Search

This review is an extensive collection of the latest literature describing the current knowledge about nanohydroxyapatite in a comprehensive way. These are hydroxyapatite particles with a size below 100 nm. Due to their size, the surface area to mass ratio of the particles increases. They are widely used in medicine due to their high potential in regenerative medicine, as a carrier of various substances, e.g., in targeted therapy. The aim of this article is to present the biological and physicochemical properties as well as the use of nanohydroxyapatite in modern medicine. Due to the potential of nanohydroxyapatite in medicine, further research is needed. [ABSTRACT FROM AUTHOR]

Fluoride varnishes, both the first and the second generations, are effective in inhibiting caries, especially in children and adolescents, by reducing it on average by 43% for permanent teeth and 37% for deciduous teeth. The aim of this study was to evaluate the dynamics of in vitro fluoride ion release from first- (Duraphat) and second-generation (MI Varnish and Embrace Varnish) fluoride varnishes and the impact of the type of varnish, the time from its application and the pH of the environment on this process. Materials and methods: The test material (90 specimens), prepared from extracted human teeth, were divided into nine groups of 10 specimens each. Measured amounts of the examined varnishes were applied onto specimens and the levels of fluoride release were assessed at the baseline and after 1, 2, 24, 48 and 168 h from the application with the use of an ion-specific electrode. The specimens were immersed into artificial saliva with pH adjusted to 4, 5 and 7. The highest cumulative release of fluoride was obtained by MI Varnish (11.52 ppm/mg), regardless of the pH of the environment, whereas the lowest released fluoride concentration was achieved by Embrace Varnish (4.82 ppm/mg). In the acidic environment, the release of fluoride was significantly higher than in the neutral environment for all investigated varnishes, with no change in the overall fluoride release profile and with maximum fluoride release in the first two hours after application. The findings of this study indicate that all examined fluoride varnishes released the maximum amount of fluoride within the first hours after application and that it was related to the acidity of the immersion medium. [ABSTRACT FROM AUTHOR]

Coordination compounds of lanthanides NEt4[NaLn2L4(H2O)], Na[NaLn2L4(H2O)]·2H2O (Ln = La3+, Nd3+) with the bis-chelating carbacylamidophosphate ligand tetramethyl N,N′-(2,2,3,3,4,4-hexafluoro-1,5-dioxopentane-1,5-diyl)bis(phosphoramidate) (H2L) were obtained for the first time via reactions of Na2L with lanthanide nitrates. The complexes were characterized by IR and NMR spectroscopy and laser desorption/ionization mass spectrometry. From X-ray diffraction analysis, it was established that the complex anions in the obtained compounds have a structure of a quadruple-stranded helicate, which encapsulates a sodium cation and a molecule of water into the negatively charged environment of the ligand fluorine and carbonyl oxygen atoms. Upon excitation by the 266 nm harmonic line of the Nd:YAG pulsed laser, the NEt4[NaNd2L4(H2O)] complex exhibits IR-emission at 300 and 77 K with the 4F3/2 emission lifetime of 2 μs. [ABSTRACT FROM AUTHOR]

In this study, it has been presented the influence of pH conditions on the evolution of the size, morphology and spectroscopic properties of yttrium orthovanadate during synthesis. A thorough research on the spectroscopic properties was performed. A series of highly crystalline 1 mol% Eu3+:YVO4 has been synthesized via the co-precipitation method. In addition, to improve the crystallinity, the materials were heat-treated at 800 °C, and the structural and morphological properties of the particles were studied using XRD (X-ray powder diffraction) and SEM (Scanning Electron Microscopy) techniques. In order to investigate the spectroscopic properties of 1 mol% Eu3+:YVO4, emission spectra and luminescence kinetics were measured. It was found that alkaline pH manifests in smaller particles compared to acidic pH conditions. In addition, superior spectroscopic properties were observed in materials obtained in alkaline pH. [ABSTRACT FROM AUTHOR]

Rb3Y2(PO4)3 and Rb3La(PO4)2, undoped and doped with Eu3+ ions, were synthesised either by the Pechini method or solid state reaction. They were characterised by thermoanalytical methods, X-ray diffraction, IR and Raman spectroscopy as well as optical techniques. It was stated that Pechini and solid state reaction methods give the compounds with the same structure. The structural data result in the P21/m space group with Z = 2 and a = 9.78 Å, b = 5.76 Å and c = 7.77 Å cell parameters for Rb3La(PO4)2 and cubic symmetry I21/3 with a = 16.87 Å and Z = 16 for Rb3Yb2(PO4)3. In Rb3La(PO4)2 the reversible β/α phase transition is observed in the 960–1070 °C temperature range. The lifetime of the 5D0 excited state measured at 77 K is about 4 and 2 ms for Rb3La(PO4)2 and Rb3Y2(PO4)3, respectively. [ABSTRACT FROM AUTHOR]

The β-KYP2O7 powders doped with Sm3+, Tb3+ and Dy3+ were obtained using a one-step urea-assisted combustion method. Their structural properties were characterized by X-ray diffraction (XRD) whereas spectroscopic properties like excitation, emission and luminescence kinetics were investigated at room temperature. β-KYP2O7 doped with Sm3+ and Dy3+ showed concentration quenching above 2 mol% of dopants whereas Tb3+ containing materials could be doped with higher concentrations. The main mechanisms of concentration quenching were identified as dipole–dipole for Sm3+ and Dy3+. Both dopants due to the abundant energy levels are strongly prone to quenching due to the non-radiative CR process whose efficiency strongly increases with the concentration of optically active ions. In the case of Tb3+ emission from both 5D3 and 5D4 levels was recorded. The 5D3 level vastly depopulates due to the CR process upon increase of the Tb3+ content whereas the slight 5D4 emission remains stable up to 5 mol%. [ABSTRACT FROM AUTHOR]

KYP2O7 powders doped with Eu3+ were obtained for the first time by a one-step urea-assisted combustion method. Detailed structural properties were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and X-ray fluorescence (EDX). Spectroscopic properties like excitation, emission and luminescence kinetics were investigated in the temperature range of 30–550 °C. The KYP2O7 doped with Eu3+ phosphor has a broad and intense absorption band centered at 213 nm, an absolute quantum yield of up to 62% and a luminescence quenching temperature of T0.5 = 400 °C. The thermal behavior analysis of the luminescence shows that non-radiative internal losses are the main mechanism responsible for quenching of the luminescence. [ABSTRACT FROM AUTHOR]