M. Wojdyła

Influence of different peripheral substituents on the nonlinear optical properties of cobalt phthalocyanine core

In this article, we show how the substituting different peripheral substituents around the cobalt phthalocyanine core correlate with nonlinear optical properties. We present the results on nonlinear optical properties of solution of cobalt phthalocyanine (CoPc), cobalt phthalocyanine with DNA-CTMA surfactant complex (CoPc-DNA-CTMA), and cobalt phthalocyanine with liquid crystal (CoPc-LC) measured by degenerate four-wave mixing (DFWM) method at the 532 nm wavelength region. We found that the values of third-order nonlinear optical susceptibility (χ⟨3⟩) of CoPc-LC and CoPc-DNA-CTMA increase in comparison with the value of the third-order nonlinear optical susceptibilities of CoPc. We supposed that this is caused by increase of the charge-transfer effects and of the dipole moments of the molecule with the increase of the chain length.

Stationary and modulated absorption spectroscopy of copper phthalocyanine (CuPc) layers grown on transparent substrate

Copper phthalocyanine thin films grown on glass and quartz substrates by the thermal evaporation method were investigated using stationary and modulated photoabsorption as well as photoreflectance spectroscopy. The stationary and modulated studies at room temperature were performed in the wavelength range 200–1200 nm and 400–1200 nm, respectively. The absorption coefficient of investigated layers was determined directly from the transmission spectrum and fitted in terms of the mixed Lorentz–Lorenz model, which assumed five oscillator components. Sensitive modulated spectroscopy, which enabled us to emphasize weakly visible transitions in the Q-band spectral region, was also performed to estimate the electronic structure of metallophthalocyanine layers. The complex nature of excited states of the metallophthalocyanine layers gave us abundant modulated spectra. These spectra were fitted using the third derivative line shape given by the Aspnes formula. Modulated photoabsorption and photoreflectance spectra for CuPc thin layers are presented for the first time in this paper.

Absorption spectroscopy of single red blood cells in the presence of mechanical deformations induced by optical traps

Abstract. The electronic properties of single human red blood cells under mechanical deformations were investigated using a combination of dual beam optical tweezers and UV-vis absorption spectroscopy. The mechanical deformations were induced by two near-infrared optical traps with different trapping powers and trap configurations. The deformations were applied in two ways: locally, due to the mechanical forces around the traps, and by stretching the cell by moving the traps in opposite directions. In the presence of local deformations, the single cell undergoes a transition from an oxygenated state to a partially deoxygenated state. This process was found to be reversible and strongly power-dependent. Stretching the cell caused an opposite effect, indicating that the electronic response of the whole cell is dominated by the local interaction with the trapping beams. Results are discussed considering light-induced local heating, the Stark effect, and biochemical alterations due to mechanical forces, and are compared with reports of previous Raman spectroscopy studies. The information gained by the analysis of a single red blood cell’s electronic response facilitates the understanding of fundamental physiological processes and sheds further light on the cell’s mechanochemistry. This information may offer new opportunities for the diagnosis and treatment of blood diseases.

Dependence of the Third Order Nonlinear Optical Susceptibility on Concentration and Peripheral Substituent of Metallophthalocyanines

Third order nonlinear optical properties of metallophthalocyanines (MPcs) were investigated using degenerate four wave mixing (DFWM) method. We also studied how the replacement of peripheral substituent around the MPcs cores correlates with nonlinear optical properties. Therefore third order nonlinear optical susceptibilities (χ<3>) of MPcs with liquid crystal (MPcs-LC) were investigated. We found that the χ<3> values of MPcs-LC increase in comparison with the corresponding values of MPcs. We supposed that this is caused by the increase of the charge transfer effects and change of the dipole moments of the molecule with the increase of molecules dimension.

Optical Properties of Vacuum Sublimed Cobalt Phthalocyanine (CoPc) Thin Layers

In this article the temperature dependence of absorption spectra of vacuum sublimed cobalt phthalocyanine (CoPc) thin layer is presented. For comparison the optical properties of CoPc solution were also investigated. Absorption measurements revealed strong intermolecular interaction in the solid form as well as the presence of intramolecular charge transfer excitation below the B exciton band. Spectral distribution of complex refractive index (n) and extinction coefficient (k) as well as thickness of the layer were found basing on reflection and transmission measurements by minimization appropriately defined error function. Corresponding values of dielectric constants were also calculated.

Third-order nonlinear optical properties of CuPc: influence of thickness and concentration

The concentration dependence of third order nonlinear optical susceptibility ( χ<3> ) of copper phthalocyanine (CuPc) dissolved in tetrahydrofuran (THF) using the degenerate four wave mixing (DFWM) method at 532 nm was investigated. We present the linear dependence of the third order nonlinear optical susceptibility ( χ<3> ) as a function of different concentration for CuPc dissolved in THF. We also calculated the second order hyperpolarizability ( γ) of CuPc solutions. Third harmonic generation (THG) measurements at the 1064 nm performed on CuPc thin films are also presented. We found that the χ<3>DFWM values are larger than the χ<3>THG ones. This variation observed in χ<3> values, occurs probably due to the different resonance contributions in solution and solid state of CuPc. We show that in the case of DFWM measurements the one and two-photon resonant contributions at the Q and C-band increase χ<3>DFWM value of CuPc. In THG measurements, the three-photon resonance contribution at the Soret band gives rise to higher χ<3>THG value.

Force and Raman spectroscopy of single red blood cell

Viscoelastic and spectroscopic properties of single RBC are probed using dual beam optical tweezers and Raman techniques, respectively. Complex response function of cell was measured by means of one and two particles passive microrheology at different stretching states yielding local and overall mechanical properties of exactly the same human erythrocyte. The frequency dependent response function (measured up to 10 kHz) was corrected for the presence of the traps and spectral distribution of complex stiffness over controlled range of cell deformation is calculated and discussed. The presence of non-thermal sources of membrane motions is also explored based on comparison of passive and active microrheology experiments. In order to get insight into structural changes of RBC due to deformation, Raman spectra of single cell were recorded. Evolution of Raman bands with cell deformation was analyzed using sensitive 2D correlation method. The combination of force and Raman spectroscopy is promising and potentially very powerful method to establish essential linkages between structure, mechanical properties and functions of living cells.

Load bearing studies of single DNA molecules and red blood cells using optical tweezers and Raman spectroscopy

Living cells and single molecules as DNA experiences numerous mechanical events, necessitating single molecule force spectroscopy techniques to provide insight into cellular mechanics as a whole system. This paper shows results on Raman spectroscopy of a single red blood cell which is gradually stretched using optically trapped beads attached to the cell. The applied force is intended to simulate step-by-step deformation experienced by cells in normal conditions (induced by blood flow) as they squeeze through microvasculature. To further improve the sensitivity of the experiments and facilitate their interpretation, 2D correlation and principal component analysis techniques were applied. The purpose of this work is to help unravel direct relationship between mechanical deformation of RBC and chemical changes occurring in the cell structure on molecular level. We also obtained Raman spectra from single DNA molecules in their natural aqueous environment as a first step to establish a direct relationship between DNAs extension and structure in the low force, entropic regime.

The Photoluminescence Properties of Vinylcarbazole – Vinylimidazole Copolymer Thin Films

In our work we obtained the white light emitting material by copolymerization of vinylcarbazole with vinylimidazole. The ratio of vinylcarbazole to vinylimidazole comers in the obtained copolymer (PVKI) was 4:3. This article is concerned with the photoluminescence (PL) study of PVKI thin films deposited on the glass substrate by the dip-coating method. The obtained results were compared with the photoluminescence of thin films of poly (N-vinylcarbazole) (PVK) and poly (N-vinylimidazole) (PVI) deposited by the same technique. All PL spectra have been measured under steady state excitation (λ = 325 nm) in the temperature range from 13 K to 325 K.

The temperature dependence of photoluminescence and absorption spectra of MPc (M = Zn, Co, Mg, Cu) thin films

In this paper, photoluminescence (PL), transmittance (T) and absorption (A) measurements have been performed for the first time on metallophthalocyanines (MPc; M = Zn, Co, Mg, Cu) thin layers grown by quasi molecular beam evaporation on quartz substrates. Investigated films of ZnPc and MgPc show PL emission from the violet to near-IR region in the wide temperature range 13 K-320 K. While the two others show a rather weak emission. Measurements have been carried out in the 350-1150 nm spectral range. The photoluminescence spectra exhibit seven transitions. Some bands have been appeared only at certain temperature range. Below and above this temperature range, these bands have been disappeared. The changes of intensity, band position and broadening versus temperature have been investigated. A multi level model has been proposed to explain the photophysical processes and temperature dependence of PL spectra.