The team at Syracuse University’s College of Arts and Sciences believes the system holds promise for future technologies that will convert chemical energy directly to light.
‘The light is extremely bright and efficient,’ said project lead Prof Mathew Maye. ‘We’ve found a new way to harness biology for non-biological applications by manipulating the interface between the biological and non-biological components.’
Fireflies produce light through a chemical reaction between luciferin and its counterpart, the enzyme luciferase. In Maye’s laboratory, the enzyme is attached to the nanorod’s surface; luciferin, which is added later, serves as the fuel. The energy that is released when the fuel and the enzyme interact is transferred to the nanorods, causing them to glow.
‘The trick to increasing the efficiency of the system is to decrease the distance between the enzyme and the surface of the rod and to optimise the rod’s architecture,’ Maye said. ‘We designed a way to chemically attach genetically manipulated luciferase enzymes directly to the surface of the nanorod.’
The nanorods are composed of an outer shell of cadmium sulphide and an inner core of cadmium seleneide. Both are semiconductor metals. Manipulating the size of the core, and the length of the rod, alters the colour of the light that is produced.
The efficiency of the system is measured on a Bioluminescence Resonance Energy Transfer (BRET) scale. The researchers found their most efficient rods (BRET scale of 44) occurred for a special rod architecture (called rod-in-rod) that emitted light in the near-infrared light range. Infrared light has longer wavelengths than visible light and is invisible to the eye. Infrared illumination is important for such things as night-vision goggles, telescopes, cameras and medical imaging.
The firefly-conjugated nanorods currently exist only in the chemistry laboratory. Additional research is ongoing to develop methods of sustaining the chemical reaction — and energy transfer — for longer periods of time and to scale up the system.
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