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![1PA ( dashed line ) and 2PA ( solid line ) spectra, and two-photon polarization ratio, Ω ( light dotted line ) for: phenylalanine, tyrosinamide, tryptophan. The abscissa corresponds to the excitation wavelength of the 2PA case. The 1PA spectra are plotted at twice their excitation wavelength. The molecular structures are shown as insets in each graph. Reproduced with permission from [42]. © 1993, Elsevier](profile/Joseph-Perry-7/publication/226779105/figure/fig3/AS:302249315192834@1449073260368/PA-dashed-line-and-2PA-solid-line-spectra-and-two-photon-polarization-ratio-O.png)
1PA ( dashed line ) and 2PA ( solid line ) spectra, and two-photon polarization ratio, Ω ( light dotted line ) for: phenylalanine, tyrosinamide, tryptophan. The abscissa corresponds to the excitation wavelength of the 2PA case. The 1PA spectra are plotted at twice their excitation wavelength. The molecular structures are shown as insets in each graph. Reproduced with permission from [42]. © 1993, Elsevier
Source publication
Two-photon absorption, the process by which an excited molecule or material is produced by the simultaneous
absorption of two photons, has been studied extensively in recent years, from both fundamental and application
points of view. On one side, the field has been expanded with the measurement of two-photon absorption
spectra and cross sections f...
Contexts in source publication
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... of proteins or to distinguish the background fluorescence signal when an external probe is introduced in the sample. The 2PA spectra of phenylalanine and tyrosinamide, both containing a substituted benzene in their structure, together with that of tryptophan (a substituted indole) have been measured in aqueous phosphate buffer (see Fig. 4) [42]. For phenylalan- Reproduced with permission from [42]. © 1993, Elsevier ine, both the 1PA and 2PA spectra exhibit a rich vibronic structure, which is different in the two spectra due to the coupling of a different normal mode with the electronic state in each case (in the 2PA case, the longest wavelength band is detected at 535 ...
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... transition lies about Table 9 2PA properties of squaraines and cyanines. The solvent in which the measurement was performed is indicated in parenthesis after the molecular structure Molecule Two-Photon Absorbing Materials and Two-Photon-Induced Chemistry Table 2 in the reference cited (the relative intensity between the two peaks is different in Fig. 4 from the same ...
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... around the focus of the laser beam (this volume is often referred to as voxel). The film can then be developed using a solvent (ethanol, in this particular case) to remove the resin from the unexposed areas. The microstructure demonstrated in this study was a helical coil of 7 µm diam- eter and 50 µm length with a line cross section 1.3 µm×2.2 µm (Fig. 14, top). Subsequent work by the same group [167,168] using SCR500 includes fabri- cation of microscale model of a bull with a height of ∼7 µm and a length of ∼10 µm (Fig. 14, bottom) using a 780 nm/150 fs ...
Context 4
... the resin from the unexposed areas. The microstructure demonstrated in this study was a helical coil of 7 µm diam- eter and 50 µm length with a line cross section 1.3 µm×2.2 µm (Fig. 14, top). Subsequent work by the same group [167,168] using SCR500 includes fabri- cation of microscale model of a bull with a height of ∼7 µm and a length of ∼10 µm (Fig. 14, bottom) using a 780 nm/150 fs ...
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Epoxy-polysiloxane composites of cationic polymerization were synthesized based on epoxy resin and tetraethoxysilane. The thermophysical properties of the resulting polymers were studied. It was established that, as the filler content increases from 0.5 to 3 wt %, the molecular weight of an intermodal segment increases and the cross-linking density...
Citations
... For molecular systems absorbing two photons with the same frequency, the total number of molecules n abs excited by TPA per unit volume per unit time n abs is given by [26] ...
Two-photon polymerization (TPP) is an advanced 3D fabrication technique capable of creating features with submicron precision. A primary challenge in TPP lies in the facile and accurate characterization of fabrication quality, particularly for structures possessing complex internal features. In this study, we introduce an automated brightfield layerwise evaluation technique that enables a simple-to-implement approach for in situ monitoring and quality assessment of TPP-fabricated structures. Our approach relies on sequentially acquired brightfield images during the TPP writing process and using background subtraction and image processing to extract layered spatial features. We experimentally validate our method by printing a fibrous tissue scaffold and successfully achieve an overall system-adjusted fidelity of 87.5% in situ. Our method is readily adaptable in most TPP systems and can potentially facilitate high-quality TPP manufacturing of sophisticated microstructures.
... Figure 7b shows a typical photocuring process. Other advanced VP processes include continuous liquid interface production (CLIP) and two-photon polymerization (2PP) [72][73][74][75]. CLIP is a proprietary process where a light source selectively cures a photosensitive liquid resin that is continuously flowing during printing. ...
Ceramic materials are used in various industrial applications, as they possess exceptional physical, chemical, thermal, mechanical, electrical, magnetic, and optical properties. Ceramic structural components, especially those with highly complex structures and shapes, are difficult to fabricate with conventional methods, such as sintering and hot isostatic pressing (HIP). The use of preceramic polymers has many advantages, such as excellent processibility, easy shape change, and tailorable composition for fabricating high-performance ceramic components. Additive manufacturing (AM) is an evolving manufacturing technique that can be used to construct complex and intricate structural components. Integrating polymer-derived ceramics and AM techniques has drawn significant attention, as it overcomes the limitations and challenges of conventional fabrication approaches. This review discusses the current research that used AM technologies to fabricate ceramic articles from preceramic feedstock materials, and it demonstrates that AM processes are effective and versatile approaches for fabricating ceramic components. The future of producing ceramics using preceramic feedstock materials for AM processes is also discussed at the end.
... This feature attracts the attention of many research groups and may be applied in various emerging technologies, such as three-dimensional data storage, optical power limiting, nonlinear optics, and organic light-emitting diodes. 13,15,[30][31][32][33][34][35][36][37] The dynamics of SB and quantification of the SB degree, as well as other SB details, can be obtained using time-resolved femtosecond infrared spectroscopy. This technique produces spectra of stretching vibrations of -C≡N or -C≡C-groups, which are localized on each branch of the molecule and are sensitive to SB. 22 In the symmetrical state, these vibrations form two (symmetric and antisymmetric) normal vibrational modes with close natural frequencies. ...
... where Δhωoct is a function of the solvent polarity Δ f , since D 0 and λor depend on it as can be seen in Eq. (12). The last term in Eq. (32) takes into account the invariance of the energy of the orientational polarization of the solvent during radiation (see Fig. 2). The corresponding dependence for a quadrupolar molecule can be obtained from the two-level model. ...
A three-level model of symmetry-breaking charge transfer (SBCT) in excited octupolar molecules is developed. The model describes the joint dynamics of the solvent and the dye in the excited state. For this, a distribution function in the space of two reaction coordinates is introduced. An evolution equation of this function is derived. A strict definition of the reaction coordinates is given, and its dynamic characteristics are determined. The free energy surface in the space of these coordinates is calculated. To quantify the symmetry-breaking degree, a two-dimensional dissymmetry vector is introduced. The model predicts the absence of SBCT in apolar solvents and an abrupt increase in its degree to half the maximum value in weakly polar solvents. The dye dipole moment is revealed to be directed along a molecular arm independently of the direction and the strength of the electric field of the solvent created by its orientational polarization. The conditions for the occurrence and nature of this effect are discussed. The effect of the degeneracy of excited states, which is inherent in octupolar dyes in the excited state, on SBCT is revealed. Degeneracy of energy levels is shown to lead to a significant increase in the symmetry-breaking degree. The effect of SBCT on the dependence of the Stokes on the solvent polarity is calculated and compared with the available experimental data.
... [99]. In the liquid photoresist, the photoinitiator absorbs two photons simultaneously to release a free radical that initiates the chain reaction for polymerization within the focal volume of the ultrafast laser, enabling 3D resolved nanofabrication [100]. Following the laser irradiance and subsequent development, i.e., washing out the non-illuminated regions, the polymerized material remaining in prescribed 3D forms reaches a resolution of 100 nm or above [101,102]. ...
Three-dimensional (3D) printing, also known as additive manufacturing, has undergone a phase of rapid development in the fabrication of customizable and high-precision parts. Thanks to the advancements in 3D printing technologies, it is now areality to print cells, growth factors, and various biocompatible materials altogether into arbitrarily complex 3D scaffoldswith high degree of structural and functional similarities to the native tissue environment. Additionally, with overpowering advantages in molding efficiency, resolution, and a wide selection of applicable materials, optical 3D printing methods have undoubtedly become the most suitable approach for scaffold fabrication in tissue engineering (TE). In this paper, we first provide a comprehensive and up-to-date review of current optical 3D printing methods for scaffold fabrication, including traditional extrusion-based processes, selective laser sintering, stereolithography, and two-photon polymerization etc. Specifically, we review the optical design, materials, and representative applications, followed by fabrication performance comparison. Important metrics include fabrication precision, rate, materials, and application scenarios. Finally, we summarize and compare the advantages and disadvantages of each technique to guide readers in the optics and TE communities to select the most fitting printing approach under different application scenarios.
... Over the past two decades, increasing attention has been devoted to the design and study of molecular materials with optimized two-photon absorption (TPA, a list of acronyms can be found at the end of this article) efficiency [1][2][3][4][5], because of relevant applications from photonics to biology, such as microfabrication [6][7][8][9][10][11], micromachines [12], 3D optical data processing and storage [13][14][15][16][17][18], bio-imaging [18,19], and photodynamic therapy [20][21][22][23]. Both experimental and theoretical explorations of the structure-property relationships governing TPA indicated that two critical factors determine the two-photon performances of organic chromophores: the π-conjugation length and the presence of intramolecular charge transfers [3,[24][25][26][27][28][29][30][31]. ...
One- and two-photon characterizations of a series of hetero- and homoleptic [RuL3-n(bpy)n]2+ (n = 0, 1, 2) complexes carrying bipyridine π-extended ligands (L), have been carried out. These π-extended D−π−A−A−π−D-type ligands (L), where the electron donor units (D) are based on diphenylamine, carbazolyl, or fluorenyl units, have been designed to modulate the conjugation extension and the donating effect. Density functional theory calculations were performed in order to rationalize the observed spectra. Calculations show that the electronic structure of the π-extended ligands has a pronounced effect on the composition of HOMO and LUMO and on the metallic contribution to frontier MOs, resulting in strikingly different nonlinear properties. This work demonstrates that ILCT transitions are the keystone of one- and two-photon absorption bands in the studied systems and reveals how much MLCT and LLCT charge transfers play a decisive role on the two-photon properties of both hetero- and homoleptic ruthenium complexes through cooperative or suppressive effects.
... Two-photon absorption (TPA), a third-order nonlinear optical effect [1,2] has many potential applications in physics [3], chemistry [4,5], and life sciences [6,7], where TPA can be used to excite high-excitation energy systems at long wavelengths for nondestructive photo-catalysis [8][9][10] or to observe physical processes such as two-photon excited fluorescence (TPEF) [11][12][13]. In photo-catalysis, long-wavelength pulsed lasers minimize the damage and thermal effects of the light source on the catalytic substrate, which not only allows for sustainable reactions but also eliminates thermal effects in the studied mechanism. ...
In this work, we theoretically studied the optical absorption properties of a layer-stacked cocrystal heterogeneous material Spe-TCNB cocrystal (STC) which is produced by supramolecular self-assembly of organic conjugated monomers SPE and TCNB. The highly ordered aggregate structure in the cocrystal STC will lead to intermolecular interactions such as π∼π, hydrogen bonds and van der Waals forces, resulting in significant charge transfer characteristics and large cross-sectional two-photon absorption characteristics. The physical mechanism of one-photon and two-photon charge transfer of cocrystal molecules is specifically discussed and the interaction between molecules and their role in charge transfer are quantitatively analyzed. We found that the charge transfer between molecular junctions composed of hydrogen bonds is mainly cross-bridge charge transfer, while the charge transfer between molecular junctions caused by accumulation is mainly cross-space charge transfer. This discovery is of great significance to the design of organic photoelectric functional materials.
... Additionally, the energy of the 2Ag state was determined by the two-photon absorption of (the structurally very similar) ortho-(2,2)-dimethyl-DSB, to be located at around ΔE A = 0.75 eV above 1Bu. 64 The value for Evert(B 1u ) will be used as a reference point for the following GSA calculations. On the other hand, the solvent dependence of ΔE A,B is not known from the experiment; therefore, these values should be handled with caution for the comparison with gas phase calculations. ...
State-of-the-art CASSCF/CASPT2 calculations are used to investigate the role of double excitations on the ground (GSA) and excited state absorption (ESA) spectra of distyrylbenzene (DSB), an important prototype medium-sized p-conjugated organic compound for optoelectronics. The multi-reference results are compared with linear and quadratic response TD-DFT results, revealing an incomplete description of the electronic transitions in the latter. Careful selection of the active space and basis set in the CASPT2 approach allows for a reliable description of the GSA and ESA features; cost-effective DFT-based geometries can be utilized without a significant loss of accuracy. Double excitations are shown to play a pivotal role already for higher excited states in the GSA spectrum, however without a relevant impact on the discernible spectral features. In the ESA, which shows a much more complex electronic situation, the crucial importance of double (and higher) excitations in all relevant electronic transitions indeed mandates a multiconfigurational treatment as done in the present benchmark study.
... These electron beams then used to target materials through magnets. EBE method has been implemented as development of 2D and 3D metal patterning (Rumi et al. 2008). This methods were also implemented for synthesis of Au NPs and platinum (Pt) NPs on multiwall carbon nanotubes to produce composite electrodes for sensors and energy storage applications (Hsieh et al. 2010). ...
On-going research in nanotechnology has confirmed a diversity of methods to synthesize nanoparticles (NPs) from a various range of materials. Nanotechnology is considered as a growing sector which brings together a multidisciplinary fields including biology, chemistry, physics, medicine, etc. with certain benefits. It includes ceramics, metals, semiconductors, polymers, metal oxides, etc. NPs have distinctive structural physicochemical and morphological characteristics based on their origin and synthesis methods. These are important in a wide variety of applications concomitant to electronic, optoelectronic, optical, electrochemical, environment. and biomedical fields. With the help of nanotechnology the major beneficial effects have been seen in agriculture, industrial sector and much more. This current review comes up with key applications of nanoparticles and extensive overview on various physical, chemical and bio-assisted methods. With all its emerging aspects nanoparticle has shown a huge upcoming opportunity in near future.
... By scanning the focal point through the bath of material, polymerization can be induced anywhere in the resist bath, a feature not possible with SLA or DLP in which polymerization can only occur at the surface of the vat. The 3D focal point has an ellipsoidal shape, with an equal length in the x-and y-axes, typically around 60 nm, and slightly elongated in the z-axis, this being ≈180 nm; [71] both the shape and dimensions are influenced by the laser intensity and the numerical aperture (NA) used. [72,73] Because of the small dimension of the focal point, the resolution of this technique is ≈20 nm to 5 µm: [1,74,75] final resolution is critically dependent on both the material and the printing parameters (Section 3.1). ...
Recent years have seen major advances in the developments of both additive manufacturing concepts and responsive materials. When combined as 4D printing, the process can lead to functional materials and devices for use in health, energy generation, sensing, and soft robots. Among responsive materials, liquid crystals, which can deliver programmed, reversible, rapid responses in both air and underwater, are a prime contender for additive manufacturing, given their ease of use and adaptability to many different applications. In this paper, selected works are compared and analyzed to come to a didactical overview of the liquid crystal‐additive manufacturing junction. Reading from front to back gives the reader a comprehensive understanding of the options and challenges in the field, while researchers already experienced in either liquid crystals or additive manufacturing are encouraged to scan through the text to see how they can incorporate additive manufacturing or liquid crystals into their own work. The educational text is closed with proposals for future research in this crossover field. Liquid crystals are the basis for many “smart” materials used in, for instance, soft robotics and polymer optics. Recently, their potential and appeal for different additive manufacturing techniques has been demonstrated. Insight into the usage of liquid crystals in 3D printing for fabrication at both micro‐ and centimeterscale is provided for those wanting to join this exciting, developing field.
... Triggering Ca 2+ sparks with 2P photolysis on a physiologically relevant time scale required the development of a new caged Ca 2+ compound with a large 2P absorption cross-section. We took advantage of knowledge gained from structure-activity relationships gained for 2P-induced fluorescence from extended pi-electron systems (Albota et al. 1998;Rumi et al. 2008), and applied it to Ca 2+ uncaging by making BIST-2EGTA (Agarwal et al. 2016). The core chromophore has a 2P cross-section in the 350-775 GM range, significantly larger than our previous Ca 2+ cages (range 0.01-0.6 ...
Key points
In cardiac myocytes, subcellular local calcium release signals, calcium sparks, are recruited to form each cellular calcium transient and activate the contractile machinery.
Abnormal timing of recovery of sparks after their termination may contribute to arrhythmias.
We developed a method to interrogate recovery of calcium spark trigger probabilities and their amplitude over time using two‐photon photolysis of a new ultra‐effective caged calcium compound.
The findings confirm the utility of the technique to define an elevated sensitivity of the calcium release mechanism in situ and to follow hastened recovery of spark trigger probabilities in a mouse model of an inherited cardiac arrhythmia, which was used for validation.
Analogous methods are likely to be applicable to investigate other microscopic subcellular signalling systems in a variety of cell types.
Abstract
In cardiac myocytes Ca²⁺‐induced Ca²⁺ release (CICR) from the sarcoplasmic reticulum (SR) through ryanodine receptors (RyRs) governs activation of contraction. Ca²⁺ release occurs via subcellular Ca²⁺ signalling events, Ca²⁺ sparks. Local recovery of Ca²⁺ release depends on both SR refilling and restoration of Ca²⁺ sensitivity of the RyRs. We used two‐photon (2P) photolysis of the ultra‐effective caged Ca²⁺ compound BIST‐2EGTA and laser‐scanning confocal Ca²⁺ imaging to probe refractoriness of local Ca²⁺ release in control conditions and in the presence of cAMP or low‐dose caffeine (to stimulate CICR) or cyclopiazonic acid (CPA; to slow SR refilling). Permeabilized cardiomyocytes were loaded with BIST‐2EGTA and rhod‐2. Pairs of short 2P photolytic pulses (1 ms, 810 nm) were applied with different intervals to test Ca²⁺ release amplitude recovery and trigger probability for the second spark in a pair. Photolytic and biological events were distinguished by classification with a self‐learning support vector machine (SVM) algorithm. In permeabilized myocytes data recorded in the presence of CPA showed a lower probability of triggering a second spark compared to control or cAMP conditions. Cardiomyocytes from a mouse model harbouring the arrhythmogenic RyRR420Q mutation were used for further validation and revealed a higher Ca²⁺ sensitivity of CICR. This new 2P approach provides composite information of Ca²⁺ release amplitude and trigger probability recovery reflecting both SR refilling and restoration of CICR and RyR Ca²⁺ sensitivity. It can be used to measure the kinetics of local CICR recovery, alterations of which may be related to premature heart beats and arrhythmias.
