Cation binding by thiacalixthianthrenes

International audienceThe complexing properties of a thiacalix[2]thianthrene 1 and its disulfoxide derivative 2 toward alkali metal, alkaline earth metal, some transition metal and some heavy metal cations have been investigated in acetonitrile by means of UV spectrophotometry. At the concentrations suited to this technique, complexation of the alkali metal cations by the sulfoxide but not the thiacalixthianthrene was detectable, whereas the converse was true for both transition metal and lanthanide cations. Complexation of the alkaline earth cations was not detectable. The strongest binding observed was that of Hg(II) to ligand 1 but in no case was complexation sufficiently strong for either ligand to function as a useful metal ion extractant. Graphical Abstract The complexing properties of a thiacalix[2]thianthrene 1 and its disulfoxide derivative 2 toward alkali metal, alkaline earth metal, some transition metal and some heavy metal cations have been investigated in acetonitrile by means of UV spectrophotometry. At the concentrations suited to this technique, complexation of the alkali metal cations by the sulfoxide but not the thiacalixthianthrene was detectable, whereas the converse was true for both transition metal and lanthanide cations. Complexation of the alkaline earth cations was not detectable. The strongest binding observed was that of Hg(II) to ligand 1 but in no case was complexation sufficiently strong for either ligand to function as a useful metal ion extractant

Photoluminescence spectra and quantum yields of gold nanosphere monomers and dimers in aqueous suspension

International audienceThe intrinsic one-photon excited photoluminescence (PL) of dimers and monomers of gold spheres suspended in water was studied by combining photon time-of-flight spectroscopy (PTOFS) and light scattering fluctuation correlation spectroscopy (LS-FCS). The samples are obtained by precisely controlling the dimerization of aqueous colloidal systems based on 50 and 80 nm gold nanospheres. The combination of PTOFS and LS-FCS enables the separate spectroscopic study of monomers and dimers even though they exist as a mixture in the samples. PL emission spectra and diffusional dynamics are obtained simultaneously through measurement at the single particle level. The PL spectra resemble the light scattering spectra, indicating the plasmon-assisted character of the photoluminescence process. We determine the intrinsic PL quantum yields of the dimers and the monomers. It is often not possible to measure such very low quantum yields in solution using conventional techniques, and we show here that PTOFS provides access to this information. The quantum yield of the dimers was found to be of same order of magnitude as that of the monomers, of the order of 10 À6 , which indicates that the interparticle 'electromagnetic hot-spots' do not play a major role in the luminescence emission mechanism in such plasmonic molecules

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

Gold nanoparticle shape dependence of colloidal stability domains

International audienceControlling the spatial arrangement of plasmonic nanoparticles is of particular interest to utilize inter-particle plasmonic coupling, which allows changing their optical properties. For bottom-up approaches, colloidal nanoparticles are interesting building blocks to generate more complex structures via controlled self-assembly using the destabilization of colloidal particles. For plasmonic noble metal nanoparticles, cationic surfactants, such as CTAB, are widely used in synthesis, both as shaping and stabilizing agents. In such a context, understanding and predicting the colloidal stability of a system solely composed of AuNPs and CTAB is fundamentally crucial. Here, we tried to rationalize the particle behavior by reporting the stability diagrams of colloidal gold nanostructures taking into account parameters such as the size, shape, and CTAB/AuNP concentration. We found that the overall stability was dependent on the shape of the nanoparticles, with the presence of sharp tips being the source of instability. For all morphologies evaluated here, a metastable area was systematically observed, in which the system aggregated in a controlled way while maintaining the colloidal stability. Combining different strategies with the help of transmission electron microscopy, the behavior of the system in the different zones of the diagrams was addressed. Finally, by controlling the experimental conditions with the previously obtained diagrams, we were able to obtain linear structures with a rather good control over the number of particles participating in the assembly while maintaining good colloidal stability.

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

TiO2/SiO2 porous composite thin films: Role of TiO2 areal loading and modification with gold nanospheres on the photocatalytic activity

International audienceThe aim of the work was to study photocatalytic activity of composite TiO2/Au/SiO2 thin films. Coatings were prepared using sol-gel technique. Physicochemical parameters of coatings were characterized using UV–vis spectrometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometry (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), ellipsometry, tactile measurements, goniometry and diffuse reflectance measurements. The photocatalytic activity of the films was tested in batch mode using aqueous solution of formic acid. Changes of formic acid concentration were determined by means of high pressure liquid chromatography (HPLC). Increase of initial degradation rate of formic acid was detected for TiO2/Au/SiO2 films with gold nanoparticle’s load 0.5 wt.% and 1.25 wt.%. However, deeper insights using more detailed characterization of these coatings demonstrated that the improvement of the photocatalytic activity is more probably attributed to an increase in the areal loading of TiO2

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

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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