Photoacoustic Monitoring of theMacroscopic Orientational Order in Disperse Red 1 Azo-Dye Based Dissolutions Vicente Torres, R. Castañeda- Guzmán, & O.G. Morales-Saavedra. CCADET-UNAM (Mexico) 1
2 Outline of the talk• Introduction – Molecular structure of the sample – UV-Vis spectra of dissolution and glass-cell• Experimental details – Experimental set-up http://digital.library.cornell.edu/• Results and discussions – Graph: averaged photoacoustic signals – Graph: Amplitude Fourier analysis – Graph: Correlation analysis – Graph: RMS-amplitude, and optical transmission vs. Voltage steps – Agreement with other investigations – Important parameters• Main conclusions and work to the future
3 Objetives:• Suggest a new photoacoustic methodology to characterize anisotropy in rod-like organic materials• Perform the PA study in switchable (poled and unpoled ) phases in memory-less samples
4Poled organic structures are inportant in: • Organic (dye) Solar Cells • (Organic Light Emitters Diode) OLEDs • Organic Non-linear Optics: Second Harmonic Generation (SHG)
5Chemical structure of the Disperse-Red-1 (DR1). • This standard NLO dye consists of (a) electron donor and (c) acceptor groups situated at two ends of a (b) azo-bridge (p-conjugated chain).1) No chemical degradation for laser action2) No structure bends in the DR13) No electrical/orientational memory effects DR1/Toluene = 0.175 mg/mL
6 Comparative UV–Vis absorbance spectraOnly the cromophore DR1 exhibits a strong and characteristic absorbance band within the visible range, near to lex = 532 nm laser excitation. 0.087 mg/mL H/E2k a
8 Experimental set-up (Detail) Glass cell with Pin DR1/Toluene dissolutionSin To the optical PZT-Sensor Sensor
9Averaged PLPA-signals for the DR1/toluene dissolution.
10Relative amplitude Fourier-analysis
11Correlation analyses vs. Voltage
12RMS-amplitude, and optical transmission vs. Applied voltage
13 Simple model (unpoled phase)• Acoustics: DR1 as line of transmission (wire-can model )• Optics: DR1 as a dipolar antenna
14Simple model (poled phase) CPLPA ~ 8.1%, Copt ~ 33.3%
15In the literature: Dicroic polarizer case CPLPA ~ 43%, Copt ~ 67% Laser Linear beam Polarizer PZT sensor Torres-Zúñiga, V., et. al., Optical absorption photoacoustic measurements for determination of molecular symmetries in a dichroic organic- film, Optics Express 16(25), pp. 20724-20733 (2008).
16 In the literature: Poled film case CPLPA ~ 3%Torres-Zúñiga, V., et.al., Monitoring molecular orientational order in NLO pushpull basedpolymeric films via photoacoustic measurements, Opt. and Lasers in Engineering 49(12),pp. 1413-1421 (2011).
17Anisotropy (A) and Macroscopic Orientational Order (f)APLPA ~ 5.6 %, Aopt ~ 21.4% fPLPA ~ 10%, fopt ~ 45%
18Main conclusions and work to the future1) The implemented experimental set-up is versatile and easy to assemble. Then, in future works is possible perform variations in the microphone position and use other polar molecules.2) The DR1 molecule is a good option to implement PA experiments @532 nm. However, in future works will be optimum obtain PA signals derived from the resonance optical peak interaction.3) Intense PA signals were obtained from the induced arrangement in the DR1 dissolutions. The PA signals are suitable to perform different numerical analysis based on the amplitude, the frequency or the phase.4) All the PA and optical analysis evidence (without contradictions) the change from an isotropic phase to an anisotropic one caused by the electric field. In particular: APLPA ~5.6%, and fPLPA ~10%.
19Thank you for your attention! • Any question? • Email: email@example.com