biosensing device is described. It is constructed around a Raspberry Pi single-board computer, which serves as the controller and user interface. The Pi is interfaced with an expansion board that controls the potential applied to a disposable screen-printed electrode and facilitates data acquisition from a photomultiplier tube (PMT), which detects the ECL emission from the sensor surface.

A redox-mediator pathway for enhanced multi-colour electrochemiluminescence in aqueous solution.

The classic and most widely used co-reactant electrochemiluminescence (ECL) reaction of tris(2,2'-bipyridine)ruthenium(ii) ([Ru(bpy)]) and tri--propylamine is enhanced by an order of magnitude by -[Ir(sppy)] (where sppy = 5'-sulfo-2-phenylpyridinato- ,), through a novel 'redox mediator' pathway. Moreover, the concomitant green emission of [Ir(sppy)]* enables internal standardisation of the co-reactant ECL of [Ru(bpy)]. 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.

Construction of a Highly Sensitive Thiol-Reactive AIEgen-Peptide Conjugate for Monitoring Protein Unfolding and Aggregation in Cells.

Impairment of the protein quality control network leads to the accumulation of unfolded and aggregated proteins. Direct detection of unfolded protein accumulation in the cells may provide the possibility for early diagnosis of neurodegenerative diseases. Here a new platform based on a peptide-conjugated thiol-reactive aggregation-induced emission fluorogen (AIEgen), named MI-BTD-P (or D1), for labeling and tracking unfolded proteins in cells is reported.

Emission from the working and counter electrodes under co-reactant electrochemiluminescence conditions.

We present a new approach to explore the potential-dependent multi-colour co-reactant electrochemiluminescence (ECL) from multiple luminophores. The potentials at both the working and counter electrodes, the current between these electrodes, and the emission over cyclic voltammetric scans were simultaneously measured for the ECL reaction of Ir(ppy) and either [Ru(bpy)] or [Ir(df-ppy)(ptb)], with tri--propylamine as the co-reactant. The counter electrode potential was monitored by adding a differential electrometer module to the potentiostat.

Controlled growth of ordered monolayers of N-heterocyclic carbenes on silicon.

N-Heterocyclic carbenes (NHCs) are promising modifiers and anchors for surface functionalization and offer some advantages over thiol-based systems. Because of their strong binding affinity and high electron donation, NHCs can dramatically change the properties of the surfaces to which they are bonded. Highly ordered NHC monolayers have so far been limited to metal surfaces.

Evolution of Topological Surface States Following Sb Layer Adsorption on BiSe.

Thin antimony layers adsorbed on bismuth selenide (Bi2Se3) present an exciting topological insulator system. Much recent effort has been made to understand the synthesis and electronic properties of the heterostructure, particularly the migration of the topological surface states under adsorption. However, the intertwinement of the topological surface states of the pristine Bi2Se3 substrate with the Sb adlayer remains unclear.

Luminescent iridium(iii)-boronic acid complexes for carbohydrate sensing.

A family of four Ir(iii) complexes of the form [Ir(ppy)2(L)]Cl (where ppy = 2-phenyl-pyridine and L = a pyridyl-1,2,4-triazole or pyridyl-1,3,4-oxadiazole ligand bearing a boronic acid group) have been prepared as potential luminescent sensors for carbohydrates. A modular eight step procedure was developed to synthesise the complexes, and this was initiated with the preparation of two benzhydrazide and three S-ethylated pyridine-2-thiocarboxamides precursors. Reaction of these precursors produced three new 1,2,4-triazole- and one 1,3,4-oxadiazole-based ligands substituted with boronic acid pinacol ester groups.