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Synthesis of CdTe quantum dots and study of their stability. Wansapura, P.T.; Chasteen , T.G.

Synthesis of CdTe quantum dots and study of their stability. Wansapura, P.T.; Chasteen , T.G. Introduction Materials and Methods Results and Discussion Conclusions. Introduction. Quantum dots (QDs) are tiny particles, or “ nanoparticles ” (NPs) .

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Synthesis of CdTe quantum dots and study of their stability. Wansapura, P.T.; Chasteen , T.G.

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  1. Synthesis of CdTe quantum dots and study of their stability.Wansapura, P.T.; Chasteen, T.G.

  2. Introduction • Materials and Methods • Results and Discussion • Conclusions

  3. Introduction

  4. Quantum dots (QDs) are tiny particles, or “nanoparticles” (NPs). • They were discovered at the beginning of the 1980s by Alexei Ekimovand Louis E. Brus. • Traditionally chalcogenides (selenides,tellurides, sulfides) of metals like Cadmium or Zinc (CdSe or ZnS, for example). • Range from 2 to 10 nanometers in diameter.

  5. Because of their small size, quantum dots display unique optical and electrical properties that are different in character from those of the corresponding bulk material. • Emission photons under excitation, is visible to the human eye as light. • The wavelength of these photon emissions depends on the its size. • The ability to precisely control the size of a quantum dot enables the manufacturer to determine the wavelength of the emission, which in turn determines the colour of light the human eye perceives.

  6. Quantum dots can therefore be “tuned” during production to emit any colour of light desired. • The smaller the dot, the closer it is to the blue end of the spectrum, and the larger the dot, the closer to the red end. • Dots can even be tuned beyond visible light, into the infra-red or into the ultra-violet. quarknet.fnal.gov (10.02.13)

  7. QDs exhibit important advantages such as i) Narrow emission spectra, ii) Increased chemical stability, iii) Tunable spectroscopic properties, iv) High quantum yields.

  8. At the end of the production process, quantum dots appear physically either as a powder or in a solution. • Photovoltaicdevices: solarcells • Biology : biosensors, imaging • Light emitting diodes: LEDs • Flat-panel displays • Memory elements • Photodetectors • Lasers openi.nlm.nih.gov (10.02.13) blog.light-innovations.com (10.02.13) european-coatings.com (10.02.13)

  9. CdTe-GSH(Glutathione) Quantum Dots • The idea ofslightly changing the shape of these QDs and hence their opticalproperties has made them very popular in optoelectronics. • CdTe QDs are used in electronic and optoelectronicdevices during the last decade, as an important tool for newsolar cell technology (photovoltaic panels) andbiomedicine.

  10. Materials and Methods

  11. A CdCl2 (4 mM) solution was prepared in 15 mM borax-citratebuffer, (pH 9.0) • Then glutathione (GSH) was added (up to 10 mM final). • After 5 min, potassium tellurite ( K2TeO3) was added at 1 mM (finalconcentration) to produce a 4:10:1 ratio of CdCl2: GSH: K2TeO3. • At this point the solution turned slightly green as result of CdTe‘‘seeds’’ formation. 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.

  12. QDs nucleation was initiated by raising thetemperature up to 900C. • CdTe QD samples were obtained in every hour time intervals. • CdTe-GSH QDs were precipitated with two volumes of ethanol and centrifugedfor 20 min at 12,000 rpm. • Fluorescence spectroscopic data obtained before and after the precipitation. 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.

  13. Dried QDs, QDs in buffer, and QDs in water were stored in under a variety of conditions involving different light intensities and temperatures.( 2hrs incubated QDs ) • 40C (under dark and light conditions), • -800C (under dark conditions), • Under sunlight, • Under room temperature conditions (under dark and light), • Under 1200 lumens bulb (fluorescent bulb), in replicate samples. • Fluorescence spectrometric data were collected and analyzed periodically for three months.

  14. Results and Discussion

  15. Images under room light Freshly prepared QDs 1h 2h 3h 4h 5h 6h After the resuspension of QDs, in the Buffer 1h 2h 3h 4h 5h 6h

  16. 0h 1h 2h 3h 4h 5h 6h Images of QDs in Transilluminator A Freshly prepared QDs B Precipitated QDs C D Dried QDs After the resuspension of QDs, in the Buffer

  17. 2hrs-Dried QDs under room light

  18. 2hrs-Dried QDs on transilluminator(302nm)

  19. QDs in buffer LB SB BB 4dB 4LB -80dB LdB LB SB BB 4dB 4LB -80dB LdB 0th day 10th day 18th day under room light On transilluminator (302nm) 24th day 32nd day 39th day 46th day 76th day LB- Lab, RT, Light / SB- Sunlight / BB- Bulb / 4dB- 40C,dark/ 4LB- 40C,Light / -80dB- -800C,Dark / LdB- Lab, RT, Dark

  20. QDs in water LW SW BW 4dW 4LW -80dW LdW LW SW BW 4dW 4LW -80dW LdW 0th day 10th day 18th day under room light 24th day On transilluminator (302nm) 32nd day 39th day 46th day 76th day LW- Lab, RT,Light/ SW- Sunlight / BW- Bulb / 4dW- 40C,dark/ 4LW- 40C,Light / -80dW- -800C,Dark / LdW- Lab, RT,Dark

  21. Dried QDs in Water LN SN BN 4dN 4LN -80dN LdN LN SN BN 4dN 4LN -80dN LdN 0th day 10th day 18th day under room light 24th day On transilluminator (302nm) 32nd day 39th day 46th day 76th day LN- Lab, RT, Light / SN- Sunlight / BN- Bulb / 4dN- 40C,dark/ 4LN- 40C,Light / -80dN- -800C,Dark / LdN- Lab, RT, Dark

  22. Conclusions

  23. CdTe-GSH QDs were successfully synthesized (solutions and powders). • Spectroscopic data shows that both QDs (solutions and powders) have similar Fluorescence characteristics. • Dried QDs were more stable.(research continued) • Under sunlight QDs in water and buffer showed degradation.(research continued)

  24. Future works…… • Further studies of Fluorescence and Absorbance spectroscopic data. • Stability studies – under different temperatures , dark / light conditions.(research continued) • Inductively coupled plasma atomic emission spectroscopic (ICP-AES),analysis to find out the ratio of Cd/Te in QDs after the degradation.

  25. ACKNOWLEDGEMENTS • Dr. Chasteen’s Research group at Sam Houston State University. • All the academic staff at Sam Houston State University. • Dr. José Manuel Pérez Donoso and Dr. Waldo A. Dıáz-VásquezMicrobiology and BioNanotechnology Research Group Laboratory of Biochemistry Facultadde CienciasQuímicas y Farmacéuticas Universidad de Santiago de Chile, Santiago, Chile. • Ms. Rachelle Smith and staff - Texas Research Institute for Environmental Studies (TRIES). • Robert A. Welch foundation.

  26. THANK YOU THANK YOU

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