4 research outputs found
Hierarchically Driven IrO<sub>2</sub> Nanowire Electrocatalysts for Direct Sensing of Biomolecules
Applying nanoscale device fabrications toward biomolecules,
ultra
sensitive, selective, robust, and reliable chemical or biological
microsensors have been one of the most fascinating research directions
in our life science. Here we introduce hierarchically driven iridium
dioxide (IrO<sub>2</sub>) nanowires directly on a platinum (Pt) microwire,
which allows a simple fabrication of the amperometric sensor and shows
a favorable electronic property desired for sensing of hydrogen peroxide
(H<sub>2</sub>O<sub>2</sub>) and dihydronicotinamide adenine dinucleotide
(NADH) without the aid of enzymes. This rational engineering of a
nanoscale architecture based on the direct formation of the hierarchical
1-dimensional (1-D) nanostructures on an electrode can offer a useful
platform for high-performance electrochemical biosensors, enabling
the efficient, ultrasensitive detection of biologically important
molecules
Conformer-Specific and Diastereomer-Specific Spectroscopy of <i>αβα</i> Synthetic Foldamers: Ac–Ala−β<sub>ACHC</sub>–Ala–NHBn
The folding propensities
of a capped, cyclically constrained, mixed <i>α/β</i> diastereomer pair, (<i>SRSS)</i> Ac–Ala−β<sub>ACHC</sub>–Ala–NHBn
(hereafter <i>RS</i>) and (<i>SSRS)</i> Ac–Ala−β<sub>ACHC</sub>–Ala–NHBn (<i>SR</i>), have been
studied in a molecular beam using single-conformation spectroscopic
techniques. These <i>α/β</i>-tripeptides contain
a cyclohexane ring across each C<sub>α</sub><i>–</i>C<sub>β</sub> bond, at which positions their stereochemistries
differ. This cyclic constraint requires any stable species to adopt
one of two ACHC configurations: equatorial CO/axial NH or
equatorial NH/axial CO. Resonant two-photon ionization (R2PI)
and infrared–ultraviolet hole-burning (IR–UV HB) spectroscopy
were used in the S<sub>0</sub>–S<sub>1</sub> region of the
UV chromophore, revealing the presence of three unique conformational
isomers of <i>RS</i> and two of <i>SR</i>. Resonant
ion-dip infrared spectra were recorded in both the NH stretch (3200–3500
cm<sup>–1</sup>) and the amide I (1600–1800 cm<sup>–1</sup>) regions. These experimental vibrational frequencies were compared
with the scaled calculated normal-mode frequencies from density functional
theory at the M05-2X/6-31+G(d) level of theory, leading to structural
assignments of the observed conformations. The <i>RS</i> diastereomer is known in crystalline form to preferentially form
a C11/C9 mixed helix, in which alternating hydrogen bonds are arranged
in near antiparallel orientation. This structure is preserved in one
of the main conformers observed in the gas phase but is in competition
with both a tightly folded C7<sub>eq</sub>/C12/C8/C7<sub>eq</sub> structure,
in which all four amide NH groups and four CO groups are engaged
in hydrogen bonding, as well as a cap influenced C7<sub>eq</sub>/NH···π/C11
structure. The <i>SR</i> diastereomer is destabilized by
inducing backbone dihedral angles that lie outside the typical Ramachandran
angles. This diastereomer also forms a C11/C9 mixed helix as well
as a cap influenced bifurcated C7<sub>ax</sub>–C11/NH···π/C7<sub>eq</sub> structure as the global energy minimum. Assigned structures
are compared with the reported crystal structure of analogous <i>α/β</i>-tripeptides, and disconnectivity graphs
are presented to give an overview of the complicated potential energy
surface of this tripeptide diastereomer pair
Synthesis of Monoclinic Potassium Niobate Nanowires That Are Stable at Room Temperature
We report the synthesis of KNbO<sub>3</sub> nanowires
(NWs) with
a monoclinic phase, a phase not observed in bulk KNbO<sub>3</sub> materials.
The monoclinic NWs can be synthesized via a hydrothermal method using
metallic Nb as a precursor. The NWs are metastable, and thermal treatment
at ∼450 °C changed the monoclinic phase into the orthorhombic
phase, which is the most stable phase of KNbO<sub>3</sub> at room
temperature. Furthermore, we fabricated energy-harvesting nanogenerators
by vertically aligning the NWs on SrTiO<sub>3</sub> substrates. The
monoclinic NWs showed significantly better energy conversion characteristics
than orthorhombic NWs. Moreover, the frequency-doubling efficiency
of the monoclinic NWs was ∼3 times higher than that of orthorhombic
NWs. This work may contribute to the synthesis of materials with new
crystalline structures and hence improve the properties of the materials
for various applications
Additional file 1: of Performance comparison of first-order conditional estimation with interaction and Bayesian estimation methods for estimating the population parameters and its distribution from data sets with a low number of subjects
rRMSE plot for THEO data set. Relative root mean square error (rRMSE) of fixed-effect and random-effect parameters from THEO data set using FOCE-I (●), BAYES(C) (▲), BAYES(F) (■) and BAYES (┼) estimation methods. (PDF 6 kb