Influence of the irradiation wavelength on the photocatalytic activity of Au-Pt nanoalloys supported on TiO2 for hydrogen generation from water

[EN] Seven samples of P25 titania containing Au Pt nanoalloys at constant total metal loading (0.25% wt),very similar particle size (1.5 nm) and different proportions of Pt (0.0, 22.8, 27.8, 35.0, 50.0, 69.0 and 100.0% wt) have been prepared and characterized. Formation of real nanoalloys was supported by the shifts in the binding energy values of Au and Pt 4f7/2 peaks in XPS. Using 532 nm laser excitation it was observed that the six samples exhibit similar photocatalytic activity for hydrogen generation in the presence of methanol as a sacrificial electron donor. In contrast, in pure water remarkable differences in efficiency for hydrogen generation between the sample containing exclusively Au that was the most active and the others containing Pt were observed. In addition, oxygen evolution was also observed in the absence of methanol under visible light irradiation. Our results illustrate the potential that nanoalloys offer to optimize the photocatalytic activity of TiO2.Financial support from the Spanish Ministry of Economy and Competitiveness (CTQ2012-31325) is gratefully acknowledged. Partial funding of networking by the European union through project TRAIN2 is also acknowledged. P. Montes-Navajas also thanks the Universidad Politecnica de Valencia for a post-doctoral contract for excellence (CEI-01-11, 20090796).Montes Navajas, PM.; Serra, M.; García Gómez, H. (2013). Influence of the irradiation wavelength on the photocatalytic activity of Au-Pt nanoalloys supported on TiO2 for hydrogen generation from water. Catalysis Science and Technology. 3(9):2252-2258. doi:10.1039/c3cy00102dS225222583

Unexpected solvent isotope effect on the triplet lifetime of methylene blue associated to cucurbit[7]uril

[EN] Methylene blue shows an isotope dependent triplet lifetime that is 50% longer in D2O compared with H2O as a result of electronic-to-vibrational relaxation. The effect is enhanced when the dye is bound to curcubit[7]uril due to a combination of restricted mobility and a unfavorable vibrational coupling.This work was supported by NSERC-Canada. M. G. B thanks the Spanish Ministry of Science and Innovation for a post-doctoral contract. E. A. Acknowledges Becas Chile and the University of Ottawa for postdoctoral fellowships. We also thank Michel Grenier for his help on the time resolved measurements.Alarcón, E.; González Béjar, M.; Montes Navajas, PM.; García Gómez, H.; Lissi, E.; Scaiano, JC. (2012). Unexpected solvent isotope effect on the triplet lifetime of methylene blue associated to cucurbit[7]uril. Photochemical & Photobiological Sciences. 11(2):269-273. doi:10.1039/c1pp05227fS269273112N. J. Turro , V.Ramamurthy and J. C.Scaiano, Modern molecular photochemistry of organic molecules, University Science Books, Sausalito, California, 2010Rekharsky, M. V., Ko, Y. H., Selvapalam, N., Kim, K., & Inoue, Y. (2007). Complexation Thermodynamics of Cucurbit[6]uril with Aliphatic Alcohols, Amines, and Diamines. Supramolecular Chemistry, 19(1-2), 39-46. doi:10.1080/10610270600915292Cohen, M. D., & Schmidt, G. M. J. (1964). 383. Topochemistry. Part I. A survey. Journal of the Chemical Society (Resumed), 1996. doi:10.1039/jr9640001996Cohen, M. D., Hirshberg, Y., & Schmidt, G. M. J. (1964). 389. Topochemistry. Part VII. The photoactivity of anils of salicylaldehydes in rigid solutions. Journal of the Chemical Society (Resumed), 2051. doi:10.1039/jr9640002051Cohen, M. D., Hirshberg, Y., & Schmidt, G. M. J. (1964). 390. Topochemistry. Part VIII. The effect of solvent, temperature, and light on the structure of anils of hydroxynaphthaldehydes. Journal of the Chemical Society (Resumed), 2060. doi:10.1039/jr9640002060Kim, J., Jung, I.-S., Kim, S.-Y., Lee, E., Kang, J.-K., Sakamoto, S., … Kim, K. (2000). New Cucurbituril Homologues:  Syntheses, Isolation, Characterization, and X-ray Crystal Structures of Cucurbit[n]uril (n= 5, 7, and 8). Journal of the American Chemical Society, 122(3), 540-541. doi:10.1021/ja993376pLee, J. W., Samal, S., Selvapalam, N., Kim, H.-J., & Kim, K. (2003). Cucurbituril Homologues and Derivatives:  New Opportunities in Supramolecular Chemistry. Accounts of Chemical Research, 36(8), 621-630. doi:10.1021/ar020254kHennig, A., Ghale, G., & Nau, W. M. (2007). Effects of cucurbit[7]uril on enzymatic activity. Chemical Communications, (16), 1614. doi:10.1039/b618703jKoner, A. L., & Nau, W. M. (2007). Cucurbituril Encapsulation of Fluorescent Dyes. Supramolecular Chemistry, 19(1-2), 55-66. doi:10.1080/10610270600910749Mohanty, J., Pal, H., Ray, A. K., Kumar, S., & Nau, W. M. (2007). Supramolecular Dye Laser with Cucurbit[7]uril in Water. ChemPhysChem, 8(1), 54-56. doi:10.1002/cphc.200600625Shaikh, M., Mohanty, J., Singh, P. K., Nau, W. M., & Pal, H. (2008). Complexation of acridine orange by cucurbit[7]uril and β-cyclodextrin: photophysical effects and pKashifts. Photochem. Photobiol. Sci., 7(4), 408-414. doi:10.1039/b715815gSueishi, Y., Asano, K., Yamaoka, M., & Yamamoto, S. (2008). Characterization of Water-Soluble Cucurbit[7]uril in Alcohol-Water Mixtures by High-Pressure Studies on the Inclusion Complexation with New Methylene Blue. Zeitschrift für Physikalische Chemie, 222(1), 153-161. doi:10.1524/zpch.2008.222.1.153Zhou, Y., Yu, H., Zhang, L., Sun, J., Wu, L., Lu, Q., & Wang, L. (2008). Host properties of cucurbit [7] uril: fluorescence enhancement of acridine orange. Journal of Inclusion Phenomena and Macrocyclic Chemistry, 61(3-4), 259-264. doi:10.1007/s10847-008-9414-8González-Béjar, M., Montes-Navajas, P., García, H., & Scaiano, J. C. (2009). Methylene Blue Encapsulation in Cucurbit[7]uril: Laser Flash Photolysis and Near-IR Luminescence Studies of the Interaction with Oxygen. Langmuir, 25(18), 10490-10494. doi:10.1021/la9011923Montes-Navajas, P., Corma, A., & Garcia, H. (2008). Complexation and Fluorescence of Tricyclic Basic Dyes Encapsulated in Cucurbiturils. ChemPhysChem, 9(5), 713-720. doi:10.1002/cphc.200700735Mohanty, J., & Nau, W. M. (2005). Ultrastable Rhodamine with Cucurbituril. Angewandte Chemie International Edition, 44(24), 3750-3754. doi:10.1002/anie.200500502Montes-Navajas, P., & Garcia, H. (2010). Cucurbituril Complexation Enhances Intersystem Crossing and Triplet Lifetime of 2,4,6-Triphenylpyrylium Ion. The Journal of Physical Chemistry C, 114(5), 2034-2038. doi:10.1021/jp9095166Van Houten, J., & Watts, R. J. (1975). Effect of ligand and solvent deuteration on the excited state properties of the tris(2,2’-bipyridyl)ruthenium(II) ion in aqueous solution. Evidence for electron transfer to solvent. Journal of the American Chemical Society, 97(13), 3843-3844. doi:10.1021/ja00846a062Schmidt, R., & Bodesheim, M. (1994). Time-Resolved Measurement of O2(1.SIGMA.+g) in Solution. Phosphorescence from an Upper Excited State. The Journal of Physical Chemistry, 98(11), 2874-2876. doi:10.1021/j100062a024Hurst, J. R., & Schuster, G. B. (1983). Nonradiative relaxation of singlet oxygen in solution. Journal of the American Chemical Society, 105(18), 5756-5760. doi:10.1021/ja00356a009Schmidt, R., & Brauer, H. D. (1987). Radiationless deactivation of singlet oxygen (1.DELTA.g) by solvent molecules. Journal of the American Chemical Society, 109(23), 6976-6981. doi:10.1021/ja00257a012Rodgers, M. A. J. (1983). TIME RESOLVED STUDIES OF 1.27 μm LUMINESCENCE FROM SINGLET OXYGEN GENERATED IN HOMOGENEOUS and MICROHETEROGENEOUS FLUIDS. Photochemistry and Photobiology, 37(1), 99-103. doi:10.1111/j.1751-1097.1983.tb04440.xRodgers, M. A. J., & Snowden, P. T. (1982). Lifetime of oxygen (O2(1.DELTA.g)) in liquid water as determined by time-resolved infrared luminescence measurements. Journal of the American Chemical Society, 104(20), 5541-5543. doi:10.1021/ja00384a070Ogilby, P. R., & Foote, C. S. (1983). Chemistry of singlet oxygen. 42. Effect of solvent, solvent isotopic substitution, and temperature on the lifetime of singlet molecular oxygen (1.DELTA.g). Journal of the American Chemical Society, 105(11), 3423-3430. doi:10.1021/ja00349a007Gardner, P. J., & Kasha, M. (1969). Electronic Consequences of Vibrational Deficiency in Polyatomic Molecules. The Journal of Chemical Physics, 50(4), 1543-1552. doi:10.1063/1.1671240Schweitzer, C., & Schmidt, R. (2003). Physical Mechanisms of Generation and Deactivation of Singlet Oxygen. Chemical Reviews, 103(5), 1685-1758. doi:10.1021/cr010371dS. L. Murov , I.Carmichael and G. L.Hug, Handbook of photochemistry, Mercel Decker Inc, New York, 1993Beeby, A., Parker, A. W., Simpson, M. S. C., & Phillips, D. (1992). The effect of solvent deuteration on the photophysics of sulphonated aluminium phthalocyanine. Journal of Photochemistry and Photobiology B: Biology, 16(1), 73-81. doi:10.1016/1011-1344(92)85154-mNau, W. M., & Mohanty, J. (2005). Taming fluorescent dyes with cucurbituril. International Journal of Photoenergy, 7(3), 133-141. doi:10.1155/s1110662x05000206Alarcón, E., Edwards, A. M., Aspee, A., Moran, F. E., Borsarelli, C. D., Lissi, E. A., … Scaiano, J. C. (2010). Photophysics and photochemistry of dyes bound to human serum albumin are determined by the dyelocalization. Photochem. Photobiol. Sci., 9(1), 93-102. doi:10.1039/b9pp00091gDavila, J., & Harriman, A. (1990). PHOTOREACTIONS OF MACROCYCLIC DYES BOUND TO HUMAN SERUM ALBUMIN. Photochemistry and Photobiology, 51(1), 9-19. doi:10.1111/j.1751-1097.1990.tb01678.xEngst, P., Kubát, P., & Jirsa, M. (1994). The influence of D2O on the photophysical properties of meso-tetra (4-sulphonatophenyl) porphine, Photosan III and tetrasulphonated aluminium and zinc phthalocyanines. Journal of Photochemistry and Photobiology A: Chemistry, 78(3), 215-219. doi:10.1016/1010-6030(93)03730-5Jensen, R. L., Arnbjerg, J., & Ogilby, P. R. (2010). Temperature Effects on the Solvent-Dependent Deactivation of Singlet Oxygen. Journal of the American Chemical Society, 132(23), 8098-8105. doi:10.1021/ja101753nLipert, R. J., & Colson, S. D. (1989). Deuterium isotope effects on S1 radiationless decay in phenol and on intermolecular vibrations in the phenol-water complex. The Journal of Physical Chemistry, 93(1), 135-139. doi:10.1021/j100338a030Tanielian, C., & Wolff, C. (1995). Determination of the Parameters Controlling Singlet Oxygen Production via Oxygen and Heavy-Atom Enhancement of Triplet Yields. The Journal of Physical Chemistry, 99(24), 9831-9837. doi:10.1021/j100024a02

Sistemas supramoleculares basados en la encapsulación en cucurbit(n)uriles

Desde el comienzo de su modernización a finales del siglo XVIII, la Química se ha desarrollado continua y rápidamente a través de la teoría atómico-molecular; sin embargo, esta química del enlace covalente ha sido explotada hasta sus límites conceptuales, de forma que incluso el mejor químico sintético de hoy día no puede fabricar sistemas moleculares complicados usando sólo el repertorio de herramientas disponibles para crear enlaces covalentes. Puesto que el siguiente paso al aumentar el nivel de complejidad hacia los sistemas polimoleculares organizados presentes en los sistemas vivos se encuentra unido a las interacciones no covalentes, es el momento de que los químicos miren más allá de la síntesis clásica hacia la Química Supramolecular, una rama relativamente joven de la ciencia que se preocupa del estudio de las características básicas de estas interacciones no covalentes. En los últimos 25 años, una enorme parte de la investigación química se ha detenido en el campo de los dispositivos moleculares fotoactivos, observando que los resultados que pueden ser obtenidos de la interacción de la luz con la materia dependen del grado de organización de la misma; en este sentido, las entidades supramoleculares que contienen este tipo de componentes pueden desarrollar propiedades nuevas moduladas por la disposición de sus unidades constitutivas, dando lugar a procesos fotoquímicos distintivos de estas especies. A través de esta ruta es posible disponer componentes moleculares prefabricados que lleven a cabo una determinada propiedad relacionada con la luz, siendo posible diseñar sistemas organizados y funcionalmente integrados capaces de elaborar la señal proporcionada por los fotones para desarrollar funciones complejas.Montes Navajas, PM. (2009). Sistemas supramoleculares basados en la encapsulación en cucurbit(n)uriles [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/6281Palanci

Síntesis de perilenodiimidas solubles en agua como sensores fluorescentes

[ES] Una de las herramientas más utilizadas de la Biotecnología son las moléculas sonda fluorescentes que permitan extraer información analítica, no sólo cualitativa sino sobre todo cuantitativa, de diferentes procesos biológicos. Desde el punto de vista químico, todos estos compuestos presentan unas características fisicoquímicas especialmente apropiadas para cada aplicación concreta, pero todas ellas deben presentar una alta solubilidad en medios acuosos y fluidos biológicos. En este sentido, la búsqueda de nuevos quimiosensores debe enfocarse, por un lado, al diseño y síntesis de moléculas altamente fluorescentes capaces de modificar sus propiedades fotofísicas al interaccionar con analitos de importancia biológica y, por otro lado, aumentar su hidrosolubilidad y selectividad por los compuestos diana deseados. Por todo ello, la familia de derivados de perileno en general y las perilenodiimidas en particular presentan estos requisitos para poder ser aplicados en sistemas de detección biotecnológicos. Así, se pretende sintetizar una perilenodiimida bifuncionalizada mediante la condensación de dos unidades perilenomonoanhídridodiéster con cadenas pegiladas derivadas del etilenglicol que, por un lado, aumenten la solubilidad de la molécula en medios biológicos y, por otro lado, sirven para interaccionar con cationes fisiológicamente importantes debido a interacciones con dichas cadenas[EN] One of the most used tools of biotechnology are fluorescent probe molecules which can extract, not only qualitative but mostly quantitative analytical information, about different biological processes. From the chemical point of view, all these compounds have the appropriate physicochemical features for each particular application, but all of them should have a high solubility in aqueous media and biological fluids. As a result, the search for new chemosensors should focus on the one hand, on the design and synthesis of highly fluorescent molecules capable to modify their photophysical properties at the time they interact with analytes of biological significance and, on the other hand, increase their water solubility and selectivity for desired target compounds. Therefore, the family of perylene derivatives in general and perylenediimides in particular present these requirements to be applied in biotechnological systems detection. Thus, it is intended to synthesize a bifunctionalized perylendiimide by condensing two units of perylenemonoanhidridediester with pegylated chains derived from ethylene glycol in order to, on the one hand, increase the solubility of the molecule in biological media and, on the other hand, serve to interact with physiologically important cations due to interactions with such chains.Montes Navajas, PM. (2017). Síntesis de perilenodiimidas solubles en agua como sensores fluorescentes. http://hdl.handle.net/10251/89640TFG

Influence of CB[n] complexation on the quenching of 2,4,6-triphenylpyrylium excited states by Fe2+ ions

[EN] This manuscript focuses on the influence that the addition of Fe2+ as electron donor quencher exerts on the photophysics of 2,4,6-triphenylpyrylium (TP+) depending on the formation or not of supramolecular inclusion complexes with cucurbit[n]uril (n: 7 or 8). 1H-NMR spectroscopy does not provide evidence supporting the formation of a ternary TP+@CB[n] Fe2+ complex. Emission quenching studies indicate that the prevalent deactivation mechanism for the quenching of TP+ emission by Fe2+ is by increasing the ionic strength of the solution, with no evidence for the occurrence of dynamic quenching. Laser flash photolysis indicates that while the triplet excited state of TP+ is instantaneously quenched by Fe2+ in the absence of CB[n], formation of the TP+@CB[n] inclusion complex protects TP+ triplet excited state from quenching, an effect that is more pronounced in the case of CB[8] due to the deeper penetration and more complete encapsulation of the heterocyclic pyrylium core inside the larger CB[8] capsule.Financial support by the Spanish Ministry of Economy and Competitiviness (CTQ2012-31325) and Generalidad Valenciana (Prometeo 20127014) is gratefully acknowledged. P. Montes-Navajas also thanks the Universidad Politecnica de Valencia for a post-doctoral contract for excellence (CEI-01-11, 20090796).Montes Navajas, PM.; García Gómez, H. (2013). Influence of CB[n] complexation on the quenching of 2,4,6-triphenylpyrylium excited states by Fe2+ ions. Journal of Colloid and Interface Science. 410:111-115. https://doi.org/10.1016/j.jcis.2013.08.016S11111541

Constrasting photocatalytic activity of commercial TiO2 samples for hydrogen generation

series of 20 commercial titanium dioxide samples, including Evonik P-25, Millenium, Huntsman,Crenox, Kronnos or Hombikat, have been tested as photocatalysts for hydrogen generation from wateror water/methanol mixtures under monochromatic visible light (532 nm) or polychromatic simulatedsun light irradiation. Remarkable variations in the photocatalytic activity were found from one sample toother. While the most active sample under monochromatic 532 nm irradiation was Millenium Tiona 595and the photocatalytic activity ranking follows the order of the red shift of the absorption band onset, theranking under simulated sun light was different and difficult to rationalize. Under simulated sun lightirradiation, the most active samples were Evonik P25 and Dupont Ti-pure. Overall, our study is of interestto illustrate the large variation in the photocatalytic activities for commercial TiO2samples dependingon the photocatalytic reaction and conditions used.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2012-32315) is gratefully acknowledged. P. Montes-Navajas also thanks the Universidad Politecnica de Valencia for a postdoctoral contract for excellence (CEI-01-11, 20090796).Montes Navajas, PM.; Serra, M.; Corma Canós, A.; García Gómez, H. (2014). Constrasting photocatalytic activity of commercial TiO2 samples for hydrogen generation. Catalysis Today. 225:52-54. https://doi.org/10.1016/j.cattod.2013.09.025S525422

Host guest complexes between cucurbit[n]urils and acetanilides having aminopropyl units

[EN] 2-(Propylamino)acetamide of aniline (1a), and bis-2-(propylamino)acetamide of ortho- (1b) and para-(1c) phenylenediamine form host-guest complexes with CB[6], CB[7] and CB[8] as evidenced by the variations in the H-1 NMR spectroscopy chemical shifts and observation in MALDI-TOF-MS and ESI-MS of ions at the corresponding mass. Binding constants for the 1:1 complexes were estimated from fluorescence titrations and were in the range 10(5)-10(6) M-1. Models based on molecular mechanics for these supramolecular complexes are provided. In spite of the different geometries arising from the ortho- or para-substitution, phenylenediamides form complexes of similar strength in which the hydrophobic alkyl chains are accommodated inside the host cavity. Formation of these host-guest complexes in the solid state was also achieved by modifying an aminopropyl silica with chloroacetanilides and preparing three silica having analogues of compounds 1a-c anchored to the solid particles. Titrations showed, however, that these solids can adsorb a large percentage of CBs by unselective interactions that are not related to the formation of inclusion complexes.Financial support by the Spanish Ministry of Science and Education (CTQ2012-36351 and CTQ2010-18671) is gratefully acknowledged. Mireia Buaki-Sogo also thanks the Spanish ministry for a post-graduate scholarship (CTQ2007-67805).Buaki-Sogo, M.; Montes Navajas, PM.; Alvaro Rodríguez, MM.; García Gómez, H. (2013). Host guest complexes between cucurbit[n]urils and acetanilides having aminopropyl units. Journal of Colloid and Interface Science. 399:54-61. https://doi.org/10.1016/j.jcis.2013.02.027S546139

Surface area measurement of graphene oxide in aqueous solutions

Graphene oxide (GO) forms persistent dispersions in aqueous solutions up to concentrations of 0.2 mg mL(-1). Addition of methylene blue (MB) to these aqueous dispersion of GO gives rise to the observation in optical spectroscopy of new absorption bands that are indicative of the formation of MB/GO conjugates. Four new absorption maxima have been characterized, and their intensity varies depending on the relative concentration of MB with respect to GO. Two of these bands appearing at 677 and 757 nm correspond to individual MB molecules adsorbed on neutral or acid sites of GO, respectively. Two other bands at 615 and 580 nm are attributable to adsorbed MB molecules showing interaction with other neighbor dye molecules at incomplete (615 nm) or complete (580 nm) surface coverage. Complete coverage of GO surface by MB causes the formation of a precipitate and the separation of the MB/GO conjugate. EDS mapping of carbon and sulfur atoms of MB/GO conjugate indicates the homogeneous distribution of MB molecules coating GO sheets. A simple and reliable protocol for surface area measurement and determination of the level of aggregation for GO dispersions in water has been proposed by determining the amount of MB that leads to the maximum intensity of the 580 nm band and precipitation of the MB/GO conjugate. Specific surface area as high as 736.6 m(2) g(-1) in the range of the theoretical value for GO has been experimentally measured for diluted GO solutions, but aggregation levels of 15% were estimated for GO concentration of 50 mu g mL(-1).Financial support by the Spanish Ministry of Economy and Competitiviness (Sever Ochoa, Generalitat Valenciana (Prometeo 20112/013) and CTQ2012-32315) is gratefully acknowledged. P. Montes-Navajas also thanks the Universidad Politecnica de Valencia for a postdoctoral contract for excellence (CEI-01-11, 20090796). The authors also thank the Spanish Science and Innovation Ministry (CONSOLIDER INGENIO 2010, ref. CSD2009-00050) for their financial support.Montes Navajas, PM.; Asenjo, NG.; Santamaria, R.; Menendez, R.; Corma Canós, A.; García Gómez, H. (2013). Surface area measurement of graphene oxide in aqueous solutions. Langmuir. 29(44):13443-13448. https://doi.org/10.1021/la4029904S1344313448294

Clinical guidelines for endoscopic mucosal resection of non-pedunculated colorectal lesions

This document summarizes the contents of the Clinical Guidelines for the Endoscopic Mucosal Resection of Non-Pedunculated Colorectal Lesions that was developed by the working group of the Spanish Society of Digestive Endoscopy (GSEED of Endoscopic Resection). This document presents recommendations for the endoscopic management of superficial colorectal neoplastic lesions

Clinical guidelines for endoscopic mucosal resection of non-pedunculated colorectal lesions.

This document summarizes the contents of the Clinical Guidelines for the Endoscopic Mucosal Resection of Non-Pedunculated Colorectal Lesions that was developed by the working group of the Spanish Society of Digestive Endoscopy (GSEED of Endoscopic Resection). This document presents recommendations for the endoscopic management of superficial colorectal neoplastic lesions