Electric-Field-Assisted Directed Assembly of Transition Metal Dichalcogenide Monolayer Sheets
D. D. Deng, Z. Lin, A. L. Elias, N. Perea-Lopez, J. Li, C. Zhou, K. Zhang, S. Feng, H. Terrones, J. S. Mayer, J. A. Robinson, M. Terrones, T. S. Mayer. (2016). “Electric-Field-Assisted Directed Assembly of Transition Metal Dichalcogenide Monolayer Sheets“. ACS Nano, DOI: 10.1021/acsnano.5b03114.
“Directed assembly of two-dimensional (2D) layered materials, such as transition metal dichalcogenides, holds great promise for large-scale electronic and optoelectronic applications. Here, we demonstrate controlled placement of solution-suspended monolayer tungsten disulfide (WS2) sheets on a substrate using electric-field-assisted assembly. Micrometer-sized triangular WS2 monolayers are selectively positioned on a lithographically defined interdigitated guiding electrode structure using the dielectrophoretic force induced on the sheets in a nonuniform field. Triangular sheets with sizes comparable to the interelectrode gap assemble with an observed preferential orientation where one side of the triangle spans across the electrode gap. This orientation of the sheets relative to the guiding electrode is confirmed to be the lowest energy configuration using semianalytical calculations. Nearly all sheets assemble without observable physical deformation, and postassembly photoluminescence and Raman spectroscopy characterization of the monolayers reveal that they retain their as-grown crystalline quality. These results show that the field-assisted assembly process may be used for large-area bottom-up integration of 2D monolayer materials for nanodevice applications.”
Effects of Nitrogen-Doped Multi-Walled Carbon Nanotubes Compared to Pristine Multi-Walled Carbon Nanotubes on Human Small Airway Epithelial Cells
A. L. Mihalchik, W. Ding, D. W. Porter, C. McLoughlin, D. Schwegler-Berry, J. D. Sisler, A. B. Stefaniak, B. N. Snyder-Talkington, R. Cruz-Silva, M. Terrones, S. Tsuruoka, M. Endo, V. Castranova, Y. Qian. (2015). “Effects of nitrogen-doped multi-walled carbon nanotubes compared to pristine multi-walled carbon nanotubes on human small airway epithelial cells“. Toxicology 333, 25-36.
“Nitrogen-doped multi-walled carbon nanotubes (ND-MWCNTs) are modified multi-walled carbon nanotubes (MWCNTs) with enhanced electrical properties that are used in a variety of applications, including fuel cells and sensors; however, the mode of toxic action of ND-MWCNT has yet to be fully elucidated. In the present study, we compared the interaction of ND-MWCNT or pristine MWCNT-7 with human small airway epithelial cells (SAEC) and evaluated their subsequent bioactive effects. Transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction suggested the presence of N-containing defects in the lattice of the nanotube. The ND-MWCNTs were determined to be 93.3% carbon, 3.8% oxygen, and 2.9% nitrogen. A dose–response cell proliferation assay showed that low doses of ND-MWCNT (1.2 μg/ml) or MWCNT-7 (0.12 μg/ml) increased cellular proliferation, while the highest dose of 120 μg/ml of either material decreased proliferation. ND-MWCNT and MWCNT-7 appeared to interact with SAEC at 6 h and were internalized by 24 h. ROS were elevated at 6 and 24 h in ND-MWCNT exposed cells, but only at 6 h in MWCNT-7 exposed cells. Significant alterations to the cell cycle were observed in SAEC exposed to either 1.2 μg/ml of ND-MWCNT or MWCNT-7 in a time and material-dependent manner, possibly suggesting potential damage or alterations to cell cycle machinery. Our results indicate that ND-MWCNT induce effects in SAEC over a time and dose-related manner which differ from MWCNT-7. Therefore, the physicochemical characteristics of the materials appear to alter their biological effects.”
Biotin Molecules on Nitrogen-Doped Carbon Nontubes Enhance the Uniform Anchoring and Formation of Ag Nanoparticles
V. J. González, E. Gracia-Espino, A. Morelos-Gómez, F. López-Urías, H. Terrones, M. Terrones. (2015). “Biotin molecules on nitrogen-doped carbon nanotubes enhance the uniform anchoring and formation of Ag nanoparticles“. Carbon 88, 51-59.
“An efficient method for anchoring silver nanoparticles (Ag-NPs) on the surface of nitrogen-doped multi-walled carbon nanotubes (CNx-MWCNTs) is reported. The process involves the attachment of biotin molecules on the surface of CNx-MWCNTs (both, pristine and acid treated) that act as a reducing agent for AgNO3, thus generating an efficient and homogeneous coating of Ag-NPs (∼3 nm in diameter). The reduction of AgNO3 on either pristine CNx-MWCNTs or acid treated CNx-MWCNTs (without biotin) results in Ag-NPs of large diameters and size distribution, in addition to a low anchoring efficiency. We confirmed that the use of biotin substantially improves the Ag-NPs anchoring efficiency, especially on acid treated CNx-MWCNTs. In order to elucidate the mechanism whereby Ag-NPs strongly bind to the surface of CNx-MWCNTs, density functional theory (DFT) calculations were carried out. These revealed the existence of covalent bonds established between one side of the biotin molecule and the CNx-MWCNT surface through oxygen atoms, leaving accessible the exposed sulfur atoms at the other end, which further provided an excellent interaction with the Ag-NPs via S–Ag bonds. Finally, we demonstrate that these Ag-NPs coated CNx-MWCNTs could be used as efficient sensors of CS2.”
Nitrogen-Doped Graphene: Beyond Single Substitution and Enhanced Molecular Sensing
R. Lv, Q. Li, A. R. Botello-Mendez, T. Hayashi, B. Wang, A. Berkdemir, Q. Hao, A. L. Elias, R. Cruz-Silva, H. R. Gutierrez, Y. A. Kim, H. Muramatsu, J. Zhu, M. Endo, H. Terrones, J. C. Charlier, M. Pan, M. Terrones. (2012). “Nitrogen-doped graphene: beyond single substitution and enhanced molecular sensing“. Scientific Reports 2, 586.
“Graphene is a two-dimensional network in which sp2-hybridized carbon atoms are arranged in two different triangular sub-lattices (A and B). By incorporating nitrogen atoms into graphene, its physico-chemical properties could be significantly altered depending on the doping configuration within the sub-lattices. Here, we describe the synthesis of large-area, highly-crystalline monolayer N-doped graphene (NG) sheets via atmospheric-pressure chemical vapor deposition, yielding a unique N-doping site composed of two quasi-adjacent substitutional nitrogen atoms within the same graphene sub-lattice (N2AA). Scanning tunneling microscopy and spectroscopy (STM and STS) of NG revealed the presence of localized states in the conduction band induced by N2AA-doping, which was confirmed by ab initio calculations. Furthermore, we demonstrated for the first time that NG could be used to efficiently probe organic molecules via a highly improved graphene enhanced Raman scattering.”
Viability Studies of Pure Carbon- and Nitrogen- Doped Nanotubes with Entamoeba Histolytica: From Amoebicidal to Biocompatible Structures
A. L. Elias, J. C. Carrero-Sanchez, H. Terrones, M. Endo, J. P. Laclette, M. Terrones. (2007). “Viability studies of pure carbon- and nitrogen-doped nanotubes with Entamoeba histolytica: from amoebicidal to biocompatible structures“. Small 3, 1723-1729.
“In vitro phagocytosis assays with Entamoeba histolytica as a model system are used to define the biocompatibility of undoped multi-walled carbon nanotubes (MWCNTs) and N-doped (CNx) MWCNTs. The CNx MWCNTs were innocuous to the proliferation of the trophozoites, whereas MWCNTs became lethal. CNx MWCNTs were actively phagocyted by trophozoites with no evidence of cellular damage or distress, in contrast to MWCNTs that induced cellular lysis. The amoebicidal action of pure carbon MWCNTs (see image) could be exploited to develop new tools against amoebiasis.”
Biocompatibility and Toxicology Studies of Carbon Nanotubes Doped with Nitrogen
J. C. Carrero-Sanchez, A. L. Elias, R. Mancilla, G. Arrellin, H. Terrones, J. P. Laclette, M. Terrones. (2006). “Biocompatibility and toxicological studies of carbon nanotubes doped with nitrogen“. Nano Letters 6, 1609-1616.
“In this report, we compare the toxicological effects between pure carbon multiwalled nanotubes (MWNTs) and N-doped multiwalled carbon (CNx) nanotubes. Different doses of tubes were administered in various ways to mice: nasal, oral, intratracheal, and intraperitoneal. We have found that when MWNTs were injected into the mice’s trachea, the mice could die by dyspnea depending on the MWNTs doses. However, CNx nanotubes never caused the death of any mouse. We always found that CNx nanotubes were far more tolerated by the mice when compared to MWNTs. Extremely high concentrations of CNx nanotubes administrated directly into the mice’s trachea only induced granulomatous inflammatory responses. Importantly, all other routes of administration did not induce signs of distress or tissue changes on any treated mouse. We therefore believe that CNx nanotubes are less harmful than MWNTs or SWNTs and might be more advantageous for bioapplications.”