In the laboratories of Kyushu University, a massive success of glowing emission from organic material for more than one hour has been achieved. This has opened new horizon of bio-imaging technology.
The scientists have been successful in creating this glowing organic material which is more flexible and transparent in much cheaper and easier method.
In the process, named persistent luminescence, materials which can glow-in-dark slowly releases energy absorbed from ambient light. In commercial fields like emergency signs or dials of watch, the luminescent materials used are inorganic type.
Features of Luminescent materials
Most of these are very rare, expensive and needs more temperature to create them; like europium and dysprosium. They also need scattered light in powder condition. On the contradiction to this glow-in-the-dark carbon based organic compounds can easily overcome these problems.
They are great light emitters and have been already used in OLEDS or organic light-emitting diodes. But the only problem was that long-lasting emission was not possible with these organic compounds. They can emit only for few minutes under indoor lighting at room temperature.
According to, Ryota Kabe, lead author of the report of researchers at Kyushu University’s centre for Organic Photonics and Electronics Research, most of the organic materials are able to absorb from light energy and emit light of different colors yet this process is generally very fast as the energy is directly stored in the molecules that produce the emission.
To get long lasting emission they simply mixed two proper molecules. The film of glowing material is formed by melting the molecules and donating and accepting of electrons. The film of materials emitted for a long time even without intense light source or low temperatures.
As per Ryota Kabe, unlike other glow-in-the-dark materials, the energy in this case has been absorbed as electrical charges which are separated over a large distance. This resulted in slow emission of energy in the form of light.
Light Absorption Method
The scientists have explained the process of light absorption in the same way of positive ion exchange.
The absorption of light gives the electron accepter molecule excess energy, which can easily remove another electron from any electron donor molecule. These extra electrons then gather to other acceptors by moving away from donor, leaving it positively charged.
The charge then gradually come back together, some slowly and some quickly. In this process they release energy that is emitted as light. The span of this is nearly an hour.
The mixing process is same of what is found in solar cells and OLEDs. Like solar cells, the charges have nowhere to escape after building up separately. This forces them to move back and emit light like the OLED.
The only thing is that the difference of charges in the new mixture can stay in a separate state in comparatively long time.