No abstract

The long-range orientational order of three members of 4-n-pentylphenylthio-4′-n-alkoxybenzoate $$ (\bar nS5) $$ series doped with a dichroic dye was studied by means of electronic absorption and fluorescence measurements. The order parameters <P2> and <P4> as well as the orientational distribution function were determined on the basis of absorption and emission spectra of linearly polarized light recorded as a function of temperature in the nematic, smectic A, and smectic C phases. An influence of the dye molecular structure on the orientational order of the dye/liquid crystal mixture was observed. Moreover, the dependence of the order parameter values on the length of the alkoxy chain in liquid crystal molecules was found. It was shown that the order parameter <P4>, obtained from fluorescence measurements, can be helpful in recognizing the second-order or weakly first-order transitions between various liquid crystalline phases.

The long-range orientational order of 4-n-pentylphenylthio-4 0 -n-decyloxybenzoate (10S5Þ doped with a dichroic dye was studied as a function of temperature in the nematic, smectic A, smectic C and smectic J phases by means of two optical spectroscopy methods: dichroism of absorption in the visible spectral region and fluorescence depolarization. On the basis of absorption and fluorescence spectra the order parameters

and

as well as the orientational distribution function were determined. The discontinuous change of both

and

parameters at the smectic A -nematic phase transition for dye= 10S5 mixtures was observed, in an agreement with the microscopic theory proposed by McMillan. An influence of the dye molecular structure on the orientational order of the dye= 10S5 mixture was observed. The correlation between the order parameter values and the shift of the phase transitions temperatures due to the dye addition was confirmed.

No abstract

The II-VI nanocrystallites (NCs) are well known as a great fluorescent probe, but one of the main problem is a toxic effect. Covering a semiconductor NCs by some materials or chemicals can reduce it, but change optical properties and functional characteristics of NCs. The potential ability of the CdTe NCs passivated by human serum albumin (HSA) to cancer cells bioimaging is examined. Performed research explored the interaction between the CdTe NCs and HSA, and fluorescence imaging efficiency of the NC-HSA bionanocomplex in comparison with the uncovered NCs. The secondary structure of the HSA is similar to the native form, which suggests a biocompatibility of the prepared bionanocomplex. The CdTe NCs located in osteosarcoma cancer cells show a high luminescence intensity. The light emission of the CdTe NCs connected with albumin is less than the pure NCs, but it is still satisfactory, and additionally have high resistance to photo-bleaching. It suggests that the CdTe NC-HSA bionanocomplex can be used as a fluorescent probe for cell labelling, tracking and other bioimaging applications.