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Charge Transfer Dynamics Interfacially Engineered Metal Chalcogenide/Oxide Quantum Dots for Photoresponsive Devices.

Thesis Info

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Author

Saeed, Shomaila

Program

PhD

Institute

Quaid-I-Azam University

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2019

Thesis Completion Status

Completed

Subject

Chemistry

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/11827/1/SHOMAILA%20SAEED%20chemistry%202019%20qau%20isb%20prr.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676725703778

Similar


In the present work, the synthesis of a series of stable cadmium telluride (CdTe), copper oxide (CuO), zinc selenide (ZnSe) quantum dots (QDs) and CdTe nanoneedles (NNs) has been reported. The nanostructures of CdTe and ZnSe are protected against rapid oxidation by capping with 3-mercaptopropionic acid (MPA), whereas in case of CuO QDs mercaptoacetic acid (MAA) is used as a capping agent. Formation of cadmium and zinc mercaptopropionic acid complex and copper mercaptoacetate complex makes a dense shell on the surface of the nanoparticles. This not only reduces the traps on surface of the QDs, but also acts as a steric fence to control the growth of QDs and create an improved external structure. Two types of the azobenzene photochromes (4-((3-formyl-4-hydroxyphenyl) diazenyl) benzoic acid (FHDBA) and 5-((4-chlorophenyl) diazenyl)-2hydroxybenzaldehyde (CPDHB) are successfully synthesized and attached to the exterior of the synthesized QDs. FHDBA and CPDHB can be switched from trans- to cis-isomer upon UV irradiation and in the dark it reverts to trans-isomer. These two azocompounds work as an effective photoswitch to quench the photoluminescence (PL) of the QDs due to reversible trans to cis interconversion by transferring electron from the conduction band of QDs to the lowest unoccupied molecular orbital (LUMO) of the cis isomer of FHDBA or CPDHB. This suggests that these azo compounds are unique photo-responsive molecules that can offer the opportunity to design fluorescent probes for bioimaging and to design data and energy storage devices. Very fast photoinduced electron transfer (PET) from ZnSe QDs to CdTe NNs has also been observed in the ZnSe QDs attached CdTe NNs (ZnSe QD/CdTe NN nano-hybrid structure) and the efficiency of transfer of electron can be controlled through the quantum confinement of ZnSe QDs. Fast PET from ZnSe QDs to CdTe NNs suggests its applications in the field of solar energy harvesting in photovoltaics. The optical properties of these nanostructures were monitored by UV-Vis, steady-state PL and time-resolved PL studies, while crystalline properties were monitored by XRD and SAED studies. The morphological analysis of these nanostructures is obtained by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution TEM. For the examination of the intermolecular interactions among the organic ligands and inorganic nanostructures Fourier transform infra-red (FT-IR) analysis was carried out.
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