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A color tunable emission was obtained in CaHfO3:Ce3+,Tb3+ phosphor. XRD, luminescence spectra, decay curves, temperature-dependent emission spectra and quantum efficiency were used to characterize the structure and luminescence properties. Under 330 nm excitation, the Ce3+ singly doped CaHfO3 samples exhibited intense blue emission. The emission intensity reached the maximum at 1 mol% Ce3+. CaHfO3:0.1Ce3+ samples possessed high quantum efficiency of 52.05%. In Tb3+ co-doped CaHfO3:Ce3+ phosphors, the emission position of Ce3+ blue shifts slightly due to weaker crystal field strength around Ce3+. Besides, the energy transfer between Ce3+ and Tb3+ leads to tunable emission colors from blue to cyan, then to green. The energy transfer efficiency and thermal stability are investigated in detail.

In this work, based on density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, we theoretically investigate the excited-state process of the 2-(6'-hydroxy-2'-pyridyl)benzimidazole (2HPB) system in acetonitrile and water solvents. Since acetonitrile is an aprotic solvent, it has no effect on the solvent-assisted excited-state proton transfer (ESPT) process. Therefore, the 2HPB molecule cannot transfer the proton in acetonitrile, which is consistent with previous experimental observation. On the other hand, 2HPB can combine one water molecule (which is a protic solvent), forming the 2HPB–H2O complex in the S0 state. After photoexcitation, the intermolecular hydrogen bonds O1H2···O3 and O3H4···N5 both get strengthened in the S1 state, which leads to the possibility of a water-assisted ESPT process. Further, the charge redistribution reveals the tendency of ESPT. By exploring the potential energy curves for the 2HPB–H2O complex in water, we confirm that a stepwise double proton transfer process occurs in the S1 state. Water-assisted ESIPT can occur along O1H2···O3 or O3H4···N5 because of their similar potential barriers. Based on the stepwise ESPT mechanism, we reinterpret the absorption and fluorescence spectra mentioned in the experiments and confirm the rationality of the water-assisted ESPT process.

Polyacrylonitrile (PAN) grafted amino-functionalized multi walled carbon nanotubes (amino-MWCNTs) were synthesized by in situ polymerization under aqueous solvent. The grafted MWCNT/PAN nascent composite fibers were prepared by the wet spinning method. Fourier transform infrared spectroscopy and Raman spectroscopy indicated that the amino-MWCNTs and PAN macromolecular chains had interfacial interactions and formed chemical bonds. The grafting content of the PAN polymer on the amino-MWCNTs was up to 73.2% by thermo gravimetric analysis. The incorporation of the grafted MWCNTs improved the degree of crystallization and crystal size of PAN nascent fibers, and changed the thermal properties during exothermic processing in an air atmosphere. Morphology analysis and testing of mechanical properties showed that the grafted MWCNT/PAN nascent composite fibers with a more uniform diameter distribution and larger diameter had higher tensile strength and tensile modulus than the control PAN nascent fibers.

Nesting-site selection is an important aspect of the breeding process in birds, as it usually determines nesting and breeding successes. Many factors can affect bird nest-site selection, including anthropogenic disturbance. In an extreme desert environment, such as the Taklamakan Desert in China, birds’ survival pressure is high, especially for rare species such as the Xinjiang Ground-jay (Podoces biddulphi). We studied nest-site selection in this species from March 2017 to May 2019. A Chi-square test, independent sample t-test, Mann–Whitney U-test, and generalized linear models were applied to possible nest-site selection factors for Xinjiang Ground-jays. The main determining factors were the distances to human settlements, water, and the edge of the oasis. Xinjiang Ground-jays nested near available water resources for easier access, which is important in arid environments. Individuals chose to nest far from the oasis edges and settlements to increase food availability and reduce interference from human activities, respectively. Overall, water, food availability, and anthropogenic influence were the main factors affecting the nest-site selection of Xinjiang Ground-jays in this study. Therefore, these results suggest that there is a trade-off between survival and reproduction. Further studies are required to verify whether similar site preferences may also apply to other desert-dwelling species.

Development of high-performance electrocatalyst for oxygen reduction reaction is imperative to address the issues of energy and environment. Zeolitic imidazolate frameworks (ZIFs)/carbon nanotubes (CNTs) composites have been regarded as a promising precursor to fabricate efficient catalysts. However, it is challenging to synthesize ZIF/CNT composites with unique structure and controllable compositions. Herein, a CNT-directing assembly strategy is developed to synthesize ZIF/CNT nanonecklaces with unique structure and tunable Zn/Co ratios. The oxidized CNTs are employed as a structure-directing agent to prepare one-dimensional nanonecklaces. The ratios of Co/Zn in the ZIF can be adjusted from 0 to 8:2 by simply changing the amount of metal precursors. After carbonization and acid leaching, Co nanoparticles are embedded in the graphitization carbon matrix. Zn species are removed completely and produce plenty of nanopores in the carbon framework. Such ZIF/CNT nanonecklaces derived carbon composites are further used as a catalyst for oxygen reduction reaction, which show high onset potential (0.92 V) and high limiting current density (5.31 mA cm−2 at 0.30 V). This work provides a new synthesis strategy for the fabrication metal/carbon composited catalysts.

A new pseudo-seeding and nano-scaffolding method was developed to synthesize thin ZIF-8 hybrid membranes (100–200 nm) with remarkable mechanical and structural stability and high H2 permeance (2.87 × 10−5 mol m−2 s−1 Pa−1) and selectivity over CO2 (14), N2 (18), CH4 (35), C3H6 (52.4) and C3H8 (950.1).

In this work, using density functional theory and time-dependent density functional theory methods, we theoretically studied the excited-state behaviors of 3 novel 2-(2-hydroxyphenyl)benzothiazole (HBT) derivatives (HBT-H-H, HBT-CN-H, and HBT-CN-CN). Analyses about primary chemical structures such as bond lengths and bond angles, we found that all the intramolecular hydrogen bonds in these 3 structures should be strengthened in the S1 state upon the photoexcitation. Exploring the infrared vibrational spectra at the hydrogen bonds groups, we confirmed that nonsubstitutional HBT-H-H structure might play more important roles in the excited-state intramolecular proton transfer (ESIPT) reaction than HBT-CN-H and HBT-CN-CN. Further, investigating vertical excitation process, it can be revealed that charge redistribution involved in hydrogen bonding moieties could facilitate the ESIPT reaction. Based on constructing potential energy curves of both S0 and S1 states, we confirmed that the substituents on HBT systems can reasonably regulate and control the ESIPT processes because of the different potential energy barriers. We deem that this present work not only elaborates the different excited-state behaviors of HBT-H-H, HBT-CN-H, and HBT-CN-CN but also may play important roles in designing and developing new materials and applications involved in HBT systems in future.

Nanosized spinelCoAl2-xRexO4complex oxides were prepared by self-propagation combustion method. The products have been characterized by XRD, SEM, and EDS. The results indicated that Al3+can be partly replaced by Re3+when the doped amount is less than 10%, which forms single solid solution. The NIR reflectance and chromatic properties of samples have also been investigated. The substitution of Re3+for Al3+in CoAl2O4can increase the blueness of pigments. SEM results revealed that the obtainedCoAl2-xRexO4pigments consisted of highly dispersed spherical-like nanoparticles with uniform size distribution. EDS results indicated that the distribution of element was considerably uniform with no chemical segregation phenomenon.

The highly dispersed nanostructured NiTiO3pigments and NiTiO3/TiO2composite pigments can be synthesized at relative low temperature. The activation energy of crystal growth of NiTiO3during calcinations via salt-assistant combustion method is 9.35 kJ/mol. The UV-vis spectra results revealed that the absorbance decreased with the increasing of calcinations temperature due to small size effect of nanometer particles. The optical data of NiTiO3nanocrystals were analyzed at the near-absorption edge. SEM showed that the obtained NiTiO3nanocrystals and NiTiO3/TiO2nanocomposite were composed of highly dispersed spherical-like and spherical particles with uniform size distribution, respectively. The chromatic properties and diffuse reflectance of samples were investigated. The obtained NiTiO3/TiO2composite samples have higher NIR reflectance than NiTiO3pigments.