speed of light
Transcript
speed of light
CAPITOLO IV° Materiali per ottica non lineare. Origine della Risposta ottica nonlineare in materiali organici molecolari. Materiali per elettroottica. Sistemi Push-Pull e modello della Bond Length Alternation. Polimeri polati, vetri solgel. Multistrati auto assemblati 1 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Case study 1 ORGANIC ELECTRO-OPTIC MODULATORS or The surface as a template for the ordered, non centrosymmetric growth of multilayered thin films starting from strongly dipolar precursors 2 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS 3 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Critical to Next Generation Computing •High frequency, ultra high stability clocks •On-chip signal distribution •Chip-to-chip interconnection •Module-to-module interconnection - Potential for Lower Cost - Exceptional Large Bandwidth, Low Relative Permittivity - Mechanical Properties - Integration with Semiconductor Electronic (Very Large Scale Integration -VLSI) - Potential for Lower Operating Voltages 4 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Electro-Optic Materials: the need for manipulation of optical signals LiNO3: 10GHz, 35dB Vπ = 5-6 V Mach-ZehnderModulator 5 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Electro-Optics: The Phenomenon • An electro-optic material (device) permits electrical and optical signals to “talk” to each other through an “easily perturbed” electron distribution in the material. A low frequency (DC to 200 GHz) electric field (e.g., a television [analog] or computer [digital] signal) is used to perturb the electron distribution (e.g., π-electrons of an organic chromophore) and that perturbation alters the speed of light passing through the material as the electric field component of light interacts with the perturbed charge distribution. • Because the speed of light is altered by the application of a control voltage, electro-optic materials can be described as materials with a voltage-controlled index of refraction. Index of refraction = speed of light in vacuum/speed of light in material 6 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Nonlinear Optical Transmission 400 nm 400 nm 800 nm 800 nm 1064 nm 532 nm 1064 nm 355 nm R2N NO2 λmax = 430 nm (CHCl3) NO absorption 7 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS 8 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS 9 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS N ZWITTERIONI N C C O N C S O N N N S C N N BETAINE MEROCIANINA O NH3 N CH3 CH2 COO 10 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS 11 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS When and How Nonlinear Optics (NLO)? Nonlinear optical phenomena arise when applied external fields, ie, either light or low frequency electrical fields, are sufficiently strong to compete with internal electrostatic interactions. Thus, nonlinear optical materials are typically those containing weakly bound (highly polarizable) electrons (read: π-electrons). electronic excited state (LUMO) ω ω 2ω 400 nm 1064 nm ω ω ω ω 3ω ω ω 800 nm electronic ground state (HOMO) Linear Absorption (Lambert-Beer) Second-Harmonic Generation (SHG) (II order NLO) Third-Harmonic Generation (THG) (III order NLO) Two-Photon Absorption (2-PA) (III order NLO) 12 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Molecular design guidelines: the Two State Model Approximations: 1. Almost one dimensional (linear) molecules 2. Main charge-transfer transition aligned with conjugation axis 3. Only the ground and excited states are taken into account β∝ µ ∆µ 2 eg E 2 eg LUMO (e state) Eeg HOMO (g state) µeg = transition moment between ground and excited states (proportional to the extinction coefficient ε) ∆µ = dipole moment difference between ground and excited states Eeg = HOMO-LUMO transition (from the absorption spectrum) 13 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Jablonski Energy Diagrams Sn photochemistry and photophysics thermal relaxation S1 ISC ns-µs T1 2-PA fluor phos fs ps-ns µs-ms S0 14 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS The Mach Zehnder Interferometer Vπ = λd/(2n3r33LΓ Γ) Vπ is the voltage required to achieve signal transduction (on/off modulation) λ = optical wavelength n = index of refraction r33 = electro-optic coefficient L = interaction length Γ = modal overlap integral d = electrode gap From M G Kuzyk, C W Dirk, Marcel Dekker Inc., 1998 15 Dept. Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Dept. Materials Science, Why Organic Electro-Optic Materials? Intrinsic material bandwidths of several hundred gigahertz. The response time (phase relaxation time) of π-electrons in organic materials to electric field perturbation is on the order of femtoseconds. Operational bandwidths of 150 GHz have been demonstrated for modulators & switches • Organic electro-optic coefficients are currently 2-4 times higher than lithium niobate and getting larger • Organic EO materials are highly processable into 3-D circuits and can be easily integrated with semiconductor electronics and silica fiber optics 16 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Comparison of Lithium Niobate and Polymer Electro-Optic Modulators State-of-the-art High Speed Infrared Modulators Commercial Lithium Niobate Devices—The Competition Vπ: 6 V @1550 nm, 30 GHz Bandwidth, $6000/per unit Commercially Available Polymer Devices Vπ: 1.2 V @ 1300 nm, 1.8 V @1550 nm 20 GHz and 30 GHz Bandwidth (3dBe) Published Prototype Device Results Vπ: 0.77 V @ 1300 nm 100 GHz operation 10 Modulator Chips on 3 Inch Wafer Pacific Wave Industries, California 90245 2 Push-Pull MZ Modulators on One Chip 17 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS NONLINEAR OPTICAL EFFECTS: Microscopic and Macroscopic Polarization—Power Series Expansion The molecular polarization P for a given molecule in the presence of a field E can be wtritten as: pi = α ij E j + β ijk Ek E j + γ ijkl E j Ek El + ... β is the first nonlinear term, known as molecular first hyperpolarizability. For a symmetric molecule even order terms, β and higher, are zero. For a bulk material or a film: Pi = χ ij E j + χ (2)ijk E k E j + χ (3)ijkl E j E k E l + ... χ(2)represents the material first nonlinear susceptibility. The chromophores must be aligned acentrically within the material to realize a nonzero χ(2). The electro-optic effect is a second order nonlinear optical phenomenon. GEOMETRIC PREREQUISITE (β β, χ ≠ 0) => NO CENTROSYMMETRIC STRUCTURE 18 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS The electro-optic coefficient r33 The coefficient of the second term in the power series expansion of material Polarization in terms of the applied electric fields, χ(2), is given by: χ ( 2 ) zzz = Nβ zzz < cos3 θ > (const ) r33 = −2 χ (2)zzz /(n z ) 4 r33 = βN<cos3θ>(constant) Loading Parameter = N <cos3θ> = (r33/β) (constant) r33 = electro-optic coefficient N = chromophore number density (molecules/cc) b = molecular first hyperpolarizability N<cos3q> = acentric order parameter n = refraction index *The constant depends on the dielectric properties of the material lattice 19 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Chromophore Requirements •Large hyperpolarizability and large dipole moment optimization of β •No absorption at operating wavelength •Stability --Thermal --Chemical & Electrochemical --Photochemical •Solubility •Compatibility with materials processing (polymeric, glassy…) Electro-optic activity requires noncentrosymmetric chromophore symmetry, i.e., <cos3q> must be large •Requires optimization of N<cos3q> 20 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Traditional Chromophore Design: Push-Pull derivatives NC Electron Donor N S NC CN S O Electron Acceptor π-conjugated bridge β∝ µ eg2 ∆µ E 2 eg Strong charge transfer transition from an electron donor group to an electron acceptor group Strongly dipolar structures (dipole moment inversion on going from the ground to the excited state) Highly polarizable π conjugated bridge 21 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Traditional Chromophore Design: Push-Pull derivatives µβ enhancement tools: 1. Use of stronger Donor and Acceptor Groups 2. Introduction of more polarizable π-bridge (tuning of the bridge aromaticity, heterocycles) 3.Conjugation length increase still preserving solubility, stability, processability and possibly easy synthetic access Zhang and Jen Proc. SPIE 372 (1997) Ermer et al. Chem Mater. , 1498 (1997). 22 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Traditional Chromophore Design: Push-Pull derivatives - Acceptors ∗ NO2 ∗ NO2 CN ∗ CN ∗ ∗ N ∗ S Ph O N ∗ O O Me N Me O F F NC NC CN CN Dalton acceptor ∗ O F CN CN CN F ∗ CN H O F NC NC S ∗ O NC CN Sandoz acceptor ∗ R N N ∗ ∗ NO2 X X = S, NR, O (CO)5M ∗ M N ∗ N N M N 23 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Traditional Chromophore Design: Push-Pull derivatives – π-bridges ∗ ∗ ∗ ∗ ∗ n n ∗ ∗ ∗ ∗ ∗ n ∗ N ∗ N ∗ N ∗ ∗ ∗ S ∗ ∗ S S ∗ X ∗ Y X = O, S; Y = N 24 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Traditional Chromophore Design: Push-Pull derivatives - Donors OR' R R N N R'O ∗ R'O ∗ R = Me, Et, Bu, Ph S ∗ ∗ ∗ R' = H, Ac, TBDMS NC NC R 2N N N N Me ∗ NC S ∗ ∗ NC ∗ O 25 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Target for electro-optics applications Figure of Merit: electro-optic coefficient r33 (Mach-Zender Modulator: info-coding in fiber-optic transmission) Present technology LiNbO3 r33 = 31 pm V-1 Best performing poled organic NLO polymer to date (Bu)2N NC CN polycarbonate matrix O S O r33 = 55 pm V-1 20% wt% loading 26 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Design motifs for obtaining EO-materials with no centrosymmetric superstructure from NLO-fores POLING PROCESS (to iso-orient the Chromophores) IS NECESSARY NO POLING 27 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Incorporation Of NLO-phoric Molecules Into Solids There exist four major methods by which chromophores are incorporated into polymers. In the main-chain approach, chromophores are chemically attached to the polymer backbone itself. In the side-chain approach, chromophores are chemically attached as part of the side chain to the polymer backbone. These systems have the advantage that a high concentration for the chromophores can be obtained without crystallization, phase separation, or the formation of concentration gradients. In the cross-linking approach, chromophores act as crosslinking bridges between two polymer chains. This method effectively destroys the mobilization of segments of the polymer chains. And since polar or octopolar alignment of the dipole moments is required, most of the cross-linking must occur during or after the poling process is completed. In the guest-host system approach, chromophores form a solid solution in a polymer host. This approach has the simplicity that the chromophores do not need to be chemically bound to the From M G Kuzyk, C W Dirk, Marcel Dekker Inc., 1998 polymer. 28 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS For each of the four approaches mentioned, a poled polymer system in the absence of an applied static electric field is not in thermodynamic equilibrium. The order parameter (cos(Φ Φ)), where Φ is the angle between the dipole moment of a molecule and the poling field, therefore decays over time, resulting in the decay of the macroscopic second order susceptibility. One can greatly reduce this intrinsic thermal relaxation by using polymer systems with intrinsically high glass transition temperatures. One elegant example currently under development is the class of optical polyimides with glass transition temperatures greater than 300-400°C. From M G Kuzyk, C W Dirk, Marcel Dekker Inc., 1998 29 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS INCORPORATION OF 2nd and 3rd order NLOPHORES INTO MATRICES Matrix •HOST-GUEST advantage drawbacks high solubility short-lived stability high poling temperature SIDE CHAINS long-lived stability may be less compatible OF BACKBONE 2nd order are highly polar, even zwitterionic systems and thus salt-like! Many 3rd order are salts ! high poling temperature How to make salts compatible with polymers ? 30 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS HIGH Tg POLYMERIC MATERIALS FOR NLO ADVANTAGES DRAWBACKS - good mechanical properties - hard reaction conditions - high thermal and chemical stability - low processability - temporal stability of performances - toxicity of employed - good optical quality solvents Requirement high concentration of efficiently active chromophores BUT… The highest the activity, the lowest stability and solubility!!! 31 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS CROSSLINKED POLY(AMIDO)AMINES O a O N N O CH3 b HN NH + d R-NH2 Water 4 d, r.t. O N N O H2N NH2 N N O N N R N c O Cross linking agent N N O N O N O Functionalized chromophore - extraordinary mild reaction conditions - easy tunability of mechanical properties - easy processability - good optical properties - concentration of the active molecule from 0.05 to 40 % by weight independently on the solubility (heterogeneous phase reaction) PROTECTION FROM PHOTODEGRADATION 32 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS FUNCTIONALIZED MOLECULAR PRECURSORS H2N CH3 N H N H2N N CH3 N N O Br H2N O Br N CN S CN H2N H N O O N CN S CN - Presence of a primary amino group is the only requirement - The nature of substituents on the pyridic nitrogen does not influence the electronic structure 33 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS PHOTOSTABILITY – THE MATRIX EFFECT H3C N CN S 0% 50% CN MeOH (after 48 h) acetone (after 4 h) Poor solution photostability because of reaction with singlet oxygen: suicidal chromophore Tertiary amino groups are efficient scavengers for 1O2 Solid state photobleaching 0h 2h 10 h 40 h 80 h 120 h 180 h 240 h 300 h 400 h 800 h 1000 h 1200 h O CH3 O N N N N n Dramatically enhanced photostability in the solid! 34 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS COME SI MISURA L’IPERPOLARIZZABILITA’ QUADRATICA MOLECOLARE β? TECNICA EFISH (Electric Field Induced Second Harmonic Generation) TECNICA SOLVATOCROMICA TECNICA HRS (Hyper Raleigh Scattering) Per i materiali bulk in polvere, l’efficienza di seconda armonica viene determinato mediante la TECNICA SPERIMENTALE DI KURTZ-PERRY Per i film può essere misurata con il metodo delle frange di Maker (coefficienti d ∝ χ (2)) 35 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS TECNICA EFISH Le molecole NLO attive in una soluzione vengono orientate mediante l’applicazione di un forte campo elettrostatico L’iperpolarizzabilità quadratica viene ottenuta dalle frange di interferenza di Maker. Fornisce la proiezione della componente vettoriale di β lungo la direzione del momento di dipolo µ. ω 3+ laser Nd :YAG 1064 o 1907 nm β≠ 0 soluzione SHG 2ω frange di Maker I 2ω , l c → γ EFISH → βλ Campo elettrico applicato (5 -8 kV ) Contributo dipolare Contributo elettronico γ EFISH = µβλ 5 KT + γ 0 ( − 2ω ;ω, ω , 0 ) Intens ità della 2a armon ica Traslazione della cella (mm) 36 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS IlIl metodo metodo solvatocromico solvatocromico Fornisce il valore di β lungo la direzione di trasferimento di carica. Spostamento della banda di assorb. o emissione in solventi di diversa polarità Assorbimento Equazione di McRae: ( ( ) ε −1 n2 −1 2 n2 −1 ν a =ν + A 3 2 + B − 2 ε + 2 a 2n + 1 n + 2 g a B= ) Emissione − 2 µ g (µ e − µ g ) ν a reg2 ∆µeg 3 = 2 2 2 2 2 2h c ν a −ν1 ν a − 4ν12 2 βCT ( )( ) νa = frequenza della banda di assorbimento MLCT ; ν1= frequenza della radiazione incidente (1.907 nm); reg =momento di dipolo della transizione (reg2=2.13 x 10-30 f/na , (µ µe- µg) = ∆ µ eg = variazione del momento di dipolo tra stato eccitato e fondamentale Equazione di Liptay hca 3 ↓ ∆µeg noti µg e a 3M a = 4πdN AV ε −1 n2 −1 − 2 ε + 2 n + 2 ν a −ν e = C + D 1/ 3 M Vm = 4 / 3πa = dN AV 3 2(µ e − µ g ) 2 D= hca3 S.Bruni, E.Cariati et al. Spectrochimica Acta Part A , 2001, 57, 1417 37 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS MISURA ° ORDINE MISURA DELLE DELLE PROPRIETA PROPRIETA’’ NLO NLO DI DI II II° ORDINE EFISH βλ Proiezione lungo l’asse del momento di dipolo Misura di β SOLVATOCROMISMO Confronto possibile solo se la direzione del trasferimento di carica coincide con la direzione del momento di dipolo βCT Componente lungo l’asse del trasferimento di carica 38 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Hyper Rayleigh Scattering (HRS) Per molecole dipolari,ottupolari (µg=0), neutre o ioniche. Fornisce una media sulle varie orientazioni di tutte le componenti del tensore β ω Nd3+ : YAG laser 1064 or 1907 nm β≠ 0 soluzione SHG 2ω Scattered signal at 90° I2ω < β2> β = β J =1 + βJ =3 βJ = 1 : componente dipolare o vettoriale del tensore β βJ = 3 : componente ottupolare del tensore β 39 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS HRS NPP=N-4-nitrofenilprolinolo polvere PM = fotomoltiplicatore, C= cuvetta portacampione, L= lenti convergenti, FV = filtri, P = polarizzatore 40 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS IL METODO KURTZ-PERRY ω laser Nd3+:YAG 1064 o 1907 nm Nd 3+ : YAG LASER 1.06 µm χ(2) ≠ 0 campione (polvere) SHG 2ω dove I2ωω ∝ χ(2) Raman Cell Filled with H2 1.91 µm Le misure SHG sono fatte rispetto a uno standard (quarzo, urea). 41 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Systematic Improvement of µβ Increase in the accepting strength Increase in the conjugation length µβ (x10 -48 esu) R N 80 N O2 R µβ (x10 -48 esu) R N NA NC S R 9,800 CN CN R N 580 N R N N O2 TC V R N DR , 30 w t% , r 33 = 13 pm /V R O N S O CN T C VI P 2,000 Ph R CN R 15,000 NC ISX N S R S CN R SO2 R NC N CN N S 13,000 NC R 3,300 C F2 (C F2 ) 5 C F3 SDS R FC N NC CN N R NC S 18,000 O R N 4,000 R O Ph AP TE I N F T C , 20 w t% , r 33 = 55 pm /V R N O R CN R' R N S R TC I CN NC 6,100 CLD 30,000 O NC NC CN NC 42 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS The bond length alternation model For a given π-bridge there is an optimal combination of Donor and Acceptor groups. If the ground state charge distribution is too asymmetric the β value decreases. Marder, S. R.; Kippelen, B.; Jen, A. K.-Y.; Peyghammbarian, N. Nature (London) 1997, 388(6645), 845-851. A D Neutral structure β>0 A D + Cyanine limit β=0 β Zwitterionic structure β<0 0 - 0.04 BLA BLA = average length difference between double and single bonds in the gr- state At the cyanine limit the molecule is symmetric and the β is accordingly zero. 43 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Further Molecular Descriptors MIX = - cos θ = - [ ( V V + 4t 2 2 ag ) 2 −1/ 2 c =1/ 21− ∆µ 4µ + ∆µ 2 2 ] BLA (in Å) = 0.11 MIX C2 is a measure of the intramolecular charge transfer !! 44 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS The bond length alternation model Me2N O Me2N Me2N Me2N O O Me2N O NMe2 Me2N NMe2 Me N O Me N O ( β > 0) ( β = 0) ( β < 0) 45 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS A figure of merit: hyperpolarizability per unit of MW MW βµ(0) βµ / M 567 14920 26.3 265 6990 26.4 347 11000 31.7 O N N O N S Marder, Science, 1994 Me N CN S Me CN N S S CN CN Gazz. Chim. Ital. 1997, 127, 165; J. Org. Chem. 1997, 62, 5755; Mat. Res. Soc. Symp. Proc. 1998, 488, 819 46 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Probing the contribution of the two limit forms: single/double-bond character of the central unit Experimental Evidence: Coupling Constants (J/Hz) R aromatic H N CN S R H N CN S CN quinoid CN H H quinoid Solvent Pyridine Quinoline Acridine Dioxane 13.61 12.99 12.69 Chloroform 14.02 13.42 12.78 DMF 15.10 14.33 13.76 aromatic Abbotto, A.; Beverina, L.; Bradamante, S.; Facchetti, A.; Klein, C.; Pagani, G. A.; Redi-Abshiro, M.; Wortmann, R. Chem. Eur. J. 2003, 9(9), 1991-2007. 47 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS TUNING FIRST HYPERPOLARIZABILITY THROUGH RING FUSION AND SOLVENT POLARITY 48 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS TUNING FIRST HYPERPOLARIZABILITY THROUGH RING FUSION AND SOLVENT POLARITY R N CN S R N CN S CN CN Experimental (computed) β0µ values (10-48 esu) Solvent Pyridine Quinoline Acridine Gas phase (+310) (+370) (+420) Dioxane a -510 (-800) + 610 (+750) + 1880 (+1760) Chloroform b - 6990 (-9600) (-10900) (-13500) DMF b - 2000 (-4200) (-3900) (-3600) a Electrooptical Absorption Measurements (R. Wortmann) b EFISH data (P. Prasad, J. Zyss) Abbotto, A.; Beverina, L.; Bradamante, S.; Facchetti, A.; Klein, C.; Pagani, G. A.; Redi-Abshiro, M.; Wortmann, R. Chem. Eur. J. 2003, 9(9), 1991-2007. 49 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Computed Solvent-dependent Charge Distribution Me Me acceptor acceptor N N CN CN S S CN CN donor donor 1.000 1.000 0.800 0.800 acceptor Natural Charge 0.600 0.600 0.400 0.400 0.200 0.200 C=C 0.000 0.000 -0.200 -0.200 -0.400 -0.400 Py 1c Qu 2c Ac 3c -0.600 -0.600 -0.800 -0.800 donor Neutral-quinoid S DM O SO D M F F DM D M e ac et on e ac e to n m CH Cl 3 of or or ty l et di he bu r ty le t ch her l bu di ane ox an e du di ox ga s ga s ph as ph as e e -1.000 -1.000 Zwitterionic - aromatic 50 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Electrooptical Absorption Measurements in Dioxane and Derived NLO properties Pyridyl Compound Quinolyl Acridyl µg (10−30 C m) 51.2 46.3 30.1 µe (10−30 C m) 41.4 52.0 73.1 ∆µ (10−30 C m) - 9.8 5.7 43.0 β0 (10-50CV-2 m3) - 79 56 310 0.56 0.46 0.22 c2 C2 is a measure of the intramolecular charge transfer !! 51 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Solvato- and Solidochromic Data for the N-decyl Pyridyl Chromophore in Selected Film Matrixes. Entry Matrix ε λmax (nm) 1 Siliceous (SiO2 sol-gel) >6 592 2 Poly(p-hydroxy styrene) ? 616 3 Poly(ethylene glycol) 3.6-4.0 628 4 N-Decyl Pyridyl (neat) ? 648 5 PMMA 3.2-3.5 676 6 Polymaleimide 3.1-3.3 680 7 Poly(vinylbenzyl chloride) 2.7-2.9 702 8 Polystyrene 2.5-2.6 724 52 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Issues with Traditional 1D Chromophores D π-bridge A Increasing in conjugation length is usually accompanied by: optical absorption red shift (eroding transparency) reduced thermal stability Challenge is clear: How can we optimize EO response, thermally stability and transparency? 53 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Design of Twisted Chromophores R R R R THEORY N O θ N O θ R R Twisted "Zwitterionic" Structure R R Flat "Quiniod" Structure I. Characteristics: -Sterically-enforced reduction in D-π π-A conjugation - Charge-separated zwitterionic ground state - Large Δµge - Tune β and λ with θ II. Attractions: - chromophores “Simple” molecules - µβ β figures ~ up to 10 × greater than other reported III. Challenge - Synthesis θ ≈ 70 - 85°° Albert, I. D. L.; et al. JACS, 1997, 119, 3155.; Albert, I. D. L.; et al. JACS, 1998, 120, 11174.: Keinan, S.; et. al. THEOCHEM, 2003, 633(2-3), 227 54 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS The twisted Chromophores t-Bu O n t-Bu R N TM TM-1, n = 0, R = Me TM-2, n = 1, R = n-Octyl CN R N n CN TMC TMC-1, n = 0, R = Me TMC-2, n = 0, R = TMC-3, n = 1, R = Kang, Facchetti, Peiwang, Ho, Marks, Righetto, Cariati, Ugo Angew. Chem. Int. Ed. 2005, 44(48), 7922-7925. 55 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Synthesis O N O Br B(OH)2 NaH2PO2 O N O N N N OTf I NaCH(CN) 2 Pd(PPh 3)4 NH=CPh 2 Pd(OAc)2/BINAP Cs2CO3 N N O OH Pd/C Pd2(dba)3/ligand K3PO4 Tf2O Pyridine/HCl Ph N CN N i. ROTf CN ii. MeONa Ph NaOAc NH2OHHCl N NH2 i. NO+BF4ii. NaI 1, R = Me 2, R = CN CN N Pd(OAc)2/PPh3, NEt3 CN i. ROTf CN ii. MeONa 3, R = Kang, Hu; Facchetti, Antonio; Stern, Charlotte L.; Rheingold, Arnold L.; Kassel, W. Scott; Marks, Tobin J. Org. Lett. 2005, 7(17), 3721-3724. 56 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS X-Ray Diffraction Characterization CN N CN 1 θ = interplanar twist angle Highly twisted θ = 80-85°°− Pronounced reduction in inter-ring π-conjugation - Predominant negative charge localization in C(CN)2 group. Significant aromatic character in pyridinium ring - A stable, highly charge-separated zwitterionic geometry dominates the ground state 57 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS NLO Response Properties. µβ Chromophore Figure of Merit: µβ/Mw EFISH µβ (10-48 esu) CN 1000 N CN 900.8 N CN CN t-Bu O t-Bu - 315,000 (± ±12%) CN N CN µβ/Mw at 1907 nm (10-48esu) N - 24,000 (± ±18%) N CN CN 800 t-BuMe2SiO N t-BuMe2SiO O CN CN CN AcO 600 NC N S CN CN O AcO Bu Bu N NC S CN CN 400 Bu N NC Bu CN S CN N CN CN 200 NC Me2N 0 S N N 2.1 NO2 17.3 25.5 27.1 25.9 45.7 57.8 - 466,000 (± ±8%) 58 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS The electro-optic coefficient r33 The coefficient of the second term in the power series expansion of material Polarization in terms of the applied electric fields, χ(2), the susceptability is given by: χ ( 2 ) zzz = Nβ zzz < cos3 θ > (const ) r33 = −2 χ (2)zzz /(n z ) 4 r33 = βN<cos3θ>(constant) Pi = α ij E j + β ijk Ek E j + γ ijkl E j Ek El + ... Loading Parameter = N <cos3θ> = (r33/β β) (constant) r33 = electro-optic coefficient - N = chromophore number density (molecules/cc) β= molecular first hyperpolarizability - N<cos3q> = acentric order parameter n = refraction index *The constant depends on the dielectric properties of the material lattice GEOMETRIC PREREQUISITE (β β, χ ≠ 0) => NO CENTROSYMMETRIC STRUCTURE 59 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Optimization of Electro-Optic Activity Molecular Level Requires optimization of β Molecular design is the key Macroscopic Level •Electro-optic activity requires noncentrosymmetric chromophore symmetry, i.e., <cos3θ> must be large •Requires optimization of N<cos3θ> 60 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Design Motifs For Acentric Electrooptic Organic Materials Poled HostHost-Guest POLING PROCESS (to iso-orient the Chromophores) Poled and Functionalized Poled ,Functionalized , inked Crosslinked Poled ,Crosslinkable Matrix IS NECESSARY Chromophoric LB LBFilm Film SelfAssembled Superlattice Superlatt (SAS) Self -Assembled NO POLING = Chromophore Module 61 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Poled polymers GEOMETRIC PREREQUISITE (β β, χ ≠ 0) => NO CENTROSYMMETRIC STRUCTURE Strongly Dipolar Chromophore Random Host Guest polymer T < polymer Tg DC field off χ2 = 0 pm/V T > polymer Tg DC field (strong) on χ2 ≠ 0 pm/V Rapid cooling T << polymer Tg DC field off χ2 ≠ 0 pm/V Poor temporal stability 62 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Corona poling experimental setup The Charge Deposition on the polymer surface allows for the minimum possible separation between the electrodes (higher DC fields) Oxygen contamination must be avoided (ozone formation) 63 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Electro-optic polymeric materials poling process A DC poling field is applied across the chromophore / host matrix. r33 = βN<cos3θ>(constant) E F i e l d Top electrode CN CN O NC CF 3 NC O NC CF 3 NC CN CF 3 NC O O O NC CF 3 CF 3 NC CN NC O NC CN NC CF 3 NC CN CF 3 NC O NC CN NC O NC CN CF 3 NC N OTBDMS N N OTBDMS TBDMSO OTBDMS TBDMSO N TBDMSO OTBDMS N N TBDMSO OTBDMS OTBDMS TBDMSO TBDMSO N N OTBDMS OTBDMS TBDMSO TBDMSO Bottom electrode Ideal case (no intermolecular interactions) : < cos3 θ> = µE / 5kT 64 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS SiO2 65 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS = ? I ciclooligosilossanolati di formula generale [RSi(O)O]nn- (R = Ph; n = 3, 4, 6…) possono rappresentare un modello di un monostrato di cromofori organici legati ad una superficie a base silicea.* - - O R Si O O R Si O Si OR O - - R O O O O Si O Si R R Si O Si OR O O R R Si O Si OO R O O Si Si R O O O O Si O Si R R -O * Pozdniakova, Yu. A.; Lyssenko, K. A.; Korlyukov, A. A.; Blagodatskikh, I. V.; Auner, N.; Katsoulis, D.; Shchegolikina, O. I. Eur. J. Inorg. Chem. 2004, 1253-1261 66 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Sintesi di anelli ciclotetrasilossanici Formula generale: [4-X-C6H4Si(O)OR]4 (R=Na, SiMe3 X = Cl, Br, CH2Cl, CH=CH2). X X X X EtO Si OEt OEt X X X Me3SiCl, pyridine NaOH, H2O EtOH, r.t. X X O Si OSi O O O Si O 4 Na Si O O resa 40-80% X = Cl, Br, CH=CH2, CH2Cl M. Ronchi, M. Pizzotti, A. Orbelli Biroli, P. Macchi, E. Lucenti, C. Zucchi, J. Organom. Chem., 2007, 692, 1788-1798 n-hexane, ∆ - NaCl O Si Si OSi Si O O O Si O Si O Si O Si resa 40-70% - solubilità in solventi organici - stabilità del legame Si-O-Si 67 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Modelli cromoforici NLO attivi N I I I O Si Si OSi Si O O Si O Pd(PPh3)2Cl2, CuI +4 Et3N, THF, ∆ SiO Si O Si yield: 47% H 1) tBuLi, Et2O, -78°C Br O Si Si OSi Si O Br O O O Si Si OSi Si O 2) I2, Et2O, -78°C Br N N N I O N Si O O Si O SiO Si O Si Br O Si O Si O Si 68 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Effetti cooperativi: cromofori non indipendenti µβEFISH × 10-48 (esu) (1.91 µm) composto N N (solvente CHCl3) N N Si O Si Si O O µ (D) β × 10-30 (esu) 68 3.08 22 318 3.64 87 238 3.96 60 (solvente CHCl3) 9.00 22 O Si Si O Si O Si O composto µβEFISH × 10-48 (esu) (1.91 µm) N 198 O Si µ (D) β × 10-30 (esu) Si O Si O Si O Si N N N N N 839 O Si Si O Si Si O O O Si 10.53 80 O Si O Si O Si Si O Si O Si O Si N N N N N 780 O Si Si O Si Si O O O Si 11.30 69 O Si O Si O Si Si O Si O Si O Si 69 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Self Assembled Acentric Multilayers Sinthesys 70 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS i => ii => iii => i) Deposizione; ii) Rotazione rapida; iii) Riscaldamento Materials construction via Layer-by-layer siloxane self-assembly Condensation Chemistry Si O H + Cl Si OH + OH Si Si Si O Si Si O Si Marks,T.J.Acc. Chem. Res. 1996, 29, 197-202; Marks,T.J.,Ratner,M.Angew.Chem.Int.Ed.Engl.1995,34, 155-173. 71 Organized self assembled monolayers with Zwitterionic Chromophores I I I I CN S OH OH OH N GLASS, QUARZ, SILICON SiX3 Si O Si O Si O O O O O O O IN SOLUTION ∆ X = Cl, I, OR UV-Vis 1 Na CN NC NC CN 0.9 S S NC CN CN S 0.8 Absorbance 0.7 0.6 0.5 N N 0.4 N 0.3 0.2 0.1 0 300 400 500 600 Wavelength (nm) 700 800 O Si O O O Si O O O Si O O Facchetti, A. ; van der Boom, M. E.; Abbotto, A. ; Beverina, L.; Marks, T. J.; Pagani, G. A. Langmuir 2001, 17, 5939-5942. 72 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS 73 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS NLO characterization 100 SHG Response 80 χ(2)zzz ~5.0 × 10-8 esu (~20 pm/V) 60 40 • bleaching effect • depolarization due to chromophore-chromophore interactions 20 0 0 10 20 30 40 50 60 70 Angle of Incidence Zwitterionic chromophores may be problematic for this approach 74 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Self-limiting chemisorptive siloxane self assembly HO OH Silica, glass-like reactivity Reactive Functionalities I N O N N OH OH OH O O O Si O O Si Si Si O O OO O Si O O Si O Si O Si O O O O O O O O Si Si Si O Si O O O O HO OH Me I Si I Cl HO PEPOH HO HO PEPOH Me N Me N N OH HO N N Me HO Cl ClCl Si O Cl Si Cl O Si Cl ClCl Si O O O O Si Si O OH N N N Me Me I I N I I N N I I N I O Si O Si O Si O O O O O O O Si O O O Si O O O Si O O O Si O O O N N I I Si O O Me N N O N N Si O O SA-PEPOH 75 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Self Assembled Acentric Multilayers Sinthesys OH OH OH O O O Si O O Si Si Si O O OO O Si O O O Si Si O Si O O O O O O Si O Si O Si O Si O O O O HO OH O S A S Capping layer Si O O O O Si Si O OH N N M O N O L A Y E R Me Chromophore layer Coupling layer Me N N Me N N Repeat O N N N I I I Si O O O Si O O O SAS Si O O SA-PEPOH 76 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Self Assembled Acentric Multilayers Synthesis repeat (i) (iii) (ii) (i-iii) Substrate (i) Coupling reagent, (ii) Organic Chromophore, (iii) Capping reagent, I O N SiX3 Et O R S HCN OH OH Cl Cl Cl Si O Cl Si Cl O Cl Si Cl Cl X = Cl, I, OR 77 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Self Assembled Acentric Multilayers Characterization N N Me SA-PEPOH2 N N SA-AZO N N N+ X- 1 2 3 4 5 78 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Self Assembled Acentric Multilayers Characterization Surface Morphology Atomic Force Microscopy (AFM) Film Composition X-Ray Photoelectron Spectroscopy (XPS) Thickness, Roughness X-Ray Reflectivity (XRR, AFM) Wettability Contact Angle Measurements (ACA) Chromophore Density Optical Transmission Spectroscopy (UV-VIS) Chromophore Alignment Second Harmonic Generation (SHG) Facchetti, A.; Abbotto, A.; Beverina, L.; Van der Boom, M. E.; Dutta, P.; Evmenenko, G.; Pagani, G. A.; Marks, T. J. Chem. Mater. 2003, 15(5), 1064-1072. 79 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Self Assembled Acentric Multilayers Characterization – Film quality and regular growth UV-Vis (Absorption) A b so rb an ce 0,16 0,14 0,12 y = 0,0249x R2 = 0,9731 SA-PEPOH 0,10 0,08 0,06 0,04 0,02 N 0,00 0 1 2 3 4 5 6 CH3 N N n°of Trilayers 200 XRR (Thickness) Thickness (A) 180 160 HO y = 33.845x 2 R = 0.9831 140 120 100 80 60 40 20 0 0 1 2 3 4 5 6 n° of Trilayers 80 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS OH Self Assembled Acentric Multilayers Characterization – Film morphology 1.0 µm 1.0 µm 1 layer 0 2 layers 3 layers AFM of SA PEP-OH on Silicon Substrates Layers 4 layers 5 layers 1 2 3 4 5 RMS (Å) 2.4 4.8 7.0 8.9 11.2 81 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Self Assembled Acentric Multilayers Characterization - SHG SA-PEPOH N CH3 N N HO 2) χ (zzz = 10-8 31 x esu (128 pm/V) OH SHG Response (a. u.) 5 y = 0.7159x 4 2 R = 0.9886 3 2 1 0 0 1 2 3 4 5 6 n°of Trilayers 82 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Is the story over? NO! 1. Consider the Gymn of the monopodal and of the bipodal 2. Why not being Bio-inspired? eM N Me N N N I I iS O Si O O O O O SA - 2 83 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS UV-Vis Characterization: solution Me N Me N Me Me N Me N N Me N N Me Me N N N 3 I N 1 N N I N I N 4 Me N 2 Me N Me N 5 I Me N Me N Me N I I 6 84 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Me Dibranched Chromophore Architecture on Covalent Self-Assembly, Thin-Film Microstructure Me N Me N Me N N N Me N Me N N Me N Me N N Me N Me 0,35 Absorbance (a. u.) 0,30 CH2 Me 0,25 N Me N 0,20 0,15 N N Si O O O 0,10 0,05 O 0,00 300 350 400 450 500 550 Si O O 600 Wawalength (nm) Facchetti, A.; Beverina, L.; Van der Boom, M. E.; Dutta, P.; Evmenenko, G.; Shukla, A. D.; Stern, C. E.; Pagani, G. A.; Marks, T. J. J. Am. Chem. Soc. 2006, 128(6), 2142-2153. 85 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS UV-Vis Characterization: SA films Me Me N N Me N N O H O H O N N I I O Me N N I I Si O O O H Si O O O Si O O O SA-1 Me Me Substrate Me Me N N N N N N Me I I N I I O Me I N (i) I Si O O I Si O O O Si O O O Si O O O Si O O I SA-3 N O Si O O O Si O O SA-IBnS Me (ii) N Me N N O Si O O Si O O O N I I I O N Me N N I I N Si O O O Si O O O Si O O SA-2 N I I Si O O I I I I O N Me N Me N Me N Me N O Si O O O Si O O O Si O O SA-4 86 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS SA films Characterization: SHG signals 2) χ (zzz esu (140 pm/V) 2.0 SHG Response (a. u.) SHG Response (a. u.) 2.0 1.6 1.2 0.8 0.4 0.0 = 34 x 10-7 N 1.6 CH3 N 1.2 0.8 0.4 0.0 0 10 20 30 40 50 Angle of Incidence (°) 60 70 0 10 20 30 40 50 60 70 Angle of Incidence (°) 87 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS Case 2 study of NLO Phoenomena: MULTIPHOTON PROCESSES excited state 3-D micro and nano-fabrication; MEMS, bioMEMS: lab-on-a-chip 800 nm ground state Optical limiting via two photon absorption Perry et al Nature 1999, 398, 51-54. IR Imaging in tissues – Immunological Assays 600 Output Intensity (GW/cm2) solvente 500 400 300 200 100 0 0 200 400 600 800 1000 1200 1400 1600 1800 Input Intensity (GW/cm2) ……really,a new challenge for organic materials ! 88 Dept. Dept. Materials Science, Science, Univ. Univ. MilanoMilano-Bicocca Photonics and Biophotonics Organics Synthesis - PhoBOS