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- Analysis of quantum coherence in biologyPublication . Khmelinskii, Igor; Makarov, Vladimir, IWe reviewed the tools of quantum physics used in modeling of quantum coherence (QC) effects in different systems, including biological systems, which behave as quantum objects in some of their degrees of freedom. In particular, we considered the usage of the effective Hamiltonian (EH), Green's function (GF) and density matrix (DM) methods in the analysis of QC, focusing on QC in biological systems. We discussed the two main mechanisms of loss of quantum state coherence: (i) dephasing of the originally prepared coherent wave package and (ii) population relaxation in the same wave package. Dephasing does not affect the quantum state population, e.g. as in spin-spin relaxation, where dephasing is described by the tau(2) relaxation time. On the other hand, the state population relaxation of the spin wavepackage is attributed to spin-lattice relaxation and is described by the tau(1) relaxation time. Presently we discussed EH and GF formalisms in terms of the complex energy, dependent on intra- and intersystem interactions that induce state population relaxation. We provided a detailed analysis of these approaches for the exciton relaxation dynamics in a glycine polypeptide chain. The same phenomena were described in the DM formalism using the relaxation matrix. We discussed QC in different biological systems, showing that QC is conserved when the interactions of the coherent wavepackage with other degrees of freedom are weak, as otherwise population relaxation causes loss of QC. We believe that our results will be useful for the researchers in the area of quantum biology.
- Superluminescence and macroscopic exciton propagation in freestanding ZnO thin filmsPublication . Khmelinskii, Igor; Makarov, Vladimir, IRecently we have reported properties of ZnO semiconductor films attached to CaF2 substrate. Presently we characterized absorption, emission and superluminescence of freestanding ZnO films, comparing these to the attached films with the same thickness values. The absorption spectra of the freestanding films had resolved bands, with the band density increasing with the nanofilm thickness. Additionally, the spectral transitions in these films were blue-shifted as compared to attached films. The absorption and emission spectra of freestanding films were resolved better than those of attached films, with the difference traceable to the surface roughness of the substrate used for deposition. We also explored exciton dynamics and propagation over macroscopic distances in freestanding films. The excitons lived longer and propagated further in freestanding films as compared to attached films. The superluminescence yield in freestanding 9.3 nm film of 0.43 +/- 0.05 was significantly larger than 0.17 +/- 0.03 in an equivalent attached film. We provided a detailed analysis of the results obtained. The reported data are unique, demonstrating significant difference in the optical properties of attached and freestanding ZnO thin films. Freestanding ZnO films are promising for optoelectmnic applications.
- Electric field modulation of light energy transmission along intermediate filaments isolated from porcine retinaPublication . Khmelinskii, Igor; Makarov, VladimirPresently we report new experimental method for simultaneous measurements of electrical and optical properties in vitro for the intermediate filaments (IFs) in the axial direction, complemented by the method to measure light intensity absorbed by IFs aligned within the capillary matrix. These methods were used to simultaneously measure spectroscopic and electric properties of Müller cell (MC) IFs extracted from porcine retina. Using light at 546 nm, we found that these IFs are excellent conductors of light energy, with the efficiency of ca. 0.5 without external voltage field and 0.7 in presence of an external voltage of 0.1 V, and good conductors of electric current, with the conductivity value close to that of typical metals. We also found that the efficiency of light energy transmission along IFs depends on the external applied voltage. The presently reported optical and electrical properties of MC IFs may endow vertebrate eyes with high-contrast vision, providing evidence in favor of a mechanism regulating the amount of light energy transmitted via MC IFs between inner and outer limiting membrane levels in vertebrate retina.