Raman spectroscopy of GaSe and InSe post-transition metal chalcogenides layers

This is the author accepted manuscript. The final version is available on open access from the Royal Society of Chemistry via the DOI in this recordIII-VI post-transition metal chalcogenides (InSe and GaSe) are a new class of layered semiconductors, which feature a strong variation of size and type of their band gaps as a function of number of layers (N). Here, we investigate exfoliated layers of InSe and GaSe ranging from bulk crystals down to monolayer, encapsulated in hexagonal boron nitride, using Raman spectroscopy. We present the N-dependence of both intralayer vibrations within each atomic layer, as well as of the interlayer shear and layer breathing modes. A linear chain model can be used to describe the evolution of the peak positions as a function of N, consistent with first principles calculationsNational Science Centre, PolandEngineering and Physical Sciences Research Council (EPSRC)Scientific and Technological Research Council of Turkey (TUBITAK)Royal SocietySamsung Advanced Institute of Technology (SAIT)European Research Council (ERC

High power Q-switched thulium doped fibre laser using carbon nanotube polymer composite saturable absorber

We have proposed and demonstrated a Q-switched Thulium doped bre laser (TDFL) with a ‘Yin-Yang’ all- bre cavity scheme based on a combination of nonlinear optical loop mirror (NOLM) and nonlinear ampli ed loop mirror (NALM). Unidirectional lasing operation has been achieved without any intracavity isolator. By using a carbon nanotube polymer composite based saturable absorber (SA), we demonstrated the laser output power of ~197 mW and pulse energy of 1.7 μJ. To the best of our knowledge, this is the highest output power from a nanotube polymer composite SA based Q-switched Thulium doped bre laser

Preferential Growth of Semiconducting Single-Walled Carbon Nanotubes on Substrate by Europium Oxide

In this paper, we have demonstrated that europium oxide (Eu2O3) is a new type of active catalyst for single-walled carbon nanotubes (SWNTs) growth under suitable conditions. Both random SWNT networks and horizontally aligned SWNT arrays are efficiently grown on silicon wafers. The density of the SWNT arrays can be altered by the CVD conditions. This result further provides the experimental evidence that the efficient catalyst for SWNT growth is more size dependent than the catalysts themselves. Furthermore, the SWNTs from europium sesquioxides have compatibly higher quality than that from Fe/Mo catalyst. More importantly, over 80% of the nanotubes from Eu2O3 are semiconducting SWNTs (s-SWNTs), indicating the preferential growth of s-SWNTs from Eu2O3. This new finding could open a way for selective growth of s-SWNTs, which can be used as high-current nanoFETs and sensors. Moreover, the successful growth of SWNTs by Eu2O3 catalyst provides new experimental information for understanding the preferential growth of s-SWNTs from Eu2O3, which may be helpful for their controllable synthesis

Transcriptomic Analysis Reveals Novel Mechanistic Insight into Murine Biological Responses to Multi-Walled Carbon Nanotubes in Lungs and Cultured Lung Epithelial Cells

There is great interest in substituting animal work with in vitro experimentation in human health risk assessment; however, there are only few comparisons of in vitro and in vivo biological responses to engineered nanomaterials. We used high-content genomics tools to compare in vivo pulmonary responses of multiwalled carbon nanotubes (MWCNT) to those in vitro in cultured lung epithelial cells (FE1) at the global transcriptomic level. Primary size, surface area and other properties of MWCNT- XNRI -7 (Mitsui7) were characterized using DLS, SEM and TEM. Mice were exposed via a single intratracheal instillation to 18, 54, or 162 μg of Mitsui7/mouse. FE1 cells were incubated with 12.5, 25 and 100 μg/ml of Mitsui7. Tissue and cell samples were collected at 24 hours post-exposure. DNA microarrays were employed to establish mechanistic differences and similarities between the two models. Microarray results were confirmed using gene-specific RT-qPCR. Bronchoalveolar lavage (BAL) fluid was assessed for indications of inflammation in vivo. A strong dose-dependent activation of acute phase and inflammation response was observed in mouse lungs reflective mainly of an inflammatory response as observed in BAL. In vitro, a wide variety of core cellular functions were affected including transcription, cell cycle, and cellular growth and proliferation. Oxidative stress, fibrosis and inflammation processes were altered in both models. Although there were similarities observed between the two models at the pathway-level, the specific genes altered under these pathways were different, suggesting that the underlying mechanisms of responses are different in cells in culture and the lung tissue. Our results suggest that careful consideration should be given in selecting relevant endpoints when substituting animal with in vitro testing

The role of metal nanoparticles in the catalytic production of single-walled carbon nanotubes - A review

Recent progress in chemical vapour deposition and aerosol synthesis of single-walled carbon nanotubes (SWCNTs) is reviewed with an emphasis on the role of metal nanoparticles in the processes. The effect of the various parameters on SWCNT formation is reported on the basis of published experiments. Evolution of the catalyst particle size distribution due to collision, sintering and evaporation of metal during SWCNT synthesis is discussed. The active catalyst has been demonstrated to be in a reduced metal form by comparison of the experimental data and calculations regarding the equilibrium concentration of carbon and oxygen in iron. Also the effect of the catalyst particle size on melting temperature and carbon solubility in metal is discussed. The stability of different carbon precursors (hydrocarbons and carbon monoxide) is considered thermodynamically. Furthermore, estimation of the maximum length of 1 and 2.5 nm diameter SWCNTs as a function of carbon solubility is conducted to determine whether carbon dissolution and precipitation are simultaneous or subsequent process steps

Carbon nanotubes and onions from carbon monoxide using Ni(acac) <inf>2</inf> and Cu(acac)<inf>2</inf> as catalyst precursors

New catalyst precursors (copper and nickel acetylacetonates) have been used successfully for the synthesis of carbon nanotubes and onion particles from carbon monoxide. Catalyst nanoparticles and carbon products were produced by metal-organic precursor vapour decomposition and catalytic disproportionation of carbon monoxide in a laminar flow reactor at temperatures between 705 and 1216°C. Carbon nanotubes (CNTs) were formed in the presence of nickel particles at 923-1216°C. The CNTs were single-walled, 1-3 nm in diameter and up to 90 nm long. Hollow carbon onion particles (COPs) were produced in the presence of copper particles at 1216°C. The COPs were from 5 to 30 nm in diameter and consisted of several concentric carbon layers surrounding a hollow core. The results of computational fluid dynamics calculations to determine the temperature and velocity profiles and mixing conditions of the species in the reactor are presented. The mechanisms for the formation of both CNTs and COPs are discussed on the basis of the experimental and computational results. © Elsevier Ltd. All rights reserved

Carbon nanotube synthesis from alcohols by a novel aerosol method

Single- and multiwalled carbon nanotubes (CNTs) were synthesised by a novel aerosol method using alcohols, namely ethanol and octanol, as carbon precursors. Preformed iron and nickel aerosol nanoparticles, produced by evaporation from resistively heated metal wire, were used as catalysts. Multiwalled CNTs were initiated by 10 nm sized catalyst particles and produced in the presence of ethanol vapour with the partial pressure of 7072 Pa, while combination of 2.4 nm particles and decreased alcohol vapour pressure (123 Pa) resulted in the formation of mainly single-walled and a small fraction of double-walled CNTs. The effect of a promoter (thiophene) in the system was found to be very important for the synthesis of multiwalled CNTs, while only a 30% number concentration increase was found for the single-walled CNT production. © Springer 2006

Carbon nanotube nucleation and growth in gas phase

Catalytic gas-phase synthesis of carbon nanotubes is gaining importance on industrial as well as lab-scale level. The method benefits from being selective toward single, double or multiwalled nanotubes as well as continuous, which makes it suitable for large-scale nanotube production. The nanotube synthesis research has been mainly directed to selectively grow the desired product. However, the fundamental understanding of the growth mechanism of the various nanotube structures has been mostly neglected. This presentation shows detailed experimental data on nucleation and growth of individual nanotubes from iron catalysed CO and ethanol decomposition. Coupling the knowledge of the growth mechanisms of the individual nanotubes with large-scale synthesis is of outmost importance. This presentation also covers the development of a pilot-scale nanotube production unit and describes the high degree of product control achieved in the process

A novel aerosol method for single walled carbon nanotube synthesis

Single walled carbon nanotubes (CNTs) were produced by a novel aerosol method. Catalyst particles were formed by a hot wire generator and introduced into a laminar flow reactor. The size of catalyst particles was approximately 1-3 nm, while the diameter of formed CNTs was 0.6-2 nm. The average length of CNTs was about 50 nm. The important role of hydrogen in the process of CNTs growth was shown. The results of computational fluid dynamics (CFD) calculations to determine the temperature and velocity profiles, mixing conditions of the species in the reactor are presented. Different types of multiwalled CNTs were produced by a CVD method, in which the aerosol introduction of catalyst particles was used. © 2004 Elsevier B.V. All rights reserved