Polymeric assembled nanoparticles through kinetic stabilization by confined impingement jets dilution mixer for fluorescence switching imaging

Traditional fluorescence switching molecules achieving the state change between on and off states commonly based on UV irradiation. However, it is worth noting that UV irradiation is harmful to both the cancer cells and the normal cells. To achieve fluorescence switching under visible wavelength and avoid complicate molecular design, a fluorophore of 2,4,5,6-tetrakis(carbazol-9-yl)-1,3-dicyanobenzene(4Cz IPN) and a quencher of diarylethene(DAE) were physically incorporated within the biocompatible block copolymer poly(lactic-co-glycolic acid)-b-poly(ethylene glycol)(PLGA-b-PEG) to form 4Cz IPNDAE nanoparticles(NPs) through flash nanoprecipitation(FNP). By using the FNP method, the NPs were prepared within milliseconds in a confined impingement jets dilution(CIJ-D) mixer. Quenching and recovery of fluorescence could achieve in the presence of DAE under 475 nm and 560 nm irradiation.Appropriate structure and fluorescent properties of the nanoparticles can be tuned by external conditions for their efficient fluorescence resonance energy transfer(FRET) in a kinetic stabilization process. This NPs formation process was further optimized by varying the dilution ratio, Reynolds number(Re) and polymer concentration to modulate the mixing and particle nucleation and growth process. The size and fluorescence switching properties of the NPs were systematically investigated in solution and in cellular uptake experiments. This work is anticipated to provide a simple and highly effective engineering strategy for the modulation of fluorescence switching nanoparticles and beneficial to its engineering application.

Research on the Outdoor Activities and Spatial Characteristics of the Elderly in College Communities:Taking a University in Northern China as an Example

In view of the aging population in the country,college communities can better meet the needs of the elderly in the community by developing hardware facilities,environmental resources,and management systems.However,in China,the research on elderly care in colleges is still in its infancy.The paper presents an analysis on the characteristics of the elderly group,outdoor activities,and space characteristics in college communities through the field survey of a university in the north,questionnaire survey and interview with the elderly.Suggestions for optimizing the outdoor activities space of the elderly in college communities are then provided,hoping to provide some reference for relevant research.

Elucidating and manipulating pressure-induced water intrusion–extrusion in tunable hydrophobic Co/Zn bimetallic ZIFs:Roles of pore size and hydrogen bond

Porous heterogeneous lyophobic systems(HLSs)find potential applications in energy restoring,dissipating,and absorbing.However,the development of controllable HLSs still lacks rational structure design of nanoporous materials matching the molecular sizes of adopted liquids.Besides that,thoroughly understanding the underlying transportation mechanism in the confined nano channels is greatly challenging.In this work,a series of Co/Zn bimetallic zeolitic imidazolate frameworks(ZIFs)with tunable structures were synthesized via regulating the Co to Zn ratios and employed to investigate the intrusion–extrusion of liquid water in confined nanopores.Structural characterizations confirm the heterometallic coordination in the Co/Zn-doped frameworks.Water intrusion–extrusion experiments unlock the relationship between the intrusion pressure and the nanopore size and realize the evolution of the HLSs between molecular spring and shock-absorber.In addition,cycling tests indicate the reversible structure change of Co/Zn ZIFs encountering pressure-induced water intrusion.In combination with molecular dynamics simulations,we present that the water multimers intrude into nanopores of ZIFs in chain-like forms along with dissociation of hydrogen bonds(HBs).Water molecules in the pre-intrusion state exhibit reduced HBs in response to the increase of pressure and linear structure with 1.6–3.0 HBs on average.After transition to the post-intrusion situation,the associative configuration of water tends to exhibit the tetrahedral structure.Herein,we highlight the roles of pore size and HB in synergically dominating the pressure-induced intrusion–extrusion of liquid water in hydrophobic nanopores.Furthermore,the present work can also guide the development of functional guest–host systems based on porous architectures.