Nanoparticles: sizes, risks and uses explained

Bonding, structure, and the properties of matter • Bulk and surface properties

Flashcards

Test your knowledge with interactive flashcards

How can one reduce exposure risk during nanoparticle manufacture?

Click to reveal answer

Engineering controls, closed systems, appropriate PPE and process containment reduce exposure risk.

Key concepts

What you'll likely be quizzed about

Definition of the nanometre scale

The nanometre (nm) equals one billionth of a metre (1 × 10−9 m). Atoms have diameters around 0.1–0.3 nm. Simple molecules span about 0.3–1 nm. Nanoparticles range from 1 nm up to 100 nm, occupying a size band above single molecules but below visible particles. The nanometre provides a quantitative limit that distinguishes molecular-scale matter from particulate nanoscale matter. Limiting factors include shape and aggregation. Particles smaller than 1 nm may behave like large molecules; particles larger than 100 nm begin to show bulk-like behaviour. Aggregation of nanoparticles into clusters increases effective size and reduces surface-area effects.

Surface area to volume ratio and property changes

Surface area to volume ratio increases as particle size decreases. Higher surface area causes more atoms or molecules to lie at the surface relative to the interior, which raises chemical reactivity and changes physical properties such as melting point and colour. Cause: small size produces high surface-area-to-volume. Effect: increased reactivity and altered optical, electrical and mechanical behaviour. Limiting factors include particle coating, shape and environment. Surface treatments or aggregation reduce accessible surface area and mitigate some nanoscale effects.

Possible risks associated with nanoparticles

Small particle size enables uptake by biological systems through inhalation, ingestion or skin contact. Cause: nanoparticles pass cellular barriers more readily than larger particles. Effect: increased potential for cellular interaction, inflammation, oxidative stress and unknown long-term effects. Environmental risks include persistence, accumulation in soils and aquatic systems, and effects on microorganisms. Risk severity depends on dose, exposure route, particle chemistry, surface coating and persistence. Toxicity of a bulk material does not always predict nanoparticle toxicity because surface properties change reactivity.

Evaluating the use of nanoparticles for a specified purpose

Evaluation compares the performance benefits against health, environmental and economic risks. Cause: desired property (for example, increased catalytic activity or stronger composite) motivates nanoparticle use. Effect: assessment requires evidence of improved function, exposure assessment, lifecycle analysis and alternatives appraisal. Consideration includes effectiveness at intended concentration, possible exposure during manufacture, use and disposal, and the availability of safer substitutes. Limiting factors include incomplete toxicology data, regulatory controls, and uncertainty about long-term environmental fate. Decisions use the precautionary principle when data are insufficient.

Key notes

Important points to keep in mind

Nanoparticles measure between 1 nm and 100 nm; atoms and simple molecules are smaller.

High surface-area-to-volume ratio causes increased reactivity and altered physical properties.

Toxicity depends on size, chemistry, surface coating, dose and exposure route.

Aggregation and surface treatment reduce accessible surface area and change behaviour.

Exposure routes include inhalation, ingestion and skin contact; each route alters risk.

Evaluation requires evidence of benefit, exposure assessment, lifecycle analysis and alternatives.

Incomplete long-term data justifies cautious decision-making and preference for safer substitutes.

Mitigation controls include coatings, containment, engineering controls and personal protective equipment.