22 research outputs found
In vivo detection of cryosurgery using multiphoton and harmonic generation microscopy
The tissue injury and the organization of collagen during cryosurgery are poorly characterized because of the lack of appropriate methodologies. In this study, we use multimodal multiphoton microscopy to assess the change of extracellular matrix after cryotreatment of skin. The cellular matrix transformations and the intercellular interactions during the wound healing process after cryolesion for mice were measured in vivo and in real-time through the dorsal skinfold chamber (DSC). Intrinsic second- harmonic generation (SHG) signals from fibrillar collagen and two-photon excited (TPE) autofluorescence from cell were collected to investigate the cryosurgical response in vivo. The TPE and SHG signals are significantly different between normal and cryotreated mice, and correlates with the wound healing process. The results suggest that this approach may be applied in real-time to noninvasively monitor the cryosurgery process and could potentially be applied to clinical evaluation
Novel mat exergaming to improve the physical performance, cognitive function, and dual-task walking and decrease the fall risk of community-dwelling older adults
[[abstract]]Physical exercise and cognitive training were previously demonstrated to improve the physical functioning and decrease the incidence of falls for older adults. This study aimed to utilize an interactive exergame mat system to develop a novel cognitive–physical training program and explore the training effects on physical performance, cognitive function, dual-task walking (DTW), and fall risk compared to the control condition. In this quasi-experimental non-randomized controlled intervention study, 110 community-dwelling older adults participated. The exercise group (n = 56; mean age, 70.7 ± 4.6 years) performed ladder-type, three-by-three grid-type, and circle-type mat exergames with simultaneous cognitive–physical training (EMAT), while the control group (n = 54; mean age, 72.0 ± 5.7 years) underwent a multicomponent exercise intervention focused on physical and cognitive training. A 2 h training session was completed weekly for 3 months. Functional fitness (including upper- and lower-extremity strength and flexibility, grasp strength, aerobic endurance, static balance, dynamic balance and agility), a foot tapping test (FTT), the Montreal Cognitive Assessment (MoCA), DTW, and a fall risk questionnaire (FRQ) were assessed before and after the interventions. The EMAT program enhanced upper-extremity strength, lower-extremity strength and flexibility, aerobic endurance, and dynamic balance and agility; improved DTW and FTT performances; and decreased FRQ score. EMAT also showed a significant advantage over control in terms of lower-extremity strength and flexibility, aerobic endurance, dynamic balance and agility, and FRQ score (all P < 0.05). The current study provides evidence of the effects of a novel mat exergaming program on physical and cognitive performance. EMAT effectively reduced the fall risk and increased the dual-task ability of walking, factors that are important in fall prevention for community-dwelling older adults
Plasmonics-Based Multifunctional Electrodes for Low-Power-Consumption Compact Color-Image Sensors
High pixel density, efficient color
splitting, a compact structure, superior quantum efficiency, and low
power consumption are all important features for contemporary color-image
sensors. In this study, we developed a surface plasmonics-based color-image
sensor displaying a high photoelectric response, a microlens-free
structure, and a zero-bias working voltage. Our compact sensor comprised
only (i) a multifunctional electrode based on a single-layer structured
aluminum (Al) film and (ii) an underlying silicon (Si) substrate.
This approach significantly simplifies the device structure and fabrication
processes; for example, the red, green, and blue color pixels can
be prepared simultaneously in a single lithography step. Moreover,
such Schottky-based plasmonic electrodes perform multiple functions,
including color splitting, optical-to-electrical signal conversion,
and photogenerated carrier collection for color-image detection. Our
multifunctional, electrode-based device could also avoid the interference
phenomenon that degrades the color-splitting spectra found in conventional
color-image sensors. Furthermore, the device took advantage of the
near-field surface plasmonic effect around the AlSi junction
to enhance the optical absorption of Si, resulting in a significant
photoelectric current output even under low-light surroundings and
zero bias voltage. These plasmonic Schottky-based color-image devices
could convert a photocurrent directly into a photovoltage and provided
sufficient voltage output for color-image detection even under a light
intensity of only several femtowatts per square micrometer. Unlike
conventional color image devices, using voltage as the output signal
decreases the area of the periphery read-out circuit because it does
not require a current-to-voltage conversion capacitor or its related
circuit. Therefore, this strategy has great potential for direct integration
with complementary metal-oxide-semiconductor (CMOS)-compatible circuit
design, increasing the pixel density of imaging sensors developed
using mature Si-based technology
Transparent, Broadband, Flexible, and Bifacial-Operable Photodetectors Containing a Large-Area Graphene–Gold Oxide Heterojunction
In this study, we combine graphene with gold oxide (AuO<sub><i>x</i></sub>), a transparent and high-work-function electrode material, to achieve a high-efficient, low-bias, large-area, flexible, transparent, broadband, and bifacial-operable photodetector. The photodetector operates through hot electrons being generated in the graphene and charge separation occurring at the AuO<sub><i>x</i></sub>–graphene heterojunction. The large-area graphene covering the AuO<sub><i>x</i></sub> electrode efficiently prevented reduction of its surface; it also acted as a square-centimeter-scale active area for light harvesting and photodetection. Our graphene/AuO<sub><i>x</i></sub> photodetector displays high responsivity under low-intensity light illumination, demonstrating picowatt sensitivity in the ultraviolet regime and nanowatt sensitivity in the infrared regime for optical telecommunication. In addition, this photodetector not only exhibited broadband (from UV to IR) high responsivity3300 A W<sup>–1</sup> at 310 nm (UV), 58 A W<sup>–1</sup> at 500 nm (visible), and 9 A W<sup>–1</sup> at 1550 nm (IR)but also required only a low applied bias (0.1 V). The hot-carrier-assisted photoresponse was excellent, especially in the short-wavelength regime. In addition, the graphene/AuO<sub><i>x</i></sub> photodetector exhibited great flexibility and stability. Moreover, such vertical heterojunction-based graphene/AuO<sub><i>x</i></sub> photodetectors should be compatible with other transparent optoelectronic devices, suggesting applications in flexible and wearable optoelectronic technologies
<i>Romantic Story or Raman Scattering?</i> Rose Petals as Ecofriendly, Low-Cost Substrates for Ultrasensitive Surface-Enhanced Raman Scattering
In this Article, we present a facile
approach for the preparation
of ecofriendly substrates, based on common rose petals, for ultrasensitive
surface-enhanced Raman scattering (SERS). The hydrophobic concentrating
effect of the rose petals allows us to concentrate metal nanoparticle
(NP) <i>aggregates</i> and analytes onto their surfaces.
From a systematic investigation of the SERS performance when using
upper and lower epidermises as substrates, we find that the lower
epidermis, with its quasi-three-dimensional (quasi-3D) nanofold structure,
is the superior biotemplate for SERS applications. The metal NPs and
analytes are both closely packed in the quasi-3D structure of the
lower epidermis, thereby enhancing the Raman signals dramatically
within the depth of focus (DOF) of the Raman optical system. We have
also found the effect of the pigment of the petals on the SERS performance.
With the novel petal-based substrate, the SERS measurements reveal
a detection limit for rhodamine 6G below the femtomolar regime (10<sup>–15</sup> M), with high reproducibility. Moreover, when we
employ an upside-down drying process, the unique effect of the Wenzal
state of the hydrophobic petal surface further concentrate the analytes
and enhanced the SERS signals. Rose petals are green, natural materials
that appear to have great potential for use in biosensors and biophotonics
White-Light-Induced Collective Heating of Gold Nanocomposite/Bombyx mori Silk Thin Films with Ultrahigh Broadband Absorbance
This paper describes a systematic investigation of the phenomenon of white-light-induced heating in silk fibroin films embedded with gold nanoparticles (Au NPs). The Au NPs functioned to develop an ultrahigh broadband absorber, allowing white light to be used as a source for photothermal generation. With an increase of the Au content in the composite films, the absorbance was enhanced significantly around the localized surface plasmon resonance (LSPR) wavelength, while non-LSPR wavelengths were also increased dramatically. The greater amount of absorbed light increased the rate of photoheating. The optimized composite film exhibited ultrahigh absorbances of approximately 95% over the spectral range from 350 to 750 nm, with moderate absorbances (>60%) at longer wavelengths (750–1000 nm). As a result, the composite film absorbed almost all of the incident light and, accordingly, converted this optical energy to local heat. Therefore, significant temperature increases (<i>ca.</i> 100 °C) were readily obtained when we irradiated the composite film under a light-emitting diode or halogen lamp. Moreover, such composite films displayed linear light-to-heat responses with respect to the light intensity, as well as great photothermal stability. A broadband absorptive film coated on a simple Al/Si Schottky diode displayed a linear, significant, stable photo-thermo-electronic effect in response to varying the light intensity
Nanocrystallized CdS beneath the Surface of a Photoconductor for Detection of UV Light with Picowatt Sensitivity
In
this study, we demonstrated that the improvement of detection
capability of cadmium sulfide (CdS) photoconductors in the ultraviolet
(UV) regime is much larger than that in the visible regime, suggesting
that the deep UV laser-treated CdS devices are very suitable for low-light
detection in the UV regime. We determined that a nanocrystallized
CdS photoconductor can behave as a picowatt-sensitive detector in
the UV regime after ultra-shallow-region crystallization of the CdS
film upon a single shot from a KrF laser. Photoluminescence and Raman
spectra revealed that laser treatment increased the degree of crystallization
of the CdS and led to the effective removal of defects in the region
of a few tens nanometers beneath the surface of CdS, confirming the
result by the transmission electron microscopy (TEM) images. Optical
simulations suggested that UV light was almost completely absorbed
in the shallow region beneath the surface of the CdS films, consistent
with the observed region that underwent major crystal structure transformation.
Accordingly, we noted a dramatic enhancement in responsivity of the
CdS devices in the UV regime. Under a low bias voltage (1 mV), the
treated CdS device provided a high responsivity of 74.7 A W<sup>–1</sup> and a detectivity of 1.0 × 10<sup>14</sup> Jones under illumination
with a power density of 1.9 nW cm<sup>–2</sup>. Even when the
power of the UV irradiation on the device was only 3.5 pW, the device
exhibited extremely high responsivity (7.3 × 10<sup>5</sup> A
W<sup>–1</sup>) and detectivity (3.5 × 10<sup>16</sup> Jones) under a bias voltage of 1 V. Therefore, the strategy proposed
in this study appears to have great potential for application in the
development of CdS photoconductors for picowatt-level detection of
UV light with low power consumption
Nondestructive Characterization of the Structural Quality and Thickness of Large-Area Graphene on Various Substrates
We
demonstrate an inspection technique, based on only one ellipsometric
parameter, Ψ, of spectroscopic ellipsometry (SE), for the rapid,
simultaneous identification of both the structural quality and thicknesses
of large-area graphene films. The measured Ψ spectra are strongly
affected by changes in the out-of-plane absorption coefficients (α<sub>TM</sub>); they are also correlated to the ratio of the intensities
of the D and G bands in Raman spectra of graphene films. In addition,
the electronic transition state of graphene within the UV regime assists
the characterization of the structural quality. We also demonstrated
that the intensities and shifts of the signals in Ψ spectra
allow clear identification of the structural qualities and thicknesses,
respectively, of graphene films. Moreover, this Ψ-based method
can be further applied to graphene films coated on various substrates.
In addition, mapping of the values of Ψ is a very convenient
and useful means of rapidly characterizing both the structural quality
and thickness of 2D materials at local areas. Therefore, this Ψ-based
characterization method has great potential for application in the
mass production of devices based on large-area graphene