Browsing by Author "Manohar, M"

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
    Fingerprinting Australian soils based on their source location
    (Elsevier B. V., 2021-03-03) Crawford, J; Cohen, DD; Antancio, AJ; Manohar, M; Siegele, R
    Sampling of PM2.5 has been undertaken twice per week at the Liverpool and Mascot sites (in Sydney, Australia) since 1998. Ion Beam Analysis (IBA) was applied to each sample to determine the concentrations of 21 elements from hydrogen to lead and the black carbon concentration was determined using photon transmission techniques. Sampling days that displayed high and low airborne soil concentrations were identified and three distinct sets of soil fingerprints were determined using Positive Matrix Factorisation (PMF) source apportionment techniques. A fingerprint for all sampling days (representing the average soil fingerprint for each site), a fingerprint corresponding to low soil days associated with local retrained road dust and a fingerprint for high soil days associated with agricultural activities. The ratios of key soil elements (i.e. Si, Al, Fe) displayed larger temporal variation for the high soil days, whereas lower variation was observed for low (local) soil days. Furthermore, it was found that the El Niño-Southern Oscillation (ENSO) affected the concentration of windblown soil dust in the atmosphere. The average soil fingerprint, for all data, was heavily influenced by sampling days containing higher concentrations of soil dust, thus representing the dominant soil type. However, we did observe differences in the K/Fe and Ca/Si ratios to be a distinguishing factor between the average soil fingerprint and the high soil day fingerprint. The Soil fingerprint for the low soil concentration days had a large fraction of black carbon associated with vehicle emissions, represented retrained road dust. © 2021 Turkish National Committee for Air Pollution Research and Control. Production and hosting by Elsevier B.V.
  • No Thumbnail Available
    Item
    MABI - A multi-wavelength absorption black carbon instrument for the measurement of fine light absorbing carbon particles
    (Elsevier, 2021-03-09) Manohar, M; Atanacio, AJ; Button, D; Cohen, DD
    Light absorbing carbon (LAC), also referred to as black carbon (BC) or more colloquially as soot; is generated from the partial combustion of fossil fuels and biomass. The significant research interest in BC is largely due to its aerodynamic diameter well within the 2.5 μm size fraction (known as PM2.5), as well as its abundance being a major constituent of atmospheric particulate matter, particularly in urban regions. Accurately measuring BC is crucial for researchers and regulators for identifying root causes, monitoring emission source concentrations and input into climate change models in order to identify approaches that can best mitigate its atmospheric abundance. This paper presents results from recent studies using a BC research instrument developed by ANSTO, the Multi-wavelength Absorption Black carbon Instrument (MABI). The paper describes in detail the instrument design, function and interpretation of data from measurement of filters collected from various geographical locations in Australia and Asia. This instrument measures the light absorption of LAC particles deposited on filters at seven different wavelengths ranging from 405 to 1050 nm to estimate the LAC concentration of different particle diameters in order to differentiate between LAC from high temperature fossil fuel combustion (such as diesel vehicle engines) and biomass burning. Providing a powerful tool for identifying source contributions and determining LAC content of filters using quantitative analysis. © 2021 Turkish National Committee for Air Pollution Research and Control.
  • No Thumbnail Available
    Item
    Mo-doped, Cr-doped, and Mo–Cr codoped TiO2 thin-film photocatalysts by comparative sol-gel spin coating and ion implantation
    (Elsevier, 2021-02-18) Chen, A; Chen, WF; Majidi, T; Pudadera, B; Atanacio, AJ; Manohar, M; Sheppard, LR; Liu, R; Sorrell, CC; Koshy, P
    Uniformly codoped anatase TiO2 thin films of varying (equal) Mo and Cr concentrations (≤1.00 mol% for each dopant) were fabricated using sol-gel spin coating and deposited on fused silica substrates. All films were annealed at 450 °C for 2 h to recrystallise anatase. Undoped anatase films have been subjected to dual ion implantation for the first time, using Mo, Cr, and sequential Mo + Cr at 1 × 1014 atoms/cm2. The films were characterised by GAXRD, AFM, SIMS, XPS, and UV–Vis and the performance was assessed by dye degradation. Despite the volumetric doping by sol-gel and the directional doping by ion implantation, neither method resulted in homogeneous dopant distributions. Both methods caused decreasing crystallinities and associated partial amorphisation. The XPS signal of the uniformly codoped films is dominated by undissolved dopant ions, which is not the case for the ion-implanted films. Increasing Ti valences are attributed to the fully oxidised condition of the Ti4+ ions that diffuse to the surface from Ti vacancy formation compared to the Ti valence of the bulk lattice, which contains Ti3+. Increasing O valence is attributed to the electronegativity of O2−, which is higher than that of Ti4+. Detailed structural mechanisms for the solubility and energetics mechanisms involve the initial formation of Mo and Cr interstitials that fill the two voids adjacent to the central Ti ion in the TiO6 octahedron, followed by integrated solid solubility (ISS) and intervalence/multivalence charge transfer (IVCT/MVCT). The sequential order of the last two is reversed for the two different doping methods. These two effects are likely to be the source of synergy, if any, between the two dopant ions. The photocatalytic performances of the uniformly codoped films are relatively poor and correlate well with the band gap (Eg). The performances of the ion-implanted films do not correlate with the Eg, where TiO2–Mo performs poorly but TiO2–Cr and TiO2–Mo–Cr outperform the undoped film. These results are interpreted in terms of the competition between the effects of Mo doping, which causes partial amorphisation and/or blockage of active sites, and Cr doping, which may cause Mo–Cr synergism, Cr-based heterojunction formation, and/or improved charge-carrier separation owing to the surface-deposition nature of ion implantation. © 2021 Hydrogen Energy Publications LLC.
  • No Thumbnail Available
    Item
    Role of oxygen vacancy ordering and channel formation in tuning intercalation pseudocapacitance in Mo single-ion-implanted CeO2–x nanoflakes
    (American Chemical Society, 2021-12-07) Zheng, XR; Mofarah, SS; Cen, A; Cazorla, C; Haque, E; Chen, EY; Atanacio, AJ; Manohar, M; Vutukuri, C; Abraham, JL; Koshy, P; Sorrell, CC
    Metal oxide pseudocapacitors are limited by low electrical and ionic conductivities. The present work integrates defect engineering and architectural design to exhibit, for the first time, intercalation pseudocapacitance in CeO2–x. An engineered chronoamperometric electrochemical deposition is used to synthesize 2D CeO2–x nanoflakes as thin as ∼12 nm. Through simultaneous regulation of intrinsic and extrinsic defect concentrations, charge transfer and charge–discharge kinetics with redox and intercalation capacitances together are optimized, where reduction increases the gravimetric capacitance by 77% to 583 F g–1, exceeding the theoretical capacitance (562 F g–1). Mo ion implantation and reduction processes increase the specific capacitance by 133%, while the capacitance retention increases from 89 to 95%. The role of ion-implanted Mo6+ is critical through its interstitial solid solubility, which is not to alter the energy band diagram but to facilitate the generation of electrons and to establish the midgap states for color centers, which facilitate electron transfer across the band gap, thus enhancing n-type semiconductivity. Critically, density functional theory simulations reveal, for the first time, that the reduction causes the formation of ordered oxygen vacancies that provide an atomic channel for ion intercalation. These channels enable intercalation pseudocapacitance but also increase electrical and ionic conductivities. In addition, the associated increased active site density enhances the redox such that the 10% of the Ce3+ available for redox (surface only) increases to 35% by oxygen vacancy channels. These findings are critical for any oxide system used for energy storage systems, as they offer both architectural design and structural engineering of materials to maximize the capacitance performance by achieving accumulative surface redox and intercalation-based redox reactions during the charge/discharge process. © 2021 American Chemical Society
  • No Thumbnail Available
    Item
    Source identification of PM2.5 during the COVID-19 lockdown in Bangkok and the metropolitan region by ion beam analysis (IBA) and positive matrix factorization (PMF) techniques
    (Elsevier B. V., 2023-07) Amphalop, S; Chienthavorn, O; Meesat, R; Tangpong, P; Chutichaisakda, M; Manohar, M; Wilkins, F; Sudprasert, W
    PM2.5 pollution has significant impacts on human health and has been a persistent problem in Bangkok and its metropolitan area for many decades. To effectively address the issue, source identification is crucial. This study was aimed at determining the sources of PM2.5 in three regions; Pathumwan district in Bangkok, Mueang district in Samut Sakhon province, and Mueang district in Samut Prakan province. PM2.5 sampling was performed according to the Federal Reference Method (FRM). A combined total of 135 samples were collected across all three locations, over a 24-h period from December 2021 to February 2022 with 46.2 mm polytetrafluoroethylene (PTFE) membranes. The filters were analyzed using particle accelerator-based ion beam analysis techniques; Proton-induced X-ray emission, proton-induced gamma-ray emission, and proton elastic scattering analysis. Positive matrix factorization was used for source apportionment for the three locations. The results indicated that the main contributors to PM2.5 in Bangkok, Samut Prakan, and Samut Sakhon were biomass/solid waste burning (45.6%), traffic (43.7%), and construction (36.0%), respectively. These preliminary findings further supported the need for expanding these types of studies to implement specific strategies for a reduction of PM2.5 level in high activity cities and which could then be applied to other urban areas around the world. © 2023 Turkish National Committee for Air Pollution Research and Control. Production and hosting by Elsevier B.V.