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 AlSi 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_<i>x</i>), 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_<i>x</i>–graphene heterojunction. The large-area graphene covering the AuO_<i>x</i> 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_<i>x</i> 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 responsivity3300 A W^–1 at 310 nm (UV), 58 A W^–1 at 500 nm (visible), and 9 A W^–1 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_<i>x</i> photodetector exhibited great flexibility and stability. Moreover, such vertical heterojunction-based graphene/AuO_<i>x</i> 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^–15 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^–1 and a detectivity of 1.0 × 10¹⁴ Jones under illumination with a power density of 1.9 nW cm^–2. Even when the power of the UV irradiation on the device was only 3.5 pW, the device exhibited extremely high responsivity (7.3 × 10⁵ A W^–1) and detectivity (3.5 × 10¹⁶ 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_TM); 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