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Discovery of elusive plasmons in tiny metal particles could yield new, light-activated cancer treatments

Although the physical phenomenon of "plasmon resonance" may be a foreign concept, you have likely appreciated the effect while admiring the stained-glass windows of a cathedral. They derive their color from metal nanoparticles embedded in the glass. When the windows are illuminated, the nanoparticles scatter specific colors depending on the particles' size and geometry

An area of intense research focus, plamsmons are a key driver of engineering at the nanoscale. For more than 50 years, scientists have debated the nature of plasmons at these smallest of scales. Now Stanford engineers have pushed the field of plasmonics into a new realm that could have lasting consequences for catalytic processes such as artificial photosynthesis and cancer research and treatment.

In a study recently published in Nature, researchers show that plasmons exist in smaller particles than had been shown before. The research reveals the presence and clear quantum-influenced nature of plasmons in individual metal particles as small as one nanometer in diameter, about 100 atoms in total. A Stanford Report story published today describes the work and the potential medical applications:

Medical science, for instance, has devised a way to use nanoparticles excited by light to burn away cancer cells, a process known as photothermal ablation. Metal nanoparticles are affixed with molecular appendages that attach exclusively to cancerous cells in the body. When irradiated with infrared light, the plasmons in the metal begin to vibrate and the nanoparticles heat up, burning away the cancer while leaving the surrounding healthy tissue unaffected.

The metal particles used in these applications today, however, are relatively large. The use of smaller particles like those described in this research could prove more easily integrated into cells and might therefore improve the accuracy and the effectiveness of these technologies.

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