资源描述
Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Optical Limiting Materials,Rupesh Narayana-Prabhu,Contents,Introduction,Optical limiters and Reverse Saturable Absorption,Chromophores,Porphyrins,Phthalocyanines,Fullerenes,Optical Limiting Studies,Conclusion,Introduction,Lasers are used in: CD players, scanners, laser pointers, spectroscopic studies, optical sensors, astronomy, military, etc.,Damages skin tissues and causes blindness.,“Smart materials” transparent under ordinary ambient light conditions, but can absorb or block intense laser light over a broad wavelength range.,Development of optical limiting materials that rely on reverse saturable absorption.,Optical Limiting Materials,Nonlinear optical materials whose transmittance decreases significantly with increasing light fluence.,Beyond the threshold, the flux of photons remains constant.,Output fluence,Input fluence,threshold,Linear transmittance,ideal,real,Absorption,Refraction,Reflection,Scattering,Physical processes causing optical limiting effects,S,One photon absorption,S,n,G,S,1,T,n,T,1,E,G,k,isc,k,SG,k,TG, = absorption cross section,Five-level energy diagram,Sequential Two photon absorption,Excited state which could absorb,G,S,1,S,n,T,n,T,1,E,G,k,isc,k,SG,k,TG,S,T,Dependence on the laser pulse,Shorter pulse duration,Longer pulse duration,T,n,T,1,k,isc,G,S,1,S,n,E,G,k,SG,S,Dependence on the laser pulse,Shorter pulse duration,Longer pulse duration,X,Three-level energy diagram,Dependence on the laser pulse,G,S,1,S,n,T,n,T,1,E,G,k,isc,k,SG,k,TG,S,T,Shorter pulse duration,Longer pulse duration,G,S,1,S,n,E,G,k,SG,S,Three-level energy diagram,Four-level energy diagram,Reverse Saturable Absorption (RSA),The excited state cross section is larger than the ground state cross section.,S,/,G, 1,(or),T,/,G, 1,Materials showing RSA become more,opaque,upon exposure to light of suitable wavelength.,T,n,T,1,G,S,1,S,n,E,G,k,isc,k,SG,k,TG,S,T,Reverse Saturable Absorption vs. Two Photon Absorption,Criteria for Optical Limiting,Sequential TPA,ES, ,G,.,ES, the pulse duration.,Wide range of incident intensities.,Low threshold.,Large non linear absorption over a broad spectral bandwidth.,ES,/ ,G,ratio.,Saturation fluence.,Output fluence,Input fluence,Linear transmittance,threshold,G,S,1,S,n,T,n,T,1,E,G,k,isc,k,SG,k,TG,S,T,indanthrone dye,Reverse Saturable Absorber Chromophores,calixnarene,thienyleneethynylene,tetraphenyldiamines,Organic Molecules,Stilbene derivatives,Reverse Saturable Absorber Chromophores,Carbon Nanotubes,Metal Clusters,Porphyrins,Phthalocyanines,Fullerenes,Techniques used,Z-scan Technique,Nd:YAG laser,sample,-Z,Photodetector,+Z,Output vs. input fluence,Transmission vs. input energy,Output fluence,Input fluence,Input energy,Transmission,Porphyrins and Phthalocyanines,Porphyrins and Phthalocyanines,Versatility, architectural flexibility, high thermal and environmental stability, inexpensiveness, non-toxicity and ease of processing.,Tailoring the electronic properties:,70 different metal atoms,Substitution on the ring,Axial substitution,Porphyrins: Early studies,80ps pulse delay,Tetraphenyl porphyrins,Blau, W.; Byrne, H.; Dennis, W. M.; Kelly, J. M.,Opt. Commun.,1985,56, 25,Molecule,f,G,(10,-17,cm,2,),S,/,G,T,/,G,H,2,TPP,9 ns,1.6,3.8,S,1,S,n,CoTPP,0.1ns,5,3.0,T,1,T,n,Fast ISC due to heavy atom effect,G,S,1,S,n,T,n,T,1,E,G,k,isc,k,SG,k,TG,S,T,Effect of metal centre and meso substituent,Nd:YAG laser: 532nm,Pulse delay: 80ps, 14ns,McEwan. K. J.; Bourhill. G.; Robertson. J. M.; Anderson. H. L. Journal of Nonlinear Optical Physics & Materials,2000,.,9, 451,X = 2H,Q- bands are red-shifted through 2H, Zn and Pb.,Pb derivatives are better optical limiters.,G,10,-17,cm,2,S,10,-17,cm,2,T,10,-17,cm,2,TTP (H),1.71,4.0,2.5,TTP (Zn),3.07,7.3,4.1,TTP (Pb),0.63,-,6.7,TTMSAP (H),1.91,8.3,5.9,TTMSAP (Zn),0.58,17,18,TTMSAP (Pb),0.53,-,24,McEwan. K. J.; Bourhill. G.; Robertson. J. M.; Anderson. H. L. Journal of Nonlinear Optical Physics & Materials,2000,9, 451,Effect of conjugation,n = 1,n =2,n =10-15,Qureshi, F. M.; Martin, S. J.; Long, X.; Bradley, D. D. C.; Henari, F. Z.; Blau, W. J.; Smith, E. C.; Wang, C. H.; Kar, A. K.; Anderson. H. L. Chemical Physics,1998,231, 87,% transmittance:,60%, 40% and 35%,exc,=,532nm,pulse delay: 500ps,n=1,n=2,n=10-15,Greater the conjugation, the better is the optical limiting performance.,(,t-,Bu),4,PcInCl,(,t-,Bu),4,PcIn(,p,-CF,3,C,6,H,4,),Bulky groups enhances optical limiting performances.,Dini, D.; Barthel, M.; Hanack, M.,Eur. J. Org. Chem.,2001,3759,exc,=,532nm,pulse delay: 5ns,Effect of,- and axial- s,ubstituents,Indium Phthalocyanines,Indium Naphthalocyanines,Optical limiting properties: similar to InPcs,Increase in solubility.,Q-band,red,shifts to 800nm,InPcs: Optical limiter in,blue,region,InNcs: Optical limiter in,red,region,Dini, D.; Barthel, M.; Hanack, M.,Eur. J. Org. Chem.,2001,3759,Effect of Axial Substitution,R,III,R,IV,a,H,t-Bu,c,H,CH,2,CN,b,H,CHO,d,CN,CN,EWG on axial position improve the optical limiting performances,.,Dini, D.; Barthel, M.; Hanack, M.,Eur. J. Org. Chem.,2001,3759,Titanium Phthalocyanines,exc,=,532nm,pulse delay: 5ns,Auger, A.; Blau, W., J.; Burnham, P. M.; Chambrier, I.; Cook, M. J.; Isare, B.; Nekelsona, F.; OFlaherty, S. M.,J. Mater. Chem,.,2003,13, 1042,Heavy Atom Effect,1,4,8,11,15,18,22,25-,octaalkylphthalocyanines,R = n-C,6,H,13,R = n-C,10,H,21,Heavy central atom: better optical limiting response,Im,(3),(esu),R = n-C,6,H,13,1,M = H, H,(6.6 1.3) x 10,-12,6,M = Zn,(1.5 0.3) x 10,-11,R = n-C,10,H,21,2,M = H, H,(5.8 1.1) x 10,-12,7,M = Zn,(9.1 1.8) x 10,-12,Auger, A.; Blau, W., J.; Burnham, P. M.; Chambrier, I.; Cook, M. J.; Isare, B.; Nekelsona, F.; OFlaherty, S. M.,J. Mater. Chem,.,2003,13, 1042,Effect of,- and axial- s,ubstituents,The absence of any group with strong electronic character in Ar substituents:,small decreases of transmittance.,high threshold intensity value.,8,8,5,5,Vagin, S.; Barthel, M.; Dini, D.; Hanack, M.;,Inorg. Chem.,2003, 42, 2683,Gallium Derivatives,F atoms increases solubility.,8,is a better optical limiter.,Yang, G. Y.; Hanack, M.; Lee, Y. W.; Chen, Y.; Lee, M. K., Y.; Dini, D.;,Chem. Eur. J.,2003, 9, 2758.,exc,=,532nm,pulse delay: 5ns,Polypyridyl Porphyrins,Duncan, T. V.; Rubtsov, I. V.; Uyeda, H. T.; Therien, M. T.,J. Am. Chem. Soc.,2004,126,9474,(nm),(G.S.),(nm),(E.S.),T,(,s),E,/,G,RuPZn,638,884,44,75,OsPZn,640,964,0.86,163,RuPZnA,682,931,24,227,OsPZnA,704,985,1.08,135,RuPZnOs,710,1000,.079,324,570nm,605nm,695nm,exc,Pulse delay = 1ns,Fullerenes,Fullerenes: Early studies,Tutt and Kost (1992): C,60,in toluene solution is an excellent optical limiter.,C,70, C,76, C,78,and C,84,have also been investigated.,C,60,is by far the best in fullerene family.,Tutt, L. W.; Kost, A.,Nature,1992,356,225.,Range of interest: 600nm-near IR,Triplet-triplet absorption,G,S,1,T,n,T,1,E,G,k,isc,k,SG,k,TG,T,Solvent Dependence,Solvent independent, but varies in solvents containing EDG.,N,N-diethylaniline (DEA) or N,N-dimethylaniline (DMA):,Inter-molecular electron transfer.,0.05,0.21,C,60,+ h, C,60,*,C,60,* + DEA (C,60,-DEA)* C,60,+ DEA,+,Ghosh, H. N.; Pal, H.; Sapre, A. V.; Mittal, J. P.,J. Am. Chem. Soc.,1993,115,11722.,Medium Dependence,Weaker responses in polymethylmethacrylate (PMMA) or poly(propionylethyleneimine) (PPEI) or sol-gel glasses.,Medium Viscosity dependent,.,Kost, A.; Tutt, L.; Klein, M. B.; Dougherty, T. K.; Elias, W. E.,Opt. Lett.,1993,18,334.,C,60,in toluene,C,60,in PMMA,Fullerene derivatives,Derivatization increases the solubility in various solvents and eases polymerization.,15,16,17,Sun, Y.-P.; Riggs, J. E.,Chem. Mater.,1997,9,1268,Similar optical limiting efficiencies of,C,60,and its derivatives.,Sun, Y.-P.; Riggs, J. E.,Chem. Mater.,1997,9,1268,Multiple-functionalized methano-C,60,dicarboxylates,Optical limiting responses of the multiple functionalized methano-C,60,dicarboxylates are all weaker than those of the parent C,60,and the mono-functionalized derivatives.,1,2,3,4,1,2,4,3,532nm,5ns,C,60,-polystyrene polymers,1,2,1,C,60,The optical limiting responses of pendant polymers are weaker than those of C,60,or the model compounds.,Sun, Y. -P.; Lawson, G. E.; Huang, W.; Wright, A. D.; Moton, D. K. Macromolecules,1999,32, 3747.,Optical limiting mechanism,Is Reverse Saturable Absorption the only mechanism?,Optical limiting performances in solid matrix different from that in solution?,G,S,1,S,n,T,n,T,1,E,G,k,isc,k,SG,k,TG,S,T,Factors,Medium viscosity,Concentration of C,60,As viscosity and concentration increases, the system has a weak optical limiting property.,Bimolecular processes ?,Bimolecular processes,Self quenching,Annihilation,Excimer-like state,Riggs, J. E.; Sun, Y.-P.,J. Phys. Chem.,A.,1999,103, 485.,Modified reverse saturable absorption model,G,S,1,S,n,T,n,T,1,S,ex,T,ex,k,S,ex,G,T,ex,G,k,Riggs, J. E.; Sun, Y.-P.,J. Phys. Chem.,A.,1999,103, 485.,Phthalocyanine-fullerene derivative,M = Cu,CuPc-C,60,is better optical limiter than CuPc or C,60,itself.,Zhu, P.; Wang, P.; Qiu, W.; Liu, Y.; Ye, C.; Fang, C.; Song, Y. Appl. Phys. Lett.,2001,78, 1319.,Excimer laser:,308,nm, 20ns,UV-400 nitrogen laser:,337,nm, 8ns,Nd:YAG laser:,532,and,1064,nm, 12ns,Georgakilas, V.; Guldi, D. M.; Signorini, R.; Bozio, R.; Prato, M.,J. Am. Chem. Soc,. 2003,125, 14268-14269,Carbon Onions,Conclusion,Optical limiting materials rely on the phenomenon of reverse saturable absorption.,Porphyrins, phthalocyanines, naphthalocyanines and fullerenes are good candidates in the visible-near IR range.,Become more opaque upon exposure to light of suitable wavelength and hence could be used to protect eye or optical sensors from the intense laser source.,Acknowledgement,Prof. Russell H. Schmehl,Dr. D. Kumaresan,Heidi Hester,Srivathsa Vaidya,Kalpana Shankar,David Karam,Monica Posse,The Chemistry Department, Tulane University,Friends at Tulane,
展开阅读全文