Enabling Broadband Solar-Blind UV Photodetection by a Rare-Earth Doped Oxyfluoride Transparent Glass-Ceramic.

Oxyfluoride transparent glass-ceramics (GC) are widely used as the matrix for rare-earth (RE) ions due to their unique properties such as low phonon energy, high transmittance, and high solubility for RE ions. Tb3+ doped oxyfluoride glasses exhibit a large absorption cross section for ultraviolet (UV) excitation, high stability, high photoluminescence quantum efficiency, and sensitive spectral conversion characteristics, making them promising candidate materials for use as the spectral converter in UV photodetectors. Herein, a Tb3+ doped oxyfluoride GC is developed by using the melt-quenching method, and the microstructure and optical properties of the GC sample are carefully investigated. By combining with a Si-based photo-resistor,a solar-blind UV detector is fabricated, which exhibits a significant photoelectric response with a broad detection range from 188 to 400 nm. The results indicate that the designed UV photodetector is of great significance for the development of solar-blind UV detectors.

Mid-Infrared Luminescence of the High Stability Perovskite CsPb1-xErxBr3-ZrF4-BaF2-LaF3-AlF3-NaF Fluoride Glass.

Perovskites have been studied because of their adjustable wavelength range, high color purity, and wide color gamut. However, they still face some problems such as poor stability and insufficient infrared luminescence. The perovskite glass can improve the stability and luminescence properties of the perovskite. In this paper, a highly stable CsPb1-xErxBr3-ZBLAN fluoride glass with mid-infrared and visible light emission was prepared. The ZBLAN fluoride glass has good inertness, which can improve the stability of the CsPb1-xErxBr3 perovskite. The CsPb1-xErxBr3-ZBLAN fluoride glass can prevent the perovskite from being destroyed by water, oxygen, and laser. The Er3+ replaces Pb2+ to bond with Br- to become the luminescent center of the CsPb1-xErxBr3-ZBLAN perovskite glass, which extends the luminescence to the mid-infrared region. In addition, its luminescent intensity is significantly higher than those of the ZBLAN-Er glass and CsPb1-xErxBr3 perovskite. After irradiation with a 365 nm UV lamp for 13 h, the luminescence intensity of the CsPb1-xErxBr3-ZBLAN perovskite glass decreases only by 10%. The EDS spectrum shows that the elements of the CsPb1-xErxBr3 perovskite are uniformly distributed in the glass matrix. The X-ray diffraction spectrum shows that the sample has both the CsPb1-xErxBr3 perovskite phase and the glass phase. This indicates that CsPb1-xErxBr3 is well crystallized in the ZBLAN glass matrix. The three parameters calculated by the Judd-Ofelt theory show that the CsPb1-xErxBr3 perovskite can increase the covalency and asymmetry around the rare earth ion Er3+. The transmission electron microscope can clearly see the morphological structure of the CsPb1-xErxBr3 perovskite in the ZBLAN glass matrix. The infrared Fourier transform spectroscopy shows that the sample has lower phonon energy. This proves that the sample has good infrared luminescence characteristics. Finally, the visible and infrared light sources were prepared. Under the irradiation of the 365 nm ultraviolet lamp and 980 nm laser, the perovskite glass produces green light and infrared emission.

Evaluation of antibacterial and cytocompatible properties of multiple-ion releasing zinc-fluoride glass nanoparticles.

Zinc-fluoride glass nanoparticles (Zinc-F) release several ions, such as fluoride, zinc and calcium ions, through acid-base reactions. The aim of this study was to evaluate the antibacterial and cytotoxic properties of Zinc-F. Antibacterial tests showed that a Zinc-F eluting solution significantly reduced the turbidity and colony-forming units of Streptococcus mutans and Actinomyces naeslundii, compared to that of calcium-fluoroaluminosilicate glass nanoparticles without zinc ions. In live/dead staining, Zinc-F eluate significantly decreased green-stained bacterial cells, indicating live cells, compared with the control (no application). Human dentin coated with Zinc-F showed suppressed S. mutans and A. naeslundii biofilm formation. Additionally, Zinc-F eluate showed low cytotoxic effects in osteoblastic and fibroblastic cells. Therefore, our findings suggested that Zinc-F exhibits antibacterial and biocompatible properties through multiple-ion release.

The effect of annealing on optical transmittance and structure of ZLANI fluorozirconate glass thin films.

We report the effect of thermal annealing on structure, composition, optical transmittance and thickness of a novel fluorozirconate glass (ZLANI) containing Zr, La, Al, Na and In fluorides. In this work, pulsed laser deposition was used to grow thin films of ZLANI, and thermal annealing at different temperatures was performed on the films. Annealing did not change the composition, but a clear structural evolution of the ZLANI glass was observed by transmission electron microscopy (TEM), showing that we can control microstructure independent of composition. An increase in transmittance after the film was subject to a 100 °C thermal anneal was ascribed to the removal of defects and structural relaxation in the amorphous state. Following an anneal of 200 °C, the transmittance decreases due to heterogeneous formation of crystalline nuclei and changes in the local bonding. After the final annealing at 300 °C, a wider-scale crystallization occurred, with some major crystal phases formed as Zr2F8(H2O)6 and ZrO2, which alters the shape of the transmittance curve. The crystalline content of the crystal phases that form in the annealed films was quantified using hollow cone dark field TEM imaging. The 100 °C or 200 °C annealing decreases the film thickness by inducing structural relaxation and densification of the amorphous films, while the thickness increase of the 300 °C annealed film resulted from the formed large crystals. These results provide insights for the design of multilayer nanocomposites with a ZLANI glass matrix, which have potential applications as up-/down-conversion luminescent materials and X-ray storage phosphors.

Experimental Investigation of Actively Q-Switched Er3+:ZBLAN Fiber Laser Operating at around 2.8 µm.

A diode-pumped Q-switched Er3+:ZBLAN double-clad, single-transverse mode fiber laser is practically realized. The Q-switched laser characteristics as a function of pump power, repetition rate, and fiber length are experimentally investigated. The results obtained show that the Q-switched operation with 46 µJ pulse energy, 56 ns long pulses, and 0.821 kW peak power is achieved at a pulse repetition rate of 10 kHz. To the best of our knowledge, this is the highest-ever demonstrated peak power emitted from an actively Q-switched, single-transverse mode Er3+:ZBLAN fiber laser operating near 2.8 µm.

Ba4YZr3F23 and Ba4LnZr3F23: a new noncentrosymmetric potential host structure type for optical devices.

The first ternary BaF2-Ln(Y)F3-ZrF4 phases crystallizing near the composition range of fluoride glasses, namely Ba4YZr3F23 (barium yttrium fluoridozirconate) and isotypic Ba4LnZr3F23 (Ln = Yb, Er and Nd), have been synthesized. The crystal structure of Ba4YZr3F23 cannot be correctly determined in the centrosymmetric space group Pnma (R1 = 0.09); it is preferably described in the noncentrosymmetric space group Pn21a (R1 = 0.028). All cations are located at y = 0.25-0.29 and 0.75-0.79. This new structure type is formed by infinite {[YZr3F23]8-}n columns associating, along [001], YF9 tricapped trigonal prisms, ZrF8 dodecahedra and ZrF7 polyhedra. These columns are interconnected via BaF10+1 and BaF12 irregular polyhedra.

Flow injection analysis as a tool for enhancing oceanographic nutrient measurements--a review.

Macronutrient elements (C, N and P) and micronutrient elements (Fe, Co, Cu, Zn and Mn) are widely measured in their various physico-chemical forms in open ocean, shelf sea, coastal and estuarine waters. These measurements help to elucidate the biogeochemical cycling of these elements in marine waters and highlight the ecological and socio-economic importance of the oceans. Due to the dynamic nature of marine waters in terms of chemical, biological and physical processes, it is advantageous to make these measurements in situ and in this regard flow injection analysis (FIA) provides a suitable shipboard platform. This review, therefore, discusses the role of FIA in the determination of macro- and micro-nutrient elements, with an emphasis on manifold design and detection strategies for the reliable shipboard determination of specific nutrient species. The application of various FIA manifolds to oceanographic nutrient determinations is discussed, with an emphasis on sensitivity, selectivity, high throughput analysis and suitability for underway analysis and depth profiles. Strategies for enhancing sensitivity and minimizing matrix effects, e.g. refractive index (schlieren) effects and the important role of uncertainty budgets in underpinning method validation and data quality are discussed in some detail.

Fluoride in pit and fissure sealants: is it a feasible combination? / Flúor em selantes de cicatrículas e fissuras: uma combinação viável?

Dental sealants work on the principle of blocking caries susceptible pits and fissures of teeth thus rendering them caries resistant. Fluoride is another agent that is effective in reducing dental caries. However added benefits of fluoride can be achieved through its topical application. These effects can further be amplified by extended exposure of tooth surface to fluoride releasing agents. Thus the concept of addition of fluoride to pit and fissure sealants was conceived. Until now two methods of fluoride incorporation in pit and fissure sealants have been formulated. First method employs addition of soluble fluoride salts to the unpolymerized resin. Second system of fluoride incorporation uses an organic fluoride compound that can be chemically bound to resin. But the mechanism of fluoride release from fluoridated fissure sealants remains speculative. Fluoride release might occur from the insoluble sealant material as a result of porosity or ion exchange procedure. Several studies have looked at benefits of such combinations, but no study has documented a clear-cut clinical benefit or potential benefit of the same, rather seems a marketing ploy. This paper reviews evidence pertaining to use of combination of fluoride and sealants for caries prevention, their feasibility and effectiveness after addition of fluoride to sealants through in vitro and in vivo studies.

Selantes dentários usam o princípio de bloqueio de fóssulas e fissuras suscetíveis à cárie, tornando-as resistentes à cárie. O flúor é outro agente eficaz na redução da cárie dentária. No entanto, os benefícios adicionais do flúor podem ser alcançados por meio da sua aplicação tópica. Esses efeitos podem ser potencializados por uma exposição prolongada da superfície do dente a agentes de liberação de flúor. Assim, o conceito de adição de flúor a selantes de fóssulas e fissuras foi introduzido. Até agora, dois métodos de incorporação de flúor em selantes de fóssulas e fissuras foram formulados. O primeiro método emprega a adição de sais de fluoreto solúveis na resina não polimerizada. O segundo utiliza um composto de flúor orgânico, que pode ser quimicamente ligado à resina. Mas o mecanismo de liberação de flúor de selantes de fissuras fluoretados permanece desconhecido. A liberação de flúor pode ocorrer a partir do selante insolúvel como resultado de porosidade ou de um processo de troca iónica. Vários estudos analisaram os benefícios de tais combinações, mas nenhum estudo documentou um benefício real ou potencial do mesmo, em vez disso, parece ser mais uma jogada de marketing. Este artigo de revisão traz comentários relativos à utilização da combinação de flúor e selantes para prevenção de cáries, sua viabilidade e eficácia após adição de fluoreto em selantes utilizando estudos in vitro e in vivo.