| 1. |
- Kanai, M, et al.
(author)
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- 2023
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swepub:Mat__t
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| 2. |
- Niemi, MEK, et al.
(author)
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- 2021
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swepub:Mat__t
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| 3. |
- Baruah, S., et al.
(author)
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Photoreactivity of ZnO nanoparticles in visible light : Effect of surface states on electron transfer reaction
- 2009
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In: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 105:7
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Journal article (peer-reviewed)abstract
- Wide band gap metal oxide semiconductors such as zinc oxide (ZnO) show visible band photolysis that has been employed, among others, to degrade harmful organic contaminants into harmless mineral acids. Metal oxides show enhanced photocatalytic activity with the increase in electronic defects in the crystallites. By introducing defects into the crystal lattice of ZnO nanoparticles, we observe a redshift in the optical absorption shifting from the ultraviolet region to the visible region (400-700 nm), which is due to the creation of intermediate defect states that inhibit the electron hole recombination process. The defects were introduced by fast nucleation and growth of the nanoparticles by rapid heating using microwave irradiation and subsequent quenching during the precipitation reaction. To elucidate the nature of the photodegradation process, picosecond resolved time correlated single photon count (TCSPC) spectroscopy was carried out to record the electronic transitions resulting from the de-excitation of the electrons to their stable states. Photodegradation and TCSPC studies showed that defect engineered ZnO nanoparticles obtained through fast crystallization during growth lead to a faster initial degradation rate of methylene blue as compared to the conventionally synthesized nanoparticles.
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| 4. |
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| 5. |
- Makhal, A., et al.
(author)
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Role of resonance energy transfer in light harvesting of zinc oxide-based dye-sensitized solar cells
- 2010
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:23, s. 10390-10395
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Journal article (peer-reviewed)abstract
- In this contribution we have studied the dynamics of light harvesting of ZnO nanoparticles (NPs) to a surface adsorbed sensitizing dye (SD) N719. By using the picosecond resolved Forster resonance energy transfer (FRET) technique we have explored that the excited ZnO NPs resonantly transfer visible optical radiation to the SD N719. The consequence of the energy transfer on the performance of the overall efficiency of a model ZnO NP-based dye-sensitized solar cell (DSSC) has also been explored. We have demonstrated that the overall efficiency of a ZnO NP-based solar cell significantly depends on the presence of high-energy photons in the solar radiation. In a control experiment on a model TiO2 NP-based solar cell it has been demonstrated that the presence of high-energy photon has a minimal effect on the performance of the cell as the TiO2 NPs are incapable of harvesting high-energy photons from solar radiation. The possibility of the back electron transfer from the excited NPs to the SD has also been investigated by studying the NPs in the presence of an ideal electron accepting organic molecule, benzoquinone (BQ). The time constants and nonradiative rate constant obtained for the ZnO/N719 system are found to be different from those of the ZnO/BQ system, which rules out the possibility of back electron transfer from ZnO NPs to SD N719. Moreover, the observed FRET dynamics in the light harvesting process of the nanocrystalites may be efficient in the further use of the nanoparticles in the development of new photodevices.
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| 6. |
- Baruah, S., et al.
(author)
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Nanostructured zinc oxide for water treatment
- 2012
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In: Nanoscience and Nanotechnology - Asia. - : Bentham Science Publishers. - 2210-6812. ; 2:2, s. 90-102
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Journal article (peer-reviewed)abstract
- Environmental pollution and industrialization on a global scale have drawn attention to the vital need for developing new hygienically friendly purification technologies. Existing wastewater treatment technologies demand high capital investment and operation & maintenance cost, and large area. Cost-effective treatment of pollutants requires the transformation of hazardous substances into benign forms and the subsequent development of effective risk management strategies from harmful effects of pollutants that are highly toxic, persistent, and difficult to treat. Application of nanotechnology that results in improved water treatment options might include removal of the finest contaminants from water (< 300 nm) and "smart materials" or "reactive surface coatings" with engineered specificity to a certain pollutant that destroy, transform or immobilize toxic compounds. Nanomaterials have been gaining increasing interest in the area of environmental remediation mainly due to their enhanced surface and also other specific changes in their physical, chemical and biological properties that develop due to size effects. Heterogeneous photocatalytic systems via metal oxide semiconductors like TiO2 and ZnO, are capable of operating effectively and efficiently for waste water treatment which has been discussed along with other nanotechnology routes that can be useful for water treatments. Multifunctional photocatalytic membranes using ZnO nanostructures are considered advantageous over freely suspended nanoparticles due to the ease of its removal from the purified water. A short discussion on the study of charge transfer mechanisms during photocatalytic reactions has also been included.
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| 7. |
- Björkman, Anne, 1981, et al.
(author)
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Tundra Trait Team: A database of plant traits spanning the tundra biome
- 2018
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In: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 27:12, s. 1402-1411
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Journal article (peer-reviewed)abstract
- © 2018 The Authors Global Ecology and Biogeography Published by John Wiley & Sons Ltd Motivation: The Tundra Trait Team (TTT) database includes field-based measurements of key traits related to plant form and function at multiple sites across the tundra biome. This dataset can be used to address theoretical questions about plant strategy and trade-offs, trait–environment relationships and environmental filtering, and trait variation across spatial scales, to validate satellite data, and to inform Earth system model parameters. Main types of variable contained: The database contains 91,970 measurements of 18 plant traits. The most frequently measured traits (>1,000 observations each) include plant height, leaf area, specific leaf area, leaf fresh and dry mass, leaf dry matter content, leaf nitrogen, carbon and phosphorus content, leaf C:N and N:P, seed mass, and stem specific density. Spatial location and grain: Measurements were collected in tundra habitats in both the Northern and Southern Hemispheres, including Arctic sites in Alaska, Canada, Greenland, Fennoscandia and Siberia, alpine sites in the European Alps, Colorado Rockies, Caucasus, Ural Mountains, Pyrenees, Australian Alps, and Central Otago Mountains (New Zealand), and sub-Antarctic Marion Island. More than 99% of observations are georeferenced. Time period and grain: All data were collected between 1964 and 2018. A small number of sites have repeated trait measurements at two or more time periods. Major taxa and level of measurement: Trait measurements were made on 978 terrestrial vascular plant species growing in tundra habitats. Most observations are on individuals (86%), while the remainder represent plot or site means or maximums per species. Software format: csv file and GitHub repository with data cleaning scripts in R; contribution to TRY plant trait database (www.try-db.org) to be included in the next version release.
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| 8. |
- Baruah, S., et al.
(author)
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Effect of seeded substrates on hydrothermally grown ZnO nanorods
- 2009
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In: Journal of Sol-Gel Science and Technology. - : Springer Berlin/Heidelberg. - 0928-0707 .- 1573-4846. ; 50:3, s. 456-464
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Journal article (peer-reviewed)abstract
- We report a study on the effect of seeding on glass substrates with zinc oxide nanocrystallites towards the hydrothermal growth of ZnO nanorods from a zinc nitrate hexahydrate and hexamethylenetetramine solution at 95 °C. The seeding was done with pre-synthesized ZnO nanoparticles in isopropanol with diameters of about 6–7 nm as well as the direct growth of ZnO nanocrystallites on the substrates by the hydrolysis of pre-deposited zinc acetate film. The nanorods grown on ZnO nanoparticle seeds show uniform dimensions throughout the substrate but were not homogenously aligned vertically from the substrate and appeared like nanoflowers with nanorod petals. Nanorods grown from the crystallites formed in situ on the substrates displayed wide variations in dimension depending upon the preheating and annealing conditions. Annealing the seed crystals below 350 °C led to scattered growth directions whereupon preferential orientation of the nanorods perpendicular to the substrates was observed. High surface to volume ratio which is vital for gas sensing applications can be achieved by this simple hydrothermal growth of nanorods and the rod height and rod morphology can be controlled through the growth parameters.
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| 9. |
- Baruah, S., et al.
(author)
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Growth of ZnO nanowires on nonwoven polyethylene fibers
- 2008
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In: Science and Technology of Advanced Materials. - : Taylor & Francis. - 1468-6996 .- 1878-5514. ; 9:2
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Journal article (peer-reviewed)abstract
- We report the growth of ZnO nanowires on nonwoven polyethylene fibers using a simple hydrothermal method at a temperature below the boiling point of water. The ZnO nanowires were grown from seed ZnO nanoparticles affixed onto the fibers. The seed ZnO nanoparticles, with diameters of about 6-7 nm, were synthesized in isopropanol by reducing zinc acetate hydrate with sodium hydroxide. The growth process was carried out in a sealed chemical bath containing an equimolar solution of zinc nitrate hexahydrate and hexamethylene tetramine at a temperature of 95°C over a period of up to 20 h. The thickness and length of the nanowires can be controlled by using different concentrations of the starting reactants and growth durations. A 0.5 mM chemical bath yielded nanowires with an average diameter of around 50 nm, while a 25 mM bath resulted in wires with a thickness of up to about 1 μm. The length of the wires depends both on the concentration of the precursor solution as well as the growth duration, and in 20 h, nanowires as long as 10 μm can be grown. The nonwoven mesh of polyethylene fibers covered with ZnO nanowires can be used for novel applications such as water treatment by degrading pollutants by photocatalysis. Photocatalysis tests carried out on standard test contaminants revealed that the polyethylene fibers with ZnO nanowires grown on them could accelerate the photocatalytic degradation process by a factor of 3.
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| 10. |
- Baruah, S., et al.
(author)
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Hydrothermal growth of ZnO nanostructures
- 2009
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In: Science and Technology of Advanced Materials. - : 2009 National Institute for Materials Science. - 1468-6996 .- 1878-5514. ; 10:1
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Journal article (peer-reviewed)abstract
- One-dimensional nanostructures exhibit interesting electronic and optical properties due to their low dimensionality leading to quantum confinement effects. ZnO has received lot of attention as a nanostructured material because of unique properties rendering it suitable for various applications. Amongst the different methods of synthesis of ZnO nanostructures, the hydrothermal method is attractive for its simplicity and environment friendly conditions. This review summarizes the conditions leading to the growth of different ZnO nanostructures using hydrothermal technique. Doping of ZnO nanostructures through hydrothermal method are also highlighted.
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