9 research outputs found
Hydrothermal synthesis of nitrogen-doped carbon dots as a sensitive fluorescent probe for the rapid, selective determination of Hg<sup>2+</sup>
<p>In the present work, a green synthetic method for producing nitrogen-doped carbon dots (NCDs) by using ammonium citrate and urea is introduced. The obtained NCDs were characterised by transmission electron microscopy, Fourier transform infrared spectra, UV–vis absorption and fluorescence spectra. The results showed that the prepared NCDs were spherical with a size of about 3.5 nm, emitting strong and stable blue fluorescence when excited at 352 nm. It was noting that the NCDs enable sensitive and selective determination of Hg<sup>2+</sup> in tap water with a linear range of 0.01–5 mg L<sup>−1</sup> based on a possible charge transfer process. The detection limit was 9.4 µg L<sup>−1</sup>.</p
Hydrothermal synthesis of fluorescent nitrogen-doped carbon quantum dots from ascorbic acid and valine for selective determination of picric acid in water samples
<p>Nitrogen doped carbon quantum dots (N-CQDs) were synthesised by a hydrothermal method using ascorbic acid and valine as precursors. The as-synthesised N-CQDs were characterised by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV−vis absorption spectra, as well as fluorescence spectrophotometer. The results revealed that the as-prepared N-CQDs were spherical shaped with an average diameter of 4 nm and emitted bright blue photoluminescence with a quantum yield of approximately 4.8 %. Additionally, we found that the fluorescence of the N-CQDs was intensively quenched by the addition of picric acid (PA). The decrease of the fluorescence intensity made it possible to determine PA in the linear range of 0.06–7.81 µg ml<sup>–</sup><sup>1</sup> based on the fluorescence resonance energy transfer between PA and N-CQDs. The detection limit was as low as 11.46 ng ml<sup>–</sup><sup>1</sup>. The proposed approach was further successfully applied for the determination of PA in water sample collected from Fenhe river for public safety and security, suggesting its great potential towards water routine analysis.</p
Active Antifogging Property of Monolayer SiO<sub>2</sub> Film with Bioinspired Multiscale Hierarchical Pagoda Structures
Antifogging surfaces with hydrophilic
or even superhydrophilic
wetting behavior have received significant attention due to their
ability to reduce light scattering by film-like condensation. However,
a major challenge remains in achieving high-speed antifogging performance
and revealing the hydrophilic-based antifogging mechanism of glass
or other transparent materials under aggressive fogging conditions.
Herein, with inspiration from the fog-free property of the typical Morpho menelaus terrestris butterfly (Butler, 1866)
wing scales, a monolayer SiO<sub>2</sub> film with multiscale hierarchical
pagoda structures (MHPSs) based on glass substrate was designed and
fabricated using an optimized biotemplate-assisted wet chemical method
without any post-treatments. The biomimetic monolayer film (BMF) composed
of nanoscale SiO<sub>2</sub> 3D networks displayed excellent antifogging
properties, which is superior to that of the glass substrate itself.
The MHPS-based BMF even kept high transmittance (∼95%) under
aggressive fog conditions, and it almost instantaneously recovered
to a fog-free state (<5 s). Moreover, the underlying active antifogging
strategy gathering initial fog capture and final antifog together
was revealed. The fogdrops spontaneously adhered on the BMF surface
and rapidly spread along the MHPSs in an anisotropic way, which made
the fogdrops evaporate instantaneously to attain an initial fog-free
state, leading to an efficient active antifogging performance. These
properties mainly benefit from the synergistic effect of both hydrophilic
chemical compositions (nanoscale SiO<sub>2</sub>) and physical structures
(biomimetic MHPSs) of the BMF. High-speed active antifogging performance
of the glass materials enabled the retention of a high transmittance
property even in humid conditions, heralding reliable optical performance
in outdoor practical applications, especially in aggressive foggy
environments. More importantly, the investigations in this work offer
a promising way to handily design and fabricate quasi-textured surfaces
with multiscale hierarchical structures that possess high-performance
physicochemical properties
Active Antifogging Property of Monolayer SiO<sub>2</sub> Film with Bioinspired Multiscale Hierarchical Pagoda Structures
Antifogging surfaces with hydrophilic
or even superhydrophilic
wetting behavior have received significant attention due to their
ability to reduce light scattering by film-like condensation. However,
a major challenge remains in achieving high-speed antifogging performance
and revealing the hydrophilic-based antifogging mechanism of glass
or other transparent materials under aggressive fogging conditions.
Herein, with inspiration from the fog-free property of the typical Morpho menelaus terrestris butterfly (Butler, 1866)
wing scales, a monolayer SiO<sub>2</sub> film with multiscale hierarchical
pagoda structures (MHPSs) based on glass substrate was designed and
fabricated using an optimized biotemplate-assisted wet chemical method
without any post-treatments. The biomimetic monolayer film (BMF) composed
of nanoscale SiO<sub>2</sub> 3D networks displayed excellent antifogging
properties, which is superior to that of the glass substrate itself.
The MHPS-based BMF even kept high transmittance (∼95%) under
aggressive fog conditions, and it almost instantaneously recovered
to a fog-free state (<5 s). Moreover, the underlying active antifogging
strategy gathering initial fog capture and final antifog together
was revealed. The fogdrops spontaneously adhered on the BMF surface
and rapidly spread along the MHPSs in an anisotropic way, which made
the fogdrops evaporate instantaneously to attain an initial fog-free
state, leading to an efficient active antifogging performance. These
properties mainly benefit from the synergistic effect of both hydrophilic
chemical compositions (nanoscale SiO<sub>2</sub>) and physical structures
(biomimetic MHPSs) of the BMF. High-speed active antifogging performance
of the glass materials enabled the retention of a high transmittance
property even in humid conditions, heralding reliable optical performance
in outdoor practical applications, especially in aggressive foggy
environments. More importantly, the investigations in this work offer
a promising way to handily design and fabricate quasi-textured surfaces
with multiscale hierarchical structures that possess high-performance
physicochemical properties
Bioinspired Omnidirectional Self-Stable Reflectors with Multiscale Hierarchical Structures
Structured surfaces,
demonstrating various wondrous physicochemical performances, are ubiquitous
phenomena in nature. Butterfly wings with impressive structural colors
are an interesting example for multiscale hierarchical structures
(MHSs). However, most natural structural colors are relatively unstable
and highly sensitive to incident angles, which limit their potential
practical applications to a certain extent. Here, we reported a bioinspired
color reflector with omnidirectional reflective self-stable (ORS) properties, which is inspired by the
wing scales of <i>Papilio palinurus</i> butterfly. Through
experimental exploration and theoretical analysis, it was found that
the vivid colors of such butterfly wings are structure-based and possess
novel ORS properties, which attributes to the multiple optical actions
between light and the complex structures coupling the inverse opal-like
structures (IOSs) and stacked lamellar ridges (SLRs). On the basis
of this, we designed and successfully fabricated the SiO<sub>2</sub>-based bioinspired color reflectors (BCRs) through a facile and effective
biotemplate method. It was confirmed that the MHSs in biotemplate
are inherited by the obtained SiO<sub>2</sub>-based BCRs. More importantly,
the SiO<sub>2</sub>-based BCRs also demonstrated the similar ORS properties
in a wide wavelength range. We forcefully anticipate that the reported
MHS-based ORS performance discovered in butterfly wing scales here
could offer new thoughts for scientists to solve unstable reflection
issues in particular optical field. The involved biotemplate fabrication
method offers a facile and effective strategy for fabricating functional
nanomaterials or bioinspired nanodevices with 3D complex nanostructures,
such as structured optical devices, displays, and optoelectronic equipment
Degradable Bioinspired Hypersensitive Strain Sensor with High Mechanical Strength Using a Basalt Fiber as a Reinforced Layer
Flexible strain sensors have received extensive attention
due to
their broad application prospects. However, a majority of present
flexible strain sensors may fail to maintain normal sensing performances
upon external loads because of their low strength and thus their performances
are affected drastically with increasing loads, which severely restricts
large-area popularization and application. Scorpions with hypersensitive
vibration slit sensilla are coincident with a similar predicament.
Herein, it is revealed that scorpions intelligently use risky slits
to detect subtle vibrations, and meanwhile, the distinct layered composites
of the main body of this organ prevent catastrophic failure of the
sensory structure. Furthermore, the extensive use of flexible sensors
will generate a mass of electronic waste just as obsoleting silicon-based
devices. Considering mechanical properties and environmental issues,
a flexible strain sensor based on an elastomer (Ecoflex)-wrapped fabric
with the woven structure was designed and fabricated. Note that introducing
a “green” basalt fiber (BF) into a degradable elastomer
can effectively avoid environmental issues and significantly enhance
the mechanical properties of the sensor. As a result, it shows excellent
sensitivity (gauge factor (GF) ∼138.10) and high durability
(∼40,000 cycles). Moreover, the reduced graphene oxide (RGO)/BF/Ecoflex
flexible strain sensor possesses superior mechanical properties (tensile
strength ∼20 MPa) and good flexibility. More significantly,
the sensor can maintain normal performances under large external tensions,
impact loads, and even underwater environments, providing novel design
principles for environmentally friendly flexible sensors under extremely
harsh environments
Degradable Bioinspired Hypersensitive Strain Sensor with High Mechanical Strength Using a Basalt Fiber as a Reinforced Layer
Flexible strain sensors have received extensive attention
due to
their broad application prospects. However, a majority of present
flexible strain sensors may fail to maintain normal sensing performances
upon external loads because of their low strength and thus their performances
are affected drastically with increasing loads, which severely restricts
large-area popularization and application. Scorpions with hypersensitive
vibration slit sensilla are coincident with a similar predicament.
Herein, it is revealed that scorpions intelligently use risky slits
to detect subtle vibrations, and meanwhile, the distinct layered composites
of the main body of this organ prevent catastrophic failure of the
sensory structure. Furthermore, the extensive use of flexible sensors
will generate a mass of electronic waste just as obsoleting silicon-based
devices. Considering mechanical properties and environmental issues,
a flexible strain sensor based on an elastomer (Ecoflex)-wrapped fabric
with the woven structure was designed and fabricated. Note that introducing
a “green” basalt fiber (BF) into a degradable elastomer
can effectively avoid environmental issues and significantly enhance
the mechanical properties of the sensor. As a result, it shows excellent
sensitivity (gauge factor (GF) ∼138.10) and high durability
(∼40,000 cycles). Moreover, the reduced graphene oxide (RGO)/BF/Ecoflex
flexible strain sensor possesses superior mechanical properties (tensile
strength ∼20 MPa) and good flexibility. More significantly,
the sensor can maintain normal performances under large external tensions,
impact loads, and even underwater environments, providing novel design
principles for environmentally friendly flexible sensors under extremely
harsh environments
Degradable Bioinspired Hypersensitive Strain Sensor with High Mechanical Strength Using a Basalt Fiber as a Reinforced Layer
Flexible strain sensors have received extensive attention
due to
their broad application prospects. However, a majority of present
flexible strain sensors may fail to maintain normal sensing performances
upon external loads because of their low strength and thus their performances
are affected drastically with increasing loads, which severely restricts
large-area popularization and application. Scorpions with hypersensitive
vibration slit sensilla are coincident with a similar predicament.
Herein, it is revealed that scorpions intelligently use risky slits
to detect subtle vibrations, and meanwhile, the distinct layered composites
of the main body of this organ prevent catastrophic failure of the
sensory structure. Furthermore, the extensive use of flexible sensors
will generate a mass of electronic waste just as obsoleting silicon-based
devices. Considering mechanical properties and environmental issues,
a flexible strain sensor based on an elastomer (Ecoflex)-wrapped fabric
with the woven structure was designed and fabricated. Note that introducing
a “green” basalt fiber (BF) into a degradable elastomer
can effectively avoid environmental issues and significantly enhance
the mechanical properties of the sensor. As a result, it shows excellent
sensitivity (gauge factor (GF) ∼138.10) and high durability
(∼40,000 cycles). Moreover, the reduced graphene oxide (RGO)/BF/Ecoflex
flexible strain sensor possesses superior mechanical properties (tensile
strength ∼20 MPa) and good flexibility. More significantly,
the sensor can maintain normal performances under large external tensions,
impact loads, and even underwater environments, providing novel design
principles for environmentally friendly flexible sensors under extremely
harsh environments
Atomistic Insight into the Epitaxial Growth Mechanism of Single-Crystal Two-Dimensional Transition-Metal Dichalcogenides on Au(111) Substrate
A mechanistic understanding of interactions between atomically
thin two-dimensional (2D) transition-metal dichalcogenides (TMDs)
and their growth substrates is important for achieving the unidirectional
alignment of nuclei and seamless stitching of 2D TMD domains and thus
2D wafers. In this work, we conduct a cross-sectional scanning transmission
electron microscopy (STEM) study to investigate the atomic-scale nucleation
and early stage growth behaviors of chemical vapor deposited monolayer
(ML-) MoS2 and molecular beam epitaxy ML-MoSe2 on a Au(111) substrate. Statistical analysis reveals the majority
of as-grown domains, i.e., ∼88% for MoS2 and 90%
for MoSe2, nucleate on surface terraces, with the rest
(i.e., ∼12% for MoS2 and 10% for MoSe2) on surface steps. Moreover, within the latter case, step-associated
nucleation, ∼64% of them are terminated with a Mo-zigzag edge
in connection with the Au surface steps, with the rest (∼36%)
being S-zigzag edges. In conjunction with ab initio density functional theory calculations, the results confirm that
van der Waals epitaxy, rather than the surface step guided epitaxy,
plays deterministic roles for the realization of unidirectional ML-MoS2 (MoSe2) domains on a Au(111) substrate. In contrast,
surface steps, particularly their step height, are mainly responsible
for the integrity and thickness of MoS2/MoSe2 films. In detail, it is found that the lateral growth of monolayer
thick MoS2/MoSe2 domains only proceeds across
mono-Au-atom high surface steps (∼2.4 Å), but fail for
higher ones (bi-Au atom step and higher) during the growth. Our cross-sectional
STEM study also confirms the existence of considerable compressive
residual strain that reaches ∼3.0% for ML-MoS2/MoSe2 domains on Au(111). The present study aims to understand
the growth mechanism of 2D TMD wafers