162 research outputs found
Fixing Colloidal Motions at Water/Air Interface with Micrometer Scale Resolution
Fast
colloidal motions driven by surface tension gradient are created
in a thin water layer. Unlike using solid boundaries to limit the
colloidal flow, our work relaxes this condition by directly placing
bulk fluid next to an open air environment. When the colloidal flow
along the air/water interface is interfered with stationary objects,
repetitive semicircular motions, that is, micro eddy, are frequently
observed in domains as small as 2 μm. We assign the capillary
convection between the liquid next to the air and that from the bulk
as the driving force for the observed motions. Relationships among
the maximum speed, temperature gradient, and thickness of the liquid
layer are experimentally investigated and numerically analyzed. Our
results could inspire future designs of micromechanical motors or
fluidic mixing in a miniature device
Fixing Colloidal Motions at Water/Air Interface with Micrometer Scale Resolution
Fast
colloidal motions driven by surface tension gradient are created
in a thin water layer. Unlike using solid boundaries to limit the
colloidal flow, our work relaxes this condition by directly placing
bulk fluid next to an open air environment. When the colloidal flow
along the air/water interface is interfered with stationary objects,
repetitive semicircular motions, that is, micro eddy, are frequently
observed in domains as small as 2 μm. We assign the capillary
convection between the liquid next to the air and that from the bulk
as the driving force for the observed motions. Relationships among
the maximum speed, temperature gradient, and thickness of the liquid
layer are experimentally investigated and numerically analyzed. Our
results could inspire future designs of micromechanical motors or
fluidic mixing in a miniature device
Fixing Colloidal Motions at Water/Air Interface with Micrometer Scale Resolution
Fast
colloidal motions driven by surface tension gradient are created
in a thin water layer. Unlike using solid boundaries to limit the
colloidal flow, our work relaxes this condition by directly placing
bulk fluid next to an open air environment. When the colloidal flow
along the air/water interface is interfered with stationary objects,
repetitive semicircular motions, that is, micro eddy, are frequently
observed in domains as small as 2 μm. We assign the capillary
convection between the liquid next to the air and that from the bulk
as the driving force for the observed motions. Relationships among
the maximum speed, temperature gradient, and thickness of the liquid
layer are experimentally investigated and numerically analyzed. Our
results could inspire future designs of micromechanical motors or
fluidic mixing in a miniature device
A Bicyclo[4.2.0]octene-Derived Monomer Provides Completely Linear Alternating Copolymers via Alternating Ring-Opening Metathesis Polymerization (AROMP)
Strained bicyclic carbomethoxy olefins
were utilized as substrates
in alternating ring-opening metathesis polymerization and found to
provide low-dispersity polymers with novel backbones. The polymerization
of methyl bicyclo[4.2.0]Âoct-7-ene-7-carboxylate with cyclohexene in
the presence of the fast-initiating Grubbs catalyst (H<sub>2</sub>IMes)Â(3-Br-Pyr)<sub>2</sub>Cl<sub>2</sub>Ruî—»CHPh leads to
a completely linear as well as alternating copolymer, as demonstrated
by NMR spectroscopy, isotopic labeling, and gel permeation chromatography.
In contrast, intramolecular chain-transfer reactions were observed
with [5.2.0] and [3.2.0] bicyclic carbomethoxy olefins, although to
a lesser extent than with the previously reported monocyclic cyclobutenecarboxylic
ester monomers [Song, A.; Parker, K. A.; Sampson, N. S. J. Am. Chem. Soc. 2009, 131, 3444]. Inclusion of cyclohexyl rings fused to the copolymer backbone
minimizes intramolecular chain-transfer reactions and provides a framework
for creating alternating functionality in a one-step polymerization
Color and Texture Morphing with Colloids on Multilayered Surfaces
Dynamic
morphing of marine species to match with environment changes in color
and texture is an advanced means for surviving, self-defense, and
reproduction. Here we use colloids that are placed inside a multilayered
structure to demonstrate color and texture morphing. The multilayer
is composed of a thermal insulating base layer, a light absorbing
mid layer, and a liquid top layer. When external light of moderate
intensity (∼0.2 W cm<sup>–2</sup>) strikes the structure,
colloids inside the liquid layer will be assembled to locations with
an optimal absorption. When this system is exposed to continuous laser
pulses, more than 18 000 times of reversible responses are
recorded, where the system requests 20 ms to start the response and
another 160 ms to complete. The flexibility of our concept further
allows the system to be built on a variety of light-absorbing substrates,
including dyed paper, gold thin film, and amorphous silicon, with
the top layer even a solid
Ru-Catalyzed Isomerization Provides Access to Alternating Copolymers via Ring-Opening Metathesis Polymerization
We describe an isomerization–alternating
ROMP protocol that
gives linear copolymers with rigorous sequence alternation. Bicyclo[4.2.0]Âoct-7-ene-7-carboxamides
of primary amines are isomerized in the presence of (3-BrPyr)<sub>2</sub>Cl<sub>2</sub>(H<sub>2</sub>IMes)ÂRuî—»CHPh to the corresponding
bicyclo[4.2.0]Âoct-1(8)-ene-8-carboxamides in which the olefinic bond
is tetrasubstituted. The <i>isomerized</i> amides undergo
alternating ring-opening metathesis polymerization with cyclohexene
to provide soluble and linear copolymers with molecular weights up
to ∼130 kDa. This process provides efficient entry to strictly
alternating copolymers that can display diverse functional groups
Self-Templated Synthesis of Porous Ni(OH)<sub>2</sub> Nanocube and Its High Electrochemical Performance for Supercapacitor
Porous NiÂ(OH)<sub>2</sub> nanocubes
were successfully fabricated
by a simple self-sacrificial-template protocol using Ni–Co
Prussian blue analogue (PBA) as precursor. When treated with NaOH,
the simultaneous corrosion of Ni–Co PBA precursor and formation
of amorphous NiÂ(OH)<sub>2</sub> resulted in porous NiÂ(OH)<sub>2</sub> nanocubes with uniform size of about 100 nm. Due to the large specific
surface area and unique regular porous structure, the as-prepared
materials showed large specific capacitance, relatively stable rate
capability and long cycle stability when used as electrode materials
for supercapacitors. With the voltage between 0.00 and 0.45 V versus
Ag/AgCl, the specific capacitance can achieve 1842 F/g at a current
density of 1 A/g
Highly Efficiently Delaminated Single-Layered MXene Nanosheets with Large Lateral Size
Single
layered Ti<sub>3</sub>C<sub>2</sub>(OH)<sub>2</sub> nanosheets
have been successfully fabricated by etching its Ti<sub>3</sub>AlC<sub>2</sub> precursor with KOH in the presence of a small amount of water.
The OH group replaced the Al layer within the Ti<sub>3</sub>AlC<sub>2</sub> structure during etching, and Ti<sub>3</sub>C<sub>2</sub>(OH)<sub>2</sub> nanosheets could be easily and efficiently achieved
through a simple washing process. The delaminated single-layered nanosheets
are clearly revealed by atomic force microscopy to be several micrometers
in lateral size. Interestingly, the exfoliated Ti<sub>3</sub>C<sub>2</sub>(OH)<sub>2</sub> nanosheets could be restacked to form a new
layer-structured material after drying. When redispersing this restacked
Ti<sub>3</sub>C<sub>2</sub>(OH)<sub>2</sub> materials in water again,
it could be re-delaminated easily only after shaking for several hours.
The easy delamination and restacking properties, coupled with intrinsic
metallic conductivity and hydrophilicity, make it an ideal two-dimensional
building block for fabricating a wide variety of functional materials
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Rational design of liquid metal organic frameworks for the enhanced CO2 absorption and their photocatalytic reduction
Metal organic frameworks (MOFs) has been widely investigated as co-catalysts for photocatalysis owing to their unique property for controlling the reaction kinetics. They are generally presented in a solid state. Recent studies have presented MOF in the liquid phase, meanwhile preserving the framework structure. Acting as a co-catalyst, significantly improved efficiency has been realized for photocatalytic CO2 reduction. This concept article focuses on the chemical principle of liquid MOF (LMOF). Their applications in CO2 adsorption and the photocatalytic CO2 reduction have been discussed with showing key examples. In addition, the other relevant applications of LMOF have been presented. </p
Alternating Ring-Opening Metathesis Polymerization Copolymers Containing Charge-Transfer Units
Alternating
copolymers derived from the ring-opening metathesis
polymerization (ROMP) of functionalized cyclobutene esters (CBEs)
and cyclohexenes (CHs) are described. The copolymer polyÂ(CBE-<i>alt</i>-CH)<sub><i>n</i></sub> contains alternating
side chains based on dialkoxynaphthalene (DAN) and pyromellitic dianhydride
(PDI). Characterization by UV–vis spectroscopy showed that
the copolymers exhibit an increase in charge-transfer intensity in
comparison to previously reported alternating copolymers. The bulky
side chains inhibit backbiting during the polymerization and allow
for enhanced control over the polymerization in comparison to copolymers
functionalized with linear alkyl groups
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