scholarly journals Colour and chemical stability of bismuth oxide in dental materials with solutions used in routine clinical practice

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0240634
Author(s):  
Josette Camilleri ◽  
Joseph Borg ◽  
Denis Damidot ◽  
Enrico Salvadori ◽  
Peter Pilecki ◽  
...  
Keyword(s):  
Dental Materials ◽  
Colour Change ◽  
Clinical Findings ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
Tooth Discoloration ◽  
Contrast Exposure ◽  
New Compounds ◽  
Electron Paramagnetic ◽  
Sodium Bismuthate

Bismuth(III) oxide is included as a radio-opacifier in dental materials, including hydraulic silicate cements, the material of choice for several endodontic procedures. It has been implicated in tooth discoloration after contact with endodontic irrigants, in particular NaOCl solution, To date, there has been no work on the chemistry: all reports have been of clinical findings only. The purpose now was to report the reactions leading to colour change from Bi2O3 in contact with solutions used in routine endodontic practice. Ten-gram portions of Bi2O3 were immersed in either water, NaOH, NaCl, NaOCl or HCl solution, either in the dark or exposed to visible light, and samples retrieved at 1, 4, 12 and 24 weeks. After washing, these were exposed to either added CO2 or not, for 1 week while drying, and under the same dark or light conditions. Changes in appearance were monitored by photography and colour measurement, and chemically by X-ray diffraction and Fourier-transform infrared spectroscopy. 24-week material was studied using electron paramagnetic resonance and Raman spectroscopy; NaOCl-treated material was also examined by scanning electron microscopy. With water, NaCl and NaOH, bismuth subcarbonate was formed. With or without added carbon dioxide, discoloration occurred from pale yellow to light brown when exposed to light, and to a lesser extent in the dark, intensifying with time. In contrast, exposure to NaOCl rapidly formed a dark brown-black sodium bismuthate. With HCl, white BiOCl was formed. Bi2O3 is not at all inert in this context as is commonly believed, denying its principle of use. Previously unreported solution-mediated reaction occurs readily even in water and NaCl solution, forming new compounds that discolour. In contact with NaOCl sodium bismuthate is formed; severe darkening occurs rapidly. The reactivity is such that Bi2O3 is not indicated for dental materials and should be withdrawn from use.

scholarly journals Electrospun Nanosystems Based on PHBV and ZnO for Ecological Food Packaging

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2123
Author(s):  
Maria Râpă ◽  
Maria Stefan ◽  
Paula Popa ◽  
Dana Toloman ◽  
Cristian Leostean ◽  
...  
Keyword(s):  
Food Packaging ◽  
Spin Trapping ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
Hno3 Solution ◽  
X Ray ◽  
Trapping Method ◽  
Ft Ir ◽  
Doped Zno ◽  
Electron Paramagnetic

The electrospun nanosystems containing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and 1 wt% Fe doped ZnO nanoparticles (NPs) (with the content of dopant in the range of 0–1 wt% Fe) deposited onto polylactic acid (PLA) film were prepared for food packaging application. They were investigated by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), antimicrobial analysis, and X-ray photoelectron spectrometry (XPS) techniques. Migration studies conducted in acetic acid 3% (wt/wt) and ethanol 10% (v/v) food simulants as well as by the use of treated ashes with 3% HNO3 solution reveal that the migration of Zn and Fe falls into the specific limits imposed by the legislation in force. Results indicated that the PLA/PHBV/ZnO:Fex electrospun nanosystems exhibit excellent antibacterial activity against the Pseudomonas aeruginosa (ATCC-27853) due to the generation of a larger amount of perhydroxyl (˙OOH) radicals as assessed using electron paramagnetic resonance (EPR) spectroscopy coupled with a spin trapping method.

Fabrication, characterization and magnetic properties of Na-doped ZnO nanorods

2016 ◽  
Vol 09 (03) ◽  
pp. 1650039 ◽  
Author(s):  
Jingyuan Piao ◽  
Li-Ting Tseng ◽  
Kiyonori Suzuki ◽  
Jiabao Yi
Keyword(s):  
Magnetic Measurements ◽  
Zno Nanorods ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Shallow Donors ◽  
Na Doping ◽  
Transmission Electron ◽  
Doped Zno ◽  
Electron Paramagnetic

Na-doped ZnO nanorods have been fabricated through a hydrothermal method. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses indicate that the d spacing of ZnO increases with increasing doping concentration, suggesting the effective incorporation of dopant Na in the samples. Electron paramagnetic resonance (EPR) measurements indicate that there are shallow donors in pure ZnO samples and the shallow donors are strongly prohibited by Na doping. In addition, the resonance at g = 2.005 suggests the formation of Zn vacancies. Magnetic measurements indicate that pure ZnO is paramagnetic and Na doping leads to ferromagnetism at room temperature. Moreover, 0.5% Na-doped ZnO nanorods exhibits the largest saturation magnetization.

Structural and Magnetic Properties of the Zn-Mn-O System

2007 ◽  
Vol 555 ◽  
pp. 95-100
Author(s):  
D. Milivojević ◽  
Jovan Blanuša ◽  
V. Spasojević ◽  
V. Kusigerski ◽  
B. Babić-Stojić
Keyword(s):  
Room Temperature Ferromagnetism ◽  
Manganese Concentration ◽  
Ferromagnetic Phase ◽  
X Ray Diffraction ◽  
Reaction Route ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Mn Oxide ◽  
Different Temperatures ◽  
Electron Paramagnetic

Zn-Mn-O semiconductor crystallites with nominal manganese concentration x = 0.01, 0.02, 0.04 and 0.10 were synthesized by a solid state reaction route using oxalate precursors. Thermal treatment procedure was carried out in air at different temperatures in the range 400 - 900°C. The samples were investigated by X-ray diffraction, magnetization measurements and electron paramagnetic resonance. X-ray analysis reveals that dominant crystal phase in the Zn-Mn-O system corresponds to the wurtzite structure of ZnO. Room temperature ferromagnetism is observed in the Zn-Mn-O samples with lower manganese concentration, x ≤ 0.04, thermally treated at low temperature (500°C). Saturation magnetization in the sample with x = 0.01 is found to be 0.05 μB/Mn. The ferromagnetic phase seems to be developed by Zn diffusion into Mn-oxide grains.

Electronic and Structural Requisites for Catalytic Activity in Copper-Ruthenium Catalysts

1994 ◽  
Vol 368 ◽  
Author(s):  
M. Malaty ◽  
D. Singh ◽  
Noel Vadel ◽  
M.L. Gomez ◽  
M. Palmieri ◽  
...  
Keyword(s):  
Structural Changes ◽  
Supported Catalyst ◽  
Ruthenium Catalysts ◽  
Molecular Techniques ◽  
Oxidation Reactions ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
Different Temperatures ◽  
Electron Paramagnetic ◽  
Reduced Forms

ABSTRACTA system made by combining two non-alloying metals, ruthenium and copper, using alumina as a support was studied. This bimetallic supported catalyst has been used mainly in hydrogenolysis, dehydrogenation and oxidation reactions of hydrocarbons. The samples were characterized by Electron Paramagnetic Resonance Spectrometry (EPR) and X-ray Diffraction (XRD). These two molecular techniques are ideal for studying the electronic and structural changes of the samples at different temperatures and concentrations. Catalytic reactions were performed using the catalyst in the reduced and non-reduced forms on a series of catalytic hydrogenations. A correlation between the electronic, structural and catalytic properties has been made. A correlation of catalytic process to molecular phenomena has yield a better understanding of the catalytic site.

Dinuclear Cu(II) 1,2,3-Triazole-Bridged Complex with Ferromagnetic Coupling

2013 ◽  
Vol 66 (9) ◽  
pp. 1029 ◽  
Author(s):  
Shi-Qiang Bai ◽  
Lu Jiang ◽  
Jing-Lin Zuo ◽  
Chun-Hua Yan ◽  
T. S. Andy Hor
Keyword(s):  
Resonance Spectrum ◽  
Magnetic Measurements ◽  
Ferromagnetic Coupling ◽  
X Ray Diffraction ◽  
Asymmetric Mode ◽  
Paramagnetic Resonance ◽  
Ferromagnetic Interaction ◽  
X Ray ◽  
Electron Paramagnetic ◽  
Weak Ferromagnetic

A new dinuclear Cu(ii) complex [Cu2Cl4(L1)2] (1) (L1 = 1-(2-picolyl)-4-hexyl-1H-1,2,3-triazole) has been synthesised and characterised by single-crystal X-ray diffraction (XRD) and powder XRD, thermogravimetric analysis, electron paramagnetic resonance spectrum, photoluminescence, and magnetic measurements. Complex 1 shows double 1,2,3-triazoles bridging the dinuclear Cu2N4 moiety, in which the bridging N=N bond indicates basal-apical asymmetric mode with 112.6° torsion angle of Cu–N=N–Cu. Different from most azole-bridged dinuclear Cu(ii) with antiferromagnetic couplings, complex 1 shows an intramolecular weak ferromagnetic interaction (J = 0.91 cm–1).

Probing the Structure and Visible Light Photocatalytic Mechanism of LaVO4/TiO2 Composite Using XRD, BET, and EPR

2012 ◽  
Vol 217-219 ◽  
pp. 737-740
Author(s):  
Han Jie Huang
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Visible Light ◽  
Gas Phase ◽  
Spin Trapping ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Photocatalytic Mechanism ◽  
Electron Paramagnetic ◽  
Visible Light Photocatalytic

In this work, a visible light-induced LaVO4/TiO2 composite has been characterized by powder X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and spin-trapping electron paramagnetic resonance (EPR) to reveal the structure and visible light photocatalytic mechanism for the decompostion of benzene in gas-phase. Based on the experimental results, a visible light-induced photochemical processes on LaVO4/TiO2 are proposed and elucidated.

scholarly journals Stable Helicene Radicals: Synthesis, Structure, Physical Properties, and Photocatalysis

2020 ◽  
Author(s):  
Aslam Shaikh ◽  
Md Mubarak Hossain ◽  
Jules Moutet ◽  
Jose Veleta ◽  
Jan Bloch ◽  
...  
Keyword(s):  
Density Functional ◽  
Chemical Reduction ◽  
Organic Radicals ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
Functional Theory ◽  
Neutral Radical ◽  
Vis Spectroscopy ◽  
Electron Paramagnetic ◽  
Helical Molecules

Abstract Stable organic radicals have gained considerable attention in the fields of catalysis and material sciences. In particular, helical molecules are of great interest in the development and application of novel organic radicals in optoelectronic and spintronic materials. Here we report the syntheses of highly stable neutral quinolinoacridine radicals by chemical reduction of their quinolinoacridinium cation analogs. The crystal structures of these [4]helicene radicals were determined by X-ray diffraction. Electron paramagnetic resonance (EPR) measurements, supported by density functional theory (DFT) calculations, indicate that the unpaired electron is mostly localized, showing more than 40% of spin density located at the central carbon of the [4]helicene radicals. Quantitative conversion from neutral radical to cation is observed upon exposure to air, monitored via UV-vis spectroscopy. The successful photoreductive dehalogenation of aryl halides occurs in the presence of 10 mol% of [4]helicene radical under blue light.

scholarly journals X-Ray Diffraction, Electron Paramagnetic Resonance and Optical Absorption Study of Bauxite

2014 ◽  
Vol 02 (02) ◽  
pp. 114-120
Author(s):  
Tanguturi Ravindra Reddy ◽  
Krishnan Thyagarajan ◽  
Ovidio Almanza Montero ◽  
Sanapa Reddy Lakshmi Reddy ◽  
Tamio Endo
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Optical Absorption ◽  
Absorption Study ◽  
X Ray Diffraction ◽  
Optical Absorption Study ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Diffraction Electron ◽  
Electron Paramagnetic
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