Presentation on theme: "Synthesis of fluorescent CdSe quantum dots under mild chemical conditions H. N. Rathnaweera and T. G. Chasteen Department of Chemistry."— Presentation transcript:
Synthesis of fluorescent CdSe quantum dots under mild chemical conditions H. N. Rathnaweera and T. G. Chasteen Department of Chemistry
Introduction Quantum Dots (QDs) Quantum dots are extremely small particles made of semiconductor materials, usually ranging from 2-10 nanometers in diameter. QDs were discovered in the early 1980s by Alexie Ekimov in a glass matrix and by Louis E. Brus in colloidal solutions. 2 www.kurzweilai.net (08/15/2014)
Solar cells Biosensors Light emitting diodes Flat-panel displays Photo detectors Lasers blog.light-innovations.com (10.02.13) 3 CdSe Quantum Dots CdSe QDs are used in a wide range of applications
QDs display unique optical and electrical properties due to their size and composition. 4 www.kurzweilai.net (08/15/2014) Quantum dot color depends on its size QDs have an ability to produce fluorescence.
Over the past few years, there was a remarkable progress in synthesizing CdSe QDs using various methods. These methods involve various organic solvents, high temperatures, high pressures and toxic substrates. But There are some disadvantages Poor Biocompatibility Poor Water Solubility 5 Kriegel, I.; Fernandez, J. R.; Wisnet, A.; Zhang, H.; Waurisch, C.; Eychmuller, A.; Dubavik, A.; Govorov, A.O.; Feldmann, J., ACSNANO. 2013, 7, 4367-4377.
Objectives Develop a simple and environmentally friendly method to synthesize glutathione (GSH) capped CdSe QDs under mild chemical conditions. Optimize the synthesis conditions to obtain CdSe QDs within a reasonable time period. 6
Method, Results and Discussion 1.Development of a method to synthesize GSH capped CdSe QDs 2.Optimization of the synthesis conditions to obtain CdSe QDs within a reasonable time period 8
9 1. CdCl 2 2. Borax-citrate buffer 3. Glutathione Method development for synthesis of GSH capped CdSe QDs CdSe QDs Pérez-Donoso, J. M.; Monrás, J. P.; Bravo, D.; Aguirre, A.; Quest, A. F.; Osorio-Román, I. O.; Aroca, R. F.; Chasteen, T. G.; Vásquez, C. C., PloS ONE 2012, 7(1), e30741. 4. Na 2 SeO 3 Keep on water bath 90°C
10 CdSe QDs at 90°C Synthetic mixture – after 2 h under room light Synthetic mixture - after 2 h under trans-illuminator QDs - after 2 h (resuspended in buffer) under trans-illuminator
11 1. CdCl 2 2. Borax-citrate buffer 3. Glutathione Optimization of the synthesis conditions CdSe QDs Pérez-Donoso, J. M.; Monrás, J. P.; Bravo, D.; Aguirre, A.; Quest, A. F.; Osorio-Román, I. O.; Aroca, R. F.; Chasteen, T. G.; Vásquez, C. C., PloS ONE 2012, 7(1), e30741. 4. Na 2 SeO 3 Keep on water bath at different temperatures 30°C, 40°C, 50°C, 60°C and 70°C
1. Temperature and growth time 12 Color variations of CdSe QDs - under trans-illuminator 1 h 3 h5 h7h24 h 48 h 144 h 1 h 3 h 5 h 7 h24 h 48 h 144 h 1 h 3 h 5 h 7 h 24 h 48 h 144 h 30°C 40°C 50°C
13 24 h 48 h 96 h 1 h3 h 5 h7 h 24 h 1 h 3 h5 h 7 h 60°C 70°C Color variations of CdSe QDs - under trans-illuminator
Temperature / o CColor variation range 30 Blue Green 40 Blue Yellow 50 Blue Orange 60 Green Yellow 70 Green Yellow 14 1 h 3 h 5 h 7 h 24 h 48 h 144 h 50°C Temperature and growth time - summary
2. Different reactant concentrations CdCl 2 : Na 2 SeO 3 4:1 CdCl 2 : Na 2 SeO 3 4:2 15 1 h 3 h 5 h 7 h 24 h 48 h 144 h 1 h 3 h 5 h 7 h 24 h 48 h72 h 1 h 3 h 5 h 7 h 24 h 48 h 72 h 1 h 3 h 5 h 7 h 24 h 48 h72 h CdCl 2 : Na 2 SeO 3 4:3 CdCl 2 : Na 2 SeO 3 4:4
Conclusions CdSe QDs were successfully synthesized under mild chemical conditions. The spectral behaviors of QDs depend on temperature and growth time. The most suitable temperature for synthesis of CdSe QDs is 50 0 C with color varying from blue to orange color. Larger size QDs (orange color) can be obtained in a reasonable time period by changing the reactant concentrations. 16
Acknowledgements Supervisor- Dr. Thomas Chasteen, Department of Chemistry Former members of Dr Chasteen’s Research group Mr. Tharaka Wansapura, Ms. Desire Lopez Dr. José Manuel Pérez Donoso, Universidad de Santiago de Chile, Santiago, Chile. Robert A. Welch foundation 17
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