Semiconductor Nanocrystals: A Powerful Visual Aid for Introducing the Particle in a Box

Abstract

For most undergraduate students, introductory quantum chemistry is a challenging subject with many uncommon, if not bizarre, ideas. It is important to relate quantum concepts to the "real" world. Semiconductor quantum dots can be used to introduce and reinforce important points of quantum mechanics and provide real-world applications that exploit quantum phenomena. Most stunning is the colorful demonstration of quantum confinement; few other instances allow direct observation of a quantum effect. Semiconductor nanocrystals can be qualitatively modeled as a particle in a box. This paper presents methods of fabricating nanocrystals, focusing on the pyrolysis of organometallic precursors. The relationship between energy and nanocrystal size is detailed, and the paper closes with an overview of applications of semiconductor nanocrystals.

Photophysics of Individual Single-Walled Carbon Nanotubes

“…As the size of a QD increases, its band edge energy shifts to the red, 123 as demonstrated in Figure 2- …”

“…123 CdSe and CdTe nanoparticles are used in this work as a reference molecule for obtaining single molecule relative QY measurements for SWNTs (Chapter 5). These particular moieties are made up of a few hundred to a few thousand atoms that are arranged in a wurtzite crystal structure.…”

“…To passivate the surface, shelling techniques are routinely used to encase the core of the crystal with a material possessing both a larger band gap (to avoid leaking of carriers into the shell) and a similar lattice constant (to minimize the lattice mismatch between the core and shell). 123 Therefore, ZnS and CdS are often used to shell CdSe and CdTe quantum dots. 124 The photophysical properties of quantum dots are dictated by their size.…”

Binding of Muscimol-Conjugated Quantum Dots to GABAC Receptors

“…The spectrum blue-shifts for smaller dots and red-shifts for larger dots owing to "particle-in-a-box" quantum mechanical properties. 45 The concentration of qdots in this preparation was determined based on a molar extinction coefficient of 6.5 × 10 5 M −1 cm −1 at 600 nm (private communication, M. Bruchez). The derivatization of qdots with the muscimol-and PEG 3400-containing structure (4) and with the PEG 2000-containing structure (7) that lacked muscimol was evaluated by electrophoresis in 1% agarose gels using Tris-acetate-EDTA (TAB) buffer, pH 7.4 (Fig.…”

Entrapment in phospholipid vesicles quenches photoactivity of quantum dots

“…1 Luminescent semiconductor nanocrystal quantum dots (QDs) are of particular interest to many research groups for their ease of chemical manipulation and crystalline structure, which enable the creation of complex assemblies 2,3 and unique photophysical characteristics such as high quantum yield, high molar extinction coefficient, broad excitation spectra and narrow symmetric emission 4 that can be tuned in accordance with particle size, 5 high resistance to chemical and photophysical degradation, and accessibility of outer shell modifications with various biologically active molecules. 6 Just like organic chromophores and fluorophores, QDs possess electronic structure and molecular orbitals.…”