| 1. |
- Unksov, Ivan N., et al.
(author)
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Fluorescence excitation enhancement by waveguiding nanowires
- 2023
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In: Nanoscale Advances. - : Royal Society of Chemistry (RSC). - 2516-0230. ; 5:6, s. 1760-1766
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Journal article (peer-reviewed)abstract
- The optical properties of vertical semiconductor nanowires can allow an enhancement of fluorescence from surface-bound fluorophores, a feature proven useful in biosensing. One of the contributing factors to the fluorescence enhancement is thought to be the local increase of the incident excitation light intensity in the vicinity of the nanowire surface, where fluorophores are located. However, this effect has not been experimentally studied in detail to date. Here, we quantify the excitation enhancement of fluorophores bound to a semiconductor nanowire surface by combining modelling with measurements of fluorescence photobleaching rate, indicative of the excitation light intensity, using epitaxially grown GaP nanowires. We study the excitation enhancement for nanowires with a diameter of 50-250 nm and show that excitation enhancement reaches a maximum for certain diameters, depending on the excitation wavelength. Furthermore, we find that the excitation enhancement decreases rapidly within tens of nanometers from the nanowire sidewall. The results can be used to design nanowire-based optical systems with exceptional sensitivities for bioanalytical applications.
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| 2. |
- Graczyk, Mariusz, et al.
(author)
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Fabrication of bottle-shaped nanochannels in fused silica using a self-closing effect
- 2012
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In: Microelectronic Engineering. - : Elsevier BV. - 1873-5568 .- 0167-9317. ; 97, s. 173-176
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Journal article (peer-reviewed)abstract
- The spatial control of molecular motor function, using nanostructured surfaces, is of great interest for the development of commercial devices for diagnostics and high-throughput drug screening with molecular motors as targets. In the present study we have fabricated 100-300 nm wide nanochannels, completely subsurfaced on fused silica chips, with the aim to interface them with a microfluidic system. Such a system will allow for changes in the chemical environment surrounding molecular motors, with minimal influence on their directional motion. This will be achieved by changing the chemical environment in a perpendicular direction to the motor motion and allowing the chemical substances to diffuse in and out of the nanochannels via a small slit (5-10 nm) on the top of the nanochannels. To create this slit, and to control its width, we here demonstrate the use of a self-closing effect based on the volume increase (2.27 times) during oxidation of silicon. The details of the fabrication steps (EBL, RIE and oxidation) are discussed. (C) 2012 Elsevier B.V. All rights reserved.
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| 3. |
- Graczyk, Mariusz, et al.
(author)
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Optimization of a self-closing effect to produce nanochannels with top slits in fused silica
- 2012
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In: Journal of Vacuum Science and Technology B. - : American Vacuum Society. - 1520-8567. ; 30:6
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Journal article (peer-reviewed)abstract
- The authors report on the fabrication of subsurfaced 100-600 nm wide nanochannels in fused silica with top slit openings in the size range of 5-10 nm. Such nanochannels can be used in combination with a nanofluidics system to guide molecular motors and quickly switch the chemical environment inside the nanochannels through diffusion via the top slits. To realize nanochannel top slits in this size range, the authors here demonstrate the use of a self-closing effect based on the volume expansion of a thin Si layer during oxidation. A high contrast electron beam lithography exposure step in conjunction with dry etching of SiO2 by reactive ion etching (RIE) and Si by inductively coupled plasma-RIE followed by wet etching of a fused silica substrate is used to create the initial slit before oxidation. The details of nanochannel fabrication steps are described and discussed. (C) 2012 American Vacuum Society. [http://dx.doi.org/10.1116/1.4766317]
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| 4. |
- Lindberg, Frida W., et al.
(author)
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Design and development of nanoimprint-enabled structures for molecular motor devices
- 2019
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In: Materials Research Express. - : IOP Publishing. - 2053-1591. ; 6:2
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Journal article (peer-reviewed)abstract
- Devices based on molecular motor-driven cytoskeletal filaments, e.g., actin filaments, have been developed both for biosensing and biocomputational applications. Commonly, these devices require nanoscaled tracks for guidance of the actin filaments which has limited the patterning technique to electron beam lithography. Thus, large scale systems become intractable to fabricate at a high throughput within a reasonable time-frame. We have studied the possibility to fabricate molecular motor-based devices using the high throughput, high resolution technique of nanoimprint lithography. Molecular motor-based devices require wide open regions (loading zones) to allow filaments to land for later propulsion into the nanoscale tracks. Such open zones are challenging to fabricate using nanoimprint lithography due to the large amount of material displaced in the process. We found that this challenge can be overcome by introducing nanoscaled pillars inside the loading zones, into which material can be displaced during imprint. By optimising the resist thickness, we were able to decrease the amount of material displaced without suffering from insufficient filling of the stamp. Furthermore, simulations suggest that the shape and positioning of the pillars can be used to tailor the overall cytoskeletal filament transportation direction and behaviour. This is a potentially promising design feature for future applications that however, requires further optimisations before experimental realisation.
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| 5. |
- Unksov, Ivan N., et al.
(author)
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Through the Eyes of Creators: Observing Artificial Molecular Motors : ACS Nanoscience Au
- 2022
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In: ACS Nanoscience AU. - : American Chemical Society (ACS). - 2694-2496.
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Journal article (peer-reviewed)abstract
- Inspired by molecular motors in biology, there hasbeen significant progress in building artificial molecular motors, usinga number of quite distinct approaches. As the constructs become moresophisticated, there is also an increasing need to directly observe themotion of artificial motors at the nanoscale and to characterize theirperformance. Here, we review the most used methods that tacklethose tasks. We aim to help experimentalists with an overview of theavailable tools used for different types of synthetic motors and tochoose the method most suited for the size of a motor and the desiredmeasurements, such as the generated force or distances in the movingsystem. Furthermore, for many envisioned applications of syntheticmotors, it will be a requirement to guide and control directed motions.We therefore also provide a perspective on how motors can be observed on structures that allow for directional guidance, such asnanowires and microchannels. Thus, this Review facilitates the future research on synthetic molecular motors, where observations ata single-motor level and a detailed characterization of motion will promote applications.
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| 6. |
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| 7. |
- Karimi, Mohammad, 1988-, et al.
(author)
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Nanowire photodetectors with embedded quantum heterostructures for infrared detection
- 2019
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In: Infrared physics & technology. - Amsterdam : Elsevier. - 1350-4495 .- 1879-0275. ; 96, s. 209-212
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Journal article (peer-reviewed)abstract
- Nanowires offer remarkable opportunities for realizing new optoelectronic devices because of their unique fundamental properties. The ability to engineer nanowire heterostructures with large bandgap variations is particularly interesting for technologically important broadband photodetector applications. Here we report on infrared photodetectors based on arrays of InP nanowires with embedded InAsP quantum discs. We demonstrate a strongly reduced dark current in the detector elements by compensating the unintentional n-doping in the nominal intrinsic region of the InP nanowires by in-situ doping with Zn, a crucial step towards realizing high-performance devices. The optimized array detectors show a broad spectral sensitivity at normal incidence for wavelengths from visible to far-infrared up to 20 μm, promoted by both interband and intersubband transitions. Optical simulations show that the unexpected normal incidence response at long wavelengths is due to non-zero longitudinal modes hosted by the nanowires. © 2018 Elsevier B.V.
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| 8. |
- Valderas Gutiérrez, Julia, et al.
(author)
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Enhanced Optical Biosensing by Aerotaxy Ga(As)P Nanowire Platforms Suitable for Scalable Production
- 2022
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In: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 5:7, s. 9063-9071
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Journal article (peer-reviewed)abstract
- Sensitive detection of low-abundance biomolecules is central for diagnostic applications. Semiconductor nanowires can be designed to enhance the fluorescence signal from surface-bound molecules, prospectively improving the limit of optical detection. However, to achieve the desired control of physical dimensions and material properties, one currently uses relatively expensive substrates and slow epitaxy techniques. An alternative approach is aerotaxy, a high-throughput and substrate-free production technique for high-quality semiconductor nanowires. Here, we compare the optical sensing performance of custom-grown aerotaxyproduced Ga(As)P nanowires vertically aligned on a polymer substrate to GaP nanowires batch-produced by epitaxy on GaP substrates. We find that signal enhancement by individual aerotaxy nanowires is comparable to that from epitaxy nanowires and present evidence of single-molecule detection. Platforms based on both types of nanowires show substantially higher normalized-to-blank signal intensity than planar glass surfaces, with the epitaxy platforms performing somewhat better, owing to a higher density of nanowires. With further optimization, aerotaxy nanowires thus offer a pathway to scalable, low-cost production of highly sensitive nanowire-based platforms for optical biosensing applications.
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| 9. |
- Boyle, Aimee L., et al.
(author)
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Squaring the Circle in Peptide Assembly: From Fibers to Discrete Nanostructures by de Novo Design
- 2012
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In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 134:37, s. 15457-15467
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Journal article (peer-reviewed)abstract
- The design of bioinspired nanostructures and materials of defined size and shape is challenging as it pushes our understanding of biomolecular assembly to its limits. In such endeavors, DNA is the current building block of choice because of its predictable and programmable self-assembly. The use of peptide- and protein-based systems, however, has potential advantages due to their more-varied chemistries, structures and functions, and the prospects for recombinant production through gene synthesis and expression. Here, we present the design and characterization of two complementary peptides programmed to form a parallel heterodimeric coiled coil, which we use as the building blocks for larger, supramolecular assemblies. To achieve the latter, the two peptides are joined via peptidic linkers of variable lengths to produce a range of assemblies, from flexible fibers of indefinite length, through large colloidal-scale assemblies, down to closed and discrete nanoscale objects of defined stoichiometry. We posit that the different modes of assembly reflect the interplay between steric constraints imposed by short linkers and the bulk of the helices, and entropic factors that favor the formation of many smaller objects as the linker length is increased. This approach, and the resulting linear and proteinogenic polypeptides, represents a new route for constructing complex peptide-based assemblies and biomaterials.
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| 10. |
- Bromley, Elizabeth H. C., et al.
(author)
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The Tumbleweed: towards a synthetic protein motor
- 2009
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In: HFSP Journal. - : Informa UK Limited. - 1955-2068. ; 3:3, s. 204-212
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Journal article (peer-reviewed)abstract
- Biomolecular motors have inspired the design and construction of artificial nanoscale motors and machines based on nucleic acids, small molecules, and inorganic nanostructures. However, the high degree of sophistication and efficiency of biomolecular motors, as well as their specific biological function, derives from the complexity afforded by protein building blocks. Here, we discuss a novel bottom-up approach to understanding biological motors by considering the construction of synthetic protein motors. Specifically, we present a design for a synthetic protein motor that moves along a linear track, dubbed the "Tumbleweed." This concept uses three discrete ligand-dependent DNA-binding domains to perform cyclically ligand-gated, rectified diffusion along a synthesized DNA molecule. Here we describe how de novo peptide design and molecular biology could be used to produce the Tumbleweed, and we explore the fundamental motor operation of such a design using numerical simulations. The construction of this and more sophisticated protein motors is an exciting challenge that is likely to enhance our understanding of the structure-function relationship in biological motors. [DOI: 10.2976/1.3111282]
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