5 research outputs found
Nanocrystalline TiO<sub>2</sub>‑Catalyzed Photoreversible Color Switching
We
report a novel photoreversible color switching system based
on the photocatalytic activity of TiO<sub>2</sub> nanocrystals and
the redox-driven color switching property of methylene blue (MB).
This system rapidly changes from blue to colorless under UV irradiation
and recovers its original blue color under visible light irradiation.
We have identified four major competing reactions that contribute
to the photoreversible switching, among which two are dominant: the
decoloration process is mainly driven by the reduction of MB to leuco
MB by photogenerated electrons from TiO<sub>2</sub> nanocrystals under
UV irradiation, and the recoloration process operates by the TiO<sub>2</sub>-induced self-catalyzed oxidation of LMB under visible irradiation.
Compared with the conventional color switching systems based on photoisomerization
of chromophores, our system has not only low toxicity but also significantly
improved switching rate and cycling performance. It is envisioned
that this photoreversible system may promise unique opportunities
for many light-driven actuating or color switching applications
Porous TiO<sub>2</sub>/C Nanocomposite Shells As a High-Performance Anode Material for Lithium-Ion Batteries
Porous
TiO<sub>2</sub>/C nanocomposite shells with high capacity,
excellent cycle stability, and rate performance have been prepared.
The synthesis involves coating colloidal TiO<sub>2</sub> nanoshells
with a resorcinol-formaldehyde (RF) layer with controllable thickness
through a sol–gel-like process, and calcining the composites
at 700 °C in an inert atmosphere to induce crystallization from
amorphous TiO<sub>2</sub> to anatase and simultaneous carbonization
from RF to carbon. The cross-linked RF polymer contributes to the
high stability of the shell morphology and the porous nature of the
shells. A strong dependence of the capacity on the amount of incorporated
carbon has been revealed, allowing the optimization of the electrode
structure for high-rate cell performance
Coassembly of Mixed Weakley-Type Polyoxometalates to Novel Nanoflowers with Tunable Fluorescence for the Detection of Toluene
In
this work, three-dimensional nanoflowers with tunable fluorescent
properties constructed with mixed Weakley-type polyoxometalates (POMs,
Na<sub>9</sub>[LnW<sub>10</sub>O<sub>36</sub>]·32H<sub>2</sub>O, Ln = Eu, Tb, abbreviated to LnW<sub>10</sub>) and tetraethylenepentamine
(TEPA) have been successfully prepared through a facile ionic self-assembly
(ISA) method. The shape and petal size of the nanoflower as well as
its fluorescent behaviors can be tuned through varying the ratio of
EuW<sub>10</sub>/TbW<sub>10</sub>. The varied-temperature emission
behaviors at 80–260 K show that the fluorescent intensity of
both Tb<sup>3+</sup> and Eu<sup>3+</sup> decreased with the increase
in temperature, which makes them potential luminescent ratiometric
thermometers. Moreover, after being mixed with polydimethylsiloxane
(PDMS), the as-formed hybrid films showed stable fluorescence along
with good transparency. The robustness of the hybrid films was also
demonstrated by corrosion resistance upon treatment with strong acid
and alkali and thus can be used as a sensor to detect toluene circularly.
Our results provide a new avenue to the facile construction of fluorescent
composites and demonstrate that the POM complexes can be further used
in supramolecular chemistry and nanomaterials
Reversible Assembly and Dynamic Plasmonic Tuning of Ag Nanoparticles Enabled by Limited Ligand Protection
Dynamic
manipulation of optical properties through the reversible
assembly of plasmonic nanoparticles offers great opportunities for
practical applications in many fields. The previous success, however,
has been limited to Au nanoparticles. Reversible assembly and plasmonic
tuning of Ag nanoparticles (AgNPs) have remained a significant challenge
due to difficulty in finding an appropriate surface agent that can
effectively stabilize the particle surface and control their interactions.
Here, we overcome the challenge by developing a limited-ligand-protection
(LLP) strategy for introducing polyÂ(acrylic acid) with precisely controlled
coverage to the AgNP surface to not only sufficiently stabilize the
nanoparticles but also enable effective control over the surface charge
and particle interaction through pH variation. The as-synthesized
AgNPs can be reversibly assembled and disassembled and accordingly
display broadly tunable coupling of plasmonic properties. Compared
to the Au-based system, the success in the reversible assembly of
AgNPs represents a significant step toward practical applications
such as colorimetric pressure sensing because they offer many advantages,
including broader spectral tuning range, higher color contrast, a
one-pot process, and low materials and production cost. This work
also highlights LLP as a new avenue for controlling the interparticle
forces, their reversible assembly, and dynamic coupling of physical
properties
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Photocatalytic Color Switching of Transition Metal Hexacyanometalate Nanoparticles for High-Performance Light-Printable Rewritable Paper
Developing
efficient photoreversible color switching systems for constructing
rewritable paper is of significant practical interest owing to the
potential environmental benefits including forest conservation, pollution
reduction, and resource sustainability. Here we report that the color
change associated with the redox chemistry of nanoparticles of Prussian
blue and its analogues could be integrated with the photocatalytic
activity of TiO<sub>2</sub> nanoparticles to construct a class of
new photoreversible color switching systems, which can be conveniently
utilized for fabricating ink-free, light printable rewritable paper
with various working colors. The current system also addresses the
phase separation issue of the previous organic dye-based color switching
system so that it can be conveniently applied to the surface of conventional
paper to produce an ink-free light printable rewritable paper that
has the same feel and appearance as the conventional paper. With its
additional advantages such as excellent scalability and outstanding
rewriting performance (reversibility >80 times, legible time >5
days, and resolution >5 μm), this novel system can serve
as an eco-friendly alternative to regular paper in meeting the increasing
global needs for environment protection and resource sustainability