Publication date: 27th June 2014
Near-infrared paramagnetic manganese-doped PbS nanocrystals
L. Turyanska1, F. Moro1, A. N. Knott1, O. Makarovsky1, A. Patanè1, M. W. Fay2, A. Meaney3, and P. C. M. Christianen3
1School of Physics and Astronomy, The University of Nottingham, NG7 2RD, UK; 2Nottingham Nanotechnology and Nanoscience Centre, NG7 2RD, UK; 3High Field Magnet Laboratory, Radboud University, Nijmegen 6525 ED, The Netherlands
The controlled incorporation of dopant impurities in a single colloidal nanocrystal (Quantum dot, QD) is a challenging field of research with potential for numerous applications in nanotechnology. Of particular interest is the incorporation of 3d transition metal ions (Mn, Co, etc) whose d-shell electronic configurations imprint the nanocrystal with unique magnetic and optical properties [1].
Here we report the successful incorporation of Mn in colloidal PbS nanocrystals and demonstrate Mn-induced electronic and optical properties of fundamental and technological interest. Our “one pot” synthesis approach produces nanoparticles that combine within one structure, paramagnetic properties of transition metals with efficient and tuneable photoluminescence (PL) emission in the near-infrared (NIR) wavelength range (850-1200 nm) [2].
We present electron spin resonance (EPR) studies revealing magnetic resonance transitions between states that are split by the hyperfine interaction between d-shell electrons and the nuclear spins of individual Mn2+ ions in the QDs . We investigate the spin dynamics of the Mn-impurities by pulsed EPR spectroscopy and achieve long spin coherence times (~ 1 ms at 5K) and Rabi oscillations.
Finally, we use high magnetic fields (up to 30T) to investigate the effect of an increasing Mn-content in the QD on the degree of circular polarization of the QD PL emission and show that Mn-impurities provide a tool for engineering the effective exciton g-factor. The observation of quantum oscillations and tuneable g-factor makes these new nanocrystals attractive candidates for spin manipulation studies and quantum information applications. Dual functionality, i.e. NIR luminescence and paramagnetism, of PbS:Mn also opens up exciting prospects for their future exploitation as imaging labels for combined fluorescence and magnetic resonance imaging. References
[1] Ochsenbein S. T. and Gamelin D. R., 2011 Nat. Nanotechnol. 6 112.
[2] Turyanska L., Moro F., Knott A. N., Fay M. W., Bradshaw T. D. and Patanè A., 2013 Part. Part. Syst. Charact. 30 945
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