| RESEARCH HIGHLIGHTS |


Fluorescence


INTO THE LIGHT


MODELING THE FLUORESCENCE ENHANCING CAPABILITIES OF MATERIALS PAVES THE WAY FOR MORE SENSITIVE BIOLOGICAL AND CHEMICAL TRACKING TECHNOLOGIES


The capacity of various noble metals and dielectrics to enhance fluorescence has been compared by A*STAR researchers, with a view to realizing more-sensitive technolo- gies to creating new applications in biology and medicine1. Fluorescence occurs when an electron,


after excitation from a fluorophore molecule, drops from the excited state back to its ground state and emits a photon of light. Utilizing this phenomena, fluorescent labe- ling, a highly sensitive and non-destructive technique, allows for binding to a specific region or functional group on a target mole- cule, such as a protein or enzyme. Fluorescent labeling is commonly used for


tracking biological or chemical compounds in mineralogy, forensics and medicine. Its application in DNA sequencing, molecular and cell biology, and the food safety industry is also attracting considerable interest, but relies upon light emitted by a single fluoro- phore, which is generally weak, thwarting its sensitivity. This is pushing the search for technologies


that amplify the fluorescence, spurring Bai Ping and colleagues from the Electronics and Photonics Department at the A*STAR Singapore Institute of High Performance Computing to compare the f luorescence enhancing capabilities of dielectric


16 A*STAR RESEARCH


Fluorescent labeling is a popular technique for tracking chemical compounds in biology, medicine and forensics.


nanoparticles and silver and gold plasmonic metal nanoparticles. “Previously, metals have been used because


they are able to confine the light into a small area, producing a stronger signal,” explains Bai. “But when the metal is placed close to the fluorophore, some of the light is reabsorbed by the metal — called quenching — reducing its f luorescence-enhancing capabilities.” As dielectric materials do not undergo quenching, particularly in the visible light


range, they have also been used; but they have poorer confinement capabilities than metals. “A hybrid that combines the advantages of


both materials is needed,” Bai says. “Our work compares the performance of both materials by taking their structures and operating environments into account, providing for an objective comparison.” Because of the tiny distances between


the materials and the fluorophores, an experimental comparison is very chal- lenging. The researchers used a simulation


ISSUE 6 | JANUARY – MARCH 2017


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