Loading...
Green synthesis of cadmium telluride type II multi shell quantum dots for biolabelling
Author(s)
Ncapayi, Vuyelwa
Date Issued
2016
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
The synthesis of water soluble CdTe, CdTe/CdSe and CdTe/CdSe/ZnSe
nanoparticles (NPs) and their optical, cytotoxicity as well as imaging properties are
presented. The synthesis was carried out under ambient conditions in the absence of
an inert environment and involved the use of potassium tellurite (K2TeO3) and sodium
selenosulphate (Na2SeSO4) as a stable tellurium and selenium precursor
respectively, while mercaptopropanoic acid (MPA) was used as capping agents. In
this method, the CdTe NPs were prepared by the addition of tellurium source solution
to MPA-cadmium complex solution at different pH while keeping other parameters
constant. The formation of the shell (CdSe) and multi shell (CdSe/ZnSe) were
achieved by adding desired precursors to the growing CdTe core NPs at one hour
interval. The temporal evolution of the optical properties and stability of the growing
nanocrystals was monitored in detail by varying the refluxing time, pH and storing the
NPs under ambient condition for several days. The as-prepared NPs were
characterised using UV-Vis absorption and photoluminescence (PL) spectroscopy,
transmission electron microscopy (TEM) and high resolution transmission electron
microscopy (HRTEM). The formation of the shells was indicated by an immediate
change in the colour of the reaction solutions after the addition of the desired
precursor and the shift in the absorption wavelength towards red-region. The optical
analyses showed an enhancement in the fluorescent intensity after the addition of the
shell solution accompanied by red-shifting of the absorption and emission maximum.
The stability study revealed an increase in the emission intensity as the ageing days
increased. The stability study of the NPs in air at room temperature show highly
improved stability of the core-shell NPs than the core. The TEM analysis showed that the materials are small, monodispersed, spherical and highly crystalline. The
cytotoxicity of the NPs was investigated on LM 8 and KM-Luc/ GFP cell line using an
MTT protocol at different concentrations. The cell viability show significant
improvement after the shell formation with CdTe/CdSe/ZnSe core multi shell NPs
having the highest cell viability at higher concentration (60 μg/mL). Furthermore a
decrease in cytotoxicity is revealed with increase in reaction time, thus NPs prepared
at longer (7 h) reaction time showed lower cytotoxicity compared with those prepared
at shorter (0.5 h) reaction time. The confocal laser microscope image of the cells
after the addition of the as-synthesised NPs confirmed the transfection of the NPs by
KM-Luc/GFP cell line, indicating that the NPs have been endocytosis. This study
demonstrates the great potential of the as-synthesised core-multi shell nanoparticles
for biological and any applications that require efficiency, high fluorescence intensity
and stability.
nanoparticles (NPs) and their optical, cytotoxicity as well as imaging properties are
presented. The synthesis was carried out under ambient conditions in the absence of
an inert environment and involved the use of potassium tellurite (K2TeO3) and sodium
selenosulphate (Na2SeSO4) as a stable tellurium and selenium precursor
respectively, while mercaptopropanoic acid (MPA) was used as capping agents. In
this method, the CdTe NPs were prepared by the addition of tellurium source solution
to MPA-cadmium complex solution at different pH while keeping other parameters
constant. The formation of the shell (CdSe) and multi shell (CdSe/ZnSe) were
achieved by adding desired precursors to the growing CdTe core NPs at one hour
interval. The temporal evolution of the optical properties and stability of the growing
nanocrystals was monitored in detail by varying the refluxing time, pH and storing the
NPs under ambient condition for several days. The as-prepared NPs were
characterised using UV-Vis absorption and photoluminescence (PL) spectroscopy,
transmission electron microscopy (TEM) and high resolution transmission electron
microscopy (HRTEM). The formation of the shells was indicated by an immediate
change in the colour of the reaction solutions after the addition of the desired
precursor and the shift in the absorption wavelength towards red-region. The optical
analyses showed an enhancement in the fluorescent intensity after the addition of the
shell solution accompanied by red-shifting of the absorption and emission maximum.
The stability study revealed an increase in the emission intensity as the ageing days
increased. The stability study of the NPs in air at room temperature show highly
improved stability of the core-shell NPs than the core. The TEM analysis showed that the materials are small, monodispersed, spherical and highly crystalline. The
cytotoxicity of the NPs was investigated on LM 8 and KM-Luc/ GFP cell line using an
MTT protocol at different concentrations. The cell viability show significant
improvement after the shell formation with CdTe/CdSe/ZnSe core multi shell NPs
having the highest cell viability at higher concentration (60 μg/mL). Furthermore a
decrease in cytotoxicity is revealed with increase in reaction time, thus NPs prepared
at longer (7 h) reaction time showed lower cytotoxicity compared with those prepared
at shorter (0.5 h) reaction time. The confocal laser microscope image of the cells
after the addition of the as-synthesised NPs confirmed the transfection of the NPs by
KM-Luc/GFP cell line, indicating that the NPs have been endocytosis. This study
demonstrates the great potential of the as-synthesised core-multi shell nanoparticles
for biological and any applications that require efficiency, high fluorescence intensity
and stability.
Additional information
Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2016
File(s)![Thumbnail Image]()
Loading...
Name
214309878-Ncapayi-V-Mtech-Chemistry-Appsc-2016.pdf
Description
Thesis
Size
8.17 MB
Format
Adobe PDF
Checksum
(MD5):894e0d267a1d94e08bd8ed74abc6dcc3