Particularities of photonic and structural transformations in the polystyrene film during pulsed infrared laser irradiation

Two new kinds of the structural in-homogeneities in the polystyrene films were created by the irradiation of the film with nanosecond pulses of the infrared laser with 1064 nm wavelength. At the beginning of the irradiation dark micro-inclusions having unusual close to rectangular geometries appeared. After about 30 seconds of the irradiation one more kind structural distortions appeared having the geometries of the systems of the concentric micro-rings. Simultaneously with the creation of these concentric micro-rings the film started to emit bright blue luminescence all over its area and significant focusing of the laser beam during its propagation through the film was observed resulting in the generation of the bright white flashes at the screen installed behind the film. The creation of the dark rectangular spots as well as of the concentric micro-rings are ascribed to the non-linear interactions between the laser radiation and the structural distortions produced in the film due to photo-thermal processes excited in the film.

Polarization Reversal Characteristics in Capacitors with a Metal/Insulator/Ferroelectric/Metal Structure

A metal/insulator/ferroelectric/metal structure was fabricated using a covering of approximately 10 nm thick of an insulating polystyrene film on a ferroelectric poly(vinylidene fluoride-trifluoroethylene) film. To fabricate several samples, the thickness of the ferroelectric film was held constant while the thickness of the insulating film was varied from 8 to 24 nm. The polarization– voltage relationships were measured to extract the main parameters, in this case the remanent polarization, depolarization, coercive voltage and biased voltage values. As the insulating film becomes thicker, the remanent polarization and coercive voltage values tended to increase. On the other hand, depolarization and biased voltage values decreased. By analyzing the above mentioned parameters, a certain optimum insulator thickness could be predicted. This work shows that metal/insulator/ferroelectric/metal devices are more useful than metal/ferroelectric/metal capacitors.

Dual Amplified Spontaneous Emission and Lasing from Nanographene Films

Chemically synthesized zigzag-edged nanographenes (NG) have recently demonstrated great success as the active laser units in solution-processed organic distributed feedback (DFB) lasers. Here, we report the first observation of dual amplified spontaneous emission (ASE) from a large-size NG derivative (with 12 benzenoid rings) dispersed in a polystyrene film. ASE is observed simultaneously at the 685 and 739 nm wavelengths, which correspond to different transitions of the photoluminescence spectrum. Ultrafast pump-probe spectroscopy has been used to ascertain the underlying photophysical processes taking place in the films. DFB lasers, based on these materials and top-layer nanostructured polymeric resonators (i.e., one or two-dimensional surface relief gratings), have been fabricated and characterized. Lasers emitting close to either one of the two possible ASE wavelengths, or simultaneously at both of them, have been prepared by proper selection of the resonator parameters.

Microbial Sensor for Determination of Amoxicillin Activity

A sensor based on the electrodynamic microwave resonator has been developed to determine the antibacterial activity of antibiotics using amoxicillin as an example. Microbial cells immobilized on the polystyrene film surface were used as a sensitive element of the sensor. The optimal conditions for the immobilization of Escherichia coli Xl-1 microbial cells on the surface of a thin polystyrene film modified in high-frequency argon discharge plasma and deposited on a lithium niobate plate were determined. The effect of amoxicillin on immobilized microbial cells was studied using the developed sensor. It has been established that the increase in con- centration of amoxicillin from 5 to 50 μg/ml leads to a significant change in the reflection coefficient S11 at the resonance frequency from the lithium niobate plate in the range of -12.6 dB — -15.1 dB. It has been shown that the developed sensor allows determining the antibacterial activity of drugs in the studied concentration range with an analysis time of 15 min.