Photochromic ormosil-phosphotungstate hybrid materials were prepared by immobilizing phosphotungstic acid, H 3 PW 12 O 40 , (HPW) in hybrid organic-inorganic ormosil matrices via sol-gel route, and the effect of addition of TiO 2 nanoparticles (NPs) on the photochromic response of HPW was studied. For measurement of the photochromic response and the bleaching kinetics, the resulting sol-gelderived ormosil-phosphotungstate hybrid materials with and without TiO 2 NPs were coated as thin films on glass substrate by dip coating. The hybrid films were characterized by scanning electron microscopy, Fourier transform infrared absorption spectroscopy, Raman spectroscopy and X-ray fluorescence spectroscopy. The addition of small amounts of TiO 2 was found to increase the photochromic response of the hybrid materials by as much as 277 % which is attributed to a possible interfacial electron transfer from the photoexcited TiO 2 to HPW. These highly UV-sensitive coatings can find useful applications in UV dosimeters and smart windows.Electronic supplementary material The online version of this article (
In this study, we sought to evaluate the influence of cigarette smoke and pH cycling on the chemical composition and surface/cross-sectional enamel microhardness. A total of 40 dental blocks obtained from bovine incisors were divided into four groups (n=10): no treatment (control); exposure to cigarette smoke (CS); exposure to pH cycling (PC); and exposure to cigarette smoke and pH cycling (CS-PC). The samples were analyzed by synchrotron radiation micro X-ray fluorescence, bench mode X-ray fluorescence, as well as surface microhardness (SMH) and cross-sectional microhardness (CSMH) testing. The SMH results were submitted to analysis of variance (ANOVA) and Tukey’s test. The CSMH results were evaluated using split-plot ANOVA and Tukey’s test. A high amount of Cd and Pb and traces of Ni and As were observed in enamel and dentin after exposure to cigarette smoke (CS and CS-PC). The SMH and CSMH of CS were statistically higher when compared with the control. The PC and CS-PC showed lower SMH and CSMH. We conclude that exposure to cigarette smoke promoted heavy metal deposition in enamel/dentin. In addition, it increased the enamel microhardness but did not promote a protective effect on the in vitro development of caries. The clinical significance of this work is that there is significant bioaccumulation of heavy metals from cigarette smoke on the surface and in the enamel and dentin.
It was possible to identify and detect Ti dopant in the range of tens of mg.Kg -1 by means of Grazing Incidence X-Ray Fluorescence (GIXRF) analysis assisted by Synchrotron Radiation. In addition, Microscopic X-ray Fluorescence analysis (μ-XRF) assisted by Synchrotron Radiation enabled the identification of spatial distributions of Titanium and Zinc within ormosils. Since these XRF analyses did not employ certified materials for validation, standards were prepared at our laboratory following a similar protocol to that used to prepare the samples. The semi-quantification method based on fundamental parameters was also used, which demonstrated be very useful and efficient. X-ray fluorescence results were validated by those obtained from Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Instrumental Neutron Activation Analysis (INAA). The different methods of analysis employed (μ-XRF GIXRF, EDXRF, ICP-OES, AAS) were effective regarding precision and accuracy in Tungsten and Zinc quantification. In the case of Titanium, however, only μ-XRF and ICP-OES results could be taken into account. Therefore, there is the need for additional analytical methods to validate concentration results for this element in ormosils. ICP-OES and INAA proved to be reference methods for results obtained through XRF (Laboratory and assisted by Synchrotron Radiation) for our materials.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.