| 1. |
- Abay, Simon, 1980, et al.
(författare)
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Quantized Conductance and Its Correlation to the Supercurrent in a Nanowire Connected to Superconductors
- 2013
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 13:8, s. 3614-3617
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Tidskriftsartikel (refereegranskat)abstract
- We report conductance and supercurrent of InAs nano wires coupled to Al-superconducting electrodes with short channel lengths and good Ohmic contacts. The nanowires are suspended 15 nm above a local gate electrode. The charge density in the nanowires can be controlled by a small change in the gate voltage. For large negative gate voltages, the number of conducting channels is reduced gradually, and we observe a stepwise decrease of both conductance and critical current before the conductance vanishes completely.
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| 2. |
- Apaydin, Dogukan, 1991, et al.
(författare)
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Optically Pumped UVC Photonic Crystal Surface-Emitting Laser
- 2023
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Photonic crystal surface-emitting lasers (PCSELs) are a new type of semiconductor lasers that offer a high optical output power while maintaining single-mode operation and a low divergence angle. Such devices rely upon the in-plane optical feedback from a two-dimensional photonic crystal and feature out-of-plane emission of the modes with zero group velocity at the photonic band edges by diffraction. Since the demonstration of the first PCSEL [1], the concept has been implemented in standard semiconductor materials with the demonstration of highperforming infrared and blue-emitting lasers [2, 3]. Extending the laser operation to shorter emission wavelengths would be a major breakthrough as such lasers would be of high interest for disinfection, material processing, curing, and medical treatments.
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| 3. |
- Apaydin, Dogukan, 1991, et al.
(författare)
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UVC photonic crystal surface-emitting lasers with low-divergent far-fields
- 2023
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Photonic crystal surface-emitting lasers (PCSEL) emitting in the ultraviolet (UV) C spectral range are exciting devices due to their low divergence and single-mode emission capable of high output powers as already demonstrated in the infrared [1] and blue spectral range [2]. This is due to their unique design, which incorporates a photonic crystal leading to a large optical gain area. PCSELs are based upon in-plane feedback from the photonic crystal and out-of-plane emission by the diffraction of the modes with zero group velocity at the photonic band edges. We recently demonstrated, to the best of our knowledge, the first UVC PCSEL with an emission at 279 nm. The device structure consists of 3 x 2 nm AlGaN quantum wells (QW) in a 60 nm Al0.70Ga0.30N waveguide and AlN cladding layers. The 140x140 μm large photonic crystal is dry etched into the top AlN cladding layer with a hexagonal lattice consisting of circular holes with a lattice constant of 140 nm and an etch depth of 65 nm, leaving 65 nm between the bottom of the photonic crystals and the first quantum well. Lasing in these PCSELs was achieved by resonant pumping of the QWs by a 266 nm pulsed laser with a spot size of 82 μm at room temperature. The devices exhibit threshold pump power densities from 25 down to 13 MW/cm2 showing a spectral narrowing down to 25 pm. Far-field patterns and band structures were investigated for a range of filling factors (fraction of the surface that is etched) between 10% to 26%, and the far-fields contain emission bands that were not yet reported in PCSELs at longer wavelengths. Changing the filling factor affects the photonic crystal band structure and thereby the optical mode at the Γ-point that will reach threshold first. This feature enables us to intentionally select the lasing mode with the desired far-field pattern. By a proper choice of filling factor, the intensity in the angular emission bands is diminished, resulting in a far-field with a narrow beam divergence of <1°.
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| 4. |
- Chalangar, Ebrahim, 1984-, et al.
(författare)
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Influence of morphology on electrical and optical properties of graphene/Al-doped ZnO-nanorod composites
- 2018
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Ingår i: Nanotechnology. - Bristol : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 29:41
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Tidskriftsartikel (refereegranskat)abstract
- The development of future 3D-printed electronics relies on the access to highly conductive inexpensive materials that are printable at low temperatures (<100 C). The implementation of available materials for these applications are, however, still limited by issues related to cost and printing quality. Here, we report on the simple hydrothermal growth of novel nanocomposites that are well suited for conductive printing applications. The nanocomposites comprise highly Al-doped ZnO nanorods grown on graphene nanoplatelets (GNPs). The ZnO nanorods play the two major roles of (i) preventing GNPs from agglomerating and (ii) promoting electrical conduction paths between the graphene platelets. The effect of two different ZnO-nanorod morphologies with varying Al-doping concentration on the nanocomposite conductivity and the graphenedispersity are investigated. Time-dependent absorption, photoluminescence and photoconductivity measurements show that growth in high pH solutions promotes a better graphene dispersity, higher doping levels and enhanced bonding between the graphene and the ZnO nanorods. Growth in low pH solutions yields samples characterized by a higher conductivity and a reduced number of surface defects. These samples also exhibit a large persistent photoconductivity attributed to an effective charge separation and transfer from the nanorods to the graphene platelets. Our findings can be used to tailor the conductivity of novel printable composites, or for fabrication of large volumes of inexpensive porous conjugated graphene-semiconductor composites. © 2018 IOP Publishing Ltd.
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| 5. |
- Chalangar, Ebrahim, PhD student, 1984-, et al.
(författare)
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Synthesis of Vertically Aligned ZnO Nanorods Using Sol-gel Seeding and Colloidal Lithography Patterning
- 2021
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Ingår i: Nanoscale Research Letters. - Heidelberg : Springer Science and Business Media LLC. - 1931-7573 .- 1556-276X. ; 16:1
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Tidskriftsartikel (refereegranskat)abstract
- Different ZnO nanostructures can be grown using low-cost chemical bath deposition. Although this technique is cost-efficient and flexible, the final structures are usually randomly oriented and hardly controllable in terms of homogeneity and surface density. In this work, we use colloidal lithography to pattern (100) silicon substrates to fully control the nanorods' morphology and density. Moreover, a sol-gel prepared ZnO seed layer was employed to compensate for the lattice mismatch between the silicon substrate and ZnO nanorods. The results show a successful growth of vertically aligned ZnO nanorods with controllable diameter and density in the designated openings in the patterned resist mask deposited on the seed layer. Our method can be used to fabricate optimized devices where vertically ordered ZnO nanorods of high crystalline quality are crucial for the device performance.
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| 6. |
- Dabkowska, Aleksandra, et al.
(författare)
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Assembly of RNA nanostructures on supported lipid bilayers.
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 7:2, s. 583-596
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Tidskriftsartikel (refereegranskat)abstract
- The assembly of nucleic acid nanostructures with controlled size and shape has large impact in the fields of nanotechnology, nanomedicine and synthetic biology. The directed arrangement of nano-structures at interfaces is important for many applications. In spite of this, the use of laterally mobile lipid bilayers to control RNA three-dimensional nanostructure formation on surfaces remains largely unexplored. Here, we direct the self-assembly of RNA building blocks into three-dimensional structures of RNA on fluid lipid bilayers composed of cationic 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) or mixtures of zwitterionic 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) and cationic sphingosine. We demonstrate the stepwise supramolecular assembly of discrete building blocks through specific and selective RNA-RNA interactions, based on results from quartz crystal microbalance with dissipation (QCM-D), ellipsometry, fluorescence recovery after photobleaching (FRAP) and total internal reflection fluorescence microscopy (TIRF) experiments. The assembly can be controlled to give a densely packed single layer of RNA polyhedrons at the fluid lipid bilayer surface. We show that assembly of the 3D structure can be modulated by sequence specific interactions, surface charge and changes in the salt composition and concentration. In addition, the tertiary structure of the RNA polyhedron can be controllably switched from an extended structure to one that is dense and compact. The versatile approach to building up three-dimensional structures of RNA does not require modification of the surface or the RNA molecules, and can be used as a bottom-up means of nanofabrication of functionalized bio-mimicking surfaces.
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| 7. |
- Das, Atanu Kumar, et al.
(författare)
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Applications of organic-based nanocomposites in corrosion protection
- 2023
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Ingår i: Nanocomposites-Advanced Materials for Energy and Environmental Aspects. - : Elsevier. - 9780323997041 ; , s. 579-590
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Corrosion protection is one of the utmost aims for the reduction of maintenance costs with higher production for the industry. The conventional toxic chromate-based coating is an environmental concern, which has led researchers to develop an organic-based coating with higher anticorrosive performance. The incorporation of nanocomposite increases the adhesion capability of the coating to the metal surface leading to protecting the metal from corrosion. Nanocomposites have novel mechanical and electrochemical properties. The type of nanocomposites depends on the type of nanostructured filler. The performance of nanocomposite coating depends on the types of nanoparticles and additives, the concentration of the dispersed particles, and the mixing processes. In this chapter, nanocellulose-based nanocomposites, their synthesis, and performance against corrosion protection have been discussed. The potential of these nanocomposites as corrosion inhibitors has been pointed out as well.
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| 8. |
- Das, Atanu Kumar, et al.
(författare)
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Developments of nanocomposites in supercapacitor applications
- 2023
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Ingår i: Nanocomposites-Advanced Materials for Energy and Environmental Aspects. - : Elsevier. - 9780323997041
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Energy demand is increasing due to the development of modern society. The use of electronic devices including portable ones is increasing gradually. Thus it is influencing the development of supercapacitors for energy storage due to their 10–100 times higher energy storage capacity. At the same time, the implication of biobased material is being considered as environmentally friendly. Cellulose is the most abundant natural renewable biomaterial. Nanocellulose obtained from cellulose possesses special mechanical and electrochemical properties that are being applied for the fabrication of supercapacitors, such as their low-cost and high conductivity and their inexpensive and environment-friendly natures. The development strategy and performance are discussed for better understanding. The work undertaken on improving the fabrication of supercapacitors from cellulose-based nanocomposites will also be summarized.
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| 9. |
- Das, Atanu Kumar, et al.
(författare)
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Nanocomposites in energy storage applications
- 2023
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Ingår i: Nanocomposites-Advanced Materials for Energy and Environmental Aspects. - : Elsevier BV. - 9780323997041 ; , s. 175-187
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The development of energy storage devices for the growing energy demand is a prerequisite for modern society. Specific characteristics, i.e., thermal, electrochemical, and mechanical properties, of nanocomposites are essential for their application in energy storage appliances. Biobased nanocomposites are being considered environmentally friendly. Nanocellulose, lignin, and chitosan are obtained from an abundant source of natural renewable materials. Using them in developing batteries and supercapacitors has great potential for a sustainable supply of energy. Nanocellulose and the lignin-based electrode have shown excellent electrochemical properties for application in a battery. Nanocellulose, lignin, and chitosan-based electrode have also exhibited excellent electrochemical properties for their utilization in supercapacitors. In addition, their low-cost, high conductivity, and environment-friendly nature are being considered for the preparation of energy storage devices. In this chapter, the development strategy and performance of batteries and supercapacitors obtained from biobased nanocomposites have been discussed.
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| 10. |
- Das, Atanu Kumar, et al.
(författare)
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Natural Fiber-based Nanocomposites as Corrosion Inhibitors
- 2022
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Ingår i: Anticorrosive Nanomaterials. - Cambridge : Royal Society of Chemistry (RSC). ; :56, s. 191-206
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Corrosion constitutes one of the troublesome issues in different industries, i.e., automotive, marine, construction, oil and gas. Protection from corrosion aims at reducing maintenance costs with higher production for the industry. Due to high toxicity, chromate-based coatings remain an environmental concern. This has necessitated the development of an organic-based coating with higher anti-corrosive performance. The adhesion capability of coating on metal surfaces can be improved through the incorporation of nanocomposites, which in turn can protect the metal from corrosion. Owing to their novel mechanical and electrochemical properties, types of nanocomposites dictate the types of nanostructured filler. The inclusion of cellulose nanocrystal (CNC) in epoxy-Zn rich coating shows better anti-corrosive performance for mild steel. In addition, silver nanoparticles and chitosan-based nanocomposite coating can protect mild steel from corrosion. However, the performance of the nanocomposite coating depends on the types of nanoparticles and additives, the concentration of the dispersed particles and mixing processes. In this chapter, the use of natural fiber-based nanocomposites in corrosion protection, and their synthesis and performance have been discussed. Alongside this, the potential of natural fiber-based nanocomposites for corrosion protection has been pointed out.
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