Quantum dot applications are numerous and range from photovoltaic devices and lasers, to bio labeling.
Complexities in the electronic band structure of quantum dots create the necessity for analysis techniques that can
accurately and reproducibly provide their absolute band energies. Cyclic voltammetry (CV) is a novel candidate for these
studies and has the potential to become a useful tool in engineering new nanocrystal technology, by providing
information necessary for predicting and modeling interfacial charge transfer to and from quantum dots. Advancing
from previous reports of nanocrystal CV, a carbon paste electrode was utilized in an attempt to increase measured
current by ensuring intimate contact between nanocrystals and the electrode. Our goal was to investigate band energies
and model nanocrystal-molecule electron transfer systems.
The increasing demand for clean, efficient energy has strongly influenced the direction of nanoscale research.
One of the most promising areas of solar energy production lies with cadmium selenide quantum dots (CdSe QDs). As a
means to improve the efficiency of solar energy conversion in QDs, metal nanoparticles have been examined. It has been
shown that in certain systems the presence of these metal nanoparticles increase electron - hole charge separation thus
providing extended times for electron harvesting. Most of the systems currently explored utilize gold nanoparticles,
which is unsurprising due to the vast amount of synthetic methods for these particles and their plasmonic effects on the
QDs. We seek to further examine these unique metal nanoparticle -quantum dot interactions through the study of CdSe
QD - palladium nanoparticle systems. We employ both steady-state and time resolved ensemble fluorescence
spectroscopy to observe the effects of increasing palladium nanoparticle concentrations on both the fluorescence
intensity and lifetime of various CdSe QDs. We find that decreasing separation distance between the particles through increasing palladium concentration, leads to a stronger interaction between the particles. We find expected fluorescence quenching of the QDs at higher concentrations of palladium. At low palladium concentrations however we observe a unique fluorescence enhancement of the QDs. We use this data to explore the relative contributions of energy and electron transfer between the particles and determine the conditions under which the maximum effects of these interactions are observed.
We measure the concentration of single-walled nanotubes (SWNTs) present in aqueous suspensions by a technique that involves surfactant removal followed by high-temperature oxidation and mass spectroscopy of the resulting products. We also analyze the shift in SWNT emission energy evident from photoluminescence excitation spectroscopy as the surfactant molecule is changed. Next we study spectroscopic changes as surfactant is gently removed by dialysis.