Controlling the size of carbon nanoparticles using hydrothermal method from tender coconut water

A low-cost synthesis of carbon nanoparticles has been developed to support broad application
prospects in optoelectronic devices [1,2]. In this work, the hydrothermal method was used to
prepare carbon nanoparticles from tender coconut (Cocos nucifera) water. A 20 ml solution of
coconut water and the 10 ml solution of coconut water with 10 ml of ethanol were filled to the
hydrothermal reactor chamber and heated to 150 °C for 60 min, 120 min and 180 min.
The resulting solution was centrifuged at 10,000 RPM for 10 min. The particle size was
analyzed using dynamic light scattering method. The optical properties and the structural
properties were investigated using UV-Vis spectrophotometer and Raman spectrometer.
The D band and G band of Raman spectra can be observed from 20 ml solution of coconut
water after reaction for 120 min and 180 min. The ratio of I_G/I_D, corresponding to the
crystallinity of carbon nanoparticles, increased from 1.6 to 1.7 as the reaction time increased
from 120 min to 180 min. The Raman spectra results confirmed that the product of the reaction
was carbon nanoparticles, and the crystallinity of carbon nanoparticles could be improved by
increasing the reaction time. The particle size increased from 383 nm to 8549 nm as the reaction
time increased from 60 min to 180 min. Moreover, the absorbance peak tended to cover the
longer wavelength as increasing reaction time. The increase in particle size and the number of
particles may affect the change in absorbance wavelength. However, all the results confirmed
that the size and crystallinity of carbon nanoparticles could be controlled by the reaction time.
The hydrothermal method is an efficient approach for producing carbon nanoparticles for
optoelectronic applications.