The properties of NaGdF4:Yb, Er nanomaterials tuned by synthesis conditions have always been one of the research hotspots in the field of upconversion nanomaterials. In this work, NaGdF4:Yb, Er upconversion nanomaterials capped with oleic acid (OA) molecules were prepared by one-step hydrothermal method. Controlling the fluorescence properties of NaGdF4:Yb, Er nanomaterials by changing the synthesis conditions were principally investigated. The results showed that the crys-talline state of the as-prepared upconversion nanomaterials tended to be intact and fluorescence emission capability enhanced when the reaction temperature increased from 140(degrees )C to 160(degrees)C, 180(degrees)C and the reaction time extended from 6h to 18h. From 0.00mmol to 0.75, 2.25, 5.00, 8.75, 12.50, 17.50mmol of sodium hydroxide amount, the synthesized up conversion nanoparticles (UCNPs) transferred from orthorhombic GdF3 to hexagonal b-NaGdF4. And when the amount of sodium hydroxide was 2.25mmol, the as-prepared nanoparticles exhibited stronger luminescence intensity. The ratio of Re3(& thorn;)(Gd-3 & thorn;:Yb-3 & thorn;:Er-3 & thorn;) could also affect the properties of the as-prepared UCNPs. The nanomaterials emitted relatively stronger fluorescence when the ratio among Gd-3 & thorn;, Yb-3 & thorn;, Er-3 & thorn;was 78:20:2. This work provides solid foundation for further theoretical study and prac-tical application of NaGdF4:Yb, Er nanomaterials.

Exploring unique topological states in condensed-matter systems has attracted great interest especially for the topological phonons recently. Based on the unbiased structure prediction approach combined with first-principles calculations, the long-sought crystal structure of Th2BC2 is determined. Most importantly, we show by the symmetry analysis and the phonon tight-binding Hamiltonian that Th2BC2 hosts nodal surface phonons on the q(z) = +/-pi plane, coexisting with nodal line phonons on the q(y) = 0 and q(y) = +/-pi planes, consequently, forming cagelike phonons. The nodal surface phonons are protected by the screw axis (C) over tilde (2z), and the nodal line phonons are enforced by inversion and time-reversal symmetries, demonstrated by the codimension argument and the effective model analysis. In addition, we also investigate the phonon surface states and the isofrequency arc on the (100) surface, which benefit the confirmation of the nodal cage phonons in experiments. Our paper not only determines the long-sought crystal structure of Th2BC2, but also provides an ideal candidate to realize the exotic topological phonon excitations.

The lead-free copper-based halide perovskite Cs3Cu2I5 is a promising material that can overcome the toxicity and instability of lead-based halide perovskites, thereby affording remarkable performance in the field of optoelectronics. Cs3Cu2I5 perovskite exhibits blue emission with a very high photoluminescence quantum yield (PLQY). First-principles calculations were used herein to theoretically expound the origins of the high PLQY of Cs3Cu2I5: (i) the low symmetry of Cs3Cu2I5 breaks the forbidden transition and enables the transition process; (ii) the large transition matrix and high transition rate increase the probability for radiative recombination of Cs3Cu2I5; (iii) the good defect tolerance broadens the path for thermal relaxation and radiative recombination. The high transition rate and good defect tolerance account for the high-efficiency PLQY of the lead-free copper-based perovskite, Cs3Cu2I5.

As a promising inorganic semiconductor photocatalyst, TiO2 has been widespread concerned since 1972. However, its practical application is limited due to its low efficiency for utilizing solar light and rapid recombination of photo-generated charges. Here, we report a way to solve these problems by calcining TiO2 samples under different conditions. It was found that the catalytic performance of TiO2 catalysts was closely related to calcination temperature and calcination atmosphere. The XRD, Raman spectra, BET, UV-vis spectra, SEM and TG-DTA investigations of the catalysts revealed that the crystal structure of TiO2, the specific surface area, and abundant oxygen vacancies were the primary factors influencing the performance of TiO2 catalysts. Consequently, the TiO2 nanocrystal calcined in a nitrogen/hydrogen mixed atmosphere at 300 degrees C for 3 h exhibited higher catalytic activity than others. These results demonstrated that annealing conditions can play an important role in catalyst activity.

TiO2 crystals with different morphologies have been successfully synthesized by simple hydrothermal method. All samples are characterized carefully by XRD, SEM, TEM, and BET techniques and the morphological effect on the photocatalytic activity of the obtained TiO2 crystals has been evaluated by degrading the pollutant molecules. The experimental results show that the TiO2 samples with different morphologies exhibited different activities to pollutant degradation. The coreshell spheres have exhibited the best photocatalytic activity, with the almost complete degradation of methyl orange (MO) and rhodamine B within 15 min under UV-light irradiation. After 20 min UV-light irradiation, the degradation efficiency of the MO solution is about 68.9%. It can be concluded that a morphological effect is responsible for the photocatalytic performance. The crystals with large BET surface area, the small crystallite size shows the better the photocatalytic performance.

We successfully obtained alpha-Fe2O3 microspheres with a ca. 500 nm diameter through solvothermal method and subsequent annealing at 300 degrees C for 2 h in air. The composition and morphology of the samples were analyzed by FT-IR, XRD, SEM, TEM, TG and BET. The gas sensitivity measurements indicated that the sensor of alpha-Fe2O3 microspheres showed good selectivity and high response to aniline gas. This sensor showed a response to aniline gas as low as 0.01 ppm, and the response achieved 12.5 at 150 degrees C to 10 ppm aniline. The enhanced gas sensing properties were due to enough pore architectures of the sample. These results demonstrated that the samples have a good application prospect in preparation of high-performance gas sensors.

Nanosized TiO2 photocatalysis technology is one of the most promising technologies for the treatment of wastewater containing azo dyes. In this work, TiO2 was deposited on a mesoporous SBA-15 molecular sieve by chemical deposition, and rare earth (RE) metal neodymium (Nd) was further deposited on the surface of the catalyst to obtain an Nd-TiO2-SBA-15 photocatalyst. The prepared photocatalyst was analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), and N-2 adsorption-desorption. The activity of the Nd-TiO2-SBA-15 photocatalyst was evaluated by using methyl orange to represent the azo dye. The effects of different Nd deposition amounts and different solution pH values on the photocatalyst performance were principally studied. The results show that the synthesized photocatalyst formed an anatase crystal with a mesoporous structure. The specific surface area and pore size of the photocatalyst are 548.2 m(2)/g and 6.5 nm, respectively. As the amount of Nd deposition gradually increases, the activity of photocatalyst undergoes a process of first rising and then decreasing. In addition, the photocatalyst maintains high photocatalytic activity in the pH range of 2-10, exhibiting good acid-base adaptability. This work demonstrates that the Nd-TiO2-SBA-15 nanophotocatalyst has broad practical application prospects on a large scale. (C) 2018 Published by Elsevier B.V.

High-efficiency nanophotocatalysts with large specific surface areas have a broad range of application prospects in the catalytic oxidation treatment of organic pollutants in wastewater. A chemical method was used to synthesize a TiO2 nanophotocatalyst with a mesoporous structure upon which a rare earth metal (Nd) was deposited, namely Nd-TiO2-SBA-15 (NTS). The prepared NTS was characterized using X-ray diffractometry, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectrometry. The photocatalytic mechanism was explored using scavenger experiments with photoinduced carriers combined with total organic carbon and UV-Vis measurements. At the same time, the kinetic properties of the NTS photocatalytic degradation of methyl orange (MO) were evaluated. The results showed that the deposition of TiO2 nanoparticles on the surface of the SBA-15 molecular sieve did not change the mesoporous structure, and Nd was uniformly distributed on the surface of the nanophotocatalyst. The photogenerated holes of the NTS played an important role in the photocatalysis process. In addition, the synthesized NTS had good adaptability in the range of pH 2-10. At pH 4, the reaction rate constant (k) of the MO photocatalytic degradation by NTS was 0.011825 mg.(L.min)(-1), and the adsorption equilibrium constant (K) was 0.051359 L mg(-1). In addition, the photocatalytic degradation rate of MO by NTS remained above 70%, even when the NTS was recycled four times. The NTS showed a good performance after recycling. This work provides a good foundation for the large-scale application of NTS. (C) 2019 Elsevier Ltd. All rights reserved.

Breast cancer (BC) is a serious disease to threat lives of women. Numerous studies have proved that BC originates from cancer stem cells (CSCs). But at present, no one approach can quickly and simply identify breast cancer stem cells (BCSCs) in solid tumor. Nanotechnology is probably able to realize this goal. But in study process, scientists find it seems that nanomaterials with one modality, such as magnetic resonance imaging (MRI) or fluorescence imaging (FI), have their own advantages and drawbacks. They cannot meet practical requirements in clinic. The nanoprobe combined MRI with FI modality is a promising tool to accurately detect desired cells with low amount in tissue. In this work, we briefly describe the MRI and FI development history, analyze advantages and disadvantages of nanomaterials with single modality in cancer cell detection. Then the application development of nanomaterials with dual-modality in cancer field is discussed. Finally, the obstacles and prospective of dual-modal nanoparticles in detection field of BCSCs are also pointed out in order to speed up clinical applications of nanoprobes.