Synthesis and Purification of Silver Nanoparticles for Metal-Enhanced Fluorescence

Silver nanoparticles have many applications due to their surface plasmon resonance which makes them optically active to visible light. When organic dye molecules are close to their surface, the nanoparticles can increase the dye’s fluorescence quantum yield and photostability through metal enhanced fluorescence (MEF). To optimize the effects of MEF, the absorption spectrum of the nanoparticles must overlap the fluorescence spectrum of the dye. Prism-shaped particles enhance MEF through the strong electric fields at their points. To create them, silver perchlorate and sodium citrate were combined in the presence of sodium borohydride. This solution was then exposed to light from green, light-emitting diodes. The pH of the solution was varied to adjust the nanoprism’s size and optical properties. Following preparation, the nanoprisms were purified using centrifugation techniques to have a narrow absorbance peak at around 610 nm. By adjusting the pH and centrifugation parameters, a homogeneous sample of nanoprisms is isolated with the correct absorption wavelength to overlap with the dye’s fluorescence and maximize MEF.