Guldpartikler

Guldpartikler, or gold particles, refer to small particles of elemental gold, typically in the range of 1 to 100 nanometers in diameter. They are often described as gold nanoparticles or colloidal gold when suspended in a liquid. Their optical properties arise from the surface plasmon resonance of conduction electrons, causing vivid colors that depend on particle size, shape, and aggregation state. For example, spherical particles around 20 nanometers in water often appear ruby red, while larger particles can appear purple or blue.

Synthesis of guldpartikler is diverse. Common chemical methods include citrate reduction (the Turkevich method), which yields mostly small, spherical particles; the Brust–Schiffrin method, which stabilizes particles with thiols in organic media; and greener approaches using plant extracts. Surface stabilization is crucial, and particles are frequently coated with ligands, polymers, or biomolecules to control stability, prevent aggregation, and enable functionalization for specific applications.

Functionalization and surface chemistry enable a wide range of uses. Gold nanoparticles are employed in biomedical imaging and diagnostics as contrast agents, in photothermal therapy, and as vehicles for targeted drug delivery. They also play a role in biosensing and catalysis, taking advantage of high surface area and catalytic activity of certain nanoparticle shapes.

Characterization methods include UV–visible spectroscopy to observe the plasmon peak, transmission electron microscopy or scanning electron microscopy for size and shape, dynamic light scattering for hydrodynamic size, and measures of zeta potential for stability assessment.

Safety and environmental considerations depend on size, coating, and dose. While generally regarded as biocompatible, comprehensive assessment and proper handling are advised. Colloidal gold has a long history of study, with early experiments by Faraday linking particle size to color and optical behavior.