10 research outputs found
Structure and Properties of Water on the Anatase TiO<sub>2</sub>(101) Surface: From Single-Molecule Adsorption to Interface Formation
The interaction of water with titanium dioxide surfaces
has a vital
role in many energy- and environment-related applications, such as
dye-sensitized solar cell, photocatalytic or photoelectrochemical
hydrogen production, and environmental purification. Structure and
properties of water on the anatase TiO<sub>2</sub>(101) surface have
been studied by using a combination of density functional theory and
force field molecular dynamics. Owing to the amphotericity of this
surface and the competition between waterâwater and waterâsubstrate
interactions, the structure and properties
of water on the anatase TiO<sub>2</sub>(101) surface exhibited some
peculiar and complicated features. The overall evolutionary process
of interface formation has been obtained by investigating the coverage-dependent
adsorption configuration and energy of water. The competition between
waterâwater
and waterâsubstrate interaction results in the existence
of a stable bilayer of water (Î â„ 2 ML) and an ice-like
structure of water at higher coverage (Î â„ 3 ML). Both
static and dynamic calculation results have showed that a highly ordered
structure occurs in the first few water molecule layers, and this
order decreases as one moves toward the bulk region. The electric
fields across the interface and in the electric double layer were
estimated to be about 10 and 2 eV, respectively. This study may provide
new insight into the static and dynamic properties of the waterâTiO<sub>2</sub> interface and elucidate the reactions that occur on the TiO<sub>2</sub> surface
Back Electron Transfer at TiO<sub>2</sub> Nanotube Photoanodes in the Presence of a H<sub>2</sub>O<sub>2</sub> Hole Scavenger
Adding
charge scavengers, which usually are more unstable than water, is
an effective method to quantify the quantum efficiency loss of photoelectrode
during the charge separation, transfer, and injection processes of
the water splitting reaction. Here, we detected, on TiO<sub>2</sub> nanotube photoanodes after using hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) as a hole scavenger, a nearly 40% saturated photocurrent
decrease in alkaline electrolyte and a negligible saturated photocurrent
difference in acid electrolyte. We found that the photoelectrons were
trapped in the surface states of TiO<sub>2</sub> with nearly the same
storage capacity of electrons in a wide range of pH values from 1.0
to 13.6. However, kinetics of a back reaction, H<sub>2</sub>O<sub>2</sub> reduction by the photoelectrons trapped in surface states,
is about 10 times higher for that in alkaline electrolyte than in
acid electrolyte. As a result, the pH-dependent kinetic difference
in H<sub>2</sub>O<sub>2</sub> reduction induced the negative effects
on the saturated photocurrent. Our results offer a new insight into
understanding the effects of back electron transfer on electrochemical
behaviors of surface states and charge scavengers
Theoretical Insight into Charge-Recombination Center in Ta<sub>3</sub>N<sub>5</sub> Photocatalyst: Interstitial Hydrogen
Ideal
Ta<sub>3</sub>N<sub>5</sub> is a promising candidate photocatalyst
for solar water splitting. In a common synthetic route, both oxygen
and hydrogen impurities are inevitably formed during the nitridation
of TaO<sub><i>x</i></sub> precursor by ammonia. The introduced
hydrogen impurities would bond with oxygen in the form of hydroxyl
groups, resulting in additional bands bracketing band edges. This
configuration adds Ta<sub>3</sub>N<sub>5</sub> electronâhole
recombination centers, leading to a high onset potential. Hydrogen
impurities would also introduce hydrogen bonds which aggravate charge
recombination by additional charge transport paths from anions to
hydroxyl recombination centers. In addition, hydride ions of hydroxyl
groups may be activated into protons at high bias and may relay hole
transport in Ta<sub>3</sub>N<sub>5</sub>, endowing the material with
high saturated photocurrent. In summary, hydrogen impurities would
aggravate the onset potential of Ta<sub>3</sub>N<sub>5</sub> in the
way of high electronâhole recombination. More broadly, hydrogen
impurities may be common in (oxy)Ânitrides and other covalent materials;
they may add to the photocatalystsâ high onset potential via
electron localizations and might introduce high charge recombination
for covalent semiconductors
Oxygen-Impurity-Induced DirectâIndirect Band Gap in Perovskite SrTaO<sub>2</sub>N
Oxynitride
semiconductors are considered to be promising candidates
for solar water splitting. In this work, we show that oxygen-rich
SrTaO<sub>2</sub>N has a band gap with directâindirect character
through twin valence-band maximums (VBMs), resulting in good photoelectronic
responses. Compared with the direct band gap of ideal SrTaO<sub>2</sub>N, the additional indirect VBM of the oxygen-rich solid solution
was found to be due to strontiumâoxygen hybridization, using
orbital projections based on hybrid/GW density functional theory (DFT).
This twin-VBM character was validated by strontium K-edge absorption
through extended X-ray absorption fine structure (EXAFS) analysis.
The twin-VBM character of the band structure can enhance the photoelectronic
response and hole transport. Our findings provide a viable strategy
for enhancing the solar water splitting performance of oxynitrides
Study on the Ambient Temperature as an Important but Easily Neglected Factor in the Process of Preparing Photovoltaic All-Inorganic CsPbIBr<sub>2</sub> Perovskite Film by the Elegant Solvent-Controlled Growth Strategy
All-inorganic CsPbIBr2 perovskite has received
extensive
attention in the field of solar cells due to its good wet and thermal
stability as well as a moderate band gap. In the preparation of CsPbIBr2 film by one-step spin-coating method, the amount of dimethyl
sulfoxide solvent remaining in the precursor film has a great influence
on the process of film growth. Therefore, it is necessary to ensure
that an appropriate amount of solvent exists in the precursor film
before annealing. Herein, we adopted the solvent-controlled growth
(SCG) strategy, that is, standing by the precursor films in the nitrogen
glovebox for a period of time before annealing, to make sure that
excess solvent can be evaporated from the precursor film. In this
work, we found that the ambient temperature is an important but easily
neglected factor in the process of preparing CsPbIBr2 film
by the SCG strategy. When the ambient temperature is 20 °C, SCG
treatment is required to obtain a flat and dense CsPbIBr2 film. However, SCG treatment is not essential at 30 °C. The
ambient temperature has an impact on the evaporation rate of the solvent
in the precursor film, and thus affects the effect of the SCG strategy.
This work highlights that, when preparing CsPbIBr2 film
by a one-step spin-coating method, in order to obtain a high-quality
CsPbIBr2 film, the influence of ambient temperature on
solvent-controlled growth strategy should be considered
Formation of Hierarchical Structure Composed of (Co/Ni)Mn-LDH Nanosheets on MWCNT Backbones for Efficient Electrocatalytic Water Oxidation
Active,
stable, and cost-effective electrocatalysts are attractive
alternatives to the noble metal oxides that have been used in water
splitting. The direct nucleation and growth of electrochemically active
LDH materials on chemically modified MWCNTs exhibit considerable electrocatalytic
activity toward oxygen evolution from water oxidation. CoMn-based
and NiMn-based hybrids were synthesized using a facile chemical bath
deposition method and the as-synthesized materials exhibited three-dimensional
hierarchical configurations with tunable Co/Mn and Ni/Mn ratio. Benefiting
from enhanced electrical conductivity with MWCNT backbones and LDH
lamellar structure, the Co<sub>5</sub>Mn-LDH/MWCNT and Ni<sub>5</sub>Mn-LDH/MWCNT could generated a current density of 10 mA cm<sup>â2</sup> at overpotentials of âŒ300 and âŒ350 mV, respectively,
in 1 M KOH. In addition, the materials also exhibited outstanding
long-term electrocatalytic stability
Modified Solvothermal Strategy for Straightforward Synthesis of Cubic NaNbO<sub>3</sub> Nanowires with Enhanced Photocatalytic H<sub>2</sub> Evolution
To further improve the photocatalytic
H<sub>2</sub> evolution activity, NaNbO<sub>3</sub> photocatalyts
simultaneously possessing cubic crystal structure and 1D morphology
have been successfully synthesized via a modified solvothermal strategy.
During the process of synthesis employing ethylene glycol as solvent,
a temperature fluctuation during the autoclaving period is proposed
to regulate the grain growth without any other additives or calcinations.
It is demonstrated that the structure-directing effect of the solvent
is enhanced in the condition of the temperature fluctuation, contributing
to the formation of 1D nanostructure. Otherwise, the irregular NaNbO<sub>3</sub> nanoparticles with severe aggregation resulted. Photocatalytic
H<sub>2</sub> evolution activities of samples under ultraviolet light
irradiation with 0.5 wt % of Pt cocatalyst indicate that NaNbO<sub>3</sub> nanowires expectedly exhibit an enhanced activity of 699
ÎŒmol h<sup>â1</sup> g<sup>â1</sup>, approaching
twice that of NaNbO<sub>3</sub> nanoparticles. The higher photocatalytic
activity of NaNbO<sub>3</sub> nanowires is attributed to their large
specific surface area, high chemical purity, and powerful reduction
ability, which have been confirmed by the further characterizations
and analysis based on crystal structure, valence state, elemental
composition, and energy band structure. The modified solvothermal
strategy provides an alternative pathway to regulate the crystal growth,
which can effectively integrate the unique morphology with desired
crystalline structure toward increasing photocatalytic activity
Enhanced Performance of Photoelectrochemical Water Splitting with ITO@α-Fe<sub>2</sub>O<sub>3</sub> CoreâShell Nanowire Array as Photoanode
Hematite
(α-Fe<sub>2</sub>O<sub>3</sub>) is one of the most
promising candidates for photoelectrodes in photoelectrochemical water
splitting system. However, the low visible light absorption coefficient
and short hole diffusion length of pure α-Fe<sub>2</sub>O<sub>3</sub> limits the performance of α-Fe<sub>2</sub>O<sub>3</sub> photoelectrodes in water splitting. Herein, to overcome these drawbacks,
single-crystalline tin-doped indium oxide (ITO) nanowire core and
α-Fe<sub>2</sub>O<sub>3</sub> nanocrystal shell (ITO@α-Fe<sub>2</sub>O<sub>3</sub>) electrodes were fabricated by covering the
chemical vapor deposited ITO nanowire array with compact thin α-Fe<sub>2</sub>O<sub>3</sub> nanocrystal film using chemical bath deposition
(CBD) method. The <i>J</i>â<i>V</i> curves
and IPCE of ITO@α-Fe<sub>2</sub>O<sub>3</sub> coreâshell
nanowire array electrode showed nearly twice as high performance as
those of the α-Fe<sub>2</sub>O<sub>3</sub> on planar Pt-coated
silicon wafers (Pt/Si) and on planar ITO substrates, which was considered
to be attributed to more efficient hole collection and more loading
of α-Fe<sub>2</sub>O<sub>3</sub> nanocrystals in the coreâshell
structure than planar structure. Electrochemical impedance spectra
(EIS) characterization demonstrated a low interface resistance between
α-Fe<sub>2</sub>O<sub>3</sub> and ITO nanowire arrays, which
benefits from the well contact between the core and shell. The stability
test indicated that the prepared ITO@α-Fe<sub>2</sub>O<sub>3</sub> coreâshell nanowire array electrode was stable under AM1.5
illumination during the test period of 40âŻ000 s
Additional file 1: Figure S1. of PKM2 regulates neural invasion of and predicts poor prognosis for human hilar cholangiocarcinoma
PKM2 expression in HC tissues. A, Western blotting revealed the expression pattern of KK1, PFKB, and PKM2 in HC (T) and matched adjacent noncancerous normal tissue (N) (A). B, Graphical representation of the different expressions of KK1, PFKB, and PKM2 between N and T from (A) using Image J. C, Western blotting showed higher expressions of PKM2 in tumor (âTâ) than normal (âNâ) in another three cases of HC. Figure S2. PFKB expression and HC patient survival. Kaplan-Meier survival curves for patients with HC according to expression of PFKB. DFS (A) and OS (B) did not differ significantly between HC patients with low or high PFKB expression. Cum, cumulative. Figure S3. Subgroup survival analysis of PKM2 expression in HC patients according to TNM category. A, patients with stage I or II HC and high PKM2 expression had a shorter median time to recurrence than did those with stage I or II HC but without PKM2 overexpression. B, patients with stage III or IV HC and high PKM2 expression had a significantly shorter median time to recurrence than did patients with stage III or IV HC but with low PKM2 expression. C, the median OS duration was significantly worse in patients with stage I or II HC and PKM2 expression than in those with stage I or II HC but with low PKM2 expression. D, the median OS duration was significantly worse in patients with stage III or IV HC and PKM2 expression than in those with stage III or IV HC but with low PKM2 expression. Cum, cumulative. Figure S4. Representative MS/MS spectrum showing the peptide of PKM2 protein. A, the intensity of repots ions of precursor peptides indicating protein expression levels. N, normal bile duct tissue. B, MS/MS spectra demonstrating identified sequences of the peptide LAPITSDPTEATAVGAVEASFK leading to identification of PKM2. Figure S5. Localization of PKM2 expression in HC cells. A and B, cytoplasmic staining for PKM2 in well/moderately differentiated cancer cells. C and D, cytoplasmic and nuclear staining (arrow) for PKM2 in poorly differentiated cancer cells. Figure S6. Xenograft models of HC. A and B, tumor cells were treated with either control shRNA or PKM2 shRNA and orthotopically implanted into nude mice as described in Materials and Methods. Tumor cells with high PKM2 expression had a higher frequency of lymph node metastasis and liver lesions than did cells with low PKM2 expression (red arrows). C, tumors with downregulated PKM2 expression had lower SDC2 expression than did those with high PKM2 expression. Figure S7. Kaplan-Meier survival curves for patients with HC according to SDC2 expression. A, patients with high SDC2-expressing tumors had a shorter median DFS duration than did patients with low SDC2-expressing tumors. B, the median OS duration in patients with high SDC2 expression did not differ significantly from that in patients with low SDC2 expression. Cum, cumulative. Figure S8. Effect of metformin treatment on tumor cell growth. A, Metformin inhibited the ability of cell proliferation of RBE cells in vitro as determined by using the CCK8 assay. B, Representative photos of HC protein staining positivity and expression pattern of IHC staining were presented. (PPTX 6948 kb
Additional file 2: Table S1. of PKM2 regulates neural invasion of and predicts poor prognosis for human hilar cholangiocarcinoma
Association between expression of PKM2, PFKB, and HK1 and clinical variables in HC patients. Table S2. Multivariate analysis of variables associated with TTP and OS in HC patients. Table S3. Multivariate analysis of variables associated with OS in HC patients. Table S4. Correlation of SDC2 expression and clinicopathological factors in HC patients. Table S5. Correlation between PKM2 protein overexpression and SDC2 protein overexpression in HC patients. (DOCX 40 kb