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.

Boosted Storage Kinetics in Thick Hierarchical Micro-Nano Carbon Architectures for High Areal Capacity Li-Ion Batteries

A practical and effective approach to increase the energy storage capacity of lithium ion batteries(LIBs)is to boost their areal capacity.Developing thick electrodes is one of the most crucial ways to achieve high areal capacity but limited by sluggish ion/electron transport,poor mechanical stability,and high-cost manufacturing strategies.Here we address these constraints by engineering a unique hierarchical-networked 10 mm thick all-carbon electrode,providing a scalable strategy to produce high areal capacity LIB electrodes.The hierarchical-networked structure utilizes micrometer-sized carbon fibers(MCFs)as building blocks,nano-sized carbon nanotubes(CNTs)as good continuous network with excellent electrical conductivity,and pyrolytic carbon as the binder and active material with excellent storage capacity.The combination of the above features endows our HNT-MCF/CNT/PC electrode with excellent performance including high reversible capacity of 15.44 mAh cm^(-2) at 2.0 mA cm^(-2) and exhibits excellent rate capability of 2.50 mAh cm^(-2) under 10.0 mA cm^(-2) current density.The Li-ion storage mechanism in HNT-MCF/CNT/PC involves dual-storage mechanism including intercalation and surface adsorption(pseudocapacitance)confirmed by the cyclic voltammetry and symmetric cell analysis.This work provides insights into the construction of high mechanical stability thick electrode for the next generation high areal capacity LIBs and beyond.

Enhancing hydrolytic stability of dynamic imine bonds and polymers in acidic media with internal protecting groups

Imine bonds are among the most explored building motifs in dynamic chemistry,polymers,and materials,and yet,their acid-resistance remains a longstanding issue.Herein we demonstrate a concept of internal protecting groups for improving the kinetic stability of dynamic imine bonds and polymers.Systematic examination of structure-reactivity relationship of a series of aldehydes/imines bearing a neighboring carboxyl allowed uncovering of required structural features for dynamically masking imine bonds with cyclic structures.Mechanistic studies indicated that noncovalent interactions along with sterics control the ringchain equilibrium and the stability of imine bonds.The incorporation of internal protecting groups into imine polymers further enabled their controlled stability in acidic media.Moreover,a combination of dynamic covalent network and coordination supramolecular network provided a facile means for the modulation of luminescent and mechanical properties of polymers.The strategies and results reported should be beneficial to molecular assemblies,dynamic polymers,biological delivery,and intelligent materials.

Geometric and Electronic Properties of Highly Fluorinated Fullerene C74F38

Geometric and electronic properties of highly fluorinated fullerene C74F38 have been studied using the density functional theory at BLYP level with the double numerical atomic orbital basis sets with polarization functions （DNP）. The optimized geometry of C74F38, quite different from that of C74, turns into a pronounced hexahedron shape because the six stabilizing isolated benzenoid rings tend to be as far apart as possible. The HOMO-LUMO energy gap and the binding energy of C74F38 indicate that C74F38 is not only kinetically but also dynamically stable. The shorter F-C bond lengths together with the analysis of the density of states and the Mulliken populations indicate that the F-C bonds in C74F38 have both covalent and ionic characters. The Mulliken populations show that the fluorine atoms obtain about 10 electrons from the C74 cage.

Transient Chemical Activation of Covalent Bonds for Healing of Kinetically Stable and Multifunctional Organohydrogels

It remains a great challenge to balance the kinetic stability and intrinsic healing ability of polymer materials.Here,we present an efficient strategy of using a synthetic reaction cycle to regulate the intrinsic healing ability of thermodynamically stable and kinetically inert multifunctional organohydrogels.By combining a double decomposition reaction with spontaneous energy dissipation,we can construct the simplest synthetic reaction cycle that can induce a transient out-of-equilibrium state for achieving the healing of organohydrogels with kinetically locked acylhydrazone bonds.In addition to balancing kinetic stability and healing ability,the synthetic reaction cycle also enables the polymer materials to have high tolerance to organic solvents,high ionic strength,high and low temperatures,and other harsh conditions.Therefore,the kinetically stable and healable organohydrogels remain mechanically flexible and electrically conductive even down to−40°C and are readily recyclable.The integration of chemical networks into healable polymers may provide novel,versatile materials for building next-generation electronic devices.

Adiabatic Decomposition of Two Kinds of Organic Peroxides by Accelerating Rate Calorimeter

The accelerating rate calorimeter was applied to study the thermal hazard of two kinds of organic peroxides, i.e. methyl ethyl ketone peroxide (MEKPO) and benzoyl peroxide (BPO). And their thermal decomposition characteristics were discussed. Meanwhile, thermal decomposition characteristics of MEKPO and BPO vvere compared. The result indicated that MEKPO is more sensitive to thermal effect than BPO. While once the thermal decomposition takes place. BPO will be more hazardous than MEKPO due to its serious pressure effect. Thermal kinetic analysis of these two kinds of organic peroxides was also taken, and the kinetic parameters for them were calculated. The study of thermal decomposition of MEKPO solution with different initial concentrations indicated that, the lower concentration MEKPO solution is, the higher onset temperature will be. And with the addition of organic solvent, it becomes more difficult for MEKPO to reach a thermal decomposition. Therefore, its thermal hazard is reduced.

Enhanced carbon dioxide adsorption performance and kinetic study of K and Al co-doped Li4SiO4

Herein, we report the effects of doped K and Al on the carbon dioxide （CO2） adsorption performance of the Li4SiO4-based adsorbents. The CO2 adsorption capacity of 0.8 wt% K and 1.5 wt% AI doped Li4SiO4 is ～2.2 times and ～1.3 times higher than that of the pristine Li4SiO4 at 500 and 600℃, respectively. The kinetic study further indicated that the reaction rates of the lithium diffusion process is greatly improved by K and AI doping, and the lithium diffusion rate of 0.8 wt% K and 1.5 wt% AI doped Li4SiO4 is ～2 times higher than that of the pristine Li4SiO4 at 575-650 ℃. K and AI doping increases the adsorption capacity of Li4SiO4-based adsorbents, and widens its effective adsorption temperature range

Effects of Ni on austenite stability and fracture toughness in high Co-Ni secondary hardening steel

Three kinds of high Co Ni secondary hardening steels with different Ni contents were studied. The nanoscale austenite layers formed at the interface of matensite laths were observed. Both observation and diffusion kinetic simulation results showed that both Ni and Co did not obtain enough time to get the equilibrium content in this system. The Ni content in austenite layers decreased significantly, and Co content increased slightly with the decrease of Ni content in overall composition. The austenite stability was estimated by Olson-Cohen model, in which both chemical and mechanical driving force could be calculated by equilibrium thermodynamic and Mohr＇s circle methods, respectively. Simulation and mechanical test results showed that The decrease of Ni content in austenite layers would cause the change of austenite stability and decrease the fracture toughness of the steels. When the Ni content in the overall composition was lower than 7 wt. %, the Ni content in y phase would be lower than 20 wt.%. And the simulation value of M; （stress induced critical martensite transformation temperature） would be up to 80 ℃, which was about 60℃ higher than room temperature. Based on the analysis, the Ni content in the overall composition of high Co Ni secondary hardening steels should be higher than 8 wt. % in order to obtain a good fracture toughness.

Lateral dipole moments induced by all-cis-pentafluorocyclohexyl groups cause unanticipated effects in self-assembled monolayers

All-cis-hexafluoro-and all-cis-pentafluoro-cyclohexane(PFCH)derivatives are new kinds of materials,the structures and properties of which are dominated by the highly dipolar Janus-face motif.Here,we report on the effects of integrating the PFCH groups into self-assembled monolayers(SAMs)of alkanethiolates on Au(111).Monolayers with an odd(eleven)and even(twelve)number of methylene groups were characterized in detail by several complementary experimental tools,supported by theoretical calculations.Surprisingly,all the data show a high similarity of both kinds of monolayers,nearly lacking the typically observed odd-even effects.These new monolayers have a packing density about 1/3 lower than that of non-substituted alkanethiolate monolayers,caused by the bulkiness of the PFCH moieties.The orientations of the PFCH groups and the alkyl chains could be determined independently,suggesting a conformation similar to the one found in the solid state structure of an analogous compound.Although in the SAMs the PFCH groups are slightly tilted away from the surface normal with the axial fluorine atoms pointing downwards,most of the dipole moments of the group remain oriented parallel to the surface,which is a unique feature for a SAM system.The consequences are much lower water contact angles compared to other partly fluorinated SAMs as well as rather moderate work function values.The interaction between the terminal PFCH moieties results in an enhanced stability of the PFCH-decorated SAMs toward exchange reaction with potential molecular substituents in spite of the lower packing density of these films.

Study on electrochemical property of La_(0.75)Mg_(0.25)Ni_(2.85)Co_(0.45–x)(AlSn)_x (x=0.0,0.1,0.2,0.3) alloys

La_（0.75）Mg_（0.25）Ni_（2.85）Co_（0.45–x）（AlSn）_x（AlSn）_x（x=0.0,0.1,0.2,0.3） alloys were prepared by magnetic induction melting method, and the phase composition and electrochemical properties were investigated systematically. The alloys were mainly composed of LaNi5, La2Ni7 and LaNi3 phase, and the cell volume of LaNi5 increased with the Al and Sn contents. For the alloy corresponding to x=0.0, the Cmax and C150 were 348.9 and 185 mA h/g, respectively, then for the alloy electrode with x=0.2, even though the Cmax was only 309.0 mA h/g less than 348.9 mA h/g, the C150 of 231 mA h/g was much higher than 185 mA h/g. And the values of the limit current density, anodic peak current density and hydrogen diffusion coefficient of the La0.75Mg0.25Ni2.85Co0.35（AlS n）0.1（x=0.1） alloy were 1079.5, 1023.8 mA /g and 5.71×10–10 cm2/s, respectively. Which were the highest than that of any other electrodes. These results suggested that the kinetic property of the La_（0.75）Mg_（0.25）Ni_（2.85）Co_（0.45–x）（AlSn）_x（AlSn）_x（x=0.0, 0.1, 0.2, 0.3） electrodes could be improved effectively by adding moderate contents of Al and Sn.