Interactions of cadmium selenide (CdSe) quantum dots with coagulant proteins extracted from Moringa oleifera seeds
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Date
2019
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Abstract
In order to investigate the interaction mechanism between Cadmium selenide (CdSe) quantum dots (QDs) and Moringa oleifera seeds coagulant protein (MOCP), CdSe QDs with hexagonal phase and crystalline size of 3.1-8.1 nm were synthesized in presence of organic solvent Trioctyl-n-phosphine oxide (TOPO) and Trioctyl phosphene (TOP) using colloidal synthesis. The purified mesoporous M. oleifera seeds coagulant protein (MOCP) with a surface area of 8.4134 m2/g, was extracted from M. oleifera seeds. The interaction mechanism between CdSe QDs and MOCP was studied using the Ultraviolet (UV)-vis absorption spectroscopy, fluorescence (FL) emission spectroscopy and the Fourier Transform Infrared spectroscopy (FTIR). The UV-vis absorption spectrum showed an absorption band of CdSe and MOCP at 546.5 nm, with an increase in concentration of MOCP the absorbance intensity decreased. This shows the molecular complexation between CdSe QDs and MOCP in formation of CdSe-MOCP complex. The FL spectroscopy revealed the excitation wavelength of MOCP and CdSe QDs at 302.7 nm and 602.4 nm respectively. The FL intensity of CdSe QDs was found to decrease with an increasing concentration of MOCP, as such it was classified as static quenching mechanisms. Using Stern-Volmer analysis, the binding constants (Kb), quenching constants (Kq) and number of binding sites (n) were determined. The thermodynamic potentials Δ𝐻𝜃(-321.3 kJmol-1); Δ𝑆𝜃( 156.0 JK-1mol-1) and Δ𝐺𝜃(-46.6 kJmol-1) were calculated and gave an indication that the interaction is a results of the electrostatic interactions, hydrophobic and van der waal forces. The stable CdSe-MOCP complex is said to be formed as a results of CdSe QDs adsorbed onto MOCP through electrostatics interaction and surface bound complexation equilibrium attraction. The CdSe-MOCP can be studied for application in water treatment, labeling agent and as sensors.
Description
A mini thesis submitted in partial fulfillment of the requirements for the Degree of Master of science (Chemistry)
Keywords
Interaction mechanism between Cadmium selenide, Moringa oleifera seeds coagulant protein, Hexagonal phase and crystalline