The interaction of gold nanoparticles (NPs) and semiconductor alloyed CdZnSe/ZnS quantum dots (QDs) in colloidal solutions is studied. It is shown that the photoluminescence intensity of QDs in a ...mixture decreases compared to that in the initial QD solution, which is caused by resonance nonradiative energy transfer from QDs to Au NPs in spontaneously formed aggregates. To control the formation of pairs of interacting QDs and Au NPs, we proposed have a method for creating QD–Au NP complexes bound by special molecules—ligands. It is shown that the morphology and optical properties of the samples obtained depend on the method of their preparation, in particular, on the chemical environment of QDs. It is found that the complexes form in the case of addition of hydrophilic Au NPs to hydrophobic QDs and that this almost does not change the optical properties of the latter compared to those of quasi-isolated QDs in colloidal solution.
Understanding the different processes in modern multicomponent metamaterials is a crucial task for their development. This includes the investigation of superstructures that can be formed by ...nanoparticle self-assembly. Here we present a destabilization-based synthetic protocol for the preparation of porous superstructures with flower, sphere, and spike-like shapes. This approach is universal for nanoparticles of various natures and compositions. We have prepared superstructures of the same architecture from alloyed quantum dots and their mixtures with gold nanoparticles. It was found that the concentration of gold nanoparticles strongly affects the QD optical properties in the superstructure: a 2.5-times PL enhancement for a 2% Au nanoparticle content is reported. We offer a detailed model describing the stages of superstructure formation and reveal the mechanisms behind this. Material-indifferent means of control over the shape and properties of self-assembled superstructures give us a new functional tool for developing metamaterials with potential applications in sensorics.
A procedure has been developed for the annulation of a 2-(thi)oxo-1,3-dithiole-4,5-dithiolate fragment to 3,6-di-
tert
-butyl-
o
-benzoquinone. The resulting
o
-quinones have a significant asymmetry ...with respect to the plane of the chelate dioxolene site, which can be used in the targeted design of the coordination environment of metal ions in complexes. Isomeric manganese adducts containing dioxolene, carbonyl, and phosphine ligands, which differ in the location of the asymmetric
o
-quinone ligand, have been characterized by EPR spectroscopy.
Abstract
The charge carrier density distribution in uniformly doped AlGaAs/GaAs superlattices with layer thicknesses of 1.5/10 nm and different numbers of quantum wells was studied. Both energy band ...theory and capacitance–voltage profiling were used to determine the carrier concentration profiles of the structures. During the analysis of the experimental and simulated capacitance–voltage characteristics, it was found that the maximum electron concentrations increase with an increase in the number of quantum wells from ∼
7.1
⋅
10
16
cm
−
3
for three wells to ∼
9.3
⋅
10
16
cm
−
3
for 25 wells with an overall superlattice doping level of ∼
10
17
cm
−
3
.
The bactericidal properties of cloths modified with bimetallic Cu-Ag and Fe-Ag and monometallic Ag nanoparticles, including against the most resistant bacteria strains and those associated with ...nosocomial infections such as
Escherichia coli
,
Staphylococcus aureus
,
Acinetobacter baumannii
,
Pseudomonas aeruginosa
,
Klebsiella pneumoniae
,
Enterococcus faecalis
, and
Enterobacter aerogenes
, were investigated. Photomicrographs obtained using a JEOL JSM-6390 LA scanning electron microscope were presented. The substrates acquired colors characteristic of reflectance spectra taken on a Shimadzu UV-2401PC spectrophotometer during the modification process.
Synthetic high-pressure high-temperature (HPHT) microdiamonds demonstrate strong resonant-like enhancement of the NV− photoluminescence (PL) at unexpectedly low concentration of the substitutional ...nitrogen atoms (NS) of 90 ppm, which is significantly smaller than the ∼250 ppm characteristic for conventional HPHT synthesis. The EPR, Raman, and luminescent spectroscopies, including time-resolved PL, provide evidence that this is due to competition between the increase in PL with increasing concentration of the NV− centers and nonradiative deactivation of these centers by defects induced by the NS in the diamond crystal lattice. It is suggested that the intensity of the NV− center emission can be optimized by the appropriate choice of nitrogen doping concentration which does not substantially disrupt the diamond crystal lattice.
A series of
o
-benzoquinones containing 2,4,4-trimethyl-2-pentyl (
tert
-octyl) substituents were synthesized. The stability of the reduced forms of the synthesized
o
-quinones and the electron ...density distribution in the corresponding radical anion species were studied by cyclic voltammetry and EPR spectroscopy.
The reaction of benzyl phenyl ketazine with PCl
3
in tetrahydrofuran affords 2-(1,2-diphenylvinyl)-4,5-diphenyl-2
H
-1,2,3diazaphosphole (
1
). An unusual 1,3-addition of methyllithium at the ...nitrogen (N-Li) and phosphorus (P-Me) atoms of diazaphosphole was discovered. The reduction peak potentials of diazaphosphole (
1
) and the starting ketazine were measured by cyclic voltammetry.
The borane reduction of carbon dioxide bound to aluminum hydrides supported by redox-active acenaphthene-1,2-diimine ligands, {(dpp-bian)AlO
2
CH
2
}
2
(
1
) (dpp-bian is ...1,2-bis(2,6-diisopropylphenyl)iminoacenaphthene) and (Ar
BIG
-bian)Al(μ-OC(H)O)
2
-Li(thf)
2
(
2
) (Ar
BIG
-bian is 1,2-bis(2,6-dibenzhydryl-4-methylphenyl)iminoacenaph-thene), was explored. The reaction of
1
with dimethylaminoborane (1:2) in toluene gives the paramagnetic methoxy-containing aluminum complex {(dpp-bian)Al(OMe)}
2
(μ-O) (
3
), whereas
2
is inert toward BH
3
• NHMe
2
, but the reduction of
2
with pinacolborane HBpin (1:4) affords the mixed derivative (Ar
BIG
-bian)Al(OCH
3
)(OBpin)Li(thf)
2
(
4
). Compounds
3
and
4
were characterized by elemental analysis, EPR and NMR spectroscopy, IR spectroscopy, and X-ray diffraction. The energy parameters of the reaction of
1
with dimethylaminoborane were evaluated and the paramagnetic electronic ground state of molecule
3
was confirmed by quantum chemical calculations.
The reactions of bimetallic acenaphthene-1,2-diimine complex (Dpp-bian-GaCr(CO)
5
2
-Na(Thf)
2
2
(
I
) (Dpp-bian = 1,2-bis(2,6-diisopropylphenyl)iminoacenaphthene) with 4,4'-bipyridine (4,4'-Bipy) ...and 1,3-bis(4-pyridyl)propane (Bpp) in THF gave 3D coordination polymers {(Dpp-bian)GaCr(CO)
5
}{Na(4,4'-Bipy)
3
}
n
(
II
) and (Dpp-bian)GaCr(CO)
4
Na(Et
2
O)(Bpp)
1,5
n
(
III
), respectively. Compounds
II
and
III
were characterized by elemental analysis and NMR and IR spectroscopy. The molecular structure of
II
was established by X-ray diffraction (CCDC no. 2278024).
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