Date of Publication

5-27-2011

Document Type

Master's Thesis

Degree Name

Master of Science in Physics

College

College of Science

Department/Unit

Physics

Thesis Adviser

Gil Nonato C. Santos

Defense Panel Chair

Lydia S. Roleda

Defense Panel Member

Emmanuel T. Rodulfo
Ivan B. Culaba

Abstract/Summary

Horizontal Vapor Phase Crystal Growth Technique was utilized in the synthesis of CdSe quantum dots for optical sensing of copper ions. Thirty five milligrams of CdSe powder with 99.99% purity was used in the synthesis. Growth temperature was set to 6000C, 8000C, 10000C and 12000C, growth time were 6 hours, 8 hours, and 10 hours, ramp time was set to 60 minutes. Scanning electron Microscope (SEM), Energy Dispersive X-ray (EDX), and Applied Spectral Imaging were used to investigate the surface morphology, elemental composition and photoluminescence spectra of the samples respectively. Results showed the successful synthesis of nanospheres, nanoblades, nanoneedles, nanosheets, and quantum dots using HVPC technique. The radii of the grown CdSe quantum dots were 2.19, 2.08, 2.04, and 1.91 nm, for 6000C, 4 hours, 6000C, 4 hours, 8000C, 4 hours and 10000C, 6 hours growth conditions respectively. Growth mechanism of quantum dots was analyzed and SEM micrographs support the Stranski-Krastanov growth mode of self-assembled CdSe quantum dots. An increase in the growth temperature of CdSe nanostructures promoted particle growth and aggregation, resulting to an increase in the size of the structures formed. Energy gaps of the CdSe quantum dots synthesized using HVPC growth technique were 1.749, 2.065, 2.105,2.125, and 2.185 eV. Quantum confinement effect was evident

the increase of energy gap and the blue shift of the emission wavelength peak as radius of quantum dot was decreased. The synthesized CdSe quantum dots were shown to be effective in the optical sensing of concentrations containing copper ions. An increase in copper ion concentration resulted to a continuous quenching of the sample’s fluorescence intensity. Fluorescence quenching mechanism in the study obeyed the Stern-volmer behavior of fluorescence intensity decay.

Abstract Format

html

Language

English

Format

Electronic

Accession Number

CDTG004987

Shelf Location

Archives, The Learning Commons, 12F, Henry Sy Sr. Hall

Physical Description

1 computer optical disc, 4 3/4 in.

Keywords

Quantum dots; Cadmium selenide; Copper ions

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Embargo Period

5-6-2022

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