The first part of this dissertation discusses GaSe monomer and aggregated particles. GaSe
nano-disks have been prepared by several different synthetic methods. A study on the effect of
various ligations suggests that well-aggregated stable particles are ligated by tight-binding alkyl
phosphonic acid anhydrides. Addition of dodecyl aldehyde to particles that are primarily ligated
by trioctylphosphine and trioctylphosphine oxide results in strongly coupled aggregates that
cause a large red shift of the absorption spectrum (1600 cm-1) and the reversal of singlet and
triplet states. This spin reversal results in changes in time-resolved anisotropy and a dramatic
decrease in radiative lifetime. The quantum yield of particles increases from 4.7% in monomers
to 61% in strongly coupled aggregates. GaSe aggregates can be mixed with a smectic-A phase
liquid crystal, LC (4-octyl, 4'-cyanobiphenyl), where the liquid crystal forces the particles to
form long stacks that are in line with the director axis of the LC. This only happens when the
synthesized GaSe particles are extremely well-aggregated.
The second part of this dissertation discusses the synthesis and exciton dynamics of
various morphologies of CdTe/CdSe nano-heterostructures. Highly luminescent CdTe spherical
nanoparticles with an average size of 3.4 nm are synthesized using a novel synthetic method that
uses Octadecylphosphonic acid in the Te precursor. These particles can have a quantum yield of
up to 90%. Core/shell and dot/tetrapod CdTe/CdSe heterostructures synthesized from these Te
cores are used to study the biexciton Auger dynamics and the electron cooling rates in these
structures by means of femtosecond transient absorption measurements. An effective mass
approximation (EMA) is used to model the exciton dynamics, specifically Auger times, in these
particles. Calculations of the electron and hole wavefunctions using the EMA model predict
electron and hole overlap and radiative lifetimes that match those of the experimental data. A
better agreement between the experimental and calculated data is observed if compression
effects, resulting from depositing a smaller-lattice shell onto a larger-lattice core, are considered.
The analysis shows that as thicker Se shells are deposited, both the Auger and electron cooling
processes are progressively suppressed, as expected. Calculations show that the Auger time is a
strong function of, and thus directly proportional to the coulombic interaction energy between
the electron and the hole.