Enhanced photoluminescence of InP@ZnS quantum dots induced by increasing the indium myristate-to-tris(trimethylsilyl)phosphine molecular precursors ratio

The synthesis and characterization of InP@ZnS quantum dots (QDs) synthesised by a one-step chemical method without injection of hot precursors are presented. The effect of the ratio of indium myristate-to-tris(trimethylsilyl)phosphine (\(\text{I}\text{n}{\left(\text{M}\text{A}\right)}_{\text{x}}/\text{P}{\left(\text{T}\text{M}\text{S}\right)}_{3}\)) molecular precursors on the structural and optical properties of the QDs were analysed. Using X-ray diffraction was demonstrated that the InP@ZnS QDs have a zinc blende crystalline phase, as was confirmed by High resolution Transmission electron microscope, and the particle sizes were found to range between 3.75 and 9.72 nm with increasing molecular precursor ratio. The observed colour variation of the QDs from yellow to green in toluene is due to the quantum confinement effect, which occurs when the nanocrystal size is smaller than the Bohr exciton radius. The QDs bandgap energy, determined by the absorbance spectroscopy, was found to depend on the \(\text{I}\text{n}{\left(\text{M}\text{A}\right)}_{\text{x}}\) concentration, ranging from 2.90 to 3.21 eV. As the \(\text{I}\text{n}{\left(\text{M}\text{A}\right)}_{\text{x}}/\text{P}{\left(\text{T}\text{M}\text{S}\right)}_{3}\) ratio increases, \(\text{I}\text{n}\text{P}@\text{Z}\text{n}\text{S}\) quantum dots exhibit enhanced photoluminescence due to passivation effects, which is redshifted from 2.91 to 2.19 eV. The temperature-dependent photoluminescence was measured in the range of 20 to 300 K, in which was observed that the photoluminescent bands did not follow the Varshni equation. The obtained results contribute to the understanding of the synthesis and physical properties of \(\text{I}\text{n}\text{P}@\text{Z}\text{n}\text{S}\) QDs, which have potential applications in various fields, such as photovoltaics, bioimaging, and sensing.