5 research outputs found
Optical Interference-Free Surface-Enhanced Raman Scattering CO-Nanotags for Logical Multiplex Detection of Vascular Disease-Related Biomarkers
Matrix metalloproteinases (MMPs),
specifically MMP-2, MMP-7, and
MMP-9, have been discovered to be linked to many forms of vascular
diseases such as stroke, and their detection is crucial to facilitate
clinical diagnosis. In this work, we prepared a class of optical interference-free
SERS nanotags (CO-nanotags) that can be used for the purpose of multiplex
sensing of different MMPs. Multiplex detection with the absence of
cross-talk was achieved by using CO-nanotags with individual tunable
intrinsic Raman shifts of CO in the 1800ā2200 cm<sup>ā1</sup> region determined by the metal core and ligands of the metal carbonyl
complex. Boolean logic was used as well to simultaneously probe for
two proteolytic inputs. Such nanotags offer the advantages of convenient
detection of target nanotags and high sensitivity as validated in
the ischemia rat model
Facile Synthesis of [101]-Oriented Rutile TiO<sub>2</sub> Nanorod Array on FTO Substrate with a Tunable AnataseāRutile Heterojunction for Efficient Solar Water Splitting
Generating
a sustainable energy source through photoelectrochemical
(PEC) water splitting requires a suitable photocatalyst. A [101]-oriented
rutile TiO<sub>2</sub> nanorod (NR) array in heterojunction with anatase
on a fluorine-doped tin oxide (FTO) substrate is successfully prepared
using a facile single-step hydrothermal process. The presence of anatase
phase over the predominant rutile NRsā surface is confirmed
by transmission electron microscopy and tip-enhanced Raman spectroscopy.
Solar water-splitting performances of anataseārutile heterojunction
with low energy (101) and high energy (001) rutile facets are compared.
The low energy (101) facet rutileāanatase heterojunction shows
higher photoconversion efficiency of 1.39% at 0.49 V<sub>RHE</sub> than the high energy (001) facet rutileāanatase heterojunction
(0.37% at 0.73 V<sub>RHE</sub>). The mechanism for enhanced photocatalytic
activity of the low energy (101) facet rutileāanatase heterojunction
has been proposed. The role of NaCl in tuning the anatase portion,
morphology, and PEC water-splitting performance has also been studied
Self-Assembled Chiral Gold Supramolecules with Efficient Laser Absorption for Enantiospecific Recognition of Carnitine
Stereospecific recognition of chiral
molecules is ubiquitous in
chemical and biological systems, thus leading to strong demand for
the development of enantiomeric drugs, enantioselective sensors, and
asymmetric catalysts. In this study, we demonstrate the ratio of d-Cys and l-Cys playing an important role in determining the
optical properties and the structures of self-assembled CysāAuĀ(I)
supramolecules prepared through a simple reaction of tetrachloroaurateĀ(III)
with chiral cysteine (Cys). The irregularly shaped ā[d-CysāAuĀ(I)]<sub><i>n</i></sub>ā or ā
[l-CysāAuĀ(I)]<sub><i>n</i></sub>ā
supramolecules with a size larger than 500 nm possessing strong absorption
in the near-UV region and chiroptical characteristics were only obtained
from the reaction of AuĀ(III) with d-Cys or l-Cys.
On the other hand, spindle-shaped ā[d/l-CysāAuĀ(I)]<sub><i>n</i></sub>ā supramolecules were formed when
using AuĀ(III) with mixtures of d/l-Cys. Our results
have suggested that AuĀ(I)Ā·Ā·Ā·AuĀ(I) aurophilic interactions,
and stacked hydrogen bonding and zwitterionic interactions between d/l-Cys ligands are important in determining their
structures. The NaBH<sub>4</sub>-mediated reduction induces the formation
of photoluminescent gold nanoclusters (Au NCs) embedded in the chiral
ā[d-CysāAuĀ(I)]<sub><i>n</i></sub>ā or ā[l-CysāAuĀ(I)]<sub><i>n</i></sub>ā supramolecules with a quantum yield of ca. 10%. The
as-formed Au NCs/ā[d-CysāAuĀ(I)]<sub><i>n</i></sub>ā and Au NCs/ā[l-CysāAuĀ(I)]<sub><i>n</i></sub>ā are an enantiospecific substrate
that can trap l-carnitine and d-carnitine, respectively,
and function as a nanomatrix for surface-assisted laser desorption/ionization
mass spectrometry (LDI-MS). The high absorption efficiency of laser
energy, analyte-binding capacity, and homogeneity of the Au NCs/ā[CysāAuĀ(I)]<sub><i>n</i></sub>ā allow for quantitation of enantiomeric
carnitine down to the micromolar regime with high reproducibility.
The superior efficiency of the Au NCs/ā[d-CysāAuĀ(I)]<sub><i>n</i></sub>ā substrate has been further validated
by quantification of l-carnitine in dietary supplements with
accuracy and precision. Our study has opened a new avenue for chiral
quantitation of various analytes through LDI-MS using metal nanocomposites
consisting of NCs and metalāligand complexes
Simple Replacement Reaction for the Preparation of Ternary Fe<sub>1ā<i>x</i></sub>PtRu<sub><i>x</i></sub> Nanocrystals with Superior Catalytic Activity in Methanol Oxidation Reaction
The finding of new metal alloyed nanocrystals (NCs) with
high catalytic
activity and low cost to replace PtRu NCs is a critical step toward
the commercialization of fuel cells. In this work, a simple cation
replacement reaction was utilized to synthesize a new type of ternary
Fe<sub>1ā<i>x</i></sub>PtRu<sub><i>x</i></sub> NCs from binary FePt NCs. The detailed structural transformation
from binary FePt NCs to ternary Fe<sub>1ā<i>x</i></sub>PtRu<sub><i>x</i></sub> NCs was analyzed by X-ray
absorption spectroscopy (XAS). Ternary Fe<sub>35</sub>Pt<sub>40</sub>Ru<sub>25</sub>, Fe<sub>31</sub>Pt<sub>40</sub>Ru<sub>29</sub>, and
Fe<sub>17</sub>Pt<sub>40</sub>Ru<sub>43</sub> NCs exhibit superior
catalytic ability to withstand CO poisoning in methanol oxidation
reaction (MOR) than do binary NCs (FePt and J-M PtRu). Also, the Fe<sub>31</sub>Pt<sub>40</sub>Ru<sub>29</sub> NCs had the highest alloying
extent and the lowest onset potential among the ternary NCs. Furthermore,
the origin for the superior CO resistance of ternary Fe<sub>1ā<i>x</i></sub>PtRu<sub><i>x</i></sub> NCs was investigated
by determining the adsorption energy of CO on the NCsā surfaces
and the charge transfer from Fe/Ru to Pt using a simulation based
on density functional theory. The simulation results suggested that
by introducing a new metal into binary PtRu/PtFe NCs, the anti-CO
poisoning ability of ternary Fe<sub>1ā<i>x</i></sub>PtRu<sub><i>x</i></sub> NCs was greatly enhanced because
the bonding of COāPt on the NCsā surface was weakened.
Overall, our experimental and simulation results have indicated a
simple route for the discovery of new metal alloyed catalysts with
superior anti-CO poisoning ability and low usage of Pt and Ru for
fuel cell applications
Unraveling the Structure of Magic-Size (CdSe)<sub>13</sub> Cluster Pairs
Cadmium selenide
is a IIāVI semiconductor model system known
for its nanoparticle preparation, growth mechanism, luminescence properties,
and quantum confinement studies. For the past 2 decades, various thermodynamically
stable āmagic-size nanoclusters (MSCs)ā of CdSe have
been observed, isolated, and theoretically calculated. Nevertheless,
none of the proposed structures were experimentally confirmed due
to the small crystal domains beyond the diffraction limit. With a
combination of nondestructive SAXS, WAXS, XRD, XPS, EXAFS, and MAS
NMR techniques, we were able to verify the phase transformation, shape,
size dimension, local bonding, and chemical environments of (CdSe)<sub>13</sub> nanoclusters, which are indicative of a paired cluster model.
These experimental results are consistent with the size, shape, bond
lengths, dipole moment, and charge densities of the proposed āpaired-tubular
geometryā predicted by computational approaches. In this article,
we revisit the formation pathway of the mysterious (CdSe)<sub>13</sub> nanoclusters and propose a paired cluster structure model for better
understanding of IIāVI semiconductor nanoclusters