Microwave-Assisted Synthesis of Carbon Nanodots from Orange Peels and its Application

Lai, Kei Chin (2020) Microwave-Assisted Synthesis of Carbon Nanodots from Orange Peels and its Application. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

The objective of this study is to synthesis and to study the characteristics of carbon nanodots (C-dots) and its application as a tool for nitrite detection by the photoluminescence method. C-dots have been concerned recently due to their excellent properties and great potential in the applications. Until today, there are various synthetic methods and carbon sources had been used to synthesis C-dots. In this study, orange peels were used as the carbon source with the microwave-assisted method to synthesis C-dots as it is an inexpensive, time saving, and eco-friendly approach. Moreover, to find the optimal condition for C-dots synthesizing, the orange peels were heated under different temperature and reaction time by microwave digester. Also, blending, filtration, heating, centrifugation, and sonication were involved during the process of synthesizing C-dots. After that, the optical properties, functionalities, particle size and zeta potential of C-dots were investigated by photoluminescence (PL) spectroscopy, Fourier transform infrared spectroscopy (FTIR), and Litesizer respectively. It was found that the solution changed from bright yellow to brown colour after heating, indicated the formation of C-dots. Also, the synthesized C-dots possessed PL properties and the condition of 190 ℃ in 1 minute at the excitation wavelength of 440 nm obtained the highest PL intensity against others. The functional groups of C-dots that were determined by FTIR spectroscopy had contributed to the hydrophilic nature of C-dots. For the particle size analysis, a negative result was obtained. Meanwhile, for the zeta potential analysis, the negative value was obtained which indicated the anionic functional groups present on the C-dots and the value located in between the range of -30 to 30 mV showed the unstable of C-dots when applied current. Lastly, during the photoluminescence detection method for nitrite, a higher concentration of nitrite solution resulted in a stronger quenching effect on C-dots.