A high-throughput sonochemical synthesis and testing strategy was developed to discover covalent organic frameworks (COFs) for photocatalysis. In total, 76 conjugated polymers were synthesized, including 60 crystalline COFs of which 18 were previously unreported. These COFs were then screened for photocatalytic hydrogen peroxide (H2O2) production using water and oxygen. One of these COFs, sonoCOF-F2, was found to be an excellent photocatalyst for photocatalytic H2O2 production even in the absence of sacrificial donors. However, after long-term photocatalytic tests (96 h), the imine sonoCOF-F2 transformed into an amide-linked COF with reduced crystallinity and loss of electronic conjugation, decreasing the photocatalytic activity. When benzyl alcohol was introduced to form a two-phase catalytic system, the photostability of sonoCOF-F2 was greatly enhanced, leading to stable H2O2 production for at least 1 week.
The introduction of a dual-functional interlayer into lithium−sulfur batteries (LSBs) provides many opportunities for restraining the "shuttle effect" and enhancing sluggish sulfur conversion kinetics. Tuning the band structure of the metal sulfide provides an opportunity to enhance its catalytic activity, which plays an important role in suppressing the "shuttle effect" of lithium polysulfides (LiPSs) in LSBs.Here were present a Co 9 S 8 @MoS 2 core−shell heterostructure anchored to a carbon nanofiber (Co 9 S 8 @MoS 2 /CNF), developed as an interlayer for suppressing the shuttle effect of LiPSs. The fabricated composite heterostructure is determined to be an effective alternative material that combines the synergistic relationship between chemisorption and electrochemical catalysis. We find that the band structure of the MoS 2 shell can be effectively tuned by the Co 9 S 8 core and that the Co 9 S 8 @MoS 2 /CNF can capture the LiPSs, providing excellent catalytic ability to convert LiPSs into Li 2 S 2 , with subsequent transformation from Li 2 S 2 to Li 2 S. Importantly, high capacities of 1002 and 986 mAh g −1 can be retained after 50 cycles with high-sulfur loadings of 6 and 10 mg cm −2 . Our results highlight the design of an atomic-scale heterostructure as a multifunctional interlayer providing a synergistic relationship between adsorption and catalysis. The net result is an effective retardation of the shuttling of LiPSs and an enhancement of the electrochemical redox reactions of LiPSs. This work shows great promise toward the development of practical applications of LSBs.
Abstract. Generations 5 and 6 (G5 and G6) poly(amidoamine) (PAMAM) dendrimers have been shown to be highly efficient nonviral carriers in in vitro gene delivery. However, their high toxicity and unsatisfied in vivo efficacy limit their applications. In this study, to improve their characteristics as gene delivery carriers, polyethylene glycol (PEG, molecular weight 5,000) was conjugated to G5 and G6 PAMAM dendrimers (PEG-PAMAM) at three different molar ratios of 4%, 8%, and 15% (PEG to surface amine per PAMAM dendrimer molecular). Compared with unconjugated PAMAM dendrimers, PEG conjugation significantly decreased the in vitro and in vivo cytotoxicities and hemolysis of G5 and G6 dendrimers, especially at higher PEG molar ratios. Among all of the PEG-PAMAM dendrimers, 8% PEG-conjugated G5 and G6 dendrimers (G5-8% PEG, G6-8% PEG) resulted in the most efficient muscular gene expression when polyplexes were injected intramuscularly to the quadriceps of neonatal mice. Consistent with the in vivo results, these two 8% PEG-conjugated PAMAM dendrimers could also mediate the highest in vitro transfection in 293A cells. Therefore, G5-8% PEG and G6-8% PEG possess a great potential for gene delivery both in vivo and in vitro.
rystalline covalent organic frameworks (COFs) have received much attention because of their use in catalysis, adsorption, separation, chemosensing, drug delivery and energy storage and production [1][2][3] . The traditional route to COFs is solvothermal synthesis 4 , but this often requires the use of sealed, pressurized tubes, elevated reaction temperatures (120-200 °C), long reaction times (2-7 days) and toxic organic solvents. These drawbacks provide an incentive to develop alternative methods to synthesize COFs.Alternatives to solvothermal syntheses include microwave synthesis 5 and room-temperature syntheses using catalysts 6,7 . These routes can be much faster than solvothermal syntheses, with reaction times of 1-2 h. However, it is still desirable to avoid the use of toxic organic solvents and metal catalysts. Solid-state synthesis is one route that eliminates bulk solvent use and reduces waste generation. p-Toluenesulfonic acid, a strong solid acid, was first used as the catalyst for solid-state COF synthesis by Kandambeth et al. 8 . However, a large quantity of p-toluenesulfonic acid (~6 molar equiv. based on the amine monomers) was required during the synthesis, and high temperatures (90-170 °C) for one minute to two days were needed to obtain the crystalline COFs 9,10 . Mechanochemical synthesis is another promising solid-state route. The first examples of COF mechanosynthesis were reported by Biswal et al. 11 . Solvent-free mechanochemical processes offer the potential for large-scale COF synthesis, but such studies are rare and the COFs produced have limited crystallinity and porosity 12 . For example, the mechanically synthesized COFs TpPa-1, TpPa-2 and TpBD had only moderate crystallinity and low Brunauer-Emmet-Teller (BET) surface areas (61 m 2 g -1 for TpPa-1, 56 m 2 g -1 for TpPa-2 and 35 m 2 g -1 for TpBD) compared with those of their solvothermal analogues 11 . Recent work by Emmerling et al. 13 showed that alternative activation methods, such as supercritical CO 2 drying 14,15 , may allow access to the porosity of mechanochemically prepared COFs.
Objectives‘National Special Stewardship in the Clinical Use of Antibiotics’ was put forward in July 2011 in China. We aimed to retrospectively evaluate the impact of antimicrobial stewardship (AMS) managed by clinical pharmacists on antibiotic utilisation, prophylaxis and antimicrobial resistance (AMR).DesignThis was a retrospective observational study of trends in antibiotic use and AMR in the context of AMS.SettingBeijing Chaoyang Hospital, a 1400-bed tertiary hospital, in China.Data and participantsAntibiotic prescriptions from 820 doctors included all outpatients (n=17 766 637) and inpatients (n=376 627) during 2010–2016. Bacterial resistance data were from all inpatients (n=350 699) during 2011–2016.InterventionsMultiaspect intervention measures were implemented by clinical pharmacists (13 persons), for example, formulating the activity programme and performance management, advising on antibacterial prescriptions and training.Outcome measuresThe proportion of antibiotic prescriptions among outpatients and inpatients, intensity of consumption in defined daily dose (DDD)/100 bed-days, antibiotic prophylaxis in type I incision operations and resistance rates ofEscherichia coli,Klebsiella pneumoniaeandPseudomonas aeruginosawere retrospectively analysed.ResultsThe proportion of antibiotic prescriptions decreased in outpatients (from 19.38% to 13.21%) and in inpatients (from 64.34% to 34.65%), the intensity of consumption dropped from 102.46 to 37.38 DDD/100 bed-days. The proportion of antibiotic prophylaxis decreased from 98.94% to 18.93%. The proportion of rational timing of initial dose increased from 71.11% to 96.74%, the proportion of rational duration rose from 2.84% to 42.63%. Time series analysis demonstrated the resistance rates ofE. coliandP. aeruginosato fluoroquinolones decreased, the incidence rate of methicillin-resistantStaphylococcus aureusalso decreased, whereas the resistance rates ofE. coliandK. pneumoniaeto carbapenems increased. The antibiotic use was partly positively correlated with AMR.ConclusionsAMS had an important role in reducing antibiotic use and surgical antibiotic prophylaxis. The AMR was positively correlated with antibiotic consumption to some extent.
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