| 1. |
- Karlsson, M., et al.
(författare)
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Wafer-scale epitaxial graphene on SiC for sensing applications
- 2015
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE - The International Society for Optics and Photonics. - 9781628418903
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Konferensbidrag (refereegranskat)abstract
- The epitaxial graphene-on-silicon carbide (SiC-G) has advantages of high quality and large area coverage owing to a natural interface between graphene and SiC substrate with dimension up to 100 mm. It enables cost effective and reliable solutions for bridging the graphene-based sensors/devices from lab to industrial applications and commercialization. In this work, the structural, optical and electrical properties of wafer-scale graphene grown on 2'™'™ 4H semi-insulating (SI) SiC utilizing sublimation process were systemically investigated with focus on evaluation of the graphene'™s uniformity across the wafer. As proof of concept, two types of glucose sensors based on SiC-G/Nafion/Glucose-oxidase (GOx) and SiC-G/Nafion/Chitosan/GOx were fabricated and their electrochemical properties were characterized by cyclic voltammetry (CV) measurements. In addition, a few similar glucose sensors based on graphene by chemical synthesis using modified Hummer'™s method were also fabricated for comparison.
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| 2. |
- Zhao, Wei, et al.
(författare)
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Evaluation of Zinc Oxide Nano-Microtetrapods for Biomolecule Sensing Applications
- 2015
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Ingår i: MICRO+NANO MATERIALS, DEVICES, AND SYSTEMS. - : SPIE - International Society for Optical Engineering. - 9781628418903
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Konferensbidrag (refereegranskat)abstract
- Zinc oxide tetrapods (ZnO-Ts) were synthesized by flame transport synthesis using Zn microparticles. This work herein reports a systematical study on the structural, optical and electrochemical properties of the ZnO-Ts. The morphology of the ZnO-Ts was confirmed by scanning electron microscopy (SEM) as joint structures of four nano-microstructured legs, of which the diameter of each leg is 0.7-2.2 mu m in average from the tip to the stem. The ZnO-Ts were dispersed in glucose solution to study the luminescence as well as photocatalytic activity in a mimicked biological environment. The photoluminescence (PL) intensity in the ultraviolet (UV) region decreased with linear dependence on the glucose concentration up to 4 mM. The ZnO-Ts were also attached with glucose oxidase (GOx) and over coated with a thin film of Nafion to form active layers on Si/SiO2/Au substrate for electrochemical glucose sensing. The attachment of GOx and the coating of Nafion onto ZnO-Ts were confirmed by Fourier transform infrared spectroscopy (FT-IR). Furthermore, the current response of the active layers based on ZnO-Ts was investigated by cyclic voltammetry (CV) in various glucose concentration conditions. Stable current response of glucose was detected with linear dependence on the glucose concentration up to 12 mM, which confirms the potential of ZnO-Ts for biomolecule sensing applications.
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| 3. |
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| 4. |
- Doddapaneni, Venkatesh, et al.
(författare)
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Improving Uv Radiation Absorption by Copper Oxide NPs/PMMA Nanocomposites for Electrical Switching Applications
- 2015
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Ingår i: Powder metallurgy and metal ceramics. - : Springer. - 1068-1302 .- 1573-9066. ; 54:7-8, s. 397-401
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposites based on the radiation absorbing polymer (PNCs) are of interest for a variety of applications including circuit breakers, UV-shielding windows, contact lenses, and glasses among others. Such PNCs can be made by incorporating suitable radiation absorbing nanoparticles into a polymeric matrix by in situ polymerization. In this study, spherical nanoparticles (5-6 nm) of oleic acid (OA) surface modified cupric oxide (CuO) are synthesized and used to improve the ultra-violet (UV) radiation absorption property of a polymer matrix, i.e., polymethylmethacrylate (PMMA). The synthesis of spherical CuO nanoparticles, surface modification using OA, dispersion of CuO nanoparticles with different concentrations in PMMA, and UV radiation absorption property of the resultant PNC are investigated. Two different PNCs are produced using OA modified CuO nanoparticles with different concentrations. As synthesized CuO nanoparticles and OA modified CuO nanoparticles are examined by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) techniques. The UV absorption edges are evaluated from the UV-Vis absorption spectra by using UV-Visible absorption spectroscopy. The results show that the UV radiation absorption of the PNC with higher concentration of CuO nanoparticles is improved compared with PMMA and the absorption edge moved towards longer wavelengths i.e., from 271 to 281 nm. These PNCs are successful in arc interruption process by absorbing a broad range of radiation emitted from high-energy copper arcs produced in the circuit breakers.
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| 5. |
- El-Sayed, Ramy, et al.
(författare)
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Single-Walled Carbon Nanotubes Inhibit the Cytochrome P450 Enzyme, CYP3A4
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- We report a detailed computational and experimental study of the interaction of single-walled carbon nanotubes (SWCNTs) with the drug-metabolizing cytochrome P450 enzyme, CYP3A4. Dose-dependent inhibition of CYP3A4-mediated conversion of the model compound, testosterone, to its major metabolite, 6 beta-hydroxy testosterone was noted. Evidence for a direct interaction between SWCNTs and CYP3A4 was also provided. The inhibition of enzyme activity was alleviated when SWCNTs were pre-coated with bovine serum albumin. Furthermore, covalent functionalization of SWCNTs with polyethylene glycol (PEG) chains mitigated the inhibition of CYP3A4 enzymatic activity. Molecular dynamics simulations suggested that inhibition of the catalytic activity of CYP3A4 is mainly due to blocking of the exit channel for substrates/products through a complex binding mechanism. This work suggests that SWCNTs could interfere with metabolism of drugs and other xenobiotics and provides a molecular mechanism for this toxicity. Our study also suggests means to reduce this toxicity, eg., by surface modification.
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| 6. |
- Khachatourian, Malek Adrine, et al.
(författare)
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Green synthesis of Y2O3:Eu3+ nanocrystals for bioimaging
- 2015
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Ingår i: Materials Research Society Symposium Proceedings. - : Materials Research Society. - 9781510806054 ; , s. 59-64
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Konferensbidrag (refereegranskat)abstract
- Rare earth (e.g., Eu, Er, Yb, Tm) doped Y2O3 nanocrystals are promising fluorescent bioimaging agents which can overcome well known problems of currently used organic dyes like photobleaching, phototoxicity, and light scattering. Furthermore, the alternative quantum dots (QDs) composed of heavy metals (e.g., CdSe) possess inherently low biocompatibility due to the heavy metal content. In the present work, monodisperse spherical Y2O3:Eu3+ nanocrystals were successfully synthesized by microwave assisted urea precipitation method followed by thermochemical treatment. This is a green, fast and reproducible synthesis method, which is surfactant and hazardous precursors free. The as prepared particles were non-aggregated, spherical particles with a narrow size distribution. The calcined particles have a polycrystalline structure preserving the monodispersity and the spherical morphology of the as prepared particles. After calcination of Y(OH)CO3:Eu3+ precursors at 900°C for 2 hours, a highly crystalline cubic Y2O3 structure was obtained. The Y2O3:Eu3+ spherical particles showed a strong red emission peak at 613nm due to the 5D0-7F2 forced electric dipole transition of Eu3+ ions under UV excitation (235 nm) as revealed by the photoluminescence analysis (PL). The effect of reaction time on size and photoluminescence properties of calcined particles and also the effect of reaction temperature and pressure on the size and the yield of the precipitation process have been studied. The intense red fluorescent emission, excellent stability and potential low toxicity make these QDs promising for applications in bio-related areas such as fluorescence cell imaging or fluorescence bio labels.
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| 7. |
- Lobov, Gleb, et al.
(författare)
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Dynamic manipulation of optical anisotropy of suspended Poly-3-hexylthiophene nanofibers
- 2016
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Ingår i: Advanced Optical Materials. - : Wiley. - 2162-7568 .- 2195-1071. ; 4:10, s. 1651-1656
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Tidskriftsartikel (refereegranskat)abstract
- Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline semiconducting nanostructures, which are known for their application in photovoltaics. Due to the internal arrangement, P3HT nanofibers possess optical anisotropy, which can be enhanced on a macroscale if nanofibers are aligned. Alternating electric field, applied to a solution with dispersed nanofibers, causes their alignment and serves as a method to produce solid layers with ordered nanofibers. The transmission ellipsometry measurements demonstrate the dichroic absorption and birefringence of ordered nanofibers in a wide spectral range of 400–1700 nm. Moreover, the length of nanofibers has a crucial impact on their degree of alignment. Using electric birefringence technique, it is shown that external electric field applied to the solution with P3HT nanofibers can cause direct birefringence modulation. Dynamic alignment of dispersed nanofibers changes the refractive index of the solution and, therefore, the polarization of transmitted light. A reversible reorientation of nanofibers is organized by using a quadrupole configuration of poling electrodes. With further development, the described method can be used in the area of active optical fiber components, lab-on-chip or sensors. It also reveals the potential of 1D conducting polymeric structures as objects whose highly anisotropic properties can be implemented in electro-optical applications..
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| 8. |
- Lobov, Gleb, et al.
(författare)
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Electro-optical effects of high aspect ratio P3HT nanofibers colloid in polymer micro-fluid cells
- 2017
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Ingår i: Optics Letters. - : OSA Publishing. - 0146-9592 .- 1539-4794. ; 42:11, s. 2157-2160
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Tidskriftsartikel (refereegranskat)abstract
- This Letter reports the electro-optical (EO) effect of Poly(3-hexylthiophene-2,5-diyl) (P3HT) nanofibers colloid in a polymer micro-fluidic EO cell. P3HT nanofibers are high aspect ratio semiconducting nanostructures, and can be collectively aligned by an external alternating electric field. Optical transmission modulated by the electric field is a manifestation of the electro-optical effect due to high inner crystallinity of P3HT nanofibers. According to our results, the degree of alignment reaches a maximum at 0.6 V/μm of electric field strength, implying a big polarizability value due to geometry and electrical properties of P3HT nanofibers. We believe that one-dimensional crystalline organic nanostructures have a large potential in EO devices due to their significant anisotropy, wide variety of properties, low actuation voltages, and opportunity to be tailored via adjustment of the fabrication process.
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| 9. |
- Lobov, Gleb, et al.
(författare)
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Optical birefringence from P3HT nanofibers in alternating electric field
- 2016
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Ingår i: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781943580194
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Konferensbidrag (refereegranskat)abstract
- AC poling allowing to control the orientation of P3HT nanofibers, result in strong optical birefringence with promising implementation in a novel type of optical modulator, without necessary embedding into any hosting matrix, e.g. liquid crystal.
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| 10. |
- Lobov, G. S., et al.
(författare)
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Direct birefringence and transmission modulation via dynamic alignment of P3HT nanofibers in an advanced opto-fluidic component
- 2017
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Ingår i: Optical Materials Express. - 2159-3930 .- 2159-3930. ; 7:1, s. 52-61
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Tidskriftsartikel (refereegranskat)abstract
- Poly-3-hexylthiophene (P3HT) nanofibers are semiconducting high-aspect ratio nanostructures with anisotropic absorption and birefringence properties found at different regions of the optical spectrum. In addition, P3HT nanofibers possess an ability to be aligned by an external electric field, while being dispersed in a liquid. In this manuscript we show that such collective ordering of nanofibers, similar to liquid crystal material, significantly changes the properties of transmitted light. With a specially fabricated opto-fluidic component, we monitored the phase and transmission modulation of light propagating through the solution of P3HT nanofibers, being placed in the electric field with strength up to 0.1 V/μm. This report describes a technique for light modulation, which can be implemented in optical fiber-based devices or on-chip integrated components.
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