![]() demonstrated that multicomponent core/shell CdSe/ZnS/CdS/ZnS QDs can be used as optimal fluorescent probes for the development of systems for cancer diagnosis and treatment using anticancer compounds based on acridine derivatives. Lately, researchers have become of significant interest in studying core-shell QDs based on ZnS/CdS semiconductors, which find a number of applications in photovoltaics, optoelectronics, medicine, and so on. The most used semiconductor compounds to fabricate QDs are those formed by atoms of II–VI, III–V, and IV–VI groups of the periodic table. In a QD, discrete energies depend on size, external fields, band gaps, etc., with which physical and optical properties can be controlled and used for applications in fields such as electronics, medicine, chemistry, and biology. In this work, we focus on studying a kind of core/shell/shell spherical QD, which consists of a semiconductor material surrounded by another one which exhibits a different value of the energy band gap. Īmong the most studied QDs, different geometrical shapes are present: cylindrical, pyramidal, conical, and spherical. These LDSH have found practical realization in nanophotonics and nanoelectronics thanks to controlled fabrication using techniques such as molecular beam epitaxy (MBE), ultrasonic sol-gel, and hydrothermal method, among others with nanostructure sizes below 10 nm. Such features can be controlled by modifying the size and/or the geometry of the system through the application of external electromagnetic probes, hydrostatic pressure, and temperature and also by suitable doping with impurity atoms. In the latter, electrons (holes) are confined in all spatial directions, allowing for electronic properties of great scientific and technological interest. Among these structures it is possible to mention the quantum wells (with charge carrier confinement along one dimension), quantum wires (confinement in two dimensions), and quantum dots (QDs). In accordance, numerous theoretical and experimental studies have been performed. The study of low-dimensional semiconductor heterostructures (LDSH) has gained relevance due to their high-efficient optoelectronic properties. This is reflected in an increase in transition energies. At the moment impurity effects are activated, a decrease in the value of the energies is noted, significantly affecting the ground state, which is more evident for small internal radius. However, dipole matrix moments decrease drastically with the increase of the electric field, leading to a reduction in amplitude of optical responses. When the strength of applied electric field is increased, the opposite effect is observed, since there is a blue-shift of resonances. The same happens when the external magnetic field increases. It is found that transition energy decreases with the growth of internal radius, thus causing the red-shift of resonant peaks. These quantities are related to transitions between the ground and first excited states, with linearly polarized incident radiation along the z-axis. Reported optical properties are the absorption and relative refractive index change coefficients. Calculations included variations of internal dot radius, the application of electric and magnetic fields (both oriented along z-direction), as well as the presence of on-center donor impurity. The corresponding Schrödinger equation was solved using the finite element method via the 2D axis-symmetric module of COMSOL-Multiphysics software. A theoretical analysis of optical properties in a ZnS/CdS/ZnS core/shell/shell spherical quantum dot was carried out within the effective mass approximation.
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