Conductive carbon paint: An efficient way to electrodeposit metallic nanowires by using porous membranes.

The present work demonstrates that conductive carbon paint, used for sample preparation in electron microscopy, can be a more straightforward and as-effective substitute for the metallic layer deposition usually used for the electrodeposition of metallic nanowires within porous membranes. AFM images demonstrated the good surface quality of the carbon layer. Raman spectroscopy confirmed the high crystallinity of carbon and high density of π-electrons. The electrical conductivity of the carbon layer was estimated using the linear sweep voltammetry technique. This new cathode was employed to grow continuous (Ni) and composition-modulated (Ni/Cu) nanowires within alumina templates, starting from aqueous solutions of Ni2+ and Cu2+ mixed salts. The obtention of metallic copper and nickel, and their separation can be readily observed by scanning electron microscopy and elemental mapping by EDS.

Dentin Staining Caused by Nano-silver Fluoride: A Comparative Study.

CLINICAL RELEVANCE: The new formulations of nano-silver fluoride caused less dentin staining than the already available commercial agents 35% silver fluoride and silver diamine fluoride at 30% and 38%. SUMMARY: The objective of this study was to evaluate the dentin staining potential of nano-silver fluoride (NSF 600 and 1500 ppm) compared with the following commercially available cariostatic agents: Advantage Arrest (Elevate Oral Care, West Palm Beach, FL, USA), Riva Star (SDI, Victoria, Australia), and Cariestop (Biodinâmica, Paraná, Brazil). Seventy-five extracted human molars were sectioned at the cementoenamel junction, and the occlusal enamel was removed for exposure of coronary dentin. The samples were divided among the five agents tested (n=15). The dentin staining (ΔE/ΔL) was analyzed with a digital spectrophotometer (VITA Easyshade, VITA Zahnfabrik, Bad Säckingen, Germany) at three different time points (before application, after two weeks, and after four weeks). Photographic images were also performed. The Kruskal-Wallis and Mann-Whitney tests compared the mean ΔE and ΔL values between groups. The NSF 600 and 1500 ppm resulted in the smallest color change (ΔE=1.02 and 1.53) and dentin staining after four weeks (ΔL=-0.76 and -1.2). The new formulations differed significantly from the commercial cariostatic agents (p<0.001). NSF might be an alternative to silver diamine fluoride since it does not compromise esthetics.

New methodology for obtaining CdTe quantum dots by using ultrasound.

Luminescent CdTe quantum dots (Qdots) have been produced at few minutes by using a new, simple and fast methodology in an aqueous medium by using ultrasound irradiation to accelerate the process of tellurium reduction. The structural and optical properties were characterized by TEM, XRD, absorption and fluorescence spectrocopy. The produced Qdots are in a strong quantum confinement regime and have only one fluorescence band. Moreover, the nanoparticles seem to be monodispersed, which is in accordance with the fluorescence results. We have developed a simple route for preparing monodispersed CdTe Qdots in an aqueous media. The use of ultrasound allows the morphology to be better controlled and the surfaces defects of Qdots to be reduced.

High-order nonlinearity of silica-gold nanoshells in chloroform at 1560 nm.

The nonlinear response of silica--gold nanoshells (SGNs) in chloroform was studied using laser pulses of 65 fs at 1560 nm. The experiments were performed using the thermally managed Z--scan technique that allows measurements of the electronic contribution for the nonlinear response, free from thermal influence. The results were analyzed using an analytical approach based on the quasi--static approximation that allowed extraction of the nonlinear susceptibility of a SGN from the data. High third--order susceptibility, χsh((3)) = - 1.5 x 10(-11) m(2)/V(2), approximately four orders of magnitude larger than for gold nanospheres in the visible, and large fifth--order susceptibility, χsh((5)) = - 1.4 x 10(-24) m(4)/V(4), were obtained. The present results offers new perspectives for nonlinear plasmonics in the near--infrared.