9 research outputs found
Photoinduced Electron Transfer between Ruthenium-bipyridyl Complex and Methylviologen in Suspensions of Smectite Clays
We examined photoinduced electron transfer (PET) in multicomponent
aqueous suspensions composed of trisĀ(2,2ā²-bipyridine)ĀrutheniumĀ(II)
(RuĀ(bpy)<sub>3</sub><sup>2+</sup>, photocatalyst), methylviologen
(1,1ā²-dimethyl-4,4ā²-bipyridinium dication, MV<sup>2+</sup>, electron acceptor), and ethylenediamine tetraacetate (EDTA, sacrificial
electron donor) together with particles of smectite-type clays although
previous studies indicated inhibition of the electron transfer from
RuĀ(bpy)<sub>3</sub><sup>2+</sup> to MV<sup>2+</sup> in the presence
of clay particles. Clays with different lateral particle sizes were
compared: hectorite (Hect) and saponite (Sapo) with small particle
sizes (ā¼30 nm) and fluorohectorite (FH) and montmorillonite
(Mont) with large particle sizes (>0.1 Ī¼m). Clay particles
were
flocculated and were settled in many cases after the addition of RuĀ(bpy)<sub>3</sub><sup>2+</sup>, MV<sup>2+</sup>, and EDTA species, and the
RuĀ(bpy)<sub>3</sub><sup>2+</sup> and MV<sup>2+</sup> cations were
almost all adsorbed on the clay particles. When Hect and Sapo were
used, reduction of MV<sup>2+</sup> was observed on the aggregated
clay particles upon visible light irradiation indicating the occurrence
of PET from RuĀ(bpy)<sub>3</sub><sup>2+</sup> to MV<sup>2+</sup>. However,
the reaction was not observed for the samples where the clay particles
were not settled. When FH and Mont were used, PET was not observed
irrespective of the flocculation of clay particles. These results
demonstrated that PET from RuĀ(bpy)<sub>3</sub><sup>2+</sup> to MV<sup>2+</sup> in the presence of clay particles is possible when the clay
particles with small sizes are appropriately aggregated to allow interparticle
electron hopping
Real-Time Monitoring of Adsorption-Induced Scrolling of Colloidal Inorganic Nanosheets
Inorganic nanotubes have attracted
much attention due
to their
unique physicochemical properties. Nanotubes can be prepared by scrolling
exfoliated nanosheets under ambient conditions. However, how the nanosheet
scrolled in its colloidal state has not been experimentally visualized.
In this paper, we directly observed the scrolling process of nanosheets
upon adsorption of organic cations. Exfoliated flat nanosheets of
niobate and clay in aqueous colloids were found to scroll by adding
organic cations, such as exfoliation reagents, to the colloids. Employment
of cationic stilbazolium dye enabled in situ observation of the dye
adsorption and scrolling by optical microscopy based on changes in
color and morphology of the nanosheets. The scrolling was promoted
for nanosheets adsorbed with a stilbazolium dye with a longer alkyl
chain, suggesting that the interaction between the hydrophobic parts
of the dye cations is the driving force of the scrolling. This finding
should encourage research on the formation of nanotubes from nanosheets
and also provides important guidelines for the selection of appropriate
exfoliation reagents when exfoliating nanosheets from layered crystals
Real-Time Monitoring of Adsorption-Induced Scrolling of Colloidal Inorganic Nanosheets
Inorganic nanotubes have attracted
much attention due
to their
unique physicochemical properties. Nanotubes can be prepared by scrolling
exfoliated nanosheets under ambient conditions. However, how the nanosheet
scrolled in its colloidal state has not been experimentally visualized.
In this paper, we directly observed the scrolling process of nanosheets
upon adsorption of organic cations. Exfoliated flat nanosheets of
niobate and clay in aqueous colloids were found to scroll by adding
organic cations, such as exfoliation reagents, to the colloids. Employment
of cationic stilbazolium dye enabled in situ observation of the dye
adsorption and scrolling by optical microscopy based on changes in
color and morphology of the nanosheets. The scrolling was promoted
for nanosheets adsorbed with a stilbazolium dye with a longer alkyl
chain, suggesting that the interaction between the hydrophobic parts
of the dye cations is the driving force of the scrolling. This finding
should encourage research on the formation of nanotubes from nanosheets
and also provides important guidelines for the selection of appropriate
exfoliation reagents when exfoliating nanosheets from layered crystals
Real-Time Monitoring of Adsorption-Induced Scrolling of Colloidal Inorganic Nanosheets
Inorganic nanotubes have attracted
much attention due
to their
unique physicochemical properties. Nanotubes can be prepared by scrolling
exfoliated nanosheets under ambient conditions. However, how the nanosheet
scrolled in its colloidal state has not been experimentally visualized.
In this paper, we directly observed the scrolling process of nanosheets
upon adsorption of organic cations. Exfoliated flat nanosheets of
niobate and clay in aqueous colloids were found to scroll by adding
organic cations, such as exfoliation reagents, to the colloids. Employment
of cationic stilbazolium dye enabled in situ observation of the dye
adsorption and scrolling by optical microscopy based on changes in
color and morphology of the nanosheets. The scrolling was promoted
for nanosheets adsorbed with a stilbazolium dye with a longer alkyl
chain, suggesting that the interaction between the hydrophobic parts
of the dye cations is the driving force of the scrolling. This finding
should encourage research on the formation of nanotubes from nanosheets
and also provides important guidelines for the selection of appropriate
exfoliation reagents when exfoliating nanosheets from layered crystals
Real-Time Monitoring of Adsorption-Induced Scrolling of Colloidal Inorganic Nanosheets
Inorganic nanotubes have attracted
much attention due
to their
unique physicochemical properties. Nanotubes can be prepared by scrolling
exfoliated nanosheets under ambient conditions. However, how the nanosheet
scrolled in its colloidal state has not been experimentally visualized.
In this paper, we directly observed the scrolling process of nanosheets
upon adsorption of organic cations. Exfoliated flat nanosheets of
niobate and clay in aqueous colloids were found to scroll by adding
organic cations, such as exfoliation reagents, to the colloids. Employment
of cationic stilbazolium dye enabled in situ observation of the dye
adsorption and scrolling by optical microscopy based on changes in
color and morphology of the nanosheets. The scrolling was promoted
for nanosheets adsorbed with a stilbazolium dye with a longer alkyl
chain, suggesting that the interaction between the hydrophobic parts
of the dye cations is the driving force of the scrolling. This finding
should encourage research on the formation of nanotubes from nanosheets
and also provides important guidelines for the selection of appropriate
exfoliation reagents when exfoliating nanosheets from layered crystals
Real-Time Monitoring of Adsorption-Induced Scrolling of Colloidal Inorganic Nanosheets
Inorganic nanotubes have attracted
much attention due
to their
unique physicochemical properties. Nanotubes can be prepared by scrolling
exfoliated nanosheets under ambient conditions. However, how the nanosheet
scrolled in its colloidal state has not been experimentally visualized.
In this paper, we directly observed the scrolling process of nanosheets
upon adsorption of organic cations. Exfoliated flat nanosheets of
niobate and clay in aqueous colloids were found to scroll by adding
organic cations, such as exfoliation reagents, to the colloids. Employment
of cationic stilbazolium dye enabled in situ observation of the dye
adsorption and scrolling by optical microscopy based on changes in
color and morphology of the nanosheets. The scrolling was promoted
for nanosheets adsorbed with a stilbazolium dye with a longer alkyl
chain, suggesting that the interaction between the hydrophobic parts
of the dye cations is the driving force of the scrolling. This finding
should encourage research on the formation of nanotubes from nanosheets
and also provides important guidelines for the selection of appropriate
exfoliation reagents when exfoliating nanosheets from layered crystals
Pickering Emulsions Prepared by Layered Niobate K<sub>4</sub>Nb<sub>6</sub>O<sub>17</sub> Intercalated with Organic Cations and Photocatalytic Dye Decomposition in the Emulsions
We investigated emulsions stabilized with particles of
layered
hexaniobate, known as a semiconductor photocatalyst, and photocatalytic
degradation of dyes in the emulsions. Hydrophobicity of the niobate
particles was adjusted with the intercalation of alkylammonium ions
into the interlayer spaces to enable emulsification in a tolueneāwater
system. After the modification of interlayer space with hexylammonium
ions, the niobate stabilized water-in-oil (w/o) emulsions in a broad
composition range. Optical microscopy showed that the niobate particles
covered the surfaces of emulsion droplets and played a role of emulsifying
agents. The niobate particles also enabled the generation of oil-in-water
(o/w) emulsions in a limited composition range. Modification with
dodecylammonium ions, which turned the niobate particles more hydrophobic,
only gave w/o emulsions, and the particles were located not only at
the tolueneāwater interface but also inside the toluene continuous
phase. On the other hand, interlayer modification with butylammonium
ions led to the formation of o/w emulsions. When porphyrin dyes were
added to the system, the cationic dye was adsorbed on niobate particles
at the emulsion droplets whereas the lipophilic dye was dissolved
in toluene. Upon UV irradiation, both of the dyes were degraded photocatalytically.
When the cationic and lipophilic porphyrin molecules were simultaneously
added to the emulsions, both of the dyes were photodecomposed nonselectively
Radiation Pressure Induced Hierarchical Structure of Liquid Crystalline Inorganic Nanosheets
Although
hierarchical assemblies of colloidal particles add novel
structure-based functions to systems, few local and on-demand colloidal
structures have been developed. We have combined the colloidal liquid
crystallinity of two-dimensional inorganic particles and laser radiation
pressure to obtain a large hierarchical and local structure in a colloidal
system. The scattering force of the laser beam converted the parallel
nanosheet alignment to the direction of the incident laser beam. At
the focal point, the nanosheet orientation depends on the electric
field of the polarized laser beam. In contrast, a giant tree-ring-like
nanosheet texture of more than 100 Ī¼m, and which is independent
of the polarization direction, was organized at the periphery of the
focal point. This organization resulted from a cooperative effect
between the liquid-crystalline nanosheets, which indicates an effectiveness
of optical manipulation to construct hierarchical colloidal structures
with the aid of interparticle interactions
Radiation Pressure Induced Hierarchical Structure of Liquid Crystalline Inorganic Nanosheets
Although
hierarchical assemblies of colloidal particles add novel
structure-based functions to systems, few local and on-demand colloidal
structures have been developed. We have combined the colloidal liquid
crystallinity of two-dimensional inorganic particles and laser radiation
pressure to obtain a large hierarchical and local structure in a colloidal
system. The scattering force of the laser beam converted the parallel
nanosheet alignment to the direction of the incident laser beam. At
the focal point, the nanosheet orientation depends on the electric
field of the polarized laser beam. In contrast, a giant tree-ring-like
nanosheet texture of more than 100 Ī¼m, and which is independent
of the polarization direction, was organized at the periphery of the
focal point. This organization resulted from a cooperative effect
between the liquid-crystalline nanosheets, which indicates an effectiveness
of optical manipulation to construct hierarchical colloidal structures
with the aid of interparticle interactions