19 research outputs found
Correlation between the deleterious effect of parasites on hosts and the relative growth rate (RGR) of host with parasite (a) and without parasite (b), parasitism response of RGR of hosts (c).
<p>Pearson correlation coefficient (<i>r</i>) and <i>p</i>-values are given and values in bold are statistically significant at <i>p</i><0.05.</p
<i>F</i>-values and significance levels of three-way nested ANOVAs of the relative growth rate (RGR) and the resources availability of host plants with fixed factors parasitism (present or absent) and origin (invasive or native), and random factor species pairs (nested with origin).
<p>Values in bold are significant at <i>p</i><0.05; Significance indicated as follows:</p>*<p><i>p</i><0.05,</p>**<p><i>p</i><0.01,</p>***<p><i>p</i><0.001.</p
Means and standard errors of parasites biomass (a) and the deleterious effect of parasites (b) on exotic, invasive species and native, non-invasive species.
<p><i>F</i>-values and significance levels of one-way ANOVA represent the effect of the origin of the species (invasive or native) on the parasites biomass and the deleterious effect of parasites on hosts (<sup>***</sup><i>p</i><0.001;<sup>**</sup><i>p</i><0.01; <sup>*</sup><i>p</i><0.05).</p
Rate-Limiting O–O Bond Formation Pathways for Water Oxidation on Hematite Photoanode
Photoelectrochemical
(PEC) water oxidation has attracted heightened
interest in solar fuel production. It is well accepted that water
oxidation on hematite is mediated by surface trapped holes, characterized
to be the high valent −FeO species. However, the mechanism
of the subsequent rate-limiting O–O bond formation step is
still a missing piece. Herein we investigate the reaction order of
interfacial hole transfer by rate law analysis based on electrochemical
impedance spectroscopy (EIS) measurement and probe the reaction intermediates
by operando Fourier-transform infrared (FT-IR) spectroscopy. Distinct
reaction orders of ∼1 and ∼2 were observed in near-neutral
and highly alkaline environments, respectively. The unity rate law
in near-neutral pH regions suggests a mechanism of water nucleophilic
attack (WNA) to −FeO to form the O–O bond. Operando
observation of a surface superoxide species that hydrogen bonded to
the adjacent hydroxyl group by FT-IR further confirmed this pathway.
In highly alkaline regions, coupling of adjacent surface trapped holes
(I2M) becomes the dominant mechanism. While both are operable at intermediate
pHs, mechanism switch from I2M to WNA induced by local pH decrease
was observed at high photocurrent level. Our results highlight the
significant impact of surface protonation on O–O bond formation
pathways and oxygen evolution kinetics on hematite surfaces
Trace-Level Potentiometric Detection in the Presence of a High Electrolyte Background
Polymeric membrane ion-selective electrodes (ISEs) have
become
attractive tools for trace-level environmental and biological measurements.
However, applications of such ISEs are often limited to measurements
with low levels of electrolyte background. This paper describes an
asymmetric membrane rotating ISE configuration for trace-level potentiometric
detection with a high-interfering background. The membrane electrode
is conditioned in a solution of interfering ions (e.g., Na<sup>+</sup>) so that no primary ions exist in the ISE membrane, thus avoiding
the ion-exchange effect induced by high levels of interfering ones
in the sample. When the electrode is in contact with the primary ions,
the interfering ions in the membrane surface can be partially displaced
by the primary ions due to the favorable ion–ligand interaction
with the ionophore in the membrane, thus causing a steady-state potential
response. By using the asymmetric membrane with an ion exchanger loaded
on the membrane surface, the diffusion of the primary ions from the
organic boundary layer into the bulk of the membrane can be effectively
blocked; on the other hand, rotation of the membrane electrode dramatically
reduces the diffusion layer thickness of the aqueous phase and significantly
promotes the mass transfer of the primary ions to the sample–membrane
interface. The induced accumulation of the primary ions in the membrane
boundary layer largely enhances the nonequilibrium potential response.
By using copper as a model, the new concept offers a subnanomolar
detection limit for potentiometric measurements of heavy metals with
a high electrolyte background of 0.5 M NaCl
miR-29b-Loaded Gold Nanoparticles Targeting to the Endoplasmic Reticulum for Synergistic Promotion of Osteogenic Differentiation
Precise
control of stem cells, such as human bone marrow-derived mesenchymal
stem cells (hMSCs), is critical for the development of effective cellular
therapies for tissue engineering and regeneration medicine. Emerging
evidence suggests that several miRNAs act as key regulators of diverse
biological processes, including differentiation of various stem cells.
In this study, we have described a delivery system for miR-29b using
PEI-capped gold nanoparticles (AuNPs) to synergistically promote osteoblastic
differentiation. The cell proliferation assay revealed that AuNPs
and AuNPs/miR-29b exert negligible cytotoxicity to hMSCs and MC3T3-E1
cells. With the assistance of AuNPs as a delivery vector, miR-29b
could efficiently enter the cytoplasm and regulate osteogenesis. AuNPs/miR-29b
more effectively promoted osteoblast differentiation and mineralization
through induced the expression of osteogenesis genes (RUNX2, OPN,
OCN, ALP) for the long-term, compared to the widely used commercial
transfection reagent, Lipofectamine. With no obvious cytotoxicity,
PEI-capped AuNPs showed great potential as an adequate miRNA vector
for osteogenesis differentiation. Interestingly, we observed loading
of AuNPs as well as AuNPs/miR-29b into the lumen of the endoplasmic
reticulum (ER). Our findings collectively suggest that AuNPs, together
with miR-29b, exert a synergistic promotory effect on osteogenic differentiation
of hMSCs and MC3T3-E1 cells
Fabrication of 3D Porous Hierarchical NiMoS Flowerlike Architectures for Hydrodesulfurization Applications
Layered
transition-metal sulfides such as MoS<sub>2</sub> often
show a range of intriguing electronic, catalytic, and optical properties.
Because of their high surface energy, layered materials generally
tend to stack and prevent the exposure of additional edge sites. Here,
we demonstrate a facile approach for the preparation of hierarchical
NiMoS nanoflowers via SiO<sub>2</sub>-assisted hydrothermal synthesis.
The structure and morphology of the nanomaterials are characterized
by scanning electron microscopy, transmission electron microscopy,
X-ray diffraction, Raman, and X-ray photoelectron spectroscopy analyses,
revealing that different sizes of NiMoS nanoflowers assembled from
various nanosheet thicknesses can be tuned by modifying the Si/Mo
molar ratio. The key aspect of this strategy is to construct the three-dimensional
nanostructures around the SiO<sub>2</sub> nanospheres while maintaining
a flowerlike feature. The correlation between the nanosheet thickness,
surface area, and total dispersion of the Mo atoms indicated that
the large quantity and efficient accessibility of NiMoS active sites
originating from the synergistically multiscale structure and atom-scale
modulations between MoS<sub>2</sub> and Ni atoms are the determining
factors for the observed impressive hydrodesulfurization performance
and the stable recyclability of these materials
Hydrogen-Bond Bridged Water Oxidation on {001} Surfaces of Anatase TiO<sub>2</sub>
To gain an atomic-level understanding of the relationship among the
surface structure, the interfacial interaction, and the water oxidation
activity on TiO<sub>2</sub>, we studied the adsorption of water and
its photocatalytic oxidation on anatase TiO<sub>2</sub> with {101}
and {001} exposed surfaces by in situ infrared spectroscopy, kinetic
isotope effect studies, and density functional theory (DFT)-based
molecular dynamics calculations. Our experimental results demonstrate
that the oxidation reaction occurs exclusively on hydrogen-bonded
water molecules (via surface hydroxyls) over {001} surface, whereas
water molecules coordinated on the {101} surface, which are conventionally
assigned to the reactive target for hole transfer, remain unchanged
during the irradiation. The theoretical calculations reveal that the
selective oxidation of water adsorbed on the {001} surfaces is primarily
attributed to the formation of hydrogen bonds, which provides a channel
to the rapid hole transfer and facilitates the O–H bond cleavage
during water oxidation
Photoinduced Stepwise Oxidative Activation of a Chromophore–Catalyst Assembly on TiO<sub>2</sub>
To probe light-induced redox equivalent separation and accumulation, we prepared ruthenium polypyridyl molecular assembly [(dcb)<sub>2</sub>Ru(bpy-Mebim<sub>2</sub>py)Ru(bpy)(OH<sub>2</sub>)]<sup>4+</sup> (Ru<sub>a</sub><sup>II</sup>–Ru<sub>b</sub><sup>II</sup>–OH<sub>2</sub>) with Ru<sub>a</sub> as light-harvesting chromophore and Ru<sub>b</sub> as water oxidation catalyst (dcb = 4,4′-dicarboxylic acid-2,2′-bipyridine; bpy-Mebim<sub>2</sub>py = 2,2′-(4-methyl-[2,2′:4′,4″-terpyridine]-2″,6″-diyl)bis(1-methyl-1H-benzo[<i>d</i>]imidazole); bpy = 2,2′-bipyridine). When bound to TiO<sub>2</sub> in nanoparticle films, it undergoes MLCT excitation, electron injection, and oxidation of the remote −Ru<sub>b</sub><sup>II</sup>–OH<sub>2</sub> site to give TiO<sub>2</sub>(e<sup>–</sup>)–Ru<sub>a</sub><sup>II</sup>–Ru<sub>b</sub><sup>III</sup>–OH<sub>2</sub><sup>3+</sup> as a redox-separated transient. The oxidized assembly, TiO<sub>2</sub>–Ru<sub>a</sub><sup>II</sup>–Ru<sub>b</sub><sup>III</sup>–OH<sub>2</sub><sup>3+</sup>, similarly undergoes excitation and electron injection to give TiO<sub>2</sub>(e<sup>–</sup>)–Ru<sub>a</sub><sup>II</sup>–Ru<sub>b</sub><sup>IV</sup>O<sup>2+</sup>, with Ru<sub>b</sub><sup>IV</sup>O<sup>2+</sup> a known water oxidation catalyst precursor. Injection efficiencies for both forms of the assembly are lower than those for [Ru(bpy)<sub>2</sub>(4,4′-(PO<sub>3</sub>H<sub>2</sub>)<sub>2</sub>bpy)]<sup>2+</sup> bound to TiO<sub>2</sub> (TiO<sub>2</sub>–Ru<sup>2+</sup>), whereas the rates of back electron transfer, TiO<sub>2</sub>(e<sup>–</sup>) → Ru<sub>b</sub><sup>III</sup>–OH<sub>2</sub><sup>3+</sup> and TiO<sub>2</sub>(e<sup>–</sup>) → Ru<sub>b</sub><sup>IV</sup>O<sup>2+</sup>, are significantly decreased compared with TiO<sub>2</sub>(e<sup>–</sup>) → Ru<sup>3+</sup> back electron transfer
Self-Assembled Bilayers on Indium–Tin Oxide (SAB-ITO) Electrodes: A Design for Chromophore–Catalyst Photoanodes
A novel approach for creating assemblies on metal oxide
surfaces
via the addition of a catalyst overlayer on a chomophore monolayer
derivatized surface is described. It is based on the sequential self-assembly
of a chromophore, [RuÂ(bpy)Â(4,4′-(PO<sub>3</sub>H<sub>2</sub>bpy)<sub>2</sub>)]<sup>2+</sup>, and oxidation catalyst, [RuÂ(bpy)Â(P<sub>2</sub>Mebim<sub>2</sub>py)ÂOH<sub>2</sub>]<sup>2+</sup>, pair, resulting
in a spatially separated chromophore–catalyst assembly