With the rapid development of modern information technology, massive amounts of data are stored that require an information security. Here, we introduce a spiropyran doped polymer dispersed cholesteric liquid crystal film based rewritable medium that can produce high quality visual two-dimensional barcodes for anti-counterfeiting, authentication and security purposes. The prepared film exhibits excellent photochromic properties, improved photosensitivity, high spatial resolution, and numerous rapid write/erase capabilities. Such rewritable material can be efficiently printed over 70 cycles without compromising its readability. Furthermore, the fabricated film is mechanically resistant to small stresses and, hence, it can be directly handled.

The real-time thermal imaging systems, which allow the rapid conversion, acquisition, and manipulation of obtained optical information, are the emerging technologies that offer a variety of imaging applications. Here, we present a novel type of thermal imaging device, based on the thermo-optical properties of liquid crystal blue phases. Herewith, the novelty lies in the use of a weak first-order phase transition between the blue phases controlled by external thermal fields. In turn, the stimulated interconversions of the selective reflections between the blue phases enable the visualization of the two-dimensional spatial distribution of the thermal fields. The real-time room temperature operation capabilities of the proposed thermal imaging device may enable applications in areas such as medicine, astronomy, security, surveillance, people tracking, aerospace monitoring, and artworks inspection. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

The gold nanoparticle (GNP) aggregation growth induced by deoxyribonucleic acid (DNA) is studied by laser scanning confocal and environmental scanning electron microscopies. As in the investigated case the direct light scattering analysis is not suitable, we observe the behavior of the fluorescence produced by a dye and we detect the aggregation by the shift and the broadening of the fluorescence peak. Results of laser scanning confocal microscopy images and the fluorescence emission spectra from lambda scan mode suggest, in fact, that the intruding of the hydrophobic moiety of the probe within the cationic surfactants bilayer film coating GNPs results in a Förster resonance energy transfer. The environmental scanning electron microscopy images show that DNA molecules act as template to assemble GNPs into three-dimensional structures which are reminiscent of the DNA helix. This study is useful to design better nanobiotechnological devices using GNPs and DNA.

We have manufactured and investigated a novel phase retarder based on a rare and less studied liquid crystal phase, such as the Crystal Smectic G-phase prepared by mixing two certified nematic mixtures. The phase retarder is transparent in the visible and near-infrared parts of the optical spectrum. The temperature stability over a wide temperature range, high birefringence, and high strength, allow the production of various types of phase retarders that can be used in optics, optical chemical analysis,and polarimetry.