Plasmonic Nanoparticles Driven Enhanced Light Amplification in a Local 2D and 3D Self-Assembly

We present fluorescence and a random lasing enhancement effect due to the interaction between gold nanoparticles (AuNPs) and Rhodamine 6G (Rh6G) dye. Non-covalently bounded dyes in the proximity of nanoparticles are studied in three systems of varying dimensionality: from (i) three-dimensional freely distributed suspensions, through (ii) quasi-two-dimensional multilamellar liposomes, to (iii) solid two-dimensional thin layers. Liposomes facilitate the formation of stable AuNPs/Rh6G composition showing enhanced fluorescence, while solid thin films exhibit plasmon-assisted random lasing

Room temperature synthesis of CdSe/CdS triangular nanoemitters and their stabilization in colloidal state and sol–gel glass

Heterostructured cadmium-based core-shell nanoparticles (NPs) are the subject of research because of not only fundamental scientific advances but also a range of technological applications. To increase the range of applications of nanoparticles, it is possible to immobilise them in sol-gel glass that can be easily manufactured and shaped, keeping the properties of the dispersed particles. This allows the creation of new bulk optical materials with tailored properties, opening up opportunities for various technological applications such as lighting or sensing. Herein we report the synthesis of core-shell CdSe/CdS triangular-shaped nanoparticles under an atmosphere of oxygen and at room temperature. A detailed characterisation of the obtained NPs was carried out. The interesting effect of the gelling agent (tetra-nbutylammonium fluoride) on the triangular nanoparticles in solution and the stability of the emission properties over time was investigated. Sol-gel glasses with entrapped triangular NPs were prepared, and their photoluminescence properties were compared with those obtained in colloidal solutions

“Chiclero’s Ulcer” Due to Leishmania mexicana in Travelers Returning from Central America: A Case Report and Review of the Literature

International audienceCutaneous leishmaniasis (CL) due to a New World species of Leishmania is increasingly seen among returning international travelers, and most cases arise from travel to Mexico, Central and South America. We described a case of CL in a women presenting a nonhealing ulceration under her right ear with slight increase of size of the left parotid gland under the skin lesion, evolving for 4 months. In her history of travel, she reported a ten-day stay in Mexico during the Christmas vacation in the Yucatan region with only half a day walking in the tropical forest. Diagnosis of CL due to Leishmania mexicana was done via PCR detection and sequencing from swab sampling of the lesion. The patient recovered without antiparasitic treatment. Clinicians should consider diagnosing Chiclero’s ulcer in patients returning from endemic areas such as Central America and Texas who present with chronic ulceration. A noninvasive sampling is sufficient for the PCR-based diagnosis of this disease

Microfabrication by two-photon lithography, and characterization, of SiO2/TiO2 based hybrid and ceramic microstructures

International audienceHigh resolution fabrication using two-photon lithography is extensively studied for a large range of materials, from polymer to inorganics. Hybrid materials including a sol-gel step have been developed since two decades to increase mechanical or optical properties in particular on silicon based materials. Among the metal oxide, few studies have been dedicated to titanium and, because of the high reactivity of titanium precursors, obtaining a resin with a high part of titanium is challenging. Indeed, resins for two-photon lithography have to be stable for the processing time and titanium precursors are more difficult to operate due to their higher reactivity and often require drastic working conditions in order to control the chemical processes. Here, we propose a method, working at ambient conditions, to print submicronic structures of organic-inorganic hybrids with a large proportion of titanium and ceramics using high resolution two-photon process. The material obtained and its evolution during the pyrolysis at 600°C and 1000°C are characterized. We show that TiO2/SiO2 based micro-ceramics can be obtained after the pyrolysis of the microstructures. The respective roles of the two chemical reactions involved in this lithography process, sol-gel condensation and radical photopolymerization, are highlighted

Nanostructured Objects designed to improve “NanoParticle Enhanced-LIBS” analysis

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Periodic nanoporous inorganic patterns directly made by self-ordering of cracks

International audienceSolution-processed inorganic nanoporous films are key components for the vast spectrum of applications ranging from dew harvesting to solar cells. Shaping them into complex architectures required for advanced functionality, often need time-consuming or expensive fabrication. In this work, we show how crack formation is harnessed to pattern porous inorganic films in a single step and without using lithography. We developed aqueous ink formulations that, in the presence of polymeric latexes, enable evaporation-induced, defect-free periodic arrays of cracks with tunable dimensions over several centimeters. The ink formulation strategy was generalized to more than ten inorganic materials including simple and binary porous oxide and metallic films covering a whole spectrum of properties including insulator, photocatalytic, electrocatalytic, conductive or electrochromic materials. Notably, this approach enables three-dimensional self-assembly of cracks by stacking several layers of different compositions, yielding periodic assemblies of polygonal shapes and Janus-type patterns. The crack patterned periodic arrays of nanoporous TiO2 diffract light, and are used as temperature-responsive diffraction grating sensors. More broadly, this method represents a unique example of self-assembly process leading to long-range order (over several cm) in a robust and controlled way

The quest for mixed-metal oxide precursors based on bismuth: synthesis and molecular structure of BiTi2(mu3-O)(mu-OPri)4(OPri)5 and [Bi2(mu-OPri)2(OPri)2(acac)2] (acac = acetylacetonate)

Various routes to mixed-metal Bi-Ti species were investigated. Various heterometallic alkoxides could be isolated by using hydrolysis reactions. The mixed-metal alkoxide BiTi2(mu(3)-O)(mu-OPri)(4)(OPri)(5) was obtained by reaction between titanium isopropoxide and a bismuth oxoisopropoxide formed in situ by controlled microhydrolysis and subsequent alcoholysis of Bi(OBut)(3). It was characterised by X-ray crystallography, H-1 NMR and Fourier-transform IR spectroscopy. The structure is based on an isosceles triangular framework with a central triply bridging oxo ligand. Bismuth is four-co-ordinate with a stereochemically active lone pair. The titanium atoms are six-co-ordinate with a severely distorted octahedral environment. Synthesis and characterisation of the bismuth-titanium ethoxides BiTi2O(OEt)(9) and Bi4Ti3O4(OEt)(16) were achieved, as well as their evaluation as oxide precursors. The latter leads, after complete hydrolysis and thermal treatment at 450 degrees C, to the pure crystalline Bi4Ti3O12 perovskite phase. The synthesis and structural characterisation of [Bi-2(mu-OPri)(2)(OPri)(2)-(eta(2)-acac)(2)](x) (acac = acetylacetonate) are also reported. The basic structural unit is a dimer in which the five-coordinated metals are linked by dissymmetrical Bi-OR bridges. Each beta-diketonate is chelating one metal. Chains of dimers run along the c axis via terminal semibridging isopropoxide ligands, ensuring six-co-ordination for the bismuth atoms

Symmetry loss of heptamethine cyanines: an example of dipole generation by ion-pairing effect

International audienceThe development of near-infrared dyes for third order nonlinear optical applications and particularly for optical power limiting at telecommunications wavelengths triggered the revival of old dyes like polymethine dyes featuring an odd number of carbon atoms. Currently numerous research endeavor is focused on the understanding of their spectroscopy in solution and in the solid state in close relationship with their electronic structure. In this context, the dramatic effect of the counter ion on the heptamethine optical properties was highlighted depending on the dissociating character of the media. The unusual consideration of this parameter allows us to explore the so-called "cyanine limit" and to finely tune the heptamethine absorption in view of future use as dopant in a material for optical limiting applications