4 research outputs found
Selective Oxidizing Gas Sensing and Dominant Sensing Mechanism of <i>n</i>‑CaO-Decorated <i>n</i>‑ZnO Nanorod Sensors
In this work, we
investigated the NO<sub>2</sub> and CO sensing
properties of <i>n</i>-CaO-decorated <i>n</i>-ZnO
nanorods and the dominant sensing mechanism in <i>n</i>–<i>n</i> heterostructured one-dimensional (1D) nanostructured multinetworked
chemiresistive gas sensors utilizing the nanorods. The CaO-decorated <i>n</i>-ZnO nanorods showed stronger response to NO<sub>2</sub> than most other ZnO-based nanostructures, including the pristine
ZnO nanorods. Many researchers have attributed the enhanced sensing
performance of heterostructured sensors to the modulation of the conduction
channel width or surface depletion layer width. However, the modulation
of the conduction channel width is not the true cause of the enhanced
sensing performance of <i>n</i>–<i>n</i> heterostructured 1D gas sensors, because the radial modulation of
the conduction channel width is not intensified in these sensors.
In this work, we demonstrate that the enhanced performance of the <i>n</i>-CaO-decorated <i>n</i>-ZnO nanorod sensor is
mainly due to a combination of the enhanced modulation of the potential
barrier height at the <i>n</i>–<i>n</i> heterojunctions, the larger surface-area-to-volume ratio and the
increased surface defect density of the decorated ZnO nanorods, not
the enhanced modulation of the conduction channel width
Highly Sensitive Ratiometric Fluorescent Chemosensor for Silver Ion and Silver Nanoparticles in Aqueous Solution
A pyrene derivative chemosensor (<b>Pyr-WH</b>) based on a dipeptide shows a highly sensitive ratiometric response to Ag(I) as well as silver nanoparticles in aqueous solution at physiological pH. <b>Pyr-WH</b> penetrated live HeLa cells and exhibits a ratiometric response to intracellular Ag(I). The binding mode of <b>Pyr-WH</b> with Ag(I) was characterized based on fluorescence changes in different pH, NMR, and ESI mass spectrometer experiments
Silicotungstate, a Potential Electron Transporting Layer for Low-Temperature Perovskite Solar Cells
Thin
films of a heteropolytungstate, lithium silicotungstate (Li<sub>4</sub>SiW<sub>12</sub>O<sub>40</sub>, termed Li-ST), prepared by a solution
process at low temperature, were successfully applied as electron
transporting layer (ETL) of planar-type perovskite solar cells (PSCs).
Dense and uniform Li-ST films were prepared on FTO glass by depositing
a thin Li-ST buffer layer, followed by coating of a main Li-ST layer.
The film thickness was controlled by varying the number of coating
cycles, consisting of spin-coating and thermal treatment at 150 °C.
In particular, by employing 60 nm-thick Li-ST layer obtained by two
cycles of coating, the fabricated CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> PSC device demonstrates the photovoltaic conversion efficiency
(PCE) of 14.26% with <i>J</i><sub>SC</sub> of 22.16 mA cm<sup>–2</sup>, <i>V</i><sub>OC</sub> of 0.993 mV and
FF of 64.81%. The obtained PCE is significantly higher than that of
the PSC employing a TiO<sub>2</sub> layer processed at the same temperature
(PCE = 12.27%). Spectroscopic analyses by time-resolved photoluminescence
and pulsed light-induced transient measurement of photocurrent indicate
that the Li-ST layer collects electrons from CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> more efficiently and also exhibits longer
electron lifetime than the TiO<sub>2</sub> layer thermally treated
at 150 °C. Thus, Li-ST is considered to be a promising ETL material
that can be applied for the fabrication of flexible PSC devices
Novel Carbazole-Based Hole-Transporting Materials with Star-Shaped Chemical Structures for Perovskite-Sensitized Solar Cells
Novel carbazole-based hole-transporting
materials (HTMs), including
extended π-conjugated central core units such as 1,4-phenyl,
4,4′-biphenyl, or 1,3,5-trisphenylbenzene for promoting effective
π–π stacking as well as the hexyloxy flexible group
for enhancing solubility in organic solvent, have been synthesized
as HTM of perovskite-sensitized solar cells. A HTM with 1,3,5-trisphenylbenzene
core, coded as <b>SGT-411,</b> exhibited the highest charge
conductivity caused by its intrinsic property to form crystallized
structure. The perovskite-sensitized solar cells with <b>SGT-411</b> exhibited the highest PCE of 13.00%, which is 94% of that of the
device derived from <i>spiro</i>-OMeTAD (13.76%). Time-resolved
photoluminescence spectra indicate that <b>SGT-411</b> shows
the shortest decay time constant, which is in agreement with the trends
of conductivity data, indicating it having fastest charge regeneration.
In this regard, a carbazole-based HTM with star-shaped chemical structure
is considered to be a promising candidate HTM