Deactivation of the ruthenium excited state by enhanced homogeneous charge transport: Implications for electrochemiluminescent thin film sensors

peer-reviewedThe electrochemiluminescent (ECL) performance of three ruthenium-based metallopolymer platforms with different homogeneous charge transfer diffusion coefficients (DCT) is reported. Significantly, simultaneous detection of light and current in tandem with steady-state photoluminescence studies demonstrate that increasing the rate of Ru3 + production via enhanced charge transport results in a decrease in ECL intensity of up to 82% when the concentration of the co-reactant, sodium oxalate, is low, i.e., sub-mM. Spectroelectrochemical studies demonstrate that for maximum sensitivity to be obtained, the electroactive properties of the polymeric support matrix need to be considered in tandem with luminophore, analyte and co-reactant concentrations

Electrochemiluminescence platform for the detection of C-reactive proteins : application of recombinant antibody technology to cardiac biomarker detection

This work exploits the high-affinity of recombinant antibodies and low background electrochemiluminescence (ECL) for cardiac-biomarker detection. The developed assay is capable of fg mL-1 detection limits as well as the detection of C-Reactive Protein (CRP) over a clinically relevant range. The assay demonstrated robust reproducibility, selectivity and stability while also highlighting a novel platform for detection of cardiac biomarkers at low concentrations

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

Applications of bio-resource based sustainable heterogeneous Pd-Nanocatalyst for Cross-Coupling and Michael addition reactions

The development of efficient and cost-effective catalysts from renewable sources is crucial for sustainable chemistry. Herein, we developed a bio-heterogeneous Pd-nanocatalyst (PdNc@PA) by incorporating palladium nanoparticles into biodegradable kenaf-cellulose modified with poly(amidoxime) ligands. The catalyst has demonstrated remarkable stability and exceptional catalytic performance in a range of cross-coupling including Mizoroki-Heck, Suzuki-Miyaura, and Tamejiro-Hiyama reactions of inactivated aryl chlorides resulting in high yields of the desired coupling products. Additionally, PdNc@PA was also found to be effective in Michael addition reactions producing N, S, O-alkylated products in high yields. Furthermore, the PdNc@PA catalyst demonstrated robustness and recoverability allowing it to be reused across successive cycles without significant loss of catalytic activity. The incorporation of renewable resources in catalyst development offers an environmentally conscious alternative to traditional synthetic approaches. This research highlights the potential of utilizing biodegradable materials as catalyst supports, which could significantly diminish environmental impact and waste production. Moreover, this study demonstrates the versatility of PdNc@PA as a proficient and reusable catalyst for a diverse array of organic reactions. These discoveries provide an encouraging pathway towards the development of sustainable and economically viable catalysts suitable for industrial applications

Ground and excited state communication within a ruthenium containing benzimidazole metallopolymer

Emission spectroscopy and electrochemistry has been used to probe the electronic communication between adjacent metal centres and the conjugated backbone within a family of imidazole based metallopolymer, [Ru(bpy)2(PPyBBIM)n]2+, in the ground and excited states, bpy is 2,2’-bipyridyl, PPyBBIM is poly[2-(2-pyridyl)-bibenzimidazole] and n = 3, 10 or 20. Electronic communication in the excited state is not efficient and upon optical excitation dual emission is observed, i.e., both the polymer backbone and the metal centres emit. Coupling the ruthenium moiety to the imidazole backbone results in a red shift of approximately 50 nm in the emission spectrum. Luminescent lifetimes of up to 120 ns were also recorded. Cyclic voltammetry was also utilized to illustrate the distance dependence of the electron hopping rates between adjacent metal centres with ground state communication reduced by up to an order of magnitude compared to previously reported results when the metal to backbone ratio was not altered. DCT and De values of up to 3.96 x 10-10 and 5.32 x 10-10 cm2S-1 were observed with corresponding conductivity values of up to 2.34 x 10-8 Scm-1

Toxic Metal Ions Removal from Electroplating Wastewater Using Polymer Chelating

Background: Empty fruit bunch (EFB) is a type of biomass waste product formed during the production process of palm oil. In the present work, EFB was used to prepare a cellulose-graftcopolymer which can be converted into poly(amidoxime)-poly(hydroxamic acid) ligands suitable for the removal of heavy metals from electroplating wastewater. Methods and Results: Poly(amidoxime)-poly(hydroxamic acid) ligands were synthesized from the poly(acrylonitrile-co-methyl acrylate) grafted palm cellulose and were analyzed via FT-IR and FESEM. The binding capacity (qe) with the metals ions such as copper (Cu2+), iron (Fe3+), cobalt (Co2+), nickel (Ni2+) and lead (Pb2+) were 341, 290, 284, 204 and 482 mg g-1, respectively at pH 6. The pseudo-first-order kinetic model is fitted with the results confirming heavy metal adsorption. The isotherm study was conducted using a linear plot of the Langmuir isotherm where results were significantly different from the experimental value (maximum adsorption, qe), indicating that adsorption does not occur on a single layer. However, the coefficient of the correlation values obtained using the Freundlich isotherm model were acceptable (R2>0.99), and it was concluded that adsorption was multilayered with some metal ions. Conclusion: The polymeric ligands synthesized here showed excellent adsorption of heavy metals from electroplating wastewater containing a notable amount of copper and iron metal ions

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Rapid microwave assisted synthesis and characterisation of a semiconducting polymer with pKa tuneable degradation properties

As part of ongoing efforts to develop electroactive polymers (EAPs) which are biodegradable/bioresorbable, we report on the microwave assisted synthesis and characterization of an electrically conducting and electroactive polymer that capitalises on pKa sensitivity to initiate the system’s fracture and breakdown. The system, poly(bis((thiophen-2-yl) methylene) benzene-1,4-diamine), a poly(thiophene-azomethine) co-polymer (PAZO), incorporates hydrolytically sensitive azomethine linkers amongst bithiophene units resulting in one continuously conjugated and redox-active macromolecular framework. Rapid microwave assisted synthesis allowed for facile preparation of the polymer with significantly reduced reaction times when compared to traditional synthetic routes. Electrochemical analysis indicated quasi-reversible electrochemical behaviour with sufficiently high conductivity for in vivo biomedical applications. The polymer displays tunable degradation behaviour whereby the time duration required for polymeric breakdown is a function of the pKa of the acid used to catalyse the reaction resulting in controllable degradation times ranging from 1 h to 6 months. The development of conductive polymeric materials that are fully degradable over pre-defined time periods opens up a portal to the next generation of EAPs for in vivo biomedical applications

Electrochemiluminescent monolayers on metal oxide electrodes: detection of amino acids

The electrochemical and photochemical properties of [Ru(bPY)(2)dcb]Cl-2 monolayers and their subsequent use for the detection of amino acids, e.g., proline, is reported; dcb is 4,4'-dicarboxy-2,2'-bipyridine and bpy is 2,2'-bipyridine. The ability of such a complex to form stable monolayers enables its utilization for the detection of oxalate and several amino acids, producing significant ECL. The electrochemical response of the Ru2+/3+ couple is electrochemically reversible and the monolayers show excellent stability with the response decreasing by less than 8% after continuous scanning over 4 h. The ECL and current responses increase linearly with increasing analyte concentration 0.2 <=, [Proline] <= 1 nM while for hydroxy-proline the dynamic range is from 1 to 10 nM. The ECL signal was monitored at similar to 644 nm, representing the lambda(max) for the [Ru(bPY)2dcb]Cl-2 monolayers. This wavelength is shifted by approximately 28 nm compared to the photoexcited lambda(max) for the same system. This technique is simple, rapid, selective and sensitive, and shows potential for the high-throughput quantitation of amino acids if adapted with other techniques such as FIA or LC systems. (c) 2006 Elsevier B.V. All rights reserved