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1.
Nanoscale ; 11(15): 7404-7413, 2019 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-30938744

RESUMO

Light scattering from small particles exhibit unique angular scattering distributions, which are strongly dependent on the radius to wavelength ratio as well as the refractive index contrast between the particles and the surrounding medium. As the concentration of the particles increases, multiple scattering becomes important. This complicates the description of the angular scattering patterns, and in many cases one has to resort to empirical phase functions. We have measured the angle dependence of light scattering from a polymer layer containing sub-micron metallic and dielectric particles. The samples exhibited strongly forward and backward peaked scattering patterns, which were fitted to a number of empirical approximative phase functions. We found that a novel two-term Reynolds-McCormick (TTRM) phase function gave the best fit to the experimental data in all cases. The feasibility of the TTRM approach was further validated by good agreement with numerical simulations of Mie single scattering phase functions at various wavelengths and sizes, ranging from the Rayleigh scattering regime to the geometrical optics regime. Hence, the widely adaptable TTRM approach is able to describe angular scattering distributions of different kinds of nanospheres and nanocomposites, both in the single scattering and multiple scattering regimes.

2.
J Inorg Biochem ; 187: 56-61, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30055396

RESUMO

Herein we report on the hydrolysis mechanism of [Pt{N(p-HC6F4)CH2}2(NC5H5)2(OH)2], a platinum(IV) complex that exhibits anti-cancer properties. Atomic telemetry, an in situ technique based on electron structure sensitive X-ray spectroscopy, revealed that hydrolysis preceded any reduction of the metal center. The obtained results are complemented with 19F NMR measurements and theoretical calculations and support the observation that this PtIV complex does not reduce spontaneously to PtII in HEPES buffer solution at pH 7.4 and after 24 h incubation. These results are of importance for the design of novel Pt-based coordination complexes as well as understanding their behavior under physiological conditions.


Assuntos
Compostos Organoplatínicos/química , Platina/química , Espectroscopia de Ressonância Magnética , Espectroscopia por Absorção de Raios X
3.
Sci Rep ; 7(1): 8670, 2017 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-28819324

RESUMO

The efficient conversion of light energy into chemical energy is key for sustainable human development. Several photocatalytic systems based on photovoltaic electrolysis have been used to produce hydrogen via water reduction. However, in such devices, light harvesting and proton reduction are carried separately, showing quantum efficiency of about 10-12%. Here, we report a nano-hybrid photocatalytic assembly that enables concomitant reductive hydrogen production and pollutant oxidation with solar-to-fuel efficiencies up to 20%. The modular architecture of this plasmonic material allows the fine-tuning of its photocatalytic properties by simple manipulation of a reduced number of basic components.

4.
J Phys Chem Lett ; 8(4): 805-811, 2017 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-28151686

RESUMO

The lack of molecular mechanistic understanding of the interaction between metal complexes and biomolecules hampers their potential medical use. Herein we present a robust procedure combining resonant X-ray emission spectroscopy and multiscale molecular dynamics simulations, which allows for straightforward elucidation of the precise interaction mechanism at the atomic level. The report unveils an unforeseen hydrolysis process and DNA binding of [Pt{N(p-HC6F4)CH2}2py2] (Pt103), which showed potential cytotoxic activity in the past. Pt103 preferentially coordinates to adjacent adenine sites, instead of guanine sites as in cisplatin, because of its hydrogen bond ability. Comparison with previous research on cisplatin suggests that selective binding to guanine or adenine may be achieved by controlling the acidity of the compound.


Assuntos
Complexos de Coordenação/química , DNA/química , Modelos Moleculares , Adenina/química , Cisplatino/química , Guanina/química , Ligação de Hidrogênio , Simulação de Dinâmica Molecular , Compostos Organoplatínicos/química , Espectrometria por Raios X , Telemetria
5.
Angew Chem Int Ed Engl ; 55(40): 12306-10, 2016 09 26.
Artigo em Inglês | MEDLINE | ID: mdl-27604393

RESUMO

For the first time, organic semiconducting polymer dots (Pdots) based on poly[(9,9'-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3} thiadiazole)] (PFBT) and polystyrene grafting with carboxyl-group-functionalized ethylene oxide (PS-PEG-COOH) are introduced as a photocatalyst towards visible-light-driven hydrogen generation in a completely organic solvent-free system. With these organic Pdots as the photocatalyst, an impressive initial rate constant of 8.3 mmol h(-1) g(-1) was obtained for visible-light-driven hydrogen production, which is 5-orders of magnitude higher than that of pristine PFBT polymer under the same catalytic conditions. Detailed kinetics studies suggest that the productive electron transfer quench of the excited state of Pdots by an electron donor is about 40 %. More importantly, we also found that the Pdots can tolerate oxygen during catalysis, which is crucial for further application of this material for light-driven water splitting.

6.
Analyst ; 141(4): 1226-32, 2016 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-26805912

RESUMO

Platinum-based drugs are commonly used in cancer treatment. The biological activity of a metallodrug is obviously closely related to its chemical and stereochemical characteristics. An overlooked aspect is the effect of the ligand to the electronic structure of the metal atom (coordinated atom). We report herein a Resonant X-ray Emission Spectroscopy (RXES) study on the chemical speciation of chiral platinum complexes in which diastereomers are distinguished on the basis of their metal electronic configuration. This demonstrates RXES high chemical speciation capabilities, a necessary property to further investigate the reactivity of the Pt atom towards nucleophiles or bionucleophiles, and an important complement the previously reported RXES abilities, namely that it can be employed for in situ studies at physiological concentrations.


Assuntos
Antineoplásicos/química , Compostos Organoplatínicos/química , Espectrometria por Raios X , Flúor/química , Ligantes , Estereoisomerismo
7.
Drug Discov Today Technol ; 16: 1-6, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26547415

RESUMO

This review presents a new application of Resonant X-ray Emission Spectroscopy (RXES) to study the mechanism of action of metal containing anticancer derivatives and in particular platinum in situ and in vivo. The technique is an example of a photon-in photon-out X-ray spectroscopic approach, which enables chemical speciation of drugs to be determined and therefore to derive action mechanisms, and to determine drug binding rates under physiological conditions and therapeutic concentrations. This is made feasible due to the atomic specificity and high penetration depth of RXES. The review presents examples of the three main types of information that can be obtained by RXES and establishes an experimental protocol to perfect the measurements within cells.


Assuntos
Complexos de Coordenação/química , Nanopartículas Metálicas/química , Neoplasias/diagnóstico por imagem , Espectrometria por Raios X/métodos , Animais , Antineoplásicos/química , Antineoplásicos/metabolismo , Antineoplásicos/uso terapêutico , Complexos de Coordenação/uso terapêutico , Humanos , Nanopartículas Metálicas/uso terapêutico , Neoplasias/tratamento farmacológico , Neoplasias/metabolismo , Radiografia
8.
Chem Commun (Camb) ; 51(54): 10914-6, 2015 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-26060844

RESUMO

Understanding electron mobility on TiO2 is crucial because of its applications in photocatalysis and solar cells. This work shows that shallow traps believed to be involved in electron migration in TiO2 conduction band are formed upon band gap excitation, i.e., are not pre-existing states. The shallow traps in TiO2 results from large polarons and are not restricted to surface.

9.
Phys Chem Chem Phys ; 17(28): 18262-4, 2015 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-26105785

RESUMO

We report on the reactivity of grafted tantalum organometallic catalysts with molecular oxygen. The changes in the local Ta electronic structure were followed by in situ high-energy resolution off-resonant spectroscopy (HEROS). The results revealed agglomeration and formation of Ta dimers, which cannot be reversed. The process occurs independently of starting grafted complex.

10.
J Biol Inorg Chem ; 20(5): 841-53, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25982100

RESUMO

The structure-activity relationships of chiral 1,2-diaminophenylalkane platinum(II) anticancer derivatives are studied, including interactions with telomeric- and genomic-like DNA sequences, the pKa of their diaqua species, structural properties obtained from DFT calculations and resonant X-ray emission spectroscopy. The binding modes of the compounds to telomeric sequences were elucidated, showing no major differences with conventional cis-platinum(II) complexes like cisplatin, supporting that the cis-square planar geometry governs the binding of small Pt(II) complexes to G4 structures. Double-stranded DNA platination kinetics and acid-base constants of the diaqua species of the compounds were measured and compared, highlighting a strong steric dependence of the DNA-binding kinetics, but independent to stereoisomerism. Structural features of the compounds are discussed on the basis of dispersion-corrected DFT, showing that the most active series presents conformers for which the platinum atom is well devoid of steric hindrance. If reactivity indices derived from conceptual DFT do not show evidences for different reactivity between the compounds, RXES experiments provide new insight into the availability of platinum orbitals for binding to nucleophiles.


Assuntos
Antineoplásicos/química , Antineoplásicos/farmacologia , DNA de Neoplasias/efeitos dos fármacos , Hidrocarbonetos Clorados/farmacologia , Compostos Organoplatínicos/química , Compostos Organoplatínicos/farmacologia , DNA de Neoplasias/genética , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Quadruplex G/efeitos dos fármacos , Humanos , Hidrocarbonetos Clorados/química , Concentração de Íons de Hidrogênio , Cinética , Modelos Moleculares , Estrutura Molecular , Teoria Quântica , Relação Estrutura-Atividade
11.
Phys Chem Chem Phys ; 14(7): 2164-70, 2012 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-21909561

RESUMO

An autoclave reactor was modified to perform simultaneously high energy resolution fluorescence detected X-ray absorption spectroscopy (HERFD XAS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy measurements without altering the reactor design. This operando cell allows one to follow changes in the electronic and geometric structure of the catalyst with HERFD XAS and relate them to the simultaneously detected activity and reaction species with ATR-FTIR formed during the reaction in the liquid phase. The capability of the cell is demonstrated by two studies. The first shows the reduction of Au/CeO(2) precursors in different solvents. The second shows that mainly Au(0) is present in the hydrogenation of nitrobenzene over Au/CeO(2).

12.
Talanta ; 77(1): 77-83, 2008 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-18804602

RESUMO

A new electronic nose was developed to identify the chemical compound released when a 2.5-L flask was broken inside a 3 m x 3 m x 2.5 m store-room. Flasks of 10 different hazardous compounds were initially present in the room: ammonia, propanone, hexane, acetic acid, toluene, methanol, tetrachloromethane, chloroform, ethanol and dichloromethane. Besides identification, quantification of the compound present in the air was also performed by the electronic nose, in order to evaluate the risk level for room cleaning. An array of six sensors based on coated piezoelectric quartz crystals was used. Although none of the individual sensors was specific for a single compound, an artificial neural network made it possible to identify and quantify the released vapour, among a series of 10 compounds, with six sensors. The neural network could be simplified, and the number of neurons reduced, provided it was used just for the identification task. Quantification could be performed later using the individual calibration of the sensor most sensitive to the identified compound.

13.
Anal Chim Acta ; 617(1-2): 171-6, 2008 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-18486654

RESUMO

An electronic nose based on acoustic wave sensors has been developed to detect spoilt fruit. Different varieties of fruits, edible and rotten, were analysed. Starting from six sensors, the minimum number of sensors capable of discriminating between spoiled and unspoiled fruit was found. The discrimination capability of the sensor array was studied separately for each fruit variety, as well as for the whole set. Mathematical models were built to classify the fruits within a fruit variety, in an objective and clear way. The models were able to distinguish between edible and rotten fruits with 100% success for New Hall oranges, Golden apples, Kiwis and William pears, and with 97.2% of success for the Starking apples. Without forming fruit variety subsets, discrimination between edible and rotten fruit was achieved with 95% success.

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