The coronavirus disease 2019(COVID-19)pandemic has caused a surge in demand for face masks,with the massive consumption of masks leading to an increase in resource-related and environmental con-cerns.In this work,we f...The coronavirus disease 2019(COVID-19)pandemic has caused a surge in demand for face masks,with the massive consumption of masks leading to an increase in resource-related and environmental con-cerns.In this work,we fabricated meltblown polypropylene(mb-PP)-based high-performance planar face masks and investigated the effects of six commonly used disinfection methods and various mask-wearing periods on the reusability of these masks.The results show that,after three cycles of treatment using hot water at 70℃ for 30 min,which is one of the most scalable,user-friendly methods for viral disinfection,the particle filtration efficiency(PFE)of the mask remained almost unchanged.After mask wearing for 24 h and subsequent disinfection using the same treatment procedures,the PFE decreased to 91.3%;the average number of bacterial and fungal colonies was assessed to be 9.2 and 51.6 colony-forming units per gram(CFU∙g^(-1)),respectively;and coliform and pyogenic bacteria were not detected.Both the PFE and the microbial indicators are well above the standard for reusable masks after disinfection.Schlieren pho-tography was then used to assess the capabilities of used and disinfected masks during use;it showed that the masks exhibit a high performance in suppressing the spread of breathed air.展开更多
Excited-state intramolecular proton transfer(EsiPT)involves photochemical tautomerization between two excited states(E*and K*)via intramolecular proton transfer.Developing polymer photochromism based on the photochemi...Excited-state intramolecular proton transfer(EsiPT)involves photochemical tautomerization between two excited states(E*and K*)via intramolecular proton transfer.Developing polymer photochromism based on the photochemical tautomerization of organic ESiPT molecules has been rarely reported.We report the ESIPT molecule HBT-2oH exhibits concentration-dependent photochromic behavior in a polyurethane(PU)network.At low concentrations,HBT-2oH primarily exists in the trans-enol configuration without intramolecular OH..N hydrogen bonds in PU,emitting blue fluorescence at~464 nm(enol emission).Upon UV irradiation,the dihedral angle between the proton donor and acceptor twists to form an intramolecular OH-.N H-bond,converting trans-enol to cis-enol and resulting in ESIPT with pale yellow fluorescence at~603 nm(keto emission).The photochromic effect of HBT-2OH@PU diminishes at high concentrations due to that aggregation favors the cis-enol form.Control molecules HBT,HBO-2OH,and HBl-2OH show no photochromism in PU,confirming that ethanolyl branches and intramolecular OH...S hydrogen bonds stabilize the trans-enol configuration of HBT-2OH.Incorporating these molecules into PMMA and PCL networks demonstrates that increased free volume and smaller aggregates enhance photochromism by reducing resistance to dihedral angle twisting.Density functional theory(DFT)calculations further confirm stable intramolecular heteroatomic hydrogen bonds(OH..S)exist in HBT-2OH.This study offers new theoretical insights and opens avenues for research on polymer based photochromic materials.展开更多
Mechanochromic polymers based on non-covalent changes have attracted much attention recently.Herein,we report the impact of inter/intramolecular hydrogen bonds on polymer mechanochromism from the excited state intramo...Mechanochromic polymers based on non-covalent changes have attracted much attention recently.Herein,we report the impact of inter/intramolecular hydrogen bonds on polymer mechanochromism from the excited state intramolecular proton transfer (ESIPT) process.PhMz-NH2-OH and PhMz=2A are designed and obtained by simple and high-yield synthesis,and are connected into polyurethane and poly(methyl acrylate-co-2-ethylhexyl acrylate),respectively.In the initial state,the PhMz-NH2-OH@PU sample shows blue fluorescence from the excited enol form (E*) excitons,owing to intermolecular hydrogen bonds that interrupt the ESIPT reactions but the PhMz=2A@PMA-2-EA sample expresses cyan fluorescence belonging to the excited keto form (K*) emission,implying that the intramolecular hydrogen bonds matter.Furthermore,under stretching,external force can tune the emission of the PhMz=2A@PMA-2-EA sample from K* to E* state.Though external force can putatively still promote a bond rotation,ESIPT reactions remain equivalently interrupted in both the relaxed and stressed states in a hydrogen-bond donating environment.DFT calculation confirms the force-induced increase in dihedral angle for the transition of ESIPT-on/off.Thus,PhMz-NH2-OH@PU and PhMz=2A@PMA-2-EA showed disparate initial ESIPT states and further different responses/sensitivity to force.This study reports a novel and efficient strategy for enriching mechanochromic investigation and extending the applications of ESIPT reactions.展开更多
基金supported by National Key Research and Development Program of China (2020YFC0844800)the Science and Technology Planning Project of Beijing (Z201100007520006)
文摘The coronavirus disease 2019(COVID-19)pandemic has caused a surge in demand for face masks,with the massive consumption of masks leading to an increase in resource-related and environmental con-cerns.In this work,we fabricated meltblown polypropylene(mb-PP)-based high-performance planar face masks and investigated the effects of six commonly used disinfection methods and various mask-wearing periods on the reusability of these masks.The results show that,after three cycles of treatment using hot water at 70℃ for 30 min,which is one of the most scalable,user-friendly methods for viral disinfection,the particle filtration efficiency(PFE)of the mask remained almost unchanged.After mask wearing for 24 h and subsequent disinfection using the same treatment procedures,the PFE decreased to 91.3%;the average number of bacterial and fungal colonies was assessed to be 9.2 and 51.6 colony-forming units per gram(CFU∙g^(-1)),respectively;and coliform and pyogenic bacteria were not detected.Both the PFE and the microbial indicators are well above the standard for reusable masks after disinfection.Schlieren pho-tography was then used to assess the capabilities of used and disinfected masks during use;it showed that the masks exhibit a high performance in suppressing the spread of breathed air.
基金supported by the National Natural Science Foundation of China(22375013,22175015,21704002)the Beijing Natural Science Foundation(2182054)+1 种基金the Big Science Project from BUCT(XK180301)the Fundamental Research Funds forthe Central Universities to Z.Y.Ma.
文摘Excited-state intramolecular proton transfer(EsiPT)involves photochemical tautomerization between two excited states(E*and K*)via intramolecular proton transfer.Developing polymer photochromism based on the photochemical tautomerization of organic ESiPT molecules has been rarely reported.We report the ESIPT molecule HBT-2oH exhibits concentration-dependent photochromic behavior in a polyurethane(PU)network.At low concentrations,HBT-2oH primarily exists in the trans-enol configuration without intramolecular OH..N hydrogen bonds in PU,emitting blue fluorescence at~464 nm(enol emission).Upon UV irradiation,the dihedral angle between the proton donor and acceptor twists to form an intramolecular OH-.N H-bond,converting trans-enol to cis-enol and resulting in ESIPT with pale yellow fluorescence at~603 nm(keto emission).The photochromic effect of HBT-2OH@PU diminishes at high concentrations due to that aggregation favors the cis-enol form.Control molecules HBT,HBO-2OH,and HBl-2OH show no photochromism in PU,confirming that ethanolyl branches and intramolecular OH...S hydrogen bonds stabilize the trans-enol configuration of HBT-2OH.Incorporating these molecules into PMMA and PCL networks demonstrates that increased free volume and smaller aggregates enhance photochromism by reducing resistance to dihedral angle twisting.Density functional theory(DFT)calculations further confirm stable intramolecular heteroatomic hydrogen bonds(OH..S)exist in HBT-2OH.This study offers new theoretical insights and opens avenues for research on polymer based photochromic materials.
基金supported by the National Natural Science Foundationof China(22175015,21704002 and 22375013)the Beijing Natural Science Foundation(2182054)+1 种基金the Big Science Project from BUCT(XK180301)the Fundamental Research Funds forthe Central Universities to Z.Y.M.
文摘Mechanochromic polymers based on non-covalent changes have attracted much attention recently.Herein,we report the impact of inter/intramolecular hydrogen bonds on polymer mechanochromism from the excited state intramolecular proton transfer (ESIPT) process.PhMz-NH2-OH and PhMz=2A are designed and obtained by simple and high-yield synthesis,and are connected into polyurethane and poly(methyl acrylate-co-2-ethylhexyl acrylate),respectively.In the initial state,the PhMz-NH2-OH@PU sample shows blue fluorescence from the excited enol form (E*) excitons,owing to intermolecular hydrogen bonds that interrupt the ESIPT reactions but the PhMz=2A@PMA-2-EA sample expresses cyan fluorescence belonging to the excited keto form (K*) emission,implying that the intramolecular hydrogen bonds matter.Furthermore,under stretching,external force can tune the emission of the PhMz=2A@PMA-2-EA sample from K* to E* state.Though external force can putatively still promote a bond rotation,ESIPT reactions remain equivalently interrupted in both the relaxed and stressed states in a hydrogen-bond donating environment.DFT calculation confirms the force-induced increase in dihedral angle for the transition of ESIPT-on/off.Thus,PhMz-NH2-OH@PU and PhMz=2A@PMA-2-EA showed disparate initial ESIPT states and further different responses/sensitivity to force.This study reports a novel and efficient strategy for enriching mechanochromic investigation and extending the applications of ESIPT reactions.
