Page 19 - KVIS Book

LIS01I

Why waste it? From Rice Waste to Fluorescent Carbon
Nanoparticles

Thanisorn Oonpitipongsa, Nattasate Tatsaringkansakul, Krittin Thasunthorn
Kamnoetvidya Science Academy, Thailand
Supervisor: Adis Khetubol
Email: thanisorn_o@kvis.ac.th

Rice is one of the most consumed staple food for a large part of the world, especially in Asia.
However, almost 30% of rice from daily meals is wasted. This causes economical losses to many
countries, which is crucial to give extra care. FCNs have become important and have attracted
considerable attention in research and industry. Since FCNs have photoluminescence properties,
i.e. they can emit light from UV to visible region under excitation, synthesized FCNs are
promising for many applications, e.g., bio-imaging and biotechnology, cancer treatment,
chemical sensing, and optoelectronic devices like light emitting diodes. This study reports on a
simple approach toward fluorescent carbon nanoparticles (FCNs) by conventional microwave,
direct heating, and microwave synthesizer route by using cooked rice as a carbon source. To
begin, leftover cooked rice is treated with acid and heated to obtain small molecular sugars
which are examined by Benedict’s test. The unwanted larger molecules are precipitated from the
mixture in the acid-treated process by centrifugation. To synthesize FCNs, the remaining solution
is used as precursors and undergoes 3 synthetic routes: conventional microwave radiation with
various reaction time, direct heating with various reaction time, and microwave synthesizer at
the different temperature with varying choices of acid (Sulfuric acid and Phosphoric acid). The
optical properties of the obtained FCNs are characterized by UV-visible spectrophotometer and
Steady-state fluorescence spectroscopy. The obtained FCNs have shown the emissive properties;
their emission is in blue to green region. Moreover, the redshift in excitation from the
fluorescence spectrophotometer indicates that the nanoparticles are an amorphous structure.
The results also reflect some drawbacks of the applied methods, such as a large distribution of
the particles’ size which is difficult to control, and it is not possible to get the red-emitting FCNs
since the particles precipitate before they have grown to that expected size. For the application,
the obtained carbon nanoparticles are promising for bioimaging because of its fluorescence
property.

Keywords: Fluorescent carbon nanoparticle, Leftover rice, Microwave synthesizer,
Emission spectra