7 research outputs found
Theoretical Study of Small Iron–Oxyhydroxide Clusters and Formation of Ferrihydrite
Hydrolysis
of iron compounds in water leads to the formation of
FeÂ(III) oyxhydroxide-based minerals like ferrihydrite, which act as
natural scavengers of inorganic contaminants in the environment. Though
studied widely, experimental identification of these oxyhydroxides
remains very difficult due to their extreme reactivity. The present
study theoretically investigates the formation of FeÂ(III) oxyhydroxides
starting from a single hydrated FeÂ(III) ion, modeling the formation
of larger clusters gradually. The structures, formation enthalpies,
and free energies of dimers, trimers, tetramers, and even larger FeÂ(III)
oxyhydroxide clusters comprising of Fe<sub>5</sub>, Fe<sub>7</sub>, and Fe<sub>13</sub>–Keggin ions in gaseous phase and in
aqueous medium (using self-consistent reaction field method) are systematically
studied using density functional theory. Spontaneous formation of
certain multinuclear FeÂ(III) oxyhydroxide clusters with clear structural
signatures of ferrihydrite highlights their potential as prenucleation
clusters in the course of mineralization
A Bottom-Up Approach toward Fabrication of Ultrathin PbS Sheets
Two-dimensional (2D) sheets are currently in the spotlight
of nanotechnology
owing to high-performance device fabrication possibilities. Building
a free-standing quantum sheet with controlled morphology is challenging
when large planar geometry and ultranarrow thickness are simultaneously
concerned. Coalescence of nanowires into large single-crystalline
sheet is a promising approach leading to large, molecularly thick
2D sheets with controlled planar morphology. Here we report on a bottom-up
approach to fabricate high-quality ultrathin 2D single crystalline
sheets with well-defined rectangular morphology via collective coalescence
of PbS nanowires. The ultrathin sheets are strictly rectangular with
1.8 nm thickness, 200–250 nm width, and 3–20 μm
length. The sheets show high electrical conductivity at room and cryogenic
temperatures upon device fabrication. Density functional theory (DFT)
calculations reveal that a single row of delocalized orbitals of a
nanowire is gradually converted into several parallel conduction channels
upon sheet formation, which enable superior in-plane carrier conduction
Hierarchical Polyoxometallate Confined in Woven Thin Films for Single-Cluster Catalysis: Simplified Electrodes for Far-Fetched O<sub>2</sub> Evolution from Seawater
The highly anticipated artificial conversion of water
to oxygen
for the imperishable growth of renewable energy requires efficient
water oxidation catalysts (WOCs) to drive the exciting 4e– transformation at low driving potentials. Herein, we describe the
freestanding thin film of P5Q7 (TFPQ), where
Preyssler [P5W30O110]14– (P5) clusters are woven with [CH3(CH2)6]4N(Br) chains (Q7) to confine
P5 clusters and maximize its catalytic exposure. The TFPQ-supported
electrode shows OER at record-low overpotentials at 10 mAcm2 (η10 = 130 and 490 mV), rapid migration of electrons
(Tafel, 35 and 56 mVdec–1), turnover frequency (TOF,
8.55 s–1), in alkaline water (1 M KOH), and natural
seawater, respectively. Evenly dispersed and confined conducting P5 clusters with a delocalized charge cloud shows ∼3
times lower η10 and eventually high OER efficiency
than nonconfined clusters. The TFPQ electrodes showed a prolonged
stability of minimum 1000 cycles in alkaline water and seawater, without
the leaching of true catalytic species P5
Hierarchical Polyoxometallate Confined in Woven Thin Films for Single-Cluster Catalysis: Simplified Electrodes for Far-Fetched O<sub>2</sub> Evolution from Seawater
The highly anticipated artificial conversion of water
to oxygen
for the imperishable growth of renewable energy requires efficient
water oxidation catalysts (WOCs) to drive the exciting 4e– transformation at low driving potentials. Herein, we describe the
freestanding thin film of P5Q7 (TFPQ), where
Preyssler [P5W30O110]14– (P5) clusters are woven with [CH3(CH2)6]4N(Br) chains (Q7) to confine
P5 clusters and maximize its catalytic exposure. The TFPQ-supported
electrode shows OER at record-low overpotentials at 10 mAcm2 (η10 = 130 and 490 mV), rapid migration of electrons
(Tafel, 35 and 56 mVdec–1), turnover frequency (TOF,
8.55 s–1), in alkaline water (1 M KOH), and natural
seawater, respectively. Evenly dispersed and confined conducting P5 clusters with a delocalized charge cloud shows ∼3
times lower η10 and eventually high OER efficiency
than nonconfined clusters. The TFPQ electrodes showed a prolonged
stability of minimum 1000 cycles in alkaline water and seawater, without
the leaching of true catalytic species P5
Hierarchical Polyoxometallate Confined in Woven Thin Films for Single-Cluster Catalysis: Simplified Electrodes for Far-Fetched O<sub>2</sub> Evolution from Seawater
The highly anticipated artificial conversion of water
to oxygen
for the imperishable growth of renewable energy requires efficient
water oxidation catalysts (WOCs) to drive the exciting 4e– transformation at low driving potentials. Herein, we describe the
freestanding thin film of P5Q7 (TFPQ), where
Preyssler [P5W30O110]14– (P5) clusters are woven with [CH3(CH2)6]4N(Br) chains (Q7) to confine
P5 clusters and maximize its catalytic exposure. The TFPQ-supported
electrode shows OER at record-low overpotentials at 10 mAcm2 (η10 = 130 and 490 mV), rapid migration of electrons
(Tafel, 35 and 56 mVdec–1), turnover frequency (TOF,
8.55 s–1), in alkaline water (1 M KOH), and natural
seawater, respectively. Evenly dispersed and confined conducting P5 clusters with a delocalized charge cloud shows ∼3
times lower η10 and eventually high OER efficiency
than nonconfined clusters. The TFPQ electrodes showed a prolonged
stability of minimum 1000 cycles in alkaline water and seawater, without
the leaching of true catalytic species P5
Supramolecular Aggregates of Tetraphenylethene-Cored AIEgen toward Mechanoluminescent and Electroluminescent Devices
Luminescent
materials possessing both the mechanoluminescence (MCL)
and electroluminescence (EL) properties are the quest for sensing
and optoelectronic applications. We report on the synthesis of a new
tailor-made luminogen, 1,2-bisÂ(4-(1-([1,1′-biphenyl]-4-yl)-2,2-diphenylvinyl)Âphenyl)-1,2-diphenylethene
(<b>TPE 5</b>), using Suzuki coupling reaction with high yield.
An aggregation-induced emission (AIE) active complex <b>TPE 5</b> forms supramolecular spherical aggregates at the air–water
interface of a Langmuir trough. As a consequence, a large enhancement
of luminescence is obtained from the mono- and multilayer Langmuir–Blodgett
films of <b>TPE 5</b> owing to the AIE effect. The luminogen <b>TPE 5</b> exhibits a reversible MCL response, displaying photoluminescence
switching due to change in the crystalline states under external stimuli.
The unique feature of luminescence enhancement upon aggregate formation
is utilized for the fabrication of light-emitting diodes with low
threshold voltage using supramolecular aggregates as the active layer.
This work demonstrates an efficient strategy for obtaining controlled
supramolecular aggregates of AIEgen with a potential in the dual applications
of MCL and EL
Aligned 1‑D Nanorods of a π‑Gelator Exhibit Molecular Orientation and Excitation Energy Transport Different from Entangled Fiber Networks
Linear
Ï€-gelators self-assemble into entangled fibers in
which the molecules are arranged perpendicular to the fiber long axis.
However, orientation of gelator molecules in a direction parallel
to the long axes of the one-dimensional (1-D) structures remains challenging.
Herein we demonstrate that, at the air–water interface, an
oligoÂ(<i>p</i>-phenylenevinylene)-derived Ï€-gelator
forms aligned nanorods of 340 ± 120 nm length and 34 ± 5
nm width, in which the gelator molecules are reoriented parallel to
the long axis of the rods. The orientation change of the molecules
results in distinct excited-state properties upon local photoexcitation,
as evidenced by near-field scanning optical microscopy. A detailed
understanding of the mechanism by which excitation energy migrates
through these 1-D molecular assemblies might help in the design of
supramolecular structures with improved charge-transport properties