بسم هللا الرحمن الرحيم

Profundización en Química Analítica

Quantum Dots as pH Probes for Study of the Enzyme Kinetics

Ala’ Salem Alnaimat

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Outlines: Introduction

- What is Quantum Dots (QDs)?- Properties of QDs- Applications of QDs

ObjectiveAdvantages & Disadvantages MethodologyResults conclusions

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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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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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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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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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MethodologyGlycidyl butyrate solution

ZnS QDs solution

Phosphate buffer saline

((PBS) (PPL) Enzyme solution

Incubation at 25˚C

for 1 min.

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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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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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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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Muchas Gracias ….

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