Preparation of magnesium-aluminum layered double hydroxides (MgAl-LDH) and determination of the quantum efficiency of CsSb photocathode on different substrates, 2020

Ikponmwen, Frank O.

2020-05

2020-2029

This dissertation consists of two parts. The first focuses on the synthesis and characterization of Mg2+/Al3+-LDH-DS/S2O82+-•H2O/C3H6OH. The second focuses on the growth and spectral response of CsSb photocathode(s) on Si, Al2O3, TiO2, and SiC. Layered double hydroxides ([MII1- x MIII x (OH)2] (An-)x/m•nH2O) are layered materials known as anionic clays, or hydrotalcite-like compounds started in the early 1980s, has become a class of layered materials having projections and promise in the field of biomaterials, drug delivery, sensors, molecular and imprinting. In this investigation, we approached a method to identify counterfeit drugs in a well-controlled environment, which is an approach that will be cheaper and conducive to society. There are two significant steps in accomplishing this investigation. The first, which is discussed in this project, is intercalating Mg2+/Al3+-LDH-DS/S2O82+-•H2O/C3H6OH in distinct layers that will be inducive for polymerization. One of the significant accomplishments has been to intercalate both sodium dodecyl sulfate and persulfate ions between the layers and for the adsorption of allyl alcohol. We began with synthesizing Mg2+/Al3+-LDH-NO3 with a d-spacing of 7.88Å. The layers increased to 35.9Å when replaced by Mg2+/Al3+-LDH-DS. These preliminary results validate our approach and open the way to developing imprinted polymers that can identify counterfeit drugs. The second part focuses on the growth and spectral response of CsSb photocathodes on Si, Al2O3, TiO2, and SiC. Alkali antimonides are efficient photocathode materials due to their high quantum efficiency compared to other materials. For this reason, a developed technique to better understand the growth and characterization of this material on different substrates. The growth of CsSb photocathodes is dependent on temperature, pressure, and deposition rate to obtain a better quantum efficiency (QE). The drive of this investigation was to explore the growth and spectral response of CsSb photocathodes on Si, Al2O3, TiO2, and SiC along with their corresponding quantum efficiency. The growth thickness was measured using a quartz crystal microbalance (QCB). The results lead to the conclusion that SiC has a QE of 9.7%, which is an improvement compared to Si, Al2O3, TiO2 - because SiC forms a better interface with Cs3Sb because it does not contain oxygen.

text

application/pdf

2020-05

dissertation

Doctor of Philosophy (PhD)

Clark Atlanta University

Department of Chemistry

Khna, Ishrat

Clark Atlanta University

Georgia--Atlanta

http://hdl.handle.net/20.500.12322/cau.td:2020_ikponmwen_frank_o

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