Surface‐enhanced Raman spectroscopy (SERS)‐based biosensors have attracted much attention for their label‐free detection, ultrahigh sensitivity, and unique molecular fingerprinting. In this study, a ...wafer‐scale, ultrasensitive, highly uniform, paper‐based, portable SERS detection platform featuring abundant and dense gold nanopearls with narrow gap distances, are prepared and deposited directly onto ultralow‐surface‐energy fluorosilane‐modified cellulose fibers through simple thermal evaporation by delicately manipulating the atom diffusion behavior. The as‐designed paper‐based SERS substrate exhibits an extremely high Raman enhancement factor (3.9 × 1011), detectability at sub‐femtomolar concentrations (single‐molecule level) and great signal reproductivity (relative standard deviation: 3.97%), even when operated with a portable 785‐nm Raman spectrometer. This system is used for fingerprinting identification of 12 diverse analytes, including clinical medicines (cefazolin, chloramphenicol, levetiracetam, nicotine), pesticides (thiram, paraquat, carbaryl, chlorpyrifos), environmental carcinogens (benzoapyrene, benzog,h,iperylene), and illegal drugs (methamphetamine, mephedrone). The lowest detection concentrations reach the sub‐ppb level, highlighted by a low of 16.2 ppq for nicotine. This system appears suitable for clinical applications in, for example, i) therapeutic drug monitoring for individualized medication adjustment and ii) ultra‐early diagnosis for pesticide intoxication. Accordingly, such scalable, portable and ultrasensitive fibrous SERS substrates open up new opportunities for practical on‐site detection in biofluid analysis, point‐of‐care diagnostics and precision medicine.
A facile, scalable fabrication strategy for developing an ultrasensitive surface‐enhanced Raman spectroscopy (SERS) detection platform that serves as a rapid, label‐free point of care diagnostics device. Highly dense Au nanopearl arrays with narrow gap distances are formed directly through thermal evaporation on hydrophobic cellulose fibers to achieve excellent portable SERS performance (enhancement factor: 3.9 x 1011; detection limit: sub‐femtomolar single molecule level; reproductivity relative standard deviation ≤ 4%).
Although the concept of using local surface plasmon resonance based nanoantenna for photodetection well below the semiconductor band edge has been demonstrated previously, the nature of local surface ...plasmon resonance based devices cannot meet many requirements of photodetection applications. Here we propose the concept of deep-trench/thin-metal (DTTM) active antenna that take advantage of surface plasmon resonance phenomena, three-dimensional cavity effects, and large-area metal/semiconductor junctions to effectively generate and collect hot electrons arising from plasmon decay and, thereby, increase photocurrent. The DTTM-based devices exhibited superior photoelectron conversion ability and high degrees of detection linearity under infrared light of both low and high intensity. Therefore, these DTTM-based devices have the attractive properties of high responsivity, extremely low power consumption, and polarization-insensitive detection over a broad bandwidth, suggesting great potential for use in photodetection and on-chip Si photonics in many applications of telecommunication fields.
Although transparent radiative cooling is a passive cooling strategy with practical applications and aesthetic appeal, complex manufacturing processes and the use of environmentally unfriendly ...thermal emitters remain latent problems. Herein, eco‐friendly transparent silk radiative cooling (TSRC) films are developed, regenerated from natural silkworm cocoons, for zero‐energy‐consumption thermal management of optoelectronic devices. These TSRC films can dissipate heat radiatively through molecular vibrations of the protein backbone and side chains, while retaining the function and appearance of the associated devices, due to their high visible transparency. Theoretical and experimental investigations revealed that the thermal emission increases rapidly upon increasing the film thickness, but slowly thereafter achieves saturation; nevertheless, the intrinsic solar absorption of silk in the ultraviolet and near‐infrared regions also grows linearly, unavoidably weakening the cooling effect. After spectroscopic optimization, the maximum cooling power during the daytime and nighttime is improved to 77.6 and 101.7 W m−2, respectively. Gratifyingly, the films have a remarkable effect on the cooling performance of electronic devices under sunlight. For example, the TSRC film provides a temperature drop of 5.1 °C for a smartphone during multitasking and charging, and 14 °C for a silicon solar panel with an improvement in the photoelectronic conversion efficiency (≈7%).
Transparent silk radiative cooling films can reduce the temperature of a silicon solar panel and a smartphone by 14 and 5.1 °C, respectively, even under direct sunlight, without compromising the function and appearance of the devices. This makes the transparent silk radiative cooling film an eco‐friendly and efficient solution for the thermal management of optoelectronic devices.
Functional materials including metals, ceramics, plastics, and nanomaterials are now widely adopted in modern devices. To facilitate the fabrication of nanostructured functional materials, ...nanoimprint lithography (NIL) technology is developed. The nanoimprint technologies for patterning functional materials are reviewed in this paper. Versatile NIL-based methods have been developed according to the material properties of the target functional materials. Besides the NIL involving dry etching or lift-off process, we also introduce other NIL-based methods such as the direct NIL, reversal NIL, solid state electrochemical stamping, nanotransfer printing, sol-gel NIL and many other improved NIL for functional materials. These methods demonstrate various advantages. For example, the direct NIL facilitates the direct formation of functional metal or plastic nanostructures with a high reproducibility at the centimeter scale, the template stripping method aims to reduce the surface roughness of metal nanostructures to a few-angstrom scale. Besides, multilayer 3D metal/polymer/ceramic nanostructures can be readily achieved on many kinds of substrates by reversal NIL or nanotransfer printing. Moreover, the sol-gel NIL for ceramics, roll-to-roll process for plastics, and some other NIL-based methods for patterning functional materials and nanomaterials are introduced. The optical and electrical properties of the nanostructured functional materials prepared by NIL are discussed. Additionally, the applications of these nanostructured functional materials are also introduced in this article. Overall, this review aims to inspire next-generation devices to be developed by NIL with versatile choices of imprinting processes and materials.
In this article, we demonstrate a semitransparent inverted-type polymer solar cell using a top laminated graphene electrode without damaging the underlying organic photoactive layer. The lamination ...process involves the simultaneous thermal releasing deposition of the graphene top electrode during thermal annealing of the photoactive layer. The resulting semitransparent polymer solar cell exhibits a promising power conversion efficiency of approximately 76% of that of the standard opaque device using an Ag metal electrode. The asymmetric photovoltaic performances of the semitransparent solar cell while illuminated from two respective sides were further analyzed using optical simulation and photocarrier recombination measurement. The devices consisting of the top laminated transparent graphene electrode enable the feasible roll-to-roll manufacturing of low-cost semitransparent polymer solar cells and can be utilized in new applications such as power-generated windows or multijunction or bifacial photovoltaic devices.
With the rapid growth in global energy consumption, the recovery of waste heat is becoming an important issue. Nevertheless, the recovery of near-room-temperature waste heat remains challenging ...because the slight temperature difference with the surroundings leads to extremely low thermoelectric power generation. In this study, we combined a daytime radiative cooling (DRC) technology with a thermoelectric generator (TEG) to efficiently recover near-room-temperature waste heat. We investigated the effects of the thermal radiation and thermal conduction properties of DRC materials on near-room-temperature waste heat recovery (WHR). We designed a hierarchical micro-nano h-BN/ZnO composite (MNHZC) that possessed an outstanding daytime radiative cooling ability and moderate thermal conductivity. With this hierarchical h-BN/ZnO composite, we achieved record-high levels of thermoelectric power generation of 225.3 and 412.3 mW m
−2
during the daytime and nighttime, respectively, with enhancements in thermoelectric power of 1030 and 190%, respectively. The attractive power generation ability of the MNHZC/TEG system suggests its great potential in low-grade waste heat recovery and environmental energy harvesting by consistently generating power in both the daytime and nighttime.
A newly designed daytime radiative cooling (DRC) strategy significantly enhances near-room-temperature waste heat recovery, generating power in both the daytime and nighttime.
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) aggregates 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.
This work presents a novel photo‐electrochemical architecture based on the 3D pyramid‐like graphene/p‐Si Schottky junctions. Overcoming the conventional transfer technique by which only planar ...graphene/Si Schottky junctions are currently available, this work demonstrates the 3D pyramid‐like graphene/p‐Si Schottky junction photocathode, which greatly enhances light harvesting efficiency and exhibits promising photo‐electrochemical performance for hydrogen generation. The formation of 3D pyramid‐like graphene/p‐Si Schottky junctions exhibits enhanced electrochemical activity and promotes charge separation efficiency compared with the bare pyramid Si surface without graphene. The inherent chemical inertness of graphene significantly improves the operational stability of 3D graphene/p‐Si Schottky junction photo‐electrochemical cells. The 3D pyramid‐like graphene/p‐Si Schottky junction photocathode delivers an onset potential of 0.41 V and a saturated photocurrent density of −32.5 mA cm−2 at 0 V (vs RHE) with excellent stability comparable to values reported for textured or nanostructured p‐Si photocathodes coated with ultrathin oxide layers by the conventional atomic layer deposition technique. These results suggest that the formation of graphene/Si Schottky junctions with a 3D architecture is a promising approach to improve the performance and durability of Si‐based photo‐electrochemical systems for water splitting or solar‐to‐fuel conversion.
This work demonstrates a novel 3D pyramid‐like graphene/p‐Si Schottky junction photocathode for H2 production based on the unique advantages of excellent carrier transport, high transparency, and superior corrosion protection of graphene. The formation of graphene/Si Schottky junctions with 3D architecture is a promising approach to improve the performance and durability of Si‐based photo‐electrochemical systems for water splitting or solar‐to‐fuel conversion.
In this study, we developed a simple approach, using a nanocavity structure, to increase the light absorption of graphene in an ultra-broadband and omnidirectional manner. We determined the light ...absorption of graphene by calculating the surface electric fields (E-fields) of various underlying substrates. Although the surface E-field was maximized for both one-dimensional photonic crystals and a metal/dielectric nanocavity structure, the much simpler two-layer nanocavity configuration also provided ultra-broadband and omnidirectional enhancement of absorption. By selecting a suitable metal as the back reflector and controlling the thickness of the single-layer dielectric spacer in the nanocavity structure, we found experimentally that the light absorption of graphene could be enhanced approximately fivefold, with full widths at half maximum of 200 nm in the ultraviolet, 400 nm in the visible, and greater than 1000 nm in the infrared regime. Moreover, we observed a significantly enhanced photo–heat response from the greater light absorption of graphene in the nanocavity structure. The absorbance spectrum of graphene in the nanocavity structure perfectly matched the air mass 1.5 solar spectrum, suggesting that such systems might be very useful for harvesting solar energy in optoelectronic devices.
In this study, we combine graphene with gold oxide (AuO x ), 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 x –graphene heterojunction. The large-area graphene covering the AuO x 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 x 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–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 x photodetector exhibited great flexibility and stability. Moreover, such vertical heterojunction-based graphene/AuO x photodetectors should be compatible with other transparent optoelectronic devices, suggesting applications in flexible and wearable optoelectronic technologies.
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