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Graphical abstract Highlights • Noncovalent interactions between phthalocyanines and SWNTs are very strong. • Macrocycles suffer strong bending distortion on nanotube sidewalls. • Calculated HOMO-LUMO gap energies are very low. • Frontier orbital distribution pattern depends on the central metal ion. • Phthalocyanine deposition onto SWNTs results in simplified XPS N 1s spectra. Abstract We performed a combined density functional theory (DFT) and X-ray photoelectron spectroscopy (XPS) study of noncovalently bonded hybrids of 3 d metal phthalocyanines MePcs (where M = Co, Ni, Cu and Zn) and single-walled carbon nanotubes (SWNT). The results of both DFT calculations (PBE functional in conjunction with the dispersion correction by Grimme and DNP basis set) and comparative XPS spectral measurements for neat MePcs and MePc+SWNT hybrids suggest very strong interactions between macrocyclic complexes and carbon nanotube sidewalls. DFT calculations produced very high absolute values of binding energies of 32.74–45.35 kcal/mol (depending on MePc and nanotube model). The macrocycles (planar in neat MePcs) suffer strong bending distortion in order to increase the area of their contact with nanotube sidewall. In many cases, N...C SWNT (and not Me...C SWNT) distances turn to be the closest approaches between MePc and SWNT model, where the nitrogen atoms forming them can be either one of the N atoms belonging to MeN 4 coordination sphere, or one of the γ-N atoms, with some of C MePc ...C SWNT closest approaches comparable in length with the shortest N...C SWNT distances. The calculated HOMO-LUMO gap energies are very low, from 0.007 to 0.622 eV only. The pattern of HOMO-LUMO distribution found in most cases is different from the one typically observed for noncovalent dyads of Pcs and porphyrins with carbon nanoclusters (fullerenes and carbon nanotubes), where HOMO is localized on the macrocyclic component and LUMO, on carbon nanocluster. The experimental XPS measurements found the existence of only one N 1s component for noncovalent MePc+SWNT complexes versus three components for neat phthalocyanine β-polymorphs, as well as the decrease of multiplet splitting and the increase of spectral resolution observed for both N 1s and Me 2p peaks as a result of phthalocyanine deposition onto SWNTs. [ABSTRACT FROM AUTHOR]

Abstract In this work, the photoelectrochemical response of single-walled (SW) and double-walled (DW) TiO 2 nanotube (TNT) layers is presented. TNT layers were grown on Ti substrates by anodization in two different ethylene glycol-based electrolytes to obtain ~5 and ~15 μm thick TNT layers. The inner shell of the TNT was quantitatively removed via a mild pre-annealing followed by a selective chemical etching treatment in piranha solution. All TNT layers were investigated for their photoelectrochemical response in the ultraviolet and near visible spectral range. Significantly enhanced photocurrent densities were revealed for the SW-TNT layers. This is ascribed to improved charge carrier separation along the tube walls due to the lack of the C- and F-rich inner shell removed by etching. Highlights • Two different double-wall anodic TiO 2 nanotube layers were investigated in this work. • Chemical etching was employed to remove the inner wall of anodic TiO 2 nanotubes. • Single-wall nanotubes show increased photocurrents compared to double-wall ones. • TGA done in air to 1000 °C revealed stronger loss of C-species for thicker layers. • Single wall nanotube layers are more suitable for photo-electrochemical applications. [ABSTRACT FROM AUTHOR]

This paper presents results on the crushing behavior of aluminum foam–filled columns with square cross section. Here, the effect of inserting an aluminum foam to single–walled and double–walled columns were studied. Parametric study for both types of columns compared with single–walled and double–walled columns were also carried out. In this work, the effect of strain rate of the aluminum foam was considered in the material model. The numerical results were compared with the available experimental data and shown to be in a very good agreement. The models that considered the strain rate effect of foam core gave better predictions compared to the ones without considering the strain rate effect. It will result in higher energy absorption and bigger local deformation on corners resulting a slightly increase of the overall crushing force. It can be said that the strain rate of the foam core plays a quite significant role in crushing behavior of the foam-filled columns, and should be taken into account. The results also showed that the interaction between the foam core and the column wall will change the deformation mode from one localized fold to multiple propagating folds and lead to the increase of total mean crushing force of the column. Similar effect of foam filling was also found in double–walled foam–filled columns. Further investigation has been conducted on the effect of core thickness to the mean crushing force response of the columns. It is also found that increasing the core thickness in double–walled foam–filled column will improve the crushing behavior up to a point where there is still interaction between the walls. After that, the further increase of the core thickness will make the column response approaching the crushing force of single–walled foam–filled. [ABSTRACT FROM AUTHOR]

Noncovalent hybrids of carbon nanotubes (CNTs) with phthalocyanines (Pcs) is a subject of growing research effort focused on the development of new efficient organic photovoltaic cells, heterogeneous catalysts, lithium batteries, gas sensors, field effect transistors, among other possible applications. The main advantage of using unsubstituted Pcs is their very moderate cost and easy commercial availability. Unfortunately, the deposition of unsubstituted Pcs onto CNT sidewalls via the traditional liquid-phase strategy proves to be very problematic due to an extremely poor solubility of Pcs. At the same time, unsubstituted free-base H 2 Pc ligand and many of its transition metal complexes exhibit high thermal stability and volatility under reduced pressure, which allows for their physical vapor deposition onto solid surfaces. In the present work, we demonstrated the possibility of simple, fast, efficient and environmentally friendly noncovalent functionalization of single-walled CNTs (SWNTs) with a series of 3 d metal(II) phthalocyanines Me(II)Pc, where Me = Co, Ni, Cu and Zn. The functionalization can be performed at 400–500 °C under moderate vacuum, and takes about 2–3 h only. The nanohybrids obtained were characterized by means of Fourier-transform infrared, Raman, UV–vis and energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), scanning and transmission electron microscopy. TGA suggested that Pc weight content is 30%, 17% and 35% for NiPc, CuPc and ZnPc, respectively (CoPc exhibited anomalous behavior), which is close to the estimates from EDS spectra of 24–39%, 27–36% and 27–44% for CoPc, CuPc and ZnPc, respectively. A strong increase in intensity of D band in the Raman spectra of SWNT‒Pc hybrids, as compared to that of pristine nanotubes, was interpreted as very strong interactions between Pc molecules and SWNT sidewalls. Very high absolute values of binding energies of 32.46–37.12 kcal/mol and the patterns of HOMO and LUMO distribution, calculated at the PBE-D/DNP level of density functional theory, also suggested that the interactions between metal phthalocyanines studied and nanotube sidewalls are very strong. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate the feasibility of realization of transparent gas sensors based on carbon nanotubes (CNTs). Both sensing layer and electrodes consist of CNTs deposited by spray deposition. The transparent sensor—with a transmittance higher than 60% in both sensing layer and electrodes—is characterized towards NH3 and CO2 and compared with a reference sensor with the same active layer but evaporated Au electrodes. In particular, the sensitivity towards NH3 is virtually identical for both reference and transparent sensors, whereas the transparent device exhibits higher sensitivity to CO2 than the reference electrode. The effect of the spacing among consecutive electrodes is also studied, demonstrating that a wider spacing in fully CNT based sensors results in a higher sensitivity because of the higher sensing resistance, whereas this effect was not observed in gold electrodes, as their resistance can be neglected with respect to the resistance of the CNT sensing layer. Overall, the transparent sensors show performance comparable—if not superior—to the traditionally realized ones, opening the way for seamlessly integrated sensors, which do not compromise on quality.

Single-walled carbon nanotubes (SWCNTs) are carbon-based nanomaterials that possess immense industrial potential. Despite accumulating evidence that exposure to SWCNTs might be toxic to humans, our understanding of the mechanisms for cellular toxicity of SWCNTs remain limited. Here, we demonstrated that acute exposure of short (1–3 μm) and regular-length (5–30 μm) pristine, carboxylated or hydroxylated SWCNTs inhibited cell proliferation in human somatic and human stem cells in a cell type-dependent manner. The toxicity of regular-length pristine SWCNT was most evidenced in NP69 > CYT00086 > MCF-10A > MRC-5 > HaCaT > HEK-293 T > HepG2. In contrast, the short pristine SWCNTs were relatively less toxic in most of the cells being tested, except for NP69 which is more sensitive to short pristine SWCNTs as compared to regular-length pristine SWCNTs. Interestingly, carboxylation and hydroxylation of regular-length SWCNTs, but not the short SWCNTs, significantly reduced the cytotoxicity. Exposure of SWCNTs also induced caspase 3 and 9 activities, mitochondrial membrane depolarization, and significant apoptosis and necrosis in MRC-5 embryonic lung fibroblasts. In contrast, SWCNTs inhibited the proliferation of HaCaT human keratinocytes without inducing cell death. Further analyses by gene expression profiling and Connectivity Map analysis showed that SWCNTs induced a gene expression signature characteristic of heat shock protein 90 (HSP90) inhibition in MRC-5 cells, suggesting that SWCNTs may inhibit the HSP90 signaling pathway. Indeed, exposure of MRC-5 cells to SWCNTs results in a dose-dependent decrease in HSP90 client proteins (AKT, CDK4 and BCL2) and a concomitant increase in HSP70 expression. In addition, SWCNTs also significantly inhibited HSP90-dependent protein refolding. Finally, we showed that ectopic expression of HSP90, but not HSP40 or HSP70, completely abrogated the cytotoxic effects of SWCNTs, suggesting that SWCNT-induced cellular toxicity is HSP90 dependent. In summary, our findings suggest that the toxic effects of SWCNTs are mediated through inhibition of HSP90 in human lung fibroblasts and keratinocytes. [ABSTRACT FROM AUTHOR]

• Sprayed single-walled CNT for gas sensors. • Characterization over ammonia from 10 to 100 ppm. • Aging over 4 years with retainment of up to 96%. In this communication, we report on the long-term stability of a carbon nanotube (CNT) thin-film based NH 3 gas sensor. These sensors were fabricated with a reproducible, large-scale, low-cost spray deposition process and are examined in terms of NH 3 sensitivity and long-term stability. The devices are measured directly after fabrication; 1-year and 4-years post fabrication while being stored in ambient conditions without further encapsulation. The retainment of up to 96% of response demonstrates the stability of such CNT-based devices. Hence, it solves a critical issue for stepping beyond the proof of concept stage. Not only can CNT-based gas sensors be utilized for years, but such sensors also do not require any special recalibration over the years. [ABSTRACT FROM AUTHOR]

Ultraviolet and infrared transmission measurements on an unoriented single-wall (SWCNTs) and multi-wall (MWCNTs) carbon nanotubes films were performed over a frequency range 190–2500 nm for the four different films. A clear change in the fine structure of the infrared spectrum for different films. The higher-energy optical absorption bands, which correspond to transitions across the Van Hove singularities, are not observed in the measured frequency range in the case of MWCNTs films. The broad excitation in the low-energy range below 0.025 eV (Drude peak ( E M0 )) are attributed to the contributions from metallic carriers localized in a finite length. This Drude peak ( E M0 ) at low-energies is decreased in in case of MWCNTs, which suggests a progressive transition of metallic tubes to insulating state. The unoriented MWCNTs films have an average thickness of about 200–400 nm. The scanning electron microscope pictures of the SWCNTs and the MWCNTs films illustrate the morphological differences between the four studied samples. The volume fraction of the carbon nanotubes in all films appears to be the same, although there is a difference for particles other than nanotubes in the films. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) are an important class of nanomaterials, which have numerous novel properties that make them useful in technology and industry. Generally, there are two types of CNTs: single-walled nanotubes (SWNTs) and multi-walled nanotubes. SWNTs, in particular, possess unique electrical, mechanical, and thermal properties, allowing for a wide range of applications in various fields, including the electronic, computer, aerospace, and biomedical industries. However, the use of SWNTs has come under scrutiny, not only due to their peculiar nanotoxicological profile, but also due to the forecasted increase in SWNT production in the near future. As such, the risk of human exposure is likely to be increased substantially. Yet, our understanding of the toxicological risk of SWNTs in human biology remains limited. This review seeks to examine representative data on the nanotoxicity of SWNTs by first considering how SWNTs are absorbed, distributed, accumulated and excreted in a biological system, and how SWNTs induce organ-specific toxicity in the body. The contradictory findings of numerous studies with regards to the potential hazards of SWNT exposure are discussed in this review. The possible mechanisms and molecular pathways associated with SWNT nanotoxicity in target organs and specific cell types are presented. We hope that this review will stimulate further research into the fundamental aspects of CNTs, especially the biological interactions which arise due to the unique intrinsic characteristics of CNTs. [ABSTRACT FROM AUTHOR]

In the present work we report significant enhancement of the photoelectrochemical properties of self- organized TiO2 nanotubes by a combined 'de-coring' of classic nanotubes followed by an appropiate TiCl4 treatment. We show that, except for the expected particle decoration, a key effect of the TiCl4 treatment is that the electron transport characteristics in TiO2 nanotubes can be drastically improved, for example, we observe an enhancement of up to 70 % in electron-transport times. [ABSTRACT FROM AUTHOR]

In this work, we have studied the temperature dependence from 83 to 1300 K in the change of position of Raman modes in single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). The effects of synthesis on the quality and quantity of carbon nanotubes (CNTs) were analyzed with high-resolution scanning electron microscopy (SEM) and micro-Raman spectroscopy. The behavior of the modes G for CNTs with the application of temperatures was studied, and we find that the (G)-peak position shifts to low frequency with increasing temperature. When reducing the ambient temperature to 83 K, there is displacement of the G-mode but not many changes were observed in the other modes. At high temperatures, there are changes in the position and intensity of the different modes. This behavior cannot be understood by purely thermal effects, it may also be due to uniaxial tension. The analysis of the experimental data showed the temperature dependencies of frequencies (w) and linewidths (FWHM). As a result of FWHM and the thermal expansion theoretical data, we calculated the Grüneisen parameter and the phonon decay rate, which are well described, taking into account the contributions from thermal expansion and anharmonicity. [ABSTRACT FROM AUTHOR]

This paper presents a numerical and experimental study of several configurations of multi-cell columns compared to single-walled and double-walled columns subjected to dynamic axial impact forces. The impact of the columns was numerically analysed using FEM and also verified by experimental testing. The effect of the column mass and thickness of the multi-cell columns compared to single- and double-walled columns was also studied. The results showed that, by analysing a group of columns with the same thickness and weight, the energy absorption efficiency can be significantly improved by introducing internal ribs to the double-walled columns. The results showed that the crushing force of the middle ribs (MR) multi-cell columns was the highest, followed by the corner ribs (CR) multi-cell columns, the double-walled (DW) columns and the single-walled (SW) columns, respectively. [ABSTRACT FROM AUTHOR]

In many computational studies of carbon nanotubes, the minimum energy configuration frequently settles on a structure for which the bond lengths are distinct. Here, we extend both the rolled-up and the polyhedral models for SWCNTs to produce general models incorporating either distinct bond lengths and the same bond angle, or distinct bond lengths and distinct bond angles. The CNTs considered here are assumed to be formed by sp2 hybridization but with different bond lengths so that the nanotube structure is assumed to comprise irregular hexagonal patterns. The polyhedral model with distinct bond lengths and distinct bond angles is based on the two postulates that all bonds lying on the same helix are equal in length and that all atoms are equidistant from a common axis of symmetry. The polyhedral model with distinct bond lengths and the same bond angle has the additional postulate that all the adjacent bond angles are equal. We derive exact formulae for the geometric parameters and we present asymptotic expansions for the polyhedral model with distinct bond lengths and distinct bond angles to the first two orders of magnitude. Good agreement is demonstrated for the predictions of the polyhedral model compared with the results obtained from other computational studies. [ABSTRACT FROM AUTHOR]

Abstract: We propose a new method of preparation of the cross-linked composites of poly(vinyl alcohol) (PVA) with carbon nanotubes (CNTs), in which the formation of new covalent bonds does not involve the nanotube entities, but instead PVA macromolecules only. The method consists in the addition of glutaraldehyde to PVA/CNT dispersions in order to cross-link PVA chains via an acetalization reaction. The composites prepared were studied by scanning electron microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis. The addition of 0.5 and 1% of single-walled and multi-walled CNTs (SWNTs and MWNTs, respectively) considerably changes the morphology and thermal stability characteristics of the glutaraldehyde cross-linked PVA. The use of SWNTs is believed to be more advantageous due to their better dispersion within the PVA phase as compared to MWNTs. [Copyright &y& Elsevier]

Abstract: A multi-step purification process to separate metal catalysts and their support materials from mixtures of straight and spiral multi-walled carbon nanotubes (MWNTs), synthesised via fluidised-bed chemical vapour deposition (CVD) is described. The process involves: (i) refluxing as-synthesised bed materials (iron and non-porous alumina supports coated with carbon nanotubes (CNTs) and amorphous carbon) in either HNO3, HNO3/H2SO4 (v/v=1:3) or H2SO4 at each mixture''s boiling point for 3, 6 or 12h, (ii) filtering these samples using a two-stage (2.7 and 0.5μm) filtration system, (iii) air drying and (iv) temperature selective, gas-phase oxidation in air to remove amorphous carbon. Both low and high purity as-synthesised bed materials (1.7 and 26.3wt% CNTs, respectively) were used to investigate the process efficiency. Collectively these four steps were successful in removing amorphous carbon, metal catalysts and their alumina supports from the CNTs, improving the CNT purity from 1.7wt% in the low purity as-synthesised samples to a maximum of 40.0wt% and from 26.3wt% in the higher purity feedstocks to 92.9wt%. In both cases the remaining impurity was unseparated alumina, which remained bound to the CNTs even after treatment with concentrated acids for 12h. The process has two potential advantages related to the development of large-scale CNT technologies: (i) the use of hydrofluoric acid, which is expensive and unsafe to use in large quantities has been avoided and (ii) the process is inherently scaleable and uses standard process engineering equipment suitable for large-scale CNT purification. [Copyright &y& Elsevier]

Soon after the discovery of carbon nanotubes (CNTs) in the early 1990's, the B- and/or N-doped CNTs began to attract increasing interest owing to their modified structural, physical and chemical properties. In comparison with the multi-walled nanotubes and nanofibers, substitutional doping of the single-walled nanotubes (SWNTs) has proved to be much more difficult, and it is only in very recent years that some experimental studies concerning the B- and/or N-doped SWNTs are emerging. This paper intends to provide an up-to-date overview of current research on the doped SWNTs, with scopes covering both the binary system of CBx- and CNx-SWNTs and the ternary BxCyNz-SWNTs. A survey of the latest achievements in the syntheses of doped SWNTs through either the direct syntheses methods or the post-synthetic substitution reaction route is first presented; then the aspects concerning their structural features, elemental compositions, dopants bonding configuration and atomic distributions, as well as their physical and chemical properties are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Flames offer potential for synthesis of carbon nanotubes in large quantities at considerably lower costs than that of other methods currently available. This study aims to examine conditions for carbon nanotube formation in premixed flames and to characterize the morphology of solid carbon deposits and their primary formation mechanisms in the combustion environment. Single-walled nanotubes have been observed in the post-flame region of a premixed acetylene/oxygen/15mol% argon flame operated at 6.7kPa with Fe(CO)5 vapor used as a source of metallic catalyst necessary for nanotube growth. Thermophoretic sampling and transmission electron microscopy were used to characterize the solid material present in the flame at various heights above burner (HAB), giving a resolution of formation dynamics within the flame system. Catalyst particle formation and growth is observed to dominate the immediate post-flame region (10–40mm HAB). Nanotubes were observed to be present after 40mm HAB with nanotube inception occurring as early as 30mm HAB. Between 40 and 70mm HAB, nanotubes are observed to coalesce into clusters. A nanotube formation ‘window’ is evident with formation limited to fuel equivalence ratios between 1.5 and 1.9. A continuum of morphologies ranging from relatively clean clusters of nanotubes to amorphous material is observed between these lower and upper limits. High-resolution TEM and Raman spectroscopy revealed nanotube bundles with each nanotube being single-walled with diameters between 0.9 and 1.5nm. [Copyright &y& Elsevier]

• For cadmium ion, a new method was applied to determine the concentration using non-specific DNAzyme, especially in electrochemical analysis. • Non-specific DNAzyme-based biosensor in conjunction with other biosensors and mathematical model is used to explore the interference law and improve the detection accuracy. • The biosensor array combined the Gaussian process regression can detect the Cd(II) concentration varying from 0.05 to 1000 nM, and the limit of detection is 0.034 nM. Only parts of heavy metal ions have sensitive and selective deoxyribozymes(DNAzymes), but most of heavy metal ions do not have the specific DNAzyme that limits the development of high-precise biosensors. As for cadmium ion (Cd2+), it lacks a specific DNAzyme that can be interfered by the multiple heavy metal ions (Hg2+ and Pb2+), causing poor accuracy if only non-specific DNAzyme-based biosensor measures the Cd2+ concentration. Here, one approach to solve this problem is proposed that uses in conjunction with other biosensors and the analysis data model to explore the interference law and improve the detection accuracy. The non-specific DNAzyme-based biosensor is fabricated using a field-effect transistor(FET), single-walled carbon nanotube(SWNTs) and non-specific DNAzyme. The performances are characterized by different spectral and electronic methods, indicating excellent sensitivity, stability and repeatability. Under the optimized conditions, the non-specific DNAzyme-based biosensor can determine Cd2+ down to 3.4 × 10-2 nM, and the linear range is varying from 5.0 × 10-2 to 1.0 × 103 nM with the correlation coefficient 0.98. To qualitatively and quantitatively analyze Cd2+ in a real sample, other biosensors with high sensitivity for Hg2+ and Pb2+ are selected and optimized to form a biosensor array, and then the detecting signals are processed by a mathematical model. At last, the prepared biosensor array is applied to measure the Cd2+ in feed to evaluate the detection accuracy. [ABSTRACT FROM AUTHOR]

Abstract: We present a study on the influence of pH in the control of the surface density of ferritin-based iron oxide nanoparticles. It is found that at pH 3, the adsorption coverage of ferritin on the substrate is more than 1000 particles/μm2, owing to coulombic attraction between ferritin and the substrate. Upon increasing the pH to 9 and reducing the concentration, the surface density is reduced to as low as 2 particles/μm2, owing to coulombic repulsion. The average particle size is unaffected by the pH change. [Copyright &y& Elsevier]

Abstract: A technology to address massive and batch fabrication of carbon nanotube field effect transistors (CNT-FET) based systems at wafer level is presented. In order to demonstrate the feasibility of the technology, we have designed, fabricated, tested and evaluated a CNT-FET based monitor chip. The monitor chip is composed of 16 different in design CNT-FET structures. In total, each monitor chip contains 5760 devices. Each wafer is composed of 24 monitor chips. Evaluation of the data obtained through automatic test procedures gives evidence of the fabrication of more than 10,000 functional CNT-FET on a 4 inch wafer. A yield of functional CNT-FET of 27% has been achieved for optimal designs. [Copyright &y& Elsevier]

Abstract: Stable homogeneous aqueous colloidal dispersion of single-wall carbon nanotubes (SWNTs) was prepared by using sodium salt dodecylbenzene sulfateas dispersing agent. Both strain amplitude and frequency sweep modes were employed to investigate the effect of magnetic fields on their viscoelastic properties by using a parallel-plate rheometer. The experimental results demonstrated that such materials exhibit magnetorheology, whose storage modulus and loss modulus show an increasing trend with magnetic field. The network microstructure was employed to explain the effect of magnet field on the magnetorheological properties. In addition, these results are expected to develop novel SWNT based magnetorheological fluids. [Copyright &y& Elsevier]

It is a huge challenge to find a green, simple and template-free strategy to construct metal-free graphitic carbon nitride (g-C 3 N 4) with a special morphology to improve its performance in photocatalytic hydrogen evolution (PHE). In this study, we discover a facile method to switch the g-C 3 N 4 morphology from bulk (Bg-C 3 N 4) to tubes (Tg-C 3 N 4) by melamine and cyanuric acid self-assembly to improve the PHE performance. Scanning electronic microscopy (SEM) images clearly show switching the Tg-C 3 N 4 morphology from double-walled to single-walled microtubes. In addition, the experimental results suggest that compared to the Bg-C 3 N 4 , Tg-C 3 N 4 not only has a large specific surface area but also exhibits a fast separation of charge carriers. Meanwhile, relative to Bg-C 3 N 4 , Tg-C 3 N 4 can effectively improve the absorption of light and adjust the bandgap energy of g-C 3 N 4. Excitedly, the obtained Tg–C 3 N 4 –0.2 displays the best PHE performance (967.93 μmol h−1 g−1 λ＞420 nm), which is approximately 20.95-fold greater than that of Bg-C 3 N 4. This work offers a promising idea for developing high-efficiency photocatalysts by switching the morphology. • Switching g-C 3 N 4 morphology from bulk to tuber was-prepared by a self-assembly. • Tg-C 3 N 4 morphology changes from double-walled to single-walled microtubes. • The mothed endows Tg-C 3 N 4 larger specific surface area and faster charge transfer. • Tg-C 3 N 4 with adjust the band gap energy can improve visible light response. • The obtained Tg–C 3 N 4 –0.2 exhibits the remarkable PHE activity. [ABSTRACT FROM AUTHOR]

In this study, annular microchannels with a microscale gap of 300 μm were implemented through the concentric superposition of two macro-sized cylinders. Flow area variations along the streamwise direction were created by introducing sinusoidal wave profiles on either the inner or outer wall of the annular gap while keeping the other wall flat. These variations introduced re-entrant effects along the flow direction. Numerical studies using the finite volume method were performed to elucidate the single-phase, steady-state thermal and hydrodynamic performances of the wavy channels, using water as the fluid medium, with an operating Reynolds number range of 800–2200. The predicted results were validated using the available measured data and classical correlations. This study demonstrated the viability of attaining enhanced heat transfer rates of up to 360% of the original straight channel through the inducement of flow area variations with single wavy-walled channels. Despite magnifications of the friction factors, the single wavy-walled channels attained a 120% increment in heat transfer coefficient when evaluated at the same pumping power. Overall, single-walled wavy passages were deemed suitable for heat exchanger designs demanding very high heat removal rates and efficiencies while the conventional serpentine channels were apt for moderately enhancing heat transfer while requiring low pumping power. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate the feasibility of realization of transparent gas sensors based on carbon nanotubes (CNTs). Both sensing layer and electrodes consist of CNTs deposited by spray deposition. The transparent sensor—with a transmittance higher than 60% in both sensing layer and electrodes—is characterized towards NH3 and CO2 and compared with a reference sensor with the same active layer but evaporated Au electrodes. In particular, the sensitivity towards NH3 is virtually identical for both reference and transparent sensors, whereas the transparent device exhibits higher sensitivity to CO2 than the reference electrode. The effect of the spacing among consecutive electrodes is also studied, demonstrating that a wider spacing in fully CNT based sensors results in a higher sensitivity because of the higher sensing resistance, whereas this effect was not observed in gold electrodes, as their resistance can be neglected with respect to the resistance of the CNT sensing layer. Overall, the transparent sensors show performance comparable—if not superior—to the traditionally realized ones, opening the way for seamlessly integrated sensors, which do not compromise on quality. [ABSTRACT FROM AUTHOR]

The present study addresses the influence of topological defects incorporated into sidewalls of single-walled carbon nanotubes (SWNTs) on the strength of noncovalent bonding and the state of adsorbed complex organic molecules. The interaction of free-base phthalocyanine (H 2 Pc) with Stone-Wales (SW) defect-containing armchair and zigzag nanotube models (ANT and ZNT, respectively) was studied at the PBE-D/DNP and M06-2X/6-31G(d,p) theoretical levels. The results obtained were analyzed by comparing them with those for DFT calculations on similar defect-free nanotube systems, with a particular emphasis on the data accounting for basis set superposition error (BSSE). As a whole, free-base H 2 Pc adsorbs on SW defect-containing SWNT models stronger than on the parent defect-free nanotubes. In PBE-D calculations, the increase in binding strength varies between 2.01 and 6.31 kcal/mol (0.087 and 0.274 eV), depending on SWNT chirality and defect orientation. In BSSE-corrected M06-2X calculations, this effect is less evident. C(H 2 Pc)...C(SWNT) are usually the shortest separations, followed by N(H 2 Pc)...C(SWNT) and H(H 2 Pc)...C(SWNT). Frontier orbital-related characteristics obtained exhibit insignificant differences as compared to similar systems based on defect-free ANT and ZNT models. For most systems, for both computational techniques HOMO-LUMO gap energies change by less than 0.06 eV. The pattern of HOMO-LUMO orbital distribution was found to be broadly variable. Unlabelled Image • H 2 Pc adsorbs on Stone-Wales defect-containing carbon nanotubes. • Interaction is generally stronger than with defect-free nanotubes. • C(H 2 Pc)...C(SWNT) are the closest contacts, followed by N(H 2 Pc)...C(SWNT) and H(H 2 Pc)...C(SWNT). • The pattern of HOMO-LUMO orbital distribution is variable. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotubes (SWCNTs) are carbon-based nanomaterials that possess immense industrial potential. Despite accumulating evidence that exposure to SWCNTs might be toxic to humans, our understanding of the mechanisms for cellular toxicity of SWCNTs remain limited. Here, we demonstrated that acute exposure of short (1-3μm) and regular-length (5-30μm) pristine, carboxylated or hydroxylated SWCNTs inhibited cell proliferation in human somatic and human stem cells in a cell type-dependent manner. The toxicity of regular-length pristine SWCNT was most evidenced in NP69>CYT00086>MCF-10A>MRC-5>HaCaT > HEK-293T>HepG2. In contrast, the short pristine SWCNTs were relatively less toxic in most of the cells being tested, except for NP69 which is more sensitive to short pristine SWCNTs as compared to regular-length pristine SWCNTs. Interestingly, carboxylation and hydroxylation of regular-length SWCNTs, but not the short SWCNTs, significantly reduced the cytotoxicity. Exposure of SWCNTs also induced caspase 3 and 9 activities, mitochondrial membrane depolarization, and significant apoptosis and necrosis in MRC-5 embryonic lung fibroblasts. In contrast, SWCNTs inhibited the proliferation of HaCaT human keratinocytes without inducing cell death. Further analyses by gene expression profiling and Connectivity Map analysis showed that SWCNTs induced a gene expression signature characteristic of heat shock protein 90 (HSP90) inhibition in MRC-5 cells, suggesting that SWCNTs may inhibit the HSP90 signaling pathway. Indeed, exposure of MRC-5 cells to SWCNTs results in a dose-dependent decrease in HSP90 client proteins (AKT, CDK4 and BCL2) and a concomitant increase in HSP70 expression. In addition, SWCNTs also significantly inhibited HSP90-dependent protein refolding. Finally, we showed that ectopic expression of HSP90, but not HSP40 or HSP70, completely abrogated the cytotoxic effects of SWCNTs, suggesting that SWCNT-induced cellular toxicity is HSP90 dependent. In summary, our findings suggest that the toxic effects of SWCNTs are mediated through inhibition of HSP90 in human lung fibroblasts and keratinocytes., (Copyright © 2017 Elsevier Inc. All rights reserved.)