Search

We report on the structural, thermal, linear, and ultrafast third-order nonlinear optical (NLO) properties of two novel anthracene chalcones: (2E)-1-(anthracen-9-yl)-3-(5-methylthiophen-2-yl)prop-2-en-1-one (5ML2SANC) and (2E)-1-(9-anthryl)-3-(2,4,5-trimethoxyphenyl)prop-2-en-1-one (245TMANC). The chalcones were synthesized by Claisen-Schmidt condensation reaction, and the single crystals were grown by the solvent evaporation method. The molecular structure was confirmed by FTIR and NMR spectroscopy, while the crystal structure was determined using the single crystal XRD. Both crystals belong to centrosymmetric monoclinic crystal system with space group P2 1 /n. The Hirshfeld surface was analyzed to understand intermolecular interactions, and the band structures - including HOMO-LUMO levels, excited state energies, GCRDs and MEPs-were studied using DFT. The ultrafast third-order NLO properties were investigated by Z-scan and degenerate four-wave mixing (DFWM) techniques using Ti: Sapphire amplifier laser delivering ∼50 fs pulses at 800 nm (1 kHz, ∼4 mJ, 2 W). Two-photon absorption, positive nonlinear refraction, optical limiting and optical switching behaviors were observed by Z-scan measurements. The time-resolved DFWM show that the decay time of 5ML2SANC is ∼127 fs, while for 245TMANC it is ∼142 fs. The second hyperpolarizability (γ) measured by Z-scan, DFWM and the estimations from the DFT theory are found to be in good agreement (∼10 -34  esu). The ultrafast optical response, significant NLO properties and thermal stability of the synthesized chalcones demonstrate their potential suitability in optical limiting and switching applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Alkali borate glasses activated with trivalent europium ions and rooted with gold (Au) nanoparticles (NPs) were synthesised through a melt quenching process involving a selective thermochemical reduction and their applicability as photonic materials was assessed in detail. Non-linear optical (NLO) measurements were performed using a Z-scan approach in the wavelength range of 700-1000 nm. The open aperture Z-scan signatures for the Eu 3+ -containing glasses embedded with and without the Au NPs established a reverse saturable absorption (RSA) at all of the studied wavelengths ascribed to the two-photon absorption (2PA). Surprisingly, the nonlinear optical absorption switched to a saturable absorption (SA) with an increase in the concentration of AuCl 3 . With the incorporation of the Au NPs, the UV excited photoluminescence (PL) intensity of the Eu 3+ -doped glasses increased first as a consequence of the local field enhancement by the Au NPs, and subsequently decreased at a higher concentration of AuCl 3 due to the reverse energy transfer from the Eu 3+ ion to the Au 0 NPs. The electronic polarization effect of the host glass enhanced the 5 D 0 → 7 F 4 transition intensity on the incorporation of the gold NPs owing to the gold NP-embedded glasses showing a deep-red emission. The NLO and PL studies suggested that the investigated glasses containing a 0.01 mol% of AuCl 3 is practically appropriate for photonic applications.

A novel zinc phthalocyanine derivative [2(3), 9(10), 16(17), 23(24) tetrakis-4-((4-(1,4,5-triphenyl-1 H -imidazol-2-yl)phenyl)ethynyl)phthalocyanine zinc(ii) (PBIPC)] was synthesized by incorporating a triphenyl imidazole moiety at its peripheral positions. The detailed mechanisms of absorption, emission, electrochemical, nonlinear optical (NLO) and photophysical (excited state dynamics) properties of PBIPC were explored. The absorption and emission properties of the compound were studied in different solvents. The incorporation of a triphenyl imidazole moiety at the peripheral position of the zinc phthalocyanine slightly broadened the Soret band. The emission studies revealed fluorescence quantum yields to be in the range of 0.11-0.22. The time-resolved fluorescence data established the radiative lifetimes to be in the nanosecond range. The oxidation and reduction processes were found to be ring centered, which were studied using the cyclic voltammetry (CV) technique. The energy optimized structures and HOMO-LUMO levels were calculated using DFT, TD-DFT analysis and were employed by means of hybrid functional theory (B3LYP) at 6-31G (d,p) basis set in the Gaussian 09 package. Two-photon absorption was observed in the NLO studies performed in the visible wavelength range of 600-800 nm while the nonlinear absorption was dominated by three- and four-photon absorption processes in the NIR wavelength range (1.0-1.5 μm). The molecule exhibited self-focusing behavior for all the wavelengths. Finally, the excited state dynamics of the title molecule PBIPC were investigated using femtosecond transient absorption spectroscopy and the results obtained were understood on the basis of a simple three kinetic model, for excitation wavelengths of 400 nm (Soret band) and 650 nm (Q-band). Both the spectra demonstrated a broad positive transient absorption (TA) data which overlapped with the ground state bleach (GSB), which in turn displayed a red shift over a delay of ∼2 ns. The lifetimes revealed a possibility of intersystem crossing ( τ > 1 ns) owing to the triplet state transition., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Lead halide perovskite nanocrystals (NCs) apart from their overwhelming optoelectronic applications have recently demonstrated promising nonlinear optical (NLO) properties such as strong two-photon absorption cross-sections (∼105 GM), two-photon fluorescence, and saturable absorption even at very high peak intensity. Zero-dimensional perovskite-related materials (0-D PRMs) are a new class of materials offering a high exciton binding energy (Eg ≥ 180 meV) with a strong photoluminescence (PL) quantum yield in few cases. Herein, we report the broadband third-order NLO properties of phase pure Cs4PbBr6 0-D PRM achieved using the Z-scan and degenerate four-wave mixing techniques in the femtosecond regime. Considering the growing content of the fluorescent and non-fluorescent forms of this material, we have performed our studies on both of them. These perovskite NCs exhibited strong multi-photon absorption properties in the near-infrared region with two-photon absorption (2PA) (cross-section, σ2 = 10-43-10-44 cm4 s equivalent to ∼106 GM) in the 500-800 nm region, three-photon absorption (3PA) (cross-section, σ3 ∼10-73 cm6 s2) in the 900-1200 nm region and four-photon absorption (4PA) (cross-section, σ4 ∼10-100 cm8 s3) in the 1300-1500 nm spectral region. These multi-photon absorption processes are explained using a simple band diagram. The measured NLO coefficients and cross-sections are fairly large when compared to some of the earlier reports on perovskite-based NCs. Cs4PbBr6 0-D PRM also demonstrated a large third-order NLO susceptibility χ(3) (∼10-7 esu), which can be attributed to the strong quantum confinement arising from spatially isolated, exciton containing individual [PbBr6]4- octahedron. These results clearly suggest the potential of 0D-PRMs in applications such as photonics and ultrafast all-optical switching devices.

Two new free-base β-octa and hexaalkyl naphthobipyrrole-derived sapphyrins are reported along with various salts thereof. One of them has substituents at all of its β positions, whereas the pyrrole unit opposite to the bipyrrolic moiety is unsubstituted in the other. The effect of bipyrrole fusion on the structure of sapphyrins was explored. Interestingly, an unprecedented sandwiched supramolecular aqua-bridged free-base sapphyrin dimer was also characterized in the solid state. Further, the effect of anions on the third-order nonlinear optical properties of these sapphyrins were explored in the salt form, along with their detailed excited-state dynamics by both degenerate and nondegenerate pump-probe studies., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)