Development of a sample preparation approach to measure the size of nanoparticle aggregates by electron microscopy

TY - JOUR

T1 - Development of a sample preparation approach to measure the size of nanoparticle aggregates by electron microscopy

AU - Dudkiewicz, Agnieszka

AU - Lehner, Angela

AU - Chaudhry, Qasim

AU - Molhave, Kristian

AU - Allmaier, Guenter

AU - Tiede, Karen

AU - Boxall, Alistair B.A.

AU - Hofmann, Peter

AU - Lewis, John

PY - 2018/11/29

Y1 - 2018/11/29

N2 - Electron microscopy (EM) is widely used for nanoparticle (NP) sizing. Following an initial assessment of two sample preparation protocols described in the current literature as “unperturbed”, we found that neither could accurately measure the size of NPs featuring a broad size distribution, e.g., aggregates. Because many real-world NP samples consist of aggregates, this finding was of considerable concern. The data showed that the protocols introduced errors into the measurement by either inducing agglomeration artefacts or providing a skewed size distribution towards small particles (skewing artefact). The focus of this work was to develop and apply a mathematical refinement to correct the skewing artefact. This refinement provided a much improved agreement between EM and a reference methodology, when applied to the measurement of synthetic amorphous silica NPs. Further investigation, highlighted the influence of NP chemistry on the refinement. This study emphasised the urgent need for greater and more detailed consideration regarding the sample preparation of NP aggregates to routinely achieve accurate measurements by EM. This study also provided a novel refinement solution applicable to the size characterisation of silica and citrate-coated gold NPs featuring broad size distributions. With further research, this approach could be extended to other NP types.

AB - Electron microscopy (EM) is widely used for nanoparticle (NP) sizing. Following an initial assessment of two sample preparation protocols described in the current literature as “unperturbed”, we found that neither could accurately measure the size of NPs featuring a broad size distribution, e.g., aggregates. Because many real-world NP samples consist of aggregates, this finding was of considerable concern. The data showed that the protocols introduced errors into the measurement by either inducing agglomeration artefacts or providing a skewed size distribution towards small particles (skewing artefact). The focus of this work was to develop and apply a mathematical refinement to correct the skewing artefact. This refinement provided a much improved agreement between EM and a reference methodology, when applied to the measurement of synthetic amorphous silica NPs. Further investigation, highlighted the influence of NP chemistry on the refinement. This study emphasised the urgent need for greater and more detailed consideration regarding the sample preparation of NP aggregates to routinely achieve accurate measurements by EM. This study also provided a novel refinement solution applicable to the size characterisation of silica and citrate-coated gold NPs featuring broad size distributions. With further research, this approach could be extended to other NP types.

KW - Aggregates

KW - Artefacts

KW - Electron microscopy

KW - Measurement

KW - Nanoparticles

KW - Sample preparation

UR - http://www.scopus.com/inward/record.url?scp=85057402709&partnerID=8YFLogxK

U2 - 10.1016/j.partic.2018.05.007

DO - 10.1016/j.partic.2018.05.007

M3 - Article

AN - SCOPUS:85057402709

SN - 1674-2001

VL - 45

SP - 49

EP - 57

JO - Particuology

JF - Particuology

ER -