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1.
Adv Healthc Mater ; 9(2): e1901528, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31820854

RESUMO

Bimetallic nanoparticles have received considerable attention owing to synergistic effect and their multifunctionality. Herein, new multifunctional Pd@Au bimetallic nanoplates decorated hollow mesoporous MnO2 nanoplates (H-MnO2 ) are demonstrated for achieving not only nucleus-targeted NIR-II photothermal therapy (PTT), but also tumor microenvironment (TME) hypoxia relief enhanced photodynamic therapy (PDT). The Pd@Au nanoplates present a photothermal conversion efficiency (PTCE) as high as 56.9%, superior to those PTAs activated in the NIR-II region such as Cu9 S5 nanoparticles (37%), Cu3 BiS3 nanorods (40.7%), and Au/Cu2- x S nanocrystals (43.2%). They further functionalize with transactivator of transcription (TAT) moiety for cell nuclear-targeting and biodegradable hollow mesoporous MnO2 (≈100 nm) loaded with photosensitizer Ce6 (TAT-Pd@Au/Ce6/PAH/H-MnO2 ) to construct a hierarchical targeting nanoplatform. The as-made TAT-Pd@Au/Ce6/PAH/H-MnO2 demonstrates good premature renal clearance escape ability and increased tumor tissue accumulation. It can be degraded in acidic TME and generate O2 by reacting to endogenous H2 O2 to relieve the hypoxia for enhanced PDT, while the released small TAT-Pd@Au nanoplates can effectively enter into the nucleus to mediate PTT. As a result, a remarkable therapeutic effect is achieved owing to the synergistic PTT/PDT therapy. This hierarchical targeting, TME-responsive, cytoplasm hypoxia relief PDT, and nuclear NIR-II PTT synergistic therapy can pave a new avenue for nanomaterials-based cancer therapy.

2.
Adv Mater ; 32(7): e1904249, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31880031

RESUMO

The development of highly efficient photocatalytic systems with rapid photogenerated charge separation and high surface catalytic activity is highly desirable for the storage and conversion of solar energy, yet remains a grand challenge. Herein, a conceptionally new form of atomically dispersed Co-P3 species on CdS nanorods (CoPSA-CdS) is designed and synthesized for achieving unprecedented photocatalytic activity for the dehydrogenation of formic acid (FA) to hydrogen. X-ray absorption near edge structure, X-ray photoelectron spectroscopy, and time-resolved photoluminescence results confirm that the Co-P3 species have a unique electron-rich feature, greatly improving the efficiency of photogenerated charge separation through an interface charge effect. The in situ attenuated total reflection infrared spectra reveal that the Co-P3 species can achieve much better dissociation adsorption of FA and activation of CH bonds than traditional sulfur-coordinated Co single atom-loaded CdS nanorods (CoSSA-CdS). These two new features make CoPSA-CdS exhibit the unprecedented 50-fold higher activity in the photocatalytic dehydrogenation of FA than CoSSA-CdS, and also much better activity than the Ru-, Rh-, Pd-, or Pt-loaded CdS. Besides, CoPSA-CdS also shows the highest mass activity (34309 mmol gCo -1 h-1 ) of Co reported to date. First-principles simulation reveals that the Co-P3 species herein can form an active PHCOO intermediate for enhancing the rate-determining dissociation adsorption of FA.

3.
Nat Commun ; 10(1): 5231, 2019 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-31745074

RESUMO

The grand challenge in the development of atomically dispersed metallic catalysts is their low metal-atom loading density, uncontrollable localization and ambiguous interactions with supports, posing difficulty in maximizing their catalytic performance. Here, we achieve an interface catalyst consisting of atomic cobalt array covalently bound to distorted 1T MoS2 nanosheets (SA Co-D 1T MoS2). The phase of MoS2 transforming from 2H to D-1T, induced by strain from lattice mismatch and formation of Co-S covalent bond between Co and MoS2 during the assembly, is found to be essential to form the highly active single-atom array catalyst. SA Co-D 1T MoS2 achieves Pt-like activity toward HER and high long-term stability. Active-site blocking experiment together with density functional theory (DFT) calculations reveal that the superior catalytic behaviour is associated with an ensemble effect via the synergy of Co adatom and S of the D-1T MoS2 support by tuning hydrogen binding mode at the interface.

4.
Nature ; 574(7776): 81-85, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31554968

RESUMO

The efficient interconversion of chemicals and electricity through electrocatalytic processes is central to many renewable-energy initiatives. The sluggish kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER)1-4 has long posed one of the biggest challenges in this field, and electrocatalysts based on expensive platinum-group metals are often required to improve the activity and durability of these reactions. The use of alloying5-7, surface strain8-11 and optimized coordination environments12 has resulted in platinum-based nanocrystals that enable very high ORR activities in acidic media; however, improving the activity of this reaction in alkaline environments remains challenging because of the difficulty in achieving optimized oxygen binding strength on platinum-group metals in the presence of hydroxide. Here we show that PdMo bimetallene-a palladium-molybdenum alloy in the form of a highly curved and sub-nanometre-thick metal nanosheet-is an efficient and stable electrocatalyst for the ORR and the OER in alkaline electrolytes, and shows promising performance as a cathode in Zn-air and Li-air batteries. The thin-sheet structure of PdMo bimetallene enables a large electrochemically active surface area (138.7 square metres per gram of palladium) as well as high atomic utilization, resulting in a mass activity towards the ORR of 16.37 amperes per milligram of palladium at 0.9 volts versus the reversible hydrogen electrode in alkaline electrolytes. This mass activity is 78 times and 327 times higher than those of commercial Pt/C and Pd/C catalysts, respectively, and shows little decay after 30,000 potential cycles. Density functional theory calculations reveal that the alloying effect, the strain effect due to the curved geometry, and the quantum size effect due to the thinness of the sheets tune the electronic structure of the system for optimized oxygen binding. Given the properties and the structure-activity relationships of PdMo metallene, we suggest that other metallene materials could show great promise in energy electrocatalysis.

5.
Angew Chem Int Ed Engl ; 58(40): 14184-14188, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31365167

RESUMO

Noble metal single atoms coordinated with highly electronegative atoms, especially N and O, often suffer from an electron-deficient state or poor stability, greatly limiting their wide application in the field of catalysis. Herein we demonstrate a new PH3 -promoted strategy for the effective transformation of noble metal nanoparticles (MNPs, M=Ru, Rh, Pd) at a low temperature (400 °C) into a class of thermally stabilized phosphorus-coordinated metal single atoms (MPSAs) on g-C3 N4 nanosheets via the strong Lewis acid-base interaction between PH3 and the noble metal. Experimental work along with theoretical simulations confirm that the obtained Pd single atoms supported on g-C3 N4 nanosheets exist in the form of PdP2 with a novel electron-rich feature, conceptionally different from the well-known single atoms with an electron-deficient state. As a result of this new electronic property, PdP2 -loaded g-C3 N4 nanosheets exhibit 4 times higher photocatalytic H2 production activity than the state-of-art N-coordinated PdSAs supported on g-C3 N4 nanosheets. This enhanced photocatalytic activity of phosphorus-coordinated metal single atoms with an electron-rich state was quite general, and also observed for other active noble metal single atom catalysts, such as Ru and Rh.

6.
J Laparoendosc Adv Surg Tech A ; 29(10): 1320-1324, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31347974

RESUMO

Background: Esophageal hiatal hernia can be classified into four types. It has been reported that most complications occurred in type II-IV hernia patients compared with type I hernia. This study aimed to investigate and compare the efficacy, complications, and long-time outcomes after laparoscopic fundoplication between type I and type II-IV hernia patients. Materials and Methods: Medical records of 110 children who underwent laparoscopic fundoplication during 2008-2017 in our institution were retrospectively analyzed. Information of postoperative symptoms, complications, and quality of life (QOL) were compared between different types. Results: All 110 children underwent laparoscopic fundoplication, and none converted to open surgery. Type I and type II-IV each accounted for 50.9% and 42.8%. There was no significant difference in the perioperative data between type I and type II-IV esophageal hiatal hernia. The follow-up information of 81 children was obtained. The scores of postoperative symptoms were comparable between type I and type II-IV group, except the severity score of reflux symptom was higher in type I hernia patients (P = .032). The difference in the incidence of postoperative complications and recurrence after laparoscopic fundoplication between type I and type II-IV hernia was not significant. The QOL in three aspects improved significantly after laparoscopic fundoplication in all types of esophageal hiatal hernia. Conclusions: Laparoscopic fundoplication was an effective approach for all types of esophageal hiatal hernia. Type II-IV hernia could obtain a comparable therapeutic effect and long-time outcome compared with type I hernia despite its increased complexity of the anatomy and the required laparoscopic repair procedure.


Assuntos
Fundoplicatura/métodos , Hérnia Hiatal/cirurgia , Laparoscopia/métodos , Pré-Escolar , Feminino , Refluxo Gastroesofágico/cirurgia , Humanos , Lactente , Tempo de Internação , Masculino , Complicações Pós-Operatórias/epidemiologia , Qualidade de Vida , Estudos Retrospectivos , Fatores de Tempo
7.
Chem Sci ; 10(23): 5898-5905, 2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-31360394

RESUMO

Sub-nanometer noble metal catalysts, especially single atom (SA), are a new class of catalytic materials for boosting catalysis and possess unique catalytic properties and high atomic utilization efficiency. Exploring the interaction between two neighboring atom monomers has great potential to further improve the performance of SA catalysts and deepen the understanding on the catalytic mechanism of heterogeneous catalysis at the atomic level. Herein, we demonstrate that the synergetic effect between neighboring Pt and Ru monomers supported on N vacancy-rich g-C3N4 promotes the catalytic CO oxidation. The experimental observation and theoretical simulation reveal that the N vacancy in the g-C3N4 structure builds an optimized triangular sub-nanometer cavity for stabilizing the neighboring Pt-Ru monomers by forming Pt-C and Ru-N bonds. The mechanistic studies based on the in situ IR spectrum and theoretical simulation confirm that the neighboring Pt-Ru monomers possess a higher performance for optimizing O2 activation than Ru-Ru/Pt-Pt monomers or isolated Ru/Pt atoms by balancing the energy evolution of reaction steps in the catalytic CO oxidation. The discovery of the synergetic effect between neighboring monomers may create a new path for manipulating the catalytic properties of SA catalysts.

8.
BMC Public Health ; 19(1): 722, 2019 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-31182070

RESUMO

BACKGROUND: The HIV prevalence among men who have sex with men (MSM) in China has increased yearly. This study aimed to explore the association between the characteristics of social communication and condomless anal intercourse (CAI) among MSM and the implications for prevention and control of HIV among MSM in China using an egocentric network framework. METHODS: The data were collected in Guangzhou between November 2016 and May 2017 through standardized face-to-face interviews. The participants were recruited among MSM who received voluntary counselling and testing services (VCT) provided by nongovernmental organizations (NGOs) and the local Centers for Disease Control and Prevention (CDC). We used the framework of the egocentric network analysis, the odd ratios of CAI were analyzed using generalized estimating equations (GEE). RESULTS: In total, 1073 MSM who nominated 2667 sexual partners were sampled. MSM who were approximately 30 years old and chose sexual partners of different age category were more likely to engage in CAI. Participants with high level education who were in partnerships with individuals with lower education levels had a higher risk of CAI. Participants who reported having a strong relationship with their sexual partners(AOR = 1.31) were associated with a higher probability of experiencing CAI during sex; while having sexual partners who were unmarried (OR = 0.56), and participants who reported meeting sexual partners online (AOR = 0.74) or, having sex with an occasional partner (AOR = 0.44)were less likely to engage in CAI. CONCLUSION: Our study indicates that the strength of sexual dyadic relational ties and different social communication mixing patterns across ages, educational categories, and marital status were associated with CAI.


Assuntos
Preservativos/estatística & dados numéricos , Homossexualidade Masculina/estatística & dados numéricos , Comportamento Sexual/estatística & dados numéricos , Minorias Sexuais e de Gênero/estatística & dados numéricos , Sexo sem Proteção/estatística & dados numéricos , Adulto , China/epidemiologia , Infecções por HIV/epidemiologia , Infecções por HIV/prevenção & controle , Homossexualidade Masculina/psicologia , Humanos , Masculino , Estado Civil , Pessoa de Meia-Idade , Razão de Chances , Prevalência , Comportamento Sexual/psicologia , Parceiros Sexuais , Minorias Sexuais e de Gênero/psicologia , Sexo sem Proteção/psicologia
9.
J Assoc Nurses AIDS Care ; 30(4): 428-439, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31241507

RESUMO

Intimate partners of people living with HIV are at risk of HIV infection. We assessed the acceptability of female condom use among 89 married, heterosexual, HIV-serodiscordant couples from Sichuan and Hunan provinces in China for this prospective observational cohort study. Participants used female condoms for 3 months, reporting use and attitudes in written logs and questionnaires. At the end of the study, 58.4% of couples expressed willingness to continue using female condoms. Factors associated with willingness to use female condoms were (a) the female partner reporting having experienced forced sex by the male partner, (b) applying a lubricant to the penis, (c) understanding the correct application method, (d) being married more than 20 years, and (e) experiencing no difficulty during the first use. Most HIV-serodiscordant couples found female condoms to be acceptable. Increasing access to female condoms could be an acceptable alternative barrier method to male condoms for preventing HIV transmission.

10.
Org Biomol Chem ; 17(20): 5121-5128, 2019 05 28.
Artigo em Inglês | MEDLINE | ID: mdl-31073552

RESUMO

A metal-free C-H formylation and acylation of BODIPY dyes using a variety of dioxolane derivatives as aldehyde equivalents is reported, providing a postfunctionalization method for controllable synthesis of BODIPYs with carbonyl groups at 3,5-positions via a radical process. The photophysical properties of resultant dyes from this efficient one-pot, chemo- and site-selective transformation have been studied.

11.
Chem Commun (Camb) ; 55(32): 4691-4694, 2019 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-30938736

RESUMO

An efficient Cu(ii)-catalyzed, C-H alkylation of BODIPY with a variety of alkyl diacyl peroxides has been developed for the first time, providing a late-stage and straightforward method for controllable synthesis of monoalkylated and dialkylated BODIPYs via a radical process that otherwise is difficult to obtain by literature methods. This chemo- and site-selective transformation will allow for the introduction of a variety of functionalities on the BODIPY core for highly versatile tethering to receptors and to other molecules of interest.


Assuntos
Compostos de Boro/química , Cobre/química , Corantes Fluorescentes/química , Peróxidos/química , Alquilação , Compostos de Boro/síntese química , Catálise , Corantes Fluorescentes/síntese química , Estrutura Molecular
12.
Adv Mater ; 31(15): e1805833, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30803065

RESUMO

The development of new electrocatalysts with high activity and durability for alcohol oxidation is an emerging need of direct alcohol fuel cells. However, the commonly used Pt-based catalysts still exhibit drawbacks including limited catalytic activity, high overpotential, and severe CO poisoning. Here a general approach is reported for preparing ultrathin PtNiM (M = Rh, Os, and Ir) nanowires (NWs) with excellent anti-CO-poisoning ability and high activity. Owing to their superior nanostructure and optimal electronic interaction, the ultrathin PtNiM NWs show enhanced electrocatalytic performance for both methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). The optimal PtNiRh NWs show mass activity of 1.72 A mg-1 and specific activity of 2.49 mA cm-2 for MOR, which are 3.17 and 2.79 times higher than those of Pt/C. In particular, the onset potentials of PtNiRh NWs for MOR and EOR shift down by about 65 and 85 mV compared with those of Pt/C. Density functional theory calculations further verify their high antipoison properties for MOR and EOR from both an electronic and energetic perspective. Facilitated by the introduction of Rh and Ni, the stable pinning of the Pt 5d band associated with electron-rich and depletion centers solves the dilemma between reactivity and anti-CO poisoning.

13.
Chem Commun (Camb) ; 55(11): 1639-1642, 2019 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-30657483

RESUMO

An efficient transition-metal-free regioselective C-H/S-H cross-coupling of BODIPY with thiols has been developed for the first time, providing a new and more straightforward method for controllable synthesis of mono-, di- and trithiolation BODIPYs via a radical process, which are otherwise difficult to obtain by literature methods. This new method will stimulate the synthesis of new and sophisticated thioether-decorated BODIPY dyes and will also easily allow the introduction of a variety of functionalities onto the BODIPY core through the thioether (pseudohalogen) functionalized BODIPY fluorophores.

14.
Small ; 15(1): e1804212, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30515971

RESUMO

The development of cost-efficient, active, and stable electrode materials as bifunctional catalysts for electrochemical water splitting is crucial to high-performance renewable energy storage and conversion devices. In this work, the synthesis of Co-based multi-metal borides nanochains with amorphous structure is reported for boosting the oxygen evolution (OER) and hydrogen evolution reactions (HER) by one-pot NaBH4 reduction of Co2+ , Ni2+ , and Fe2+ under ambient temperature. In all the investigated Co-based metal borides, NiCoFeB nanochains show the excellent OER performance with a low overpotential of 284 mV at 10 mA cm-2 and Tafel slope of 46 mV dec-1 , respectively, together with excellent catalytic stability, and robust HER performance with an overpotential of 345 mV at 10 mA cm-2 . The density functional theory (DFT) calculations reveal that the excellent electrocatalytic performance is mainly attributed to optimal electronic structure by tuning the Co-3d band activities by the incorporation of Ni and Fe for enhanced water splitting via the potentially existed Co0 state. Moreover, the electrolyzer using NiCoFeB nanochains as anode and cathode offers 10 mA cm-2 at a cell voltage of 1.81 V, comparable to commercial Pt/C // Ir/C, providing a simple method to design and explore highly efficient and cheap bifunctional electrocatalysts for overall water splitting.

15.
J Am Chem Soc ; 140(50): 17624-17631, 2018 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-30403846

RESUMO

Neutral aqueous zinc-air batteries (ZABs) are an emerging type of energy devices with substantially elongated lifetime and improved recyclability compared to conventional alkaline ZABs. However, their development is impeded by the lack of robust bifunctional catalyst at the air-electrode for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). Here, we report the controlled synthesis of NiFe2O4/FeNi2S4 heterostructured nanosheets (HNSs) that are highly efficient in catalyzing OER and ORR, therefore enabling neutral rechargeable ZABs. Associated with the formation of abundant oxide/sulfide interfaces over NiFe2O4/FeNi2S4 HNSs' surfaces, the catalyst's oxygen binding energy can be effectively tuned to enhance the OER and ORR activities, as revealed by the density functional theory calculations. In 0.2 M phosphate buffer solution, the optimized NiFe2O4/FeNi2S4 HNSs present an excellent oxygen electrocatalytic activity and stability, with much lower OER and ORR overpotentials than single-component FeNi2S4 or NiFe2O4 and with negligible performance decay in accelerated durability testing. When used as an air-electrode, the NiFe2O4/FeNi2S4 HNSs can deliver a power density of 44.4 mW cm-2 and a superior cycling stability (only 0.6% decay after 900 cycles at 0.5 mA cm-2), making the resultant ZAB the most efficient and robust one with a neutral aqueous electrolyte reported to date. This work highlights the essential function of the heterostructure interface in oxygen electrocatalysis, opening a new avenue to advanced neutral metal-air batteries.

16.
J Exp Clin Cancer Res ; 37(1): 258, 2018 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-30359286

RESUMO

BACKGROUND: Neuroblastoma (NB) is the most common pediatric solid tumor that originates from neural crest-derived sympathoadrenal precursor cells that are committed to development of sympathetic nervous system. The well differentiated histological phenotype of NB tumor cells has been reportedly associated with favorable patient outcome. Retinoic acid (RA) can effectively induce NB cell differentiation, thereby being used in the clinic as a treatment agent for inducing the differentiation of high-risk NB. However, the underlying molecular mechanisms of regulating differentiation remain elusive. METHODS: The correlation between clinical characteristics, survival and the deubiquitinating enzyme ubiquitin C-terminal hydrolase 1 (UCHL1) expression were assessed using a neuroblastic tumor tissue microarray, and then validated in three independent patient datasets. The different expression of UCHL1 in ganglioneuroblastoma, ganglioneuroma and NB was detected by immunohistochemistry, mass spectra and immunoblotting analysis, and the correlation between UCHL1 expression and the differentiated histology was analyzed, which was also validated in three independent patient datasets. Furthermore, the roles of UCHL1 in NB cell differentiation and proliferation and the underlying mechanisms were studied by using short hairpin RNA and its inhibitor LDN57444 in vitro. RESULTS: Based on our neuroblastic tumor tissue microarrays and three independent validation datasets (Oberthuer, Versteeg and Seeger), we identified that UCHL1 served as a prognostic marker for better clinical outcome in NB. We further demonstrated that high UCHL1 expression was associated with NB differentiation, indicated by higher UCHL1 expression in ganglioneuroblastomas/ganglioneuromas and well-differentiated NB than poorly differentiated NB, and the positive correlation between UCHL1 and differentiation markers. As expected, inhibiting UCHL1 by knockdown or LDN57444 could significantly inhibit RA-induced neural differentiation of NB tumor cells, characterized by decreased neurite outgrowth and neural differentiation markers. This effect of UCHL1 was associated with positively regulating RA-induced AKT and ERK1/2 signaling activation. What's more, knockdown of UCHL1 conferred resistance to RA-induced growth arrest. CONCLUSION: Our findings identify a pivotal role of UCHL1 in NB cell differentiation and as a prognostic marker for survival in patients with NB, potentially providing a novel therapeutic target for NB.


Assuntos
Biomarcadores Tumorais/metabolismo , Neuroblastoma/metabolismo , Neurônios/citologia , Ubiquitina Tiolesterase/metabolismo , Diferenciação Celular , Linhagem Celular Tumoral , Proliferação de Células , Criança , Ganglioneuroblastoma/metabolismo , Ganglioneuroma/metabolismo , Regulação Neoplásica da Expressão Gênica , Humanos , Neurônios/metabolismo , Prognóstico , Análise de Sobrevida , Análise Serial de Tecidos , Regulação para Cima
17.
ACS Cent Sci ; 4(9): 1244-1252, 2018 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-30276259

RESUMO

The development of highly efficient and durable electrocatalysts for high-performance overall water-splitting devices is crucial for clean energy conversion. However, the existing electrocatalysts still suffer from low catalytic efficiency, and need a large overpotential to drive the overall water-splitting reactions. Herein, we report an iridium-tungsten alloy with nanodendritic structure (IrW ND) as a new class of high-performance and pH-universal bifunctional electrocatalysts for hydrogen and oxygen evolution catalysis. The IrW ND catalyst presents a hydrogen generation rate ∼2 times higher than that of the commercial Pt/C catalyst in both acid and alkaline media, which is among the most active hydrogen evolution reaction (HER) catalysts yet reported. The density functional theory (DFT) calculations reveal that the high HER intrinsic catalytic activity results from the suitable hydrogen and hydroxyl binding energies, which can accelerate the rate-determining step of the HER in acid and alkaline media. Moreover, the IrW NDs show superb oxygen evolution reaction (OER) activity and much improved stability over Ir. The theoretical calculation demonstrates that alloying Ir metal with W can stabilize the formed active iridium oxide during the OER process and lower the binding energy of reaction intermediates, thus improving the Ir corrosion resistance and OER kinetics. Furthermore, the overall water-splitting devices driven by IrW NDs can work in a wide pH range and achieve a current density of 10 mA cm-2 in acid electrolyte at a low potential of 1.48 V.

18.
ACS Appl Mater Interfaces ; 10(44): 37974-37980, 2018 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-30207451

RESUMO

With its inherent zig-zag layered structure and open framework, Na2Ti3O7 (NTO) is a promising anode material for potassium-ion batteries (KIBs). However, its poor electronic conductivity caused by large band gap (∼3.7 eV) usually leads to low-performance KIBs. In this work, we synthesize the fluff-like hydrogenated Na2Ti3O7 (HNTO) nanowires grown on N-doped carbon sponge (CS) as a binder-free and current-collector-free flexible anode for KIBs (denoted as HNTO/CS). High-resolution X-ray photoelectron spectroscopy (XPS) and electron spin-resonance spectroscopy (ESR) confirm the existence of Ti-OHs and O vacancies in HNTO. The first-principles calculation discloses that both Ti-OHs and O vacancies are equivalent to n-type doping because they can shift the Fermi level up to the conduction band, thus leading to a higher electronic conductivity and better performance for KIBs. In addition, the N-doped CS can further reinforce the conductivity and avoid the aggregation of HNTO nanowires during cycling. As a result, the as-made HNTO/CS can deliver a capacity of 107.8 mAh g-1 at 100 mA g-1 after 20 cycles, and keep the capacity of 90.9% and 82.5% after 200 and 1555 cycles, respectively, much better than the samples without hydrogenation treatment or N-doped CS and reported KTi xO y-based materials. Our work highlights the importance of hydrogenation treatment and N-doped CS in enhancing the electrochemical property for KIBs.

19.
Adv Mater ; 30(43): e1803220, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30260517

RESUMO

Iron-nitrogen-carbon (Fe-N-C) is hitherto considered as one of the most satisfactory alternatives to platinum for the oxygen reduction reaction (ORR). Major efforts currently are devoted to the identification and maximization of carbon-enclosed FeN4 moieties, which act as catalytically active centers. However, fine-tuning of their intrinsic ORR activity remains a huge challenge. Herein, a twofold activity improvement of pristine Fe-N-C through introducing Ti3 C2 Tx MXene as a support is realized. A series of spectroscopy and magnetic measurements reveal that the marriage of FeN4 moiety and MXene can induce remarkable Fe 3d electron delocalization and spin-state transition of Fe(II) ions. The lower local electron density and higher spin state of the Fe(II) centers greatly favor the Fe d z 2 electron transfer, and lead to an easier oxygen adsorption and reduction on active FeN4 sites, and thus an enhanced ORR activity. The optimized catalyst shows a two- and fivefold higher specific ORR activity than those of pristine catalyst and Pt/C, respectively, even exceeding most Fe-N-C catalysts ever reported. This work opens up a new pathway in the rational design of Fe-N-C catalysts, and reflects the critical influence of Fe 3d electron states in FeN4 moiety supported on MXene in ORR catalysis.

20.
BMJ Open ; 8(7): e022394, 2018 07 30.
Artigo em Inglês | MEDLINE | ID: mdl-30061446

RESUMO

OBJECTIVE: To determine the feasibility of long-term prospective follow-up and ascertainment of cancer in offspring and mothers from the 1993-1995 Chinese Community Intervention Program that provided folic acid supplements before and during early pregnancy to reduce neural tube defects. DESIGN: Feasibility pilot study for a prospective cohort study. SETTING: Families residing during 2012-2013 in one rural and one urban county from 21 counties in 3 provinces in China included in the Community Intervention Program campaign. PARTICIPANTS: The feasibility study targeted 560 families, including 280 from the rural and 280 from the urban county included in the large original study; about half of mothers in each group had taken and half had not taken folic acid supplements. INTERVENTION: The planned new study is observational. PRIMARY AND SECONDARY OUTCOME MEASURES: Primary: incidence of paediatric cancers in offspring; secondary: other chronic diseases in offspring and chronic diseases in mothers RESULTS: Only 3.4% of pilot study families could not be found, 3.9% had moved out of the study area and 8.8% refused to participate. Interviews were completed by 82% of mothers, 79% of fathers and 83% of offspring in the 560 families. Almost all mothers and offspring who were interviewed also participated in anthropometric measurements. We found notable urban-rural differences in sociodemographic and lifestyle characteristics of the parents, but fewer differences among the offspring. In eight catchment area hospitals, we identified a broad range of paediatric cancers diagnosed during 1994-2013, although paediatric brain tumours, lymphomas and rarer cancers were likely under-represented. CONCLUSIONS: Overall, 20 years after the original Community Intervention Program, the pilot study achieved high levels of follow-up and family member interview participation, and identified substantial numbers of paediatric malignancies during 1994-2013 in catchment area hospitals. Next steps and strategies for overcoming limitations are described.


Assuntos
Ácido Fólico/uso terapêutico , Neoplasias/epidemiologia , Defeitos do Tubo Neural/prevenção & controle , Efeitos Tardios da Exposição Pré-Natal/epidemiologia , Complexo Vitamínico B/uso terapêutico , Adolescente , Adulto , Criança , China/epidemiologia , Estudos de Coortes , Suplementos Nutricionais , Estudos de Viabilidade , Feminino , Humanos , Incidência , Masculino , Projetos Piloto , Gravidez , Estudos Prospectivos , População Rural , População Urbana , Adulto Jovem
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