Change search
Refine search result
12345 101 - 150 of 223
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 101. Giri, Anupam
    et al.
    Goswami, N.
    Pal, M.
    Zar Myint, M. T.
    Al-Harthi, S.
    Singha, A.
    Ghosh, B.
    Dutta, Joydeep
    Deparment in Nanotechnology, Water Research Center, Sultan Qaboos University, Al-Khoudh, Oman.
    Pal, S. K.
    Rational surface modification of Mn3O4 nanoparticles to induce multiple photoluminescence and room temperature ferromagnetism2013In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 1, no 9, p. 1885-1895Article in journal (Refereed)
    Abstract [en]

    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.

  • 102. Habib, K.
    et al.
    Mohammad, W.
    Karim, F.
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Measurement of aluminum oxide film in situ during anodization of aluminum by fabry-pÉrot interferometry2017In: Corrosion and Prevention 2017, Australasian Corrosion Association , 2017Conference paper (Refereed)
    Abstract [en]

    A novel experimental scheme for real time measurement of aluminum oxide film during anodization was developed for the first time. The scheme was established based on a combination of a fiber optic sensor of Fabry-Pérot interferometry and direct current (DC) electrochemical methods. The scheme was assembled in a way to simultaneously anodize the aluminum samples and to measure the thickness of the aluminum oxide film. The anodization process of aluminum sample was carried out in 2% sulfuric acid (H2SO4) solution by the DC methods at room temperature. The estimated thickness of the aluminum oxide film by the novel scheme was verified by scanning electron microscopy (SEM) and holographic interferometry. This study shows that real time measurement of the thickness of aluminum oxide film by Fabry-Pérot interferometry (2.136µm) is feasible as it closely matched the thickness determined by SEM (2.1µm). The obtained values of the resistance by Fabry-Pérot interferometer (2.4 x109 Ohms) and by holographic interferometry (2.54x109 Ohms) were found twice the obtained value of the resistance by EIS (1.25x109 Ohms).

  • 103. Habib, K.
    et al.
    Mohammad, W.
    Karim, F.
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Resistance values of aluminum oxide film in situ during anodization of aluminum by fabry-pérot interferometry2017In: ECS Transactions, Electrochemical Society Inc. , 2017, no 10, p. 1221-1229Conference paper (Refereed)
    Abstract [en]

    A combination of Fabry-Pérot interferometry and the DC electrochemical method have been used for the first time, in situ, to measure the resistance of aluminum oxide films in 2% sulfuric acid solution. Values of the corresponding resistance of the obtained Al2O3 film thickness were determined during anodization of aluminum (Al) in 2% H2SO4. The obtained resistance values were verified by electrochemical impedance spectroscopy (EIS) and holographic interferometry. The corresponding resistance (2.4 x109 Ohms) to the final thickness of the aluminum oxide film was found in an agreement with the resistance value that was measured by holographic interferometry, 2.54x109 Ohms, in 2% H2SO4. On the contrary, the corresponding resistance (2.4 x109 Ohms) to the final thickness of the aluminum oxide film was found twice the value of the resistance that was measured by the electrochemical impedance spectroscopy (EIS), 1.25x109 Ohms, in 2% H2SO4.

  • 104. Habib, Khaled
    et al.
    Mohammad, Waleed
    Karim, Farzia
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Electrochemical Parameters of Aluminum Oxide Film in Situ During Anodization of Aluminum by White Light-Optical Interferometry2019In: Corrosion, Nashville, Tennessee, USA: NACE International, 2019, Vol. 2019, article id 12837Conference paper (Refereed)
    Abstract [en]

    Both of Fabry-Pérot interferometry and the DC electrochemical method have been simultaneously used for the first time to measure in situ the anodic current density (J) of aluminum oxide films in 0,2,4,5,6,8 and 10% sulfuric acid solutions (H2SO4). The calculated values of J by Fabry-Pérot interferometry were verified by the DC electrochemical method, i.e., a potentiostat, and the AC electrochemical method, i.e., a potentiostat with an accessory of AC impedance spectroscopy (EIS). The corresponding thickness (d) of the aluminum oxide (Al2O3) film to the anodic current density was determined by Fabry-Pérot interferometry under a potentiostatic condition of 9 V with respect to the open circuit potential of the aluminum samples in the H2SO4 solutions, for 90 minutes. Then, the obtained d of the Al2O3 films by Fabry-Pérot interferometry was verified by scanning electron microscopy (SEM) and compared to d values that were obtained by the EIS. The calculated J by Fabry-Pérot interferometry was found in agreement with those of the DC electrochemical method. In contrast, the calculated J by Fabry-Pérot interferometry was found in a 3 fold discrepancy with data obtained by the EIS.

  • 105. Hemtanon, B.
    et al.
    Thanachayanont, C.
    Das, D.
    Dutta, Joydeep
    Asian Institute of Technology, Thailand.
    Diode fabricated by layer by layer deposition of semiconductor nanoparticles2007Conference paper (Refereed)
    Abstract [en]

    We report the development of a modified polyelectrolyte deposition technique for building multilayer thin films. The quantum dots of zinc sulphide nanoparticles doped with manganese were synthesized by co-precipitation techniques and the nanoparticles were found to consist of crystallites that were estimated to be around 2.2 nm. The modified polyelectrolyte deposition technique has been used for the growth of multifunctional nanoparticulate ZnS thin films and schottky diodes. The Schottky junction device exhibit diode-like behavior and this technique shows promise for large area construction of diodes using wet-chemical synthesis of semiconductor nanoparticles.

  • 106. Herard, C.
    et al.
    Bowen, P.
    Lemaitre, J.
    Dutta, J.
    Chemical synthesis and characterization of nano-crystalline palladium oxide1995In: Nanostructured Materials, Vol. 6, no 1-4, p. 313-316Article in journal (Refereed)
  • 107. Hofmann, H.
    et al.
    Dutta, Joydeep
    Scholz-Odermatt, S.
    Vacassy, R.
    Valmalette, J.-Ch.
    Potential of nanosized ceramic powder for functional applications1997In: Ceramic Engineering and Science Proceedings, 1997, Vol. 18, no 4 B, p. 687-694Conference paper (Refereed)
    Abstract [en]

    Nanophase ceramic particles are building-blocks for the formation of nanostructured ceramics and are important in a composite for functional applications. Different synthesis methods for nanosized ceramics were developed. Depending on the method and chemical composition, powders which are agglomerates of nanosized primary particles exist. These primary particles show very small grain size distribution.

  • 108. Hofmeister, H.
    et al.
    Dutta, J.
    Hofmann, H.
    Atomic structure of amorphous nanosized silicon powders upon thermal treatment1996In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 54, no 4, p. 2856-2862Article in journal (Refereed)
    Abstract [en]

    Amorphous silicon powders prepared by plasma-enhanced chemical vapor deposition, of 8-24-nm-sized particles agglomerated into larger aggregates were annealed in a reducing atmosphere to study the phase transformation behavior of these particles. High-resolution electron microscopy revealed a very rough surface, with structural details of 1 to 2 nm, of the as-prepared single powder particles. Upon l h annealing at temperatures between 300 and 600 °C circular contrast features, 1.5-2.5 nm in size, are observed in the amorphous particles, hinting to the formation of a medium-range order. A distinct onset of crystallization is achieved at 700 °C, with structures ranging from very small crystalline ordered regions of 2.5-3.5 nm in size, to fast-grown multiply twinned crystallites. Rapid progress of crystallization, mainly caused by growth twinning, is observed upon annealing at 800 °C. At 900 °C, almost completely crystalline particles are formed. The particles having lattice characteristics of diamond cubic silicon frequently exhibit a faulted structure, because of multiple twinning events. They are covered by an amorphous oxide shell of a 1.5 to 2 nm thickness, which is found to develop with the onset of crystallization. Size and surface roughness of the as-prepared powders are widely preserved throughout all stages of heating, and practically no sintering occurs up to 900 °C.

  • 109. Hofmeister, H.
    et al.
    Dutta, J.
    Hofmann, H.
    Nanoscale ordering in amorphous silicon powders formed by plasma induced reaction of silane1997In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 235-238, no 2, p. 595-600Article in journal (Refereed)
  • 110. Hofmeister, H.
    et al.
    Ködderitzsch, P.
    Dutta, Joydeep
    Department of Materials Science, Swiss Fed. Institute of Technology, CH-1015 Lausanne, Switzerland.
    Structure of nanometersized silicon particles prepared by various gas phase processes1998In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 232-234, p. 182-187Article in journal (Refereed)
    Abstract [en]

    We have explored various gas phase processes for the fabrication of nanometersized Si and SiOx particles and measured their structural properties (agglomeration, size, shape, crystallinity, surface roughness and internal structure) by conventional and high resolution electron microscopy. Agglomerated amorphous Si particles, 10-30 nm in size, were prepared by gas phase reactions including cluster growth processes in a low pressure silane plasma. Annealing at 900°C resulted in almost complete crystallisation of nearly spherical particles covered by an amorphous oxide shell. Inert gas arc evaporation of silicon yielded single crystalline, spherical Si particles, 4-16 nm in size, in which no defects were detected. These particles, agglomerated into chains and tangles, are covered entirely by a thin amorphous oxide layer. Thermal evaporation of solid SiO in an inert gas atmosphere produced agglomerated, nearly spherical amorphous SiOx particles, 8-24 nm in size, with considerable surface roughness. Upon annealing at 900°C, the formation of 3-6 nm sized Si crystallites in the interior of these particles was observed.

  • 111. Hollenstein, C.
    et al.
    Dorier, J. -L
    Dutta, J.
    Sansonnens, L.
    Howling, A. A.
    Diagnostics of particle genesis and growth in RF silane plasmas by ion mass spectrometry and light scattering1994In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 3, no 3, p. 278-285Article in journal (Refereed)
  • 112. Hornyak, G. L.
    et al.
    Patrissi, C. J.
    Martin, C. R.
    Valmalette, J. -C
    Dutta, J.
    Hofmann, H.
    Dynamical Maxwell-Garnett optical modeling of nanogold-porous alumina composites: Mie and kappa influence on absorption maxima1997In: Nanostructured materials, ISSN 0965-9773, E-ISSN 1872-9150, Vol. 9, no 1-8, p. 575-578Article in journal (Refereed)
    Abstract [en]

    Composites consisting of nanogold in porous alumina host membranes have been fabricated and characterized. Nanocluster size (11 nm to 60 nm radius) and shape (prolate to oblate) were varied experimentally. Two phenomena were responsible for the position of maximum absorption (λmax) of the composites. First, light scattering due to extrinsic electrodynamic effects became important as particle size was increased. This resulted in red shifts in λmax and is known as the Mie effect. Secondly, blue shifts were induced as particle aspect ratio was increased. We have designated shifts due to particle shape and orientation as the "kappa" effect. The two appeared to exert their influence independently. Simulations by means of the dynamical Maxwell-Garnett (DMG) expression resulted in good correlation with experimental λmax. We demonstrate again the versatility of the template method of synthesizing nanostructured materials. © 1997 Acta Metallurgica Inc.

  • 113. Hornyak, G. L.
    et al.
    Patrissi, C. J.
    Oberhauser, E. B.
    Martin, C. R.
    Valmalette, J. -C
    Lemaire, L.
    Dutta, J.
    Hofmann, H.
    Effective medium theory characterization of Au/Ag nanoalloy-porous alumina composites1997In: Nanostructured materials, ISSN 0965-9773, E-ISSN 1872-9150, Vol. 9, no 1-8, p. 571-574Article in journal (Refereed)
    Abstract [en]

    The optical constants nAl and kAl of a 50/50 volume fraction Au/Ag alloy were derived synthetically by application of a Bruggeman (BG) effective medium expression. The alloy data base was then input into a Maxwell-Garnett (MG) effective medium expression to determine the absorption maximum of the nano- alloy/insulator composite (the volume fraction of the nano-alloy was equal to 5%). The absorption maximum (λmax) of the hypothetical composite was found to be 499 nm for spherical particles and was blue-shifted relative to that of a composite containing pure gold nanospheres (499 vs. 528 nm respectively). The transmission color at this wavelength was a red-orange. λmax in the range 512 to 519 nm (Au/Ag alloy between 60/40 - 70/30 volume fraction respectively) is needed to obtain the scarlet-red exhibited by the famous Lycurgus cup of 4th century Rome (1). © 1997 Acta Metallurgica Inc.

  • 114. Hossain, M. K.
    et al.
    Ghosh, S. C.
    Boontongkong, Y.
    Thanachayanont, C.
    Dutta, Joydeep
    Microelectronics, School of Advanced Technologies, Asian Institute of Technology, Klong Luang, Pathumthani 12120, Thailand.
    Growth of Zinc Oxide nanowires and nanobelts for gas sensing applications2005In: Journal of Metastable and Nanocrystalline Materials, ISSN 1422-6375, Vol. 23, p. 27-30Article in journal (Refereed)
    Abstract [en]

    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.

  • 115. Houriet, R.
    et al.
    Feschotte, J.
    Dutta, J.
    Hofmann, H.
    Growth kinetics of tin oxide from tin tetrachloride/ methanol complex1996In: Vide: Science, Technique et Applications, 1996, p. 230-232Conference paper (Refereed)
    Abstract [en]

    Extensive in-situ pyrolysis experiments are carried out to understand the deposition kinetics of SnO2 from SnCl4·CH3OH complex, using X-ray fluorescence (XRF), mass (MS) and infra-red (FTIR) spectroscopy. SnCl4 transforms into SnO2 by two processes, a direct reaction probably with water at approx. 100°C and the decomposition of the complex at higher temperatures (> 300°C). HCI which is evolved during the reactions probably plays an important role in the crystallization of SnO2.

  • 116. Imani, R.
    et al.
    Talaiepour, M.
    Dutta, Joydeep
    Asian Institute of Technology, Thailand.
    Ghobadinezhad, M. R.
    Hemmasi, A. H.
    Nazhad, M. M.
    Production of antibacterial filter paper from wood cellulose2011In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 6, no 1, p. 891-900Article in journal (Refereed)
    Abstract [en]

    Paper has a visible market-share in hygiene products either in the form of personal hygiene or as food packaging. The designation "hygiene", though it suggests cleanliness, does not imply antibacterial properties; rather it can be stated that hygiene products do not initiate microorganism growth. Antibacterial products could restrict propagation of pathogenic bacteria either by holding bacteria or by trapping and neutralizing them. Most research in this field has been conducted using textile fibers as a substrate, but the present work uses paper instead. The objective was to produce an antibacterial filter paper capable of trapping and neutralizing pathogenic microorganisms using wood fibers. To produce antibacterial paper, chitosan and nanosilver capped with PAA (polyacrylic acid) were deposited on the fiber surface using a layer-by-layer technique. Samples for the tests were prepared from refined bleached softwood (RBSW) kraft pulp. The deposition of antibacterial agents on fiber as well as paper were monitored using a zeta potential analyzer (ZPA), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIRS). The minimum requirement for deposition of the agents was a multilayer comprised of eight alternating layers. The deposition onto fiber or paper had no effect on tensile strength or the pore structure of the substrate.

  • 117. Jafri, S. H. M.
    et al.
    Dutta, Joydeep
    Asian Institute of Technology, Thailand.
    Sweatman, D.
    Sharma, A. B.
    Current-voltage characteristics of layer-by-layer self-assembled colloidal thin films2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, no 13Article in journal (Refereed)
    Abstract [en]

    Self-organized construction of advanced materials and devices has been carried out starting with tailor-made colloidal nanoparticles as building blocks. Multilayer thin films of gold nanoparticles stabilized by glutamates and zinc sulfide nanoparticles capped with chitosan were self-organized by a modified polyelectrolyte deposition process. Resistive current-voltage characteristic was observed in devices (less than 50 layers). The conduction onset in thicker devices (> 50 layers) was found to be at applied voltages of similar to 1.6, similar to 1.94, and similar to 2.79 V for 75, 100, and 150 layer structures, respectively. Devices exhibit similar behavior in forward and reverse biases and the electrical characteristics were repeatable.

  • 118. Jafri, S. H. M.
    et al.
    Sharma, A. B.
    Thanachayanont, C.
    Dutta, Joydeep
    Asian Institute of Technology, Thailand.
    Directed self-assembly of multilayer thin films of ZnS and gold nanoparticles by modified polyelectrolyte deposition technique2005In: Materials Research Society Symposium Proceedings, Materials Research Society, 2005, p. 483-494Conference paper (Refereed)
    Abstract [en]

    Fabrication strategies based on mechanisms of self-assembly are now widely being recognized as inevitable tools in nanotechnology. Self-organized construction of advanced materials and devices may be done starting with tailor made nanoparticles as building blocks. Multilayer thin films of gold, zinc sulphide and manganese doped zinc Sulfide nanoparticles were fabricated by a modified polyelectrolyte deposition process, A prerequisite to utilization of colloids for the fabrication of uniform layers is that they remain in suspension and resist unwanted agglomeration. The stability of colloids is generally achieved either by electrostatic stabilization, involving the creation of an electrical double layers arising from ions intentionally adsorbed on the surface of the particle and associated counter ions that surround the particle, or by steric hindrance that is achieved by the adsorption of macromolecules on the surface of the particles. The inherent necessity to introduce electrostatic or steric hindrance to avoid colloidal agglomeration was utilized to induce self-assembly of multilayers applying similar concept used for the layering of polyelectrolytes. Polyacrylic acid was used as the polyanion and chitosan as the polycation for the deposition process. Upto 100 layers of nanoparticles were constructed and films that wore found to be stable and uniform over the substrate. The layer-by-layer deposition of multilayers of several different structures was prepared and devices showing resistive and capacitive electrical characteristics have been fabricated. The onset of electrical conduction in the resistive devices could be varied by introducing a dielectric interlayer between gold nanoparticles and by introducing a gold overlayer on the zinc sulphide nanoparticle devices.

  • 119. Jaisai, Mayuree
    et al.
    Baruah, Sunandan
    Dutta, Joydeep
    Asian Institute of Technology, Thailand; Sultan Qaboos University, Oman.
    Paper modified with ZnO nanorods–antimicrobial studies2012In: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 3, no 1, p. 684-691Article in journal (Refereed)
    Abstract [en]

    Paper with antimicrobial properties was developed through in situ growth of ZnO nanorods. The targeted application for this type of paper is in health centers as wallpaper, writing paper, facemasks, tissue paper, etc. The paper was tested on three model microbes, Gram-positive bacteria Staphylococcus aureus, Gram-negative bacteria Escherichia coli and common airborne fungus Aspergillus niger. No viable bacterial colonies or fungal spores could be detected in the areas surrounding test samples of the antimicrobial paper. Gram-negative bacteria Escherichia coli were found to be inhibited in an area that is 239% and 163% the area of the paper sample under different room lighting conditions, i.e., halogen and fluorescent lamp illumination, respectively. For Gram-positive bacteria Staphylococcus aureus the zones of inhibition surrounding the paper samples are 102% and 70%, and for Aspergillus niger, 224% and 183% of the sample area, under similar lighting conditions.

  • 120. Karim, F.
    et al.
    Bora, T.
    Chaudhari, M. B.
    Habib, K.
    Mohammed, W. S.
    Dutta, Joydeep
    Asian Institute of Technology (AIT), Thailand; Sultan Qaboos University, Oman.
    Optical fiber-based sensor for in situ monitoring of cadmium sulfide thin-film growth2013In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 38, no 24, p. 5385-5388Article in journal (Refereed)
    Abstract [en]

    This work presents a scheme for in situ monitoring of thin-film growth. A fiber-optic sensor based on Fabry-Perot interferometric technique has been established for the first time to monitor in situ growth of thin films. This was applied for determining thickness of cadmium sulfide (CdS) thin films during growth. The fabrication process of CdS film was carried out in 30mMcadmiumacetate and thioacetamide solution at 60°C temperature. The estimated thickness determined during the growth was verified by scanning electron microscopy. This study shows that in situ measurement of the thickness of thin films is feasible by this new technique, and a close match of the estimated thickness was achieved.

  • 121. Karim, Farzia
    et al.
    Bora, Tanujjal
    Chaudhari, Mayur
    Habib, Khalid
    Mohammed, Waleed
    Dutta, Joydeep
    Sultan Qaboos University, Oman.
    Measurement of aluminum oxide film by Fabry-Pérot interferometry and scanning electron microscopy2016In: Journal of Saudi Chemical Society, ISSN 1319-6103Article in journal (Refereed)
    Abstract [en]

    A novel experimental scheme for real time measurement of aluminum oxide film during anodization was developed for the first time. The scheme was established based on a combination of a fiber optic sensor of Fabry-Pérot interferometry and direct current (DC) electrochemical methods. The scheme was assembled in a way to simultaneously anodize the aluminum samples and to measure the thickness of the aluminum oxide film. The anodization process of aluminum sample was carried out in 4% sulfuric acid (H2SO4) solution by the DC methods at room temperature. The estimated thickness of the aluminum oxide film by the novel scheme was verified by scanning electron microscopy (SEM) and electrochemistry measurements. This study shows that real time measurement of the thickness of aluminum oxide film is feasible as it closely matched the thickness determined by SEM and other electrochemistry techniques.

  • 122. Khalid, Mohamed
    et al.
    Bora, Tanujjal
    Ghaithi, Ahmed Al
    Thukral, Sharanjit
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics, Functional Materials, FNM.
    Raman Spectroscopy detects changes in Bone Mineral Quality and Collagen Cross-linkage in Staphylococcus Infected Human Bone.2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, no 1, article id 9417Article in journal (Refereed)
    Abstract [en]

    Diagnosis of osteomyelitis presents a formidable challenge. Lack of pathognomonic clinical sign (s) and diagnostic tests that can diagnose osteomyelitis at an early stage contribute to this difficulty. If the diagnosis is not made early, the disease becomes very difficult to eradicate and can lead to limb threatening and potentially life-threatening complications. Staphylococcus aureus is the most common organism causing osteomyelitis. Raman Spectroscopy provides information about molecular vibration that could potentially be considered as a spectral signature for cellular changes in specific pathologic conditions. In this study we describe a technique using Raman spectroscopy that could potentially be used to diagnose staphylococcal osteomyelitis. Human bone samples were co-cultured with Staphylococcus aureus (S. aureus) and the effects of bacterial growth on bone quality were monitored using Raman spectroscopy. A major drop in the bone mineral quality and crystallinity was observed in the infected bones compared to the controls. S. infection was also found to be cross-linking to the collagen. Our study shows that specific spectral signatures are present for the cause as well as the effect of staphylococcal osteomyelitis, opening the possibility of developing a useful diagnostic modality for early and rapid diagnosis of this condition.

  • 123. Khan, Muahammad Najam
    et al.
    Dutta, Joydeep
    sian Institute of Technology, Thailand; Sultan Qaboos University, Sultanate of Oman.
    Photocatalytic Inactivation of Escherichia Coli using Zinc Stannate Nanostructures under Visible Light2016In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 1131Article in journal (Refereed)
    Abstract [en]

    Zinc stannate (ZnSnO3) nanostructured were synthesized in aqueous media at room temperature. The room temperature synthesis was designed using pourbaix diagrams. The synthesized nanoparticles were checked for their photocatalytic activity for inactivation of model microbe such as Escherichia coli (E.Coli). Photocatalytic activity was observed for zinc stannate (ZTO) in colloidal solution and ZTO deposited on glass slides. Various different concentrations of ZTO nanoparticles were used in slurry form, the bactericidal activity was observed under halogen light, room light and dark conditions. Type of light source and concentration of catalyst were observed to be the two utmost parameters for assessing the efficiency.

  • 124. Khan, Muhammad Najam
    et al.
    Dutta, Joydeep
    Asian Inst Technol, Thailand.
    Comparison of photocatalytic activity of zinc stannate particles and zinc stannate/zinc oxide composites for the removal of phenol from water, and a study on the effect of pH on photocatalytic efficiency2015In: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 36, p. 124-133Article in journal (Refereed)
    Abstract [en]

    Zinc stannate and composite zinc stannate/zinc oxide particles were synthesized by a precipitation method in aqueous media at room temperature. As synthesized particles were characterized by SEM, TEM and XRD. Photocatalytic degradation of 50 ppm phenol in water in the presence of as synthesized particles was studied using the fluorescence decay. Experiments were carried out in both acidic and basic conditions to assess the stability of the catalyst particles and the role of pH on the photocatalytic degradation efficiency. Composite material showed enhanced activity in slightly acidic conditions. Efficiency of photodegradation was observed to be closely related to the isoelectric point of zinc stannate/zinc oxide composites.

  • 125. Khan, Z. A.
    et al.
    Kumar, R.
    Dutta, Joydeep
    Sultan Qaboos University, Oman.
    Effective medium theory applied to colloidal solution of gold nanoparticles and alternating gold-silica multilayer thin film composites2013In: Journal of the Chemical Society of Pakistan, ISSN 0253-5106, Vol. 35, no 2, p. 250-256Article in journal (Refereed)
    Abstract [en]

    Optical modeling of multilayer thin films constructed with oppositely charged nanoparticles help us to understand phenomenon such as surface plasmon resonance, absorbance, transmittance and reflectance. This work reports the application of Maxwell-Garnett effective medium theory in quasi-static limit to colloidal suspensions consisting of host material silica and the inclusion material -gold nanoparticles. Layer-by-layer deposition method was used to self-assemble these nanoparticles to build multilayer composite films. By varying the number and thickness of the layers and the size and spacing of the metal inclusion, a facilitative optical design is modeled to build multilayers of nanosized materials targeted for desired applications.

  • 126. Khan, Zaheer Abbas
    et al.
    Kumar, Rachana
    Dutta, Joydeep
    Asian Institute of Technology, Thailand.
    Multilayer thin films of colloidal gold and silica nanoparticles: Effect of polyelectrolyte coating2012In: Canadian Journal of Chemical Engineering, ISSN 0008-4034, E-ISSN 1939-019X, Vol. 90, no 4, p. 919-924Article in journal (Refereed)
    Abstract [en]

    The use of oppositely charged colloidal nanoparticles to build multilayered structures is an approach in thin film science. In this work, uniform spherical nano-dispersions of gold (ca. 20nm) and silica (ca. 30nm) were synthesised with specific volume concentration to achieve colloidal stability. Exploiting the use of self-assembly, multilayers of these oppositely charged nanoparticles were built using alternate coating with chitosan. Gold nanoparticles have strong optical absorption in visible region of electromagnetic spectrum resulting from its surface plasmon resonance. Silica nanoparticles have low refractive index and absorb light mostly in the ultraviolet (UV) region. The optical absorption band of the fabricated thin films extends from UV to visible region of the electromagnetic spectrum. The spectral characteristics of these thin-film assemblies are a combination of thickness and the order of the layers in a stack. These films have potential applications as optical elements and in optoelectronics.

  • 127. Khan, Zaheer Abbas
    et al.
    Kumar, Rachana
    Mohammed, Waleed S
    Hornyak, Gabor L
    Dutta, Joydeep
    Asian Institute of Technology, Thailand.
    Optical thin film filters of colloidal gold and silica nanoparticles prepared by a layer-by-layer self-assembly method2011In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 46, no 21, p. 6877-6882Article in journal (Refereed)
    Abstract [en]

    A novel fabrication method for optical thin film filters based on the self-organization of alternating layers of colloidal gold and silica nanoparticles (NP) is reported. The filter is designed to work in the deep-UV to visible spectral range. The spectral absorption peaks are tuned by three parameters: the organic capping ligand of the gold NPs (citrate, chitosan, poly (diallyl-dimethylammonium)- chloride or PDDA); the capping environment (bare, chitosan, or PDDA) of the silica NPs and the thickness of the film. Precise control of the transmission color (less than 1% color distance per layer), is achieved by changing the film thickness. Exploitation of the self-assembly process should lead to the facile production of highly reliable large area thin film optical filters at considerably lower costs.

  • 128. Kitsomboonloha, R.
    et al.
    Baruah, S.
    Myint, M. T. Z.
    Subramanian, V.
    Dutta, Joydeep
    Center of Excellence in Nanotechnology School Of Engineering and Technology, Thailan.
    Selective growth of zinc oxide nanorods on inkjet printed seed patterns2009In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 311, no 8, p. 2352-2358Article in journal (Refereed)
    Abstract [en]

    A method for the selective patterning of zinc oxide (ZnO) nanorods is presented that combines inkjet printing of zinc acetate precursors on a substrate used to form ZnO nanocrystallites that subsequently grow into nanorods in a reaction bath containing zinc acetate and hexamethylamine during a hydrothermal process. A total of 100 μm patterns were formed on glass substrates kept at fixed temperatures by printing dots that can also form lines, arrays and rectangular patterns through the use of a 50 μm printhead. Different concentrations of zinc acetate (0.1-1 M) ink-jetted onto the substrates led to the growth of 100 nm to 1 μm wide ZnO nanorods vertically out of the substrates. The length of the ZnO nanorods could be controlled by the concentration of the precursor solution during the hydrothermal process as well as the duration of growth process.

  • 129. Kitsomboonloha, R.
    et al.
    Ngambenjawong, C.
    Mohammed, W. S.
    Chaudhari, M. B.
    Hornyak, G. L.
    Dutta, Joydeep
    Asian Institute of Technology, Thailand.
    Plasmon resonance tuning of gold and silver nanoparticle-insulator multilayered composite structures for optical filters2011In: Micro & Nano Letters, ISSN 1750-0443, E-ISSN 1750-0443, Vol. 6, no 6, p. 342-344Article in journal (Refereed)
    Abstract [en]

    A novel approach for optical filter implementation by tuning the plasmon resonance absorption of gold and silver nanoparticles in layer-by-layer (LBL) composite structures is presented. The LBL composite structures consisted of alternating layers of polyacrylic acid (PAA)-capped Au and PAA-capped Ag bi-layers. The results show clear spectrum tuning of green and blue peaks. Spectrum tuning can be extended when more metals or oxide nanoparticles are incorporated.

  • 130. Kroll, U.
    et al.
    Meier, J.
    Goetz, M.
    Howling, A.
    Dorier, J. -L
    Dutta, Joydeep
    Shah, A.
    Hollenstein, Ch.
    Influence of higher deposition temperature on a-Si:H material properties, powder formation and light-induced degradation, using the VHF (70 MHz) glow discharge technique1993In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 164-166, p. 59-62Article in journal (Refereed)
  • 131. Kumar, Santosh
    et al.
    Boro, Jyotish Chandra
    Ray, Dharitri
    Mukherjee, Avik
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Bionanocomposite films of agar incorporated with ZnO nanoparticles as an active packaging material for shelf life extension of green grape2019In: Heliyon, Vol. 5, no 6, article id e01867Article in journal (Refereed)
  • 132. Kumar, Santosh
    et al.
    Ye, Fei
    Dobretsov, Sergey
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Chitosan Nanocomposite Coatings for Food, Paints, and Water Treatment Applications2019In: Applied Sciences, Vol. 9, no 12Article in journal (Refereed)
    Abstract [en]

    Worldwide, millions of tons of crustaceans are produced every year and consumed as protein-rich seafood. However, the shells of the crustaceans and other non-edible parts constituting about half of the body mass are usually discarded as waste. These discarded crustacean shells are a prominent source of polysaccharide (chitin) and protein. Chitosan is a de-acetylated form of chitin obtained from the crustacean waste that has attracted attention for applications in food, biomedical, and paint industries due to its characteristic properties, like solubility in weak acids, film-forming ability, pH-sensitivity, biodegradability, and biocompatibility. We present an overview of the application of chitosan in composite coatings for applications in food, paint, and water treatment. In the context of food industries, the main focus is on fabrication and application of chitosan-based composite films and coatings for prolonging the post-harvest life of fruits and vegetables, whereas anti-corrosion and self-healing properties are the main properties considered for antifouling applications in paints in this review.

  • 133. Kyaw, H H
    et al.
    Myint, M T Z
    Al-Harthi, S H
    Maekawa, T
    Yanagisawa, K
    Sellai, A
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    The influence of initial gold nanoparticles layer on migration of silver nanoparticles in silver/glass matrix2019In: Thin Solid Films, Vol. 685, p. 216-224Article in journal (Refereed)
    Abstract [en]

    A thin layer of gold nanoparticles (AuNPs) was deposited on glass substrates followed by subsequent deposition of silver nanoparticles (AgNPs) on it. Both AuNPs and AgNPs layers were fabricated by DC magnetron sputtering with inert gas condensation technique. The effect of initial thin layer of AuNPs have on the transformation of AgNPs surface structure by post annealing at 500 degrees C and 600 degrees C in air was investigated. The influence of post annealing temperature on the surface morphology was studied by atomic force microscopy and post annealing at 500 degrees C reduce the size of AgNPs along with the formation of some AgNPs inside the glass matrix. At 600 degrees C, aggregation of AuNPs on the surface was observed and increased in the number of AgNPs that diffused into the glass matrix. X-ray photoelectron spectroscopy was employed to study the surface composition and chemical states. The temperature dependence of Ag diffusion into the glass matrix was characterised and observed by UV-visible absorption spectroscopy and cross sectional transmission electron microscopy. Furthermore, ultraviolet photoelectron spectroscopy revealed a new shoulder related to Au 6 s hybridized with Au 5d and Ag 4d bands in the 1-4 eV regions, which affirmed the metallic character of AgNPs/AuNPs/glass system at higher annealing temperature. By introducing AuNPs on glass prior to AgNPs deposition, novel properties such as limited Ag ion diffusion and evaporation were found and problems previously encountered in AgNPs/glass system were avoided. The proposed AgNPs/AuNPs/glass system can be useful in plasmonic applications such as chroma filters and photonic devices.

  • 134. Kyaw, Htet H.
    et al.
    Al-Harthi, Salim H.
    Sellai, Azzouz
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Self-organization of gold nanoparticles on silanated surfaces2015In: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 6, p. 2345-2353Article in journal (Refereed)
    Abstract [en]

    The self-organization of monolayer gold nanoparticles (AuNPs) on 3-aminopropyltriethoxysilane (APTES)-functionalized glass substrate is reported. The orientation of APTES molecules on glass substrates plays an important role in the interaction between AuNPs and APTES molecules on the glass substrates. Different orientations of APTES affect the self-organization of AuNps on APTES-functionalized glass substrates. The as grown monolayers and films annealed in ultrahigh vacuum and air (600 degrees C) were studied by water contact angle measurements, atomic force microscopy, X-ray photoelectron spectroscopy, UV-visible spectroscopy and ultraviolet photoelectron spectroscopy. Results of this study are fundamentally important and also can be applied for designing and modelling of surface plasmon resonance based sensor applications.

  • 135. Kyaw, Htet Htet
    et al.
    Boonruang, Sakoolkan
    Mohammed, Waleed S.
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Design of electric-field assisted surface plasmon resonance system for the detection of heavy metal ions in water2015In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 5, no 10, article id 107226Article in journal (Refereed)
    Abstract [en]

    Surface Plasmon Resonance (SPR) sensors are widely used in diverse applications. For detecting heavy metal ions in water, surface functionalization of the metal surface is typically used to adsorb target molecules, where the ionic concentration is detected via a resonance shift (resonance angle, resonance wavelength or intensity). This paper studies the potential of a possible alternative approach that could eliminate the need of using surface functionalization by the application of an external electric field in the flow channel. The exerted electrical force on the ions pushes them against the surface for enhanced adsorption; hence it is referred to as “Electric-Field assisted SPR system”. High system sensitivity is achieved by monitoring the time dynamics of the signal shift. The ion deposition dynamics are discussed using a derived theoretical model based on ion mobility in water. On the application of an appropriate force, the target ions stack onto the sensor surface depending on the ionic concentration of target solution, ion mass, and flow rate. In the experimental part, a broad detection range of target cadmium ions (Cd 2+) in water from several parts per million (ppm) down to a few parts per billion (ppb) can be detected.

  • 136. Kyaw, Htet Htet
    et al.
    Bora, Tanujjal
    Dutta, Joydeep
    Asian Institute of Technology, Thailand .
    One-Diode Model Equivalent Circuit Analysis for ZnO Nanorod-Based Dye-Sensitized Solar Cells: Effects of Annealing and Active Area2012In: IEEE transactions on nanotechnology, ISSN 1536-125X, E-ISSN 1941-0085, Vol. 11, no 4, p. 763-768Article in journal (Refereed)
    Abstract [en]

    Electrical characteristics of 1-D zinc oxide (ZnO) nanorod-based dye-sensitized solar cells (DSSCs) were experimentally measured and followed by theoretical analysis using simple one-diode model. Defect sites (mostly oxygen vacancies) in ZnO are typically responsible for lower DSSC performance, which are removed by annealing the ZnO nanorods at high temperatures up to 450 C. The DSSC performances with respect to the different annealing temperatures (250 °C, 350 °C, and 450°C) were determined by measuring their I-V characteristics at 1-sun irradiation (AM 1.5G). The variations in series and shunt resistances of DSSC were estimated by fitting the experimental I-V characteristics with the ideal I-V curve obtained from the one-diode equivalent model of the DSSC. By increasing annealing temperature, reduction in the series resistance R s of the DSSCs with a subsequent increase in the shunt resistance R sh was obtained. Annealing temperature of 350 C was found to be optimum at which maximum DSSC performances with 1-cm 2 cell active area showing minimum R s (0.02 kΩ) with high R sh (1.08 kΩ) values were observed. Reduction in the active area of the DSSCs from 1 to 0.25 cm 2 and further to 0.1 cm 2 demonstrated improved device performance with ∼56% and ∼24% enhancement in the fill factor and open-circuit voltage V oc, respectively, due to the reduced sheet resistance and lower recombination rate resulting low series resistance and high shunt resistance, respectively. At the optimum annealing temperature, maximum DSSC efficiency of 4.60 was obtained for the 0.1-cm 2 cell active area.

  • 137. Kyaw, Htet Htet
    et al.
    Myint, Myo Tay Zar
    Al-Harthi, Salim Hamood
    Maekawa, Toru
    Yanagisawa, Keiichi
    Sellai, Azzouz
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics, Functional Materials, FNM.
    Observation of exchanging role of gold and silver nanoparticles in bimetallic thin film upon annealing above the glass transition temperature2017In: MATERIALS RESEARCH EXPRESS, ISSN 2053-1591, Vol. 4, no 8, article id 086409Article in journal (Refereed)
    Abstract [en]

    The exchange role of gold (Au) and silver (Ag) in bimetallic films co-evaporated onto soda-lime glass substrates with Au-Ag volume ratios of 1:2, 1:1 and 2:1 have been demonstrated. Annealing of the films above the glass transition temperature in air led to non-alloying nature of the films, silver neutrals (Ag-0) and gold nanoparticles (AuNPs) on the surface, along with silver nanoparticles (AgNPs) inside the glass matrix. Moreover, the size distribution and interparticle spacing of the AuNPs on the surface were governed by the Ag content in the deposited film. In contrast, the content of Au in the film played an opposite role leading to the migration of Ag ions (i.e. Ag-0 being transformed to Ag ions after annealing in oxygen ambient) to form AgNPs inside the glass matrix. The higher the Au content in the film is, the more likely Ag-0 to stay on the surface and impacts on the size distribution of AuNPs and consequently on the refractive index sensitivity measurements. Experimental realisation of this fact was reflected from the best performance for localized surface plasmon resonance (LSPR) sensitivity test achieved with Au-Ag ratio of 1:2. The Au/Ag/glass bimetallic dynamic results of this study can be pertinent to sensor applications integrated with optical devices.

  • 138. Laxman, K.
    et al.
    Bora, T.
    Al-Harthi, S. H.
    Dutta, Joydeep
    Asian Institute of Technology, Thailand; Sultan Qaboos University, Oman.
    Improved sensitization of zinc oxide nanorods by cadmium telluride quantum dots through charge induced hydrophilic surface generation2014In: Journal of Nanomaterials, ISSN 1687-4110, E-ISSN 1687-4129, Vol. 2014, article id 919163Article in journal (Refereed)
    Abstract [en]

    This paper reports on UV-mediated enhancement in the sensitization of semiconductor quantum dots (QDs) on zinc oxide (ZnO) nanorods, improving the charge transfer efficiency across the QD-ZnO interface. The improvement was primarily due to the reduction in the interfacial resistance achieved via the incorporation of UV light induced surface defects on zinc oxide nanorods. The photoinduced defects were characterized by XPS, FTIR, and water contact angle measurements, which demonstrated an increase in the surface defects (oxygen vacancies) in the ZnO crystal, leading to an increase in the active sites available for the QD attachment. As a proof of concept, a model cadmium telluride (CdTe) QD solar cell was fabricated using the defect engineered ZnO photoelectrodes, which showed ∼10% increase in photovoltage and ∼66% improvement in the photocurrent compared to the defect-free photoelectrodes. The improvement in the photocurrent was mainly attributed to the enhancement in the charge transfer efficiency across the defect rich QD-ZnO interface, which was indicated by the higher quenching of the CdTe QD photoluminescence upon sensitization.

  • 139. Laxman, K.
    et al.
    Myint, M. T. Z.
    Al Abri, M.
    Al-Gharibi, L.
    Al Namani, B.
    Bourdoucen, H.
    Dutta, Joydeep
    Sultan Qaboos University, Oman.
    Efficient desalination of brackish ground water via a novel capacitive deionization cell using nanoporous activated carbon cloth electrodes2015In: Journal of Engineering Research, ISSN 1726-6009, Vol. 12, no 2, p. 22-31Article in journal (Refereed)
    Abstract [en]

    Sea water intrusion in ground water sources has made brackish water desalination a necessity in Oman. The application of capacitive deionization (CDI) for the deionization of ground water samples from wells in Al-Musanaah Wilayat is proposed and demonstrated. A CDI cell is fabricated using nanoporous activated carbon cloth (ACC) as the electrodes and is shown to be power efficient for desalting ground water samples with total dissolved solids (TDS) of up to 4,000 mg/l. The CDI cell was able to remove up to 73% of the ionic scaling and fouling contaminants from brackish water samples. The power consumption for deionization of brackish water was estimated to be 1 kWh/m3 of desalinated water, which is much lower than the power required to process water with equivalent TDS by the reverse osmosis processes. The CDI process is elaborated, and observations and analysis of the ion adsorption characteristics and electrical properties of the capacitive cell are elucidated.

  • 140. Laxman, K.
    et al.
    Myint, M. T. Z.
    Bourdoucen, H.
    Dutta, Joydeep
    Sultan Qaboos University, Oman.
    Enhancement in ion adsorption rate and desalination efficiency in a capacitive deionization cell through improved electric field distribution using electrodes composed of activated carbon cloth coated with zinc oxide nanorods2014In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 13, p. 10113-10120Article in journal (Refereed)
    Abstract [en]

    Electrodes composed of activated carbon cloth (ACC) coated with zinc oxide (ZnO) nanorods are compared with plain ACC electrodes, with respect to their desalination efficiency of a 17 mM NaCl solution at different applied potentials. Polarization of the ZnO nanorods increased the penetration depth and strength of the electric field between the electrodes, leading to an increase in the capacitance and charge efficiency at reduced input charge ratios. Uniform distribution of the electric field lines between two electrodes coated with ZnO nanorods led to faster ion adsorption rates, reduced the electrode saturation time, and increased the average desalination efficiency by ∼45% for all applied potentials. The electrodes were characterized for active surface area, capacitance from cyclic voltammetry, theoretical assessment of surface area utilization, and the magnitude of electric field force acting on an ion of unit charge for each potential.

  • 141. Laxman, Karthik
    et al.
    Al Gharibi, Laila
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM. Sultan Qaboos University, Oman.
    Capacitive deionization with asymmetric electrodes: Electrode capacitance vs electrode surface area: Electrode capacitance vs electrode surface area2015In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 176, p. 420-425Article in journal (Refereed)
    Abstract [en]

    Asymmetry of electrodes on the equilibrium salt adsorption capacity in a capacitive configuration was studied. Experiments were carried out by using activated carbon cloth (ACC) with a specific surface area and specific capacitance of similar to 1000 m(2)/g and 44 F/g as the anode and ACC coated with zinc oxide nanorods (ZnO NR) with a specific surface area and specific capacitance of 637 m(2)/g and 57 F/g as the cathode. The electrodes were characterized electrically and their salt adsorption capacities measured for various anode-cathode configurations to conclude that for multimodal electrodes, specific capacitance and not specific surface area regulates the salt adsorption capacity. The adsorption trends were analyzed and equated to an electrical model to qualitatively predict the equilibrium salt adsorption capacity, where the smaller capacitance was observed to be the limiting factor. The results in this work are especially useful for practical CDI units, where anode-cathode capacitance should be matched to achieve maximum salt removal efficiency.

  • 142.
    Laxman, Karthik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Functional Materials, FNM.
    Husain, Afzal
    Sultan Qaboos Univ, Coll Engn, Dept Mech & Ind Engn, POB 33, Muscat 123, Oman..
    Nasser, Asma
    Sultan Qaboos Univ, Nanotechnol Res Ctr, POB 17, Muscat 123, Oman..
    Al Abri, Mohammed
    Sultan Qaboos Univ, Nanotechnol Res Ctr, POB 17, Muscat 123, Oman.;Sultan Qaboos Univ, Petr & Chem Engn Dept, Coll Engn, POB 33, Muscat 123, Oman..
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics, Functional Materials, FNM.
    Tailoring the pressure drop and fluid distribution of a capacitive deionization device2019In: Desalination, ISSN 0011-9164, E-ISSN 1873-4464, Vol. 449, p. 111-117Article in journal (Refereed)
    Abstract [en]

    The performance of a capacitive deionization (CDI) device is governed by complex relations between the electrode material properties, fluid velocity and fluid distribution within the device. In order to maximize fluid (water) interaction with the electrodes, the relationships between fluid flow and electrode material properties are explored here to develop novel CDI architectures which reduce the pressure drop, improve surface utilization factor and improve the electrode salt adsorption capacity. Using activated carbon cloth (ACC) as the electrode material, the pressure drop across the CDI device is quantified with respect to flow scheme (flow-between and flow-through CDI modes) used. Computational fluid dynamic (CFD) models are developed to study and optimize the fluid velocity and distribution in order to minimize the device fluid pressure losses. The model predictions are verified by constructing the conceptualized CDI devices and correlating the theoretical and experimentally obtained pressure drops, salt adsorption capacities and fluid flow parameters. The results indicate that up to 60% reduction in pressure drop and similar to 35% increase in specific salt adsorption capacity can be achieved by simple changes to the input-output port architecture of the CDI units. The results describe a method to considerably lower energy consumption in commercial CDI devices.

  • 143.
    Laxman, Karthik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Kimoto, Daiki
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Sahakyan, Armen
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Nanoparticulate Dielectric Overlayer for Enhanced Electric Fields in a Capacitive Deionization Device2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 6, p. 5941-5948Article in journal (Refereed)
    Abstract [en]

    The magnitude and distribution of the electric field between two conducting electrodes of a capacitive deionization (CDI) device plays an important role in governing the desalting capacity. A dielectric coating on these electrodes can polarize under an applied potential to modulate the net electric field and hence the salt adsorption capacity of the device. Using finite element models, we show the extent and nature of electric field modulation, associated with changes in the size, thickness, and permittivity of commonly used nanostructured dielectric coatings such as zinc oxide (ZnO) and titanium dioxide (TiO2). Experimental data pertaining to the simulation are obtained by coating activated carbon cloth (ACC) with nanoparticles of ZnO and TiO2 and using them as electrodes in a CDI device. The dielectric-coated electrodes displayed faster desalting kinetics of 1.7 and 1.55 mg g(-1) min(-1) and higher unsaturated specific salt adsorption capacities of 5.72 and 5.3 mg g(-1) for ZnO and TiO2, respectively. In contrast, uncoated ACC had a salt adsorption rate and capacity of 1.05 mg g(-1) min(-1) and 3.95 mg g(-1), respectively. The desalting data is analyzed with respect to the electrical parameters of the electrodes extracted from cyclic voltammetry and impedance measurements. Additionally, the obtained results are correlated with the simulation data to ascertain the governing principles for the changes observed and advances that can be achieved through dielectric-based electrode modifications for enhancing the CDI device performance.

  • 144. Laxman, Karthik
    et al.
    Myint, Myo Tay Zar
    Al Abri, Mohammed
    Sathe, Priyanka
    Dobretsov, Sergey
    Dutta, Joydeep
    Sultan Qaboos University, Oman.
    Desalination and disinfection of inland brackish ground water in a capacitive deionization cell using nanoporous activated carbon cloth electrodes2015In: Desalination, ISSN 0011-9164, E-ISSN 1873-4464, Vol. 362, p. 126-132Article in journal (Refereed)
    Abstract [en]

    Desalination of brackish water using capacitive deionization (CDI) poses unique challenges attributed to the microbial, organic and other contaminants in water. By using chemically inert and high surface area activated carbon cloth electrodes, the desalination of water from wells in Oman's Al Musanaah wilayat is demonstrated. The ion adsorption characteristics for well water are compared to that of synthetic water (sodium chloride) and their dependence on the charge, size and concentration is investigated. Disinfection properties of the CDI unit were also demonstrated with a 3-fold decrease in viable bacterial cells upon desalination of well water. The power consumption for well water desalination was lower than that of synthetic water with similar salt concentrations and was calculated to be 0.78kWh/m3. The stated desalting capabilities and small footprint make CDI a viable option for remote ground water desalination.

  • 145. Laxman, Karthik
    et al.
    Myint, Myo Tay Zar
    Khan, Rashid
    Pervez, Tasneem
    Dutta, Joydeep
    Sultan Qaboos University, Oman.
    Effect of a semiconductor dielectric coating on the salt adsorption capacity of a porous electrode in a capacitive deionization cell2015In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 166, p. 329-337Article in journal (Refereed)
    Abstract [en]

    A theoretical model was developed to study the effect of an additional dielectric coating on the conducting electrodes in a capacitive deionization cell. The electric field generated at the electrode surface and its distribution was quantitatively investigated for coating materials with different dielectric properties. The model shows that a nanostructured low dielectric and intrinsically polar material like zinc oxide (ZnO) is well suited to enhance the efficiency of capacitive desalination. Electrodes formed by ZnO nanorods coated on conducting electrodes of activated carbon cloth (ACC) were subsequently fabricated and its desalination parameters were studied using a 17 mM (1000 ppm) NaCl solution as the feed at an applied potential of 1.6 V DC. The composite ZnO nanorod coated electrodes improved salt removal efficiency by 40%, and adsorbed 35% of the salt in a single pass experiment, at a charge efficiency of 80% and an electrosorptive capacity of 8.1 mg/g of the electrode. A simultaneous increase in the ion adsorption rate led to a ∼40% reduction in the energy consumption as compared to an uncoated ACC electrode.

  • 146. Laxman, Karthik
    et al.
    Myint, Myo Tay Zar
    Khan, Rashid
    Pervez, Tasneem
    Dutta, Joydeep
    Sultan Qaboos University, Oman.
    Improved desalination by zinc oxide nanorod induced electric field enhancement in capacitive deionization of brackish water2015In: Desalination, ISSN 0011-9164, E-ISSN 1873-4464, Vol. 359, p. 64-70Article in journal (Refereed)
    Abstract [en]

    Ion adsorption in capacitive deionization is a function of the electric field strength present at the electrode surface. We show enhancement in the electric field strength by coating activated carbon cloth (ACC) electrodes with zinc oxide (ZnO) nanorods, where the effective field was shown to vary with respect to the length, diameter and proximity of the coated ZnO nanorods. Deionization of a 17. mM NaCl solution in a single pass experiment using the composite electrodes showed a desalination efficiency of 35%, a 40% improvement as compared to plain ACC electrodes. The composite electrodes also desalinated at a charge efficiency of 78% with a salt uptake of 7.7. mg/g of the electrode. An enhancement in the ion adsorption rate led to a 30% reduction in the energy consumption per mole of salt removed for the desalination process. A theoretical model showing further enhancement in the desalination efficiency by reducing the diameter of the rods is also discussed.

  • 147.
    Laxman, Kunjali Karthik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Al Rashdi, M.
    Al Sabahi, J.
    Al Abri, M.
    Dutta, Joydeep
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Supported versus colloidal zinc oxide for advanced oxidation processes2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 411, p. 285-290Article in journal (Refereed)
    Abstract [en]

    Photocatalysis is a green technology which typically utilizes either supported or colloidal catalysts for the mineralization of aqueous organic contaminants. Catalyst surface area and surface energy are the primary factors determining its efficiency, but correlation between the two is still unclear. This work explores their relation and hierarchy in a photocatalytic process involving both supported and colloidal catalysts. In order to do this the active surface areas of supported zinc oxide nanorods (ZnO NR's) and colloidal zinc oxide nanoparticles (having different surface energies) were equalized and their phenol oxidation mechanism and capacity was analyzed. It was observed that while surface energy had subtle effects on the oxidation rate of the catalysts, the degradation efficiency was primarily a function of the surface area; which makes it a better parameter for comparison when studying different catalyst forms of the same material. Thus we build a case for the use of supported catalysts, wherein their catalytic efficiency was tested to be unaltered over several days under both natural and artificial light, suggesting their viability for practical applications.

  • 148. Lemaire, L.
    et al.
    Scholz, S. M.
    Bowen, P.
    Dutta, Joydeep
    Hofmeister, H.
    Hofmann, H.
    Effect of CuO additives on the reversibility of zirconia crystalline phase transitions1999In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 34, no 9, p. 2207-2215Article in journal (Refereed)
  • 149.
    Loiko, Pavel
    et al.
    ITMO Univ, Kronverkskiy Pr 49, St Petersburg 197101, Russia..
    Bora, Tanujjal
    Sultan Qaboos Univ, Water Res Ctr, Chair Nanotechnol, POB 17, Muscat 123, Oman..
    Maria Serres, Josep
    Univ Rovira & Virgili, Fis & Cristal Log Mat & Nanomat FiCMA FiCNA, Campus Sescelades,C Marcel Li Domingo S-N, E-43007 Tarragona, Spain..
    Mateos, Xavier
    Univ Rovira & Virgili, Fis & Cristal Log Mat & Nanomat FiCMA FiCNA, Campus Sescelades,C Marcel Li Domingo S-N, E-43007 Tarragona, Spain.;Max Born Inst Nonlinear Opt & Short Pulse Spect, Max Born Str 2a, D-12489 Berlin, Germany..
    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..
    Baranov, Alexander
    ITMO Univ, Kronverkskiy Pr 49, St Petersburg 197101, Russia..
    Aguilo, Magdalena
    Univ Rovira & Virgili, Fis & Cristal Log Mat & Nanomat FiCMA FiCNA, Campus Sescelades,C Marcel Li Domingo S-N, E-43007 Tarragona, Spain..
    Diaz, Francesc
    Univ Rovira & Virgili, Fis & Cristal Log Mat & Nanomat FiCMA FiCNA, Campus Sescelades,C Marcel Li Domingo S-N, E-43007 Tarragona, 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..
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Oriented ZnO Nanorods: A Novel Saturable Absorber for Lasers at 1-2 mu m2017In: 2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE & EUROPEAN QUANTUM ELECTRONICS CONFERENCE (CLEO/EUROPE-EQEC), IEEE , 2017Conference paper (Refereed)
  • 150. Loiko, Pavel
    et al.
    Bora, Tanujjal
    Serres, JM
    Mateos, Xavier
    Yu, HH
    Baranov, A
    Aguilo, M
    Diaz, F
    Griebner, U
    Petrov, V
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Oriented ZnO Nanorods: A Novel Saturable Absorber for Lasers at 1-2 μm2017In: 2017 European Conference on Lasers and Electro-Optics and European Quantum Electronics Conference, Optical Society of America, 2017Conference paper (Other academic)
    Abstract [en]

    Nowadays, the development of broadband ultrafast saturable absorbers (SAs) based on carbon nanostructures (e.g., graphene, SWCNTs) and 2D-materials (e.g., MoS2, topological insulators) for passive Q-switching (PQS) and mode-locking (ML) of near-IR lasers (1-2 μm) is attracting a tremendous interest [1]. For PQS, such absorbers can be integrated into compact bulk (microchip) and waveguide lasers providing ns-long pulses at high repetition rates (up to few MHz). Zinc oxide (ZnO) nanostructures exhibit outstanding physical properties and they are used in various photonic applications. In the present work, we demonstrate the potential of ZnO nanorods (NRs) for broadband SAs for near-IR lasers.

12345 101 - 150 of 223
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf