This presentation taking about what is called QUANTUM DOTs and its application as pH Probes for Study of the Enzyme Kinetics. Ala' Naimat - Universidad de Santiago de Compostela - Spain

1. ‫الرحيم‬ ‫الرحمن‬ ‫هللا‬ ‫بسم‬
Profundización en Química Analítica
Quantum Dots as pH Probes for Study of the Enzyme Kinetics
Ala’ Salem Alnaimat
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2. Outlines: Introduction
- What is Quantum Dots (QDs)?
- Properties of QDs
- Applications of QDs
 Objective
 Advantages & Disadvantages
 Methodology
 Results
 conclusions
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3. Introduction
What is Quantum Dots (QDs)?
QDs are luminescent semiconductor nanocrystals of an approximately 2–100 nm
( 10-50 atoms) in diameter.
Properties of QDs:
1- high brightness due to the extinction coefficient
2- broad absorption characteristics and a narrow band width in emission spectra.
3- Longer fluorescence lifetime ranging from 10 - 40 ns compared to the organic dyes.
The Quantum Dot
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4. Applications of QDs:
Computing : increase the performance
and storage of computers
Biology: Cell labelling, cancer therapy, and
lymphocyte immunology
Light emitting devices (LOD): displays industry
Photovoltaic devices: increase the efficiency and reduce
the cost of today's typical silicon Photovoltaic cells.
Security Tags: can be detected using the night-vision goggles
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5. Advantages & Disadvantages of QDs
Advantages: water soluble substances. Compared with the
traditional analytical methods based organic dyes using QDs
as pH probes was found to be a convenient, rapid and specific
method for the kinetics studies.
Disadvantages: QDs may be toxic according to its composition
which includes some heavy metals, and also the degradation of
QDs is still unknown specially inside the living organism.
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6. Objective
QDs were used as pH probe for a reaction kinetic study of the hydrolysis
of glycidyl butyrate catalyzed by porcine pancreatic lipase (PPL)
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7. Methodology
Glycidyl butyrate solution
ZnS QDs solution
Phosphate buffer saline
((PBS) (PPL) Enzyme solution
Incubation at 25˚C
for 1 min.
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8. Results
The fluorescence intensity of ZnS QDs linearly decreases with time increasing, which
indicates that QDs can be successfully used as pH probes for enzyme reaction kinetic
study.Time ( a-j): 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 min
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9. The effect of The emission spectra
of ZnS QDs to different additives.
(a) Ultra pure water; (b) methanol;
(c) PPL; (d) glycidyl butyrate;
(e) glycidol.on the fluorescence
intensity of QDs is investigated
No significant influence of
all these materials on the
fluorescence intensity of QDs
is observed.
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10. conclusions
• The proposed method was found to improve stability,
sensitivity and a monitoring range for determination proton
concentration as compared to the methods based on the organic
dyes.
References:
• Dudu Wua, Zhi Chenb “ZnS quantum dots as pH probes for study of enzyme
reaction kinetics” Enzyme and Microbial Technology 51 (2012) 47– 52.
• Tan Jun, Wang Bochu, Zhu Liancai “ Quantum Dots: A novel tool to discovery”
Pakistan Journal of Biological Science. 9 (5) 917- 922, 2006
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11. Muchas Gracias ….
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