Insights from in situ and environmental TEM on the oriented attachment of α-Fe2O3 nanoparticles during α-Fe2O3 nanorod formation

Trevor P. Almeida, Michael W. Fay, Thomas Willum Hansen, Yanqiu Zhu, Paul D. Brown

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    Abstract

    Acicular α-Fe2O3 nanorods (NRs), at an intermediate stage of development, were isolated using a snapshot valve-assisted hydrothermal synthesis (HS) technique, for the purpose of complementary in situ transmission electron microscopy (iTEM) and environmental TEM (ETEM) investigations of the effect of local environment on the oriented attachment (OA) of α-Fe2O3 nanoparticles (NPs) during α-Fe2O3 NR growth. Observations of static snapshot HS samples suggested that α-Fe2O3 NPs undergo reorientation following initial attachment, consistent with an intermediate OA stage, prior to ‘envelopment’ with the developing NR to adopt a perfect single crystal. Conversely, the heating of partially developed α-Fe2O3 NRs up to 250 °C, under vacuum, during iTEM, demonstrated the progressive coalescence of loosely packed α-Fe2O3 NPs and the coarsening of α-Fe2O3 NRs, without any direct evidence for an intermediate OA stage. Direct evidence was obtained for the action of an OA mechanism prior to the consumption of α-Fe2O3 NPs at the tips of developing α-Fe2O3 NRs during ETEM investigation, under an He pressure of 5 mbar at 500 °C. However, α-Fe2O3 NPs more strongly attached to the side-walls of developing α-Fe2O3 NRs were more likely to be consumed through a local NP destabilisation and reordering process, in the absence of an OA mechanism. Hence, the emerging ETEM evidence suggests a competition between OA and diffusion processes at the α-Fe2O3 NP coalescence stage of acicular α-Fe2O3 NR crystal development, depending on whether the localised growth conditions facilitate freedom of NP movement.
    Original languageEnglish
    JournalCrystEngComm
    Volume16
    Issue number8
    Pages (from-to)1540-1546
    Number of pages7
    ISSN1466-8033
    DOIs
    Publication statusPublished - 2014

    Bibliographical note

    © The Royal Society of Chemistry 2014

    Cite this

    Almeida, Trevor P. ; Fay, Michael W. ; Hansen, Thomas Willum ; Zhu, Yanqiu ; Brown, Paul D. / Insights from in situ and environmental TEM on the oriented attachment of α-Fe2O3 nanoparticles during α-Fe2O3 nanorod formation. In: CrystEngComm. 2014 ; Vol. 16, No. 8. pp. 1540-1546.
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    title = "Insights from in situ and environmental TEM on the oriented attachment of α-Fe2O3 nanoparticles during α-Fe2O3 nanorod formation",
    abstract = "Acicular α-Fe2O3 nanorods (NRs), at an intermediate stage of development, were isolated using a snapshot valve-assisted hydrothermal synthesis (HS) technique, for the purpose of complementary in situ transmission electron microscopy (iTEM) and environmental TEM (ETEM) investigations of the effect of local environment on the oriented attachment (OA) of α-Fe2O3 nanoparticles (NPs) during α-Fe2O3 NR growth. Observations of static snapshot HS samples suggested that α-Fe2O3 NPs undergo reorientation following initial attachment, consistent with an intermediate OA stage, prior to ‘envelopment’ with the developing NR to adopt a perfect single crystal. Conversely, the heating of partially developed α-Fe2O3 NRs up to 250 °C, under vacuum, during iTEM, demonstrated the progressive coalescence of loosely packed α-Fe2O3 NPs and the coarsening of α-Fe2O3 NRs, without any direct evidence for an intermediate OA stage. Direct evidence was obtained for the action of an OA mechanism prior to the consumption of α-Fe2O3 NPs at the tips of developing α-Fe2O3 NRs during ETEM investigation, under an He pressure of 5 mbar at 500 °C. However, α-Fe2O3 NPs more strongly attached to the side-walls of developing α-Fe2O3 NRs were more likely to be consumed through a local NP destabilisation and reordering process, in the absence of an OA mechanism. Hence, the emerging ETEM evidence suggests a competition between OA and diffusion processes at the α-Fe2O3 NP coalescence stage of acicular α-Fe2O3 NR crystal development, depending on whether the localised growth conditions facilitate freedom of NP movement.",
    author = "Almeida, {Trevor P.} and Fay, {Michael W.} and Hansen, {Thomas Willum} and Yanqiu Zhu and Brown, {Paul D.}",
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    year = "2014",
    doi = "10.1039/c3ce41866a",
    language = "English",
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    Insights from in situ and environmental TEM on the oriented attachment of α-Fe2O3 nanoparticles during α-Fe2O3 nanorod formation. / Almeida, Trevor P.; Fay, Michael W.; Hansen, Thomas Willum; Zhu, Yanqiu; Brown, Paul D.

    In: CrystEngComm, Vol. 16, No. 8, 2014, p. 1540-1546.

    Research output: Contribution to journalJournal articleResearchpeer-review

    TY - JOUR

    T1 - Insights from in situ and environmental TEM on the oriented attachment of α-Fe2O3 nanoparticles during α-Fe2O3 nanorod formation

    AU - Almeida, Trevor P.

    AU - Fay, Michael W.

    AU - Hansen, Thomas Willum

    AU - Zhu, Yanqiu

    AU - Brown, Paul D.

    N1 - © The Royal Society of Chemistry 2014

    PY - 2014

    Y1 - 2014

    N2 - Acicular α-Fe2O3 nanorods (NRs), at an intermediate stage of development, were isolated using a snapshot valve-assisted hydrothermal synthesis (HS) technique, for the purpose of complementary in situ transmission electron microscopy (iTEM) and environmental TEM (ETEM) investigations of the effect of local environment on the oriented attachment (OA) of α-Fe2O3 nanoparticles (NPs) during α-Fe2O3 NR growth. Observations of static snapshot HS samples suggested that α-Fe2O3 NPs undergo reorientation following initial attachment, consistent with an intermediate OA stage, prior to ‘envelopment’ with the developing NR to adopt a perfect single crystal. Conversely, the heating of partially developed α-Fe2O3 NRs up to 250 °C, under vacuum, during iTEM, demonstrated the progressive coalescence of loosely packed α-Fe2O3 NPs and the coarsening of α-Fe2O3 NRs, without any direct evidence for an intermediate OA stage. Direct evidence was obtained for the action of an OA mechanism prior to the consumption of α-Fe2O3 NPs at the tips of developing α-Fe2O3 NRs during ETEM investigation, under an He pressure of 5 mbar at 500 °C. However, α-Fe2O3 NPs more strongly attached to the side-walls of developing α-Fe2O3 NRs were more likely to be consumed through a local NP destabilisation and reordering process, in the absence of an OA mechanism. Hence, the emerging ETEM evidence suggests a competition between OA and diffusion processes at the α-Fe2O3 NP coalescence stage of acicular α-Fe2O3 NR crystal development, depending on whether the localised growth conditions facilitate freedom of NP movement.

    AB - Acicular α-Fe2O3 nanorods (NRs), at an intermediate stage of development, were isolated using a snapshot valve-assisted hydrothermal synthesis (HS) technique, for the purpose of complementary in situ transmission electron microscopy (iTEM) and environmental TEM (ETEM) investigations of the effect of local environment on the oriented attachment (OA) of α-Fe2O3 nanoparticles (NPs) during α-Fe2O3 NR growth. Observations of static snapshot HS samples suggested that α-Fe2O3 NPs undergo reorientation following initial attachment, consistent with an intermediate OA stage, prior to ‘envelopment’ with the developing NR to adopt a perfect single crystal. Conversely, the heating of partially developed α-Fe2O3 NRs up to 250 °C, under vacuum, during iTEM, demonstrated the progressive coalescence of loosely packed α-Fe2O3 NPs and the coarsening of α-Fe2O3 NRs, without any direct evidence for an intermediate OA stage. Direct evidence was obtained for the action of an OA mechanism prior to the consumption of α-Fe2O3 NPs at the tips of developing α-Fe2O3 NRs during ETEM investigation, under an He pressure of 5 mbar at 500 °C. However, α-Fe2O3 NPs more strongly attached to the side-walls of developing α-Fe2O3 NRs were more likely to be consumed through a local NP destabilisation and reordering process, in the absence of an OA mechanism. Hence, the emerging ETEM evidence suggests a competition between OA and diffusion processes at the α-Fe2O3 NP coalescence stage of acicular α-Fe2O3 NR crystal development, depending on whether the localised growth conditions facilitate freedom of NP movement.

    U2 - 10.1039/c3ce41866a

    DO - 10.1039/c3ce41866a

    M3 - Journal article

    VL - 16

    SP - 1540

    EP - 1546

    JO - CrystEngComm

    JF - CrystEngComm

    SN - 1466-8033

    IS - 8

    ER -