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1.
Artigo em Inglês | MEDLINE | ID: mdl-32077675

RESUMO

BACKGROUND: Long-term data are scarce regarding the efficacy of extended repair for acute type A aortic dissection (ATAAD) using frozen elephant trunk and total arch replacement (FET + TAR) technique. We seek to evaluate our single-center experience with the FET + TAR technique in patients with ATAAD, focusing on early and long-term survival and reoperation. METHODS: The early and long-term outcomes of FET + TAR were analyzed for 518 patients with ATAAD operated on between April 2003 and December 2012. Mean age 46.2 ± 10.5 years and 426 were male (82.2%). Malperfusion occurred in 66 (12.7%) and Marfan syndrome (MFS) in 51 (9.8%). Bentall procedure was performed in 153 (29.5%), aortic cusp resuspension in 82 (15.8%), root remodeling (uni- or bi-Yacoub) in 19 (3.7%), ascending aortic replacement in 22 (4.2%) and extra-anatomic bypass in 15 patients (2.9%). The times of cardiopulmonary bypass time (CPB), cross-clamp and selective antegrade cerebral perfusion were 201 ± 50, 112 ± 34, and 26 ± 10 minutes, respectively. RESULTS: Operative mortality rate was 7.5% (39/518). Spinal cord injury occurred in 2.5% (13/518), stroke in 2.9% (15/518), reexploration for bleeding in 2.5% (13/518) and acute kidney injury in 4.6% (24/518). Early reintervention with thoracic endovascular aortic repair (TEVAR) was performed in 3 (0.6%). Follow-up was complete in 98.7% (473/479) at mean 9.0 ± 4.8 years (range 0.2-16.2). Late death occurred in 74, distal dilation in 31 and distal new entry in 9 patients. Late reoperation was performed in 31 patients, including TEVAR in 12, thoracoabdominal aortic replacement in 9, abdominal aortic replacement in 2, anastomotic leak repair in 5. Survival and freedom from distal reoperation were 77.3% (95% confidence interval [CI] 72.9-81.1%) and 69.8% (95% CI 63.4-75.3%), and 92.9% (95% CI 89.9-95.0%) and 92.9% (95% CI 89.9-95.0%) at 10 and 15 years, respectively. Competing risks analysis showed that at 12 years, the incidence was 28.0% for death, 8.5% for distal reoperation, and 63.5% of patients were alive without reoperation. Multivariable analyses found that CPB time (in minutes) (odds ratio [OR], 1.011; 95% CI 1.006-1.017; P < 0.001) and malperfusion syndrome (binary) (OR 2.291; 95% CI 1.283-6.650; P = 0.011) were predictive of operative mortality, while multiple malperfusion predicted late death (hazard ratio, HR 6.815; 95% CI 2.447-18.984; P < 0.001). Risk factors for late death and distal reoperation included MFS (HR, 1.824; 95% CI 1.078-3.087; P = 0.025) and malperfusion (HR, 1.787; 95% CI 1.042-3.064; P = 0.035). CONCLUSIONS: In this large series of ATAAD, the FET + TAR technique has achieved satisfactory early and long-term survival and freedom from reoperation up to 15 years. Marfan syndrome and malperfusion syndrome were risk factors for early and late mortality and distal reoperation. This study adds long-term evidence supporting the use of the FET + TAR technique in patients with ATAAD involving the arch and descending aorta.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32057078

RESUMO

OBJECTIVES: Aortic dissection (AoD) in the presence of an aberrant right subclavian artery (ARSA) is very rare. Clinical experience is limited, and there is no consensus regarding the optimal management strategy. We seek to evaluate the safety and efficacy of the total arch replacement (TAR) and frozen elephant trunk (FET) technique as an approach to AoD in patients with ARSA by retrospectively analysing our single-centre experience. METHODS: From 2009 to 2017, we performed TAR + FET for 22 patients with ARSA sustaining AoD (13 acute, 59.1%). The mean age was 46.0 years [standard deviation (SD) 8.3], and 19 patients were male (86.4%). ARSA orifice was dilated in 15 (68.2%) patients, and a Kommerall diverticulum was diagnosed in 13 (59.1%) patients with a mean diameter of 21.8 mm (SD 7.7; range 15-40). Surgery was performed via femoral and right/left carotid cannulation under hypothermic circulatory arrest at 25°C. The ARSA was reconstructed using a separate branched graft. RESULTS: ARSA was closed proximally by ligation in 16 (72.7%) patients, direct suture in 4 (18.2%) patients and both in 2 (9.1%) patients. Operative mortality was 13.6% (3/22). Type Ib endoleak occurred in 1 (4.5%) patient at 8 days. Follow-up was complete in 100% at mean 4.2 years (SD 2.0), during which 3 late deaths and 1 reintervention for type II endoleak occurred. Survival was 81.8% and 76.4% at 3 and 5 years, respectively. Freedom from reoperation was 89.2% up to 8 years. In competing risks analysis, the incidence was 22.1% for death, 10.8% for reoperation and 67.1% for event-free survival at 5 years. The false lumen, ARSA orifice and Kommerall diverticulum were obliterated in 100%. Grafts were patent in 100%. No patients experienced cerebral ischaemia and upper extremity claudication. Hypothermic circulatory arrest time (min) was sole predictor for death and aortic reintervention (hazard ratio 1.168, 95% confidence interval 1.011-1.348; P = 0.034). CONCLUSIONS: The TAR and FET technique is a safe and efficacious approach to AoD in patients with ARSA. Modifications of routine TAR + FET techniques are essential to successful repair, including femoral and right/left carotid artery cannulation, ligation of ARSA on the right side of the trachea and ARSA reconstruction with a separate graft.

3.
Sci Total Environ ; 709: 136146, 2020 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-31905585

RESUMO

Dust particulates play an essential role for the nucleation, hygroscopicity and also contribute to aerosol mass. We investigated the chemical composition, size distribution and mixing states of PM2.5 using a single-particle aerosol mass spectrometer (SPAMS), Monitor for AeRosols and Gases (MARGA), and off-line membrane sampling from 2018.1.24 to 2018.2.20 at a coastal supersite in Ningbo, a port city in Yangtze River Delta, China. During the study campaign, the eastern part of China had experienced a wide range of cooling, sandstorm, and snowfall processes. The entire sampling campaign was categorized into five sub-periods based on the levels of PM2.5 and the ratios of PM2.5/PM10, namely clean (T1), heavy pollution (T2), light pollution (T3), dust (sandstorm) (T4) and cleaning pollution (T5) period. After comparing the average mass spectrum for each period, it shows that the primary ions, such as Ca2+and SiO3-, rarely coexist with each other within a single particle, but secondary ions generally coexist with these primary ions. Furthermore, the coexistence of each two different ions within a particle does not show distinct variation for the whole study periods. All these suggest that the absorption and partitioning of gaseous contaminants into the surface of primary aerosol through heterogeneous reactions are the major pathways of aging and growth of aerosol; and the merging of particles through collisions usually is insignificant. Although the absolute concentrations of nitrate and sulfate all increased with the PM2.5 concentrations, the relative equivalent concentrations of NO3- and SO42- displayed opposite trends; the relative contribution of sulfate decreased and that of nitrate increased as the increase of pollution. During the dust period, the relative equivalent concentrations of calcium and/or potassium ions in PM2.5 are significantly higher. This study provided deep insights about the mixing states and characteristics of particulate after long-range transport and a visualization tool for aerosol study.

4.
J Am Chem Soc ; 142(6): 3069-3076, 2020 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-31971790

RESUMO

The idea of modularity in organic total synthesis has promoted the construction of diverse targeted natural products by varying the building blocks and assembly sequences. Yet its utilization has been mainly limited to the synthesis of molecular compounds based on covalent bonds. In this work, we expand the conceptual scope of modular synthesis into framework materials, which bridges metal- and covalent organic frameworks (MOFs and COFs) hierarchically in reticular chemistry. While the assembly sequences are determined by the coordination or the covalent bond strengths, a modular synthesis strategy which progressively links simple building blocks into increasingly sophisticated superstructures was reported. As a result, a series of hierarchical COF-on-MOF structures with architectural intricacy were obtained through sequence-defined reactions of diverse building blocks. The tunability of spatial apportionment, compositions, and functionality was successfully managed in these framework materials. To the best of our knowledge, this is the first report on the synthesis of COF@MOF composites and also the first discovery of controlled COF alignment. This generalizable modularity strategy will not only accelerate the discovery of multicomponent framework materials by the hierarchical assembly of MOFs and COFs but also offer a predictable retrosynthetic route to smart materials with unusual tunability owing to the diverse inorganic or organic building units.

5.
ChemSusChem ; 13(1): 205-211, 2020 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-31556474

RESUMO

The development of sustainable catalysts to simultaneously improve activity and selectivity remains a challenge. Herein, it is demonstrated that metal nanoparticles (MNPs) can be encapsulated into a yolk-shell metal-organic framework (MOF) with controllable spatial localization to optimize catalytic performance. When the MNPs are located in the void space between the shell and the core of the MOF, the resulting MNPs@MOF composites show both high catalytic activity and selectivity toward the hydrogenation of α,ß-unsaturated aldehydes. In particular, the easily recoverable and stable Ptvoid @MOF(Y) shows an exceptionally high selectivity of 98.2 % for cinnamyl alcohol at a high conversion of 97 %. The excellent performance can be attributed to easy diffusion of the reactants to access highly exposed MNPs in the MOF support, as well as the improved adsorption of the reactant and desorption of the product due to the appropriate metal-support interaction and rich void space between core and shell.

6.
Huan Jing Ke Xue ; 41(1): 65-74, 2020 Jan 08.
Artigo em Chinês | MEDLINE | ID: mdl-31854905

RESUMO

Gaseous elemental mercury (GEM) is commonly known as a hazardous heavy metal in the atmosphere and is harmful to living organisms. GEM is chemically stable and has a long residence time in the atmosphere; hence, it can be transported over long distances with air masses and is regarded as a global pollutant. We study the transportation and transformation mechanisms of GEM and its potential anthropogenic and natural contribution sources. GEM, conventional atmospheric pollutants, and meteorological parameters were monitored at a coastal site in Ningbo during the summer and autumn of 2017. The results were as follows. ① The concentrations of GEM ranged from 0.97-10.95 ng·m-3 and the mean and standard deviation (SD) were (2.32±0.90) ng·m-3, whereby the mean summer concentration was lower than the mean autumn concentration. ② The diurnal variations of GEM, ozone (O3), and gaseous oxidized mercury (GOM) during summer/autumn and sunny/rainy days suggest that higher levels of O3 and that strong solar radiation accounted for the rapid photochemical oxidation of GEM. The intensity of oxidation on sunny days was higher than that on rainy days. ③ Correlation analysis showed that GEM was significantly positively correlated with PM2.5 (R=0.65, P<0.01), PM10 (R=0.47, P<0.01), NO2 (R=0.46, P<0.01), and CO (R=0.57, P<0.01). Local and regional sources of GEM were mainly related to fossil fuel combustion. ④ The photochemical oxidation rate of GEM was influenced by the concentrations of oxidants (e.g., O3), gas-particle partitioning between GEM and particles, and light extinction effects of PM2.5, water vapor, and NO2. ⑤ Potential source contribution analysis (PSCF) indicated that the northwestern Zhejiang Province (including Ningbo City), the southern Anhui Province, and most of Jiangxi Province constitute a triangular area that is a potential source contribution to NBUEORS atmospheric GEM pollution during the summer. Local, regional, and long-range sources all had strong impacts on GEM pollution. During the autumn, the potential sources were mainly in the northern Zhejiang Province, and the source was smaller than that during the summer. GEM pollution during the autumn was mainly influenced by local and regional sources. Therefore, the control of atmospheric GEM pollution in the Yangtze River delta should apply inter-regional prevention and comprehensive control strategies in order to reduce atmospheric mercury pollution.

7.
J Hazard Mater ; 382: 121018, 2020 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-31446354

RESUMO

The broad spectrum detection of veterinary drugs is very important for rapid and large-scale safe screen of animal-derived foods. Metal-organic frameworks (MOFs), as a kind of emerged functional porous materials are quite promising in the chemical sensing and molecular detection. In this work, we report the high-performance broad spectrum detection of 15 commonly-used veterinary drugs through the fluorescence quenching in a newly-designed chemically stable Al-based MOF, Al3(µ3-O)(OH)(H2O)2(PPTTA)3/2 (BUT-22). To the best of our knowledge, this is the first systematic investigation for the application of MOFs in the detection/sensing of veterinary drugs through fluorescence quenching method. The quenching efficiencies of the tested veterinary drugs on BUT-22 are all beyond 82%, and the limits of detection (LOD) are low at parts per billion (ppb) levels. Interestingly, BUT-22 also enables the selective detection of nicarbazin (NIC) through the clearly-observed red shift of its maximum fluorescence emission wavelength. Moreover, the fluorescence quenching mechanism was explored with the help of theoretical calculations. Our work indicates that MOFs are favorable materials for the detection of veterinary drugs, being potentially useful in monitoring drug residues of animal-derived foods.

8.
Ecotoxicol Environ Saf ; 187: 109821, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31677572

RESUMO

In this study, a porous framework MOF-74(Zn) (Zn2 (DHBDC)(DMF)(H2O)2, H4dondc = 1, 5-dioxido-2, 6-naphthalenedicarboxylic acid) with open metal sites was successful synthesized. MOF-74(Zn) as a template was grafted on the open metal sites with ethylenediamine (en) named MOF-74(Zn)-en to develop a highly selective and sensitive fluorescence detector for rapid determination of tetrabromobisphenol A (TBBPA). The obtained MOF-74(Zn)-en was well characterized by Fourier Transform Infrared (FT-IR), Scanning Electron Microscopy (SEM) and showed ideal properties of photoluminescence. The fluorescence enhancement showed a good linear relationship with the concentrations of TBBPA in the range of 50-400 µg/L, and its limit of detection could reach to 0.75 µg/L. Furthermore, the possible sensing mechanism of the fluorescence enhancement could be attributed to Förster resonance energy transfer (FRET). The results will provide a convenient and quick method for detection of TBBPA. To the best of my knowledge, this is the first case to detect TBBPA by fluorescence enhancement with MOF derivatives.


Assuntos
Fluorescência , Estruturas Metalorgânicas/química , Bifenil Polibromatos/análise , Poluentes Químicos da Água/análise , Zinco/química , Etilenodiaminas/química , Limite de Detecção , Bifenil Polibromatos/química , Espectrometria de Fluorescência/instrumentação , Poluentes Químicos da Água/química
9.
Inorg Chem ; 58(23): 15909-15916, 2019 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-31725278

RESUMO

In recent years, more and more research on metal-organic frameworks (MOFs) has focused on exploring their practical applications, where the stability is crucial. Besides the metal-ligand coordination bond, the configuration of the ligand also plays an important role in determining the stability of resulting MOFs. In this work, we demonstrate that fixing flexible arms of core-shared ligands can enhance the stability of their Zr(IV)-MOFs. Two groups, four core-shared tetracarboxylate ligands, 3,3',3″,3‴-(pyrene-1,3,6,8-tetrayltetrakis(benzene-4,1-diyl))tetraacrylate (PTSA4-) and 6,6',6″,6‴-(pyrene-1,3,6,8-tetrayl)tetrakis(2-naphthoate) (PTNA4-) with the pyrene core and 3,3',3″,3‴-((9H-carbazole-1,3,6,8-tetrayl)tetrakis(benzene-4,1-diyl))-tetraacrylate (CTSA4-) and 6,6',6″,6‴-(9H-carbazole-1,3,6,8-tetrayl)tetrakis-(2-naphthoate) (CTNA4-) with the carbazole core are rationally designed. Two ligands in each group have different flexibilities due to the distinct side arms: the styrene arm is flexible, whereas the naphthalene is rigid. Constructed with Zr6 clusters, four 4,8-connected Zr(IV)-MOFs, Zr6O4(OH)8(H2O)4(PTSA)2 (BUT-72) and Zr6O4(OH)8(H2O)4(PTNA)2 (BUT-73) with a sqc-a topologic framework structure and Zr6O4(OH)8(H2O)4(CTSA)2 (BUT-74) and Zr6O4(OH)8(H2O)4(CTNA)2 (BUT-63) with a scu-a structure are obtained, respectively. It is found that the stability of BUT-73 and -63 with the rigid naphthoate-based ligands is significantly enhanced compared with that of BUT-72 and -74 with the flexible phenyl acrylate-based ones. Moreover, stable BUT-63 represents outstanding performance in the molecular recognition of most solvents commonly used in organic synthesis and industrial manufacture.

10.
ACS Appl Mater Interfaces ; 11(44): 41595-41601, 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31603301

RESUMO

A feasible strategy for the in situ growth of two-dimensional (2D) [Ni3(OH)2(1,4-BDC)2-(H2O)4]·2H2O (Ni-BDC; 1,4-BDC = 1,4-benzenedicarboxylate) and the subsequent partial sulfurization treatment for the decoration of nickle sulfide (NiS) is developed. The fabricated hierarchically structured Ni-BDC@NiS as a synergistic electrocatalyst shows extremely high activity toward the oxygen evolution reaction (OER). The optimal Ni-BDC@NiS catalyst acquires a current density of 20 mA cm-2 at a lower overpotential of 330 mV and low Tafel slope of 62 mV dec-1, outperforming most previously reported Ni-based sulfide catalysts. Clearly, the combination of the NiS and Ni-BDC array contributed to the improvement of electron transfer, promotion of water adsorption, and increase of rich active species. In addition, the in situ created hierarchical structure not only affords feasible access for mass transport but also strengthens structural integrity, contributing to efficient and stable OER performance. This general and effective strategy anchoring conductive active species on a porous metal-organic framework (MOF) thus provides an efficient way to fabricate synergistic electrocatalysts for the OER.

11.
J Clin Med ; 8(11)2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31652955

RESUMO

We aimed to investigate the association of gut microbiota with disease activity, inflammatory parameters, and auto-antibodies profile in rheumatoid arthritis (RA). A total of 138 RA patients and 21 healthy controls (HC) were enrolled. Fecal samples were collected for bacterial DNA extraction and 16S ribosome (r)RNA sequencing, followed by analyses of gut microbiota composition. Serum levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-17A were determined by using ELISA. Our results indicated that RA patients had lower diversity index, which reflects both evenness and richness of gut microbiota, compared to HC. The alpha-diversity was lower in anti-citrullinated peptide antibodies (ACPA)-positive patients than in HC. The phylum Verrucomicrobiae and genus Akkermansia were more abundant in patients compared to HC. There was increased relative abundance of Enterobacteriaceae as well as Klebsiella, and less abundance of Bifidobacterium in patients with high levels of TNF-α or IL-17A compared to those who had low levels of these cytokines. In addition, ACPA-positive patients had higher proportions of Blautia, Akkermansia, and Clostridiales than ACPA-negative patients. Gut dysbiosis in RA patients was presented as different microbial composition and its association with inflammatory parameters as well as ACPA seropositivity. These findings support the involvement of gut microbiota in RA pathogenesis.

12.
Ann Thorac Surg ; 2019 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-31494136

RESUMO

BACKGROUND: This study sought to evaluate the long-term impact of frozen elephant trunk (FET) on the distal aorta of patients with Marfan syndrome (MFS) who had type I dissection confined to the thoracic aorta (above the diaphragmatic hiatus). METHODS: Between 2003 and 2016, 42 patients with MFS (Ghent or revised Ghent criteria) (age 33.3 ± 8.9 years; 27 men; 64.3%) sustaining type I dissection above the diaphragmatic hiatus involving the aortic arch (22 acute; 52.4%) underwent total arch replacement and FET. Dissection extended distally to the mid-descending aorta in 32 (76%) and to above the diaphragmatic hiatus in 10 (24%) patients. Operative mortality was 4.8% (2 of 42). Follow-up was 100% at 6.3 ± 3.0 years. RESULTS: Maximal aortic sizes at the mid-descending aorta, diaphragmatic hiatus, renal arteries, and largest segment of abdominal aorta were 22.8, 21.1, 19.1, and 19.9 mm preoperatively and 23.1, 22.0, 19.8, and 22.4 mm on the latest computed tomographic angiography. Dilation and complete remodeling of the distal aorta occurred in 10.0% (4 of 40) and 90% (36 of 40) of patients, respectively. One late death occurred, and 3 distal reoperations were performed. Preoperative abdominal aortic maximal aortic size was predictive of distal dilatation (mm) (hazard ratio, 1.78; P = .021) and reoperation (≥25 mm vs <25 mm) (hazard ratio, 12.88; P = .037). At 10 years, freedom from dilation, reoperation, and death were 69.8%, 78.1%, and 90.0%, respectively. At 8 years, the rates of death, reoperation, and reoperation-free survival were 10%, 11%, and 79%, respectively. CONCLUSIONS: The FET technique has a positive remodeling impact on type I dissection confined to the thoracic aorta in patients with MFS. This study adds evidence supporting the safety and durability of this extended approach for type I aortic dissection in MFS.

13.
Nat Commun ; 10(1): 3861, 2019 08 27.
Artigo em Inglês | MEDLINE | ID: mdl-31455843

RESUMO

Polychlorinated dibenzo-p-dioxins (PCDDs), as a class of persistent and highly toxic organic pollutants, have been posing a great threat to human health and the environment. The sensing of these compounds is important but challenging. Here, we report a highly stable zirconium-based metal-organic framework (MOF), Zr6O4(OH)8(HCOO)2(CPTTA)2 (BUT-17) with one-dimensional hexagonal channels and phenyl-rich pore surfaces for the recognition and sensing of two representative PCDDs, 2,3-dichlorodibenzo-p-dioxin (BCDD) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), based on the fluorescence quenching. BUT-17 exhibits high sensing ability with the detection limits as low as 27 and 57 part per billion toward BCDD and TCDD, respectively, and is very selective as well without the interference of similar compounds. The recognition of BUT-17 toward BCDD is demonstrated by single-crystal structure of its guest-loaded phase, in which the fluorescence-quenched complexes form between the adsorbed BCDD molecules and the MOF host through π-π stacking and hydrogen bonding interactions.


Assuntos
Poluentes Ambientais/análise , Estruturas Metalorgânicas/química , Dibenzodioxinas Policloradas/análise , Zircônio/química , Poluentes Ambientais/química , Fluorescência , Dibenzodioxinas Policloradas/química
14.
Dalton Trans ; 48(36): 13541-13545, 2019 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-31469147

RESUMO

Simultaneously involving abundant [NH2(CH3)2]+ cations and uncoordinated carboxylate oxygen atoms as dual active sites, two microporous CoII-MOFs (LCU-105 and LCU-106, LCU = Liaocheng University) both exhibit highly selective adsorption of CO2/CH4 and CO2/N2. GCMC theoretical simulations provide good verification of the experimental results.

16.
Chem Rev ; 119(18): 10638-10690, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31361477

RESUMO

Food safety is a prevalent concern around the world. As such, detection, removal, and control of risks and hazardous substances present from harvest to consumption will always be necessary. Metal-organic frameworks (MOFs), a class of functional materials, possess unique physical and chemical properties, demonstrating promise in food safety applications. In this review, the synthesis and porosity of MOFs are first introduced by some representative examples that pertain to the field of food safety. Following that, the application of MOFs and MOF-based materials in food safety monitoring, food processing, covering preservation, sanitation, and packaging is overviewed. Future perspectives, as well as potential opportunities and challenges faced by MOFs in this field will also be discussed. This review aims to promote the development and progress of MOF chemistry and application research in the field of food safety, potentially leading to novel solutions.

17.
J Am Chem Soc ; 141(26): 10283-10293, 2019 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-31180667

RESUMO

Metal-organic frameworks (MOFs) have been developing at an unexpected rate over the last two decades. However, the unsatisfactory chemical stability of most MOFs hinders some of the fundamental studies in this field and the implementation of these materials for practical applications. The stability in a MOF framework is mostly believed to rely upon the robustness of the M-L (M = metal ion, L = ligand) coordination bonds. However, the role of organic linkers as agents of stability to the framework, particularly the linker rigidity/flexibility, has been mostly overlooked. In this work, we demonstrate that a ligand-rigidification strategy can enhance the stability of MOFs. Three series of ligand rotamers with the same connectivity but different flexibility were prepared. Thirteen Zr-based MOFs were constructed with the Zr6O4(OH4)(-CO2) n units ( n = 8 or 12) and corresponding ligands. These MOFs allow us to evaluate the influence of ligand rigidity, connectivities, and structure on the stability of the resulting materials. It was found that the rigidity of the ligands in the framework strongly contributes to the stability of corresponding MOFs. Furthermore, water adsorption was performed on some chemically stable MOFs, showing excellent performance. It is expected that more MOFs with excellent stability could be designed and constructed by utilizing this strategy, ultimately promoting the development of MOFs with higher stability for synthetic chemistry and practical applications.

18.
Mikrochim Acta ; 186(7): 454, 2019 06 14.
Artigo em Inglês | MEDLINE | ID: mdl-31201535

RESUMO

A metal organic framework (MOF) based adsorbent of type UiO-66 was hydrothermally prepared and applied to simultaneous sensing and removal of the asthma drug clenbuterol. The MOF possesses a large specific surface area (1460 cm2·g-1) and a stable structure, and has a large adsorption capacity for clenbuterol (160 mg·g-1). If clenbuterol binds to the MOF, the fluorescence of the sorbent (best measured at excitation/emission wavelengths of 290/396 nm) is quenched by up to 88%. Based on these findings, a fluorometric assay has been developed for the rapid determination of clenbuterol. The adsorption equilibrium of UiO-66 for CLB can be achieved at 60 min and the adsorption efficiency is above 80%. The method has a linear response in the 4.0 to 40 ng·mL-1 concentration range, and the lower limit of detection is 0.17 µM. All of this indicates that UiO-66 is promising for simultaneous detection and the removal of CLB in water. Graphical abstract Schematic presentation of the detection and removal of clenbuterol in water medium by a stable fluorescent Zr(IV)-based metal organic framework. This method exhibited a large adsorption capacity for clenbuterol (160 mg/g) and low limit of detection (0.17 µM).

19.
Dalton Trans ; 48(25): 9225-9233, 2019 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-31161164

RESUMO

The formation of metal-organic frameworks (MOFs) under given reaction conditions depends on various factors including reaction duration, temperature, used solvent, system pH, and others. Among them, the reaction duration is relatively less investigated. In this work, based on a Cu(ii)-MOF system, the reaction duration was found to play an important role in directing the formation of two different products, (NH2(CH3)2)[Cu12(DDPN)6(H2O)10Cl] (BUT-301) on shorter reaction time and (NH2(CH3)2)2[Cu(DDPN)] (BUT-302) on longer reaction time, when CuCl2 reacted with 3,5-di(3,5-dicarboxylphenyl)nitrobenzene (H4DDPN) in a DMA/MeOH mixed solvent at 120 °C. With increasing the reaction duration, BUT-301 can transform into BUT-302. Both MOFs have three-dimensional (3D) framework structures. BUT-301 is constructed from paddle-wheel Cu2(COO)4 units and DDPN4- ligands as four-connected linkers, while BUT-302 is assembled from mononuclear Cu(ii) centers connecting the ligands as also four-connected linkers but in a monodentate coordination fashion. N2 adsorption confirmed that both MOFs are porous materials with the Brunauer-Emmett-Teller (BET) surface areas of 1953 and 561 m2 g-1, respectively. Interestingly, both BUT-301 and -302 show selective adsorption properties of C3H4 over C3H6. The C3H4/C3H6 adsorption selectivities were calculated to be 1.9 and 4.4 at 0.1 bar and 298 K by the ideal adsorbed solution theory (IAST) for a 1 : 99 C3H4/C3H6 mixture, respectively.

20.
J Sci Food Agric ; 99(11): 5083-5091, 2019 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-31066054

RESUMO

BACKGROUND: The effect of ultrasonic thawing (0, 160, 280, 400 W) on water-holding capacity (WHC), physicochemical properties and structure of tuna myofibrillar proteins was investigated. RESULTS: Thawing time was shown to decrease and thawing loss to increase significantly (P < 0.05) as power increased (160-400 W), whereas there was no significant difference (P > 0.05) in cooking loss. Changes in T2 relaxation time were investigated using low-field nuclear magnetic resonance. Ultrasonic thawing could significantly (P < 0.05) improve the immobilised water content compared to the control (0 W). surface hydrophobicity decreased significantly and then increased significantly (P < 0.05), whereas there was no significant difference (P > 0.05) in the reactive sulfhydryl content as power was increased. Tuna thawed at 280 W suffered fewer negative effects on its microstructure. Roman spectral date showed that the α-helix changed to a random coil and ß-turn as power was increased (up to 400 W). CONCLUSION: The application of ultrasonic thawing at a specified power was showed to be a beneficial process when used in the seafood industry, but application of excessive power resulted in lower WHC and structural changes to myofibrillar proteins. © 2019 Society of Chemical Industry.


Assuntos
Manipulação de Alimentos/métodos , Carne/análise , Proteínas Musculares/química , Atum , Ultrassom/métodos , Água/análise , Animais , Congelamento , Interações Hidrofóbicas e Hidrofílicas
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