# What nanoparticles are made of: STEM, ICP-MS and magnetometry

> Six principles for finding what nanoparticles are made of and how their elements are arranged: preparing a TEM grid, HAADF-STEM with its Z-contrast, EDS detectors around the specimen, ICP-MS from acid digestion to the plasma, single-particle ICP-MS and the vibrating-sample magnetometer. Instruments and principles only, with every caption quoted from the cited papers.

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- Updated: 2026-10-14
- Category: Nanomaterial guides
- Method: Composition and structure
- Starting materials: Nanoparticles drop-cast on a grid, digested in acid, or held still in a magnetometer
- Product: Arrangement of the elements in each particle, the metal content, particle mass and number, and the magnetisation
- Key result: Instruments and principles drawn by LabCanvas from the cited papers; no micrograph, spectrum or magnetisation loop is shown
- Figure: 1920 × 1080 px, 45 editable layers (6 generated objects with settings)

## Steps

1. **Preparing a TEM grid**: A drop of the dispersion on a 3 mm Au grid coated with a holey carbon film, the grid on a tissue that absorbed the liquid flowing through the film, left to dry in air for a few minutes; smaller particles tend to settle on the film, biasing TEM sizes toward smaller particles, and aggregates can come from drying (Tuoriniemi 2014)
2. **HAADF-STEM**: Combined with EDX mapping, the atomic-number (Z) contrast of HAADF-STEM characterises how the two metals are arranged in bimetallic Pd–Au particles, and HAADF-STEM tomography shows them in 3D (Tran 2012); Z-contrast can read nanoparticle barcodes built from different elements (Chen 2015)
3. **Mapping the elements**: X-ray (XEDS) detectors can be arranged symmetrically around the specimen; XEDS adds information where Z-contrast is low (Genc 2013)
4. **ICP-MS**: Au nanoparticles and Au–Ag nanoshells were mineralised in aqua regia with HF at 65 °C for 4 h (Faucher 2018); CTAB-capped gold nanorods were decomposed in a microwave with reverse aqua regia and H₂SO₄ (Godoy 2021); tissues were homogenised and lysed with aqua regia (Sonavane 2008). After dilution the liquid is nebulised with argon; the aerosol passes a spray chamber (90–98 % ends as waste) to the plasma (≈ 7500 K), where it is desolvated, vaporised, atomised and ionised, and the ions are separated by mass-to-charge ratio (Resano 2022)
5. **Single-particle ICP-MS**: Each particle that reaches the plasma gives a burst of ions, detected as a short pulse above the background; the pulse intensity is proportional to the mass of the analyte in the particle and the number of pulses to the number concentration; transport efficiency is never 100 % (Resano 2022)
6. **Vibrating-sample magnetometry**: VSM and SQUID magnetometry measure the magnetisation of magnetic nanoparticles under varying magnetic fields and temperatures (Amorim 2025); in lymph nodes the iron content was quantified from the magnetic moment curve with the Langevin model, the tissue fixed tightly and the vibration amplitude kept small (Visscher 2013)

## Limitations

- TEM sizes are biased toward smaller particles, and aggregates can come from drying (Tuoriniemi 2014)
- Not every particle reaches the plasma in single-particle ICP-MS (Resano 2022)

## References

1. Tuoriniemi et al., “Intermethod comparison of the particle size distributions of colloidal silica nanoparticles”, Sci. Technol. Adv. Mater. 2014. https://doi.org/10.1088/1468-6996/15/3/035009 (primary)
2. Tran et al., “Configuration of microbially synthesized Pd–Au nanoparticles studied by STEM-based techniques”, Nanotechnology 2012. https://doi.org/10.1088/0957-4484/23/5/055701 (primary)
3. Genc et al., “XEDS STEM tomography for 3D chemical characterization of nanoscale particles”, Ultramicroscopy 2013. https://doi.org/10.1016/j.ultramic.2013.03.023 (primary)
4. Resano et al., “Living in a transient world: ICP-MS reinvented via time-resolved analysis for monitoring single events”, Chem. Sci. 2022. https://doi.org/10.1039/d1sc05452j (primary)
5. Amorim, “A compendium of magnetic nanoparticle essentials: a comprehensive guide for beginners and experts”, Pharmaceutics 2025. https://doi.org/10.3390/pharmaceutics17010137 (primary)
6. Chen et al., “Rare earth core/shell nanobarcodes for multiplexed trace biodetection”, Anal. Chem. 2015. https://doi.org/10.1021/acs.analchem.5b00944 (further reading)
7. Faucher et al., “Gold and silver quantification from gold-silver nanoshells in HaCaT cells”, J. Trace Elem. Med. Biol. 2018. https://doi.org/10.1016/j.jtemb.2018.01.017 (further reading)
8. Godoy et al., “Evaluating the total gold concentration in metallic nanoparticles with a high content of organic matter through microwave-assisted decomposition platform and plasma-based spectrometric techniques (ICP-MS and ICP OES)”, Talanta 2021. https://doi.org/10.1016/j.talanta.2020.121808 (further reading)
9. Sonavane, Tomoda & Makino, “Biodistribution of colloidal gold nanoparticles after intravenous administration: effect of particle size”, Colloids Surf. B 2008. https://doi.org/10.1016/j.colsurfb.2008.07.004 (further reading)
10. Visscher et al., “Quantitative analysis of superparamagnetic contrast agent in sentinel lymph nodes using ex vivo vibrating sample magnetometry”, IEEE Trans. Biomed. Eng. 2013. https://doi.org/10.1109/TBME.2013.2261893 (further reading)

Credit: Drawn by LabCanvas after Resano et al., Chem. Sci. 2022 (doi:10.1039/d1sc05452j), Tuoriniemi et al., Sci. Technol. Adv. Mater. 2014, Tran et al., Nanotechnology 2012 and Genc et al., Ultramicroscopy 2013, and the papers in the details.

## Questions

**What does the “What nanoparticles are made of: STEM, ICP-MS and magnetometry” template show?** Six principles for finding what nanoparticles are made of and how their elements are arranged: preparing a TEM grid, HAADF-STEM with its Z-contrast, EDS detectors around the specimen, ICP-MS from acid digestion to the plasma, single-particle ICP-MS and the vibrating-sample magnetometer. Instruments and principles only, with every caption quoted from the cited papers.

**What are the steps shown in “What nanoparticles are made of: STEM, ICP-MS and magnetometry”?** 1. Preparing a TEM grid: A drop of the dispersion on a 3 mm Au grid coated with a holey carbon film, the grid on a tissue that absorbed the liquid flowing through the film, left to dry in air for a few minutes; smaller particles tend to settle on the film, biasing TEM sizes toward smaller particles, and aggregates can come from drying (Tuoriniemi 2014). 2. HAADF-STEM: Combined with EDX mapping, the atomic-number (Z) contrast of HAADF-STEM characterises how the two metals are arranged in bimetallic Pd–Au particles, and HAADF-STEM tomography shows them in 3D (Tran 2012); Z-contrast can read nanoparticle barcodes built from different elements (Chen 2015). 3. Mapping the elements: X-ray (XEDS) detectors can be arranged symmetrically around the specimen; XEDS adds information where Z-contrast is low (Genc 2013). 4. ICP-MS: Au nanoparticles and Au–Ag nanoshells were mineralised in aqua regia with HF at 65 °C for 4 h (Faucher 2018); CTAB-capped gold nanorods were decomposed in a microwave with reverse aqua regia and H₂SO₄ (Godoy 2021); tissues were homogenised and lysed with aqua regia (Sonavane 2008). After dilution the liquid is nebulised with argon; the aerosol passes a spray chamber (90–98 % ends as waste) to the plasma (≈ 7500 K), where it is desolvated, vaporised, atomised and ionised, and the ions are separated by mass-to-charge ratio (Resano 2022). 5. Single-particle ICP-MS: Each particle that reaches the plasma gives a burst of ions, detected as a short pulse above the background; the pulse intensity is proportional to the mass of the analyte in the particle and the number of pulses to the number concentration; transport efficiency is never 100 % (Resano 2022). 6. Vibrating-sample magnetometry: VSM and SQUID magnetometry measure the magnetisation of magnetic nanoparticles under varying magnetic fields and temperatures (Amorim 2025); in lymph nodes the iron content was quantified from the magnetic moment curve with the Langevin model, the tissue fixed tightly and the vibration amplitude kept small (Visscher 2013).

**What are the starting materials and the product?** Starting materials: Nanoparticles drop-cast on a grid, digested in acid, or held still in a magnetometer. Product: Arrangement of the elements in each particle, the metal content, particle mass and number, and the magnetisation.

**Which papers is “What nanoparticles are made of: STEM, ICP-MS and magnetometry” based on?** Tuoriniemi et al., “Intermethod comparison of the particle size distributions of colloidal silica nanoparticles”, Sci. Technol. Adv. Mater. 2014 (doi:10.1088/1468-6996/15/3/035009); Tran et al., “Configuration of microbially synthesized Pd–Au nanoparticles studied by STEM-based techniques”, Nanotechnology 2012 (doi:10.1088/0957-4484/23/5/055701); Genc et al., “XEDS STEM tomography for 3D chemical characterization of nanoscale particles”, Ultramicroscopy 2013 (doi:10.1016/j.ultramic.2013.03.023); Resano et al., “Living in a transient world: ICP-MS reinvented via time-resolved analysis for monitoring single events”, Chem. Sci. 2022 (doi:10.1039/d1sc05452j); Amorim, “A compendium of magnetic nanoparticle essentials: a comprehensive guide for beginners and experts”, Pharmaceutics 2025 (doi:10.3390/pharmaceutics17010137); Chen et al., “Rare earth core/shell nanobarcodes for multiplexed trace biodetection”, Anal. Chem. 2015 (doi:10.1021/acs.analchem.5b00944); Faucher et al., “Gold and silver quantification from gold-silver nanoshells in HaCaT cells”, J. Trace Elem. Med. Biol. 2018 (doi:10.1016/j.jtemb.2018.01.017); Godoy et al., “Evaluating the total gold concentration in metallic nanoparticles with a high content of organic matter through microwave-assisted decomposition platform and plasma-based spectrometric techniques (ICP-MS and ICP OES)”, Talanta 2021 (doi:10.1016/j.talanta.2020.121808); Sonavane, Tomoda & Makino, “Biodistribution of colloidal gold nanoparticles after intravenous administration: effect of particle size”, Colloids Surf. B 2008 (doi:10.1016/j.colsurfb.2008.07.004); Visscher et al., “Quantitative analysis of superparamagnetic contrast agent in sentinel lymph nodes using ex vivo vibrating sample magnetometry”, IEEE Trans. Biomed. Eng. 2013 (doi:10.1109/TBME.2013.2261893).

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