Researchers at the Institute of Physical Chemistry of the Polish Academy of Sciences have formulated an efficient approach to create chemical-coated carbon nanotubes that can emit red light when subjected to ultraviolet light. Carbon nanotubes have large surface area so as to support the attachment of several molecules, including the ones that can emit light.
A PhD student at the IPC PAS, Valentina Utochnikova, explained that attaching light-emitting molecules to the nanotube directly is not a favorable option, as the latter would highly diminish the luminescence effect.
To decrease the absorption of light, the nanotubes are subjected to temperatures in the range of 140-160ºC in an ionic liquid solution altered using a terminal azido function. Owing to such high temperatures, a thermal reaction occurs and consequently molecules coated nanotubes behave as anchors-links. On one hand, the anchors are fixed to the nanotube surface while on the other hand molecules can be fixed that can emit visible light. Each link carries a positive charge at the free end. These nanotubes are then immersed in another solution, which contains negatively charged lanthanide complex.
These negatively charged europium complexes are captured instantaneously by anchors fixed to nanotubes with positively charged free terminals owing to electrostatic interaction. Individual nanotubes are coated with molecules to release visible light. On reaction completion, the altered nanotubes are then washed and dried to form a sooty powder. When exposed to UV irradiation, the lanthanide complexes attached to nanotubes begin emitting red light instantly. It is necessary to simplify the chemical reactions for creating new light-emitting nanotubes. New nanotubes created by combining good conductivity of charges with high luminescence properties make it suitable for OLED-based technologies.
Source: http://ichf.edu.pl/