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This paper demonstrates femtosecond laser direct writing mediated flexible integration of plasmonic Ag/Pd alloy nanostructures that can be potentially used as a robust surface‐enhanced Raman spectroscopy substrate inside the microfluidic chip. Silver–palladium alloy with controllable composition ratio can be patterned into plasmonic nanostructures due to two‐photon absorption induced coreduction of silver/palladium double metal ions. Since the alloy structures can effectively protect the silver from oxidation, thus they can facilitate the stable on‐chip detection devices with long lifetime. The as‐fabricated silver–palladium alloy substrate with 18% content of palladium maintains a relatively high enhancement factor of about 2.62 × 108 while at the same time demonstrating the best stability against aerobic oxidation, as it is stable for up to 20 d under ambient aerobic conditions, exhibiting a significant improvement compared to those unprotected silver substrates which have a limited lifetime of only 3 or 4 d. [ABSTRACT FROM AUTHOR]

We theoretically investigated third harmonic generation (THG) from planar chiral metamaterials consisting of a square array of gammadion-shaped metal-insulatormetal multilayered nanostructures.We showthat there exists strong circular dichroism (CD) for THG on the proposed chiral metamaterials. We also demonstrate that geometrically mirroring the gammadion -shaped meta-atoms can result in reversal of the THG-CD effect. Based on theseCDeffects in the optical nonlinear regime, we propose a design of a Fresnel zone plate (FZP) for intense focusing of theTHGsignals, in which adjacent zones of the FZP consist of gammadions with mirror symmetry and generate circularly polarizedTHGwith opposite handedness. Furthermore, we demonstrate that the relative phase of the THG can be continuously changed by rotating the gammadion around its rotational axis, which could be used in the FZP to control the polarization of the output THG signals. [ABSTRACT FROM AUTHOR]

We present a design of multilayer core-shell nanostructures formed by introducing a dielectric gap shell layer between a silver core and a monolayer graphene shell for spectrally selective absorption enhancement in graphene based on an unconventional Fano effect. We demonstrate that this mechanism enables great flexibility in the choice of parameters of the proposed structures for the achievement of a relatively large and narrow-band absorption enhancement in graphene. Furthermore, we also demonstrate that such a spectrally selective absorption enhancement in graphene is highly tunable and can be optimized by controlling either the core or the shell parameters. These unique absorption properties may have applications in color-selective photodetectors and image sensors. [ABSTRACT FROM AUTHOR]

Using nanomaterials to develop multimodal systems has generated cutting-edge biomedical functions. Herein, we develop a simple chemical-vapor-deposition method to fabricate graphene-isolated-Au-nanocrystal (GIAN) nanostructures. A thin layer of graphene is precisely deposited on the surfaces of gold nanocrystals to enable unique capabilities. First, as surface-enhanced-Raman-scattering substrates, GIANs quench background fluorescence and reduce photocarbonization or photobleaching of analytes. Second, GIANs can be used for multimodal cell imaging by both Raman scattering and near-infrared (NIR) two-photon luminescence. Third, GIANs provide a platform for loading anticancer drugs such as doxorubicin (DOX) for therapy. Finally, their NIR absorption properties give GIANs photothermal therapeutic capability in combination with chemotherapy. Controlled release of DOX molecules from GIANs is achieved through NIR heating, significantly reducing the possibility of side effects in chemotherapy. The GIANs have high surface areas and stable thin shells, as well as unique optical and photothermal properties, making them promising nanostructures for biomedical applications. [ABSTRACT FROM AUTHOR]

In this paper, we report on the design and observation of double Fano resonances (DFRs) in an individual symmetry-reduced nanostructure and the induced high sensing sensitivity. Such a plasmonic nanostructure consists of a partially overlapped double-metallic nanotriangles with unequal sizes fabricated by using fast and low-cost angle-resolved nanosphere lithography. Symmetry breaking generates two narrow quadrupolar dark modes, which further enhance the coupling with fundamental bright dipole modes within the same structure, manifesting the effect of DFRs. The resonance wavelength and line shape of DFRs can be tailored by changing the degree of asymmetry as well as the size of the designed nanostructure. Based on DFRs, a high sensitivity to dielectric environment with a maximum figure of merit of 35 is measured. Due to a fast manufacturing process with high reproducibility and high structural tunability, the fabricated individual metallic nanostructure provides an opportunity for significant potential applications in localized surface plasmon resonance based single or double-wavelength sensors in the near-infrared region. [ABSTRACT FROM AUTHOR]

Technologicallycontrolling nanostructures is essential to tailoring the functionalitiesand properties of nanomaterials. Various methods free from lithography-basedtechniques have been employed to fabricate 2D nanostructures; howeverit is still hard to achieve a well interconnected 2D regular nanostructure.Here, we demonstrate a facile chemical solution method to self-assemblea regular and interconnected VO2nanonet on the wafer scale.The nanonet shows a well-defined 2D truss network constructed by VO2nanorods with twinning relationships. The growth directionand crystallographic orientation of nanorods are synchronously controlled,leading to horizontally epitaxial growth of nanorods along three symmetricdirections of the (001) single-crystal sapphire substrate. The uniquenanonets enable the acquisition of excellent resistance switchingproperties and dramatic fatigue endurance. A large resistance changeof near 5 orders with a 1.7 °C width of the hysteresis loop ischaracterized comparably to the properties of single crystals withoutdetectable degradation after 500 cycles over the metal-to-insulatortransition. It indicates that the nanonet can serve as an exceptionalcandidate for practical application in switching functional devices.Our findings offer a novel pathway for self-assembly of 2D orderednanostructures, which would provide new opportunities for the bottom-upintegration of nanodevices. [ABSTRACT FROM AUTHOR]