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Highly selective and sensitive detection of toxic mercury ions (Hg2+) has become a critical issue in recent decades, due to increasing environmental and health requirements. Herein, carbon dots reduced and decorated Ag (CDs/Ag) nanoparticles based fiber probes were fabricated, providing a "turn-off" surface-enhanced Raman spectroscopy (SERS) for low-concentration Hg2+ ions detection. The CDs/Ag nanoparticles fiber probe exhibits better SERS performance than that of Ag nanoparticles fiber, attributed to the stronger electromagnetic intensities induced by localized surface plasmon resonance (LSPR) and larger hot-spot areas resulting from the interaction between silver nanoparticles and carbon dots, under 532 nm beam excitation. As low as 10−11 M Hg2+ ions can be detected through the decrease in Raman scattering intensities of CV molecules, due to the SERS inactive Hg metal layer wrapping the surface of silver nanoparticles, through the reduction of Hg2+ ions by carbon dots. The dropping of silver nanoparticles' LSPR induced absorption peak, EDS elemental mapping, and XPS analysis all confirm that the wrapping decreases the LSPR effect and corresponding Raman intensity. Furthermore, the detection shows high selectivity and can only be applied for detecting Hg2+ ions, owing to the reduction capability of carbon dots. The close analysis results obtained using SERS fiber probes and commercial inductively coupled plasma-mass spectrometry (ICP-MS) for detecting Hg2+ ions in real water sample confirm the reliability of this detection method. This research indicates the CDs/Ag fiber probe has a great potential application for environmental Hg2+ ions detection. [Display omitted] • Carbon dots directly reduced Ag+ ions and the formation of CDs/Ag composite nanoparticles fiber probes; • Better SERS performance from CDs/Ag nanoparticles fiber probes due to stronger LSPR effect and larger hot-spot areas; • Highly selective trace mercury ions detection from the decrease of CV molecules SERS intensities; • CDs reduced Hg2+ into metallic layer wrapping on CDs/Ag nanoparticles. [ABSTRACT FROM AUTHOR]

The effects of ZrO 2 addition on the glass network structure, crystallization behavior and microwave dielectric properties of ZnO-B 2 O 3 glass-ceramics were investigated. The introduction of ZrO 2 decreases the connectivity of the superstructure in the borate glass network and thus affects the crystallization behavior of glass, leading to the transformation of the main crystalline phase from Zn 4 B 6 O 13 to ZnB 4 O 7 and Zn 3 B 2 O 6. With the increase of ZrO 2 content, the microstructure changed from the branch-like structure into the net-like structure. For the sintered glass-ceramics, the relative permittivity increased with the ZrO 2 content, which relates to the decrease in the vibrational energy of the B-O bond. In addition, the glass-ceramic with 0.25 mol% ZrO 2 exhibits the maximum Q×f value due to the low disorder of B3+ cations. The ZnO-B 2 O 3 glass-ceramic with 0.25 mol% ZrO 2 sintered at 660 °C for 5 h exhibits the optimum microwave dielectric properties with ε r = 6.18, Q×f = 23,670 GHz, τ f = −65 ppm/°C. The high Vickers hardness of 662 kgf/mm2 and excellent chemical compatibility with Ag electrode demonstrated that the glass-ceramic is a good candidate for ULTCC application. • Raman spectroscopy was used to characterize the change of borate superstructures units in the glass at the intermediate-range order scale, which is an important reason for the change of the main crystalline phase when the introduction of ZrO 2 into the ZnO-B 2 O 3 glass system • The Zr4+ ions in the glass-ceramics have a strong accumulation effect on the O2- ions, which leads to the reduction of the vibration energy of the B-O bond and affect the polarization behavior, finally the relative dielectric constant increased. • In the glass-ceramic with 0.25mol% ZrO 2 content, the B3+ions show the highest degree of cationic order, which indicates that the crystal structure in glass-ceramic is closer to the standard lattice structure, so the highest Q×f value is obtained. [ABSTRACT FROM AUTHOR]

Ho 3+ /Y 3+ co-doped BaF 2 nanocrystals were precipitated in oxyfluoride glasses through conventional melt-quenching and subsequent thermal treatment. X-ray diffraction patterns, transmission electron microscope images and absorption spectra confirmed the incorporation of Ho 3+ /Y 3+ ions into BaF 2 nanocrystals in glass-ceramics. With the gradual substitution of Ho 3+ ions by Y 3+ ions, concentration dependent energy transfer between excited Ho 3+ ions were suppressed and relative emission intensity at 1.2 μm band was enhanced. The maximum emission cross-section calculated was 0.60 × 10 −20 cm 2 in BH1-GC specimen, indicating that Ho 3+ /Y 3+ co-doped glass-ceramics have a great potential for the development of 1.2 μm band gain medium. [ABSTRACT FROM AUTHOR]

ZnAl 2 O 4 nanocrystals (NCs) embedded transparent glass-ceramics containing relatively large amount of alkali oxide were prepared and effects of the crystallization on ion-exchange properties of glass-ceramics were investigated. Precipitation of ZnAl 2 O 4 NCs not only improves the Vickers hardness of the glass-ceramics, but also reduces the content of zinc and aluminum with concomitant increase in the content of sodium in the residual glassy phase. These changes in the residual glassy phase decrease the activation energy of K–Na ion-exchange and enhance the diffusion coefficient of potassium, resulting in the large ion-exchange depth and significantly improved Vickers hardness of the ion-exchanged glass-ceramics. These results show that glass-ceramics containing non-alkali nanocrystals have promising applications in fields of covers for optoelectronic devices. • ZnAl 2 O 4 NCs were precipitated in transparent aluminosilicate GCs containing large amount of alkali oxides. • Crystallization of ZnAl 2 O 4 NCs can improve ion exchange properties. • Compositional changes in residual glassy phase in GCs was responsible for the enhanced ion-exchange. [ABSTRACT FROM AUTHOR]