Synthesis and Characterization of Lemon (Citrus limon) Peelings Derived Carbon Quantum Dots-Polyaniline (CQD-Pani) Composites

Abstract

INTRODUCTION

Carbon Quantum Dots (CQDs) are nanoparticles used by researchers in different fields of science. These materials are biocompatible and are conductive at the same time. Polyaniline (Pani) is a conductive polymer that is best known for its property that can synthesize the desired structure and properties of a polymer material. In this study, the two materials are synthesized and characterized together to explore the new properties that these materials could make.

METHODS

Modifications from Sedaghat's (2013) method were used in order to create CQD-Pani composite. First, lemon peelings were used as a carbon source and CQDs were synthesized through the hydrothermal method. The synthesized CQD was centrifuged, then the supernatant was collected. From there, the researchers made concentrations of 4ml, 7ml, and 10ml CQD then were added to Pani to create different concentrations of CQD to Pani. Ammonium Persulfate was then added to the mixture as it serves as an initiator. The polymerization process happened between 0-4°C. These were then characterized using the Scanning Electron Microscope (SEM) for its surface morphology and Fourier Transform Infrared Spectroscopy (FTIR) for the fingerprinting of unknown substances present in the material.

RESULTS

The concentration of 10ml CQD-Pani and Pani were characterized using SEM. Both samples were observed in different magnifications. Under the magnification level of 300,000x, the 10ml CQD-Pani was observed to have "dots" on its surface. These "dots" are agglomerated CQDs on the surface of CQD-Pani while these "dots" are not present in Pani. The CQD-Pani appears to be more fibrous than Pani. The FTIR reported the presence of mainly citric acid across all of the samples which is a component used in the very start of the synthesis. This further validates the role of citric acid from lemon peelings as the carbon source in synthesizing CQDs. The samples also appear to have aromatic rings present in certain regions of the spectra, indicating the presence of aniline since it is a benzene ringed compound. Siloxanes are also present in the Pani.

DISCUSSIONS

From the characterizations done, the addition of CQD to Pani is evident based on the morphological testing. The functional groups used in synthesizing CQD-Pani are found in the samples as well. Siloxanes are present in the control group and were considered as a contaminant and should not be present in that sample. The researchers recommend performing a bioassay and more characterizations to the sample.