Institut des
NanoSciences de Paris

Nanostructures and optics

Study of single nanocrystals

Colloidal nanocrystals are crystalline spheres of a few nanometers, sometimes protected by a shell in order to improve their optical properties. They are very bright and stable emitters and their emission wavelength can be chosen over the whole visible range through the parameters of chemical synthesis (fig. 1a), and their optical properties compare to those of an « artifical atom ».

We collaborate with the group of Benoît Dubertret at the ESPCI (Paris) which studies the synthesis of high quality nanocrystals emitting in the red-near infrared and the optimization of the nanocrystals shell in order to suppress their blinking. We also work with the group of Pham Thu Nga at the IMS (Hanoi). We perform ensemble measurements (emission and absorption spectra, decay curves, quantum yield, low temperature measurements) (fig. 1b) as well as studies on single nanocrystals with a confocal microscope (blinking, single-photon emission, coherence and spectral diffusion (collaboration J.-P. Hermier, GEMaC)...) (fig. 1c).

Fig. 1 : Fluorescence of nanocrystals of CdTeSe synthesized at the ESPCI (left sample) et de CdSe/ZnS synthétisés à l’IMS (3 samples on the right, corresponding to 3 different nanocrystals sizes), illuminated by a UV lamp. (b) Emisison spectra of ensemble of nanocrystals from the IMS at various temperatures. (c) Intensity fluctuations (blinking) of a single nanocrystal from IMS with and without ZnS shell.


In the perspective of coupling a nano-emitter to a photonic structure, the knowledge of the emitter orientation is necessary. It is also necessary to determine whether light emission originates from a single dipole or from an incoherent sum of two degenerate dipoles (« 2D dipole »). We have established a theoretical description which connects the orientation of an emitter and its 1D or 2D nature to its polarization behavior. We have shown that the angle between the dipole and the optical axis can be extracted from the degree of linear polarization (provided that the theoretical relation between these quantities is known (fig. 2c), by a model which must include in particular the emitter optical environment and the objective numerical aperture). We applied this method to the study of CdSe/CdS nanocrystals (2D dipoles ; synthesis B. Dubertret) (fig. 2b) and to dot-in-rod CdSe/CdS nanorods (1D dipoles ; synthesis L. Carbone), as well as nanorods oriented by a liquid crystal (collaboration E. Lacaze).

Fig. 2 : An example of orientation measurement for a CdSe/CdS nanocrystal (a) Experimental setup schematic and definition of the angles, (b) result of the experimental polarization analysis, (c) theoretical relation between the degree of linear polarization \delta and the angle \Theta. The conclusion of this measurement is that \Phi = 49° and \Theta = 51°, with 4° uncertainty on each angle value.


Collaborations :

- Benoît Dubertret at LPEM (ESPCI, Paris)

- Pham Thu Nga at l’IMS (VAST, Hanoi)

- Alberto Bramati at LKB (Paris)

- Luigi Carbone, NNL, Istituto Nanoscienze-CNR, (Lecce)

- Emmanuelle Lacaze, INSP

- Jean-Pierre Hermier, GEMaC


Communications :

- Amit Raj Dhawan, Fu Feng, Laurent Coolen and Agnès Maître, Semiconductor luminescent colloidal core-shell nanorods and dot-in-rods, IEEE Photonics Journal 7, 1-6 (2015),

- Louis Biadala, Hugo Frederich, Laurent Coolen, Stéphanie Buil, Xavier Quélin, Clémentine Javaux, Michel Nasilowski, Benoît Dubertret and Jean-Pierre Hermier, Photon-correlation Fourier spectroscopy of the trion fluorescence in thick-shell CdSe/CdS nanocrystals, Phys. Rev. B 91, 085416 (2015),

- Laurent Pelliser, Mathieu Manceau, Clotilde Lethiec, Delphine Coursault, Stefano Vezzoli, Godefroy Leménager, Laurent Coolen, Massimo DeVittorio, Ferruccio Pisanello, Luigi Carbone, Agnès Maître, Alberto Bramati and Emmanuelle Lacaze, Alignment of rod-shaped single photon emitters dynamically driven by line defects in liquid crystals, Adv. Funct. Mat. 25, 1719 (2015)

- Clotilde Lethiec, Ferruccio Pisanello, Luigi Carbone, Alberto Bramati, Laurent Coolen and Agnès Maître, Polarimetry-based analysis of dipolar transitions of single colloidal CdSe/CdS dot-in-rods, New J. Phys. 16, 093014 (2014),

- C. Lethiec, J. Laverdant, C. Javaux, B. Dubertret, C. Schwob, L. Coolen and A. Maître, Determination of the orientation of a single nano-emitter by polarization analysis, Advanced Architectures in Photonics (AAP 2014), Prague (Rép. Tchèque), 21-24 septembre 2014,

- C. Lethiec, J. Laverdant, C. Javaux, B. Dubertret, C. Schwob, L. Coolen and A. Maître, Determination of the orientation of a single nano-emitter by polarization analysis, Condensed Matter in Paris (CMD25-JMC14), Paris, 24-29 août 2014,

- C. Lethiec, J. Laverdant, C. Javaux, B. Dubertret, C. Schwob, L. Coolen and A. Maître, Determination of the orientation of a single nano-emitter by polarization analysis, International Conference on Nanoscience + Technology (ICN+T), Vail (Etats-Unis), 21-25 juillet 2014,

- Hai Yen Nguyen, Willy Daney de Marcillac, Clotilde Lethiec, Ngoc Hong Phan, Catherine Schwob, Agnès Maître, Quang Liem Nguyen, Van Vu Le, Paul Bénalloul, Laurent Coolen and Pham Thu Nga, Synthesis and optical properties of core/shell ternary/ternary CdZnSe/ZnSeS quantum dots, Opt. Mater. 36, 1534 (2014),

- Clotilde Lethiec, Julien Laverdant, Henri Vallon, Clémentine Javaux, Benoît Dubertret, Jean-Marc Frigerio, Catherine Schwob, Laurent Coolen and Agnès Maître, Measurement of three-dimensional dipole orientation of a single fluorescent nanoemitter by emission polarization analysis, Phys. Rev. X 4, 021037 (2014),

- C. Lethiec, J. Laverdant, H. Vallon, L. Carbone, B. Dubertret, C. Javaux, C. Schwob, L. Coolen, A. Maître, Determination of the orientation of a single nano-emitter by polarization analysis, International Nanoscience Student Conference, (Londres, Août 2013)

- Clotilde Lethiec, Julien Laverdant, Hugo Frederich, Cherif Belacel, Catherine Schwob, Laurent Coolen, Agnès Maître, Godefroy Leménager, Alberto Bramati, Luigi Carbone, Etude en polarisation de l’orientation de différents types de nanoémetteurs, Journées de la Matière Condensée, Montpellier, août 2012

- J. Laverdant, W. Daney de Marcillac, C. Barthou, C. Schwob, L. Coolen, P. Benalloul, P. T. Nga et A. Maître, Experimental determination of fluorescence quantum yield of semiconductor nanocrystals, Materials 4, 1182 (2011).

- P. T. Nga, V. D. Chinh, V.T. H. Hanh, N. X. Nghia, P.T. Dzung, C. Barthou, P. Benalloul, J. Laverdant, et A. Maître, Optical properties of normal and “giant” multishell CdSe quantum dots for potential application in material science, Int. J. Nanotechnol., Vol. 8, 347 (2011), Special Issue on Nanotechnology in Vietnam.

- Nga, P.T., Chinh, V.D., Linh, P.T., Cuong, K.C., Hanh, V.T.H. and Nghia, N.X., Barthou, C. Maître, A., The temperature effect on photoluminescence properties of CdSe/ZnS quantum dots, Adv. in Nat. Sci., Vol. 10, 167-174 (2009).

- C. Barthou, C. Vion, L. Coolen, P. Benalloul, Pham Thu Nga, Vu Duc Chinh, Pham Thuy Linh, Vu Thi Bich, Pham Thu Nga, A. Maître, Luminescence Properties of II/VI Semiconductor Colloidal Nanocrystals at Collective and Single Scale, Asean Workshop On Advanced Materials Science And Nanotechnology (Nha Tran, Vietnam, 15-21 septembre 2008), IOP Publishing, Journal of Physics : Conference Series 187 (2009) 012018

- Nguyen Xuan Nghia, Pham Thu Nga, Vu Duc Chinh, Le Ba Hai, Phan Tien Dung, Do Thuy Chi, C. Barthou, P. Bénalloul, C. Vion et A. Maître, Synthesis and optical properties of core-shell semiconductor quantum dots in opal photonic crystals, Conference on Nanoscience and Technology (Pékin, Chine, juin 2007)

- Pham Thu Nga, Nguyen Van Chuc, Vu Duc Chinh, Nguyen Xuan Nghia, Phan Tien Dung, Dao Nguyen, Thuan, Pham Thai Cuong, Chu Viet Ha, Vu Hong Hanh, Vu Thi Kim Lien, Thai Nguyen, C. Barthou, P. Bénalloul, M. Romanelli et A. Maître, Synthesis and optical properties of colloidal core-shell semiconductor nanocrystals quantum dots for sensory application, 5th IEE Conference on Sensors (Daegu, Corée, octobre 2006)