Nonlinear optical response of a gold surface in the visible range: A study by two-color sum-frequency generation spectroscopy. I. Experimental determination

International audienceWe experimentally determine the effective nonlinear second-order susceptibility of gold over the visible spectral range. To reach that goal, we probe by vibrational two-color sum-frequency generation spectroscopy the methyl stretching region of a dodecanethiol self-assembled monolayer adsorbed on a gold film. The sum-frequency generation spectra show a remarkable shape reversal when the visible probe wavelength is tuned from 435 to 705 nm. After correcting from Fresnel effects, the methyl stretching vibrations serve as an internal reference, allowing to extract the dispersion of the absolute phase and relative amplitude of the effective nonlinear optical response of gold in the visible range. Published by AIP Publishing. https://doi

Effect of Nitrogen on Properties of Na2O-CaO-SrO-ZnO-SiO2 Glasses

Glasses in the Na2O-CaO-SrO-ZnO-SiO2 system have previously been investigated for suitability as a reagent in Al-free glass polyalkenoate cements (GPCs). These materials have many properties that offer potential in orthopedics. However, their applicability has been limited, to date, because of their poor strength. This study was undertaken with the aim of increasing the mechanical properties of a series of these Zn-based GPC glasses by doping with nitrogen to give overall compositions of: 10Na2O-10CaO-20SrO-20ZnO-(40-3x)SiO2-xSi3N4 (x is the no. of moles of Si3N4). The density, glass-transition temperature, hardness, and elastic modulus of each glass were found to increase fairly linearly with nitrogen content. Indentation fracture resistance also increases with nitrogen content according to a power law relationship. These increases are consistent with the incorporation of N into the glass structure in threefold coordination with silicon resulting in extra cross-linking of the glass network. This was confirmed using 29Si MAS-NMR which showed that an increasing number of Q2 units and some Q3 units with extra bridging anions are formed as nitrogen content increases at the expense of Q1 units. A small proportion of Zn ions are found to be in tetrahedral coordination in the base oxide glass and the proportion of these increases with the presence of nitrogen

Structure-Property Correlation in Sodium Borophosphate Glasses Modified with Niobium Oxide

Bulk glasses of the series (100−x)[0.4Na2O-0.2Nb2O5-0.4P2O5]-xB2O3 with x = 0–48 mol% B2O3 were prepared by slow cooling in air. Their glass transition temperature increases within the range of 0–16 mol% B2O3, but further additions of B2O3 result in its decrease. Their structure was investigated by Raman, 11B, and 31P MAS NMR spectroscopy. The relative number of BO4 units decreases with increasing B2O3 content, while the number of BO3 units increases up to 59 % at x = 48. The upfield shift of a broad resonance peak in the 31P MAS NMR spectra is ascribed to an increasing connectedness of the structural network with increasing B2O3 content. A strong Raman band at 916–929 cm−1 shows the presence of NbO6 octahedra in the structural network of these glasses. With the B2O3 addition, a decrease in DC conductivity is observed, which is attributed to the decrease in the concentration of Na+ ions

The structure and properties of zinc aluminophosphate glasses

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Le pouvoir alimentaire mondial en question

Cyclope pocheNational audienceLe pouvoir alimentaire, qui consiste à utiliser la fourniture d'aliment pour faire pression sur un partenaire ou un adversaire, est-il en voie de disparition ? Un grand nombre de pays, souvent les plus pauvres, se trouvent en état de dépendance alimentaire vis-à-vis de quelques grandes puissances agro-alimentaires. Le nombre de mal-nourris va-t-il nettement diminuer ou seulement se stabiliser ? La dépendance alimentaire va-t-elle s'aggraver ? Quels sont les facteurs de déstabilisation de la situation alimentaire mondiale ? Les mesures spectaculaires comme embargos et boycotts font-elles partie du passé ? Quel peut être le rôle spécifique de l'Europe en matière de politique agricole et de coopération face à la stratégie récemment réaffirmée des Etats-Unis ? C'est à ces questions cruciales que l'ouvrage tente de répondre

Relace struktura-vlastnosti v borofosfátových sklech barnatých modifikovaných oxidem niobičným

Phosphate glasses containing a high amount of niobium oxide exhibit non-linear optical properties which make them attractive for various optical devices. This contribution is devoted to the investigation of glasses of the series (100 - x)10.5BaO-0.1B(2)O(3)-0.4P(2)O(5)]-xNb(2)O(5) with x = 0-45 and 80[0.5BaO-yB(2)O(3)-(0.5 - y)P2O5]-20Nb(2)O(5) with y = 0-0.25. The basic characteristic parameters of the prepared glasses were determined. The index of refraction of these glasses increases substantially with increasing Nb2O5 content from 1.620 to 2.007 and the glass transition temperature increases within the range of 551-704 degrees C. The glass structure was investigated by P-31, B-11 and Nb-93 NMR, and Raman spectroscopies. Raman spectra revealed that at low Nb2O5 content a strong vibrational band of isolated NbO6 octahedra dominates the spectra. New bands appear in the Raman spectra in the glasses with 30 mol% of Nb2O5 that were assigned to vibrations of Nb-O-Nb bonds interconnecting NbO6 octahedra. B-11 MAS NMR spectra reveal the dominant role of BO4 units in the glass structure. B-11 MAS NMR spectra revealed that with increasing Nb2O5 content new resonances of BO4 units appear in the spectra due to the replacement of B-O-P bonds by B-O-Nb and B-O-B bonds. With an increasing Nb2O5 content, part of the BO4 units is also converted to BO3 units. 93Nb MAS NMR spectra primarily reflect changes in the length of Nb-O bonds in the NbO6 octahedra manifested in a decreasing asymmetry of the octahedra with increasing Nb2O5 content and the formation of niobate clusters. Niobo-borophosphate glasses reveal very high chemical durability as well as high glass transition temperatures due to the replacement of weaker P-O bonds with stronger Nb-O bonds.Fosfátová skla obsahující vysoký obsah oxidu niobičného vykazují nelineární optické vlastnosti, což je činí atraktivními pro různé optické součástky. V tomto článku byla připravena a studována skla řady (100 - x)10.5BaO-0.1B(2)O(3)-0.4P(2)O(5)]-xNb(2)O(5) s obsahem x = 0-45 mol. Nb2O5 a skla 80[0.5BaO-yB(2)O(3)-(0.5 - y)P2O5]-20Nb(2)O(5) s y = 0-0.25. Index lomu těchto skel roste podstatně s růstem obsahu Nb2O5 z hodnoty 1.620 na 2.007 and teplota seklné transformace roste v rozmezí 551-704°C. Struktura skel byla studována NMR spektroskopií jader P-31, B-11 a Nb-93 a též Ramanovou spektroskopií, Ramanova spektra ukázala u skel s nízkým obsahem Nb2O5 přítomnost silného vibračního pásu isolovaných NbO6 oktedrů, které dominují spektrům. V Ramanových spektrech skla se 30 mol.% Nb2O5 se objevují pásy vibrací vazeb Nb-O-Nb propojujících oktaedry NbO6. B-11 MAS NMR spektra ukazují na dominantní roli celků BO4 ve struktuře. skel. B-11 MAS NMR spektra ukázala, že při růstu obsahu Nb2O5 dochází k náhradě vazeb B-O-P vazbami B-O-Nb and B-O-B. 93Nb MAS NMR spectra ukazují na změny délky vazeb Nb-O v oktaedrech NbO6 což vede k poklesu asymetrie oktaedrů NbO6 s růstem obsahu Nb2O5. Nioboborofosfátová skla vykazují vysokou chemickou odolnost a vysoké teploty skelné transformace z důvodu náhrady slabších vazeb P-O silnějšími vazbami Nb-O

Glass-forming ability, structure and physical properties of ZnO–In2O3–P2O5 glasses

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