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  • 1. Baruah, S.
    et al.
    Dutta, J.
    Centre of Excellence in Nanotechnology, Asian Institute of Technology,Thailand.
    Hydrothermal growth of ZnO nanostructures2009In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 10, no 1Article in journal (Refereed)
    Abstract [en]

    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.

  • 2. Baruah, S.
    et al.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Zinc stannate nanostructures: Hydrothermal synthesis2011In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 12, no 1Article in journal (Refereed)
    Abstract [en]

    Nanostructured binary semiconducting metal oxides have received much attention in the last decade owing to their unique properties rendering them suitable for a wide range of applications. In the quest to further improve the physical and chemical properties, an interest in ternary complex oxides has become noticeable in recent times. Zinc stannate or zinc tin oxide (ZTO) is a class of ternary oxides that are known for their stable properties under extreme conditions, higher electron mobility compared to its binary counterparts and other interesting optical properties. The material is thus ideal for applications from solar cells and sensors to photocatalysts. Among the different methods of synthesizing ZTO nanostructures, the hydrothermal method is an attractive green process that is carried out at low temperatures. In this review, we summarize the conditions leading to the growth of different ZTO nanostructures using the hydrothermal method and delve into a few of its applications reported in the literature.

  • 3. Baruah, S.
    et al.
    Jaisai, M.
    Imani, R.
    Nazhad, M. M.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Photocatalytic paper using zinc oxide nanorods2010In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 11, no 5Article in journal (Refereed)
    Abstract [en]

    Zinc oxide (ZnO) nanorods were grown on a paper support prepared from soft wood pulp. The photocatalytic activity of a sheet of paper with ZnO nanorods embedded in its porous matrix has been studied. ZnO nanorods were firmly attached to cellulose fibers and the photocatalytic paper samples were reused several times with nominal decrease in efficiency. Photodegradation of up to 93% was observed for methylene blue in the presence of paper filled with ZnO nanorods upon irradiation with visible light at 963 Wm–2 for 120 min. Under similar conditions, photodegradation of approximately 35% was observed for methyl orange. Antibacterial tests revealed that the photocatalytic paper inhibits the growth of Escherichia coli under room lighting conditions.

  • 4. Baruah, S.
    et al.
    Thanachayanont, C.
    Dutta, Joydeep
    Asian Institute of Technology, School of Engineering and Technology, Thailand.
    Growth of ZnO nanowires on nonwoven polyethylene fibers2008In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 9, no 2Article in journal (Refereed)
    Abstract [en]

    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.

  • 5. Charinpanitkul, T.
    et al.
    Chanagul, A.
    Dutta, Joydeep
    School of Advanced Technologies, Asian Institute of Technology,Thailand.
    Rungsardthong, U.
    Tanthapanichakoon, W.
    Effects of cosurfactant on ZnS nanoparticle synthesis in microemulsion2005In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 6, no 3-4 SPEC. ISS., p. 266-271Article in journal (Refereed)
    Abstract [en]

    ZnS nanoparticles with different morphology; spherical, ellipsoidal particles' nanotubes and nanorods, could be successfully synthesized from quaternary W/O microemulsion system. The morphology of the final products could be clearly confirmed by the scanning electron microscopy (SEM) and the transmission electron microscopy (TEM). The effect of cosurfactant on size and morphology of the obtained products have been explored in this work. The key controlling parameters such as the molar ratio of water to surfactant (wo) and the reactant concentration, which affect the product characteristics, have also been investigated.

  • 6. Panigrahi, Puspamitra
    et al.
    Araujo, C. Moyses
    Hussen, Tanveer
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University.
    Crafting ferromagnetism in Mn-doped MgO surfaces with p-type defects2014In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 15, no 3, p. 035008-Article in journal (Refereed)
    Abstract [en]

    We have employed first-principles calculations based on density functional theory (DFT) to investigate the underlying physics of unusual magnetism in Mn-doped MgO surface. We have studied two distinct scenarios. In the first one, two Mn atoms are substitutionally added to the surface, occupying the Mg sites. Both are stabilized in the Mn3+ valence state carrying a local moment of 4.3 mu(B) having a high-spin configuration. The magnetic interaction between the local moments display a very short-ranged characteristic, decaying very quickly with distance, and having antiferromagnetic ordering lower in energy. The energetics analysis also indicates that the Mn ions prefer to stay close to each other with an oxygen atom bridging the local interaction. In the second scenario, we started exploring the effect of native defects on the magnetism by crafting both Mg and O vacancies, which are p-and n-type defects, respectively. It is found that the electrons and holes affect the magnetic interaction between Mn ions in a totally different manner. The n-type defect leads to very similar magnetism, with the AFM configuration being energetically preferred. However, in the presence of Mg vacancy, the situation is quite different. The Mn atoms are further oxidized, giving rise to mixed Mn(d) ionic states. As a consequence, the Mn atoms couple ferromagnetically, when placed in the close configuration, and the obtained electronic structure is coherent with the double-exchange type of magnetic interaction. To guarantee the robustness of our results, we have benchmarked our calculations with three distinct theory levels, namely DFT-GGA, DFT-GGA+U and DFT-hybrid functionals. On the surface, the Mg vacancy displays lower formation energy occurring at higher concentrations. Therefore, our model systems can be the basis to explain a number of controversial results regarding transition metal doped oxides.

  • 7. Pummakarnchana, O.
    et al.
    Tripathi, N.
    Dutta, Joydeep
    School of Advanced Technologies, Asian Institute of Technology, Thailand.
    Air pollution monitoring and GIS modeling: A new use of nanotechnology based solid state gas sensors2005In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 6, no 3-4 SPEC. ISS., p. 251-255Article in journal (Refereed)
    Abstract [en]

    Air pollution is a serious problem in thickly populated and industrialized areas in Thailand, especially in Bangkok. The air pollution in Bangkok is abundant, especially in areas where pollution sources and the human population are concentrated. Economic growth and industrialization are proceeding at a rapid pace, accompanied by increasing emissions of air polluting sources. Furthermore, though the variety and quantities of polluting sources have increased dramatically, the development of a suitable method for monitoring the pollution causing sources has not followed at the same pace. Environmental impacts of air pollutants have impact on public health, vegetation, material deterioration etc. To prevent or minimize the damage caused by atmospheric pollution, suitable monitoring systems are urgently needed that can rapidly and reliably detect and quantify polluting sources for monitoring by regulating authorities in order to prevent further deterioration of the current pollution levels. Consequently, it is important that the current real-time air quality monitoring system, controlled by the Pollution Control Department (PCD), should be adapted or extended to aid in alleviating this problem. Nanotechnology has been applied to several industrial and domestic fields, for example, applications for gas monitoring systems, gas leak detectors in factories, fire and toxic gas detectors, ventilation control, breath alcohol detectors, and the like. Here we report an application example of studying air quality monitoring based on nanotechnology 'solid state gas sensors'. So as to carry out air pollution monitoring over an extensive area, a combination of ground measurements through inexpensive sensors and wireless GIS will be used for this purpose. This portable device, comprising solid state gas sensors integrated to a Personal Digital Assistant (PDA) linked through Bluetooth communication tools and Global Positioning System (GPS), will allow rapid dissemination of information on pollution levels at multiple sites simultaneously. The AQ report generated can be then published using Internet GIS to provide a real-time information service for the PCD, for increased public awareness and enhanced public participation. The local deterministic and geostatistical interpolation methods have been used for spatial prediction, and to find out the most suitable method for studying air pollution, based on observations at each monitoring site.

  • 8. Sugunan, A.
    et al.
    Thanachayanont, C.
    Dutta, Joydeep
    School of Advanced Technologies, Asian Institute of Technology, Thailand.
    Hilborn, J. G.
    Heavy-metal ion sensors using chitosan-capped gold nanoparticles2005In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 6, no 3-4 SPEC. ISS., p. 335-340Article in journal (Refereed)
    Abstract [en]

    We report a novel strategy for using gold nanoparticles capped with chitosan for sensing ions of heavy metals. Acidic anions (glutamate ions in our case) are expected to cap the nanoparticle surfaces similar to conventional methods of stabilization of gold nanoparticles by citrate ions. The polycationic nature of chitosan enables attachment of the polymer to the negatively charged gold nanoparticle surfaces through electrostatic interactions. Use of chitosan serves dual purpose of providing sufficient steric hindrance ensuring stability of the colloid and also to functionalize the nanoparticles for use as sensors. The well-documented chelating properties of chitosan and the sensitivity of the optical properties of gold nanoparticles to agglomeration have been employed to detect low concentrations of heavy metals ions (Zn2+ and Cu2+) in water. A comparison of the optical absorption spectra of the colloidal suspension before and after exposure to metal ions is a good indicator of the concentration of the heavy metal ions.

  • 9. Warad, H. C.
    et al.
    Ghosh, S. C.
    Hemtanon, B.
    Thanachayanont, C.
    Dutta, J.
    School of Advanced Technologies, Asian Institute of Technology,Thailand.
    Luminescent nanoparticles of Mn doped ZnS passivated with sodium hexametaphosphate2005In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 6, no 3-4 SPEC. ISS., p. 296-301Article in journal (Refereed)
    Abstract [en]

    We report the synthesis of luminescent nanoparticles of manganese doped zinc sulfide (ZnS:Mn2+) with an emission peak at around 590 nm. Nanoparticles of ZnS:Mn2+ are prepared by a co-precipitation reaction from homogenous solutions of zinc and manganese salts. Based on Ostwald ripening and surface passivation, we discuss a mechanism for the formation of ZnS:Mn2+ nanoparticles. The reaction proceeds with the nucleation of ZnS crystals, which are immediately passivated by the anions in the solution. This in turn attracts cations including zinc and manganese which contribute to the growth of the crystal. These nanoparticles are sterically stabilized using polyphosphates of sodium namely sodium tripolyphosphate (STTP) and sodium hexametaphosphate (SHMP). The nanoparticles consist of particles of 60-80 nm in diameter, each containing primary crystallites that was estimated from the X-ray diffraction patterns to be at around 2.2 nm

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