Showing papers by "Xingfa Gao published in 2014"
TL;DR: Direct evidence is provided that low concentrations of pristine graphene and graphene oxide show no apparent influence on the viability of MDA-MB-231 human breast cancer cells, PC3 human prostate cancer Cells, as well as B16F10 mouse melanoma cells, but both pristine grapheneand graphene oxide can effectively inhibit the migration and invasion of these cancer cells.
161 citations
TL;DR: In this article, nonequilibrium quantum chemical molecular dynamics simulation of early stages in the nucleation process of carbon nanotubes from acetylene feedstock on an Fe-38 cluster was performed based on the density-functional tight-binding (DFTB) potential.
51 citations
TL;DR: In this paper, the acidity and reducibility of 13C-labeled C60 fullerenols were investigated using density functional theory calculations, and a structural model was proposed to interpret the main IR and NMR spectroscopic and electronically paramagnetic properties.
Abstract: Fullerenol is one of the main precursors of fullerene-based materials, which is promising for various biological applications because of its unusual biocompatibility and biofunctionality. However, the functional groups, acidity and reducibility, which substantialize the applications of fullerenols, remain open questions. Using density functional theory calculations, we investigated reaction mechanisms underlying the acidity and reducibility of C60 fullerenols. On the basis of theoretical insights combined with synthesis, IR and NMR structural characterization of 13C-labeled C60 fullerenols, we identified the functional groups and developed and verified a structural model for C60 fullerenols. The results show a strong dependence of acidity and reducibility on the hydroxyl distributions of fullerenols. Fullerenols with stable π-electron configurations on C60 cores, in which no double bonds have to be placed in conjugated pentagonal rings when drawing their Kekule structures, have low acidities and reducibilities. Contrarily, fullerenols with unstable π-electron configurations have high acidities and reducibilities. For fullerenols with different hydroxyl distributions, the calculated acid dissociation constants range from −17.55 to 15.21, and the calculated redox potentials range from −0.87 to 1.32 V. Hydroxyls with high acidities and reducibilities unlikely survive in fullerenols synthesized using alkali, oxidizing conditions. Instead, they exist as the corresponding conjugate bases or oxidized products. This structural prediction agrees with our NMR results and the previous experiments. The proposed structural model is able to interpret the main IR and NMR spectroscopic and electronically paramagnetic properties of C60 fullerenols without the disadvantages of the previous models.
43 citations
TL;DR: In this article, the authors used density functional theory to study the reaction mechanisms of chemical reduction of graphene oxide (GO) by the sulfur-containing compounds HSO 3 − and H 2 SO 3.
29 citations
TL;DR: The ITO/Gd@C82-PVK/Al sandwich nonvolatile memory device was developed based on polymer containing carbazole moieties as electron donors and Gd@c82 as electron acceptors for the first time.
13 citations
TL;DR: In this article, a 13C-C60 sample was synthesized by arc discharge method with the stable isotope 13C direct substituting the skeleton carbon atoms on the carbon cage.
Abstract: In the last three decades, due to the unique structure and biological activities of fullerene materials, many reports were published on their synthesis and application in biomedical and environmental sciences, however, there is very few examples that have leapt out of the laboratory and into the commercial market. Obviously, further study is required to solve their crucial biological safety issues. In this article, the 13C-C60 sample was synthesized by arc discharge method with the stable isotope 13C direct substituting the skeleton carbon atoms on the carbon cage. The numbers of the incorporated 13C-atoms have been identified by isotope ratio mass spectroscopy. The isotope effect of the skeleton 13C-enriched C60 made its mass spectrum and vibrational Infrared/Raman spectra changes. Its mass spectra peaks at range from m / z =719~734 showed the normal distribution and the strongest peak position shifted up with the increase number of 13C. Infrared and Raman spectra of 13C-C60 retained the characteristic spectrum of C60, however, due to the stable isotope 13C-incorporated reducing C60 molecular symmetry, the characteristic peaks occurred the migration and splitting with increasing the number of 13C. Simultaneously, the 13C direct labeling method does not destroy the intrinsic structure of fullerene. Undoubtedly, 13C-C60 will open the door for quantitatively, safely and non-destructively evaluating on the biological safety of fullerene nanomaterials in vivo .
9 citations
TL;DR: The free-energy of C70-corrole calculated by employing the redox potentials and singlet excited-state energy suggested the possibility of electron transfer from the excited singlet state of corrole to the fullerene entity, which agreed with the results of the theoretical calculation.
Abstract: A new electron transfer dyad, covalently linked C-70-corrole, was prepared via C-70 and 10-(4-Formylaryl)-5,15-bis(pentafluorophenyl). The structures and the properties of the new material were investigated by HPLC, MALDI-TOF-MS, UV-Vis-NIR spectroscopy, NMR, fluorescence analysis and CV/DPV. The free-energy of C-70-corrole calculated by employing the redox potentials and singlet excited-state energy suggested the possibility of electron transfer from the excited singlet state of corrole to the fullerene entity, which agreed with the results of the theoretical calculation.
4 citations
TL;DR: In this paper, the impact of surface passivation of nanocrystals on the quantum boundary effect was investigated and the view of the traditional effective mass model was extended to include the QSE, which opens a new degree of freedom in engineering the electronic and optoelectronic properties of nanomaterials.
Abstract: Quantum size effect (QSE) is of central importance in nanoscience. For semiconductors, it is generally perceived that the QSE raises the band gap of a nanocrystal by effectively increasing the kinetic energies of electrons and holes. Using first-principles calculations and Si nanofilms as a test case, we investigated the impact of surface passivation of nanocrystals on the QSE and extended the view of the traditional QSE, as depicted in the classic effective mass model, to include the quantum boundary effect. We showed that the band gap of Si nanofilms is critically affected by the passivation species at the surface, which could result in not only the commonly observed increase in band gap but also a decrease with respect to the bulk value. The Si nanofilms can have a band gap that is virtually the same as that of bulk Si when film thickness is less than 2 nm. The new understanding of the QSE opens a new degree of freedom in engineering the electronic and optoelectronic properties of nanomaterials.
2 citations