| 1. |
- Gowtham, S., et al.
(author)
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First-principles study of physisorption of nucleic acid bases on small-diameter carbon nanotubes
- 2008
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In: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 19:12, s. 125701-
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Journal article (peer-reviewed)abstract
- We report the results of our first-principles study based on density functional theory on the interaction of the nucleic acid base molecules adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U), with a single-walled carbon nanotube (CNT). Specifically, the focus is on the physisorption of base molecules on the outer wall of a (5, 0) metallic CNT possessing one of the smallest diameters possible. Compared to the case for CNTs with large diameters, the physisorption energy is found to be reduced in the high-curvature case. The base molecules exhibit significantly different interaction strengths and the calculated binding energies follow the hierarchy G>A>T>C>U, which appears to be independent of the tube curvature. The stabilizing factor in the interaction between the base molecule and CNT is dominated by the molecular polarizability that allows a weakly attractive dispersion force to be induced between them. The present study provides an improved understanding of the role of the base sequence in deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) in their interactions with carbon nanotubes of varying diameters.
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| 2. |
- Hajati, Y, et al.
(author)
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Improved gas sensing activity in structurally defected bilayer graphene
- 2012
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In: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 23:50, s. 50550-
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Journal article (peer-reviewed)abstract
- Graphene is a two-dimensional material with a capability of gas sensing, which is here shown to be drastically improved by inducing gentle disorder in the lattice. We report that by using a focused ion beam technique, controlled disorder can be introduced into the graphene structure through Ga + ion irradiation. This disorder leads to an increase in the electrical response of graphene to NO 2 gas molecules by a factor of three in an ambient environment (air). Ab initio density functional calculations indicate that NO 2 molecules bind strongly to Stone–Wales defects, where they modify electronic states close to the Fermi level, which in turn influence the transport properties. The demonstrated gas sensor, utilizing structurally defected graphene, shows faster response, higher conductivity changes and thus higher sensitivity to NO 2 as compared to pristine graphene.
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| 3. |
- Polcar, Tomas, et al.
(author)
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Nanoscale colour control : W-O graded coatings deposited by magnetron sputtering
- 2008
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In: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 19:39, s. 395202-
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Journal article (peer-reviewed)abstract
- A new design of decorative tungsten oxide coatings is presented. The coatings were deposited with a graded refractive index by magnetron sputtering from a tungsten target and pulsing the reactive gas. The controlled injection of the reactive gas can produce a concentration profile gradient from pure tungsten to tungsten trioxide, determining the final apparent colour of the coating. A dynamic sputtering model was built to simulate the growth of the coating during the reactive gas pulsing which was validated by direct measurement of the gradient of the oxygen content in the deposited coatings. Finally, these results were used for an optical model allowing the optical properties of the deposited tungsten oxide layer to be described, again validated by experimental analysis. This procedure allows the deposition of coatings with the desired colour by using the models to finding the optimal oxygen pulse parameters. This proposed method can be easily applied to almost any metal/metal oxide system.
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| 4. |
- Banin, U., et al.
(author)
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Nanotechnology for catalysis and solar energy conversion
- 2021
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In: Nanotechnology. - : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 32:4
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Journal article (peer-reviewed)abstract
- This roadmap on Nanotechnology for Catalysis and Solar Energy Conversion focuses on the application of nanotechnology in addressing the current challenges of energy conversion: 'high efficiency, stability, safety, and the potential for low-cost/scalable manufacturing' to quote from the contributed article by Nathan Lewis. This roadmap focuses on solar-to-fuel conversion, solar water splitting, solar photovoltaics and bio-catalysis. It includes dye-sensitized solar cells (DSSCs), perovskite solar cells, and organic photovoltaics. Smart engineering of colloidal quantum materials and nanostructured electrodes will improve solar-to-fuel conversion efficiency, as described in the articles by Waiskopf and Banin and Meyer. Semiconductor nanoparticles will also improve solar energy conversion efficiency, as discussed by Boschloo et al in their article on DSSCs. Perovskite solar cells have advanced rapidly in recent years, including new ideas on 2D and 3D hybrid halide perovskites, as described by Spanopoulos et al 'Next generation' solar cells using multiple exciton generation (MEG) from hot carriers, described in the article by Nozik and Beard, could lead to remarkable improvement in photovoltaic efficiency by using quantization effects in semiconductor nanostructures (quantum dots, wires or wells). These challenges will not be met without simultaneous improvement in nanoscale characterization methods. Terahertz spectroscopy, discussed in the article by Milot et al is one example of a method that is overcoming the difficulties associated with nanoscale materials characterization by avoiding electrical contacts to nanoparticles, allowing characterization during device operation, and enabling characterization of a single nanoparticle. Besides experimental advances, computational science is also meeting the challenges of nanomaterials synthesis. The article by Kohlstedt and Schatz discusses the computational frameworks being used to predict structure-property relationships in materials and devices, including machine learning methods, with an emphasis on organic photovoltaics. The contribution by Megarity and Armstrong presents the 'electrochemical leaf' for improvements in electrochemistry and beyond. In addition, biohybrid approaches can take advantage of efficient and specific enzyme catalysts. These articles present the nanoscience and technology at the forefront of renewable energy development that will have significant benefits to society.
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| 5. |
- Chulapakorn, Thawatchart, 1988-, et al.
(author)
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Influence of Swift Heavy Ion Irradiation on the Photoluminescence of Si-nanoparticles and Defects in SiO2
- 2017
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In: Nanotechnology. - : IOP PUBLISHING LTD. - 0957-4484 .- 1361-6528. ; 28:37
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Journal article (peer-reviewed)abstract
- The influence of swift heavy ion (SHI) irradiation on the photoluminescence (PL) of silicon nanoparticles (SiNPs) and defects in SiO2-film is investigated. SiNPs were formed by implantation of 70 keV Si+ and subsequent thermal annealing to produce optically active SiNPs and to remove implantation-induced defects. Seven different ion species with energy between 3-36 MeV and fluence from 10(11)-10(14) cm(-2) were employed for irradiation of the implanted samples prior to the thermal annealing. Induced changes in defect and SiNP PL were characterized and correlated with the specific energy loss of the employed SHIs. We find that SHI irradiation, performed before the thermal annealing process, affects both defect and SiNP PL. The change of defect and SiNP PL due to SHI irradiation is found to show a threshold-like behaviour with respect to the electronic stopping power, where a decrease in defect PL and an anticorrelated increase in SiNP PL after the subsequent thermal annealing are observed for electronic stopping exceeding 3-5 keV nm(-1). PL intensities are also compared as a function of total energy deposition and nuclear energy loss. The observed effects can be explained by ion track formation as well as a different type of annealing mechanisms active for SHI irradiation compared to the thermal annealing.
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| 6. |
- Duan, Tianbo, 1992-, et al.
(author)
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Towards Ballistic Transport CVD Graphene by Controlled Removal of Polymer Residues
- 2022
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In: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 33:49, s. 495704-
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Journal article (peer-reviewed)abstract
- Polymer-assisted wet transfer of chemical vapor deposited (CVD) graphene has achieved great success towards the true potential for large-scale electronic applications, while the lack of an efficient polymer removal method has been regarded as a crucial factor for realizing high carrier mobility in graphene devices. Hereby, we report an efficient and facile method to clean polymer residues on graphene surface by merely employing solvent mixture of isopropanol (IPA) and water (H2O). Raman spectroscopy shows an intact crystal structure of graphene after treatment, and the x-ray photoelectron spectroscopy indicates a significant decrease in the C–O and C=O bond signals, which is mainly attributed to the removal of polymer residues and further confirmed by subsequent atomic force microscopy analysis. More importantly, our gated measurements demonstrate that the proposed approach has resulted in a 3-fold increase of the carrier mobility in CVD graphene with the electron mobility close to 10 000 cm2 V−1 S−1, corresponding to an electron mean free path beyond 100 nm. This intrigues the promising application for this novel method in achieving ballistic transport for CVD graphene devices.
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| 7. |
- Geremariam Welearegay, Tesfalem, et al.
(author)
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Fabrication and characterisation of ligand-functionalised ultrapure monodispersed metal nanoparticle nanoassemblies employing advanced gas deposition technique
- 2018
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In: Nanotechnology. - : IOP PUBLISHING LTD. - 0957-4484 .- 1361-6528. ; 29:6
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Journal article (peer-reviewed)abstract
- Here, we report for the first time the fabrication of ligand-functionalised ultrapure monodispersed metal nanoparticles (Au, Cu, and Pt) from their pure metal precursors using the advanced gas deposition technique. The experimental conditions during nanoparticle formation were adjusted in order to obtain ultrafine isolated nanoparticles on different substrates. The morphology and surface analysis of the as-deposited metal nanoparticles were investigated using scanning electron microscopy, x-ray diffraction and Fourier transform infra-red spectroscopy, which demonstrated the formation of highly ordered pure crystalline nanoparticles with a relatively uniform size distribution of similar to 10 nm (Au), similar to 4 nm (Cu) and similar to 3 nm (Pt), respectively. A broad range of organic ligands containing thiol or amine functional groups were attached to the nanoparticles to form continuous networks of nanoparticle-ligand nanoassemblies, which were characterised by scanning electron microscopy and x-ray photoelectron spectroscopy. The electrical resistance of the functional nanoassemblies deposited in the gap spacing of two microfabricated parallel Au electrodes patterned on silicon substrates ranged between tens of k Omega and tens of M Omega, which is suitable for use in many applications including (bio)chemical sensors, surface-enhanced Raman spectroscopy and molecular electronic rectifiers.
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| 8. |
- Hussain, T., et al.
(author)
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Graphitic carbon nitride nano sheets functionalized with selected transition metal dopants : an efficient way to store CO2
- 2018
-
In: Nanotechnology. - : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 29:41
-
Journal article (peer-reviewed)abstract
- Proficient capture of carbon dioxide (CO2) is considered to be a backbone for environment protection through countering the climate change caused by mounting carbon content. Here we present a comprehensive mechanism to design novel functional nanostructures capable of capturing a large amount of CO2 efficiently. By means of van der Waals corrected density functional theory calculations, we have studied the structural, electronic and CO2 storage properties of carbon nitride (g-C6N8) nano sheets functionalized with a range of transition metal (TM) dopants ranging from Sc to Zn. The considered TMs bind strongly to the nano sheets with binding energies exceeding their respective cohesive energies, thus abolishing the possibility of metal cluster formation. Uniformly dispersed TMs change the electronic properties of semiconducting g-C6N8 through the transfer of valence charges from the former to the latter. This leaves all the TM dopants with significant positive charges, which are beneficial for CO2 adsorption. We have found that each TM's dopants anchor a maximum of four CO2 molecules with suitable adsorption energies (-0.15 to -1.0 eV) for ambient condition applications. Thus g-C6N8 nano sheets functionalized with selected TMs could serve as an ideal sorbent for CO2 capture.
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| 9. |
- Hussain, Tanveer, et al.
(author)
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Improved sensing characteristics of methane over ZnO nano sheets upon implanting defects and foreign atoms substitution
- 2017
-
In: Nanotechnology. - : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 28:41
-
Journal article (peer-reviewed)abstract
- Thanks to the growing interests of metal oxide sensors in environmental and industrial uses, this study presents the sensing mechanism of methane gas (CH4) on recently synthesized two-dimensional form of ZnO, ZnO nano sheets (ZnO-NS). The adsorption energy of CH4 on pristine ZnO-NS, calculated by means of van derWaals corrected first-principles calculations, is found to be insufficient restricting its application as an efficient nano sensor. However, the creation of (O/Zn) vacancies and the substitution of foreign dopants into ZnO-NS considerably intensify the binding energy of CH4. Through a comprehensive energetic analysis, it is observed that among all the substituents, boron (B), sulphur (S) and gallium (Ga) improves the binding of CH4 to 2.75, 6.1 and 7.5 times respectively than its values on pristine ZnO-NS. In addition to the CH4 binding energies falling ideally between physisorption and chemisorption range, a prominent variation in the electronic properties before and after CH4 exposure indicates the promise of substituted Zn-NS as a useful nano sensors.
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| 10. |
- Jafri, Syed Hassan Mujtaba, 1979-, et al.
(author)
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Nanomolecular electronic devices based on AuNP molecule nanoelectrodes using molecular place-exchange process
- 2020
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In: Nanotechnology. - : IOP PUBLISHING LTD. - 0957-4484 .- 1361-6528. ; 31:22
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Journal article (peer-reviewed)abstract
- The implementation of electronics applications based on molecular electronics devices is hampered by the difficulty of placing a single or a few molecules with application-specific electronic properties in between metallic nanocontacts. Here, we present a novel method to fabricate 20 nm sized nanomolecular electronic devices (nanoMoED) using a molecular place-exchange process of nonconductive short alkyl thiolates with various short chain conductive oligomers. After the successful place-exchange with short-chain conjugated oligomers in the nanoMoED devices, a change in device resistance of up to four orders of magnitude for 4,4 '-biphenyldithiol (BPDT), and up to three orders of magnitude for oligo phenylene-ethynylene (OPE), were observed. The place-exchange process in nanoMoEDs are verified by measuring changes in device resistance during repetitive place-exchange processes between conductive and nonconductive molecules and surface-enhanced Raman spectroscopy. This opens vast possibilities for the fabrication and application of nanoMoED devices with a large variety of molecules.
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