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1.
Huan Jing Ke Xue ; 41(4): 1770-1778, 2020 Apr 08.
Artigo em Chinês | MEDLINE | ID: mdl-32608684

RESUMO

In this study, watermelon rind was used as a raw material to modify watermelon rind biochar (MBC) with ammonium sulphate[(NH4)2S] for adsorption of Pb(Ⅱ) ions. The effects of solution pH, adsorption time, adsorbent addition amount, initial mass concentration of Pb(Ⅱ) ions, and ionic strength on the adsorption of Pb(Ⅱ) ions were investigated. The results show that the saturated adsorption time was 5 h, the optimum pH of the adsorption reaction was 6, and when the initial mass concentration of Pb(Ⅱ) ions were 1000 mg·L-1, and the amount of adsorbent was 2.0 g·L-1. The maximum adsorption amount of MBC to Pb(Ⅱ) ions can reach 97.63 mg·g-1, which is significantly higher than unmodified watermelon husk biochar (BC). The adsorption of Pb(Ⅱ) ions by modified watermelon biochar was in accordance with the Langmuir isotherm adsorption model and the pseudo second-order kinetic model, which proves that adsorption is dominated by monolayer chemical adsorption. The desorption of MBC after adsorption of Pb(Ⅱ) ions was carried out using a sodium hydroxide solution to study the reusability of MBC, and the adsorption amount was still 64.74 mg·g-1 in the sixth cycle. Characterization and analysis of adsorbents by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption, scanning electron microscopy-energy spectroscopy, zeta potential analysis, and X-ray diffraction (XRD) were carried out, which showed that the adsorption mechanism is mainly that MBC oxygen- and MBC sulfur-containing groups adsorb Pb(Ⅱ) through complexation and precipitation. Therefore, ammonium sulfide modified watermelon rind biochar can be used as a highly efficient lead adsorbent.

2.
Soft Matter ; 2020 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-32490476

RESUMO

Self-emulsification, referring to the spontaneous formation of droplets of one phase in another immiscible phase, is attracting growing interest because of its simplicity in creating droplets. Existing self-emulsification methods usually rely on phase inversion, temperature cycling, and solvent evaporation. However, achieving spatiotemporal control over the morphology of self-emulsified droplets remains challenging. In this work, a conceptually new approach of creating both simple and complex droplets by self-emulsification of a phase-separating (SEPS) aqueous film, is reported. The aqueous film is formed by depositing a surfactant-laden aqueous droplet onto an aqueous surface, and the fragmentation of the film into droplets is triggered by a wetting transition. Smaller and more uniform droplets can be achieved by introducing liquid-liquid phase separation (LLPS). Moreover, properly modulating quadruple LLPS and film fragmentation enables the creation of highly multicellular droplets such as flower-like droplets stabilized by the interfacial self-assembly of nanoparticles. This work provides a novel strategy to design aqueous droplets by LLPS, and it will inspire a wide range of applications such as membraneless organelle synthesis, cell mimics and delivery.

3.
Am J Physiol Endocrinol Metab ; 319(1): E217-E231, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32516026

RESUMO

We previously demonstrated that circulating extracellular vesicles (EVs) from patients with valvular heart disease (VHD; vEVs) contain inflammatory components and inhibit endothelium-dependent vasodilation. Neutrophil chemotaxis plays a key role in renal dysfunction, and dexmedetomidine (DEX) can reduce renal dysfunction in cardiac surgery. However, the roles of vEVs in neutrophil chemotaxis and effects of DEX on vEVs are unknown. Here, we investigated the impact of vEVs on neutrophil chemotaxis in kidneys and the influence of DEX on vEVs. Circulating EVs were isolated from healthy subjects and patients with VHD. The effects of EVs on chemokine generation, forkhead box protein O3a (FOXO3a) pathway activation and neutrophil chemotaxis on cultured human umbilical vein endothelial cells (HUVECs) and kidneys in mice and the influence of DEX on EVs were detected. vEVs increased FOXO3a expression, decreased phosphorylation of Akt and FOXO3a, promoted FOXO3a nuclear translocation, and activated the FOXO3a signaling pathway in vitro. DEX pretreatment reduced vEV-induced CXCL4 and CCL5 expression and neutrophil chemotaxis in cultured HUVECs via the FOXO3a signaling pathway. vEVs were also found to suppress Akt phosphorylation and activate FOXO3a signaling to increase plasma levels of CXCL4 and CCL5 and neutrophil accumulation in kidney. The overall mechanism was inhibited in vivo with DEX pretreatment. Our data demonstrated that vEVs induced CXCL4-CCL5 to stimulate neutrophil infiltration in kidney, which can be inhibited by DEX via the FOXO3a signaling. Our findings reveal a unique mechanism involving vEVs in inducing neutrophils chemotaxis and may provide a novel basis for using DEX in reducing renal dysfunction in valvular heart surgery.

4.
Br J Radiol ; : 20200082, 2020 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-32584595

RESUMO

OBJECTIVE: To understand the status of pre-procedural safety practices in radiological examinations at radiology residency training institutions in various Asian regions. METHODS: A questionnaire based on the Joint Commission International Accreditation Standards was electronically sent to 3 institutions each in 10 geographical regions across 9 Asian countries. Questions addressing 45 practices were divided into 3 categories. A five-tier scale with numerical scores was used to evaluate safety practices in each institution. Responses obtained from three institutions in the United States were used to validate the execution rate of each surveyed safety practice. RESULTS: The institutional response rate was 70.0% (7 Asian regions, 21 institutions). 44 practices (all those surveyed except for the application of wrist tags for identifying patients with fall risks) were validated using the US participants. Overall, the Asian participants reached a consensus on 89% of the safety practices. Comparatively, most Asian participants did not routinely perform three pre-procedural practices in the examination appropriateness topic. CONCLUSION: Based on the responses from 21 participating Asian institutions, most routinely perform standard practices during radiological examinations except when it comes to examination appropriateness. This study can provide direction for safety policymakers scrutinizing and improving regional standards of care. ADVANCES IN KNOWLEDGE: This is the first multicenter survey study to elucidate pre-procedural safety practices in radiological examinations in seven Asian regions.

5.
Chem Commun (Camb) ; 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32539061

RESUMO

The early detection of cancer shows great promise for the control and prevention of cancer. For early detection, one of the challenges that still exists is searching for methods that can illuminate tumors with high sensitivity. Here, acidity and hypoxia, two typical features that exist universally in a solid tumor microenvironment, were focused on to attain synergistic imaging with an enhanced signal-to-noise ratio. This was realized using an iridium(iii) based optical probe (Ir-1) that could sense acidity and hypoxia simultaneously and synergistically. Through the synergistic sensing of acidic pH and hypoxia, stronger emission signals or larger lifetime changes can be obtained than if a single factor (acidity or hypoxia) is used to induce variations. Furthermore, its potential for biological applications was confirmed by employing Ir-1 for phosphorescence synergistic intensity and lifetime imaging of acidity and hypoxia in live monolayer cells and 3D multicellular spheroids.

6.
Indian Heart J ; 72(2): 93-100, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32534695

RESUMO

OBJECTIVES: The different etiology of HF has different prognostic risk factors. Prognosis assessment of ICM and NICM has important clinical value. This study is aimed to explore the predicting factors for ICM and NICM. METHODS: 1082 HFrEF patients were retrospectively enrolled from Jan. 01, 2016 to Dec. 31, 2017. On Jan. 31, 2019, 873 patients were enrolled for analysis excluding incomplete, unfollowed, and unexplained data. The patients were divided into ischemic and non-ischemic group. The differences in clinical characteristics and long-term prognosis between the two groups were analyzed, and multivariate Cox analysis was used to predict the respective all-cause mortality, SCD and rehospitalization of CHF. RESULTS: 873 patients aged 64(53,73) were divided into two groups: ICM (403, 46.16%) and NICM. At the end, 203 died (111 in ICM, 54.68%), of whom 87 had SCD (53 in ICM, 60.92%) and 269 had rehospitalization for HF(134 in ICM, 49.81%). Independent risk factors affecting all-cause mortality in ICM: DM, previous hospitalization of HF, age, eGFR, LVEF; for SCD: PVB, eGFR, Hb, revascularization; for readmission of HF: low T3 syndrome, PVB, DM, previous hospitalization of HF, eGFR. Otherwise; factors affecting all-cause mortality in NICM: NYHA III-IV, paroxysmal AF/AFL, previous hospitalization of HF, ß-blocker; for SCD: low T3 syndrome, PVB, nitrates, sodium, ß-blocker; for rehospitalization of HF: paroxysmal AF/AFL, previous admission of HF, LVEF. CONCLUSIONS: Both all-cause mortality and SCD in ICM is higher than that in NICM. Different etiologies of CHF have different risk factors affecting the prognosis.

7.
J Endovasc Ther ; 27(3): 385-393, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32517556

RESUMO

Purpose: To summarize the experience and outcomes of total endovascular repair of thoracoabdominal aortic disease using 3-dimensional (3D) printed models to guide on-site creation of fenestrations in aortic stent-grafts. Materials and Methods: From April 2018 to March 2019, 34 patients (mean age 58±14 years; 24 men) with thoracoabdominal aortic disease were treated in our department. Nineteen patients had thoracoabdominal aortic dissection and 15 had thoracoabdominal aortic aneurysm. Preoperatively, a 3D printed model of the aorta was made according to computed tomography images. In the operating room, the main aortic stent-graft was completely released in the 3D printed model, and the position of each fenestration or branch was marked on the stent-graft. The fenestrations were then made using an electric pen. Wires were sewn to the edge of the fenestrations using nonabsorbable sutures. After customization, the aortic stent-graft was reloaded into the delivery sheath and deployed. Results: The printing process took ~5 hours (1 hour for image reconstruction, 3 hours for printing, and 1 hour for postprocessing). The physician-modified stent-grafts had a total of 107 fenestrations secured by 102 bridging stent-grafts, including 73 covered stents and 29 bare stents. The average procedure time was 5.6±1.2 hours, including a mean 1.3 hours for stent-graft customization. No renal insufficiency or paraplegia occurred. Two branch arteries were lost during the operation. One patient (3%) died 1 week after surgery from a retrograde dissection rupture. One patient developed a minor cerebral infarction postoperatively. The mean follow-up time was 8.5 months. There was 1 endoleak from a fenestration (coil embolized) and 4 distal ruptures of the aortic dissection (3 treated and 1 observed). Conclusion: Three-dimensional printing can be used to guide creation of fenestrated stent-grafts for the treatment of thoracoabdominal aortic diseases involving crucial branches. This technique appears to be more accurate than the traditional measurement method, with short-term follow-up demonstrating the safety and reliability of the method. However, further research and development are needed.

8.
Curr Atheroscler Rep ; 22(6): 23, 2020 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-32468443

RESUMO

PURPOSE OF REVIEW: This review summarizes the effects of microparticles and exosomes in the progression of atherosclerosis and the prospect for their diagnostic and therapeutic potentials. RECENT FINDINGS: Microparticles and exosomes can induce endothelial dysfunction, vascular inflammation, coagulation, thrombosis, and calcification via their components of proteins and noncoding RNAs, which may promote the progression of atherosclerosis. The applications of microparticles and exosomes become the spotlight of clinical diagnosis and therapy. Microparticles and exosomes are members of extracellular vesicles, which are generated in various cell types by different mechanisms of cell membrane budding and multivesicular body secretion, respectively. They are important physiologic pathways of cell-to-cell communication in vivo and act as messengers accelerating or alleviating the process of atherosclerosis. Microparticles and exosomes may become diagnostic biomarkers and therapeutic approaches of atherosclerosis.

9.
Brain Stimul ; 13(3): 655-663, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32289694

RESUMO

BACKGROUND: Transcranial direct current stimulation (tDCS) has been proven to be able to modulate motor cortical plasticity might have potential as an alternative, adjunctive therapy for Parkinson's disease (PD). However, the efficacy of tDCS in PD is still uncertain. A disease animal model may be useful to clarify the existence of a treatment effect and to explore an effective therapeutic strategy using tDCS protocols. OBJECTIVE: The current study was designed to identify the comprehensive therapeutic effects of tDCS in 6-hydroxydopamine (6-OHDA)-lesioned PD rats. METHODS: Following early and long-term tDCS application (starting 24 h after PD lesion, 300 µA anodal tDCS, 20 min/day, 5 days/week) in awake PD animals for a total of 4 weeks, the effects of tDCS on motor and non-motor behaviors as well as dopaminergic neuron degeneration levels, were identified. RESULTS: We found that the 4-week tDCS intervention significantly alleviated 6-OHDA-induced motor deficits in locomotor activity, akinesia, gait pattern and anxiety-like behavior, but not in apomorphine-induced rotations, recognition memory and depression-like behavior. Immunohistochemically, tyrosine hydroxylase (TH)-positive neurons in the substantia nigra were significantly preserved in the tDCS intervention group. CONCLUSIONS: These results suggest that early and long-term tDCS could exert neuroprotective effects and reduce the aggravation of motor dysfunctions in a 6-OHDA-induced PD rat model. Furthermore, this preclinical model may enhance the promising possibility of the potential use of tDCS and serve as a translational platform to further identify the therapeutic mechanism of tDCS for PD or other neurological disorders.

10.
PLoS One ; 15(4): e0232096, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32339210

RESUMO

Endophytic bacteria, which are common in plant tissues, may help to control plant pathogens and enhance plant growth. Camellia oleifera, an oil-producing plant, is widely grown in warm, subtropical, hilly regions in China. However, C. oleifera is strongly negatively affected by C. oleifera anthracnose, which is caused by Colletetrichum fructicola. To find a suitable biocontrol agent for C. oleifera anthracnose, 41 endophytes were isolated from the stems, leaves, and roots of C. oleifera. Bacterial cultures were identified based on analyses of 16S rDNA sequences; most strains belonged to the genus Bacillus. The antagonistic effects of these strains on C. fructicola were tested in vitro. In total, 16 strains inhibited C. fructicola growth, with B. subtilis strain 1-L-29 being the most efficient. Strain 1-L-29 demonstrated antagonistic activity against C. siamense, C. asianum, Fusarium proliferatum, Agaricodochium camellia, and Pseudomonas syringae. In addition, this strain produced indole acetic acid, solubilized phosphate, grew on N-free media, and produced siderophores. To facilitate further microecological studies of this strain, a rifampicin-resistant, green fluorescent protein (GFP)-labeled strain, 1-L-29gfpr, was created using protoplast transformation. This plasmid had good segregational stability. Strain 1-L-29gfpr was re-introduced into C. oleifera and successfully colonized root, stem, and leaf tissues. This strain remained at a stable concentration in the root more than 20 d after inoculation. Fluorescence microscopic analysis showed that strain 1-L-29gfpr thoroughly colonized the root surfaces of C. fructicola as well as the root vascular tissues of Arabidopsis thaliana.

11.
Stem Cells Dev ; 29(13): 863-875, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32323639

RESUMO

Nerve regeneration remains a challenge. Patient-derived induced pluripotent stem cell (iPSC)-differentiated neural stem cells (NSCs) provide a promising hope. Zinc is closely involved in central nervous system development and metabolism, but its role on iPSC neural differentiation is elusive and zinc detection methods in live cells are limited. In this study, intracellular zinc was detected in real time by a zinc fluorescent chemosensor and was shown to be increased during the iPSC neural induction process. iPSC neural differentiation was promoted with the addition of zinc chloride (ZnCl2) and inhibited with the addition of zinc chelator N,N,N0,N0-tetrakis(2-pyridylmethyl)-ethylenediamine, indicated by western blot and enzyme-linked immunosorbent assay analysis of NSC marker Nestin expression and measurement of neurite-like structures. Mechanistically, the phosphorylation level of ERK1/2 and STAT3 was changed with the zinc level, suggesting that zinc may affect the neural differentiation of iPSCs through ERK-STAT signaling. In conclusion, our study shows the important role of zinc in iPSC neural differentiation and suggests a new idea for iPSC-derived NSC application in nerve regeneration.

12.
Appl Radiat Isot ; 161: 109143, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32250842

RESUMO

The whole picture of the BNCT facility at Tsing Hua Open-pool Reactor will be presented which consists of the following aspects: the construction project, the beam quality, routine operations including the QA program for the beam delivery, determination of boron-10 concentration in blood, T/N ratio, and the clinical affairs including the patient recruit procedure and the patient irradiation procedure. The facility is positioned to serve for conducting clinical trials, emergent (compassionate) treatments, and R&D works.

13.
Small ; : e2001062, 2020 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-32309915

RESUMO

Color-saturated red light-emitting diodes (LEDs) with emission wavelengths at around 620-640 nm are an essential part of high-definition displays. Metal halide perovskites with very narrow emission linewidth are promising emitters, and rapid progress has been made in perovskite-based LEDs (PeLEDs); however, the efficiency of the current color-pure red PeLEDs-still far lags behind those of other-colored ones. Here, a simple but efficient strategy is reported to gradually down-shift the Fermi level of perovskite nanocrystals (NCs) by controlling the interaction between NCs and their surface molecular electron acceptor-benzyl iodide with aromatic rings-and realize p-doping in the color-saturated 625 nm emitting NCs, which significantly reduces the hole injection barrier in devices. Besides, both the luminescence efficiency and electric conductivity of perovskite NCs are enhanced as additional advantages as the result of surface defects passivation. As a result, the external quantum efficiency for the resulting LED is increased from 4.5% to 12.9% after benzyl iodide treatment, making this device the best-performing color-saturated red PeLED so far. It is further found that the hole injection plays a more critical role than the photoluminescence efficiency of perovskite emitter in determining the LED performance, which implies design principles for efficient thin-film planar LEDs.

14.
Small ; : e2000749, 2020 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-32285619

RESUMO

Supported metal nanoparticles (MNPs) undergo severe aggregation, especially when the interaction between MNPs and their supports are limited and weak where their performance deteriorates dramatically. This becomes more severe when catalysts are operated under high temperature. Here, it is reported that MNPs including Pt, Au, Rh, and Ru, with sub-2 nm size can be stabilized on densely packed defective CeO2 nanoparticles with sub-5 nm size via strong coupling by direct laser conversion of corresponding metal ions encapsulated cerous metal-organic frameworks (Ce-MOFs). Ce-MOF serves as an ideal dispersion precursor to uniformly encapsulate noble metal ions in their orderly arranged pores. Ultrafast laser vaporization and cooling forms uniform, ultrasmall, well-mixed, and exceptionally dense nanoparticles of metal and metal oxide concurrently. The laser-induced ultrafast reaction (within tens of nanoseconds) facilitates the precipitation of CeO2 nanoparticles with abundant surficial defects. Due to the well-mixed ultrasmall Pt and CeO2 components with strong coupling, this catalyst exhibits exceptionally high stability and activity both at low and high temperatures (170-1100 °C) for CO oxidation in long-term operation, significantly exceeding catalysts prepared by traditional methods. The scalable feature of laser and huge MOF family make it a versatile method for the production of MNP-based nanocomposites in wide applications.

15.
Clin Otolaryngol ; 2020 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-32348006

RESUMO

OBJECTIVES: The aim of this anatomical study is to make quantitative comparison among three endoscopic approaches, encompassing contralateral endonasal transseptal transmaxillary transpterygoid approach (contralateral EEA), endoscopic sublabial transmaxillary transalisphenoid (Caldwell-Luc) approach, and endoscopic transorbital transmaxillary approach through inferior orbital fissure (ETOA), to the anterolateral skull base for assisting preoperative planning. DESIGN & PARTICIPANTS: Anatomical dissections were performed in four adult cadaveric heads bilaterally using three endoscopic transmaxillary approaches described above. SETTING: Skull Base Laboratory at the National Defense Medical Center. MAIN OUTCOME MEASURES: The area of exposure, angles of attack, and depth of surgical corridor of each approach were measured and obtained for statistical comparison. RESULTS: The ETOA had significantly larger exposure over middle cranial fossa (731.40 ± 80.08 mm2 ) than contralateral EEA (266.60 ± 46.74 mm2 ) and Caldwell-Luc approach (468.40 ± 59.67 mm2 ). In comparison with contralateral EEA and Caldwell-Luc approach, the ETOA offered significantly greater angles of attack and shorter depth of surgical corridor (P < 0.05 for all comparisons). CONCLUSIONS: The ETOA is the superior choice for target lesion occupying multiple compartments with its epicenter located in the middle cranial fossa or superior portion of infratemporal fossa.

16.
Zootaxa ; 4751(3): zootaxa.4751.3.5, 2020 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-32230407

RESUMO

This paper provides the first description of a female of Shoveliteratura triangula Shi, Bian Change, 2011, as well as the complete mitogenome sequence using next-generation sequencing (NGS) technology. The length of the entire mitogenome was 16,152 bp and contained the typical gene arrangement, base composition, and codon usage found in other related species. The overall base composition exhibited a clear anti-G (10.8%) and AT bias (70.5%). The third codon positions in all protein-coding genes (PCGs) displayed high AT-content values (81.4%) in contrast to lower values of 64.2%/64.5% in the first/second positions. Two tandem repeats, 2.49 repeats of 112 bp and 3.65 repeats of 201 bp, contributed 1013 bp to the length of the S. triangula control region (CR). A T-stretch as a recognition sequence of the replication origin and more than one distinct tandem repeat in the CR were common in the Tettigoniidae mitogenomes. Both the maximum likelihood (ML) and Bayesian inference (BI) analyses supported each subfamily of the Tettigoniidae as a monophyletic group. The relationships of the subfamilies were as follows: (Lipotactinae (Hexacentrinae (Conocephalinae (Meconematinae (Bradyporinae, Tettigoniinae))))). The newly sequenced species S. triangula was most closely related to Pseudokuzicus pieli.


Assuntos
Genoma Mitocondrial , Ortópteros , Animais , Teorema de Bayes , Feminino , Genômica , Filogenia , RNA de Transferência
17.
Zhongguo Zhen Jiu ; 40(3): 247-50, 2020 Mar 12.
Artigo em Chinês | MEDLINE | ID: mdl-32270635

RESUMO

OBJECTIVE: To compare the clinical effect between Stiletto needle combined with massotherapy and articular injection of sodium hyaluronate for pain in patients with knee osteoarthritis (KOA). METHODS: A total of 156 patients with KOA were randomly divided into an observation group and a control group, 78 cases in each group. The patients in the observation group were treated with Stiletto needle (once a week) combined with massotherapy (twice a week); the patients in the control group were treated with articular injection of sodium hyaluronate (once a week). The treatment period were 5 weeks in total. The visual analogue scale (VAS) score, local tenderness value, knee joint activity and Lysholm knee joint score were recorded before treatment, 3 weeks and 5 weeks of treatment. RESULTS: Compared before treatment, the VAS score, local tenderness value, knee joint activity and Lysholm knee joint score in the two groups were improved 5 weeks of treatment (P<0.05). After 5 weeks of treatment, The local tenderness value and Lysholm knee joint score in the observation group were significantly improved compared with the control group (P<0.05), but the knee joint activity in the control group was superior to that in the observation group (P<0.05). CONCLUSION: The Stiletto needle combined with massotherapy are superior to articular injection of sodium hyaluronate in relieving pain and improving knee joint function in patients with early-to-moderate KOA, but its effect on joint activity is inferior to sodium hyaluronate.

18.
J Phys Chem Lett ; : 3481-3487, 2020 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-32298119

RESUMO

Single-atom catalysis has recently emerged as a promising approach for catalyzing the carbon dioxide reduction reaction (CO2RR). In this study, we present a principle for designing active single-atom catalysts (SACs) for CO2RR. We systematically examine totally 24 transition metals supported by a graphitic carbon nitride (g-CN) monolayer and find that their catalytic activities are highly correlated with the adsorption free energies of two intermediate species (OH and OCH). We then identify two important intrinsic descriptors, namely, the number of electrons in the outmost d-shell and the enthalpy of vaporization of the transition metal. Test calculations on transition metals supported by a C2N monolayer indicate that both descriptors are quite universal for SACs of CO2RR. Based on these results, we show that Ni@g-CN, Cu@g-CN, and Co@C2N are promising SACs for CO2RR. This study offers an effective principle for designing highly active SACs for CO2RR on the basis of intrinsic properties of transition metals.

19.
J Phys Chem Lett ; 11(7): 2541-2549, 2020 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-32163707

RESUMO

Recently, the reduction of CO2 to fuels has been the subject of numerous studies, but the selectivity and activity remain inadequate. Progress has been made on single-site two-dimensional catalysts based on graphene coupled to a metal and nitrogen for the CO2 reduction reaction (CO2RR); however, the product is usually CO, and the metal-N environment remains ambiguous. We report a novel two-dimensional graphene nitrene heterostructure (grafiN6) providing well-defined active sites (N6) that can bind one to three metals for the CO2RR. We find that homobimetallic FeFe-grafiN6 could reduce CO2 to CH4 at -0.61 V and to CH3CH2OH at -0.68 V versus reversible hydrogen electrode, with high product selectivity. Moreover, the heteronuclear FeCu-grafiN6 system may be significantly less affected by hydrogen evolution reaction, while maintaining a low limiting potential (-0.68 V) for C1 and C2 mechanisms. Binding metals to one N6 site but not the other could promote efficient electron transport facilitating some reaction steps. This framework for single or multiple metal sites might also provide unique catalytic sites for other catalytic processes.

20.
Langmuir ; 36(12): 3057-3063, 2020 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-32160744

RESUMO

Microalgae biofilm-based culture systems have wide applications in environmental engineering and biotechnology. Biofilm structure is critical for the transport of nutrients, gas, and signaling molecules in a microalgal biofilm. This work aims to understand the influence of cell surface energy (SE) on the microalgal biofilm structure. Three microalgae species were used as model cells in the study: Chlorella sp., Nannochloris oculata, and Chlorella pyrenoidosa. First, by mediating biofilm culture conditions, we obtained Chlorella sp. cells with SEs of 40.4 ± 1.5, 44.7 ± 1.0, and 62. 7 ± 1.2 mJ/m2, N. oculata cells with SEs of 47.7 ± 0.5, 41.1 ± 1.0, and 62.6 ± 1.2 mJ/m2, and C. pyrenoidosa cells with SEs of 64.0 ± 0.6, 62.1 ± 0.7, and 62.8 ± 0.6 mJ/m2. Then, based on the characterizations of biofilm structures, we found that cell SE can significantly affect the microalgae biofilm structure. When the cell SEs ranged from 40 to 50 mJ/m2, the microalgae cells formed heterogeneous biofilms with a large number of open voids, and the biofilm porosity was higher than 20%. Alternatively, when the cell SEs ranged from 50 to 65 mJ/m2, the cells formed a flat, homogeneous biofilm with the porosity lower than 20%. Finally, the influencing mechanism of cell SE on biofilm structure was interpreted based on the thermodynamic theory via analyzing the co-adhesion energy between cells. The study has important implications in understanding factors that influence the biofilm structures.

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