Cationic copolymers based on 2-(N,
-dimethylamino)ethyl methacrylate and polyethylene glycol monomethyl ether (pDMAEMA-co-PEO) with different molecular weights have been synthesized. Their ...physicochemical properties were studied by NMR spectroscopy, sedimentation, and potentiometric titration. According to the data of potentiometric titration for the synthesized pegylated cationic copolymers, the apparent dissociation constants were determined in the pH range from 4.5 to 8.5. The physicochemical properties of interpolyelectrolyte complexes of these polycations with circular DNA (IPEC DNA) were also studied by dynamic light scattering, electrophoretic mobility, and TEM methods. It has been established that the diameter and electrokinetic potential (ζ-potential) of interpolyelectrolyte complexes can be varied over a wide range (from 200 nm to 1.5 μm and from -25 mV to +30 mV) by changing the ratio of oppositely charged ionizable groups in pegylated cationic copolymers and DNA, as well as by regulating medium pH. The resistance of the IPEC DNA/polycation complex to the action of nucleases was studied by electrophoresis in agarose gel; the cytotoxic effect of the polymers in vitro, and the efficiency of penetration (transfection) of IPEC DNA with PDMAEMA-co-PEO-polycations into eukaryotic cells of a cell line derived from human embryonic kidneys HEK 293 in vitro.
Here, we report the synthesis, characterization, and properties of novel nanohybrids formed by self-assembly of negatively charged MoS2 nanoplates and positively charged iron oxide nanoparticles ...(NPs) of two different sizes, 5.1 and 11.6 nm. Iron oxide NPs were functionalized with an amphiphilic random copolymer, quaternized poly(2-(dimethylamino)ethyl metacrylate-co-stearyl metacrylate), synthesized for the first time using atom transfer radical polymerization. The influence of the MoS2 fraction and the iron oxide NP size on the structure of the nanohybrids has been studied. Surprisingly, larger NPs retained a larger fraction of the copolymer, thus requiring more MoS2 nanoplates for charge compensation. The nanohybrid based on 11.6 nm NPs was studied in oxidation of sulfide ions. This reaction could be used for removing the dangerous pollutant from wastewater and in the production of hydrogen from water using solar energy. We demonstrated a higher catalytic activity of the NP/MoS2 nanohybrid than that of merely dispersed MoS2 in catalytic oxidation of sulfide ions and facile magnetic recovery of the catalyst after the reaction.
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The effect of doping of the ZnxCd1−xS (x=0.37–0.50) alloy nanocrystals with Mn2+ ions on the rate and apparent quantum yield of the photocatalytic H2 evolution catalyzed by this alloy ...has been investigated. It has been found that the ZnS shell significantly increases the lifetime of the Mn2+ excited state, which leads to the generation of ‘hot’ electrons and the two-photon photocatalytic reduction of hydrogen ions. An analysis of the characteristics of nanocrystals without a ZnS shell with similar excitation energies of the edge exciton revealed that the efficiency of the alloy doped with Mn2+ ions is 1.2–1.3 times higher due to an increase in the lifetime of photoinduced electron–hole pairs.
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Polymer-coated CdS nanocrystals were doped with nickel in different ways: (1) by thermal decomposition of Ni(acac)2, (2) via photodeposition from NiCl2 aqueous solution, and (3) using ...nickel bis(2-aminobenzenethiolate) complex in the polymer shell. The modification of nanocrystals with nickel resulted in threefold increase in the rate of hydrogen evolution in the aqueous Na2S/Na2SO3 solution (pathways 1, 2) and 15- to 400-fold (pathways 3 and 2, respectively) increase in the aqueous solutions containing ascorbic acid.
Synthesis of polystyrene-block-polybutadiene (PS-b-PB) and polystyrene-block-polyisobutylene (PS-b-PIB) micelles filled with MoS x nanoparticles was carried out in a one-pot procedure in heptane ...using complexation with Mo(CO)6 followed by interaction with H2S. The structure and composition of Mo carbonyl complexes and MoS x -containing micelles were studied using FTIR, static light scattering, turbidimetry, and transmission electron microscopy. By varying the reaction atmosphere (argon or CO) during interaction with Mo(CO)6, the location of MoS x species obtained after sulfiding was tailored. Carrying out complexation with PS-b-PB in CO, which is also a reaction product, prevents complexation in the PS micelle core, thus providing location of Mo species only in the PB corona. Antifrictional tests show that this location leads to better tribological performance: lower friction coefficient or higher critical load (at which the friction coefficient is measured). When MoS x species are located in the PS core (complexation with Mo(CO)6 was carried out in argon atmosphere), low density of the micelles in the case of PS-b-PIB block copolymer with a short PS block provides much better antifrictional performance than those with the dense PS-b-PB micelles.
The novel Pt- and Rh-containing polymers based on polystyrene-polybutadiene block copolymers were studied in hydrosilylation of three systems of reagents: styrene/triethylsilane, ...1-hexene/dimethylchlorosilane, and cyclohexanone/triethylsilane. All polymers containing Pt and Rh complexes were found to display some catalytic effect whose effectiveness for the same system of reagents is dependent on the nature of the polymeric ligand. On the other hand, the reagent nature influences even more strongly the catalytic properties of polymers. No side products of hydrosilylation was observed with Rh-containing polymer catalysts in cyclohexanone/triethylsilane system.
The alloys of Zn
0.34
Cd
0.66
S QDs show a high photocatalytic activity when mediating the hydrogen production from water with a reaction rate of 233 ± 9 µmol h
−1
g
−1
. The reaction is carried out ...in the presence of ascorbic acid as sacrificial electron donor. The alloy Zn
0.34
Cd
0.66
S/ZnS QDs with a ZnS shell showed a yield about seven times lower for the same process compared to the ZnCdS/ZnS alloy. The dynamics of the exciton reactions in the initial stages of the reaction mediated by these QDs was studied by femtosecond laser spectroscopy. Femtosecond transient absorption spectra is reported in a detailed and comprehensive way describing dynamics of the absorption peak A1 near the bleach band of edge exciton B1. This A1 absorption peak is attributed to the Stark shift due to exciton–exciton interactions due to the trapping of a hole or an electron on the QDs surface. In shell-less ZnCdSQDs, the A1 peak presented two kinetic components: the damping of the A1 peak amplitude due to the relaxation of “hot” excitons and the concomitant growth of the A1 peak at later delay times. We suggest that this was due to due to the carrier capture charge by surface traps leading to electric field redistribution in the QDs. The relaxation/decay of “hot” electrons in alloys of ZnCdS and ZnCdS/ZnS QDs occur with characteristic times of
τ
ZnCdS
= 153 fs for ZnCdS and
τ
ZnCdS/ZnS
= 193 fs.
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•The Mn2+ doped ZnxCd1-xS and ZnxCd1-xS/ZnS quantum dots were synthesized.•The quantum yield photoluminescence of Mn2+ doped QDs reached 60%•Spectral signal derivatives allowed to ...localize Mn2+ in the prepared QDs.•The distribution of Mn2+ ions in QDs depends on the synthesis method.
The synthesis methods (one- or two-pot) of stable Mn2+ doped ZnxCd1-xS and ZnxCd1-xS/ZnS quantum dots are reported in this study with a quantum yield (QY) of ∼ 60% in anhydrous and ∼ 30% in aqueous media for Mn2+ photoluminescence (PL). Mn2+-localization in the prepared QDs was characterized by electron paramagnetic resonance (EPR). Structural parameters were established by X-ray diffraction (XRD). Femtosecond transient absorption spectroscopy, time-gated luminescence measurements allowed to elucidate the relaxation dynamics of exciton, traps and 4T1 excited Mn2+. High-order derivative spectral analyses of the photoluminescence (PL) bands of Mn2+ accompanied with Gauss peaks decomposition have been employed. This analysis revealed narrow peaks in the spectral range from green (∼537 nm) to far-red (∼655 nm). These PL peaks can be associated with different locations of Mn2+ in QDs that are characterized by different strengths of the crystal field around Mn2+. Dopant localization sites and relaxation processes control the quantum yield of Mn2+, providing higher photocatalytic activity, pronounced electroluminescence, and higher sensitivity.
