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1.
Phys Chem Chem Phys ; 19(3): 2322-2331, 2017 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-28054686

RESUMO

To reveal a new structure-property relationship regarding the nonlinear optical (NLO) properties of fullerenes that are associated with gamma (γ) density, fullerenes I (C40, C50, C60 and C70), whose heights range from 4.83 to 7.96 Å, and II (C24, C36, C48 and C72), whose widths range from 4.45 to 8.22 Å, have been the research objects. Calculation of their geometric and electronic structures, absorption spectra, and the second hyperpolarizability (γ) and the γ density analysis have been performed. It is found that the electronic spatial extent and the polarizability (α) value increase linearly as the fullerenes increase by every 12 carbon atoms. Similarly, the γ values are also proportional to the fullerene size. It is worth noting that the relative magnitude of γxxxx and γzzzz was exactly consistent with that of the width and height of fullerenes. The analysis of γ density provides the essential reason for this result, that is, the magnitude of the contribution to γ values associated with γ densities is proportional to the density amplitudes multiplied by the distance between them. Larger fullerenes possess larger density amplitudes and longer distances, resulting in larger γ values with respect to smaller fullerenes. This work presents a new structure-property interplay between the width and height of the fullerenes and their second hyperpolarizability γ. Moreover, the γ density analysis provides a new insight to explore the nature of the relationship between the structure and the NLO properties.

2.
ACS Appl Mater Interfaces ; 8(48): 33183-33188, 2016 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-27934177

RESUMO

We designed and fabricated a fluorophore-containing tetradentate carboxylate ligand-based metal-organic framework (MOF) material with open and semiopen channels, which acted as the host for sulfur trapped in Li-S batteries and sensor of benzene homologues. These channels efficiently provide a π-π* conjugated matrix for the charge transfer and guest molecule trapping. The open channel ensured a much higher loading quantitative of sulfur (S content-active material, 72 wt %; electrode, 50.4 wt %) than most of the MOF/sulfur composites, while the semiopen channel possessing aromatic rings tentacles guaranteed an outstanding specific discharge capacity (1092 mA h g-1 at 0.1 C) accompanied by good cycling stability. To our surprise, benefiting from special π-π* conjugated conditions, compound 1 could be a chemical sensor for benzene homologues, especially for 1,2,4-trimethylbenzene (1,2,4-TMB). This is the first example of MOFs materials serving as a sensor of 1,2,4-TMB among benzene homologues. Our works may be worthy of use for references in other porous materials systems to manufacture more long-acting Li-S batteries and sensitive chemical sensors.

3.
J Phys Chem A ; 120(46): 9330-9340, 2016 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-27934245

RESUMO

Zwitterionic complexes have been the subject of great interest in the past several decades due to their multifunctional application in supramolecular chemistry. Herein, a series of internally stable charge-compensated carboranylated square-planar Pt(II) zwitterionic complexes have been explored by density functional theory aim to assessing their structures, the first hyperpolarizabilities, first hyperpolarizability densities, and electronic absorption spectra. It is found that the first hyperpolarizabilities of two-dimensional (2D) structure complexes are much larger with respect to the one-dimensional complex. It is ascribed to the lower transition energy and more obvious charge transfer, which can be further illustrated by their large amplitude and separate distribution of first hyperpolarizability density. In addition, the first hyperpolarizabilities of 2D complexes can be further significantly modified by introducing electron-donating/withdrawing groups on the carborane cage. As a consequence, we believe that these 2D zwitterionic complexes can behave as novel second-order nonlinear optical chromophore with a promising future.

4.
ACS Appl Mater Interfaces ; 7(50): 27959-67, 2015 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-26619747

RESUMO

In this work, the chemical interaction of cathode and lithium polysulfides (LiPSs), which is a more targeted approach for completely preventing the shuttle of LiPSs in lithium-sulfur (Li-S) batteries, has been established on the electrode level. Through simply posttreating the ordinary sulfur cathode in atmospheric environment just for several minutes, the Au nanoparticles (Au NPs) were well-decorated on/in the surface and pores of the electrode composed of commercial acetylene black (CB) and sulfur powder. The Au NPs can covalently stabilize the sulfur/LiPSs, which is advantageous for restricting the shuttle effect. Moreover, the LiPSs reservoirs of Au NPs with high conductivity can significantly control the deposition of the trapped LiPSs, contributing to the uniform distribution of sulfur species upon charging/discharging. The slight modification of the cathode with <3 wt % Au NPs has favorably prospered the cycle capacity and stability of Li-S batteries. Moreover, this cathode exhibited an excellent anti-self-discharge ability. The slight decoration for the ordinary electrode, which can be easily accessed in the industrial process, provides a facile strategy for improving the performance of commercial carbon-based Li-S batteries toward practical application.

5.
J Nanosci Nanotechnol ; 15(12): 9630-5, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26682389

RESUMO

Double carbon-coated LiFePO4 (D-LiFePO4/C) composite with sphere-like structure was synthesized through combination of co-precipitation and solid-state methods. Cetyl-trimethyl-ammonium bromide (CTAB) and citric acid served as two kinds of carbon sources in sequence. SEM images demonstrated that double carbon coating had certain influence on the morphology. The thickness of carbon coating on D-LiFePO4/C was about 1.7 nm and the content of carbon was 2.48 wt%, according to HRTEM and TG analysis. The electrochemical impedance spectroscopy analysis indicated that the D-LiFePO4/C composite presented the charge-transfer resistance of 68 Ω and Li ion diffusion coefficient of 2.68 x 10(-13) cm2 S(-1), while the single carbon-coated LiFePO4 (S-LiFePO4/C) exhibited 135.5Ω and 4.03 x 10(-14) cm2 S(-1). Especially, the prepared D-LiFePO4/C electrode showed discharge capacities of 102.9 (10C) and 87.1 (20C) mA h g(-1), respectively, with almost no capacity lost after 400 cycles at 10C, which were much better than those of S-LiFePO4/C composite.

6.
Phys Chem Chem Phys ; 17(36): 23481-8, 2015 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-26295076

RESUMO

The effect of graphene lateral size on the electrochemical performance of lithium-sulfur (Li-S) batteries is often ignored. In this study, the thermally exfoliated large lateral-sized graphene (denoted LTG) was employed as the conductive matrix to support sulfur, and its performance was then compared with that of a smaller lateral-sized graphene (denoted STG) for Li-S batteries. The results showed that the LTG-S composite exhibited much higher capacity retention (53%) versus the STG-S (29%) and better rate capabilities. Because they were both identical in morphology, in terms of sulfur content and sulfur distribution, the improved properties probably resulted from the potential prevention of polysulfide diffusion upon cycling due to the larger graphene-based network and higher aspect ratio of the LTG matrix, referred as better polysulfide reservoirs. To further improve the cell performance, a reduced graphene oxide-coated carbon fiber paper (RCF) was inserted between the LTG-S cathode and the separator by a simple drop-coat method, which provided an increased conductive surface area for polysulfides to be oxidized/reduced and buffered volume expansion. As expected, the discharge capacities of 1143 and 622 mA h g(-1) at first use and after 100th cycles were obtained with an average Coulombic efficiency of 99.7%, which were higher than 847 and 455 mA h g(-1) for the cathode without the RCF, respectively. This study highlights the significance of large graphene sheets and interlayers on the inhibition of polysulfide diffusion and offers a new way to solve the problems of Li-S batteries.

7.
Phys Chem Chem Phys ; 14(47): 16476-85, 2012 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-23131708

RESUMO

Stimulated by the preparation and characterization of the isolated pentagon rule (IPR) violating chlorofullerene: C(60)Cl(8) (Nat. Mater. 2008, 7, 790-794), we have performed a systematic investigation on the structural stabilities, electronic and optical properties of the IPR-violating C(60)X(8) (X = H, F, and Cl) fullerene compounds via density functional theory. The large energy gaps between the highest occupied and the lowest unoccupied molecular orbitals provide a clear indication of high chemical stabilities of C(60)X(8) derivatives, and moreover, the C(60)X(8) molecules present great aromatic character with the negative nucleus independent chemical shift values. In the addition reactions of C(60) (C(2v)) + 4X(2) → C(60)X(8), a series of exothermic processes are involved, with high reaction energies ranging from -71.97 to -233.16 kcal mol(-1). An investigation on the electronic property shows that C(60)F(8) and C(60)Cl(8) could be excellent electron acceptors as a consequence of large vertical electron affinities. The density of state analysis suggests that the frontier molecular orbitals of C(60)X(8) are mainly from the carbon orbitals of two separate annulene subunits, and the influence from X atoms is secondary. In addition, the ultraviolet-visible spectra and second-order hyperpolarizabilities of C(60)X(8) are calculated by means of time-dependent density functional theory and a finite field approach, respectively. Both the average static linear polarizability <α> and second-order hyperpolarizability <γ> of C(60)X(8) increase greatly compared to those of C(60).

8.
J Mol Graph Model ; 38: 248-55, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23085167

RESUMO

Donor substituted heteroleptic bis-tridentate Ru(II) complexes with different deprotonated forms exhibit larger alterations of the first hyperpolarizabilities in oxidized process and are promising to become redox-switchable nonlinear optical (NLO) molecular materials. For systems with diprotonated form, the ß(vec) value of the two-electron-oxidized system ¹3²âº is 5.3 and 178.6 times as large as those of the reduced parent 3 and the one-electron-oxidized system 3⁺ according to the DFT-FF results. For systems with mono-protonated form, the oxidization of the deprotonated benzimidazole anion is more helpful to enhance the ß(vec) value because of the increasing ß(x) component. For systems with fully deprotonated form, the largest ratio of |ß(vec)((1″)⁺)/ß(vec)(1″)| of the system without substituent is about 13.2 due to the dominant off-diagonal tensor ß(zxx). And the time-dependent density functional theory (TDDFT) results indicate that the charge transfer transition of the first excited state displays an indispensable role for larger off-diagonal tensor. Finally, the calculated frequency-dependent ß results exhibit a small dispersion effect at the low-frequency region.


Assuntos
Complexos de Coordenação/química , Elétrons , Prótons , Rutênio/química , Benzimidazóis/química , Concentração de Íons de Hidrogênio , Modelos Moleculares , Estrutura Molecular , Óptica e Fotônica , Oxirredução , Piridinas/química , Teoria Quântica , Eletricidade Estática
9.
Zhongguo Yi Liao Qi Xie Za Zhi ; 32(2): 97-9, 82, 2008 Mar.
Artigo em Chinês | MEDLINE | ID: mdl-18581871

RESUMO

The design principles of a noninvasive ventilator's turbine are studied and discussed in this paper. The design is completed from its several aspects and in combination of related theories, using SolidWorks tools. Abundant experimental results prove that this design's technical specifications meet all the requirements.


Assuntos
Respiração Artificial/instrumentação , Ventiladores Mecânicos , Desenho de Equipamento , Respiração Artificial/métodos
10.
Zhongguo Yi Liao Qi Xie Za Zhi ; 31(1): 39-43, 2007 Jan.
Artigo em Chinês | MEDLINE | ID: mdl-17432125

RESUMO

The theory of fluorescence resonance energy transfer (FRET) and methods of fluorescence detection in fluorescent-quantitative polymerase chain reaction (FQ-PCR) are introduced in this article. Applications of FRET in fluorescence detection of PCR are emphatically discussed, and FRET research progress and future trends are pointed out too.


Assuntos
Transferência Ressonante de Energia de Fluorescência/métodos , Transferência Ressonante de Energia de Fluorescência/tendências , Reação em Cadeia da Polimerase/métodos
11.
Zhongguo Yi Liao Qi Xie Za Zhi ; 30(6): 437-40, 2006 Nov.
Artigo em Chinês | MEDLINE | ID: mdl-17300014

RESUMO

This paper outlines kinds of index of eyes' optical effect and some different testing methods of intraocular lenses' optical quality.


Assuntos
Lentes Intraoculares , Refratometria/métodos , Testes Visuais/métodos , Humanos , Implante de Lente Intraocular , Sensibilidade e Especificidade
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