Electrochemiluminescence (ECL) sensing properties of water soluble core-shell CdSe/ZnS quantum dots/Nafion composite films

Water soluble positively charged 2-(dimethylamino) ethanethiol (DAET)-protected core-shell CdSe/ZnS quantum dots (QDs) were synthesized and incorporated within negatively charged Nafion polymer films. The water soluble QDs were characterized using UV-visible and fluorescence spectroscopies. Nafion/QDs composite films were deposited on glassy carbon electrodes and characterized using cyclic voltammetry. The electrochemiluminescence (ECL) using hydrogen peroxide as co-reactant was enhanced for Nafion/QDs composite films compared to films of the bare QDs. Significantly, no ECL was observed for Nafion/QDs composite films when peroxydisulfate was used as the co-reactant, suggesting that the permselective properties of the Nafion effectively exclude the co-reactant. The ECL quenching by glutathione depends linearly on its concentration when hydrogen peroxide is used as the co-reactant, opening up the possibility to use Nafion/QDs composite films for various electroanalytical applications

Optimising electrogenerated chemiluminescence of quantum dots via co-reactant selection

We demonstrate that for quantum dot (QD) based electrochemiluminescence (ECL), the commonly used co-reactant does not preform as effectively as potassium persulfate. By exploiting this small change is co-reactant, ECL intensity can be enhanced dramatically in a cathodic based ECL system. However, TPA remains the preferential co-reactant based system for anodic ECL. This phenomenon can be rationalised through the relative energy level profiles of the QD to the co-reactant in conjunction with the applied potential range. This work highlights the importance of understanding the co-reactant pathway for optimising the application of ECL to bioanalytical analysis, in particular for near infrared (NIR) QDs which can be utilised for analysis in blood

Methods for synthesizing diethyl carbonate from ethanol and supercritical carbon dioxide by one-pot or two-step reactions in the presence of potassium carbonate

Carbon dioxide sequestration was studied by synthesizing diethyl carbonate (DEC) from ethanol and CO2 under supercritical conditions in the presence of potassium carbonate as a base. The co-reagent was ethyl iodide or a concentrated strong acid. This sequestration reaction occurs in two steps, which were studied separately and in a one-pot reaction. An organic-inorganic carbonate hybrid, potassium ethyl carbonate (PEC) is generated at the end of the first step. This intermediate was characterized and was found to be a target molecule for CO2 capture. Different co-reactants, such as ethyl iodide and concentrated strong Brönsted acid, were compared in the second step and used to investigate the reactivity of the hybrid. With ethyl iodide as the co-reactant, one-pot DEC synthesis gave higher yields (46%) than two-step production. The supercritical CO2 acts as a swelling solvent and compatibilizing agent in the reaction medium, favoring interactions between ethanol and CO2 and between PEC and ethyl iodide. The use of a phase transfer catalyst (PTC) increased DEC production (yield 51%) without increasing the amount of diethyl ether (DEE) produced as a by-product (yield 2%)

Insights into electrochemiluminescent enhancement through electrode surface modification

The electrochemiluminescent (ECL) properties of a luminescent metal centre, [Ru(bpy)(3)](2+), can be significantly modulated through its electronic interaction with neighbouring centres and the polymer backbone used to confine it on an electrode surface. From the perspective of ECL based sensing devices, an increase in the ECL efficiency of a metallopolymer film can result in enhanced sensor sensitivity and selectivity. This work probes the ECL properties of both conjugated, [Ru(bpy)(2)(PPyBBIM)(10)](2+), and non-conjugated, [Ru(bpy)(2)(PVP)(10)](2+), ruthenium based metallopolymer films based on a well documented reaction with sodium oxalate, where bpy is 2,2'-bipyridyl, PPYBBIM is poly[2-(2-pyridyl)-bibenzimidazole] and PVP is poly(4-vinylpyridine). Through a combination of ground state electrochemical studies and ECL measurements, the ECL efficiency for each film is determined. This study reveals that despite a dramatic influence in charge transfer rates between metal centres, as observed for the conducting polymer, mediated through the conducting polymer backbone, a corresponding increase in ECL efficiency is not always observed. The degree of communication between the adjacent excited state metal centres are an important consideration for ECL enhancement however self quenching, luminophore distribution and film porosity must also be considered

A novel route to Pt-Bi2O3 composite thin films and their application in photo-reduction of water

A novel homoleptic bismuth(III) β-diketonate (dibenzoylmethane – dbm) complex [Bi(dbm)3]2 has been used as a precursor to thin films of crystalline β-Bi2O3, and hexachloroplatinic acid (H2PtCl6·6H2O) has been demonstrated as a suitable precursor for deposition of platinum nanoparticles, both deposited via aerosol-assisted chemical vapour deposition (AACVD). Thin films of Pt–Bi2O3 were co-deposited from a mixture of [Bi(dbm)3]2 and H2PtCl6·6H2O; the introduction of Pt particles into β-Bi2O3 causes hydrogen to be evolved during photolysis of water over the composite material, a property not found for Pt particles or β-Bi2O3 alone

Enhanced electrochemiluminescence from a stoichiometric ruthenium(II)-iridium(III) complex soft salt

The authors thank NSERC, CFI, FQRNT, PREA, and The University of Western Ontario for generous financial support to this research.Electrochemiluminescence (ECL) and electrochemistry are reported for a heterometallic soft salt, [Ru(dtbubpy)3][Ir(ppy)2(CN)2]2 ([Ir][Ru][Ir]), consisting of a 2:1 ratio of complementary charged Ru and Ir complexes possessing two different emission colors. The [Ru]2+ and [Ir]− moieties in the [Ir][Ru][Ir] greatly reduce the energy required to produce ECL. Though ECL intensity in the annihilation path was enhanced 18× relative to that of [Ru(bpy)3]2+, ECL in the co-reactant path with tri-n-propylamine was enhanced a further 4×. Spooling spectroscopy gives insight into ECL mechanisms: the unique light emission at 634 nm is due to the [Ru]2+* excited state and no [Ir]−* was generated in either route. Overall, the soft salt system is anticipated to be attractive and suitable for the development of efficient and low-energy-cost ECL detection systems.PostprintPeer reviewe

Constraints on Exotic Heavily Ionizing Particles from the Geological Abundance of Fullerenes

The C_{60} molecule exhibits a remarkable stability and inertness that leads to its survival in ancient carbonaceous rocks initially subject to the high temperatures requisite for its formation. Elementary particles having very high electronic stopping powers can similarly form C_{60} and higher fullerenes in their wake. Combined, these two features point at the possibility of using the C_{60} presence (or absence) in selected bulk geological samples as a new type of solid-state nuclear track detector, with applications in astro-particle physics.Comment: Final version (few modifications). Phys. Rev. Lett. (in press). 4 pages LaTeX, 1 eps figure embedde

Chemiluminescence from osmium(ii) complexes with phenanthroline, diphosphine and diarsine ligands

The reaction of various [Os(L)2(L′)]2+ complexes (where L and L′ are phenanthroline, diphosphine or diarsine ligands) and organic reducing agents after chemical or electrochemical oxidation of the reactants produces an emission of light corresponding to MLCT transitions. In certain instances, the emission was greater than that of [Ru(bipy)3]2+, but the relative signals were dependent on many factors, including reagent concentration, mode of oxidation, reducing agent and the sensitivity of the photodetector over the wavelength range

Green chemiluminescence from a bis-cyclometalated iridium(III) complex with an ancillary bathophenanthroline disulfonate ligand

The reaction of a fluorinated iridium complex with cerium(IV) and organic reducing agents generates an intense emission with a significant hypsochromic shift compared to contemporary chemically-initiated luminescence from metal complexes