5 research outputs found
α‑Fe<sub>2</sub>O<sub>3</sub>/NiOOH: An Effective Heterostructure for Photoelectrochemical Water Oxidation
The
study of the semiconductor/electrocatalyst interface in electrodes
for photoelectrochemical water splitting is of paramount importance
to obtain enhanced solar-to-fuel efficiency. Here, we take into consideration
the multiple effects that a thin layer of photodeposited amorphous
Ni-oxyhydroxide (NiOOH) induces on hematite (α-Fe<sub>2</sub>O<sub>3</sub>) photoanodes. The reduction of overpotential produced
a photocurrent onset potential advance of 150 mV and an increase of
photocurrent of about 50% at 1.23 V vs RHE. To give an interpretation
to these phenomena, we carried out deep electrochemical investigations
by cyclic voltammetry and electrochemical impedance spectroscopy.
The effective charge injection into the electrolyte due to the reduction
of the charge transfer resistance at the electrode/electrolyte interface
was observed and increased along with the amount of deposited NiOOH.
The benefits of NiOOH deposition are ascribable to its ability to
scavenge holes from hematite surface traps. This effect is mitigated
at a potential higher than 1.25 V, since a fraction of photogenerated
holes is consumed into the Ni redox cycle
Hierarchical Hematite Nanoplatelets for Photoelectrochemical Water Splitting
A new nanostructured α-Fe<sub>2</sub>O<sub>3</sub> photoelectrode synthesized through plasma-enhanced
chemical vapor deposition (PE-CVD) is presented. The α-Fe<sub>2</sub>O<sub>3</sub> films consist of nanoplatelets with (001) crystallographic
planes strongly oriented perpendicular to the conductive glass surface.
This hematite morphology was never obtained before and is strictly
linked to the method being used for its production. Structural, electronic,
and photocurrent measurements are employed to disclose the nanoscale
features of the photoanodes and their relationships with the generated
photocurrent. α-Fe<sub>2</sub>O<sub>3</sub> films have a hierarchical
morphology consisting of nanobranches (width ∼10 nm, length
∼50 nm) that self-organize in plume-like nanoplatelets (350–700
nm in length). The amount of precursor used in the PE-CVD process
mainly affects the nanoplatelets dimension, the platelets density,
the roughness, and the photoelectrochemical (PEC) activity. The highest
photocurrent (<i>j</i> = 1.39 mA/cm<sup>2</sup> at 1.55
V<sub>RHE</sub>) is shown by the photoanodes with the best balance
between the platelets density and roughness. The so obtained hematite
hierarchical morphology assures good photocurrent performance and
appears to be an ideal platform for the construction of customized
multilayer architecture for PEC water splitting
TiO<sub>2</sub> Nanotubes Arrays Loaded with Ligand-Free Au Nanoparticles: Enhancement in Photocatalytic Activity
A new protocol to
synthesize size-controlled Au nanoparticles (NPs) loaded onto vertically
aligned anatase TiO<sub>2</sub> nanotubes arrays (TNTAs) prepared
by electrochemical anodization is reported. Ligand-free Au NPs (<10
nm) were deposited onto anatase TNTAs supports, finely tuning the
Au loading by controlling the immersion time of the support into metal
vapor synthesis (MVS)-derived Au-acetone solutions. The Au/TNTAs composites
were characterized by electron microscopies (SEM, (S)ÂTEM), X-ray diffraction,
X-ray photoelectron spectroscopy, and UV–vis spectroscopy.
Their photocatalytic efficiency was evaluated in toluene degradation
in air under ambient conditions without thermal or chemical postsynthetic
treatments. The role of Au loadings was pointed out, obtaining a three
times enhancement of the pristine anatase TNTAs activity with the
best sample containing 3.3 μg Au cm<sup>–2</sup>
Effect of Nature and Location of Defects on Bandgap Narrowing in Black TiO<sub>2</sub> Nanoparticles
The increasing need for new materials capable of solar
fuel generation
is central in the development of a green energy economy. In this contribution,
we demonstrate that black TiO<sub>2</sub> nanoparticles obtained through
a one-step reduction/crystallization process exhibit a bandgap of
only 1.85 eV, which matches well with visible light absorption. The
electronic structure of black TiO<sub>2</sub> nanoparticles is determined
by the unique crystalline and defective core/disordered shell morphology.
We introduce new insights that will be useful for the design of nanostructured
photocatalysts for energy applications
Gold Nanoparticles Capped by a GC-Containing Peptide Functionalized with an RGD Motif for Integrin Targeting
Gold nanoparticles were obtained by reduction of a tetrachloroaurate
aqueous solution in the presence of a RGD-(GC)<sub>2</sub> peptide
as stabilizer. As comparison, the behavior of the (GC)<sub>2</sub> peptide has been studied. The (GC)<sub>2</sub> and RGD-(GC)<sub>2</sub> peptides were prepared ad hoc by Fmoc synthesis. The colloidal
systems have been characterized by UV–visible, TGA, ATR-FTIR,
mono and bidimensional NMR techniques, confocal and transmission (TEM)
microscopy, ζ-potential, and light scattering measurements.
The efficient cellular uptake of Au-RGD-(GC)<sub>2</sub> and Au-(GC)<sub>2</sub> stabilized gold nanoparticles into U87 cells (human glioblastoma
cells) were investigated by confocal microscopy and compared with
the behavior of (GC)<sub>2</sub> capped gold nanoparticles. A quantitative
determination of the nanoparticles taken up has been carried out by
measuring the pixel brightness of the images, a measure that highlighted
the importance of the RGD termination of the peptide. Insight in the
cellular uptake mechanism was investigated by TEM microscopy. Various
important evidences indicated the selective uptake of RGD-(GC)<sub>2</sub> gold nanoparticles into the nucleus