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1.
ACS Sens ; 2020 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-33306358

RESUMO

The emerging applications of electrochemical gas sensors (EGSs) in Internet of Things-enabled smart city and personal health electronics bring out a new challenge for common EGSs, such as alcohol fuel cell sensors (AFCSs) to reduce the dependence on a pricy Pt catalyst. Here, for the first time, we propose a low-cost novel N,S-codoped metal catalyst (FeNSC) to accelerate oxygen reduction reaction (ORR) and replace the Pt catalyst in the cathode of an AFCS. The optimal FeNSC shows high ORR activity, stability, and alcohol tolerance. Furthermore, the FeNSC-based AFCS not only demonstrates excellent linearity, low detection limit, high stability, and superior sensitivity to that of the commercial Pt/C-based AFCS but also outperforms commercial Pt/C-based AFCS in the exposed cell regarding great linearity, high sensitivity, and great stability. Such a promising sensor performance not just proves the concept of the FeNSC-based ACFS but enlightens the next-generation designs toward low-cost, highly sensitive, and durable EGSs.

2.
Int J Clin Exp Pathol ; 13(6): 1361-1371, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32661471

RESUMO

Metastasis is a major risk for lung adenocarcinoma-related mortality. Accumulating evidence raises the possibility that anticancer therapies might be more sensitive by targeting premetastatic niches in addition to the cancer cells themselves. Here, we identified a subpopulation of metastatic lung adenocarcinoma, which was characterized by EMT-related markers such as E-cadherin, Twist, SMAD, and ß-catenin. EMT+ cases exhibited poorer prognosis than EMT- patients, reflecting the pro-metastatic features of EMT. Immunohistochemical staining decorated CD15+ PMN-MDSCs surrounding EMT+ cancer cells in lymph nodes. Metastatic tissues secreted high levels of chemokines, including CXCL1, CXCL5, and CCL2, into the circulation to recruit histidine decarboxylase (Hdc)-positive PMN-MDSCs into metastatic colonies through upregulated CXCR2. The percentage of Hdc+ PMN-MDSCs increased in the setting of metastasis. Hdc+ PMN-MDSCs obtained from EMT+ metastatic masses expressed a higher level of TGF-ß1, rather than TGF-ß2 and TGF-ß3, compared to EMT- counterparts. The depletion of Hdc+ PMN-MDSCs or downregulation of TGF-ß1 significantly decreased EMT+ percentage and, thus, hampered the metastasis process in murine models. Together, our findings suggest that metastatic tumor secretes high levels of chemokines to recruit Hdc+ PMN-MDSCs, which, in turn, express TGF-ß1 to induce cancer cells to undergo EMT at metastatic sites.

3.
J Insect Sci ; 20(3)2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32559298

RESUMO

The rice stem borer, Chilo suppressalis (Walker), and the rice leaf folder, Cnaphalocrocis medinalis Guenée, are two of the most destructive lepidopteran pests in rice. Since these two pyralid insects overlap in their occurrence in rice paddy fields, farmers prefer to set their pheromone-baited traps together in the rice fields for their monitoring. However, our field observation demonstrated that no male adult of C. suppressalis was captured in traps baited with commercial sex pheromone of C. suppressalis (CCS) combined with commercial sex pheromone of C. medinalis (CCM). To confirm that the C. medinalis sex pheromone component(s) interfere with the attraction of males of the rice stem borers to their conspecific females, single components of C. medinalis sex pheromone combined with CCS in traps were tested in the laboratory and rice paddy field. The results revealed that the two alcohol components in CCM, i.e., (Z)-11-octadecen-1-ol (Z11-18: OH) and (Z)-13-octadecen-1-ol (Z13-18: OH) may cause a significant reduction in capturing C. suppressalis males caused by CCS. We recommend against using these sex pheromones together in the field and suggest that Z11-18: OH and Z13-18: OH could be potential inhibitors or antagonists of C. suppressalis sex pheromone to control the rice stem borer.


Assuntos
Controle de Insetos , Mariposas/fisiologia , Controle Biológico de Vetores , Atrativos Sexuais/farmacologia , Comportamento Sexual Animal/efeitos dos fármacos , Animais , Mariposas/efeitos dos fármacos
4.
Artigo em Inglês | MEDLINE | ID: mdl-32271975

RESUMO

Pt-based electrocatalysts are considered as one of the most promising choices to facilitate the oxygen reduction reaction (ORR), and the key factor enabling their success is to reduce the required amount of platinum. Herein, we focus on illuminating both the theoretical mechanisms which enable enhanced and sustained ORR activity and the practical methods to achieve them in catalysts. The various multi-step pathways of ORR are firstly reviewed and the rate-determining steps based on the reaction intermediates and their binding energies are analyzed. We then explain the critical aspects of Pt-based electrocatalysts to tune oxygen reduction properties from the viewpoints of active sites exposure and altering the surface electronic structure, and further summarize representative research progress towards practically achieving these activity enhancements with a focus on platinum size reduction, shape control and core Pt elimination methods. We finally outline the remaining challenges and provide our perspectives with regard to further enhancing their activities.

5.
Adv Mater ; 29(7)2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27982465

RESUMO

Rich, porous graphene frameworks decorated with uniformly dispersed active sites are prepared by using polyaniline as a graphene precursor and introducing phenanthroline as a pore-forming agent. The unprecedented fuel-cell performance of this electrocatalyst is linked to the graphene frameworks with vast distribution of pore sizes, which maximizes the active-sites accessibility, facilitates mass-transport properties, and improves the carbon corrosion resistance.

6.
ACS Appl Mater Interfaces ; 8(10): 6488-95, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26937737

RESUMO

Nitrogen-functionalized graphene materials have been demonstrated as promising electrocatalyst for the oxygen reduction reaction (ORR), owning to their respectable activity and excellent stability in alkaline electrolyte. However, they exhibit unacceptable catalytic activity in acid medium. Here, a hierarchically porous Co-N functionalized graphene aerogel is prepared as an efficient catalyst for the ORR in acid electrolyte. In the preparation process, polyaniline (PANI) is introduced as a pore-forming agent to aid in the self-assembly of graphene species into a porous aerogel networks, and a nitrogen precursor to induce in situ nitrogen doping. Therefore, a Co-N decorated graphene aerogel framework with a large surface area (485 m(2) g(-1)) and an abundance of meso/macropores is effectively formed after heat treatment. Such highly desired structures can not only expose sufficient active sites for the ORR but also guarantee the fast mass transfer in the catalytic process, which provides significant catalytic activity with positive onset and half wave potentials, low hydrogen peroxide yield, high resistance to methanol crossover, and remarkable stability that is comparable to commercial Pt/C in acid medium.

7.
ACS Appl Mater Interfaces ; 6(6): 3930-6, 2014 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-24598249

RESUMO

The large-scale synthesis of nitrogen doped graphene (N-graphene) with high oxygen reduction reaction (ORR) performance has received a lot of attention recently. In this work, we have developed a facile and economical procedure for mass production of edge-nitrogen-rich graphene nanoplatelets (ENR-GNPs) by a combined process of ball milling of graphite powder (GP) in the presence of melamine and subsequent heat treatment. It is found that the ball milling process can not only crack and exfoliate pristine GP into edge-expanded nanoplatelets but also mechanically activate GP to generate appropriate locations for N-doping. Analysis results indicate that the doped N atoms mainly locate on the edge of the graphitic matrix, which contains ca. 3.1 at.% nitrogen content and can be well-dispersed in aqueous to form multilayer nanoplatelets. The as-prepared ENR-GNPs electrocatalyst exhibits highly electrocatalytic activity for ORR due to the synergetic effects of edge-N-doping and nanosized platelets. Besides, the stability and methanol tolerance of ENR-GNPs are superior to that of the commercial Pt/C catalyst, which makes the nanoplatelets a promising candidate for fuel cell cathode catalysts. The present approach opens up the possibility for simple and mass production of N-graphene based electrocatalysts in practice.

8.
ACS Nano ; 8(4): 3313-21, 2014 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-24601550

RESUMO

Two-dimensional materials based on ternary system of B, C and N are useful ranging from electric devices to catalysis. The bonding arrangement within these BCN nanosheets largely determines their electronic structure and thus chemical and (or) physical properties, yet it remains a challenge to manipulate their bond structures in a convenient and controlled manner. Recently, we developed a synthetic protocol for the synthesis of crumpled BCN nanosheets with tunable B and N bond structure using urea, boric acid and polyethylene glycol (PEG) as precursors. By carefully selecting the synthesis condition, we can tune the structure of BCN sheets from s-BCN with B and N bond together to h-BCN with B and N homogenously dispersed in BCN sheets. Detailed experiments suggest that the final bond structure of B and N in graphene depends on the preferentially doped N structure in BCN nanosheets. When N substituted the in-plane carbon atom with all its electrons configured into the π electron system of graphene, it facilitates the formation of h-BCN with B and N in separated state. On the contrary, when nitrogen substituted the edge-plane carbon with the nitrogen dopant surrounded with the lone electron pairs, it benefits for the formation of B-N structure. Specially, the compound riched with h-BCN shows excellent ORR performance in alkaline solution due to the synergistic effect between B and N, while s-BCN dominant BCN shows graphite-like activity for ORR, suggesting the intrinsic properties differences of BCN nanosheets with different dopants bond arrangement.

9.
ACS Appl Mater Interfaces ; 5(21): 11108-14, 2013 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-24099362

RESUMO

Designing and fabricating advanced oxygen reduction reaction (ORR) electrocatalysts is critical importance for the sake of promoting widespread application of fuel cells. In this work, we report that nitrogen-doped graphene (NG), synthesized via one-step pyrolysis of naturally available sugar in the presence of urea, can serve as metal-free ORR catalyst with excellent electrocatalytic activity, outstanding methanol crossover resistance as well as long-term operation stability in alkaline medium. The resultant NG1000 (annealed at 1000 °C) exhibits a high kinetic current density of 21.33 mA/cm(2) at -0.25 V (vs Ag/AgCl) in O2-saturated 0.1 M KOH electrolyte, compared with 16.01 mA/cm(2) at -0.25 V for commercial 20 wt % Pt/C catalyst. Notably, the NG1000 possesses comparable ORR half-wave potential to Pt/C. The effects of pyrolysis temperature on the physical prosperity and ORR performance of NG are also investigated. The obtained results demonstrate that high activation temperature (1000 °C) results in low nitrogen doping level, high graphitization degree, enhanced electrical conductivity, and high surface area and pore volume, which make a synergetic contribution to enhancing the ORR performance for NG.

10.
ACS Nano ; 7(6): 4764-73, 2013 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-23647240

RESUMO

Nitrogen-doped graphene sheets (NGS), synthesized by annealing graphite oxide (GO) with urea at 700-1050 °C, were studied as positive electrodes in a vanadium redox flow battery. The NGS, in particular annealed at 900 °C, exhibited excellent catalytic performance in terms of electron transfer (ET) resistance (4.74 ± 0.51 and 7.27 ± 0.42 Ω for the anodic process and cathodic process, respectively) and reversibility (ΔE = 100 mV, Ipa/Ipc = 1.38 at a scan rate of 50 mV s(-1)). Detailed research confirms that not the nitrogen doping level but the nitrogen type in the graphene sheets determines the catalytic activity. Among four types of nitrogen species doped into the graphene lattice including pyridinic-N, pyrrolic-N, quaternary nitrogen, and oxidic-N, quaternary nitrogen is verified as a catalytic active center for the [VO](2+)/[VO2](+) couple reaction. A mechanism is proposed to explain the electrocatalytic performance of NGS for the [VO](2+)/[VO2](+) couple reaction. The possible formation of a N-V transitional bonding state, which facilitates the ET between the outer electrode and reactant ions, is a key step for its high catalytic activity.

11.
J Org Chem ; 74(11): 4149-57, 2009 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-19391614

RESUMO

A convergent, enantioselective and general synthetic route to a class of marine natural products-malyngamides O (1), P (2), Q (3), R (4), 5''-epi-3 and 5''-epi-4-bearing a novel vinyl chloride structural motif was developed. The key steps involved construction of the vinyl chloride functionality by Wittig reaction, a DCC/HOBt-promoted amidation, an aldol reaction in the construction of the basic backbone of 1, 2, 3, 4, 5''-epi-3, and 5''-epi-4, and methylation of an enol moiety via either base/acid conditions or a Mitsunobu reaction. Moreover, the absolute configuration of the stereogenic center at C-5'' in 3 was further confirmed by synthesis of the natural product and its C-5'' epimer.


Assuntos
Ácidos Acíclicos/síntese química , Alcenos/síntese química , Ácidos Acíclicos/química , Alcenos/química , Amidas , Produtos Biológicos/síntese química , Produtos Biológicos/química , Pirróis , Estereoisomerismo , Cloreto de Vinil
12.
Zhongguo Yi Liao Qi Xie Za Zhi ; 32(6): 413-5, 2008 Nov.
Artigo em Chinês | MEDLINE | ID: mdl-19253572

RESUMO

The combination of the cryosurgery using LN2 and intelligent RF ablation therapeutic instrument based on the theory of local destruction is introduced in this paper, and this alternating therapy is believed to have a better controlling effect on tumor ablation. In heating period, a fuzzy algorithm is used to control the RF power to realize a more smoothly heating process to the target area.


Assuntos
Ablação por Cateter/instrumentação , Criocirurgia/instrumentação , Hipertermia Induzida/instrumentação , Neoplasias/cirurgia , Ablação por Cateter/métodos , Desenho de Equipamento , Humanos , Hipertermia Induzida/métodos
13.
Chemistry ; 12(20): 5238-45, 2006 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-16607672

RESUMO

Bichromophoric compounds BP-C-NP and BP-C-NBD were synthesized with benzophenone chromophore (BP) as the donor, and 2-naphthyl (NP) and norbornadiene group (NBD) as the acceptor, respectively. Their intramolecular triplet energy transfer was examined. The bridges linking the donor and acceptors in these molecules involve a crown ether moiety complexing a sodium ion. Phosphorescence quenching, flash photolysis and photosensitized isomerization experiments indicate that intramolecular triplet energy transfer occurs with rate constants of about 3.3 x 10(5) and 4.8 x 10(5) s(-1) and efficiencies of about 33 and 42 % for BP-C-NP and BP-C-NBD, respectively. Theoretical calculations indicate that these molecules adopt conformations below room temperature which allow their two-end chromophores conducive to through-space energy transfer.

14.
Org Lett ; 5(7): 1075-7, 2003 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-12659577

RESUMO

[reaction: see text] Nanosized particles of modified silica with 3-ammoniumpropyl residue have been prepared and successfully used as microreactors to control the regioselectivity of the photocycloaddition of five 9-substituted anthracences [AnCH(2)N(+)(CH(3))(3)Br(-) (1), AnCH(2)COO(-)Na(+) (2), AnCH(2)CH(2)COOH (3), AnCH(2)OH (4), AnCH(3) (5), where An = 9-anthryl]. While the photocycloaddition of the five substrates in methanol mainly gave rise to their head-to-tail (h-t) photocyclomers, irradiation of 1-4 incorporated in the suspension of the modified silica in methanol almost exclusively yielded the head-to-head (h-h) photocyclomers with high quantum yields.

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