Shape Matters: Effect of 1D, 2D, and 3D Isovolumetric Quantum Confinement in Semiconductor Nanoparticles

Abstract

Semiconductor nanoparticles (NPs) are a class of nanoscopic materials with highly tunable optical and electronic properties. The electronic density of states of these NPs depends strongly on both shape and size and has allowed semiconductor NPs to be tailored for applications in various fields including photovoltaics, solid-state lighting, and biological labeling. This work presents investigation of the effect of shape on excitonic properties of electronically excited NPs. Specifically, this work focuses on isovolumetric NPs and addresses the question of how optical properties of NPs are impacted by isovolumetic deformation of NP shapes. The effects of three shapes, representing 1D, 2D, and 3D quantum confinement, for three sizes and four semiconductor materials (CdSe, CdS, CdTe, and PbS) were studied. The electronic excitation in these NPs was described using electron−hole (eh) quasiparticle representation, and exciton binding energies, ehjoint probabilities, and eh-separation distances were calculated using the eh explicitly correlated Hartree−Fock method. The calculations demonstrated that increased anisotropy in the confinement potential resulted in decreased exciton binding energy in the NPs. Within a specific volume, it was found that nanorods exhibited lower exciton binding energies than did nanodisks and that nanodisks exhibited lower exciton binding energies than nanospheres of identical volume. In contrast, the trend for eh-joint probability was found to be opposite that of exciton binding energies. These results demonstrate that a relatively small change in NP structure can result in a substantial change in the excitonic properties of these nanomaterials.

Continuous Hydrothermal Synthesis of Inorganic Nanoparticles: Applications and Future Directions

“…If there is no more material in solution, then the particles obtained may primarily be those from the initial nuclei, which will result in a narrow size distribution and small particles. 116 However, it is possible for NP growth to follow particle nucleation in a number of ways: (1) precursor metal ions from solution can feed to grow the preformed nuclei, or (2) Ostwald ripening can occur (small nuclei that are able to dissolve and then redeposit onto more thermodynamically favorable larger nuclei), and (3) NPs can coalesce to form larger ones.…”

“…Their unique and tunable size-dependent properties (in the range 1–100 nm) make these materials superior and indispensable in many modern technological applications. The significant reduction in size of bulk materials often improves their properties due to quantum confinement effects, giving rise to tunable electronic or other properties . Nanomaterials can also have greatly increased surface area to volume ratios, which can determine the rate of surface area dependent (or defect site controlled) reaction rates.…”

Potential‐Controlled (R)Evolution: Electrochemical Synthesis of Nanoparticles with Well‐Defined Shapes

“…The controlled evolution of nanoparticle surface structure using electrochemical synthetic approaches is emerging as an important contributor to the overall field of well‐defined inorganic nanoparticle synthesis. The intrinsic properties of nanoparticles with well‐defined facets and shapes are desired in applications such as catalysis, [1–5] spectroscopy, [6–7] nanomedicine, [8–11] electronics, [12–14] and energy conversion [15–16] . Meeting the complex needs of emerging and proposed technologies in these areas requires the ability to precisely and deliberately control the shape, surface facet structure, and composition of metal and metal oxide nanoparticles to tune properties such as reactivity, plasmonic response, biological interactions, and conductivity.…”

Two-Dimensional Transition Metal Oxide and Chalcogenide-Based Photocatalysts

“…In many cases, the CB edge will shift toward H 2 reduction potential or the VB edge will shift toward O 2 oxidation potential or both happen simultaneously [ 49 ]. Therefore, the increased thermodynamic driving force is expected according to the Marcus–Gerischer theory [ 50 , 51 ]. Moreover, the unique 2D layered structure can be a suitable matrix to induce some special optical phenomena such as plasmonic effect that possibly extends the absorption range of solar spectrum [ 52 , 53 ].…”