Slippery Alkoxysilane Coatings for Antifouling Applications.

Herein, we report the wettability and antifouling behavior of a range of different siloxane coatings on plastic and glass substrates. The films investigated are prepared using trimethoxysilane precursors with different alkyl chain lengths (1-18 C atoms) in order to study how the nature of the hydrophobic group affects the different parameters used to characterize wettability (contact angles, sliding angles, and contact angle hysteresis). Atomic force microscopy analysis shows that the coatings possess low surface topography [root mean squared roughness (rms) < 50 nm] and are highly transparent as studied using UV-vis spectroscopy. The sliding properties of H2O, CH2I2, methanol, and ethylene glycol were observed to be strongly influenced by the chain length of the alkoxysilane precursor used. The coatings formed from the longer chain analogues show comparable water sliding angles to superhydrophobic surfaces. These coatings show similar performance to analogous alkoxysilane coating-bearing fluorinated groups, indicating that they could act as viable environmentally friendly alternatives to some of the fluorinated films that have been widely adopted. Furthermore, these surfaces are highly durable toward common forms of abrasion and are observed to show low adhesion toward synthetic feces, indicating that their utility extends further than repelling liquids alone. Consequently, these coatings could show promise for potential use in applications in the medical sector where fouling by biological mixtures leads to an unsustainable use of materials.

Interaction of Surface-Modified Alumina Nanoparticles and Surfactants at an Oil/Water Interface: A Neutron Reflectometry, Scattering, and Enhanced Oil Recovery Study.

The evaluation of the mechanism of nanoparticle (NP)/surfactant complex adsorption at the critical oil/water interface was studied. A sophisticated technique (neutron reflectometry) was used to give a unique insight on NP/oil interactions in oil recovery systems. Herein, the adsorption of two modified alumina NPs with different degrees of hydrophobicity [hydrophilic = 2-[2-(2-methoxyethoxy)ethoxy]acetic acid and hydrophobic = octanoic acid (OCT)] stabilized with two different surfactants were studied at the oil/water interface. A thin layer of deuterated (D) and hydrogenated (H) hexadecane (contrast matching silicon substrate) oil was formed on a silicon block by a spin coating freeze process. The distribution of the NPs across the oil/water interface with the CTAB surfactant is similar between the two systems. NPs coated with CTAB have more affinity toward the oil/water interface, which explains the oil recovery increase by around 5% when flooding the core with the OCT-NP/CTAB system compared to the surfactant flooding alone. These results suggest that the NP/surfactant complexes can have potential usage in EOR recovery applications.

Facemasks and ferrous metallurgy: improving gasification reactivity of low-volatile coals using waste COVID-19 facemasks for ironmaking application.

The global pandemic response to COVID-19 has led to the generation of huge volumes of unrecyclable plastic waste from single use disposable face coverings. Rotary hearth furnaces can be used to recover Zn and Fe from non-recyclable steelmaking by-product dusts, and waste plastic material such as facemasks could be utilized as a supplementary reductant for the rotary hearth furnace (RHF), but their fibrous form makes milling and processing to appropriate sizing for RHF application extremely challenging. A scalable method of grinding facemasks to powder by melting and mixing with Welsh coal dust reported herein provides a solution to both environmental challenges. The melt-blended PPE/coal dust shows a dramatically improved CO2 gasification reactivity (Ea = 133-159 kJmol-1) when compared to the untreated coal (Ea = 183-246 kJmol-1), because of improved pore development in the coal during the pyrolysis stage of heating and the catalytic activity of the CaO based ash present in the facemask plastic. The results are promising for the application of waste facemasks in recycling steelmaking by-product dusts in rotary hearth furnaces and may also be suitable for direct injection to the blast furnace subject to further study.

Rheological, physicochemical, and microstructural properties of asphalt binder modified by fumed silica nanoparticles.

Warm mix asphalt (WMA) is gaining increased attention in the asphalt paving industry as an eco-friendly and sustainable technology. WMA technologies are favorable in producing asphalt mixtures at temperatures 20-60 °C lower in comparison to conventional hot mix asphalt. This saves non-renewable fossil fuels, reduces energy consumption, and minimizes vapors and greenhouse gas emissions in the production, placement and conservation processes of asphalt mixtures. At the same time, this temperature reduction must not reduce the performance of asphalt pavements in-field. Low aging resistance, high moisture susceptibility, and low durability are generally seen as substantial drawbacks of WMA, which can lead to inferior pavement performance, and increased maintenance costs. This is partly due to the fact that low production temperature may increase the amount of water molecules trapped in the asphalt mixture. As a potential remedy, here we use fumed silica nanoparticles (FSN) have shown excellent potential in enhancing moisture and aging susceptibility of asphalt binders. In this study, asphalt binder modification by means of FSN was investigated, considering the effects of short-term and long-term aging on the rheological, thermal, and microstructural binder properties. This research paves the way for optimizing WMA by nanoparticles to present enhanced green asphalt technology.

Effect of Applied Pressure on the Electrical Resistance of Carbon Nanotube Fibers.

Carbon nanotubes (CNTs) can be spun into fibers as potential lightweight replacements for copper in electrical current transmission since lightweight CNT fibers weigh <1/6th that of an equivalently dimensioned copper wire. Experimentally, it has been shown that the electrical resistance of CNT fibers increases with longitudinal strain; however, although fibers may be under radial strain when they are compressed during crimping at contacts for use in electrical current transport, there has been no study of this relationship. Herein, we apply radial stress at the contact to a CNT fiber on both the nano- and macro-scale and measure the changes in fiber and contact resistance. We observed an increase in resistance with increasing pressure on the nanoscale as well as initially on the macro scale, which we attribute to the decreasing of axial CNT…CNT contacts. On the macro scale, the resistance then decreases with increased pressure, which we attribute to improved radial contact due to the closing of voids within the fiber bundle. X-ray photoelectron spectroscopy (XPS) and UV photoelectron spectroscopy (UPS) show that applied pressure on the fiber can damage the π-π bonding, which could also contribute to the increased resistance. As such, care must be taken when applying radial strain on CNT fibers in applications, including crimping for electrical contacts, lest they operate in an unfavorable regime with worse electrical performance.

Groundwater Remediation of Volatile Organic Compounds Using Nanofiltration and Reverse Osmosis Membranes-A Field Study.

Groundwater contamination by chlorinated hydrocarbons represents a particularly difficult separation to achieve and very little is published on the subject. In this paper, we explore the potential for the removal of chlorinated volatile and non-volatile organics from a site in Bedfordshire UK. The compounds of interest include trichloroethylene (TCE), tetrachloroethylene (PCE), cis-1,2-dichloroethylene (DCE), 2,2-dichloropropane (DCP) and vinyl chloride (VC). The separations were first tested in the laboratory. Microfiltration membranes were of no use in this separation. Nanofiltration membranes performed well and rejections of 70-93% were observed for synthetic solutions and up to 100% for real groundwater samples. Site trials were limited by space and power availability, which resulted in a maximum operating pressure of only 3 bar. Under these conditions, the nanofiltration membrane removed organic materials, but failed to remove VOCs to any significant extent. Initial results with a reverse osmosis membrane were positive, with 93% removal of the VOCs. However, subsequent samples taken demonstrated little removal. Several hypotheses were presented to explain this behavior and the most likely cause of the issue was fouling leading to adsorption of the VOCs onto the membrane and allowing passage through the membrane matrix.

Pressure dependent conduction of individual multi-walled carbon nanotubes: the effect of mechanical distortions.

Multi-walled carbon nanotubes (MWCNTs) show an oscillation in electrical resistance (from I-V measurements) during mechanical distortion in which peak separation is inversely correlated with the diameter of the MWCNTs. These results provide the first experimental support of the theoretical prediction that distortion causes Van Hove singularities and Dirac cones in MWCNTs to misalign and cause the opening of the band gap, and suggest that when fabricating contacts for CNTs for device applications, the pressure caused by the contact deposition method must be taken into account for manufacturing devices with consistent properties.

Inducing upwards band bending by surface stripping ZnO nanowires with argon bombardment.

Metal oxide semiconductors such as ZnO have attracted much scientific attention due their material and electrical properties and their ability to form nanostructures that can be used in numerous devices. However, ZnO is naturally n-type and tailoring its electrical properties towards intrinsic or p-type in order to optimise device operation have proved difficult. Here, we present an x-ray photon-electron spectroscopy and photoluminescence study of ZnO nanowires that have been treated with different argon bombardment treatments including with monoatomic beams and cluster beams of 500 atoms and 2000 atoms with acceleration volte of 0.5 keV-20 keV. We observed that argon bombardment can remove surface contamination which will improve contact resistance and consistency. We also observed that using higher intensity argon bombardment stripped the surface for nanowires causing a reduction in defects and surface OH- groups both of which are possible causes of the n-type nature and observed a shift in the valance band edge suggest a shift to a more p-type nature. These results indicate a simple method for tailoring the electrical characteristic of ZnO.

Polyphenols of Traditional Apple Varieties in Interaction with Barley ß-Glucan: A Study of the Adsorption Process.

Apple polyphenols have been studied for various beneficial bioactivities. Especially interesting are traditional, old varieties of apples for which some initial studies have suggested significant bioactivities, but they are still not completely understood. Polyphenol bioactivities can be affected by interactions with dietary fibers such as ß-glucans. The aim of this study was to investigate for the first time interactions between individual polyphenols from traditional, old apple varieties ("Bozicnica" and "Batulenka") and ß-glucans by studying the adsorption process. Polyphenols were extracted from the peel and flesh of traditional apples by using an ultrasonic bath and characterized with high-performance liquid chromatography. The amounts of adsorbed (qe) and un-adsorbed (ce) polyphenols were modeled with adsorption isotherms (Langmuir, Dubinin-Radushkevich, and Hill) by using improved non-linear fitting in a novel R algorithm, developed specifically for the modeling of adsorption isotherms. Polyphenols adsorbed onto ß-glucan from 9 to 203 (peel, "Bozicnica"), 1 to 484 (peel, "Batulenka"), 5 to 160 (flesh, "Bozicnica"), and 19 to 28 mg g-1 (flesh, "Batulenka"). The adsorption was concentration dependent (polyphenols present in higher amount adsorbed in higher amounts). Physical sorption can be suggested. Polyphenols from traditional apples adsorb onto ß-glucan and should be further studied.

New insights into the interactions between asphaltene and a low surface energy anionic surfactant under low and high brine salinity.

HYPOTHESIS: The hyperbranched chains on the tail of low surface energy surfactants (LSES) causes lowering of surface free energy and rock wettability alteration, offering significant improvement in oil recovery in asphaltene oil reservoirs. EXPERIMENTS: Oil sweep efficiency was determined by fluid displacement in pure brine and LSES-brine solutions in a microfluidic pattern that was representative of a sandstone cross-section. Interfacial tension (IFT), wettability alteration, Raman and X-ray photoelectron spectroscopy (XPS) were used to measure the changes of asphaltene interactions with oil-aged substrate after surface treating with brine and surfactant-brine solutions. FINDINGS: The hyperbranched LSES yielded a significant increase in the original-oil-in-place (OOIP) recovery (58%) relative to brine flooding (25%), even in the presence of asphaltene. Raman spectra showed the LSES-brine solutions to be capable of causing change to the asphaltene aggregate size after centrifugation treatment.

Controlling the wettability of plastic by thermally embedding coated aluminium oxide nanoparticles into the surface.

HYPOTHESIS: Nanoparticle embedding into the surface of plastics provides an effective anchor that improves the durability of coatings formed from functionalized nanoparticles. Coatings formed from thermally embedded particles show superior wear resistance relative to coatings formed from non-embedded particles. As a consequence of this, embedded nanoparticles functionalized with hydrophilic and hydrophobic carboxylates are better suited for controlling the wettability of plastics than when the nanoparticles are deposited onto the plastic under ambient conditions. EXPERIMENTS: Carboxylate-functionalized Al2O3 nanoparticles were embedded into ethylene vinyl acetate through spray coating the particles onto the substrate during heating. Sonication was used to remove excess particles that did not become embedded into the material. Coatings formed from the embedded particles were characterized through scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The wettability of the coatings was characterized using static and dynamic contact angle (CA) measurements to measure the apparent water contact angles, and sliding angle measurements, whilst the durability of the coatings was studied using scratch testing, tape peel tests, and abrasion tests. The build-up of fog on the substrates was also studied through exposing the surfaces to water vapour. FINDINGS: Thermal embedding of the particles into the surface of the plastic was observed to occur when the material was heated to temperatures around its melting temperature. AFM and SEM showed that plastic embedded with the nanoparticles possessed a morphology that was substantially rougher than the untreated plastic. CA measurements showed that plastic embedded with hydrophobic isostearate functionalized nanoparticles was highly hydrophobic and displayed a CA of approximately 152°. Dynamic CA measurements and sliding angle measurements revealed that plastic embedded with the isostearate functionalized nanoparticles showed petal-like wetting behavior. Furthermore, it was observed that the CA of the plastic could be varied from highly hydrophobic to highly hydrophilic through embedding varying amounts of isostearate and hydrophilic 2-[2-(2-methoxyethoxy)ethoxy]acetate functionalized Al2O3 nanoparticles into the surface of the material. Scratch testing showed that thermally embedding the nanoparticles into the plastic substantially improved their abrasion resistance, relative to when the nanoparticles are deposited onto the non-heated material. This methodology indicates that embedding nanoparticles into plastics creates durable coatings that can display variable wettability. Consequently, this methodology could be useful in applications where it is desirable to keep plastics dry, such as for food packaging or medical devices.

Temperature-Induced Structural Transformations in Undoped and Eu3+-Doped Ruddlesden-Popper Phases Sr2SnO4 and Sr3Sn2O7: Relation to the Impedance and Luminescence Behaviors.

We report that luminescence of Eu3+ ion incorporated into Ruddlesden-Popper phases allows monitoring phase transition in powders (instead of single crystals), in a time-efficient manner (compared to neutron diffraction), and importantly, with greater sensitivity than previous methods. Crystal structure and dielectric response of undoped and 0.5%Eu3+-doped Sr3Sn2O7 ceramics were studied as a function of temperature over the temperature range of 300-800 K. The luminescence studies of 0.5%Eu3+-doped Sr2SnO4 and Sr3Sn2O7 samples were performed in the temperature range of 80-500 K. These results were compared with the respective dependences for the undoped compounds. The structural transformations in 0.5%Eu3+-doped Sr3Sn2O7 were found at 390 and 740 K. The former is associated with the isostructural atomic rearrangement that resulted in a negative thermal expansion along two of three orthorhombic crystallographic axes, while the latter corresponds to the structural transition from the orthorhombic Amam phase to the tetragonal I4/mmm one. A similar temperature behavior with the structural transformations in the same temperature ranges was observed in undoped Sr3Sn2O7, although the values of lattice parameters of the Eu3+-doped and undoped compounds were found to be slightly different indicating an incorporation of europium in the crystal lattice. A dielectric anomaly associated with a structural phase transition was observed in Sr3Sn2O7 at 390 K. Optical measurements performed over a wide temperature range demonstrated a clear correlation between structural transformations in Eu3+-doped Sr2SnO4 and Sr3Sn2O7 and the temperature anomalies of their luminescence spectra, suggesting the efficacy of this method for the determination of subtle phase transformations.

Comparison of hydrophobicity and durability of functionalized aluminium oxide nanoparticle coatings with magnetite nanoparticles-links between morphology and wettability.

HYPOTHESIS: The wetting characteristics of coatings created using functionalised nanoparticles and adhesive resins, depends strongly on the particle distribution within the surface layers. Although it has been shown that commercially available adhesives improve the durability of hydrophobic nanoparticle coatings, the wettability of these surfaces is governed by the agglomeration behaviour of the particles within the adhesive. As a consequence of this, coatings where the particles are highly agglomerated within the adhesive show lower hydrophobicity. EXPERIMENTS: The morphology and chemical composition of coatings formed from carboxylate functionalised Al2O3 and magnetite (Fe3O4) nanoparticles and epoxy resin on plastic was studied using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Water contact angle (WCA) measurements were used to investigate how the coatings' morphological characteristics and loading of the particles within the surface layers influenced their wettability. Infrared (IR) spectroscopy and thermogravimetric analysis (TGA) were used to study carboxylate adsorption onto the magnetite nanoparticles. FINDINGS: Combining the Al2O3 nanoparticles with epoxy resin was observed to create highly hydrophobic coatings that displayed water contact angles (WCAs) between 145 and 150°. These coatings displayed good durability when sonicated in isopropanol and wiped with tissue. By comparison, coatings formed from the magnetite nanoparticles were substantially less hydrophobic and displayed WCAs between 75 and 125° when combined with epoxy resin. SEM revealed that the magnetite nanoparticles in the coatings were present as large agglomerates. By comparison, coatings formed from the Al2O3 nanoparticles showed a more homogenous particle distribution. Furthermore, XPS showed that the resin engulfed the magnetite nanoparticles to a far greater extent. The difference in wetting behaviour of these coatings is largely attributed to their different morphologies, since the particles are similar sizes and TGA shows that the particles possess similar carboxylate grafting densities. The uneven distribution of nanoparticles in the magnetite/epoxy resin coating is due to the particles' magnetic properties, which drive nanoparticle agglomeration as the coatings solidify. This work demonstrates that it is important to consider inter-particle interactions when fabricating low wettability composite coatings.

Experimental Measurement of Angular and Overlap Dependence of Conduction between Carbon Nanotubes of Identical Chirality and Diameter.

Measurement of the angular and overlap dependence of the conduction between two identical carbon nanotubes (CNTs), with the same diameter and chirality, has only been possible through theoretical calculations; however, our observation of increased resistance adjacent to the junction between two CNTs facilitates such measurements. Since electrical resistance was found to increase with increased diameter ratio, applying 10 V to one of dissimilar diameter CNTs results in cleavage at the junction. Manipulation of the resulting identical CNTs (created by cutting a single CNT) allows for the direct measurement of the angular and parallel overlap conduction. Angular (13° < θ < 63°) dependence shows two minima (22° and 44°) and a maximum at 30°, and conduction between parallel CNTs increases with overall tip separation but shows a sinusoidal relationship with contact length, consistent with the concept of atomic scale registry.

Size and morphology dependent surface wetting based on hydrocarbon functionalized nanoparticles.

HYPOTHESIS: The wetting properties of films created using metal oxide nanoparticles can be controlled through roughness and chemical functionality; however, other variations such as the size and shape of the particles play an important role in improved understanding of the wetting behaviour of these materials. EXPERIMENTS: Infrared (IR) spectroscopy and thermogravimetric analysis (TGA) were used to study the chemisorption and grafting density of a carboxylic acid onto the surface of nanoparticles. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to investigate the morphology and roughness of the nanoparticle films. To investigate the wettability and surface energy of the films, static and dynamic contact angle (CA) measurements were used. FINDINGS: Smaller, spherical nanoparticles (<50 nm) were observed to create films that displayed greater surface roughness and showed superhydrophobic properties. By comparison, larger, 135 nm spherical nanoparticles showed reduced surface roughness and displayed water contact angles (WCAs) <150°. Since these particles showed similar carboxylate grafting densities, this suggests that there is a particle size limit above which it is not possible to deposit superhydrophobic films. This study also shows that topographical effects brought about by film roughness can be overcome through increasing the carboxylate grafting density on the surface of the nanoparticles. It was observed that films created using mix shape <50 nm nanoparticles with relatively low surface roughness displayed superhydrophobic WCAs and low hysteresis. These particles also possessed a substantially larger carboxylate grafting density, indicating that the extent of functionalization also has a large bearing on the wettability of the films. Herein, we show that particle size, morphology, and reactivity all play important roles in determining the wettability of nanoparticle films.

A new approach to enhancing the CO2 capture performance of defective UiO-66 via post-synthetic defect exchange.

Zirconium-based metal-organic frameworks (Zr-MOFs) are a subclass of MOFs known for their remarkable stability, especially in the presence of water. This makes them extremely attractive for practical applications, including CO2 capture from industrial emission sources; however, the CO2 adsorption capacity of Zr-MOFs is moderate compared to that of the best performing MOFs reported to date. Functionalization of Zr-MOFs with amino groups has been demonstrated to increase their affinity for CO2. In this work, we assessed the potential of post-synthetic defect exchange (PSDE) as an alternative approach to introduce amino functionalities at missing-cluster defective sites in formic acid modulated UiO-66. Both pyridine-containing (picolinic acid and nicotinic acid) and aniline-containing (3-aminobenzoic acid and anthranilic acid) monocarboxylates were integrated within defective UiO-66 with this method. Non-defective UiO-66 modified with linkers bearing the same amino groups (2,5-pyridinedicarboxylic acid and 2-aminoterephthalic acid) were prepared by classical post-synthetic ligand exchange (PSE), in order to compare the effect of introducing functionalities at defective sites versus installing them on the backbone. PSDE reduces the porosity of defective UiO-66, but improves both the CO2 uptake and the CO2/N2 selectivity, whereas PSE has no effect on the porosity of non-defective UiO-66, improving the CO2 uptake but leaving selectivity unchanged. Modification of defective UiO-66 with benzoic acid reveals that pore size reduction is the main factor responsible for the observed uptake improvement, whereas the presence of nitrogen atoms in the pores seems to be beneficial for increasing selectivity.

Aqueous electromigration of single-walled carbon nanotubes and co-electromigration with copper ions.

The electromigration behaviour of raw and acid purified single walled carbon nanotubes (SWCNTs) in dilute aqueous systems (0.0034 mg mL-1), in the absence of surfactant, with the addition of either 0.85 M acetic acid or 0.1 M CuSO4, was evaluated using a 2-inch copper cathode and either a 2-inch copper or 0.5-inch platinum anode. The results showed that the electromigration of raw SWCNTs (with a high catalyst residue) in the presence of CuSO4 resulted in the formation of a Cu-SWCNT composite material at the cathode. In contrast, acid purified SWCNTs were observed to diffuse to a copper anode, creating fibrillated agglomerates with "rice-grain"-like morphologies. Upon acidification with acetic acid (or addition of CuSO4) the direction of electromigration reversed towards the cathode as a result of coordination of Cu2+ to the functional groups on the SWCNT overcoming the inherent negative charge of the acid purified SWCNTs. The result was the co-deposition of SWCNTs and Cu metal on the cathode. Addition of 0.005 M EDTA sequesters some of the Cu2+ and resulted in the separation of metal decorated SWCNTs to the cathode and un-decorated SWCNTs to the anode. The resulting SWCNT and Cu/SWCNT deposits were characterized by Raman spectroscopy, XPS, SEM, EDS, and TEM.

Post-Synthetic Ligand Exchange in Zirconium-Based Metal-Organic Frameworks: Beware of The Defects!

Post-synthetic ligand exchange in the prototypical zirconium-based metal-organic framework (MOF) UiO-66 was investigated by in situ solution 1 H NMR spectroscopy. Samples of UiO-66 having different degrees of defectivity were exchanged using solutions of several terephthalic acid analogues in a range of conditions. Linker exchange only occurred in defect-free UiO-66, whereas monocarboxylates grafted at defect sites were found to be preferentially exchanged with respect to terephthalic acid over the whole range of conditions investigated. A 1:1 exchange ratio between the terephthalic acid analogue and modulator was observed, providing evidence that the defects had missing-cluster nature. Ex situ characterisation of the MOF powders after exchange corroborated these findings and showed that the physical-chemical properties of the MOF depend on whether the functionalisation occurs at defective sites or on the framework.

Investigation into the effects of surface stripping ZnO nanosheets.

ZnO nanosheets are polycrystalline nanostructures that are used in devices including solar cells and gas sensors. However, for efficient and reproducible device operation and contact behaviour the conductivity characteristics must be controlled and surface contaminants removed. Here we use low doses of argon bombardment to remove surface contamination and make reproducible lower resistance contacts. Higher doses strip the surface of the nanosheets altering the contact type from near-ohmic to rectifying by removing the donor-type defects, which photoluminescence shows to be concentrated in the near-surface. Controlled doses of argon treatments allow nanosheets to be customised for device formation.

Spatial and Contamination-Dependent Electrical Properties of Carbon Nanotubes.

Two-point probe and Raman spectroscopy have been used to investigate the effects of vacuum annealing and argon bombardment on the conduction characteristics of multiwalled carbon nanotubes (MWCNTs). Surface contamination has a large effect on the two-point probe conductivity measurements which results in inconsistent and nonreproducible contacts. The electric field under the contacts is enhanced which results in overlapping depletion regions when probe separations are small (<4 µm) causing very high resistances. Annealing at 200 and 500 °C reduced the surface contamination on the MWCNT, but high resistance contacts still did not allow intrinsic conductivity measurements of the MWCNT. The high resistance measured due to the overlapping depletion regions was not observed after annealing to 500 °C. Argon bombardment reduced the surface contamination more than vacuum annealing at 500 °C but caused a slight increase in the defects concentration, enabling the resistivity of the MWCNT to be calculated, which is found to be dependent on the CNT diameter. The observations have significant implications for future CNT-based devices.