A novel polyimide (PI) and imide compound emitting prominent reddish-orange fluorescence under excitation by UV light were prepared based on 3-hydroxypyromellitic dianhydride (PHDA), and their fluorescence properties were examined. The steady-state fluorescence spectrum of a PI film displayed an emission band at 590 nm with a very large Stokes shift (ν = 10 448 cm −1 ) via the excited-state intramolecular proton transfer (ESIPT), while the time-resolved fluorescence spectrum showed a rapid decay of the emission band of the enol form at around 400 nm within 15 ps. Transient absorption measurements showed an induced absorption and stimulated emission of the keto form with a time constant of ca. 3.0 ps, implying that ESIPT occurs on this time scale. Consequently, introduction of a hydroxy group into the pyromellitic moiety of PIs and imide compounds led to the long-wavelength ESIPT emission applicable to spectral converters having high thermal, mechanical, and environmental stabilities.

In the present research diamond-like carbon (DLC) films containing 4–29 at.% of silicon were deposited by reactive magnetron sputtering of carbon target. Study by X-ray photoelectron spectroscopy revealed the presence of Si–C bonds in the films. Nevertheless, a significant amount of Si–O–C and Si–Ox bonds was present too. The shape of the Raman scattering spectra of all studied diamond-like carbon containing silicon (DLC:Si) films was typical for diamond-like carbon. However, some peculiarities related to silicon doping were found. Studies on the dependence of DLC:Si of the optical transmittance spectra on the Si atomic concentration have shown that doping by silicon affects linear, as well as nonlinear, optical properties of the films. It is shown that the normalized reflectance of DLC:Si films decreased with the increased exciting light fluence. No clear relation between the normalized reflectance and photoexcited charge carrier relaxation time was found. It was suggested that that the normalized reflectance decrease with fluence can be related to nonlinear optical properties of the hydrogenated diamond-like carbon phase in DLC:Si film.

Noble metal nanoparticles patterned in ordered arrays can interact and generate hybrid plasmonic–photonic resonances called surface lattice resonances (SLRs). Dispersion curves help explain how the Bragg coupling conditions and radiation patterns create dipolar and quadrupolar SLRs, but they assume that the nanoparticles are static structures, which is inaccurate at ultrafast time scales. In this article, we examine how local surface plasmon resonances (LSPRs) supported by cubic Ag nanocrystals are modulated by ultrafast photophysical processes that generate optomechanical modes. We use transient absorbance spectroscopy measurements to demonstrate how the LSPRs of the nanoparticles modulate the SLR of the array over time. Two primary mechanical breathing modes of Ag nanocubes were identified in the data and input into electromagnetic models to examine how fluctuations in shape affect the dispersion diagram. Our observations demonstrate the impact of optomechanical processes on the photonic length scale, which should be considered in the design of SLR-based devices.

Excited state dynamics of trinary star-shaped dendritic compounds with triphenylamine arms and different cores were studied by means of time-resolved fluorescence and transient absorption. Under optical excitation, nonpolar C symmetry molecules form polar excited states localized on one of the molecular substituents. Conformational excited state stabilization of molecules with an electron-accepting core causes a formation of twisted internal charge transfer (TICT) states in polar solvents. A low transition dipole moment from TICT state to the ground state causes very weak fluorescence of those compounds and strong dependence on the solvent polarity. The compound formed from the triphenylamine central core and identical arms also experiences excited state twisting, however, weakly sensitive to the solvent polarity.

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