The development of atmospheric water generator has depended critically on the preparation of hygroscopic materials. In our systematic efforts toward porous frameworks for effective humidity reduction, a super hygroscopic materials,...
Low (α)- and high-temperature (β) forms of BiTaO have attracted much attention due to their dielectric and photocatalytic properties. In the present work, a third form, the so-called HP-BiTaO, was synthesized at high temperature and pressure. The phase evolution, phase transformations, and dielectric properties of α- and β-BiTaO and HP-BiTaO ceramics are studied in detail. β-BiTaO ceramics densified at 1300 °C with the microwave permittivity ε ≈ 53, the microwave quality factor Q ≈ 12070 GHz, and the temperature coefficient of resonant frequency τ ≈ -200 ppm/°C. HP-BiTaO ceramics were synthesized at 5 GPa and 1300 °C followed by annealing at 600 °C. In contrast with the α phase, HP-BiTaO exhibited ε ≈ 195 at 1 kHz to 10 MHz, accompanied by a low dielectric loss of ∼0.004. The relation between structure and dielectric properties is discussed in the context of Shannon's additive rule and bond theory.
The coordination interactions between transitionmetal ions (Cu 2+ , Ag + ) and sulfur atoms on ultrathin twodimensional (2D) nanosheets of spin-crossover (SCO) metal− organic frameworks {[Fe(1,3-bpp) 2 (NCS) 2 ] 2 } n (1,3-bpp = 1,3di(4-pyridyl)propane), which constructed the ultrathin 2D nanosheets into three-dimensional (3D) nanoparticles, have made a profound effect on the SCO performance. Compared with 2D nanosheets, both the intraligand π−π* transition band and the metal-to-ligand charge transition band from the d(Fe) + π(NCS) to π*(1,3-bpp), for the 3D nanoparticles, have shown dramatic blue-shifts; meanwhile, the d−d transition band for the high-spin (HS) state Fe(II) ions has been generated, suggesting significantly the influence of 3D assemble-caused dimensional changes on the solidstate SCO performance of ultrathin 2D nanosheets. More importantly, by loading on the ytterbium ion (Yb 3+ )-sensitized hexagonal phase upconverting nanoparticles in the aqueous colloidal suspension, the near infrared (NIR) light (980 nm) triggered HS (high spin) to LS (low spin) state transitions have been observed, demonstrating the achievement of challenging target of NIR lighttriggered molecular conversion under environment conditions.
Traditional
methods of preparing regular-shaped silver chloride
nanoparticles for antiseptic use are complex. Squarelike AgCl nanoparticles
with an average size of about 400 nm were prepared using the two-dimensional
(2D) metal–organic framework nanosheet Ni(pyz)2Cl2 (pyz, pyrazine) and the surfactant polyvinyl pyrrolidone
(PVP), which exhibit enhanced antibiofilm properties compared with
common AgCl nanoparticles. This excellent performance can be attributed
to the stronger light absorption ability, which helps in producing
a larger amount of hydroxyl radicals that have a strong oxidative
function to destroy the structure of bacteria, as well as a larger
surface area, which aids in the release of more silver ions into the
bacterial cell. This work has provided a creative method for preparing
squarelike AgCl nanoparticles with uniform morphology that does not
easily agglomerate, showing an immense application prospect in the
antibacterial field.
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