Chemistry MSc Program Thesis Defence
by Malak Aldajani, Chemistry Masters Candidate
Flocculation Performance of Lignin-Acrylamide Derivatives
September 16, 2019
9:00 AM
ATAC 3004
Committee Members:
Dr. Pedram Fatehi (Supervisor), Dr. Christine Gottardo, Dr. Ebrahim Rezaei, Dr. Hongbin Liu (External)
Everyone is welcome
Abstract
Supramolecular systems are always reversible and characterization of their dynamics is essential to understand and control their function. The kinetics for the association and dissociation processes of the building blocks of interest are measured using fast kinetic techniques. Studies with host systems of increasing complexity will be presented: (i) The characterization of the binding dynamics of a chiral guest with cyclodextrin uncovered the reasons for chiral recognition from the kinetic studies. (ii) Studies with cucurbit[n]urils (CB[n]) showed that the exceptionally high equilibrium constants for guest binding are achieved because the dissociation processes are much slower than observed for other macrocycles. The presence of cations, which can bind to the portals of CB[n]s, and the structure of the guest influence the type of mechanism observed for the guest-CB[n] dynamics. (iii) Bile salt aggregates are host systems with increased complexity because of the presence of binding sites with different properties. Bile salt aggregates in solution and as gels are excellent hosts to solubilize water insoluble functional guests, such as photochromic compounds.( iv) Serum albumins are chiral host systems that were employed to enhance the chiral discrimination of a bimolecular model reaction. Photophysical measurements showed that the highest enantiomeric excess is achieved when the reagent is bound to a protein site for which exchange dynamics of the reagent with the aqueous phase is fast, but once bound the reagent is immobile.
ABSTRACT
Due to the depletion of fossil fuels and the serious environmental problems accompanying their combustion, a new form of energy that is clean, renewable, low-cost and a viable alternative to fossil fuels is urgently needed. The direct conversion of sunlight into fuels (i.e. solar fuels), and the degradation of water/air pollutants under sunlight v^th the aid of an artificial photo-catalyst is an attractive prospect, considering that in a single hour the sun delivers energy sufficient for all human activities in an entire year. However, a major challenge lies in designing efficient sunlight-driven photocatalyst system.
Recently, our group has designed a variety of novel nanomaterials with controlled size and shape, which have potential applications in catalysis and photocatalysis. In this talk, I will select three new types of nanocomposites which were recently developed in our group: (i) CdS-titanate-Ni nanocomposites for H2 generation under visible light from water splitting: In this system, the intimate contact between CdS nanoparticles and titanate nanodiscs as well as Ni selectively located on the titanate surface, as a key role for high H2 generation will be discussed, (ii) 3D-hollow Au/Ti02 nanospheres for air depollution under sunlight: This designed photocatalyst possesses several exceptional properties including high surface area, photonic behavior, multiple light scattering and strong visible-light absorption, owing to its unique structure. As a result, an excellent photo-activity for air depollution has been achieved, (iii) Hollow double-shell Ti02/electron storage material (ESM) system for air depollution both under sunlight and in the dark: To overcome the drawback of photocatalysis that they can only function under light irradiation, we designed a new system which possesses large sunlight absorption and high electron storage capacity. Photo-excited electrons are stored in the day light and further discharged in the dark to form H2O2 for organic pollutant degradation. Thus, this system can function both during the day and during the night. The design of this type of materials will be discussed. In addition, the potential applications of these materials in photocatalysis will be also highlighted.
