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José M. G. Martinho

Bio: José M. G. Martinho is an academic researcher from Instituto Superior Técnico. The author has contributed to research in topics: Excimer & Pyrene. The author has an hindex of 38, co-authored 216 publications receiving 5345 citations. Previous affiliations of José M. G. Martinho include Centre national de la recherche scientifique & École normale supérieure de Lyon.


Papers
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Journal ArticleDOI
TL;DR: In this critical review the strategies for modification of Rhodamine dyes and a discussion on the variety of applications of these new derivatives as fluorescent probes are given.
Abstract: Rhodamine dyes are widely used as fluorescent probes owing to their high absorption coefficient and broad fluorescence in the visible region of electromagnetic spectrum, high fluorescence quantum yield and photostability. A great interest in the development of new synthetic procedures for preparation of Rhodamine derivatives has arisen in recent years because for most applications the probe must be covalently linked to another (bio)molecule or surface. In this critical review the strategies for modification of Rhodamine dyes and a discussion on the variety of applications of these new derivatives as fluorescent probes are given (108 references).

1,204 citations

Journal ArticleDOI
TL;DR: These clusters of only two and three atoms show stable photoluminescent and magnetic properties, which make them the smallest and most elemental gold building blocks in nature (after atoms) bringing new possibilities to construct novel nano/microstructures with large potential interest in biomedicine, catalysis, and so forth.
Abstract: Gold atomic clusters of only two and three atoms were prepared by a simple electrochemical technique based on the anodic dissolution of a gold electrode in the presence of PVP, and subsequent electroreduction of the Au-PVP complexes These clusters show stable photoluminescent and magnetic properties, which make them the smallest and most elemental gold (0) building blocks in nature (after atoms) bringing new possibilities to construct novel nano/microstructures with large potential interest in biomedicine, catalysis, and so forth

158 citations

Journal ArticleDOI
25 Dec 1996-Langmuir
TL;DR: In this article, the surface pressure area (﷿-A) isotherms at the air-water interface of poly(styrene)-poly(ethylene oxide) diblock copolymers (PSm-PEOn,m 38,n ) 90, 148, 250, and 445) have been studied at several temperatures.
Abstract: Spread monolayers of poly(styrene)-poly(ethylene oxide) diblock copolymers (PSm-PEOn,m )38,n ) 90, 148, 250, and 445) have been studied at the air-water interface by measuring the surface pressurearea (﷿-A) isotherms at several temperatures. The ﷿-A isotherms exhibit several regions which can be ascribed to different conformations of the polymer chains: a pancake structure at low surface pressures and high areas when the isolated chains are adsorbed by both the PS globule and the PEO segments at the interface; an intermediate structure, quasi-brush, when the PEO segments are solubilized in the subphase; and finally a brush developed at low surface areas when the PEO chains are obliged to stretch away from the interface to avoid overlapping. At surface pressures near 10 mN/m there is a transition between a high-density pancake and the quasi-brush regime. The compression and the subsequent expansion curves superpose at the transition and quasi-brush regions but not at the brush and pancake stages. This points to a high cohesion in the brush structure after compression and to some irreversible entanglementandhydrationofthePEOchainswhenimmersedinthesubphase. Thesetwolocalhystereses depend differently on the PEO chain length and temperature. The hysteresis observed at high surface pressures (brush conformation) decreases with the PEO length and temperature, whereas the low surface pressure hysteresis (pancake) increases with PEO chain length, decreases with temperature in the range 283-298 K, and increases in the range 298-315 K. A negative mean transition entropy change was obtainedfromthetemperaturedependenceofthequasi-SSAL-quasi-brushtransition. Theresultsindicate that the extensive properties of the present diblock copolymers at the interface, such as the pancake limiting area and the mean transition entropy, when expressed by PEOmer, are independent of the PEO length.

151 citations

Journal ArticleDOI
TL;DR: In this article, the authors highlight the state of the art in the strategies leading to one and only one precisely localized dye per polymer chain, which can be introduced at three different steps of the polymerization: i) at the very beginning via the initiator or a chain transfer agent, ii) during polymerization via a functional monomer or a quencher, or iii) after polymerisation via covalent binding of a dye-derivative.

109 citations

Journal ArticleDOI
06 Aug 1998-Langmuir
TL;DR: In this article, the authors investigated the effect of block polyelectrolyte length and temperature on the formation of block copolymers at the air-water interface, and showed that the effects of the length of the PEO chains and the amount of stearic acid on the expansion of the PS38-PEO90 block can be observed.
Abstract: Amphiphilic block copolymers form an important class of materials which have attracted considerable attention because of their outstanding solution properties and a wide range of applications.1,2 These materials are very interesting from the point of view of fundamental research, as they exhibit self-assembling properties in the presence of a selective solvent or surface.3-7 Surface micelles at the air-water interface, of different morphologies depending on the balance between block sizes, have been directly identified by TEM and AFM for block polyelectrolytes8,9 and for nonionic diblock copolymers.10 The present work was mainly motivated by a previous work on monolayers of poly(styrene)-poly(ethylene oxide), PSm-PEOn diblock copolymers, with varying lengths of the PEO block, spread at the air-water interface.11 As for grafted polymers,12-14 a pancake, a quasi-brush state, and a brush state were observed. It was found that compression-expansion cycles of the π-A isotherms superpose in the quasi-brush but not in the brush and pancake regions.11 The hysteresis observed at low surface pressures (pancake region) increases with PEO chain length and decreases with temperature. This was attributed to the irreversible entanglement and hydration of the PEO chains when immersed in the water subphase. The hysteresis at high surface pressuressin the brush regionsexhibited an unusual minimum in the expansion curve. This peculiar shape of the π-A isotherms suggests that the system undergoes a metastable regime during the expansion and finally returns to the equilibrium when the compression and the expansion curves superimpose in the quasi-brush region. The increase of π with the area indicates a overexpanded monolayer due to the high cohesion and local order reached in the brush conformation which is not disrupted in the time scale of the expansion run. This effect tends to disappear with an increase of PEO length and temperature. Both effects difficult the organization of PEO chains and diminish the cohesion. To further clarify this subject, the initial work was extended to study the effect of the concentration of the spreading solution, initial surface concentration of the monolayer, and a number of other experimental variables, namely maximum surface pressure reached on the compression run, rate of the compression-expansion cycles, and number of successive cycles. The present work studies further the influence of the PEO length and shows that the minimum on the π-A isotherms of PS38-PEO90 disappears in the presence of various amounts of stearic acid (SA). Dynamic light scattering measurements show aggregation of the block copolymers PS38-PEO90 and PS38-PEO148 in chloroform solutions, for the same range of concentrations used in the film balance measurements.

84 citations


Cited by
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Journal ArticleDOI
TL;DR: Van Kampen as mentioned in this paper provides an extensive graduate-level introduction which is clear, cautious, interesting and readable, and could be expected to become an essential part of the library of every physical scientist concerned with problems involving fluctuations and stochastic processes.
Abstract: N G van Kampen 1981 Amsterdam: North-Holland xiv + 419 pp price Dfl 180 This is a book which, at a lower price, could be expected to become an essential part of the library of every physical scientist concerned with problems involving fluctuations and stochastic processes, as well as those who just enjoy a beautifully written book. It provides an extensive graduate-level introduction which is clear, cautious, interesting and readable.

3,647 citations

Journal ArticleDOI
TL;DR: An overview of the basic photophysics and electron transfer theory is presented in order to provide a comprehensive guide for employing this class of catalysts in photoredox manifolds.
Abstract: In this review, we highlight the use of organic photoredox catalysts in a myriad of synthetic transformations with a range of applications. This overview is arranged by catalyst class where the photophysics and electrochemical characteristics of each is discussed to underscore the differences and advantages to each type of single electron redox agent. We highlight both net reductive and oxidative as well as redox neutral transformations that can be accomplished using purely organic photoredox-active catalysts. An overview of the basic photophysics and electron transfer theory is presented in order to provide a comprehensive guide for employing this class of catalysts in photoredox manifolds.

3,550 citations

Journal ArticleDOI
TL;DR: The Rehybridization of the Acceptor (RICT) and Planarization ofThe Molecule (PICT) III is presented, with a comparison of the effects on yield and radiationless deactivation processes.
Abstract: 6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

2,924 citations

Journal ArticleDOI
TL;DR: School of Chemistry, Bio21 Institute, University of Melbourne, 30 Flemington Road, Victoria 3010, Australia; School of Materials Science and Engineering, Nanyang Technological University, Nastyang Avenue, Republic of Singapore 639798; Institute of Materials Research and Engineering (IMRE) and the Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore 117602.
Abstract: A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

2,378 citations