Evaluate the use of nanoparticles for specific purposes
Bonding, structure and the properties of matter • Bulk and surface properties
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Key concepts
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Definition and size-related properties
Nanoparticles are particles with dimensions in the 1–100 nm range. Small size causes a large surface area to volume ratio, which increases the proportion of atoms at the surface and changes chemical reactivity. Size-dependent properties cause changes in melting point, catalytic activity and optical behaviour. Quantum effects appear at the lower nanometre scale and cause altered electronic and optical properties compared with bulk material.
Surface area to volume ratio and reactivity
Increased surface area to volume ratio causes more atoms to be exposed for reactions, which increases reaction rates and catalytic efficiency. Higher reactivity causes improved performance in catalysts, sensors and antimicrobials. Increased surface reactivity causes potential instability and faster degradation or aggregation unless stabilised. Surface coatings or capping agents cause reduced reactivity and change interactions with the environment or biological tissues.
Common nanoparticle types and functional roles
Metal nanoparticles (e.g., silver, gold) cause strong optical and antimicrobial effects and serve in sensing, catalysis and medical applications. Metal oxides (e.g., TiO2, ZnO) cause UV protection and photocatalysis and serve in sunscreens and self-cleaning surfaces. Carbon-based nanoparticles (e.g., fullerenes, carbon nanotubes) cause high strength and electrical conductivity and serve in composite materials and electronics. Magnetic nanoparticles (e.g., iron oxides) cause controllable motion in magnetic fields and serve in separation and targeted delivery.
Assessment criteria for a specified purpose
Assessment uses performance, selectivity, required dose, stability, delivery method and cost as primary criteria. Performance data show effect size and duration; selectivity shows whether the nanoparticle affects only the target without harmful side effects. Limiting factors include required concentration that causes harm, instability or aggregation that reduces effect, delivery challenges that prevent reaching the target, and economic or manufacturing constraints that make the application impractical.
Health, environmental and regulatory limiting factors
Toxicity to cells or organisms causes potential harm when nanoparticles cross biological barriers or generate reactive oxygen species. Persistence and bioaccumulation cause long-term environmental exposure and ecosystem effects. Regulatory frameworks cause constraints on allowable release, product labelling and exposure limits. Evidence of risk from toxicity studies and lifecycle analyses causes regulators to restrict or require mitigation measures.
Evidence types and data interpretation
Quantitative performance data, dose–response curves and reproducible experimental results cause reliable assessment of effectiveness. In vitro toxicity tests cause initial hazard identification; in vivo and ecological studies cause understanding of real-world impacts. Lifecycle analysis and environmental monitoring cause evaluation of long-term fate. Independent replication and standardised methods cause higher confidence in conclusions about suitability for a specified purpose.
Key notes
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