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1.
Chem Commun (Camb) ; 56(8): 1263-1266, 2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-31903465

RESUMO

Two methods are reported for the one-pot preparation of high concentrations of gold nanoparticles (AuNPs) embedded throughout sodium polyacrylate hydrogels; this stabilises the AuNP in even extremely high ionic strength environments, and enables them to act as effective catalysts for the hydride-reduction of nitrophenols and of dyes, with zero order kinetics.

2.
Dalton Trans ; 48(18): 5892-5896, 2019 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-30632590

RESUMO

Copper(ii) coordination complexes, 1 and 2, containing nonsteroidal anti-inflammatory drugs (NSAIDs) potently kill breast cancer stem cells (CSCs) and bulk breast cancer cells. Although detailed biological studies have been conducted to shed light on their mechanism of cytotoxicity, little is known about their molecular level mechanism of action. This biophysical study, aided by the preparation of a fluorophore-containing analogue, 3, reveals that the complexes operate by undergoing reduction to a copper(i) form and releasing the associated NSAIDs.


Assuntos
Antineoplásicos/química , Fenômenos Biofísicos/efeitos dos fármacos , Complexos de Coordenação/química , Cobre/química , Células-Tronco Neoplásicas/efeitos dos fármacos , Antineoplásicos/farmacologia , Neoplasias da Mama/diagnóstico por imagem , Neoplasias da Mama/tratamento farmacológico , Sobrevivência Celular/efeitos dos fármacos , Complexos de Coordenação/farmacologia , Feminino , Corantes Fluorescentes/química , Humanos , Indometacina/química , Naproxeno/química , Imagem Óptica/métodos , Oxirredução , Espécies Reativas de Oxigênio/metabolismo
3.
Anal Chim Acta ; 1048: 12-21, 2019 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-30598141

RESUMO

In amperometric gas sensors, the flux of gas to electrode surfaces determines the analytical response and detection limit. For trace concentration detection, the resulting low current prevents the miniaturisation of such sensors. Therefore, in this study, we have developed repeating arrays of nanostructures which maximise flux towards their surface. Unique platinum 3D cauliflower-shaped deposits with individual floret-shaped segments have been produced in a single step electrodeposition process. The confined walls of recessed microelectrode arrays (10 µm in diameter, 90 electrodes) are utilized to produce these structures with a high surface area. Distinct segments are observed, with the gaps corresponding to electrodes adjacent in the microarray; thus the majority of the deposits face the primary diffusion zones. The sizes and shapes of the deposits are characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) and the largest structures are found to be 22 ±â€¯1 µm in width and 7.9 ±â€¯0.2 µm in height over the microhole. These modified electrodes are employed to detect ammonia using the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C2mim][NTf2], as an electrolyte. Current responses on the cauliflower arrays were seven times higher for linear sweep voltammetry and ca. 12 times higher for chronoamperometry, relative to the bare microrrays, and limits of detection were less than 1 part per million of ammonia (gas phase concentration). This work highlights the use of modified microarrays with highly accessible 3D structures for enhanced electroanalytical detection of analyte species at ultra low concentrations.

4.
Phys Chem Chem Phys ; 20(24): 16558-16567, 2018 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-29873357

RESUMO

Solvate ionic liquids are a relatively new class of liquids produced by combining a coordinating solvent with a salt. They have a variety of uses and their suitability for such depends upon the ratio of salt to coordinating solvent. This work investigates the Kamlet-Taft solvent parameters of, NMR chemical shifts of nuclei in, and thermoelectrochemistry of a selected set of solvate ionic liquids produced from glymes (methyl terminated oligomers of ethylene glycol) and lithium bis(trifluoromethylsulfonyl)imide at two different compositions. The aim is to improve the understanding of the interactions occurring in these ionic liquids to help select suitable solvate ionic liquids for future applications.

5.
Chem Commun (Camb) ; 54(42): 5261-5267, 2018 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-29761191

RESUMO

For the third time, a Faraday Discussion addressed ionic liquids. Encompassing the wealth of research in this field, the contributions ranged from fundamental insights to the diverse applications of ionic liquids. Lively discussions initiated in the lecture hall and during poster sessions then seamlessly continued during the social program.

10.
Phys Chem Chem Phys ; 19(35): 24255-24263, 2017 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-28848948

RESUMO

Entropic changes inherent within a redox process typically result in significant temperature sensitivity. This can be utilised positively or can be a detrimental process. This study has investigated the thermoelectrochemical properties (temperature-dependant electrochemistry) of the ferrocenium|ferrocene redox couple in an ionic liquid, and in particular the effect of covalently tethering this redox couple to fixed positive or negative charges. As such, the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide was employed to dissolve ferrocene, as well as cationic-tethered ferrocene (the 1-ethyl-3-(methylferrocenyl)imidazolium cation) and anionic-tethered ferrocene (the ferrocenylsulfonyl(trifluoromethylsulfonyl)imide anion). These systems were characterised in terms of their voltammetry (apparent formal potentials, diffusion coefficients and electron transfer rate constants) and thermoelectrochemistry (temperature coefficients of the cell potential or 'Seebeck coefficients', short circuit current densities and power density outputs). The oxidised cationic species behaved like a dicationic species and was thus 6-fold more effective at converting waste thermal energy to electrical power within a thermoelectrochemical cell than unmodified ferrocene. This was almost exclusively due to a significant boost in the Seebeck coefficient of this redox couple. Conversely, the oxidised anionic species was formally a zwitterion, but this zwitterionic species behaved thermodynamically like a neutral species. The inverted entropic change upon going from ferrocene to anion-tethered ferrocene allowed development of a largely temperature-insensitive reference potential based upon a mixture of acetylferrocene and ferricenyl(iii)sulfonyl(trifluoromethylsulfonyl)imide.

11.
Org Biomol Chem ; 15(26): 5556-5563, 2017 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-28639642

RESUMO

The cleavage of a series of ethers was examined in an ionic liquid containing hydrogen bromide. Reactions that did not proceed in either water or DMSO were found to proceed readily in this system, with notable selectivity between the cleavage of the different ether types examined herein. Increasing the proportion of water in the reaction mixture dramatically decreased the rate constant of ether cleavage; this could, in part, be attributed to a decrease in the solvent stabilisation of the transition state. Through analysis of the electronic requirements of the reaction (using substrates containing substituents with different Hammett parameters) and observation of rate enhancements for an ortho substituted system, the importance of the extent of protonation of the ether prior to nucleophilic attack was demonstrated.

12.
Phys Chem Chem Phys ; 18(30): 20768-77, 2016 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-27412130

RESUMO

Thermoelectrochemistry offers a simple, scalable technique for direct conversion of waste heat into useful electricity. Here the thermoelectrochemical properties of lithium-glyme solvate ionic liquids, as well as their dilute electrolyte analogues, have been investigated using mixtures of tetraglyme (G4, tetraethylene glycol dimethyl ether) and lithium bis(trifluoromethylsulfonyl)imide (Li[NTf2]). The thermoelectrochemical process is entropically-driven by release of the glyme from the lithium-glyme complex cation, due to electrodeposition of lithium metal at the hotter lithium electrode with concomitant electrodissolution at the cooler lithium electrode. The optimum ratio for thermochemical electricity generation is not the solvate ionic liquid (equimolar mixture of Li[NTf2] and glyme), but rather one Li[NTf2] to four G4, due to the mixtures relatively high ionic conductivity and good apparent Seebeck coefficient (+1.4 mV K(-1)). Determination of the lithium-glyme mixture thermal conductivity enabled full assessment of the Figure of Merit (ZT), and the efficiency relative to the Carnot efficiency to be determined. As the lithium electrodeposits are porous, alternating the temperature gradient results in a system that actually improves with repeated use.

13.
Sci Rep ; 5: 8398, 2015 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-25669133

RESUMO

Bacterial resistance to conventional antibiotics necessitates the identification of novel leads for infection control. Interference with extracellular phenomena, such as quorum sensing, extracellular DNA integrity and redox active metabolite release, represents a new frontier to control human pathogens such as Pseudomonas aeruginosa and hence reduce mortality. Here we reveal that the extracellular redox active virulence factor pyocyanin produced by P. aeruginosa binds directly to the deoxyribose-phosphate backbone of DNA and intercalates with DNA nitrogenous base pair regions. Binding results in local perturbations of the DNA double helix structure and enhanced electron transfer along the nucleic acid polymer. Pyocyanin binding to DNA also increases DNA solution viscosity. In contrast, antioxidants interacting with DNA and pyocyanin decrease DNA solution viscosity. Biofilms deficient in pyocyanin production and biofilms lacking extracellular DNA show similar architecture indicating the interaction is important in P. aeruginosa biofilm formation.


Assuntos
Biofilmes , DNA/metabolismo , Fenazinas/metabolismo , Pseudomonas aeruginosa/fisiologia , Piocianina/metabolismo , Fatores de Virulência/metabolismo , Antioxidantes/metabolismo , DNA/química , Desoxirribonuclease I/metabolismo , Transporte de Elétrons , Espaço Extracelular/metabolismo , Oxirredução , Ligação Proteica , Pseudomonas aeruginosa/patogenicidade , Piocianina/química , Termodinâmica , Viscosidade
14.
J Colloid Interface Sci ; 383(1): 110-7, 2012 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-22789798

RESUMO

Herein, we report the synthesis of three covalently linked superparamagnetic nanocrystal-multi-walled carbon nanotube (MWCNT) composites. A generic strategy for amphiphilic polymer coating of nanocrystals and further functionalization for amide bond formation with the MWCNTs is discussed. This approach can in principle allow attachment of any colloidal nanocrystal to the MWCNTs. The materials were characterized at each stage of the syntheses using DLS, zeta-potential measurements, FT-IR, TEM, and XPS techniques. The practicality of this linkage is demonstrated by the reversible magnetic immobilization of these materials on an electrode during non-aqueous electrochemistry.

15.
Chem Commun (Camb) ; 48(45): 5572-4, 2012 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-22531576

RESUMO

The Hydrogen evolution reaction has been quantitatively investigated at a Pt electrode in series of room temperature ionic liquids vs. Ag/Ag(+) redox couple. The measured formal potentials of the H(2)/H(+) (HNTf(2)) redox couple in each RTIL reveals a dependence on the nature of anion, suggesting significant interaction between proton and anion.

16.
Analyst ; 137(9): 2054-62, 2012 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-22421892

RESUMO

Carbon black (CB) nanoparticles modified with fluorescein, a highly fluorescent molecule, were prepared using a facile and efficient methodology. Simply stirring CB in aqueous solution containing fluorescein resulted in the strong physisorption of fluorescein onto the CB surface. The resulting Fluorescein/CB was then characterised by means of X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), fluorescence microscopy and fluorescence spectroscopy. The optimum experimental conditions for fluorescence of Fluorescein/CB viz. fluorescence excitation and emission wavelengths, O(2) removal and the amount of Fluorescein/CB used, were investigated. The Fluorescein/CB was used as a fluorescent probe for the sensitive detection of Pd(II) in water, based on fluorescence quenching. The results demonstrated that the fluorescence intensity of Fluorescein/CB decreased with increasing Pd(II) concentration, and the fluorescence quenching process could be described by the Stern-Volmer equation. The limit of detection (LOD) for the fluorescence quenching of Fluorescein/CB by Pd(II) in aqueous solution was found to be 1.07 µM (based on 3σ). Last, approaches were studied for the removal of Fe(III) which interferes with the fluorescence quenching of Fluorescein/CB. Complexation of Fe(III) with salicylic acid was used to enhance and control the selectivity of Fluorescein/CB sensor towards Pd(II) in the presence of Fe(III).

17.
Phys Chem Chem Phys ; 14(15): 5222-8, 2012 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-22358388

RESUMO

The kinetics and mechanism of the proton reduction reaction in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(2)mim][NTf(2)]) was studied at gold, molybdenum, nickel, titanium and platinum electrodes. Significant differences in electrochemical rate constants were observed between the different metals and with the corresponding processes in aqueous solution. The hydrogen evolution mechanism was consistent at all five metals in the ionic liquid, in stark contrast to the known behaviour in aqueous systems.

18.
Phys Chem Chem Phys ; 14(7): 2375-80, 2012 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-22246053

RESUMO

The voltammetric response of the quinone species 'quinizarin' (QZ) and its electrocatalytic reduction of oxygen are studied at a boron doped diamond electrode (BDD). It is demonstrated that, contrary to the widespread belief that adsorption of organic molecules on BDD is minimal, not only does QZ readily adsorb to the electrodes surface but this adsorption is also influenced at low surface coverages by the pre-exposure of the electrode to organic solvents. Furthermore, the nature of this adsorbed QZ species is investigated and a potential dependent phase transition is observed. This is to the authors knowledge the first system to exhibit a phase transition of an adsorbed species on a boron doped diamond surface. At low scan rates the system is found to oscillate; these oscillations are ascribed to the presence of a 'negative differential resistance'.

19.
Proc Natl Acad Sci U S A ; 108(50): 19891-5, 2011 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-22109547

RESUMO

After 35 years the hunt for improved anthracycline antibiotics is unabated but has yet to achieve the levels of clinical success desired. Electrochemical techniques provide a large amount of kinetic and thermodynamic information, but the use of such procedures is hindered by issues of sensitivity and selectivity. This work demonstrates how by harnessing the mechanism of catalytic reduction of oxygen by the quinone functionality present within the anthracycline structure it is possible to study the reactive moiety in nanomolar concentration. This methodology allows electrochemical investigation of the intercalation of quinizarin into DNA and, in particular, the quinone oxidation and degradation mechanism. The reversible reduction of the quinizarin, which in the presence of oxygen leads to the formation of reactive oxygen species, is found to occur at -0.535 V (vs. SCE) pH 6.84 and the irreversible oxidation leading to the molecules degradation occurs at +0.386 V (vs. SCE) pH 6.84.


Assuntos
Antraquinonas/química , Eletroquímica/métodos , Oxigênio/química , Animais , DNA/análise , Doxorrubicina/química , Eletricidade , Oxirredução
20.
J Phys Chem B ; 115(47): 13873-9, 2011 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-21992687

RESUMO

The electrochemistry of elemental sulfur (S(8)) and the polysulfides Na(2)S(4) and Na(2)S(6) has been studied for the first time in nonchloroaluminate ionic liquids. The cyclic voltammetry of S(8) in the ionic liquids is different to the behavior reported in some organic solvents, with two reductions and one oxidation peak observed. Supported by in situ UV-vis spectro-electrochemical experiments, the main reduction products of S(8) in [C(4)mim][DCA] ([C(4)mim] = 1-butyl-3-methylimidazolium; DCA = dicyanamide) have been identified as S(6)(2-) and S(4)(2-), and plausible pathways for the formation of these species are proposed. Dissociation and/or disproportionation of the polyanions S(6)(2-) and S(4)(2-) appears to be slow in the ionic liquid, with only small amounts of the blue radical species S(3)(•-) formed in the solutions at r.t., in contrast with that observed in most molecular solvents.

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