High dispersion of heteropolyacid nanoparticles on hydrothermally Cs-modified three-dimensionally ordered macroporous SiO2 with excellent selectivity in methacrolein oxidation

Heteropolyacid nanoparticles(NPs)were supported on Cs-modified three-dimensionally ordered macroporous(3DOM)SiO2 and used as the catalyst for the oxidation of methacrolein(MAL)to methacrylic acid(MAA).Hydrothermal treatment and incipient wetness impregnation were employed respectively for the Cs-modification.It was found that hydrothermal Cs-modification of 3DOM SiO2 promoted the dispersion of the supported heteropolyacid,which showed an average particle size of 5.2 nm,much smaller than that(17.6 nm)on the Csmodified 3DOM SiO2 prepared by incipient wetness impregnation.The effects of hydrothermal treatment on the structure and catalytic performance of the catalyst were investigated.Results showed that the ion exchange between Cs+and the surface silanol groups on 3DOM SiO2 was promoted with the increase of the hydrothermal temperature.Meanwhile,Cs-modification helped the heteropolyacid to retain intact Keggin structure,inhibiting the formation of MoO3.Highly dispersed heteropolyacid NPs with enhanced structural stability exhibited excellent selectivity to MAA in the oxidation of MAL.

Organic room-temperature phosphorescent polymers for efficient X-ray scintillation and imaging

Materials that exhibit visible luminescence upon X-ray irradiation show great potential in the medical and industrial fields.Pure organic materials have recently emerged as promising scintillators for X-ray detection and radiography,due to their diversified design,low cost,and facile preparation.However,recent progress in efficient radioluminescence has mainly focused on small molecules,which are inevitably associated with processability and repeatability issues.Here,a concise strategy is proposed to prepare radioluminescent polymers that exhibit multiple emission colors from blue to yellow with high brightness in an amorphous state by the radical copolymerization of negatively charged polyacrylic acid and different positively charged quaternary phosphonium salts.One of the obtained polymers exhibits excellent photostability under a high X-ray irradiation dosage of 27.35 Gy and has a detection limit of 149 nGy s^(−1).This performance is superior to that of conventional anthracene-based scintillators.Furthermore,by simply drop-casting a polymer methanol solution on a quartz plate,a transparent scintillator screen was successfully fabricated for X-ray imaging with a resolution of 8.7 line pairs mm^(−1).The pure organic phosphorescent polymers with a highly efficient radioluminescence were demonstrated for the first time,and the strategy reported herein offers a promising pathway to expand the application range of amorphous organic scintillators.