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(last update 02/03/2010)                                                                                                                                                                              

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(last 6 months)        

19/01/10: The paper "Interplay between Amplified Spontaneous Emission, Foerster Resonant Energy Transfer, and Self-Absorption in Hybrid Poly(9,9-dioctylfluorene)-CdSe/ZnS Nanocrystal Thin Films " by M. Anni et al has been published in the Journal of Physical Chemistry A

28/12/09: The paper "Oxygen Optical Gas Sensing by Reversible Fluorescence Quenching in Photo-Oxidized Poly(9,9-dioctylfluorene) Thin Films " by M. Anni and R. Rella has been published in the Journal of Physical Chemistry B

28/09/09: M. A. has been awarded by the Società Italiana di Fisica of the Panizza prize

Organic conjugated molecules emerged in the last 30 years as almost unique compounds, combining the typical qualities of plastics, like low cost, flexibility, and possible cheap production in large scale, with the properties typical of inorganic semiconductors, like charge transport, light emission and optical gain.

The "discovery and development of conductive polymers" was awarded in 2000 with the Nobel Prize for Chemistry.

Actually organic compound are used in prototypes of a wide family of devices, like LASERs, Field Effect Transistors (FET), Solar Cells,    and Light Emitting  Diodes (LEDs).

Our research is focused on the study of the emission properties of  light emitting organic molecules.    The research covers both basic physics studies and the  realization and characterization of device prototypes, with particular interest for organic LASER and sensors. 

The current research lines are:

Stimulated Emission and lasing in organic thin films

Linear optical properties of organic molecules

II-VI semiconductor nanocrystals and hybrid polymer-nanocrystal systems

All our papers are available in the Publication section. Please feel free to contact us for further details and possible collaborations.

Some examples of flexible devices, Left: a sheet of flexible polymeric Field Effect Transistors (from Bell Labs). Right: a flexible optically pumped organic laser, the yellow laser beam is well visible (from Ludwig Maximillian Universität Munich).		An example of color tunability of a single class of organic molecules (dioxide-oligothiophenes)

Stimulated Emission in organic thin films

Schematic level structure of a conjugated polymer showing the states involved in light absorption and emission. Light absorption (blue arrow) usually leads the molecule in a vibrationally excited state, then rapid relaxation to the lower energy excited state takes place, followed by light emission (yellow arrow) and final quick relaxation to the ground state. This 4 level scheme is ideal for low threshold LASER.		Typical emission spectra of the organic LASER realized in our laboratories. The laser emission shows a tunability across 40 nm, from the yellow to the orange region (see the photograph of the laser spot).
Right: Organic blue emitting waveguide with optical gain. The active film is about 300 nm thick and, in the measurement conditions, emits 3ns stimulated emission pulses with a 10 Hz repetition rate.(Click on the image for video)

Selected publications

-M. Anni, M. Alemanno "Temperature dependence of the Amplified Spontaneous Emission of the of Poly(9,9-dioctylfluorene) β-phase” Physical Review B 78, 233102 (2008)

-M. Anni, M. Alemanno “Spectral effects of gain saturation in the β-phase of Poly(9,9-dioctylfluorene)” Applied Physics Letters 93, 123311 (2008)

-M. Anni "The role of the β-phase content on the Stimulated Emission of Poly(9,9-dioctylfluorene) thin films" Applied Physics Letters 93, 023308 (2008) .

-M. Anni and S. Lattante "Non traditional laser systems: the case of organic random lasers" i Handbook of Organic Electronics and Photonics Vol. 2, Chapter 3 (American Scientific Publishers).

-S. Lattante, G. Barbarella,  L. Favaretto, G. Gigli, R. Cingolani, and M. Anni  "Efficient stimulated emission due to bimolecular annihilation reduction in oligothiophene dioxide thin films"  Applied Physics Letters 89, 051111 (2006).

- S. Lattante,  M. De Giorgi, R. Cingolani, G. Gigli, G. Barbarella, L. Favaretto, and  M. Anni “Interplay between Stimulated Emission and Singlet Singlet annihilation in oligothiophene dioxide thin films” Journal of Applied Physics 100, 023530 (2006).

-S. Lattante, F. Romano, A. P. Caricato, M. Martino, and M. Anni “Low electrode induced optical losses in organic active single layer PFO waveguides with two Indium Tin Oxide electrodes deposited by Pulsed Laser Deposition” Applied Physics Letters 89, 031108 (2006).

-S. Lattante, M. Anni, M. Salerno, L. Lagonigro, R. Cingolani, G. Gigli, M. Pasini, S. Destri, W. Porzio "Optical gain in fluorenyl-thiophene co-oligomer thin films" Optical Materials 28, 1072 (2006).

-M. Anni, S. Lattante, T. Stomeo, G.Gigli, R.Cingolani, G. Barbarella, L. Favaretto “Mode interaction and   light transport  in bidimensional organic random lasers in the weak scattering limit”  Phys. Rev. B 70, 195216 (2004).

-M. Anni, S. Lattante, G.Gigli, G. Barbarella, L. Favaretto and R.Cingolani “Far-field emission and feedback origin of random lasing in oligothiophene dioxide neat films” Appl. Phys. Lett. 83, 2754 (2003) .

-M. Anni, G. Gigli, M.Zavelani-Rossi, C.Gadermaier, G. Lanzani, G. Barbarella, L. Favaretto and R.Cingolani, "Amplified spontaneous emission from a soluble thiophene-based oligomer" Appl. Phys. Lett. 78, 2679 (2001).

Linear optical properties of organic molecules

	Chemical structure of a typical conjugated molecule (the PF8 monomer). The blue dots are Carbon atoms, while the cyan dots are Hydrogen atoms.
A nice example of how the emission properties can depend on the microscopic morphology. The top image shows the intensity of light emission a 82×82mm2 region of a polyfluorene (PF8) thin film as a function of the emitted light wavelength, while the bottom figure shows the emission spectra inside and outside the central cluster. The molecules inside the cluster adopt a planar chain conformation that lead to emission at higher wavelength (lower energy) with respect to the molecules in the large external uniform region.	Set-up for the characterization of organic optical gas sensors (c/o CNR-IMM Lecce). Two optical fibers are used for the laser excitation of the film and for the PL collection. The chemical composition of the chamber atmosphere is controlled by mixing dry air with the different analytes (In collaboration with  Dr. R. Rella of CNR-IMM Lecce)

Selected publications

-M. Anni and R. Rella "Oxygen optical gas sensing by reversible fluorescence quenching in photo-oxidized poly(9,9-dioctylfluorene) thin films " Journal of Physical Chemistry B  114, 2086–2090 (2010) with cover

-M. Anni, M. E. Caruso, S. Lattante "Microscopic Investigation of the Excitons' Intermolecular Energy Migration in the β phase of  Poly(9-9-Dioctyl Fluorene) by Confocal Laser Spectroscopy"  Journal of Physical Chemistry C 112, 2958 (2008).

-M. E. Caruso, and M. Anni “Real time investigation of the poly9-9-dioctyl fluorene β phase formation under solvent vapours exposure” Physical Review B 76, 054207 (2007).

-M. Anni, S. Lattante, M. De Kok, R. Cingolani, and G. Gigli "Intermolecular sequential energy transfer in a white emitting copolymer" Applied Physics Letters 89,221903 (2006).

-M. E. Caruso, S. Lattante, R. Cingolani and M. Anni “Microscopic investigation of the Poly(9,9-dioctylfluorene) photoluminescence dependence on the deposition conditions by confocal laser microscopy” Applied Physics Letters 88,181906 (2006).

-M. Anni, M. E. Caruso, S. Lattante, R. Cingolani “The role of excitons quasi equilibrium in the temperature dependence of the Poly(9,9-dioctylfluorene) β-phase photoluminescence”  Journal of Chemical Physics, 124, 134707 (2006).

-M.Anni, F. Della Sala, M. F. Raganato, E. Fabiano, S. Lattante, R. Cingolani, G. Gigli, G. Barbarella and L. Favaretto “Non radiative relaxation of dioxide oligothiophenes: the role of the environement”  J. Phys. Chem. B 109, 6004 (2005).

-M Anni, G. Gigli, R. Cingolani, Y. Galvão Gobato, A. Vercik, A.Marletta, F.G. Guimarães, R. Faria “Defect-assisted photoluminescence intensity enhancement in poly(p-phenylene vinylene) films probed by time-resolved photoluminescence” Phys. Rev. B 68 035215 (2003).

  II-VI Semiconductors nanocrystals and hybrid nanocrystal-polymer systems

	Left: dependence of the emission color on the nanocrystal size. The nanocrystals in the solutions in the picture have the same chemical composition and the tunability of the emission wavelength is fully due to quantum size effects.
Right: schematic description of the resonant energy transfer between a polymer and a semiconductor nanocrystal. An UV laser (blue photon on the left) is used to generate an exciton in the polymer. The excitation is then non-radiatively transferred (green arrow) to the nanocrystal, where finally radiative recombination takes place, with the emission of a red photon.

Selected Publications

-M. Anni, E. Alemanno, A. Cretì, C. Ingrosso, A. Panniello, M. Striccoli, M. L. Curri, and M. Lomascolo "Interplay between Amplified Spontaneous Emission, Forster Resonant Energy Transfer and self absorption in hybrid Poly(9,9-dioctylfluorene)-CdSe/ZnS nanocrystal thin films" Journal of Physical Chemistry A  114, 2086–2090 (2010)

-A. Cretì. M. Lomascolo, G. Leo, L. Manna, and M. Anni “Shell-thickness effects in photoluminescence decay of colloidal core/shell nanorods”  Journal of Luminescence 128, 361 (2008).

-A. Cretì, M. Anni, M. Zavelani-Rossi, G. Lanzani, L. Manna and M. Lomascolo "Ultrafast carrier dynamics and confined acoustic phonons in CdSe nanorods" Journal of Optics A: Pure Appl. Opt. 10, 064004 (2008).

-A. Cretì, M. Anni , M. Zavelani-Rossi , G. Lanzani , L. Manna , and M. Lomascolo "Role of defect states on Auger processes in resonantly pumped CdSe nanorods" Applied Physics Letters 91, 093106 (2007).

-A. Cretì, M. Zavelani-Rossi, G. Lanzani, M. Anni, L. Manna,  and M. Lomascolo “Role of the shell thickness in Stimulated Emission and Photoinduced Absorption in CdSe core/shell nanorods”  Physical Review B 73, 165410 (2006).

-A. Cretì, M. Anni, M. Zavelani Rossi, G. Lanzani, G. Leo, F. Della Sala, L. Manna, and M. Lomascolo "Ultrafast carrier dynamics in core and core/shell CdSe quantum rods: Role of the surface and interface defects" Phys. Rev B 72, 125346 (2005).

-D. Valerini, A. Cretì, M. Lomascolo, L. Manna, R. Cingolani, and M. Anni "Temperature dependence of the photoluminescence properties of colloidal CdSe/ZnS core/shell quantum dots embedded in a polystyrene matrix" Phys. Rev. B 71, 235409 (2005).

-M. Anni, D. Valerini, L. Manna, A. Cretì, R. Cingolani and M. Lomascolo "Förster energy transfer from blue emitting polymers to colloidal CdSe/ZnS core shell quantum dots"  Appl. Phys. Lett. 85, 4169 (2004).