| 1. |
- Alene Asres, Georgies, et al.
(författare)
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A novel WS2 nanowire-nanoflake hybrid material synthesized from WO3 nanowires in sulfur vapor
- 2016
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 6:25610
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Tidskriftsartikel (refereegranskat)abstract
- In this work, WS2 nanowire-nanoflake hybrids are synthesized by the sulfurization of hydrothermally grown WO3 nanowires. The influence of temperature on the formation of products is optimized to grow WS2 nanowires covered with nanoflakes. Current-voltage and resistance-temperature measurements carried out on random networks of the nanostructures show nonlinear characteristics and negative temperature coefficient of resistance indicating that the hybrids are of semiconducting nature. Bottom gated field effect transistor structures based on random networks of the hybrids show only minor modulation of the channel conductance upon applied gate voltage, which indicates poor electrical transport between the nanowires in the random films. On the other hand, the photo response of channel current holds promise for cost-efficient solution process fabrication of photodetector devices working in the visible spectral range.
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| 2. |
- Asres, Georgies Alene, et al.
(författare)
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High photoresponse of individual WS2 nanowire-nanoflake hybrid materials
- 2018
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Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 112:23
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Tidskriftsartikel (refereegranskat)abstract
- van der Waals solids have been recognized as highly photosensitive materials that compete conventional Si and compound semiconductor based devices. While 2-dimensional nanosheets of single and multiple layers and 1-dimensional nanowires of molybdenum and tungsten chalcogenides have been studied, their nanostructured derivatives with complex morphologies are not explored yet. Here, we report on the electrical and photosensitive properties of WS2 nanowire-nanoflake hybrid materials we developed lately. We probe individual hybrid nanostructured particles along the structure using focused ion beam deposited Pt contacts. Further, we use conductive atomic force microscopy to analyze electrical behavior across the nanostructure in the transverse direction. The electrical measurements are complemented by in situ laser beam illumination to explore the photoresponse of the nanohybrids in the visible optical spectrum. Photodetectors with responsivity up to similar to 0.4 AW(-1) are demonstrated outperforming graphene as well as most of the other transition metal dichalcogenide based devices. Published by AIP Publishing.
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| 3. |
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| 4. |
- Botros, Milad, et al.
(författare)
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Endomorphins interact with the substance P (SP) aminoterminal SP (1-7) binding in the ventral tegmental area of the rat brain
- 2008
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Ingår i: Peptides. - : Elsevier BV. - 0196-9781 .- 1873-5169. ; 29:10, s. 1820-1824
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Tidskriftsartikel (refereegranskat)abstract
- We have recently identified a specific binding site for the tachykinin peptide substance P (SP) fragment SP1-7 in the rat spinal cord. This site appeared very specific for SP1-7 as the binding affinity of this compound highly exceeded those of other SP fragments. We also observed that endomorphin-2 (EM-2) exhibited high potency in displacing SP1-7 from this site. In the present work using a [H-3]-labeled derivative of the heptapeptide we have identified and characterized [H-3]-SP1-7 binding in the rat ventral tegmental area (VTA). Similarly to the [H-3]-SP1-7 binding in the spinal cord the affinity of unlabeled SP1-7 to the specific site in VTA was significantly higher than those of other SP fragments. Further, the tachykinin receptor NK-1, NK-2 and NK-3 ligands showed no or negligible binding to the identified site. However, the mu-opioid peptide (MOP) receptor agonists DAMGO, EM-1 and EM-2 did, and significant difference was observed in the binding affinity between the two endomorphins. As recorded from displacement curves the affinity of EM-2 for the SP1-7 site was 4-5 times weaker than that for SP1-7 but about 5 times higher than that of EM-1. The opioid receptor antagonists naloxone and naloxonazine showed weak or negligible binding. it was concluded that the specific site identified for SP1-7 binding in the rat VTA is distinct from the MOP receptor although it exhibits high affinity for EM-2.
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| 5. |
- Fu, Qilin, 1986-, et al.
(författare)
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High dynamic stiffness mechanical structures with nanostructured composite coatings deposited by high power impulse magnetron sputtering
- 2016
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Ingår i: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 98, s. 24-33
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured Cu:CuCNx composite coatings with high static and dynamic stiffness were synthesized by means of plasma-enhanced chemical vapor deposition (PECVD) combined with high power impulse magnetron sputtering (HiPIMS). Scanning electron microscope (SEM) images and energy-dispersive X-ray spectroscopy (EDS) mapping from cross-sectioned samples reveals a multi-layered nanostructure enriched in Cu, C, N, and O in different ratios. Mechanical properties of the coatings were investigated by Vickers micro-indention and model tests. It was observed that copper inclusions as well as copper interlayers in the CNx matrix can increase mechanical damping by up to 160%. Mechanical properties such as hardness, elastic modulus and loss factor were significantly improved by increasing the discharge power of the sputtering process. Moreover the coatings loss modulus was evaluated on the basis of indentation creep measurements under room temperature. The coating with optimum properties exhibited loss modulus of 2.6 GPa. The composite with the highest damping loss modulus were applied on the clamping region of a milling machining tool to verify their effect in suppressing regenerative tool chatter. The high dynamic stiffness coatings were found to effectively improve the critical stability limit of a milling tool by at least 300%, suggesting a significant increase of the dynamic stiffness.
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| 6. |
- Fu, Qilin, 1986-, et al.
(författare)
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Suppressing tool chatter with novel multi-layered nanostructures of carbon based composite coatings
- 2015
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 223, s. 292-298
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Tidskriftsartikel (refereegranskat)abstract
- Multi-layered nanostructured Cu and Cu-CNx composites synthesized by plasma-enhanced chemical vapour deposition were applied in the clamping area of a milling tool to suppress regenerative tool chatter. Scanning electron microscopy analysis showed a multi-layered nanostructure with excellent conformality, i.e. coating is not only uniform on planar surfaces but also around corners of the substrate. Cu:CuCNx nanostructured multilayers with thicknesses of approximately 0.5:1.6 mu m were obtained. With a diameter of 20 mm, the milling tool performed slotting processes at an overhang length of 120 mm. Modal analysis showed that a coating, with a thickness of approximately 300 mu m, can add sufficient damping without losing stiffness of the tool, to increase the critical stability limit by 50% or 100% depending on cutting direction.
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| 7. |
- Gach, Katarzyna, et al.
(författare)
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Synthesis and biological evaluation of novel peripherally active morphiceptin analogs.
- 2010
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Ingår i: Peptides. - Amsterdam : Elsevier BV. - 1873-5169 .- 0196-9781. ; 31:8, s. 1617-1624
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Tidskriftsartikel (refereegranskat)abstract
- Morphiceptin (Tyr-Pro-Phe-Pro-NH(2)), a tetrapeptide present in the enzymatic digest of bovine beta-casein, is a selective ligand of the mu-opioid receptor. In the present study, we describe the synthesis of a series of novel morphiceptin analogs modified in positions 1-3. Two of the obtained analogs, [Dmt(1), d-Ala(2), d-1-Nal(3)]morphiceptin and [Dmt(1), d-NMeAla(2), d-1-Nal(3)]morphiceptin (Dmt-2',6'-dimethyltyrosine and d-1-Nal-3-(1-naphthyl)-d-alanine)) displayed very high mu-receptor affinity, resistance to enzymatic degradation, and remarkable supraspinally mediated analgesia, as shown in the hot-plate test after intracerebroventricular but not intravenous administration, which indicated that they could not cross the blood-brain barrier. Therefore, these two analogs were further tested in vitro and in vivo towards their possible peripheral analgesic activity and inhibitory effect on gastrointestinal (GI) motility. We report that both peptides showed strong antinociceptive effect in the writhing test after intraperitoneal administration, inhibited smooth muscle contractility in vitro and GI motility in vivo. Taken together, these findings indicate that the novel morphiceptin analogs which induce peripheral, but not central antinociception, inhibit GI transit, and possess exceptional metabolic stability, may provide an interesting approach to the development of peripherally restricted agents for the treatment of GI motility disorders, such as diarrhea or diarrhea-predominant irritable bowel syndrome.
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| 8. |
- Halonen, Niina, et al.
(författare)
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Low-temperature growth of multi-walled carbon nanotubes by thermal CVD
- 2011
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Ingår i: Physica status solidi. B, Basic research. - Malden : Wiley-Blackwell. - 0370-1972 .- 1521-3951. ; 248:11, s. 2500-2503
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Tidskriftsartikel (refereegranskat)abstract
- Low-temperature thermal chemical vapor deposition (thermal CVD) synthesis of multi-walled carbon nanotubes (MWCNTs) was studied using a large variety of different precursor compounds. Cyclopentene oxide, tetrahydrofuran, methanol, and xylene: methanol mixture as oxygen containing heteroatomic precursors, while xylene and acetylene as conventional hydrocarbon feedstocks were applied in the experiments. The catalytic activity of Co, Fe, Ni, and their bi-as well as tri-metallic combinations were tested for the reactions. Low-temperature CNT growth occurred at 400 degrees C when using bi-metallic Co-Fe and tri-metallic Ni-Co-Fe catalyst (on alumina) and methanol or acetylene as precursors. In the case of monometallic catalyst nanoparticles, only Co (both on alumina and on silica) was found to be active in the low temperature growth (below 500 degrees C) from oxygenates such as cyclopentene oxide and methanol. The structure and composition of the achieved MWCNTs products were studied by scanning and transmission electron microscopy (SEM and TEM) as well as by Raman and X-ray photoelectron spectroscopy (XPS) and by X-ray diffraction (XRD). The successful MWCNT growth below 500 degrees C is promising from the point of view of integrating MWCNT materials into existing IC fabrication technologies. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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| 9. |
- Kordás, Krisztián, et al.
(författare)
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Nanoparticle Dispersions
- 2013
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Ingår i: Springer Handbook of Nanomaterials. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642205941 - 9783642205958 ; , s. 729-776
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Bokkapitel (refereegranskat)abstract
- This chapter aims to provide an insight into the physics and chemistry of nanoparticle–liquid systems. The first part of the chapter discusses parameters and effects that influence dispersion stability (Sect. 20.1), including particle size and shape as well as the interactions at the interface between the solid and liquid phases. Section 20.2 summarizes the practical aspects of making a dispersion, collecting and listing hundreds of examples from contemporary literature. Because of the broad spectrum of materials in question, the survey is limited to dispersions of inorganic nanoparticles including metals, their oxides/sulfides, some (compound) semiconductors, as well as nanostructured carbon particles such as fullerenes, nanotubes, and graphene/graphite (Sect. 20.3). Dispersions of polymers of either synthetic or biological origin lie beyond the scope of this work. Since a very large fraction of applications are related to various surface coatings using dispersions as the source of nanoparticles, Sect. 20.4 is devoted to drying phenomena and particle self-ordering.
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| 10. |
- Kukkola, Jarmo, et al.
(författare)
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Electrical transport through single-wall carbon nanotube-anodic aluminum oxide-aluminum heterostructures
- 2010
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 21:3, s. 35707-
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Tidskriftsartikel (refereegranskat)abstract
- Aluminum foils were anodized in sulfuric acid solution to form thick porous anodic aluminum oxide (AAO) films of thickness approximately 6 microm. Electrodes of carboxyl-functionalized single-wall carbon nanotube (SWCNT) thin films were inkjet printed on the anodic oxide layer and the electrical characteristics of the as-obtained SWCNT-AAO-Al structures were studied. Nonlinear current-voltage transport and strong temperature dependence of conduction through the structure was measured. The microstructure and chemical composition of the anodic oxide layer was analyzed using transmission and scanning electron microscopy as well as x-ray photoelectron spectroscopy. Schottky emission at the SWCNT-AAO and AAO-Al interfaces allowed by impurity states in the anodic aluminum oxide film together with ionic surface conduction on the pore walls of AAO gives a reasonable explanation for the measured electrical conduction. Calcined AAO is proposed as a dielectric material for SWCNT-field effect transistors.
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| 11. |
- Kukkola, Jarmo, et al.
(författare)
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Gas sensors based on anodic tungsten oxide
- 2011
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier B V. - 0925-4005 .- 1873-3077. ; 153:2, s. 293-300
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured porous tungsten oxide materials were synthesized by the means of electrochemical etching (anodization) of tungsten foils in aqueous NaF electrolyte. Formation of the sub-micrometer size mesoporous particles has been achieved by infiltrating the pores with water. The obtained colloidal anodic tungsten oxide dispersions have been used to fabricate resistive WO3 gas sensors by drop casting the sub-micrometer size mesoporous particles between Pt electrodes on Si/SiO2 substrate followed by calcination at 400 °C in air for 2 h. The synthesized WO3 films show slightly nonlinear current–voltage characteristics with strong thermally activated carrier transport behavior measured at temperatures between −20 °C and 280 °C. Gas response measurements carried out in CO, H2, NO and O2 analytes (concentration from 1 to 640 ppm) in air as well as in Ar buffers (O2 only in Ar) exhibited a rapid change of sensor conductance for each gas and showed pronounced response towards H2 and NO in Ar and air, respectively. The response of the sensors was dependent on temperature and yielded highest values between 170 °C and 220 °C.
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| 12. |
- Kukkola, Jarmo, et al.
(författare)
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Inkjet-printed gas sensors : metal decorated WO3 nanoparticles and their gas sensing properties
- 2012
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 22:34, s. 17878-17886
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Tidskriftsartikel (refereegranskat)abstract
- Inkjet deposition is an attractive technology to localize nanomaterials in an area-selective manner on virtually any kind of surfaces. Great advantages of the method are effective usage of materials, low processing temperatures and few required manufacturing steps, thus enabling rapid prototyping and bulk production with reasonably low cost. A number of different electrical devices such as light emitting diodes, transistors and solar cells have already been demonstrated, reflecting the versatility of inkjet printing. In this paper, we collect the contemporary results on inkjet deposited gas sensors and show examples of such gas sensing devices based on surface modified WO3 nanoparticles for efficient discrimination of various gaseous analytes from sub-ppm up to nearly 0.1% concentration levels in air.
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| 13. |
- Lin, Jhih-Fong, et al.
(författare)
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Trifluoroacetylazobenzene for optical and electrochemical detection of amines
- 2015
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 3:8, s. 4687-4694
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we demonstrate the solution processing of optical and electrochemical dye sensors based on 4-(dioctylamino)-4'-(trifluoroacetyl) azobenzene and its application in sensing different amine compounds. Distinct optical response of the sensors exposed to ammonia, tetramethylammonium hydroxide, ethylamine, cadaverine and putrescine (typical compounds upon the decomposition of proteins) is observed. Incorporation of inkjet deposited thin films of the dye as sensors in food packages of ground meat and salmon is found as a feasible route to detect the appearance of biogenic amines produced by the degrading food products. Furthermore, we demonstrate an electrochemical amine sensor based on (trifluoroacetyl) azobenzene dye added in carbon nanotube-Nafion (R) composites. The electrochemical sensor exploits the reaction between the dye and amines to detect amines in electrolytes, while the carbon nanotubes provide large surface for adsorption and also provide a percolating electrical network for allowing efficient charge transfer at the electrode electrolyte interface.
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| 14. |
- Mäklin, Jani, et al.
(författare)
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Thermal diffusivity of aligned multi-walled carbon nanotubes measured by the flash method
- 2011
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Ingår i: Physica status solidi. B, Basic research. - : John Wiley & Sons. - 0370-1972 .- 1521-3951. ; 248:11, s. 2508-2511
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Tidskriftsartikel (refereegranskat)abstract
- Thermal diffusivity of freestanding catalytic chemical vapor deposition (CCVD) grown multi-walled carbon nanotube (MWCNT) forests (height of 1.5 and 1.9 mm) was characterized in the temperature range between 25 and 200 degrees C. Copper and Al-alloy metal blocks were used as references for validation of the experimental setup. The measurements were carried out along the MWCNT alignment direction with a thermal property analyzer that uses the flash method. The thermal diffusivities measured at room temperature for as-grown and post-annealed (2 h at 480 degrees C in open air) samples were found to be similar to 0.45 and similar to 0.23 cm(2)/s, respectively. In both cases, the thermal diffusivity values were slightly decreasing with increasing temperature. The observed decrease in diffusivity after annealing is most probably due to the loss of amorphous carbon in the specimens and also because of the increased defect density in the nanotube walls resulting in a more pronounced phonon scattering in the lattice. The measured thermal diffusivities for as-grown samples agree with data reported elsewhere for similar MWCNT materials [W. Yi et al., Rev. B 59, 9015 (1999) and T. Borca-Tasciuc et al., J. Appl. Phys. 98, 054309 (2005)]. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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| 15. |
- Ngoc Pham, Tung, et al.
(författare)
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Industrially benign super-compressible piezoresistive carbon foams with predefined wetting properties : from environmental to electrical applications
- 2014
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- In the present work electrically conductive, flexible, lightweight carbon sponge materials derived from open-pore structure melamine foams are studied and explored. Hydrophobic and hydrophilic surface properties - depending on the chosen treatment conditions - allow the separation and storage of liquid chemical compounds. Activation of the carbonaceous structures substantially increases the specific surface area from ,4 m2 g21 to ,345 m2 g21 , while retaining the original three-dimensional, open-pore structure suitable for hosting, for example, Ni catalyst nanoparticles. In turn the structure is rendered suitable for hydrogenating acetone to 2-propanol and methyl isobutyl ketone as well for growing hierarchical carbon nanotube structures used as electric double-layer capacitor electrodes with specific capacitance of ,40 F/g. Mechanical stress-strain analysis indicates the materials are super-compressible (.70% volume reduction) and viscoelastic with excellent damping behavior (loss of 0.69 6 0.07), while piezoresistive measurements show very high gauge factors (from ,20 to 50) over a large range of deformations. The cost-effective, robust and scalable synthesis - in conjunction with their fascinating multifunctional utility - makes the demonstrated carbon foams remarkable competitors with other three-dimensional carbon materials typically based on pyrolyzed biopolymers or on covalently bonded graphene and carbon nanotube frameworks.
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| 16. |
- Toth, Geza, et al.
(författare)
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Thermal management of micro hotspots in electric components with carbon nanotubes
- 2013
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Ingår i: International Journal of Nanotechnology. - : InderScience Publishers. - 1475-7435 .- 1741-8151. ; 10:1-2, s. 57-62
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Tidskriftsartikel (refereegranskat)abstract
- The excellent thermal and electrical conductivity as well as the remarkable mechanical properties of Carbon Nanotubes (CNTs) all point towards an unbeatable and facile route towards replacing traditional thermal management materials, like copper, in the electronics industry. In spite of that, the technology is still suffering from considerable challenges. In order to realise an actual electronics, which uses CNTs for thermal management, inevitable trade-offs have to be made. Our work is focusing on proposing novel ideas and manufacturing techniques which show a reasonable potential and could justify the practicality of this technology. The paper is reporting on the recent results in hotspot removal by using tailored multi-layer chips and CNTs grown directly on the heat affected zone.
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| 17. |
- Toth, Geza, et al.
(författare)
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Towards fully printed, antenna-based proximity sensors
- 2012
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Ingår i: Zhongguó wùli xuékan. - 0577-9073. ; 50:6, s. 910-918
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we describe proximity sensors using functional coatings as sensing elements. The planar inductor-capacitor resonant circuit is fabricated by conventional PCB fabrication techniques and also by using low cost drop-on-demand inkjet printing technology. The permittivity and conductivity is changing in the system as a function of humidity, which simulates the presence of a body. This change in turn modifies the resonant frequency of the sensor. The performance of the fabricated proximity sensors are good, especially using the PCB resonant circuit and the gypsum / sodium-hydrogen titanate nanowire composites as sensitizing elements.
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| 18. |
- Virtanen, Pasi, et al.
(författare)
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Towards one-pot synthesis of menthols from citral : Modifying Supported Ionic Liquid Catalysts (SILCAs) with Lewis and Brønsted acids
- 2009
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Ingår i: Journal of Catalysis. - : Elsevier Inc. - 0021-9517. ; 263:2, s. 209-19
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Tidskriftsartikel (refereegranskat)abstract
- The use of ionic liquids in catalysis is attracting ever more attention in chemical engineering. In line with this research we have studied Supported Ionic Liquid Catalysts (SILCAs) which consist of immobilized catalytic species, e.g. transition metal particles residing in an ionic liquid layer immobilized on a solid support. We found out that dissolution of Lewis or Brønsted acids into the ionic liquid layer of SILCA has major effects to the activity as well as the product distribution of the catalyst in citral transformation reactions. In fact, one-pot synthesis of menthols from citral was accomplished. The effects of different amounts of added Lewis and/or Brønsted acids to SILCA (one of them or both) were studied in this work. Graphical abstract Supported Ionic Liquid Catalyst (SILCA) was modified with different Lewis and Brønsted acids and the effects of different acids to the catalyst activity and product selectivity in a reaction of menthols from citral was evaluated. Full-size image (20K)High-quality image (101K)
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| 19. |
- Wu, Ming-Chung, et al.
(författare)
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Nitrogen-doped anatase nanofibers decorated with noble metal nanoparticles for photocatalytic production of hydrogen
- 2011
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Ingår i: ACS NANO. - : American Chemical Society. - 1936-0851 .- 1936-086X. ; 5:6, s. 5025-5030
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Tidskriftsartikel (refereegranskat)abstract
- We report the synthesis of N-doped TiO2 nanofibers and high photocatalytic efficiency in generating hydrogen from ethanol-water mixtures under UV-A and UV-B irradiation. Titanate nanofibers synthesized by hydrothermal method are annealed in air and/or ammonia to achieve N-doped anatase fibers. Depending on the synthesis route, either interstitial N atoms or new N-Ti bonds appear in the lattice resulting in slight lattice expansion as shown by XPS and HR-TEM analyses, respectively. These nanofibers were then used as support for Pd and Pt nanoparticles deposited with wet impregnation followed by calcination and reduction. In the hydrogen generation tests the N-doped samples were clearly outperforming their un-doped counterparts showing remarkable efficiency not only under UV-B but also with UV-A illumination. Applying 100 mg catalyst (N-doped TiO2 nanofiber decorated with Pt nanoparticles) in 1 L water-ethanol mixture the H2 evolution rates were as high as 700 μmol/h (UV-A) and 2250 μmol/h (UV-B) corresponding to photo energy percentages of ~3.6% and ~12.3%, respectively.
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| 20. |
- Wu, Ming-Chung, et al.
(författare)
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Photo-Kelvin probe force microscopy for photocatalytic performance characterization of single filament of TiO2 nanofiber photocatalysts
- 2013
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 1:18, s. 5715-5720
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Tidskriftsartikel (refereegranskat)abstract
- This is an in-depth study on the photocatalytic performance characterization for single filament of TiO2 nanofiber photocatalysts by the novel photo-Kelvin probe force microscopy technique (photo-KPFM) and first principles calculations. Three kinds of TiO2 nanofibers: anatase TiO2 nanofibers (anatase TiO2 NFs), nitrogen doped TiO2 nanofibers (N-TiO2 NFs), and nitrogen doped TiO2 nanofibers decorated with platinum nanoparticles (N-TiO2-Pt NFs) were investigated. The N-TiO2-Pt NFs exhibit the largest negative photo surface potential shift (-182 mV) as compared to anatase TiO2 NFs (-29 mV). The first-principles calculations based on density functional theory (CASTEP simulation software) indicate that the significant photo surface potential shift obtained by adding nitrogen and platinum into TiO2 NFs is induced by two mechanisms: (1) enhancement in absorbance to increase exciton generation and (2) decreased charge recombination to increase surface charge. These changes in the photo surface potential of various TiO2 nanofibers are closely correlated with their photocatalytic activity. Thus, this novel photo-KPFM provides a useful technique to easily monitor the photocatalytic capability of materials in the development of high performance photocatalysts.
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| 21. |
- Wu, Ming-Chung, et al.
(författare)
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Photocatalytic activity of nitrogen-doped TiO2-based nanowires : a photo-assisted Kelvin probe force microscopy study
- 2013
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Ingår i: Journal of nanoparticle research. - : Springer. - 1388-0764 .- 1572-896X. ; 16:1, s. Article Number: UNSP 2143-
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a set of nitrogen-doped TiO2-based nanomaterials demonstrating photocatalytic activity was developed by combining the efforts of lattice doping and metal nanoparticle decoration and tested for photo-degradation of methylene blue dye by applying solar simulator irradiation. The surface potential shifts of these TiO2-based photocatalytic nanomaterials measured by Kelvin probe force microscope have been used to study the degree of electron generation of the photocatalysts after irradiation and were well correlated with the photocatalytic activity. The nitrogen-doped TiO2 nanowires decorated with Pt nanoparticles can induce obvious electron accumulation and result in a large shift of surface potential. The analysis shows a clear correlation between the surface potential shift and the photodegradation activity. Furthermore, a thorough comparative photocatalytic activity study combined with X-ray photoelectron spectroscopy analysis of the materials-doped with nitrogen under various conditions-reveals that the photocatalytic efficiency of the catalysts is maintained even if the lattice doping is leached e.g., by thermal treatments after doping. By monitoring the surface potential shifts of various TiO2-based photocatalysts by photo-assisted Kelvin probe force microscopy, we obtain a useful tool for developing novel materials with high photocatalytic activity.
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| 22. |
- Wu, Ming-Chung, et al.
(författare)
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Synthesis and Photocatalytic Performance of Titanium Dioxide Nanofibers and the Fabrication of Flexible Composite Films from Nanofibers
- 2012
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Ingår i: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 12:2, s. 1421-1424
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Tidskriftsartikel (refereegranskat)abstract
- Titanium dioxide nanofibers were synthesized and applied in flexible composite films that are easy to handle and recycle after use. The nanofibers were obtained in a multi-step procedure. First, sodium titanate nanofibers were prepared from TiO2 nanoparticles through the alkali hydrothermal method. In the next step, sodium hydrogen titanate nanofibers were made by washing the sodium titanate nanofibers in HCI solution. Finally, the sodium hydrogen titanate nanofibers were transformed to TiO2 anatase nanofibers by calcination in air. The photocatalytic activity of TiO2 anatase nanofibers were evaluated and compared to a TiO2 nanoparticle catalyst by decomposing methyl orange dye in aqueous solutions. The achieved reaction rate constant of TiO2 anatase nanofibers was comparable to that of Degussa P25. Paper-like flexible composite films were prepared by co-filtrating aqueous dispersions of TiO2 catalyst materials and cellulose. The composite films made from the nanofibers exhibit better mechanical integrity than those of the nanoparticle-cellulose composites.
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