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  • 151.
    Loiko, Pavel
    et al.
    ITMO Univ, Kronverkskiy Pr 49, St Petersburg 197101, Russia..
    Bora, Tanujjal
    Sultan Qaboos Univ, Chair Nanotechnol, Water Res Ctr, POB 17, Muscat 123, Oman.;Asian Inst Technol, Sch Engn & Technol, Nanotechnol, POB 4, Klongluang 12120, Pathumthani, Thailand..
    Serres, Josep Maria
    URV, Dept Quim Fis & Inorgan, Fis & Cristallog Mat & Nanomat FiCMA FiCNA EMaS, Campus Sescelades, Tarragona 43007, Spain..
    Yu, Haohai
    Shandong Univ, State Key Lab Crystal Mat, Jinan 250100, Shandong, Peoples R China.;Shandong Univ, Inst Crystal Mat, Jinan 250100, Shandong, Peoples R China..
    Aguio, Magdalena
    URV, Dept Quim Fis & Inorgan, Fis & Cristallog Mat & Nanomat FiCMA FiCNA EMaS, Campus Sescelades, Tarragona 43007, Spain..
    Diaz, Francesc
    URV, Dept Quim Fis & Inorgan, Fis & Cristallog Mat & Nanomat FiCMA FiCNA EMaS, Campus Sescelades, Tarragona 43007, Spain..
    Griebner, Uwe
    Max Born Inst Nonlinear Opt & Short Pulse Spect, Max Born Str 2a, D-12489 Berlin, Germany..
    Petrov, Valentin
    Max Born Inst Nonlinear Opt & Short Pulse Spect, Max Born Str 2a, D-12489 Berlin, Germany..
    Mateos, Xavier
    URV, Dept Quim Fis & Inorgan, Fis & Cristallog Mat & Nanomat FiCMA FiCNA EMaS, Campus Sescelades, Tarragona 43007, Spain..
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Oriented zinc oxide nanorods: A novel saturable absorber for lasers in the near-infrared2018In: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 9, p. 2730-2740Article in journal (Refereed)
    Abstract [en]

    Zinc oxide (ZnO) nanorods (NRs) oriented along the crystallographic [001] axis are grown by the hydrothermal method on glass substrates. The ZnO NRs exhibit a broadband (1-2 mu m) near-IR absorption ascribed to the singly charged zinc vacancy V-z(n)-1. The saturable absorption of the ZnO NRs is studied at approximate to 1 mu m under picosecond excitation, revealing a low saturation intensity, approximate to 10 kW/cm(2), and high fraction of the saturable losses. The ZnO NRs are applied as saturable absorbers in diode-pumped Yb (approximate to 1.03 mu m) and Tm (approximate to 1.94 mu m) lasers generating nanosecond pulses. The ZnO NRs grown on various optical surfaces are promising broadband saturable absorbers for nanosecond near-IR lasers in bulk and waveguide geometries.

  • 152. Mahmood, M. A.
    et al.
    Baruah, S.
    Anal, A. K.
    Dutta, Joydeep
    Asian Institute of Technology, Thailand.
    Microbial pathogen inactivation using heterogeneous photocatalysis2012In: Environmental Chemistry for a Sustainable World, Springer Berlin/Heidelberg, 2012, Vol. 2, p. 511-541Chapter in book (Other academic)
    Abstract [en]

    The concentration of toxic materials and infectious microorganism in the natural resources of drinking water is constantly increasing causing severe environmental pollution. Availability of safe drinking water to people in developing countries has become a serious challenge. The traditional chemical methods for the disinfection of drinking water have limitations due to their costs for the undeveloped nations. Furthermore, generation of harmful disinfection byproducts associated with the chemical disinfection processes like chlorination is a source of rising concern among the masses. Hence, there is an urgent need to work out some more reliable alternate techniques for the purpose. Heterogeneous photocatalysis, being considered as a promising technique to control environmental pollution has attracted the interest of researchers during the last couple of decades. The method is not only free of generation of harmful byproducts, but could also be cost effective and environmental friendly by utilizing ambient solar light. We present an overview of photocatalytic inactivation of water borne microbial pathogens. We focus here on various factors involved in the disinfection processes and discuss how different researchers have addressed them to improve the overall efficiency of photocatalytic inactivation of microbes. Research reports on the subject show that heterogeneous photocatalysis degrades wide range of microbial pathogens including bacteria, molds, fungi, and virus. Titanium dioxide (TiO2) has been found as an efficient photocatalyst to produce hydroxyl (OH) radicals under ultraviolet irradiation. The nanoparticulate photocatalyst has been observed to adsorb at the surface of the microbe and perforate the cell envelop through redox reaction leading not only to complete disintegration/mineralization of the cell. There exists an optimum catalyst loading while the inactivation rate increases with intensity of the incident light. For enhancement of the microbial inactivation efficiency under solar light, the photocatalyst has been modified in different ways which include doping and coupling with other materials, dye sensitization, and application of voltage. Suspended particles and ions have been observed to suppress the photocatalytic inactivation rate. Furthermore, water under the photocatalytic treatment has been seen to change spontaneously from basic into acidic, while, decreasing pH of suspension from 7 to 4 during the course of photocatalytic treatment increases the inactivation rate. The photocatalytic microbial inactivation has been seen to follow Langmuir-Hinshelwood kinetic model.

  • 153. Mahmood, M. A.
    et al.
    Baruah, S.
    Dutta, Joydeep
    Center of Excellence in Nanotechnology, Asian Institute of Technology, Thailand.
    Enhanced visible light photocatalysis by manganese doping or rapid crystallization with ZnO nanoparticles2011In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 130, no 1-2, p. 531-535Article in journal (Refereed)
    Abstract [en]

    In addition to their sizes and morphologies, the electronic and optical properties of ZnO nanostructures are strongly dependent on the nature and concentration of point defects generated during the crystallization process. Herein, we report synthesis of ZnO nanoparticles with high defect concentration through fast crystallization under microwave irradiation. ZnO nanocrystallites, obtained through microwave assisted hydrothermal synthesis process, exhibited higher visible light photocatalytic activity than the conventionally hydrolyzed nanoparticles as well as manganese (Mn) doped nanoparticles (ZnO:Mn(2+)). The enhancement in the photocatalytic activity was attributed to the higher defect concentration in the as-synthesized nanocrystallites which was confirmed from their optical absorption and photoluminescence spectra. Microwave assisted hydrolysis could be an effective and convenient alternate method to introduce defects in ZnO nanocrystallites which enhances visible light photocatalytic activity of ZnO nanocrystals.

  • 154. Mahmood, M. A.
    et al.
    Bora, T.
    Dutta, Joydeep
    Sultan Qaboos University, Oman.
    Studies on hydrothermally synthesised zinc oxide nanorod arrays for their enhanced visible light photocatalysis2013In: International Journal of Environmental Technology and Management, ISSN 1466-2132, E-ISSN 1741-511X, Vol. 16, no 1-2, p. 146-159Article in journal (Refereed)
    Abstract [en]

    Photocatalytic activities of hydrothermally synthesised ZnO nanorod films in synergism with visible light have been studied. Influence of each of the synthesis parameters, like concentration of precursor solution, relative concentration of hexamine and zinc nitrate, growth time, growth temperature, pre-growth seeding, post-growth annealing, concentration and pH of the contaminant suspension, and light source have been investigated. Appraisal of photocatalytic efficiencies of all the synthesised samples have been done on degradation of aqueous Methylene Blue (MB) solution under artificial/ambient light. Maximum photocatalytic activities were obtained when ZnO nanorods were synthesised with equimolar concentration of 10 mM hexamine and zinc nitrate grown for 15 hr at 90°C with post-synthesis annealing at 250°C in air. Solar irradiation was found more effective than artificial white light while the activity increased exponentially with pH value of the contaminant suspension.

  • 155. Mahmood, M. A.
    et al.
    Dutta, Joydeep
    Asian Institute of Technology, Klong Luang, Pathumthani 12120, Thailand.
    Spray pyrolized pre-coating layers for controlled growth of zinc oxide nanorods by hydrothermal process2011In: Nanoscience and Nanotechnology - Asia, ISSN 2210-6812, Vol. 1, no 2, p. 92-96Article in journal (Refereed)
    Abstract [en]

    Seeding is critical for the hydrothermal synthesis of zinc oxide (ZnO) nanorod arrays on solid substrates. Herein, spray pyrolysis is proposed as a simple and efficient technique for the deposition of ZnO seeding film on glass. The method involves the in situ formation of ZnO nanocrystals by spraying aqueous solution of zinc acetate on hot substrate (°C) whereby ZnO nanocrystallites with narrow size distribution (4-8 nm) are formed. Majority of the crystals were found to have their polar (0001) facet oriented parallel perpendicular to the substrate surface. Upon hydrothermal growth of ZnO nanorods in an equimolar solution of zinc nitrate and hexamine, it was observed that seeding by spray pyrolysis led to the formation of dense ZnO nanorod arrays that were well aligned and strongly attached to the glass substrates.

  • 156. Mahmood, Mohammad Abbas
    et al.
    Baruah, Sunandan
    Anal, Anil Kumar
    Dutta, Joydeep
    Asian Institute of Technology, Thailand .
    Heterogeneous photocatalysis for removal of microbes from water2012In: Environmental Chemistry Letters, ISSN 1610-3653, E-ISSN 1610-3661, Vol. 10, no 2, p. 145-151Article in journal (Refereed)
    Abstract [en]

    Increasing water pollution by microbes has become a source of serious health concern across the globe. Production of potentially carcinogenic disinfection by-products has marred credibility of traditional water purification techniques like chlorination. Photocatalysis has emerged as a promising alternative technique for the disinfection of water with minimal risk of harmful by-products. The process involves a wide band gap semiconductor material which, upon irradiation of light, produces electrons and holes with high redox potential to degrade organic contaminants and microbes. In this review, we analyze the research trends in photocatalytic inactivation of water borne microorganisms. This report analyzes the major factors that affect the disinfection efficiency using this process. The discussion also includes plausible mechanisms of microbial degradation as well as a kinetic model of the inactivation process. Different approaches, like doping of semiconductors or energy band engineering or plasmon coupling, have been reported for the enhancement and utilization of ambient solar light. Photocatalysis could be a cost-effective and environmentally friendly water purification technique though further research is required to enhance its efficiency with the use of solar light.

  • 157. Mahmood, Mohammad Abbas
    et al.
    Dutta, Joydeep
    Asian Institute of Technology, Thailand; Sultan Qaboos University, Oman.
    Microwave assisted hydrothermal synthesis of zinc hydroxystannate films on glass substrates2012In: Journal of Sol-Gel Science and Technology, ISSN 0928-0707, E-ISSN 1573-4846, Vol. 62, no 3, p. 495-504Article in journal (Refereed)
    Abstract [en]

    Zinc stannate (ZnSnO 3, Zn 2SnO 4) and its precursor, i.e. zinc hydroxystannate (ZnSn(OH) 6), have emerged as technological nanomaterials for different applications. Herein, we report synthesis of polycrystalline zinc hydroxystannate (ZHS) film on glass substrate through facile and efficient microwave assisted hydrothermal growth. The method comprises of three steps; deposition of ZnO seed films on glass substrates through spray pyrolysis, growth of ZnO nanorod arrays over the seeded substrates through microwave assisted hydrothermal method and transformation of the as-synthesized ZnO nanorod arrays into the ZHS films through microwave treatment in aqueous precursor solution of SnCl 4 and NaOH. The films were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction and scanning electron microscopy (SEM). The films contain two crystalline phases namely ZnO with [002] as preferred growth direction and ZnSn(OH) 6 preferably grown along [200] vector. The obtained ZHS films consist of crystals of exclusively cubic structure with sizes up to several microns. Microwave irradiation time, NaOH/SnCl 4 molar ratio, concentration of Sn 4+ ions, and the applied power are the four parameters which influence the size, aerial density and growth rate of ZHS microblocks.

  • 158. Makhal, A.
    et al.
    Sarkar, S.
    Bora, T.
    Baruah, S.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology,.
    Raychaudhuri, A. K.
    Pal, S. K.
    Role of resonance energy transfer in light harvesting of zinc oxide-based dye-sensitized solar cells2010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 23, p. 10390-10395Article in journal (Refereed)
    Abstract [en]

    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.

  • 159. Makhal, Abhinandan
    et al.
    Sarkar, Soumik
    Bora, Tanujjal
    Baruah, Sunandan
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Raychaudhuri, A K
    Pal, Samir Kumar
    Dynamics of light harvesting in ZnO nanoparticles2010In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 21, no 26, p. 265703-1Article in journal (Refereed)
    Abstract [en]

    We have explored light harvesting of the complex of ZnO nanoparticles with the biological probe Oxazine 1 in the near-infrared region using picosecond-time-resolved fluorescence decay studies. We have used ZnO nanoparticles and Oxazine 1 as a model donor and acceptor, respectively, to explore the efficacy of the Förster resonance energy transfer (FRET) in the nanoparticle–dye system. It has been shown that FRET from the states localized near the surface and those in the bulk of the ZnO nanoparticles can be resolved by measuring the resonance efficiency for various wavelengths of the emission spectrum. It has been observed that the states located near the surface for the nanoparticles (contributing to visible emission at λ≈550 nm) can contribute to very high efficiency (>90%) FRET. The efficiency of light harvesting dynamics of the ZnO nanorods has also been explored in this study and they were found to have much less efficiency (~40%) for energy transfer compared to the nanoparticles. The possibility of an electron transfer reaction has been ruled out from the picosecond-resolved fluorescence decay of the acceptor dye at the ZnO surface.

  • 160. Myint, M. T. Z.
    et al.
    Dutta, Joydeep
    Center of Excellence in Nanotechnology, Asian Institute of Technology, Thailand.
    Fabrication of zinc oxide nanorods modified activated carbon cloth electrode for desalination of brackish water using capacitive deionization approach2012In: Desalination, ISSN 0011-9164, E-ISSN 1873-4464, Vol. 305, p. 24-30Article in journal (Refereed)
    Abstract [en]

    Capacitive deionization (CDI) is a promising technique for removing dissolved ions from saline water. This method works on electrochemical control to remove ions from aqueous solution upon electrically charging the electrodes (anode and cathode). In this work, highly porous and conducting activated carbon cloth (ACC) material modified with zinc oxide (ZnO) nanorods (ACC:ZnO) was used as base substrate in a flow through capacitor configuration. Simple and low temperature hydrothermal method was used to grow ZnO nanorods on ACC surface in an aqueous media. The desalination process was conducted using 100 ppm sodium chloride (NaCl) solution with the flow rate of 2 ml/min under an applied potential of 1.2 V. Enhancement of salt removal (desalination) and regeneration efficiency of 34% and 24% were achieved respectively.

  • 161. Myint, M. T. Z.
    et al.
    Hornyak, G. L.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    One pot synthesis of opposing ’rose petal’ and ’lotus leaf’ superhydrophobic materials with zinc oxide nanorods2014In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 415, p. 32-38Article in journal (Refereed)
    Abstract [en]

    The synthesis in one pot1One-pot synthesis indicates that the two-step chemical synthesis on cloth surfaces was accomplished simultaneously for each cloth in one vessel (or one beaker).1 of opposing 'rose petal' and 'lotus leaf' superhydrophobic materials from commercially available superhydrophilic cloth substrates of varying texture is described for the first time. Surfaces of 'rough' textured cloth and 'smooth' textured cloth were simultaneously rendered superhydrophobic by growing zinc oxide (ZnO) nanorods by a hydrothermal process in the same chemical bath. Contact angle hysteresis and water pendant drop tests revealed strong water adhesion to ZnO microrod-treated rough cloth. The combination of water contact angle >150° and strong adhesion is indicative of the 'rose petal effect' with potential for water pinning. Smooth cloth with ZnO nanorods exhibited no adhesion to water droplets with facilitative roll-off. The combination of water contact angle >50° and weak to no adhesion with water is indicative of the 'lotus leaf effect' with potential for self-cleaning. Pendant water drop tests indicated cohesive failure of water on rough cloth coated with ZnO nanorods. Natural rose petals demonstrated adhesive failure between the petal surface and water droplet. A parsimonious explanation is presented. We also describe the development of superhydrophobic clothes without the need for special conditions or further chemical modification.

  • 162. Myint, M. T. Z.
    et al.
    Kitsomboonloha, R.
    Baruah, S.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Superhydrophobic surfaces using selected zinc oxide microrod growth on ink-jetted patterns2011In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 354, no 2, p. 810-815Article in journal (Refereed)
    Abstract [en]

    The synthesis and properties of superhydrophobic surfaces based on binary surface topography made of zinc oxide (ZnO) microrod-decorated micropatterns are reported. ZnO is intrinsically hydrophilic but can be utilized to create hydrophobic surfaces by creating artificial roughness via microstructuring. Micron scale patterns consisting of nanocrystalline ZnO seed particles were applied to glass substrates with a modified ink-jet printer. Microrods were then grown on the patterns by a hydrothermal process without any further chemical modification. Water contact angle (WCA). 1Water contact angle (WCA).1 up to 153° was achieved. Different micro array patterned surfaces with varying response of static contact angle or sessile droplet analysis are reported

  • 163. Myint, M. T. Z.
    et al.
    Kumar, N. S.
    Hornyak, G. L.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Hydrophobic/hydrophilic switching on zinc oxide micro-textured surface2013In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 264, p. 344-348Article in journal (Refereed)
    Abstract [en]

    Switchable wettability of zinc oxide (ZnO) microrod coated surfaces was controlled in two different ways: (1) by physical geometry (surface coverage area SA: the area covered by solid) and (2) by irradiation with ultraviolet (UV) light followed by infrared (IR) or furnace heating. In the first approach, the threshold coverage area for achieving hydrophobic surfaces was found to be <40%, which is in good agreement with predicted values in the literature leading to a metastable Cassie-Baxter regime. The transformation of hydrophobic to hydrophilic surfaces was studied by alternating cycles of 3 h exposure to ultraviolet (λpeak ∼ 253 nm) light followed by 1 h of annealing or IR irradiation alone. Three different annealing temperatures (120 °C, 200 °C and 250 °C) were utilized. Results of this work can be applied for designing surfaces with controlled wettability.

  • 164. Myint, Myo Tay Zar
    et al.
    Al-Harthi, S. H.
    Dutta, Joydeep
    Sultan Qaboos University, Oman.
    Brackish water desalination by capacitive deionization using zinc oxide micro/nanostructures grafted on activated carbon cloth electrodes2014In: Desalination, ISSN 0011-9164, E-ISSN 1873-4464, Vol. 344, p. 236-242Article in journal (Refereed)
    Abstract [en]

    The fabrication of electrodes grafted with zinc oxide (ZnO) micro/nanomaterials (nanoparticles, nanorods, microsheets and microspheres) on activated carbon cloth (ACC) for water desalination by capacitive deionization (CDI) is reported. ZnO micro/nanomaterials were hydrothermally grown on ACC and used as electrodes in a flow cell for brackish water desalination. Morphology of ZnO structures on ACC surfaces was found to affect salt removal efficiency. The desalination experiments were carried out using 100 ppm sodium chloride (NaCl) solution employing a flow rate of 2 ml/min in a parallel plate configuration with an electrode area of similar to 8.4 cm(2) under an applied potential of 1.2 V (DC). Enhanced salt removal efficiency of 22% for ZnO microsheet grafted ACC electrodes as well as ZnO nanorod grafted ACC electrodes was achieved.

  • 165. Najam Khan, M.
    et al.
    Al-Hinai, M.
    Al-Hinai, A.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Visible light photocatalysis of mixed phase zinc stannate/zinc oxide nanostructures precipitated at room temperature in aqueous media2014In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 40, no 6, p. 8743-8752Article in journal (Refereed)
    Abstract [en]

    Aqueous synthesis was used to obtain zinc stannate (ZTO) nanoparticles by precipitation at room temperature. Pourbaix diagrams were employed to formulate the precipitation reactions and synthesis process. Solution pH was controlled during the synthesis process as a major variable. The synthesized ZTO particles showed good photocatalytic activity under UV light irradiation. In order to improve visible light photocatalytic activity of ZTO nanoparticles, mixed phase zinc stannate/zinc oxide (ZnO) composites were prepared by co-precipitation at room temperature. Effects of precursor concentrations on the size and morphology of the obtained particles are reported. The composite ZTO/ZnO showed better photodegradation under visible light irradiation compared to ZTO and ZnO nanoparticles with methylene blue (MB) as a test chemical contaminant. Experiments were designed to elaborate on the active species for photocatalytic degradation of the dye and are reported here. Benzoquinone (BQ) was found to be the most effective scavenger, reducing the photodegradation considerably, indicating that O2-• plays a major role in MB degradation since 50% reduction in photocatalytic activity was observed.

  • 166. Nikkam, Nader
    et al.
    Toprak, Muhammet
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Al-Abri, Mohammed
    Myint, Myo Tay Zar
    Souayeh, Maissa
    Mohseni, Seyed Majid
    Fabrication and thermo-physical properties characterization of ethylene glycol-MoS2 heat exchange fluids2017In: International Communications in Heat and Mass Transfer, ISSN 0735-1933, E-ISSN 1879-0178, Vol. 89, p. 185-189Article in journal (Refereed)
    Abstract [en]

    This study reports on the fabrication and thermo-physical properties evaluation of ethylene glycol (EG) based heat exchange fluids containing molybdenum disulfide nanoparticles (MoS2 NPs) and micrometer sized particles (MPs). For this purpose, MoS2 NPs and MPs (with average size of 90 nm and 1.2 mu m; respectively) were dispersed and stabilized in EG with particle loading of 0.25, 0.5, 1 wt%. To study the real effect of MoS2 NP/MP the use of surfactants was avoided and ultrasonic agitation was used for dispersion and preparation of stable MoS2 NFs/MFs. The objectives were investigation of impact of MoS2 particle size (including NP/MP) and particle loading on thermo-physical properties of EG based MoS2 NFs/MFs including thermal conductivity (TC) and viscosity of NFs/MFs at 20 degrees C. All suspensions (NFs/MFs) exhibited a higher TC than the EG as base liquid and NFs showed higher TC enhancement values than the MFs. A TC enhancement of 16.4% was observed for NFs containing 1 wt % MoS2 NPs while the maximum increase in viscosity of 9.7% was obtained for the same NF at 20 degrees C. It indicates this NF system may have some potential to be utilized in heat transfer applications.

  • 167.
    Nordstrand, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Dynamic Langmuir Model: A Simpler Approach to Modeling Capacitive Deionization2019In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 26, p. 16479-16485Article in journal (Refereed)
    Abstract [en]

    Capacitive deionization (CDI) is emerging as an environment-friendly and energy-efficient water desalination option for meeting the growing global demand for drinking water. It is important to develop models that can predict and optimize the performance of CDI systems with respect to key operational parameters in a simple way. Such models could open up modeling studies to a wider audience by making modeling more accessible to researchers. We have developed the dynamic Langmuir model that can describe CDI in terms of a few fundamental macroscopic properties. Through extensive comparisons with data from the literature, it is shown that the model could describe and predict charge storage, ion adsorption, and charge efficiency for varying input ion concentrations, applied voltages, electrolyte compositions, electrode asymmetries, and electrode precharges in the equilibrium state. We conclude that the model could accurately describe a wide range of key features while being a simpler approach than the commonly applied theories for modeling CDI.

  • 168.
    Nordstrand, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Laxman, Karthik
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Myint, Myo Tay Zar
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    An Easy-to-Use Tool for Modeling the Dynamics of Capacitive Deionization2019In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 123, no 30, p. 6628-6634Article in journal (Refereed)
    Abstract [en]

    Capacitive deionization is an emerging method of desalinating brackish water that has been presented as an alternative to the widely applied technologies such as reverse osmosis. However, for the technology to find more widespread use, it is important not only to improve its efficiency but also to make its modeling more accessible for researchers. In this work, a program has been developed and provided as an open-source with which a user can simulate the performance of a capacitive deionization system by simply entering the basic experimental conditions. The usefulness of this program was demonstrated by predicting how the effluent concentration in a continuous-mode constant-voltage operation varies with time, as well as how it depends on the flow rate, applied voltage, and inlet ion concentration. Finally, the generality of the program has been demonstrated using data from reports in the literature wherein various electrode materials, cell structures, and operational modes were used. Thus, we conclude that the model, termed the dynamic Langmuir model, could be an effective and simple tool for modeling the dynamics of capacitive deionization.

  • 169. Promnimit, S.
    et al.
    Baruah, S.
    Lamdub, U.
    Dutta, Joydeep
    Center of Excellence in Nanotechnology, Asian Institute of Technology, Thailand.
    Hydrothermal growth of ZnO hexagonal nanocrystals: Effect of growth conditions2013In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 21, p. 57-63Article in journal (Refereed)
    Abstract [en]

    Hexagonal ZnO nanocrystals were synthesized through a hydrothermal route under mild conditions (growth temperature of 90 degrees C at atmospheric pressure). Pre-synthesized ZnO nanoparticles were used to serve as nucleation sites for the growth of the nanocrystals. The growth of ZnO nanorods was found to be surface independent. The dimensions of the hexagonal ZnO nanocrystals were observed to be dependent on the concentration of the reactants used (sources of Zn2+ and OH- ions), pH of the growth bath and also on the duration of crystal growth. The average diameter and height of the ZnO nanocrystals was found to be directly proportional to the concentration of the reactants as well as hydrolysis time. The orientation of the nanocrystals was found to be dependent upon the seeding method employed. Hexagonal single crystals of a wide range of dimensions and aspect ratios could be successfully synthesized through a control of growth parameters.

  • 170. Promnimit, S.
    et al.
    Cavelius, C.
    Mathur, S.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Growth of gold/zinc sulphide multilayer films using layer-by-layer assembly of colloidal nanoparticles2008In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 41, no 2, p. 285-291Article in journal (Refereed)
    Abstract [en]

    Fabrication of multilayer thin films through layer-by-layer (lbl) deposition of charged nanoparticles on tin-doped indium oxide (ITO) coated and uncoated glass substrates are reported. The thin films were constructed by alternately dipping a substrate into a colloidal suspension of chitosan capped zinc sulphide (ZnS) nanoparticles (∼30 nm) and citrate stabilized colloidal gold (Au) nanoparticles (∼20 nm) leading to electrostatic interactions between the oppositely charged nanoparticle layers. Thin films consisting of up to 200 deposition cycles by multiple dipping have been studied and surface morphology, changes in the optical absorption characteristics, thickness, uniformity, roughness and electrical characteristics are reported. The multilayered assemblies, attached to the surface by strong ionic bonds, were highly stable and could not be removed by moderate scratching. The current-voltage characteristics in the forward and reverse bias conditions demonstrated rectifying behaviors in the onset of conduction voltage which makes these films attractive for future electronic devices

  • 171. Promnimit, S.
    et al.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Self-organization of colloidal nanoparticles into functional pressure sensing device2012In: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 12, no 10, p. 8143-8146Article in journal (Refereed)
    Abstract [en]

    In this work, we report the multilayer thin film device for pressure sensing based on self-organized colloidal nanoparticles through the Layer-by-Layer (LbL) technique. The method in which macromolecules and nanoparticles are self-organized into assemblies to create novel nanostructures is receiving increasing research attention. Nanoparticles based multilayer thin films through the LbL self assembly process relies on electrostatic interaction of charged nanoparticles on flat substrates are reported as an interesting alternative for the fabrication of electronic devices.(3) These electronic devices composed of alternating chitosan capped zinc sulphide nanoparticles layers and citrate stabilized gold nanoparticles layers onto ITO coated glass substrates. The multilayered assemblies, attached to the surface by strong ionic bonds, were highly stable and could not be removed by moderate scratching. The multilayer films can be applied to detect pressure with satisfactory results where the conduction onset voltage decreases linearly with the applied pressure. Current voltage (I-V) characteristics were measured at room temperature in direct current mode in samples grown with varying number of deposition cycles, which are directly related to the number of multilayers grown on the substrate. It is a promising method for the future of pressure sensing device fabrication.

  • 172. Promnimit, S.
    et al.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Synthesis and electrical characterization of multilayer thin films designed by Layer-by-Layer self assembly of nanoparticles2010In: Journal of Nano Research, ISSN 1662-5250, Vol. 11, p. 1-6Article in journal (Refereed)
    Abstract [en]

    In this work, we report the directed self organization of multilayer thin film devices with colloidal nanoparticles through Layer-by-Layer (LbL) technique [1]. Self-organization of nanoparticles into assemblies to create novel nanostructures is getting increasing research attention in microelectronics, medical, energy and environmental applications. Directed self-organization of nanoparticles [2] into multilayer thin films were achieved by LbL growth through the interaction of oppositely charged of colloidal nanoparticles on substrates of any kind and shapes. Multilayer thin film devices were fabricated using multilayers of gold (conducting) nanoparticles separated by a dielectric nanoparticulate layer of zinc sulphide. The thin films obtained have been studied extensively and the changes in surface morphology, the optical absorption characteristics, thickness, uniformity, adhesion, and conduction behavior are reported. Current voltage (I-V) characteristics of multilayer devices with an increasing number of deposition cycles show an initial current blockade until an onset voltage value, which increases linearly upon the additional layers stacked in devices [3]. A conductive behavior of the device was observed upon exceeding the onset voltage. Moreover, I-V behavior showed that the conduction onset voltage increases linearly depending on the numbers of layers in the final device controlled by the deposition cycles. Systematic I-V characteristics in the forward and reverse biased conditions demonstrated rectifying behaviors in the onset of conduction voltage which makes these films attractive for future electronic device applications.

  • 173. Promnimit, S.
    et al.
    Jafri, S. H. M.
    Sweatman, D.
    Dutta, Joydeep
    School of Engineering and Technology, Asian Institute of Technology, Thailand.
    Conduction properties of layer-by-layer self-assembled multilayer nanoparticulate structures2008In: Journal of Nanoelectronics and Optoelectronics, ISSN 1555-130X, E-ISSN 1555-1318, Vol. 3, no 2, p. 184-189Article in journal (Refereed)
    Abstract [en]

    Nanoparticles based multilayer fabricated using layer-by-layer (LbL) self assembly process mediated through polyelectrolytes is reported as an interesting alternative for the fabrication of electronic devices. The effect of deposition cycle on the current-voltage characteristics of thin multilayer devices composed of alternating layers of chitosan-capped zinc sulphide nanoparticles (0 = 35 nm) and gold nanoparticles (0 = 20 nm), deposited onto a conducting indium tin oxide (ITO) coated glass substrate is reported. The current voltage (I-V) characteristics of multilayer devices with an increasing number of layers show an initial current blockade until an onset voltage value, which increases linearly upon the addition of the number of the layers stacked in the device. A conductive behavior of the device could be observed after exceeding the onset voltage. The conduction onset voltage is enhanced from similar to 0.14 V to similar to 5.6 V by increasing deposition cycles, from n = 5 to 100. Symmetric current-voltage characteristics can be observed both under forward and reverse bias conditions.

  • 174. Promnimit, Sujira
    et al.
    Bera, T.
    Baruah, S.
    Dutta, Joydeep
    Chitosan capped colloidal gold nanoparticles for sensing zinc ions in water2012In: Journal of Nano Research, ISSN 1662-5250, Vol. 16, p. 55-61Article in journal (Refereed)
    Abstract [en]

    In this work, we report sensing of Zn2+ ions using chitosan capped colloidal gold nanoparticles in aqueous media. The chitosan capping not just acted as an electro-static stabilizer to the colloidal gold nanoparticles, but also could bind to Zn2+ ions if present in the solution. However, the Zn2+ ions chelation to the chitosan capping decreased the stability of the colloidal gold hence shifted the surface plasmon peak to higher wavelengths. The extent of this red shift was found to be dependent on the concentration of the Zn2+ ions and therefore the presence of Zn2+ ions could be determined both qualitatively and quantitatively by analyzing the optical spectra of the chitosan capped gold nanoparticles. The sensing capability was also affected by the size of the nanoparticles, which could be tuned by adjusting the molar ratio of the reducing agent and the gold salt to the desired levels. Optical characteristics showed satisfactory results in estimating the amount of Zn2+ ions in water. This is thus a promising method for on the spot assessment of heavy metal ion concentrations in water.

  • 175. 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.

  • 176. Rahim, Hazli Rafis Bin Abdul
    et al.
    Bin Lokman, Muhammad Quisar
    Harun, Sulaiman Wadi
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Mohammed, Waleed Soliman
    TEMPERATURE SENSING BY SIDE COUPLING OF LIGHT THROUGH ZINC OXIDE NANORODS ON OPTICAL FIBERS2017In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 257, p. 15-19Article in journal (Refereed)
    Abstract [en]

    A temperature sensor fabricated by light side coupling through spirally patterned zinc oxide (ZnO) nanorods coated directly on plastic optical fiber (POF) is reported. A significant response to temperature changes from 20 degrees C to 100 degrees C based on extinction concept due to the attenuation of light by scattering and absorption was used. Sensitivity increases by a factor of 1.3 in spirally patterned coatings compared to optical fibers with continuous coating. The simplicity and economical sensor fabrication process for the swift and sensitive detection of temperature changes using visible light source show potential in environmental and biomedical applications.

  • 177. Rahim, Hazli Rafis Bin Abdul
    et al.
    Manjunath, Somarapalli
    Fallah, Hoorieh
    Thokchom, Siddharth
    Harun, Sulaiman Wadi
    Mohammed, Waleed Soliman
    Hornyak, Louis Gabor
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Side coupling of multiple optical channels by spiral patterned zinc oxide coatings on large core plastic optical fibers2016In: Micro & Nano Letters, ISSN 1750-0443, E-ISSN 1750-0443, Vol. 11, no 2, p. 122-126Article in journal (Refereed)
    Abstract [en]

    Improved optical side coupling efficiency was demonstrated for spiral patterned zinc oxide (ZnO) nanorods coated large core plastic optic fibers (POFs) as opposed to unpatterned continuous coatings. ZnO nanorods were grown by the hydrothermal method directly onto POF surfaces. Nanorods coating enhanced coupling inside the fiber by scattering light but were also capable of causing leakage. Structuring the growth to specific regions allows scattering from different segments along the fiber to contribute to the total coupled power. ZnO nanorods growth time of 12 h and temperature of 90 degrees C provided the best coupling voltage. Side coupling was measured to be a factor of 2.2 times better for spiral patterned coatings as opposed to unpatterned coatings. The formation of multiple segments was as well used for multiple-wavelength channels excitation where different bands were side coupled from different segments.

  • 178. Ray, S.
    et al.
    Dutta, Joydeep
    Barua, A. K.
    Deb, S. K.
    Bilayer SnO2:In/SnO2 thin films as transparent electrodes of amorphous silicon solar cells1991In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 199, no 2, p. 201-207Article in journal (Refereed)
  • 179. Renugopalakrishnan, V
    et al.
    Kannan, A M
    Srinivasan, S S
    Thavasi, V
    Ramakrishna, S
    Li, P
    Mershin, A
    Filipek, S
    Kumar, A
    Dutta, Joydeep
    Asian Institute of Technology, Thailand.
    Nanomaterials for energy conversion applications2009In: Nanomaterials for Energy Conversion Applications: Biosolar and biofuel cells, American Scientific Publishers, 2009, p. 155-178Chapter in book (Other academic)
  • 180. Sabah, A.
    et al.
    Dakua, I.
    Kumar, P.
    Mohammed, W. S.
    Dutta, Joydeep
    Asian Institute of Technology, Thailand; Sultan Qaboos University, Oman.
    Growth of templated gold microwires by self organisation of colloids on Aspergillus niger2012In: Digest Journal of Nanomaterials and Biostructures, ISSN 1842-3582, E-ISSN 1842-3582, Vol. 7, no 2, p. 583-591Article in journal (Refereed)
    Abstract [en]

    Template assisted self-organization of inorganic nanoparticles was investigated to render the physicochemical properties of both nanoparticles and biological materials in hierarchical architecture by using chloroauric acid and Ajinomoto® (mono-sodium glutamate, MSG) that served the dual purpose of stabilizing the NPs in the gold colloid and also nutritional source for growth of Aspergillus niger (A. niger) hyphae and mycelia (acting as living template). The coating of gold nanoparticles on living hyphae was controlled by varying MSG concentration to gold salt and the reaction temperature without requiring any hazardous re-agent. Grown microwires displayed wide variations in dimension and morphology depending upon the preheating and nutrient conditions. Uniform and thick agglomeration of gold nanoparticles at higher molar ratios (MR's ~ 10 and 12) formed microwire of diameters between 1-2 μm and length exceeding 1 mm within two weeks. Heat treatment above 40-45°C led to negligible growth, wide variation in diameter (1.1-3.6 μm) and significant reduction of gold colloids due to excessive surface evaporation, whereas, maximum morphological changes in microwires were observed at 300C, having diameter 2.1-2.9 μm. The pH of the gold colloids was found to change gradually from 3 to &gt; 7 during the growth process indicating the successive aggregation of gold nanoparticles on living hyphae and the consumption of glutamic acid by the microbes. High surface area of these bio-templated gold microwires is interesting for sensing, electronics, optics and catalysis applications.

  • 181. Sabah, A.
    et al.
    Kumar, P.
    Mohammed, W. S.
    Dutta, Joydeep
    Asian Institute of Technology, Thailand; Sultan Qaboos University, Oman.
    Visible-light-induced directed gold microwires by self-organization of nanoparticles on Aspergillus Niger2013In: Particle & particle systems characterization, ISSN 0934-0866, E-ISSN 1521-4117, Vol. 30, no 5, p. 473-480Article in journal (Refereed)
    Abstract [en]

    A directional point-to-point growth of microwires of gold nanoparticles (AuNPs) self-organized on Aspergillus niger (A. niger) templates by utilizing positive phototropic fungal response to different spectral ranges of visible light is reported. A. niger serves as a living template for the self-organization of monosodium glutamate (MSG) capped gold colloids under controlled nutrient trigger and appropriate light, temperature, and humidity conditions. The experimental results show that control of these parameters eliminates the need for any microchannels for the directional growth of microwires. The growth rate of fungal hyphae increases exponentially under light illumination compared to its growth in the dark under similar conditions. White light is found to be most suitable to trigger the directional growth. Gold microwires of about 1 to 2 m diameter and length exceeding 1 mm are grown within a week with a maximum divergence of 40-50 degrees from the light path regardless of the wavelength of the light irradiation. Phototropic response of fungi has been investigated intensively over the last three decades, but this is the first report on the collective use of microbial tropism and directed biomimetic self-organization of metallic nanoparticles on living organisms.

  • 182. Saoud, K.
    et al.
    Alsoubaihi, R.
    Bensalah, N.
    Bora, T.
    Bertino, M.
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Synthesis of supported silver nano-spheres on zinc oxide nanorods for visible light photocatalytic applications2015In: Materials research bulletin, ISSN 0025-5408, E-ISSN 1873-4227, Vol. 63, p. 134-140Article in journal (Refereed)
    Abstract [en]

    We report the synthesis of silver (Ag) nano-spheres (NS) supported on zinc oxide (ZnO) nanorods through two step mechanism, using open vessel microwave reactor. Direct reduction of ZnO from zinc nitrates was followed by deposition precipitation of the silver on the ZnO nanorods. The supported Ag/ZnO nanoparticles were then characterized by electron microscopy, X-ray diffraction, FTIR, photoluminescence and UV-vis spectroscopy. The visible light photocatalytic activity of Ag/ZnO system was investigated using a test contaminant, methylene blue (MB). Almost complete removal of MB in about 60 min for doses higher than 0.5 g/L of the Ag/ZnO photocatalyst was achieved. This significant improvement in the photocatalytic efficiency of Ag/ZnO photocatalyst under visible light irradiation can be attributed to the presence of Ag nanoparticles on the ZnO nanoparticles which greatly enhances absorption in the visible range of solar spectrum enabled by surface plasmon resonance effect from Ag nanoparticles.

  • 183.
    Saoud, Khaled
    et al.
    Virginia Commonwealth Univ Qatar, Liberal Arts & Sci, Doha, Al Doha, Qatar..
    Al Soubaihi, Rola
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Self-sustaining and hysteresis behavior of low-temperature CO oxidation on mesoporous Pd/SiO2 aerogel s catalyst under dynamics conditions2018In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 256Article in journal (Other academic)
  • 184. Sapkota, Ajaya
    et al.
    Anceno, Alfredo J
    Baruah, Sunandan
    Shipin, Oleg V
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Zinc oxide nanorod mediated visible light photoinactivation of model microbes in water2011In: Nanotechnology, ISSN 1361-6528, Vol. 22, no 21Article in journal (Refereed)
  • 185. Sardar, Samim
    et al.
    Sarkar, Soumik
    Myint, Myo Tay Zar
    Al-Harthi, Salim
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Pal, Samir Kumar
    Role of Central Metal Ion in Hematoporphyrin-Functionalized Titania in Solar Energy Conversion Dynamics2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 42, p. 18562-18570Article in journal (Refereed)
    Abstract [en]

    In this study, we have investigated the efficacy of electron transfer processes in hematoporphyrin (HP) and iron hematoporphyrin ((Fe) HP) sensitized titania as potential materials for capturing and storing solar energy. Steady-state and picosecond-resolved fluorescence studies show the efficient photoinduced electron transfer processes in hematoporphyrin-TiO2 (HP-TiO2) and Fe(III)-hematoporphyrin-TiO2 (Fe(III)HP-TiO2) nanohybrids, which reveal the role of central metal ions in electron transfer processes. The bidentate covalent attachment of HP onto TiO2 particulates is confirmed by FTIR, Raman scattering and X-ray photoelectron spectroscopy (XPS) studies. The iron oxidation states and the attachment of iron to porphyrin through pyrrole nitrogen atoms were investigated by cyclic voltammetry and FTIR studies, respectively. We also investigated the potential application of HP-TiO2 and Fe(III)HP-TiO2 nanohybrids for the photodegradation of a model organic pollutant methylene blue (MB) in aqueous solution under wavelength dependent light irradiation. To further investigate the role of iron oxidation states in electron transfer processes, photocurrent measurements were done by using Fe(III) and Fe(II) ions in porphyrin. This work demonstrates the role of central metal ions in fundamental electron transfer processes in porphyrin sensitized titania and their implications for dye-sensitized device performance.

  • 186. Sarkar, Biplab
    et al.
    Dutta, Joydeep
    Sultan Qaboos University, Oman; Asian Institute of Technology, Thailand.
    Optimization of the sublethal dose of silver nanoparticle through evaluating its effect on intestinal physiology of Nile tilapia (Oreochromis niloticus L.)2015In: Journal of Environmental Science and Health. Part A: Toxic/Hazardous Substances and Environmental Engineering, ISSN 1093-4529, E-ISSN 1532-4117, Vol. 50, no 8, p. 814-823Article in journal (Refereed)
    Abstract [en]

    Silver nanoparticles (SNPs) are widely used in a variety of biomedical and consumer products as an antimicrobial additive. The present study was conducted to evaluate the impacts of low-dose SNPs on intestinal physiology of tilapia (Oreochromis niloticus L.) for assessing its apparent environmental risk due to extensive commercial use. SNPs were synthesized by a chemical reduction method yielding 1-27 nm oval shaped particles. Early fingerlings of tilapia were exposed with two sublethal concentrations (0.8 and 0.4 mg L-1) of SNPs for twenty one days period and its impact on the intestinal physiology was evaluated by histochemistry, catalase expression, glutamate dehydrogenase activity, SDS-PAGE and gut micro flora count. Histological analysis showed thinning of intestinal wall, swelling on mucosal layer and immunohistochemical assay exhibited an enhanced catalase expression in SNPs treated fishes. Gut microflora count elicited a dose-dependent depletion and a variable SDS-PAGE profile followed by significant (P < 0.05) elevations in glutamate dehydrogenase activity in SNPs-treated fishes. This study was designed to provide a better understanding of environmentally acceptable, dose-dependent SNPs delivery in fishes and to formulate guidelines in aquatic toxicology.

  • 187. Sarkar, S.
    et al.
    Makhal, A.
    Bora, T.
    Lakhsman, K.
    Singha, A.
    Dutta, Joydeep
    Pal, S. K.
    Hematoporphyrin-ZnO nanohybrids: Twin applications in efficient visible-light photocatalysis and dye-sensitized solar cells2012In: ACS Applied Materials and Interfaces, ISSN 1944-8244, Vol. 4, no 12, p. 7027-7035Article in journal (Refereed)
  • 188. Sarkar, S.
    et al.
    Makhal, A.
    Lakshman, K.
    Bora, T.
    Dutta, Joydeep
    Asian Institute of Technology, Klong Luang, Thailand.
    Kumar Pal, S.
    Dual-sensitization via electron and energy harvesting in CdTe quantum dots decorated ZnO nanorod-based dye-sensitized solar cells2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 27, p. 14248-14256Article in journal (Refereed)
    Abstract [en]

    Different-sized, 3-mercaptopropionic acid (MPA) stabilized CdTe quantum dots (QDs) have been prepared in aqueous solution, and potential cosensitization of such QDs in ZnO nanorod (NR)-based dye-sensitized solar cells (DSSCs) has been established. The results presented in this study highlight two major pathways by which CdTe QDs may contribute to the net photocurrent in a DSSC: (1) a direct injection of charge carriers from QDs to ZnO semiconductor via photoinduced electron transfer (PET) and (2) an indirect excitation of the sensitizing dye (SD) N719 molecules by funneling harvested light via Förster resonance energy transfer (FRET). The steady-state and picosecond-resolved luminescence measurements were combined to clarify the process of PET and FRET from the excited QDs to ZnO NR and SD N719, respectively. On the basis of these advantages, the short-circuit current density and the photoconductivity of the QD-assembled DSSCs with distinct architectures are found to be much higher than DSSCs fabricated with N719 sensitizer only.

  • 189. Sarkar, S.
    et al.
    Sardar, S.
    Makhal, A.
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Pal, S. K.
    Engineering FRET-based solar cells: Manipulation of energy and electron transfer processes in a light harvesting assembly2014In: High-Efficiency Solar Cells, American Chemical Society (ACS), 2014, Vol. 190, p. 267-318Chapter in book (Refereed)
  • 190. Sarkar, Soumik
    et al.
    Makhal, Abhinandan
    Baruah, Sunandan
    Mahmood, Mohammad A
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Pal, Samir K
    Nanoparticle-Sensitized Photodegradation of Bilirubin and Potential Therapeutic Application2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 17, p. 9608-9615Article in journal (Refereed)
  • 191. Sarkar, Soumik
    et al.
    Makhal, Abhinandan
    Bora, Tanujjal
    Baruah, Sunandan
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Pal, Samir Kumar
    Photoselective excited state dynamics in ZnO–Au nanocomposites and their implications in photocatalysis and dye-sensitized solar cells2011In: Physical Chemistry Chemical Physics, ISSN 1463-9084, Vol. 13, no 27, p. 12488-12496Article in journal (Refereed)
  • 192. Sathe, P.
    et al.
    Laxman, Karthik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Functional Materials, FNM.
    Myint, M. T. Z.
    Dobretsov, S.
    Richter, J.
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics, Functional Materials, FNM.
    Bioinspired nanocoatings for biofouling prevention by photocatalytic redox reactions2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, no 1, article id 3624Article in journal (Refereed)
    Abstract [en]

    Aquaculture is a billion dollar industry and biofouling of aquaculture installations has heavy economic penalties. The natural antifouling (AF) defence mechanism of some seaweed that inhibits biofouling by production of reactive oxygen species (ROS) inspired us to mimic this process by fabricating ZnO photocatalytic nanocoating. AF activity of fishing nets modified with ZnO nanocoating was compared with uncoated nets (control) and nets painted with copper-based AF paint. One month experiment in tropical waters showed that nanocoatings reduce abundances of microfouling organisms by 3-fold compared to the control and had higher antifouling performance over AF paint. Metagenomic analysis of prokaryotic and eukaryotic fouling organisms using next generation sequencing platform proved that nanocoatings compared to AF paint were not selectively enriching communities with the resistant and pathogenic species. The proposed bio-inspired nanocoating is an important contribution towards environmentally friendly AF technologies for aquaculture.

  • 193. Sathe, Priyanka
    et al.
    Myint, M. T. Z.
    Dobretsov, Sergey
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Removal and regrowth inhibition of microalgae using visible light photocatalysis with ZnO nanorods: a green technology2016In: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 162, p. 61-67Article in journal (Refereed)
    Abstract [en]

    Algal biofouling can be a major problem during membrane filtration processes reducing membrane efficiency. Removal of microalgae by visible light photocatalysis using zinc oxide (ZnO) nanorods was studied in this work. ZnO nanorods were grown on polypropylene support substrates. The treatment unit was constructed by incorporating ZnO nanocoated substrates in a glass tube. Anti-algal activity of the treatment units were tested using green microalga, Dunaliella salina, of 107 cells/mL concentration, which is higher than the concentration of cells during algal blooms. Nearly total algal cell inactivation was achieved within 2 h of continuous visible light illumination in the presence of nanocoated support substrates, as determined by flow cytometry analysis (98%) and trypan blue staining (95%). Uncoated support substrate under light illumination did not lead to algal cell mortality (1.7%). Complete inhibition of any regrowth of algal cells treated with nanocoated substrates was confirmed as no significant changes in the total number of cells were observed even after 2 weeks of incubation of the treated culture. The anti-algal activity of ZnO nanorods was attributed to the formation of reactive oxygen species (ROS) through photocatalytic processes. ZnO nanorod coated substrates used in the treatment units could be a suitable green method to control membrane fouling in water treatment plants avoiding the utilisation of harmful chemicals.

  • 194. Sathe, Priyanka
    et al.
    Richter, Jutta
    Myint, Myo Tay Zar
    Dobretsov, Sergey
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Self-decontaminating photocatalytic zinc oxide nanorod coatings for marine microfouling prevention: a mesocosm study2016In: Biofouling (Print), ISSN 0892-7014, E-ISSN 1029-2454, Biofouling, Vol. 32, no 4, p. 383-395Article in journal (Refereed)
  • 195. Scholz, S. M.
    et al.
    Carrot, G.
    Hilborn, J.
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Valmalette, J. -C
    Hofmann, H.
    Luciani, A.
    Optical properties of gold-containing poly(acrylic acid) composites1998In: MRS / [ed] K.E. Gonsalves, M-I. Baraton, J.X. Chen, J.A. Akkara, 1998, Vol. 501, p. 79-84Conference paper (Refereed)
  • 196. Scholz, S. M.
    et al.
    Dutta, Joydeep
    Hofmann, H.
    Hofmeister, H.
    Raman spectroscopic study of silicon nanopowders1997In: Journal of Materials Science & Technology, ISSN 1005-0302, Vol. 13, no 4, p. 327-332Article in journal (Refereed)
    Abstract [en]

    Vibrational properties of silicon nanopowders are discussed with reference to Raman spectroscopic measurements. The powders were produced in a low pressure rf plasma from the cluster induced agglomeration of positive ions formed during the dissociation of silane. Influence of thermal treatment and the crystallization phenomena of the powder were studied. Raman spectroscopic measurements reveal size quantization effects for the particles as well as the existence of partially ordered regions in the apparently amorphous primary particles. The crystalline and amorphous volume fraction in the material were calculated from the relative spectral intensities. The results obtained in these experiments are consistent with the observations from recent high resolution transmission electron microscopy studies of these powders.

  • 197. Scholz, S. M.
    et al.
    Vacassy, R.
    Dutta, Joydeep
    Swiss Fed. Inst. Technol. Lausanne, Switzerland; Balzers Process Systems, Display Technology Division, Liechtenstein.
    Hofmann, H.
    Akinc, M.
    Mie scattering effects from monodispersed ZnS nanospheres1998In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 83, no 12, p. 7860-7866Article in journal (Refereed)
    Abstract [en]

    Transmission spectra of monodispersed particles exhibit pronounced resonance features from which particle properties can be deduced. ZnS powders were used as model materials since they can be synthesized by homogeneous precipitation with a narrow size distribution. The optical extinction spectra can be simulated using Mie scattering theory, and can be used as an in situ diagnostic tool for following the growth of particles during precipitation reactions. Using results of particle diameter measurements by other methods, information on the refractive index of the particles can be retrieved, indicating a highly porous internal structure of the spheres. Distinct features in the experimental and simulated spectra have been interpreted as to arise from circumference and diameter resonance effects in the particles. The simultaneous observation of these two effects allows one to estimate size and solid volume fraction from simple transmission spectra by application of an effective-medium model for the simulation parameters. The potential of application of Mie resonance effects for selective light screening or as pigments are discussed.

  • 198. Scholz, S. M.
    et al.
    Vacassy, R.
    Lemaire, L.
    Dutta, Joydeep
    Swiss Fed. Inst. Technol. Lausanne, Switzerland; Balzers Process Systems, Display Technology Division, Liechtenstein.
    Hofmann, H.
    Nanoporous Aggregates of ZnS Nanocrystallites1998In: Applied organometallic chemistry, ISSN 0268-2605, E-ISSN 1099-0739, Vol. 12, no 5, p. 327-335Article in journal (Refereed)
    Abstract [en]

    During the synthesis of ZnS powders by wet chemical precipitation, the formation of nanoporous spheres is observed. The powders have been investigated using thermogravimetric analysis, X-ray diffraction and optical spectroscopies. Nanopore formation can be explained by several stages of growth. The formation of nanoparticles as primary particles is followed by their agglomeration forming secondary particles. These secondary particles are monodispersed spheres with a considerable porosity, because the agglomeration of the nanoparticles is unlikely to be volume-filling. The voids or nanopores formed by this agglomeration process in the secondary particles is estimated to comprise around 35% of the sphere volume. They are mainly filled with water and the residues of the chemical reagents. Water in the pores partially reacts with ZnS and forms hydrated sulphates. The chemical reagents used for the precipitation reactions are also found to be bound to the nanocrystallite's surfaces as ligands in some cases. Depending on the reaction conditions and reagents, the agglomeration of the nanoparticles can also be modified or hindered by the use of complexing agents acting as a sterically stabilizing surface layer on the nanocrystallites. The agglomeration of nanoparticles to larger units being a general phenomenon, this use of complexing agents to control pore formation and agglomerate size should be applicable to other nanocrystalline systems.

  • 199. Schulte, J.
    et al.
    Dutta, Joydeep
    Nanotechnology in environmental protection and pollution2005Collection (editor) (Refereed)
  • 200.
    Shafiq, Muhammad
    et al.
    Sultan Qaboos Univ, Dept Elect & Comp Engn, Coll Engn, POB 33, Muscat 123, Oman..
    Laxman, Karthik
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Estimation of ion adsorption using iterative analytical model in capacitive deionization process2018In: Desalination and Water Treatment, ISSN 1944-3994, E-ISSN 1944-3986, Vol. 116, p. 75-82Article in journal (Refereed)
    Abstract [en]

    Capacitive deionization (CDI) is an upcoming technique that can replace existing processes for removing and recuperating metal ions from dilute industrial waste waters. CDI removes ions via electrosorption on to its electrode surfaces, the efficiency of which is a function of CDI electrode properties that progressively change during continued operation. As such a need exists to develop a model to predict CDI performance over elongated periods which is independent of electrode properties and has negligible error values. By applying a first order non-linear dynamic model (FONDM) with inputs independent of the electrode characteristics, we propose a universal model that can predict CDI ion adsorption capacity with changes in applied potential, flow rate and electrolyte temperature to within 5% of the experimentally obtained results. The model was verified using activated carbon cloth (ACC) as a test electrode and aqueous sodium chloride solution as electrolyte, with a good prediction for ion electrosorption efficiency and time dependent electrosorption dynamics. The simplicity of the model makes it easy to adapt for various applications and in the development of intelligent control systems for CDI units in practical settings.

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