Molecular linkage of plasmonic nanoparticles in colloidal suspensions for enhanced pollutant sensing,

Meeting of Nanoscience and Nanotechnology (N&N) in Spain, Madrid, March 11-14 (2014) ; http://www.nanospainconf.org/2014/index.php?conf=14Spanish Ministerio de Economía y Competitividad (MINECO, Grant FIS2010-15405) and Comunidad de Madrid through the MICROSERES II network (Grant S2009/TIC-1476)Peer Reviewe

Radical in the Peroxide-Produced F-Type Ferryl Form of Bovine Cytochrome <i>c</i> Oxidase

The reduction of O2 in respiratory cytochrome c oxidases (CcO) is associated with the generation of the transmembrane proton gradient by two mechanisms. In one of them, the proton pumping, two different types of the ferryl intermediates of the catalytic heme a3-CuB center P and F forms, participate. Equivalent ferryl states can be also formed by the reaction of the oxidized CcO (O) with H2O2. Interestingly, in acidic solutions a single molecule of H2O2 can generate from the O an additional F-type ferryl form (F•) that should contain, in contrast to the catalytic F intermediate, a free radical at the heme a3-CuB center. In this work, the formation and the endogenous decay of both the ferryl iron of heme a3 and the radical in F• intermediate were examined by the combination of four experimental approaches, isothermal titration calorimetry, electron paramagnetic resonance, and electronic absorption spectroscopy together with the reduction of this form by the defined number of electrons. The results are consistent with the generation of radicals in F• form. However, the radical at the catalytic center is more rapidly quenched than the accompanying ferryl state of heme a3, very likely by the intrinsic oxidation of the enzyme itself

Temperature and oxygen-concentration dependence of singlet oxygen production by RuPhen as induced by quasi-continuous excitation

Advanced Search Home > Journals > Photochemical & Photobi... > Temperature and oxygen-... For Authors & Referees | For Librarians | For Members Journal cover: Photochemical & Photobiological Sciences Photochemical & Photobiological Sciences Issue 12, 2014 A society-owned journal publishing high quality research on all aspects of photochemistry and photobiology. Impact Factor 2.939 12 Issues per Year Indexed in Medline Journal Home Previous Article | Next Article Paper Temperature and oxygen-concentration dependence of singlet oxygen production by RuPhen as induced by quasi-continuous excitation Jaroslav Varchola,a Veronika Huntosova,b Daniel Jancura,ab Georges Wagnières,c Pavol Miskovskyab and Gregor Bánó*ab Show Affiliations Photochem. Photobiol. Sci., 2014,13, 1781-1787 DOI: 10.1039/C4PP00202D Received 06 Jun 2014, Accepted 02 Oct 2014 First published online 06 Oct 2014 | | Share on citeulike | Share on facebook | Share on twitter | | More PDF Rich HTML Send PDF to Kindle Download Citation Help Request Permissions Abstract Cited by Related Content Assessment of partial pressure of oxygen (pO2) by luminescence lifetime measurements of ruthenium coordination complexes has been studied intensively during the last few decades. RuPhen (dichlorotris(1,10-phenanthroline) ruthenium(II) hydrate) is a water soluble molecule that has been tested previously for in vivo pO2 detection. In this work we intended to shed light on the production of singlet oxygen by RuPhen. The quantum yield of singlet oxygen production by RuPhen dissolved in 0.9% aqueous NaCl solution (pH = 6) was measured at physiological temperatures (285–310 K) and various concentrations of molecular oxygen. In order to minimize the bleaching of RuPhen, the samples were excited with low power (<2 mW) laser pulses (20 μs long), created by pulsing a cw laser beam with an acousto-optical modulator. We show that, whereas the RuPhen phosphorescence lifetime decreases rapidly with an increase of temperature (keeping the oxygenation level constant), the quantum yield of singlet oxygen production by RuPhen is almost identical in the temperature range of 285–310 K. For air-saturated conditions at 310 K the measured quantum yield is about 0.25. The depopulation rate constants of the RuPhen 3MLCT (metal-to-ligand charge-transfer) state are determined in the absence and in the presence of oxygen. We determined that the excitation energy for the RuPhen 3MLCT→d–d transition is 49 kJ mol−1 in the 0.9% NaCl solution (pH = 6)

Gaps induced by molecular linkage of plasmonic nanoparticles in colloidal suspensions for SERS enhanced pesticide sensing

Espectroscopia, Universidad de la Rioja, Logroño, La Rioja, 9-11 de julio de 2014; http://www.unirioja.es/espectroscopia2014/Linear ¿,¿-dithiols with aliphatic nature have been used in this work as linkers to control the aggregation of silver nanoparticles and to induce the formation of interparticle gaps. The interest of these gaps resides in the well-known fact that when plasmonic surfaces are within a close distance, their plasmon modes couple. This event affects the electromagnetic field distribution in a manner that a drastic enhancement occurs in the gaps leading to the creation of hot spots. As a result, the optical response of substances situated inside the hot spots is strongly increased, which is highly valuable for their use in surface-enhanced spectroscopies. In this work we present a study of the formation and the characterization of the gaps formed by using dithiols of different lengths, where both thiol groups are connected by a linear aliphatic chain with 6, 8 and 10 CH2 groups. This characterization was done by using plasmon resonance and transmission electron microscopy (TEM). The Surface-Enhanced Raman Scattering (SERS) technique was employed in the investigation of the adsorption of these dithiols on the metal surface by analysing key structural spectral markers of the adsorption, metal coordination, orientation, ordering and interfacial packing of these molecules on surfaces of silver and gold NPs. The fingerprint character of SERS spectra, the propension rules of SERS and the high sensitivity of this technique make this study possible even at the very low concentration of dithiols sufficient to induce the NPs linking. Dithiol-linked nanoparticles were employed as sensors in the detection of the pesticides aldrin, dieldrin, endosulfan and linden at very low concentrations, taking advantage of the high affinity of these pollutants for aliphatic-like membranes. The sensing ability of these substrates was optimized by varying the surface coverage of dithiols.Peer Reviewe

Negligible interaction of [Ru(Phen) 3 ] 2+ with human serum albumin makes it promising for a reliable in vivo assessment of the tissue oxygenation

The interaction between a ruthenium - based water soluble oxygen probe ([Ru(Phen)3]2+, phen - phenanthroline) and human serum albumin (HSA) was investigated with the aim of describing the influence of HSA on the [Ru(Phen)3]2+ luminescence properties. Nowadays, several oxygen sensitive luminescent probes are used to determine the oxygen level in different compartments of living organisms. However, they can interact, depending on their hydrophilic/hydrophobic characters, with various serum proteins, and/or lipids, during their utilization for in vivo oxygen measurement. Since HSA is the most abundant serum protein in most biological organisms, its presence may affect the spectral properties of the employed probes and, consequently, the determination of the oxygen concentration. Having this in mind, we have applied several spectroscopic and calorimetric techniques to study [Ru(Phen)3]2+ - HSA mixtures. Only a negligible effect of HSA on the absorption and luminescence spectra of [Ru(Phen)3]2+ was observed. In addition, differential scanning calorimetric studies showed that [Ru(Phen)3]2+ does not significantly influence HSA thermal stability. Importantly, [Ru(Phen)3]2+ retained a reliable luminescence lifetime sensitivity to the oxygen concentration in solutions supplemented with HSA and in U87 MG cancer cells. Finally, the biodistribution of [Ru(Phen)3]2+ in the presence of serum proteins in the blood stream of chick embryo's chorioallantoic membrane (CAM) was investigated. Fast [Ru(Phen)3]2+ and similar extravasations were observed in the presence or absence of CAM-serum. We can conclude that HSA-[Ru(Phen)3]2+ complex interaction does not significantly influence the potential of [Ru(Phen)3]2+ to be a suitable candidate for a reliable oxygen probe in living organisms

Adsorption of linear aliphatic α,ω-dithiols on plasmonic metal nanoparticles: A structural study based on surface-enhanced Raman spectra

The adsorption mechanism of linear aliphatic α,ω-dithiols with chain lengths of 6, 8 and 10 carbon atoms on silver and gold nanoparticles has been studied by surface-enhanced Raman scattering (SERS) spectroscopy. SERS spectra provided the structural marker bands of these compounds and they were employed to obtain information about the adsorption and coordination mechanism, the orientation, conformational order, and packing of the aliphatic chains of dithiols on the metal nanoparticle surface. The effect of the type of metal (silver or gold) and the extent of surface coverage on all the above mentioned properties is discussed. It was found that the adsorption of dithiols on Au nanoparticles leads to a more disordered structure of the aliphatic chains of dithiols in comparison with the adsorption on Ag nanoparticles. The interaction through both thiol groups makes the adsorption of dithiols on metal surfaces substantially different from that of monothiols; in particular, the orientation of dithiols is perpendicular, while monothiols adopt a tilted orientation. Dithiols may act as linkers between metal nanoparticles and induce the formation of nanogaps with a controllable interparticle distance. The nanogaps thus formed are able to produce hot spots exhibiting a large intensification of electromagnetic field in these points which has been proved by the observation of intense SERS spectra of dithiols until a concentration of 10-8 M, corresponding to a large Raman enhancement factor of 5 × 106. © 2014 the Partner Organisations.This work has been supported by the Spanish Ministerio de Economía y Competitividad (MINECO, grant FIS2010-15405) and Comunidad de Madrid through the MICROSERES II network (grant S2009/TIC-1476), by the Agency of the Ministry of Education of Slovak Republic for the Structural Funds of the European Union, Operational program Education (Doctorand, ITMS code: 26110230013 and KVARK, ITMS code: 26110230084) and Operational program Research and Development (NanoBioSens (ITMS code: 26220220107) and CEVA II (ITMS code: 26220120040)), by the Slovak Research and Development Agency under the contract APVV-0242-11, and by the project CELIM (316310) funded by 7FP EU.Peer Reviewe