Presented at Optical Society of America’s Conference on Lasers and Electro Optic, Baltimore, MD (May 2-6, 2011) Publication Reference: Devin Pugh-Thomas, Brian M. Walsh, Mool C. Gupta, “Quantum Dots for High Temperature Sensing”, Technical digest of the Conference on Lasers and Electro Optics, Baltimore, Maryland, May 2-6, 2011, paper JWA58.

1. Quantum Dots for High Temperature
Sensing
Devin Pugh-Thomas 1,2, Brian M. Walsh 2, Mool C. Gupta1
1 University of Virginia, Charles L. Brown Department of Electrical and Computer Engineering, Charlottesville, VA 22904
2 NASA Langley Research Center, Laser Remote Sensing Branch, Hampton, VA 23681
Abstract High temperature luminescence based sensing is demonstrated by embedding colloidal CdSe/ZnS
quantum dots into a high temperature SiO2 dielectric matrix. The nanocomposite was solution fabricated. The
CdSe/ZnS quantum dots in the nanocomposite show an absorption band at a wavelength of 600 nm. The room
temperature photoluminescence peak was observed at 606 nm. Temperature–dependent spectral and intensity modes
were investigated from 295-540 K. The sensor sensitivity is 0.11 nm/oC.
Introduction What are quantum dots? 0.35
Colloidal CdSe quantum dots have been CdSe (ZnS) 1mm film
Quantum dots are semiconductors whose excitons CdSe (ZnS) 5mm film
highlighted as one of the most distinguished 0.30 (a) CdSe (ZnS) solution
photonic materials in nanotechnology. One driver (electron-hole pairs) exhibit 3D quantum confinement.
for such research is the potential for application of They have properties between bulk semiconductors and
Absorption (A.U.)
(b)
quantum dots (QDs) into next-generation atoms which allows wavelength tunability with particle 0.25
electronic and photonic devices. Due to quantum size. Typical dimensions are 1-100 nm.
confinement, QDs have unique optical properties CdSe/ZnS core-shell quantum dot. 0.20
that resemble those of single molecules. The (c)
temperature dependence of photoluminescence
(PL) was recently demonstrated using quantum 0.15
dots, opening the field for thermometry
applications [1-2] . The insensitivity of the
emission to oxygen and other chemical species 0.10
presages these materials for luminescence 450 500 550 600 650 700
thermometry for aerospace applications. Wavelength (nm)
A step towards developing low cost opto-sensing UV-vis absorption spectra of CdSe/ZnS:SiO2 quantum
devices consists of immobilizing quantum dots in dot nanocomposite (a) 1 mm film, (b) 5 mm film and
solid support structures. When embedded into (c) solution recorded at T=295K.
select matrices, quantum dot-clusters exhibit
stabilized emission and high quantum yield. For
high temperature applications, the matrix must not 635
impede the luminescence and needs to be AFM thin film morphology.
chemically and thermally stable. In this work, a Ramp up
Cool down
CdSe(ZnS):SiO2 luminescence-based high 630
temperature optical sensor is demonstrated. Band gap structure of CdSe/ZnS:SiO2 thin film. Peak wavelength (nm)
625
620
615
610
250 300 350 400 450 500 550
Temperatrue (K)
Sensor stability under thermal cycling for
the peak wavelength shift.
Conclusions
To realize low cost opto-sensing devices, we
Results synthesized nanocomposite thin films of thermally and
photochemically stable semiconductor quantum dots.
The emission peak is Stokes shifted and the FWHM
50 140
increases with temperature. The temperature
Theoretical Expression for the
295 K dependent spectral shift of the QD PL emission under
Temperature dependent Linewidth:
300 K Experiment thermal cycle enables self-referenced intensity based
40 315 K 130 Theory
345 K
temperature measurements with 0.11 nm/oC
1
370 K   ELO   sensitivity. For the first time, we show a
395 K (T )  inh   AC T  LO exp 
 k T   1
 CdSe/ZnS:SiO2 luminescence-based high temperature
Intensity (A.U.)
FWHM (meV)
120  B  
30 425 K  sensor. This CdSe/ZnS:SiO2 sensor can be applied in
450 K
480 K combination with other luminescent indicators for
20
525 K 110 inh − inhomogeneous linewidth multi-sensing applications using the same
AC − exciton-acoustic phonon immobilization chemistry.
inh= 52.5 meV scattering coefficient
100
AC = 0.031 meV/K
10 LO −exciton-LO phonon coupling
LO= 50 meV
coefficient References
90 ELO= 25 meV
ELO − LO phonon energy 1.) G. W. Walker, V.C. Sundar, C. M. Rudzinski, D. M. Wun, G.
0 Bawendi, D. G. Nocera, Appl. Phys. Lett. 83, 3555-3557, 2003.
kB − Boltzmann constant
570 580 590 600 610 620 630 640 650 250 300 350 400 450 500 550 2.) G. De Bastida, F. J. Arregui, J. Goicoechea, I. R. Matias,
Wavelength (nm) Temperature (K) Sensors, 6, 1378-1379, 2006
Temperature response of the CdSe/ZnS:SiO2 Variation in the full width at half maximum Contact: Devin Pugh-Thomas
photoluminescence from room temperature to 525 K. (FWHM) with respect to temperature. Phone: (757) 864-3854, E-mail: dmp4t@virginia.edu