Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
UV-Vis Spectra and Fluorescence Properties of CdSe Nanocrystals
N. Atmaca 1 , M. R. Karim 1 , N. Yavarinia 1 ,H. Ünlü 1 *
1 Istanbul Technical University, Department of Physics, Maslak 34469, Istanbul, Turkey
Abstract-CdSe quantum dots have been synthesized from a solution including cadmium acetate, oleic acid, diphenyl ether and trioctylphosphine,
selenide heated under stirring and argon flow. Optical absorption and fluoresence spectra were used to characterize the optical properties of CdSe
quantum dots. We found t hat the absorption and emission peaks shifts to higher wavelengths as temperature increases.
Semiconductor quantum dots are tiny clusters of
semiconductor material, fabricated length scales between
nanometers and a few microns. Quantum dots (QDs) are
important because of their power to emit a particular wave
length.Also the size and shape of these structures can be
completely controlled. QDs can be used to make optical
devices such as photo detectors[1] and emitters[2] to be used
for quantum computing applications[3,4],
nanoelectronics[5,6], and biological applications[7].
Cadmium acetate and oleic acid were dissolved with
diphenyl ether in three neck flask. The mixture was heated
140 0 C under stirring and continuous argon flow.When
temperature rised to 140 °C, we waited for one hour. Then
the mixture was cooled to 70 °C. After then
trioctylphosphine- selenide solution having 200 °C
temperature under the vacuum was added to mixture and
heated to 110-140 °C. Samples were taken to tubes for 1, 5,
10, 15, 20, 25, 30 minutes. After samples cooling to room
temperature, centrifuged them to remove excess insoluable
organics and salts that may have formed during the reaction.
A precipitation using hexane as the solvents and methanol as
the nonsolvent is repeated three times to narrow the size
distribution and remove excess organics. The reaction
process was monitored by UV-Vis absorption and
fluorescence spectra as a function of time and temperature.
Fluorescence intensity (a.u.)
50
45
40
35
30
25
20
15
10
5
140 0 C
0
440 450 460 470 480 490 500 510 520 530 540 550
Wavelength (nm)
Figure 2. Fluorescence emission spectra of CdSe QDs at 20 min. At
different temperatures.
In conclusion, both the emission and absorption peaks
increase with increasing temperatures due to the increasing
particle size.
The authors would like to acknowledge the financial
support provided by TUBITAK under Grant No.TBAG-
105T463.
110 0 C
120 0 C
130 0 C
1.8
Absorbance (a.u.)
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
130 0 C
0
380 400 420 440 460 480 500 520 540
Wavelength (nm)
110 0 C
.
Figure 1. Absorption spectra of CdSe QDs at 1 min. at different
temperatures.
120 0 C
140 0 C
*Corresponding author: 0Thunlu@itu.edu.tr
[1] L. W. Ji and at all, Solid State Electronics 47, 1753-1756
(2003).
[2] S.Coe and at all,Nature,420, 800-803 (2002).
[3]X.Li and at all,Sience. 301, 809-811 (2003)
[4] E.Biolatti and at all, Phys. Rev. Letter,85, 5647-5650 (2000).
[5]I.Amlani and at all,Sience. 284, 289-291 (1999)
[6]M.Girlanda and at all, Applied Phys.Letter. 75, 3198-3200
(1999)
[7]P.Alivisatos,Nature Biotechnology. 22, 47-52(2004)
Figure 1 showed that the absorption peaks for 1 min. of
CdSe quantumdots samples at 110 °C, 120 °C, 130 °C,
140 °C) were 424, 446, 464 and 476 n m respectively. Figure
2 also showed that the emission peaks of fluoresence spectra
for 20 min. of CdSe QD samples at those temperatures were
488, 490, 506 and 516 n m respectively. These two results
had some differences, because peaks not only depend on
temperature but also on time. Those results had same
characteristics i.e. peaks increased with increasing
temperature.
6th Nanoscience and Nanotechnology Conference, zmir, 2010 338