Abstract
Recently, an increasing number of organic compounds including polycyclic aromatic hydrocarbons (PAHs) and nitro-aromatic compounds (NACs) are being released into the environment and most of them are hazardous to living organisms and ecosystems. Thus, the detection of those organic pollutants has become a major concern. Until now various techniques have been used to sense organic pollutants, and such methods have included surface-enhanced Raman spectroscopy (SERS), gas chromatography coupled with mass spectrometry (GC–MS), plasma desorption mass spectrometry (PDMS), energy dispersive X-ray diffraction (EDXRD), and various spectral imaging techniques. However, these conventional methods are not low-cost, not environmentally-friendly, not portable, and not suitable for rapid field detection. Over the past decades, fluorescence technology using organic pollutants detection provides an attractive and promising alternative owing to its unique advantages which include cost-effectiveness, environmentally-friendliness, rapid response and good portability. Therefore, this study explored aqueous synthesis, characterisation and application of CuInS2/ZnS-GO fluorescent probe for the fluorescence detection of the selected organic compounds such as polycyclic aromatic hydrocarbons and nitro-aromatic compounds in aqueous phase. The pollutants are; phenanthrene (Phe), pyrene (Py) and naphthalene (Naph) and trinitrophenol (TNP). A fluorescent nanocomposite was prepared by decorating graphene oxide (GO) with glutathione (GSH)-capped CuInS2/ZnS core/shell quantum dots (QDs). The composite was prepared via in-situ synthesis in which glutathione (GSH) and sodium citrate were used as dual stabilizers. The quantum dots nanocomposite was prepared through non- covalent functionalization of QDs with graphene oxide (GO). The as-synthesized composite was characterised using UV-Vis absorption, photoluminescence (PL) vi spectroscopy, high resolution transmission electron microscopy (HR-TEM), Fourier- transform infrared spectroscopy (FT-IR), Ultraviolet–visible spectroscopy (UV-Vis), X-ray diffraction (XRD) and Raman scattering. The photoluminescence (PL) spectrophotometry revealed the Forster resonance energy transfer (FRET) between the QDs and GO. The Raman scattering revealed the presence of QDs on the GO nanosheets. The TEM showed that the QDs were well distributed on the GO nanosheets. This was in agreement with the UV absorption bands which revealed the excitonic peaks for the QDs and the QDs-GO. In addition, the XRD patterns confirmed the crystalline nature of the as-prepared materials. The sensing studies indicated that the fluorescence intensity of the QDs-GO nanocomposite can be increased by both PAHs and NACs. However, the fluorescence intensity of pristine QDs does not show changes in the presence of PAHs. Though the presence of PAHs in the QDs did not show significant changes in the fluorescence intensity, however, the presence of the NAC, TNP, caused the fluorescence intensity of the QDs to decrease.
M.Sc. (Chemistry)