25 research outputs found
Multifunctional Ultrathin Pd<sub><i>x</i></sub>Cu<sub>1–<i>x</i></sub> and Pt∼Pd<sub><i>x</i></sub>Cu<sub>1–<i>x</i></sub> One-Dimensional Nanowire Motifs for Various Small Molecule Oxidation Reactions
Developing
novel electrocatalysts for small molecule oxidation
processes, including formic acid oxidation (FAOR), methanol oxidation
reaction (MOR), and ethanol oxidation reaction (EOR), denoting the
key anodic reactions for their respective fuel cell configurations,
is a significant and relevant theme of recent efforts in the field.
Herein, in this report, we demonstrated a concerted effort to couple
and combine the benefits of small size, anisotropic morphology, and
tunable chemical composition in order to devise a novel “family”
of functional architectures. In particular, we have fabricated not
only ultrathin 1-D Pd<sub>1–<i>x</i></sub>Cu<sub><i>x</i></sub> alloys but also Pt-coated Pd<sub>1–<i>x</i></sub>Cu<sub><i>x</i></sub> (i.e., Pt∼Pd<sub>1–<i>x</i></sub>Cu<sub><i>x</i></sub>;
herein the ∼ indicates an intimate association, but not necessarily
actual bond formation, between the inner bimetallic core and the Pt
outer shell) core–shell hierarchical nanostructures with readily
tunable chemical compositions by utilizing a facile, surfactant-based,
wet chemical synthesis coupled with a Cu underpotential deposition
technique. Our main finding is that our series of as-prepared nanowires
are functionally flexible. More precisely, we demonstrate that various
examples within this “family” of structural motifs can
be tailored for exceptional activity with all 3 of these important
electrocatalytic reactions. In particular, we note that our series
of Pd<sub>1–<i>x</i></sub>Cu<sub><i>x</i></sub> nanowires all exhibit enhanced FAOR activities as compared
with not only analogous Pd ultrathin nanowires but also commercial
Pt and Pd standards, with Pd<sub>9</sub>Cu representing the “optimal”
composition. Moreover, our group of Pt∼Pd<sub>1–<i>x</i></sub>Cu<sub><i>x</i></sub> nanowires consistently
outperformed not only commercial Pt NPs but also ultrathin Pt nanowires
by several fold orders of magnitude for both the MOR and EOR reactions
in alkaline media. The variation of the MOR and EOR performance with
the chemical composition of our ultrathin Pt∼Pd<sub>1–<i>x</i></sub>Cu<sub><i>x</i></sub> nanowires was also
discussed
Probing Ultrathin One-Dimensional Pd–Ni Nanostructures As Oxygen Reduction Reaction Catalysts
An
ambient, surfactant-based synthetic means was used to prepare
ultrathin binary (<i>d</i> ∼ 2 nm) Pd–Ni nanowires,
which were subsequently purified using a novel butylamine-based surfactant-exchange
process coupled with an electrochemical CO adsorption and stripping
treatment to expose active surface sites. We were able to systematically
vary the chemical composition of as-prepared Pd–Ni nanowires
from pure elemental Pd to Pd<sub>0.50</sub>Ni<sub>0.50</sub> (atomic
ratio), as verified using EDS analysis. The overall morphology of
samples possessing >60 atom % Pd consisted of individual, discrete
one-dimensional nanowires. The electrocatalytic performances of elemental
Pd, Pd<sub>0.90</sub>Ni<sub>0.10</sub>, Pd<sub>0.83</sub>Ni<sub>0.17</sub>, and Pd<sub>0.75</sub>Ni<sub>0.25</sub> nanowires in particular
were examined. Our results highlight a “volcano”-type
relationship between chemical composition and corresponding ORR activities
with Pd<sub>0.90</sub>Ni<sub>0.10</sub>, yielding the highest activity
(i.e., 1.96 mA/cm<sup>2</sup> at 0.8 V) among all nanowires tested.
Moreover, the Pd<sub>0.90</sub>Ni<sub>0.10</sub> sample exhibited
outstanding methanol tolerance ability. In essence, there was only
a relatively minimal 15% loss in the specific activity in the presence
of 4 mM methanol, which was significantly better than analogous data
on Pt nanoparticles and Pt nanowires. In addition, we also studied
ultrathin, core–shell Pt∼Pd<sub>0.90</sub>Ni<sub>0.10</sub> nanowires, which exhibited a specific activity of 0.62 mA/cm<sup>2</sup> and a corresponding mass activity of 1.44 A/mg<sub>Pt</sub> at 0.9 V. Moreover, our as-prepared core–shell electrocatalysts
maintained excellent electrochemical durability. We postulate that
one-dimensional Pd–Ni nanostructures represent a particularly
promising platform for designing ORR catalysts with high performance
Synthesis, Characterization, and Formation Mechanism of Crystalline Cu and Ni Metallic Nanowires under Ambient, Seedless, Surfactantless Conditions
In
this report, crystalline elemental Cu and Ni nanowires have
been successfully synthesized through a simplistic, malleable, solution-based
protocol involving the utilization of a U-tube double diffusion apparatus
under ambient conditions. The nanowires prepared within the 50 and
200 nm template membrane pore channels maintain diameters ranging
from ∼90–230 nm with lengths attaining the micrometer
scale. To mitigate for the unwanted but very facile oxidation of these
nanomaterials to their oxide analogues, our synthesis mechanism relies
on a carefully calibrated reaction between the corresponding metal
precursor solution and an aqueous reducing agent solution, resulting
in the production of pure, monodisperse metallic nanostructures. These
as-prepared nanowires were subsequently characterized from an applications’
perspective so as to investigate their optical and photocatalytic
properties
Robust but On-Demand Detachable Wet Tissue Adhesive Hydrogel Enhanced with Modified Tannic Acid
Adhesives with robust but readily detachable wet tissue
adhesion
are of great significance for wound closure. Polyelectrolyte complex
adhesive (PECA) is an important wet tissue adhesive. However, its
relatively weak cohesive and adhesive strength cannot satisfy clinical
applications. Herein, modified tannic acid (mTA) with a catechol group,
a long alkyl hydrophobic chain, and a phenyl group was prepared first,
and then, it was mixed with acrylic acid (AA) and polyethylenimine
(PEI), followed by UV photopolymerization to make a wet tissue adhesive
hydrogel with tough cohesion and adhesion strength. The hydrogel has
a strong wet tissue interfacial toughness of ∼1552 J/m2, good mechanical properties (∼7220 kPa cohesive strength,
∼873% strain, and ∼33,370 kJ/m3 toughness),
and a bursting pressure of ∼1575 mmHg on wet porcine skin.
The hydrogel can realize quick and effective adhesion to various wet
biological tissues including porcine skin, liver, kidney, and heart
and can be changed easily with triggering urea solution to avoid tissue
damage or uncomfortable pain to the patient. This biosafe adhesive
hydrogel is very promising for wound closure and may provide new ideas
for the design of robust wet tissue adhesives
Robust but On-Demand Detachable Wet Tissue Adhesive Hydrogel Enhanced with Modified Tannic Acid
Adhesives with robust but readily detachable wet tissue
adhesion
are of great significance for wound closure. Polyelectrolyte complex
adhesive (PECA) is an important wet tissue adhesive. However, its
relatively weak cohesive and adhesive strength cannot satisfy clinical
applications. Herein, modified tannic acid (mTA) with a catechol group,
a long alkyl hydrophobic chain, and a phenyl group was prepared first,
and then, it was mixed with acrylic acid (AA) and polyethylenimine
(PEI), followed by UV photopolymerization to make a wet tissue adhesive
hydrogel with tough cohesion and adhesion strength. The hydrogel has
a strong wet tissue interfacial toughness of ∼1552 J/m2, good mechanical properties (∼7220 kPa cohesive strength,
∼873% strain, and ∼33,370 kJ/m3 toughness),
and a bursting pressure of ∼1575 mmHg on wet porcine skin.
The hydrogel can realize quick and effective adhesion to various wet
biological tissues including porcine skin, liver, kidney, and heart
and can be changed easily with triggering urea solution to avoid tissue
damage or uncomfortable pain to the patient. This biosafe adhesive
hydrogel is very promising for wound closure and may provide new ideas
for the design of robust wet tissue adhesives
Robust but On-Demand Detachable Wet Tissue Adhesive Hydrogel Enhanced with Modified Tannic Acid
Adhesives with robust but readily detachable wet tissue
adhesion
are of great significance for wound closure. Polyelectrolyte complex
adhesive (PECA) is an important wet tissue adhesive. However, its
relatively weak cohesive and adhesive strength cannot satisfy clinical
applications. Herein, modified tannic acid (mTA) with a catechol group,
a long alkyl hydrophobic chain, and a phenyl group was prepared first,
and then, it was mixed with acrylic acid (AA) and polyethylenimine
(PEI), followed by UV photopolymerization to make a wet tissue adhesive
hydrogel with tough cohesion and adhesion strength. The hydrogel has
a strong wet tissue interfacial toughness of ∼1552 J/m2, good mechanical properties (∼7220 kPa cohesive strength,
∼873% strain, and ∼33,370 kJ/m3 toughness),
and a bursting pressure of ∼1575 mmHg on wet porcine skin.
The hydrogel can realize quick and effective adhesion to various wet
biological tissues including porcine skin, liver, kidney, and heart
and can be changed easily with triggering urea solution to avoid tissue
damage or uncomfortable pain to the patient. This biosafe adhesive
hydrogel is very promising for wound closure and may provide new ideas
for the design of robust wet tissue adhesives
Robust but On-Demand Detachable Wet Tissue Adhesive Hydrogel Enhanced with Modified Tannic Acid
Adhesives with robust but readily detachable wet tissue
adhesion
are of great significance for wound closure. Polyelectrolyte complex
adhesive (PECA) is an important wet tissue adhesive. However, its
relatively weak cohesive and adhesive strength cannot satisfy clinical
applications. Herein, modified tannic acid (mTA) with a catechol group,
a long alkyl hydrophobic chain, and a phenyl group was prepared first,
and then, it was mixed with acrylic acid (AA) and polyethylenimine
(PEI), followed by UV photopolymerization to make a wet tissue adhesive
hydrogel with tough cohesion and adhesion strength. The hydrogel has
a strong wet tissue interfacial toughness of ∼1552 J/m2, good mechanical properties (∼7220 kPa cohesive strength,
∼873% strain, and ∼33,370 kJ/m3 toughness),
and a bursting pressure of ∼1575 mmHg on wet porcine skin.
The hydrogel can realize quick and effective adhesion to various wet
biological tissues including porcine skin, liver, kidney, and heart
and can be changed easily with triggering urea solution to avoid tissue
damage or uncomfortable pain to the patient. This biosafe adhesive
hydrogel is very promising for wound closure and may provide new ideas
for the design of robust wet tissue adhesives
Robust but On-Demand Detachable Wet Tissue Adhesive Hydrogel Enhanced with Modified Tannic Acid
Adhesives with robust but readily detachable wet tissue
adhesion
are of great significance for wound closure. Polyelectrolyte complex
adhesive (PECA) is an important wet tissue adhesive. However, its
relatively weak cohesive and adhesive strength cannot satisfy clinical
applications. Herein, modified tannic acid (mTA) with a catechol group,
a long alkyl hydrophobic chain, and a phenyl group was prepared first,
and then, it was mixed with acrylic acid (AA) and polyethylenimine
(PEI), followed by UV photopolymerization to make a wet tissue adhesive
hydrogel with tough cohesion and adhesion strength. The hydrogel has
a strong wet tissue interfacial toughness of ∼1552 J/m2, good mechanical properties (∼7220 kPa cohesive strength,
∼873% strain, and ∼33,370 kJ/m3 toughness),
and a bursting pressure of ∼1575 mmHg on wet porcine skin.
The hydrogel can realize quick and effective adhesion to various wet
biological tissues including porcine skin, liver, kidney, and heart
and can be changed easily with triggering urea solution to avoid tissue
damage or uncomfortable pain to the patient. This biosafe adhesive
hydrogel is very promising for wound closure and may provide new ideas
for the design of robust wet tissue adhesives
Robust but On-Demand Detachable Wet Tissue Adhesive Hydrogel Enhanced with Modified Tannic Acid
Adhesives with robust but readily detachable wet tissue
adhesion
are of great significance for wound closure. Polyelectrolyte complex
adhesive (PECA) is an important wet tissue adhesive. However, its
relatively weak cohesive and adhesive strength cannot satisfy clinical
applications. Herein, modified tannic acid (mTA) with a catechol group,
a long alkyl hydrophobic chain, and a phenyl group was prepared first,
and then, it was mixed with acrylic acid (AA) and polyethylenimine
(PEI), followed by UV photopolymerization to make a wet tissue adhesive
hydrogel with tough cohesion and adhesion strength. The hydrogel has
a strong wet tissue interfacial toughness of ∼1552 J/m2, good mechanical properties (∼7220 kPa cohesive strength,
∼873% strain, and ∼33,370 kJ/m3 toughness),
and a bursting pressure of ∼1575 mmHg on wet porcine skin.
The hydrogel can realize quick and effective adhesion to various wet
biological tissues including porcine skin, liver, kidney, and heart
and can be changed easily with triggering urea solution to avoid tissue
damage or uncomfortable pain to the patient. This biosafe adhesive
hydrogel is very promising for wound closure and may provide new ideas
for the design of robust wet tissue adhesives
Synthesis of Compositionally Defined Single-Crystalline Eu<sup>3+</sup>-Activated Molybdate–Tungstate Solid-Solution Composite Nanowires and Observation of Charge Transfer in a Novel Class of 1D CaMoO<sub>4</sub>–CaWO<sub>4</sub>:Eu<sup>3+</sup>–0D CdS/CdSe QD Nanoscale Heterostructures
As
a first step, we have synthesized and optically characterized
a systematic series of one-dimensional (1D) single-crystalline Eu<sup>3+</sup>-activated alkaline-earth metal tungstate/molybdate solid-solution
composite CaW<sub>1–<i>x</i></sub>Mo<sub><i>x</i></sub>O<sub>4</sub> (0 ≤ “<i>x</i>” ≤ 1) nanowires of controllable chemical composition
using a modified template-directed methodology under ambient room-temperature
conditions. Extensive characterization of the resulting nanowires
has been performed using X-ray diffraction, electron microscopy, and
optical spectroscopy. The crystallite size and single crystallinity
of as-prepared 1D CaW<sub>1–<i>x</i></sub>Mo<sub><i>x</i></sub>O<sub>4</sub>:Eu<sup>3+</sup> (0 ≤
“<i>x</i>” ≤ 1) solid-solution composite
nanowires increase with increasing Mo component (“<i>x</i>”). We note a clear dependence of luminescence output upon
nanowire chemical composition with our 1D CaW<sub>1–<i>x</i></sub>Mo<sub><i>x</i></sub>O<sub>4</sub>:Eu<sup>3+</sup> (0 ≤ “<i>x</i>” ≤
1) evincing the highest photoluminescence (PL) output at “<i>x</i>” = 0.8, among samples tested. Subsequently, coupled
with either zero-dimensional (0D) CdS or CdSe quantum dots (QDs),
we successfully synthesized and observed charge transfer processes
in 1D CaW<sub>1–<i>x</i></sub>Mo<sub><i>x</i></sub>O<sub>4</sub>:Eu<sup>3+</sup> (“<i>x</i>” = 0.8)–0D QD composite nanoscale heterostructures.
Our results show that CaW<sub>1–<i>x</i></sub>Mo<sub><i>x</i></sub>O<sub>4</sub>:Eu<sup>3+</sup> (“<i>x</i>” = 0.8) nanowires give rise to PL quenching when
CdSe QDs and CdS QDs are anchored onto the surfaces of 1D CaWO<sub>4</sub>–CaMoO<sub>4</sub>:Eu<sup>3+</sup> nanowires. The observed
PL quenching is especially pronounced in CaW<sub>1–<i>x</i></sub>Mo<sub><i>x</i></sub>O<sub>4</sub>:Eu<sup>3+</sup> (“<i>x</i>” = 0.8)–0D CdSe
QD heterostructures. Conversely, the PL output and lifetimes of CdSe
and CdS QDs within these heterostructures are not noticeably altered
as compared with unbound CdSe and CdS QDs. The differences in optical
behavior between 1D Eu<sup>3+</sup> activated tungstate and molybdate
solid-solution nanowires and the semiconducting 0D QDs within our
heterostructures can be correlated with the relative positions of
their conduction and valence energy band levels. We propose that the
PL quenching can be attributed to a photoinduced electron transfer
process from CaW<sub>1–<i>x</i></sub>Mo<sub><i>x</i></sub>O<sub>4</sub>:Eu<sup>3+</sup> (“<i>x</i>” = 0.8) to both CdSe and CdS QDs, an assertion
supported by complementary near edge X-ray absorption fine structure
(NEXAFS) spectroscopy measurements