| 1. |
- Baruah, S., et al.
(författare)
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Photoreactivity of ZnO nanoparticles in visible light : Effect of surface states on electron transfer reaction
- 2009
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 105:7
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Giri, Anupam, et al.
(författare)
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Rational surface modification of Mn3O4 nanoparticles to induce multiple photoluminescence and room temperature ferromagnetism
- 2013
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 1:9, s. 1885-1895
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Tidskriftsartikel (refereegranskat)abstract
- Surface modification can have a significant influence on the materials behavior at the nanoscale and can lead to nanostructures with novel properties. Here, we demonstrate the surface modification induced multiple photoluminescence and room temperature ferromagnetic activation of Mn3O4 nanoparticles (NPs). Employing a systematic variation of the ligands, their functional groups and the structural position of the functional groups, we have identified the necessary and sufficient structural requirements of the surface co-ordinating ligands, in order to induce unprecedented optical/magnetic responses from the NPs. Using a multitude of spectroscopic techniques, we have investigated the mechanism behind the emergence of the multiple photoluminescence (PL), and it is revealed that the presence of a α-hydroxy carboxylate moiety in the ligands is necessary to activate the Jahn-Teller (J-T) splitting of Mn3+ ions on the NP surface and the corresponding d-d transitions along with the ligand-to-metal charge transfer transitions (LMCT, associated with Mn2+/3+-ligand interactions) is the key factor. However, the presence of a carboxylate group on the surface coordinating ligands is sufficient to activate the room temperature ferromagnetism of the NPs. Moreover, it has been observed that the ligands that induced the smallest crystal field splitting energy (CFSE) resulted in the strongest ferromagnetic activation of the NPs. Finally, the functionalized material has been identified as an efficient catalyst for the photo-degradation of a model cationic organic dye. Apart from the fundamental scientific interest, these results represent a promising route for the rational design of Mn 3O4 NPs adaptable to diverse applications.
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| 3. |
- Hossain, M. K., et al.
(författare)
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Growth of Zinc Oxide nanowires and nanobelts for gas sensing applications
- 2005
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Ingår i: Journal of Metastable and Nanocrystalline Materials. - 1422-6375. ; 23, s. 27-30
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Tidskriftsartikel (refereegranskat)abstract
- Zinc Oxide (ZnO) is a very useful as a solid state gas sensor material. In chemical sensing the surface and interface interactions between the analyte molecules and the sensing material is all but important that is read through the changes in electrical conductance. In that sense, nano-objects with a large surface atom/bulk atom ratio, like nanoparticles and nanowires, are potentially the best chemical sensors. The mechanism envisioned involves the adsorption (and eventually diffusion) of the analyte molecule at the surface that induces a change in the electrical resistance of the nano-object. The most convenient way to measure changes in electrical resistance in such devices is to obtain the specific material as nanowires or as connected nanoparticles. Here, we will discuss about a low-temperature wet-chemical process of synthesizing ZnO nanoparticles, nanowires and nanobelts for application as gas sensors.
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| 4. |
- Johansson, Daniel, 1975, et al.
(författare)
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Multi - model analyses of the economic and energy implications for China and India in a post-Kyoto climate regime
- 2012
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a modeling comparison project on how the2°C climate target could affect economic and energy systems development in China and India. The analysis uses a framework that harmonizes baseline developments and soft-links seven national and global models being either economy wide (CGE models) or energy system models. The analysis is based on a global greenhouse gas emission pathway that aims at a radiative forcing of 2.9 W/m2 in 2100 and with a policy regime based on convergence of per capita CO2 emissions with emissions trading. Economic and energy implications for China and India vary across models. Decreased energy intensity is the most important abatement approach in the CGE models, while decreased carbon intensity is most important in the energy system models. Reliance on Coal without Carbon Capture and Storage (CCS) is significantly reduced in most models, while CCS is a central abatement technology in energy system models, as is renewable and nuclear energy. Concerning economic impacts China bears in general a higher cost than India, as China benefits less from emissions trading. Costs are also affected by changes in fossil fuel prices, currency appreciation from capital inflow from carbon trading and timing of emission reductions.
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| 5. |
- Johansson, Daniel, 1975, et al.
(författare)
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Multi-model comparison of the economic and energy implications for China and India in an international climate regime
- 2015
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Ingår i: Mitigation and Adaptation Strategies for Global Change. - : Springer Science and Business Media LLC. - 1381-2386 .- 1573-1596. ; 20:8, s. 1335-1359
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a modeling comparison on how stabilization of global climate change at about 2 °C above the pre-industrial level could affect economic and energy systems development in China and India. Seven General Equilibrium (CGE) and energy system models on either the global or national scale are soft-linked and harmonized with respect to population and economic assumptions. We simulate a climate regime, based on long-term convergence of per capita carbon dioxide (CO2) emissions, starting from the emission pledges presented in the Copenhagen Accord to the United Nations Framework Convention on Climate Change and allowing full emissions trading between countries. Under the climate regime, Indian emission allowances are allowed to grow more than the Chinese allowances, due to the per capita convergence rule and the higher population growth in India. Economic and energy implications not only differ among the two countries, but also across model types. Decreased energy intensity is the most important abatement approach in the CGE models, while decreased carbon intensity is most important in the energy system models. The reduction in carbon intensity is mostly achieved through deployment of carbon capture and storage, renewable energy sources and nuclear energy. The economic impacts are generally higher in China than in India, due to higher 2010–2050 cumulative abatement in China and the fact that India can offset more of its abatement cost though international emission trading.
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