ZnTi-layered double hydroxides（LDHs） with varying Zn/Ti ratio have been synthesized by coprecipitation of zinc and titanium salts from homogeneous solution.The obtained ZnTi-LDHs possess high crystallinity and hiera...ZnTi-layered double hydroxides（LDHs） with varying Zn/Ti ratio have been synthesized by coprecipitation of zinc and titanium salts from homogeneous solution.The obtained ZnTi-LDHs possess high crystallinity and hierarchical structure with improved UV-absorbance property.The UV-vis spectra show that the UV absorbing properties of ZnTi-LDHs is stronger and broader than both MgAl-LDH and ZnAl-LDH due to the existence of Ti.Moreover,the UV absorption property increased with the content of Ti,which can be ascribed to the decrease in the band gap energy,as clearly confirmed by density functional theory calculations.When irradiated by UV rays,the property of the samples with generated free radicals（OH^·and O2^·） was evaluated by means of electron spin resonance（EPR）.ZnTi-LDHs generated a relatively lower active radicals in contrast with TiO2 and ZnO,which implied an increased safety used as sunscreens.Therefore,this work provides a detailed understanding of UV shielding properties of ZnTiLDHs which was unrevealed previously,and demonstrates the expansive application prospects of ZnTiLDHs in the field of sunscreens.展开更多
Dielectric spectra of 4A zeolite particles bulked in deionized water（4A/W） or cyclohexane（4A/C） were measured respectively under different temperatures, and two dielectric relaxations were found in both of 4A/W an...Dielectric spectra of 4A zeolite particles bulked in deionized water（4A/W） or cyclohexane（4A/C） were measured respectively under different temperatures, and two dielectric relaxations were found in both of 4A/W and 4A/C. Because of existence of water molecules in pores, both low and high frequency relaxation times（t LFR and t HFR） of 4A/W decreased more sharply than 4A/C with increasing temperature.According to the temperature dependence of t LFR and t HFR, the activation energies of Na＋interacting with framework under hydrated and dehydrated environments were calculated respectively, and the original properties of Na＋in dehydrated zeolite were obtained by analyzing the dielectric properties of 4A/C.Furthermore, a transient state of Na＋motion with temperature was found in 4A/C system.展开更多
基金supported by the National Natural Science Foundation of China (No. 21301012)the Development of High-Caliber Talents Project of Beijing Municipal Institutions (No. CIT & TCD 201504009)+1 种基金China Cosmetic Collaborative Innovation Center, BTBUthe Open Research Fund Program of Beijing Key Lab of Plant Resource Research and Development, BTBU
文摘ZnTi-layered double hydroxides（LDHs） with varying Zn/Ti ratio have been synthesized by coprecipitation of zinc and titanium salts from homogeneous solution.The obtained ZnTi-LDHs possess high crystallinity and hierarchical structure with improved UV-absorbance property.The UV-vis spectra show that the UV absorbing properties of ZnTi-LDHs is stronger and broader than both MgAl-LDH and ZnAl-LDH due to the existence of Ti.Moreover,the UV absorption property increased with the content of Ti,which can be ascribed to the decrease in the band gap energy,as clearly confirmed by density functional theory calculations.When irradiated by UV rays,the property of the samples with generated free radicals（OH^·and O2^·） was evaluated by means of electron spin resonance（EPR）.ZnTi-LDHs generated a relatively lower active radicals in contrast with TiO2 and ZnO,which implied an increased safety used as sunscreens.Therefore,this work provides a detailed understanding of UV shielding properties of ZnTiLDHs which was unrevealed previously,and demonstrates the expansive application prospects of ZnTiLDHs in the field of sunscreens.
基金supported by Beijing Natural Science Foundation (Nos. 2143040, 2144047)the Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions (No. CIT&TCD201504009)National Natural Science Foundation of China (No. 21301012)
文摘Dielectric spectra of 4A zeolite particles bulked in deionized water（4A/W） or cyclohexane（4A/C） were measured respectively under different temperatures, and two dielectric relaxations were found in both of 4A/W and 4A/C. Because of existence of water molecules in pores, both low and high frequency relaxation times（t LFR and t HFR） of 4A/W decreased more sharply than 4A/C with increasing temperature.According to the temperature dependence of t LFR and t HFR, the activation energies of Na＋interacting with framework under hydrated and dehydrated environments were calculated respectively, and the original properties of Na＋in dehydrated zeolite were obtained by analyzing the dielectric properties of 4A/C.Furthermore, a transient state of Na＋motion with temperature was found in 4A/C system.
