Structural and optical properties of alloyed quaternary CdSeTeS core and CdSeTeS/ZnS core–shell quantum dots

Abstract

Synthesis of fluorescent alloyed quantum dots (QDs) with unique optical properties suitable for a wide array of chemical, physical and biological applications is of research interest. In this work, highly luminescent and photostable alloyed quaternary CdSeTeS core QDs of two different sizes were fabricated via the organometallic hot-injection synthetic route. Characterization of the nanocrystals were performed using TEM, XRD, UV/vis and fluorescence spectrophotometric techniques. We have demonstrated in this work that the well fabricated alloyed quaternary CdSeTeS core QDs possess unique optical properties that are advantageous over conventional core/shell systems. Formation of the CdSeTeS/ZnS core/shell with the desired optical properties comes with a number of challenges, hence the advantages of the quaternary alloyed core over the core/shell QDs are (i) avoidance of the challenging process of determining the proper shell thickness which can provide the desired optical properties in the core/shell system and (ii) avoidance of the lattice-induced mismatch between the core and the shell material which can either lead to incomplete exciton confinement or dislocation at the core/shell interface.

Composition-Tunable Optical Properties of Zn x Cd(1 − x)S Quantum Dot–Carboxymethylcellulose Conjugates: Towards One-Pot Green Synthesis of Multifunctional Nanoplatforms for Biomedical and Environmental Applications

“…Since the bandgap engineering of ternary and quaternary alloyed QDs can be achieved via controlling their composition (relative constituent stoichiometry) in addition to their sizes and internal structures, it is therefore feasible to design and tune their optical properties, which are not readily viable to binary QDs [ 16 – 19 ]. This can be achieved by creating a solid solution (i.e., an alloy) of two semiconductors with different energy gaps, where an increase in the bandgap energy is generally observed with increasing the concentration of the wider bandgap semiconductor, either with cation (i.e., metal constituent) or anion (i.e., chalcogenide constituent) alloyed QDs [ 20 , 21 ]. Nonetheless, the development of QDs based on Zn–Cd–S alloys using one-pot “greener” aqueous processes with biocompatible ligands are narrowly reported in the literature, where the large majority of studies report the production of QDs at high temperatures by organometallic routes, microwave-assisted synthesis, and using toxic organic solvents [ 15 , 17 , 18 , 21 – 25 ].…”

An ultrasensitive SiO2-encapsulated alloyed CdZnSeS quantum dot-molecular beacon nanobiosensor for norovirus

“…Alloyed QDs enable improved flexibility in output efficiency compared to conventional QD systems (Wang et al, 2009;Ma et al, 2009;Caruge et al, 2008). Different alloyed QD cores for ternary and quaternary structures have been reported (Ünlü et al, 2013;Swafford et al, 2006;Adegoke et al, 2015).…”

Development of a Thiol-capped Core/Shell Quantum Dot Sensor for Acetaminophen

“…The significant fluorescence enhancement of CdSe/ZnS QDs is a result of the influence of the larger band gap induced by the ZnS shell which efficiently traps the electrons in the core, and also due to the removal of dangling surface bonds in the QD core upon addition of the shell (Scheme S1). 30 The extinction coefficient of L-cys-CdSe and L-cys-CdSe/ZnS QDs were calculated according to a published method. 31 The concentrations of L-cys-CdSe and L-cys-CdSe/ZnS QDs in Millipore water can be therefore calculated from the Beer-Lambert law.…”