7 research outputs found
Composition-Dependent Catalytic Activity of Bimetallic Nanocrystals: AgPd-Catalyzed Hydrodechlorination of 4‑Chlorophenol
Ag–Pd bimetallic nanocrystals
(NCs) with tunable compositions and narrow size distributions were
produced by a one-pot synthesis. The NC growth process was investigated
by time-dependent TEM, XRD, and UV–vis studies. In the hydrodechlorination
of 4-chlorophenol, the AgPd<sub><i>x</i></sub> (<i>x</i> = 2, 4, 6, 9, 19) showed pronounced composition-dependent
catalytic activities, leading to the AgPd<sub>9</sub> catalyst with
excellent activity
Single-Crystalline Octahedral Au–Ag Nanoframes
We report the formation of single-crystalline octahedral
Au–Ag
nanoframes by a modified galvanic replacement reaction. Upon sequential
addition of AgNO<sub>3</sub>, CuCl, and HAuCl<sub>4</sub> to octadecylamine
solution, truncated polyhedral silver nanoparticles formed first and
then changed into octahedral Au–Ag nanoframes, without requiring
a conventional Ag removal step with additional oxidation etchant.
The nanoframes have 12 sides, and all of the eight {111} faces are
empty. The side grows along the [110] direction, and the diameter
is less than 10 nm. The selective gold deposition on the high-energy
(110) surface, the diffusion, and the selective redeposition of Au
and Ag atoms are the key reasons for the formation of octahedral nanoframes
Syntheses of Water-Soluble Octahedral, Truncated Octahedral, and Cubic Pt–Ni Nanocrystals and Their Structure–Activity Study in Model Hydrogenation Reactions
We developed a facile strategy to synthesize a series
of water-soluble
Pt, Pt<sub><i>x</i></sub>Ni<sub>1‑<i>x</i></sub> (0 < <i>x </i>< 1), and Ni nanocrystals. The octahedral,
truncated octahedral, and cubic shapes were uniformly controlled by
varying crystal growth inhibition agents such as benzoic acid, aniline,
and carbon monoxide. The compositions of the Pt<sub><i>x</i></sub>Ni<sub>1‑<i>x</i></sub> nanocrystals were effectively
controlled by choice of ratios between the Pt and Ni precursors. In
a preliminary study to probe their structure–activity dependence,
we found that the shapes, compositions, and capping agents strongly
influence the catalyst performances in three model heterogeneous hydrogenation
reactions
Molybdenum Disulfide Nanoparticles as Multifunctional Inhibitors against Alzheimer’s Disease
The complex pathogenic
mechanisms of Alzheimer’s disease
(AD) include the aggregation of β-amyloid peptides (Aβ)
into oligomers or fibrils as well as Aβ-mediated oxidative stress,
which require comprehensive treatment. Therefore, the inhibition of
Aβ aggregation and free-radical scavenging are essential for
the treatment of AD. Nanoparticles (NPs) have been found to influence
Aβ aggregation process in vitro. Herein, we report the inhibition
effects of molybdenum disulfide (MoS<sub>2</sub>) NPs on Aβ
aggregation. Polyvinylpyrrolidone-functionalized MoS<sub>2</sub> NPs
were fabricated by a pulsed laser ablation method. We find that MoS<sub>2</sub> NPs exhibit multifunctional effects on Aβ peptides:
inhibiting Aβ aggregation, destabilizing Aβ fibrils, alleviating
Aβ-induced oxidative stress, as well as Aβ-mediated cell
toxicity. Moreover, we show that MoS<sub>2</sub> NPs can block the
formation of the Ca<sup>2+</sup> channel induced by Aβ fibrils
in the cell membrane for the first time. Thus, these observations
suggest that MoS<sub>2</sub> NPs have great potential for a multifunctional
therapeutic agent against amyloid-related diseases
Highly Active and Selective Catalysis of Bimetallic Rh<sub>3</sub>Ni<sub>1</sub> Nanoparticles in the Hydrogenation of Nitroarenes
Because of the requirements of sustainable
development as well
as the desirability of using molecular hydrogen as a chemical reagent,
it is of paramount importance and great challenge to develop highly
active and selective catalysts for the hydrogenation of organic molecules,
including substituted nitroarenes. We approach this question by probing
unsupported bimetallic nanoparticles. A series of novel bimetallic
Rh<sub><i>x</i></sub>Ni<sub><i>y</i></sub> (<i>x</i>, <i>y</i> = 1, 2, 3) nanoparticles were successfully
prepared using our “noble metal-induced reduction” strategy.
Unsupported Rh<sub>3</sub>Ni<sub>1</sub> nanoparticles were subsequently
identified to be a highly active and exceedingly selective catalyst
for the hydrogenation of nitroarenes under ambient conditions, underscoring
a remarkable synergistic effect of the two metals. Further experiments
showed that the Rh<sub>3</sub>Ni<sub>1</sub> catalyst could be a highly
efficient, selective, and recyclable catalyst for a range of nitroarene
substrates. This work showcased the value of bimetallic nanoparticles
in catalysts development for sustainable chemistry
Room Temperature Activation of Oxygen by Monodispersed Metal Nanoparticles: Oxidative Dehydrogenative Coupling of Anilines for Azobenzene Syntheses
It is highly challenging but desirable
to develop efficient catalysts
for the activation of oxygen under mild conditions. Here, we report
that various monodispersed metal nanoparticles (Ag, Pt, Co, Cu, Ni,
Pd, and Au) efficiently activated molecular oxygen under mild conditions,
illustrated by the aerobic oxidation of anilines to form either symmetric
or asymmetric aromatic azo compounds. This discovery indicates that
exploiting the catalytic power of nanoparticles could enable sustainable
chemistry suitable for important oxidation reactions
Direct Syntheses of Styryl Ethers from Benzyl Alcohols via Ag Nanoparticle-Catalyzed Tandem Aerobic Oxidation
Ag nanoparticle-catalyzed aerobic
oxidation of benzyl alcohols
in basic DMSO gave efficient formation of styryl ethers, featuring
single carbon transfer and CC and C–O bond formation.
A deuterium labeling experiment established that DMSO was the carbon
source. Further experiments showed the reaction proceeded through
a styryl sulfoxide intermediate originating from basic DMSO and transient
benzaldehyde. Control reactions in the absence of the Ag NPs or air
indicated that oxidation of the styryl sulfoxide was required for
the final C–O bond formation. This work demonstrated that metal
nanoparticles could be applied to tandem heterogeneous catalysis in
organic chemistry