Three-photon Absorption Properties Research Articles

Regioisomers containing triarylboron-based motifs as multi-functional photoluminescent materials: from dual-mode delayed emission to pH-switchable room-temperature phosphorescence.

Triarylboron compounds have been established as promising candidates in optoelectronic applications. However, realizing multi-functional properties in triaryl boron-based materials remains challenging. Herein, we present two regioisomers, 1 and 2, designed judiciously by connecting a dimethylamino donor and a dimesitylboryl acceptor at 1,4 and 2,6-positions of the naphthalene spacer, respectively. Both compounds 1 and 2 display simultaneous, delayed fluorescence and persistent room-temperature phosphorescence (580 nm, τ av = 168 ms, Φ = 76% for 1; 550 nm, τ av = 129 ms, Φ = 88% for 2 in 1 wt% PMMA), with the delayed fluorescence bands being sensitive to doping concentration (in PMMA). Notably, compound 1 in 1 wt% PMMA films demonstrates a reversibly switchable single-molecule phosphorescence from orange (580 nm) to green (λ Ph = 550 nm, τ av = 42 ms) in response to pH, which can be utilized for anti-counterfeiting applications. These results were further corroborated by studying the respective cationic salts 1-OTF and 2-OTF. Moreover, 1 and 2 exhibited blue-shifted fluorescence in response to mechanical pressure. Compound 2 also showed three-photon (σ3P) absorption properties which were better compared to those of compound 1.

Rational Design of Cyclometalated Iridium(III) Complexes for Three-Photon Phosphorescence Bioimaging.

Compared to 2PE (two-photon excitation) microscopy, 3PE microscopy has superior spatial resolution, deeper tissue penetration, and less defocused interference. The design of suitable agents with a large Stokes shift, good three-photon absorption (3PA), subcellular targeting, and fluorescence lifetime imaging (FLIM) properties, is challenging. Now, two IrIII complexes (3PAIr1 and 3PAIr2) were developed as efficient three-photon phosphorescence (3PP) agents. Calculations reveal that the introduction of a new group to the molecular scaffold confers a quadruple promotion in three-photon transition probability. Confocal and lifetime imaging of mitochondria using IrIII complexes as 3PP agents is shown. The complexes exhibit low working concentration (50 nm), fast uptake (5 min), and low threshold for three-photon excitation power (0.5 mW at 980 nm). The impressive tissue penetration depth (ca. 450 μm) allowed the 3D imaging and reconstruction of brain vasculature from a living specimen.

Superior multiphoton absorption properties in colloidal Mn-doped CsPbCl3 two-dimensional nanoplatelets

We have studied the two- and three-photon absorption (2PA and 3PA) properties of Mn-doped CsPbCl3 two-dimensional nanoplatelets (2D NPs) and cubic nanocrystals. Compared with their cubic counterparts, the Mn-doped 2D NPs exhibit stronger quantum confinement effects that can more efficiently enhance their dopant-carrier exchange interactions and multiphoton absorption. More specifically, the maximum volume-normalized 2PA and 3PA cross sections of the 2D NPs were 6.8 and 7.2 times greater than those of their cubic counterparts, respectively, reaching up to 1237 GM/nm3 in the visible light band and 2.24×10−78 cm6·s2·photon−2/nm3 in the second biological window, respectively.

Solvent effects on the fluorescence and effective three-photon absorption of a Zn(II)-[meso-tetrakis(4-octyloxyphenyl)porphyrin

The fluorescence and effective three-photon absorption (3PA) properties of Zn(II)-[meso-tetrakis(4-octyloxyphenyl)porphyrin] (labeled Zn(II)-porphyrin) dissolved in three different polar solvents were systematically investigated. The electrochemical and photophysical properties of Zn(II)-porphyrin were investigated by 1H NMR spectra, IR spectra, mass spectroscopy, and electronic absorption spectra. The fluorescence emission of Zn(II)-porphyrin in three different solvents excited at the wavelengths of 420 nm (Soret band) and 550 nm (Q-band) were analyzed. By performing Z-scan experiments with femtosecond laser pulses at a wavelength of 800 nm, the effective 3PA process of Zn(II)-porphyrin in three different solvents was observed and the underlying mechanism was discussed in detail. It is found that the fluorescence spectra slightly depend on the polarity of the solvent. Interestingly, the effective 3PA properties of Zn(II)-porphyrin strongly depend on the solvent polarity. The lower the solvent polarity is, the larger effective 3PA cross-section is. Low polar solvents are beneficial to applications of Zn(II)-porphyrin in optical limiting, photodynamic therapy, etc.

Two- and three-photon absorption properties of fan-shaped dendrons derived from 2,3,8-trifunctionalized indenoquinoxaline units: synthesis and characterization

Fan-shaped dendrimers are synthesized and experimentally found to possess strong two-/three-photon absorption in the femtosecond regime.

Enhanced three-photon absorption in CdSe/CdS core/shell nanocrystals in near-infrared

Colloidal CdSe nanocrystals are synthesized and successively overcoated with CdS monolayers (MLs). The three-photon absorption (3PA) properties are measured by Z-scan and nonlinear transmission techniques with 80 fs laser pulses at 1250 nm in the near-infrared. The 3PA enhancement factor due to the overcoating of three ML CdS was 850, significantly larger than that caused by a size increase of the CdSe cores. The 3PA enhancement mainly originates from the reduction of nonradiative traps on the cores’ surface. The effects of a local field and intrinsic piezoelectric polarization are also discussed.

Packing of Large Two- and Three-Photon Activity Into Smallest Possible Unsymmetrical Fluorene Chromophores.

The quantum chemical study of one-, two-, and three-photon absorption (1PA, 2PA, and 3PA) properties for a set of compact fluorene derivatives (FD) with combination of different donor and acceptor moieties on both sides of fluorene ring system is presented. The main goal of the study is to pack large two-photon (2P) and three-photon (3P) activity into smallest possible chromophore. Linear, quadratic, and cubic response time-dependent density functional theory was used to calculate 1PA, 2PA, and 3PA properties, respectively. We used CAMB3LYP/cc-pVDZ level of theory for all the property calculations. The 2P and 3P transition probabilities were recalculated using two-state model approach and found to be in good agreement with the response theory results for first excited state. To include the contributions from higher states, the three-state model was also employed to recalculate the 2P transition probabilities and found to be in excellent agreement with response theory. The 2P/3P tensor elements were also analyzed to find reasons behind large 2P/3P activities. All the orbitals involved in transition processes were studied in detail by both molecular orbital pictures (qualitatively) and overlap diagnostic Λ-values (quantitatively). The study reveals that the novel fluorene derivatives FD-12 and FD-13 have shown large 2PA cross-section values of 1100 G.M. and 1030 G.M.; and 3PA transition probabilities of 6.10 × 10(10) a.u. and 4.85 × 10(10) a.u., respectively, for transition S0 → S1. The largest 3PA transition probability of 4.04 × 10(11) a.u. was found with FD-12 for S0 → S2 excitation. The linear relationship between Λ-values and 2PA cross-section values was also studied.

Ab initio study of solvent-dependent one-, two- and three-photon absorption properties of PRODAN-based chemo-sensors

In this work, we study the solvent-dependent one-, two- and three-photon absorption (1PA, 2PA and 3PA) properties of 2-propionyl-6-dimethylamino naphthalene (PRODAN) and three newly synthesized20 cyclopenta[b]naphthalene derivatives, in gas phase and three different solvents, namely cyclohexane, dichloromethane and ethanol. A comparison between the calculated and the available experimental data shows that the results obtained with B3LYP/cc-pVDZ level of theory matches well with the experimental absorption data for all of these compounds. The 2P and 3P transition probabilities, for all of these systems, are found to be maximum in solvents of intermediate polarity (here, dichloromethane), which is in accordance with the experimental observation for various other systems. All the 1P, 2P and 3P transition probabilities are found to be the maximum for PRODAN as compared to other three molecules in both the gas as well as the different solvent phases (except for 3PA in gas and cyclohexane solvents). We have explained these results by meticulously inspecting the components of different transition moment vectors and the tensor elements involved. This work demonstrates the one-, two- and three-photon absorption properties of PRODAN, and three newly synthesized donor-π-acceptor systems can be enhanced in moderately polar solvents. 2SM is employed to explain the linear, quadratic and cubic response theory results, which establish that PRODAN is more active than the other systems studied.

First principles studies on one-, two-, and three-photon absorption properties of a symmetric carbazole derivative both in gas phase and solution

One-, two-, and three-photon absorption spectra of a novel symmetric carbazole derivative have been calculated by applying density functional response theory, both in gas phase and in a selection of solvents with increasing polarity. The effect from surrounding solvents is described by the polarizable continuum model. The effect of the choice of geometry, as well as the exchange–correlation functional has been carefully analyzed. It is found that the Coulomb attenuation method variant of Becke’s three-parameter exchange and the Lee–Yang–Parr correlation functional (CAMB3LYP) can reproduce very well the experimental one-photon absorption lineshape. The dielectric solutions enhance both one- and multi-photon absorption properties. Possible explanations for the discrepancy between calculated and experimental three-photon absorption cross sections have been analyzed in details. The calculation suggests that the possible involvement of excite-state absorption in the experimental measurement cannot be ruled out.

Synthesis and efficient three-photon excited green fluorescence of pyridine–triphenylamine conjugated dyes

Pyridine-end-capped triphenylamine derivatives (Py2-TPA)n (n = 1,2,4) were synthesized using palladium-catalyzed Heck reaction and characterized by 1H NMR, 13C NMR, and HRMS-MALDI-TOF. Three-photon absorption and three-photon excited fluorescence properties of chromophores (Py2-TPA)n were studied using a femtosecond Ti:Sapphire laser system. These chromophores exhibit efficient three-photon excited green fluorescence peaking at 540–590 nm. The three-photon absorption cross-section of σ3 = 6.99 × 10−79 cm6 s2 photon−2 in the femtosecond regime has been obtained from (Py2-TPA)4. The ratio of 3PA cross-sections in CH2Cl2 solution σ3 (Py2-TPA)4:σ3 (Py2-TPA)2:σ3 (Py2-TPA)1 is 6.0:4.2:1. The ratio of conjugated π-electron numbers in (Py2-TPA)n is 4.4(n = 4):2.6(n = 2):1(n = 1). The increasing the push–pull units of (Py2-TPA)n and π-electron conjugation length or increasing the extent of charge transfer from the ends to the middle aryl core results in an increase of the 3PA cross-section. The results indicate that large aromatic conjugated chromophores (Py2-TPA)n containing pyridine–triphenylamine D–A pairs and a conjugated aryl core provide a new opportunity for 3PA-materials and three-photon fluorophores for practical application.

Remarkable Effect of Iridium Cyclometalation on the Nonlinear Absorption Properties of a Quadrupolar Imine Ligand

A new type of dinuclear iridium complex, based on a quadrupolar Schiff base ligand, is synthesized and its structure fully characterized. Its linear and nonlinear spectroscopic properties are investigated, evidencing a strong contribution of the metal-to-ligand transitions not only to the linear absorption but also to the two- and three-photon absorption properties.

Three-photon absorption and vibrational spectroscopic study of 2-methylamino-5-chlorobenzophenone

In this paper, the vibrational spectral analysis and three-photon absorption properties of an organic material of 2-methylamino-5-chlorobenzophenone have been reported. The geometry and harmonic vibrational wavenumbers are calculated with the help of B3LYP density functional theory method. The detailed interpretation of the vibrational spectra has been carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology (SQM). SQM force fields have also been used to calculate potential energy distribution (PED) in order to make conspicuous vibrational assignments. The nonlinear absorption properties have been investigated in ethanol solution at 532nm using the Z-scan technique employing laser pulses of 5ns duration. Open aperture Z-scan data reveal the presence of effective three-photon absorption for ns pulses at 532nm resulting in a strong optical limiting behavior, indicating possible photonic applications.

Synthesis, tunable two and three-photon absorption properties of triazine derivatives by branches

Three novel triazine derivatives, (E)-4-(2-(4,6-dimethyl-1,3,5-triazin-2- yl)vinyl)- N,N-di-p-tolylaniline (a), 4,4′–((1E,1′E)-(6-methyl-1,3,5-triazine-2,4-diyl) bis(ethene-2,1-diyl))bis(N,N-di-p-tolylaniline) (b), and 4,4′,4′′–((1E,1′E,1′′E)-(1,3,5- triazine-2,4,6-triyl)tris(ethene-2,1-diyl))tris(N,N-di-p-tolylaniline) (c), were designed and synthesized. Their photophysical and photochemical properties were investigated systematically including single-photon absorption, nonlinear optical absorption (NOA) and up-converted fluorescence. Interestingly, the compound a with single branch showed pure three-photon absorption phenomenon, while the corresponding b and c indicated two-photon induced excited-state absorption properties, showing strong structure-dependence relationship. The results offer a method to design and synthesize organic molecules for multiphoton materials. It was noted that the three-photon cross-section value (δ3) of a was up to 1.35 × 10−76 cm6 s2. Correspondingly, the two-photon (δ2) and excited-state cross-section (δe) values of b and c also were obtained, and value of them were 485 GM and 1.03 × 10−17 cm2 for b, and 1100 GM and 1.27 × 10−18 cm2 for c, respectively.

Two-photon absorption of metal–organic DNA-probes

We report remarkable multiphoton absorption properties of DNA intercalating ruthenium complexes: (1) [Ru(phen)(2)dppz](2+); (2) [(11,11'-bidppz)(phen)(4)Ru(2)](4+); (3) [11,11'-bipb(phen)(4)Ru(2)](4+). Two-photon spectra in the range from 460 to 1100 nm were measured using the Z-scan technique. In particular, complex 2 was found to exhibit very strong two- and three-photon absorption properties, which could be an effect of symmetric charge transfer from the ends towards the middle of the conjugated dimeric orbital system. We propose that these molecules could provide a new generation of DNA binding nonlinear chromophores for wide applications in biology and material science. The combination of a large two-photon cross section and strong luminescence quantum yields for the molecules when intercalated makes the compounds uniquely bright and photo-stable probes for two-photon luminescence imaging and also promising as enhanced photosensitizers in two-photon sensitizing applications.

Molecules of ruthenium-based olefin metathesis catalysts as two- and three-photon absorbers

Three ruthenium-based complexes exhibiting catalytic activity in olefin metathesis have been examined for the presence of interesting nonlinear optical (NLO) properties. Measurements were performed by the Z-scan technique using a tunable femtosecond laser system. This initial screening for potential new applications in photonics of complexes representative of a wide family of ruthenium-based olefin metathesis catalysts has found moderately strong two-photon and three-photon absorption properties in relatively simple molecules that may lead to the development of a new class of strong nonlinear absorbers.

Highly Efficient Multiphoton‐Absorbing Quadrupolar Oligomers for Frequency Upconversion

Two series of quadrupolar diphenylamino-endcapped oligofluorenes, PhN-OF(n)-NPh (n=2-5) and PhN-OF(n)-TAZ-OF(n)-NPh (n=1-4), which have an electron-withdrawing 1,2,4-triazole (TAZ) moiety as central core, with D-π-A-π-D structural motif (D=donor, A=acceptor), have been synthesized by palladium-catalyzed Suzuki cross-coupling of 9,9-dibutyl-7-(diphenylamino)-2-fluorenylboronic acid and the corresponding (1,2,4-triazole-based) aryl halide as key step. On pumping with infrared femtosecond lasers, these oligomers showed very strong multiphoton-excited blue photoluminescence. These D-π-D and D-π-A-π-D quadrupolar oligofluorenes exhibit superior three-photon absorption properties compared to the respective D-π-A counterparts with a highest three-photon absorption cross-section (σ(3)) of up to 2.72×10(-77) cm(6) s(2) . Despite the comparable linear and multiphoton absorption properties of the two types of quadrupolar oligomers PhN-OF(n)-NPh and PhN-OF(n)-TAZ-OF(n)-NPh, only the former exhibit remarkably intense and highly efficient multiphoton-excited frequency-upconverted deep blue lasing, which gives rise to record high lasing efficiency of 0.097% and very narrow of full width at half-maximum of the lasing spectra. Our findings suggest that quadrupolar-type molecules/oligomers are superior for multiphoton excited frequency upconverted lasing to their dipolar counterparts and also provide important guidelines to design highly efficient three-photon absorption molecules for photoluminescence and lasing applications.

Degenerate Multi-Photon Properties of Spirofluorene Derivatives

Two- and three-photon absorption properties of the fluorene-based chromophores have been investigated. The two- and three-photon absorption cross-section are found to be increased with the strength of the electron donor groups in the order of N-ethylcarbazoyl (1), triphenylamino (2), and N,N-dibutylanilino (3) groups. This nonlinear absorption enhancement can be interpreted by the increase of intramolecular charge transfer facilitated by strong electron donors and the decreased detuning energy (deltaE). Furthermore, direct laser microfabrication by two-photon photopolymerization with compound 2 as a two-photon sensitizer was carried out. Laser exposure time-dependent lateral voxel size has also been studied.

Two- and Three-Photon Absorption Induced Emission, Optical Limiting and Stabilization of CdTe/CdS/ZnS Quantum Tripods System

Two- and three-photon absorption and excitation properties of CdTe/CdS/ZnS quantum tripods in chloroform have been investigated by using ~160-fs laser pulses in the spectral range of ~(1150-1650) nm. The two- and three-photon excited up-conversion emission is located around 740-nm position; the emission intensity follows the square law and cubic law on the excitation intensity for the former and the latter, respectively. The nonlinear transmission and output/input characteristics have been measured at a two-photon absorption wavelength of 1175 nm and a three-photon absorption wavelength of 1580 nm separately. Fairly good optical power limiting and stabilization performance of this material have been achieved.

Two- and three-photon absorption of organic ionic pyrylium based materials

Pyrylium dyes having the same basic chemical structure, differing only to a specific substituent, have been used as novel materials for multiphoton three-dimensional data storage. Electronic absorption spectra, two-photon and three-photon absorption properties of this class of pyrylium dyes, have been studied theoretically and compared to experimental results. The effects of the counteranion, the surrounding solvent, and electron releasing and electron withdrawing groups in specific positions of the basic structure have been explored in detail. It is argued that on grounds of the quality of experimental spectroscopic agreement, the computed two- and three-photon data may be used in pulse propagation simulations of three-dimensional recording in optical memories.

Solvent Effects on the Three-Photon Absorption of a Symmetric Charge-Transfer Molecule

We present a theoretical study of the solvent-induced three-photon absorption cross section of a highly conjugated fluorene derivative, performed using density functional (DFT) cubic response theory in combination with the polarizable continuum model. The applicability of the often used two-state model is examined by comparison against the full DFT response theory results. It is found that the simplified model performs poorly for the three-photon absorption properties of our symmetric charge-transfer molecule. The dielectric medium enhances the three-photon absorption cross section remarkably. The effects of solvent polarity and geometrical distortions have been carefully examined. A detailed comparison with experiment is presented.