Microwave solution route to ceramic ZnAl2O4 nanoparticles in 10 minutes: inversion and photophysical changes with thermal history

Microwave-assisted synthesis of ZnAl2O4 nanoparticles in minutes using metalorganic precursors is reported. Phase-pure ZnAl2O4 with an average crystallite size of similar to 5 nm is formed in the solution medium at 185 degrees C. Annealing in air at temperatures between 500 and 1200 degrees C increases the crystallite size to similar to 32 nm. The as-prepared particles are largely shapeless, whereas polyhedral crystallites with well-defined grain boundaries can be seen in the HR-TEM image of the annealed samples. Diffuse reflectance spectroscopy provides insight into the structural development of the oxide spinel. Rapid synthesis leads to significant crystallographic inversion (similar to 33%), as observed by X-ray photoelectron spectroscopy. Photoluminescence spectroscopy shows that the different emission bands are due both to anti-site defects in the form of zinc interstitials caused by cationic inversion and to oxygen and zinc vacancies. Optical measurements suggest that inhomogeneity in cationic distribution, probably caused by the rapidity of synthesis, is prevalent even after annealing at temperatures up to 1200 degrees C, and plays a significant role in controlling the emission properties of the spinel. The microwave-assisted technique using metalorganic precursors is an easy path to the rapid synthesis of doped ZnAl2O4 phosphors

Cr-doped ZnAl2O4: Microwave solution route for ceramic nanoparticles from metalorganic complexes in minutes

A combination of microwave irradiation and metalorganic precursors in solution was used for the synthesis of Cr:ZnAl2O4 nanoparticles with high yields (similar to 92%). Though the spinel phase is formed after similar to 40minutes, 60minutes of microwave irradiation was required for the complete transformation of precursors into the spinel. The as-prepared material is nanocrystalline and phase-pure and was subjected to annealing in air at different temperatures. Annealing improved the crystallinity, and the material turned pink at 1200 degrees C. The structural and optical properties were investigated by XRD, HR-TEM, FE-SEM, FT-IR, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The two bands in the excitation spectra (400 and 540nm) became more intense as the annealing temperature was raised. The 400nm band was asymmetric and consisted of two peaks, suggesting a trigonal distortion. The emission spectra consisted of a zero phonon line (ZPL), along with its associated multi-phonon side bands. The high Dq/B (3.21) suggested the presence of Cr3+ in a strong crystal field. With annealing, the emission lifetimes increased from similar to 7 to similar to 34ms. This work demonstrates rapid, low-temperature synthesis of a red-emitting phosphor, with potential applications in bio-imaging, sensors, and lighting

PD-1 derived CA-170 is an oral immune checkpoint inhibitor that exhibits preclinical anti-tumor efficacy

Sasikumar et al. describe the identification and characterization of CA-170, a small molecule inhibitor of PD-L1 and VISTA. They find that CA-170 activates T cells and exhibits anti-tumor efficacy in mouse models. This study highlights the potential of CA-170, which has advanced to human clinical trials, as an anti-cancer drug