ملخص البحث :

The paper is focused on the study of the dynamic surface properties of mixed monolayers of porphyrin and arachidic acid with various mole fractions at the air–water interface. The choice of porphyrin solid thin film as an object of study is explained by its high potential application in the area of photovoltaics and medicine. The Langmuir monolayers of porphyrin and arachidic acid were formed under different conditions using the Langmuir-Blodgett technique. The increase of subphase temperature led to a decrease in the rigidity of the porphyrin monolayer and leads to accelerating the relaxation process of the monolayer. The chosen surface pressure (4, 5, 15 and 35 mN/m) affected the stability of the floating monolayer. The higher miscibility of the monolayers was obtained at the mole fraction of porphyrin = 0.333. The change in the phase of monolayers surface was reported on the basis of surface potential data. The morphology properties of the mixed systems transferred on silicon substrates by Schaeffer method are studied.

ملخص البحث :

The development of low-defect self-organizing thin film materials is one of the most important directions of modern optoelectronics. For this purpose, the formation and stability of quantum dots (QDs) floating monolayers on the composition (pure water or NiCl2 aqueous solutions) and temperature (19 and 25 °C) of subphase have been investigated. The studied quantum dots were CdSe/CdS/ZnS (core/shell/shell) stabilized by oleic acid. The data on π-A isotherms, hysteresis, and stability of QDs floating monolayers were analyzed. It was found that the monolayer formed on the pure water subphase is more stable. It was established that the increase of NiCl2 content in the aqueous subphase (from 1 to 5 mM) leads to the decrease of the gas phase region and the increase of the liquid and condensed phase regions on π-A isotherms. It was suggested that Ni2+ cation interacts with the carboxylic groups of free (unbounded to QDs) oleic acid molecules. As a result, the density of floating layer and the compression module values increased. The highest compression modulus values of QDs floating monolayers were found for the 5 mM NiCl2 containing subphase. On the basis of the studied floating layers, thin films were obtained on silicon substrates, and their surface was investigated by the AFM method. It was determined that the presence of NiCl2 in the aqueous subphase leads to an increase in the thicknesses and hydrophobicity of the prepared thin films. The obtained data can be used at the formation of multicomponent thin film nanomaterials containing quantum dots.

ملخص البحث :

The authors theoretically investigated absorbance spectra of the hypothetical 1D Cu clusters with 2–22 atoms and monoatomic thickness. In contrast to 3D isomers with interband transitions only (< 600 nm; intrinsic for any copper nanostructure), the 1D clusters possess strong absorbance bands within 650–1800 nm range depending on the cluster size (NIR bands). The band location in NIR range was explained by low binding number per copper atom that leads to weaker coupling of 4s electrons within the conduction band and reducing energy gap between vacant and occupied orbitals. The NIR bands are formed by HOMO → LUMO transitions and their large intensity was explained by highly hybridized sp character of HOMO and LUMO and by the low contribution of 3d electrons (< 10%). The analysis of the number of electrons involved to the formation of NIR bands demonstrates their prominent plasmonic (collective) character. For example, the NIR band of the cluster with 20 atoms (1636 nm) is formed by excitation of 5 electrons. In contrast, 0.35 and 0.44 electrons were involved to the formation of all absorbance bands within visible–NIR range (400–1000 nm) for spherical and tetrahedral 3D isomers, respectively. The results are in qualitative agreement with experimental results for copper nanorods and nanowires which also possess strong bands in the red–NIR range (> 600 nm) compared to the nanoparticles with spherical geometry. Additionally, the large clusters (16–22 atoms) possess multiple bands in NIR range that is also in agreement with the experiment.