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The transition metal dichalcogenides (TMDs) have drawn great research attention, motivated by the derived remarkable optoelectronic properties and the potentials for high-efficient excitonic devices. The plasmonic nanocavity, integrating deep-sub wavelength confinement of optical mode with dramatic localized field enhancement, provides a practical platform to manipulate light–matter interaction. In order to obtain strong exciton–plasmon coupling effects, it’s crucial to match the vibration direction of exciton to the available strong localized in-plane electric field. Herein, we demonstrate the coupling effect of in-plane exciton in monolayer tungsten diselenide (WSe2) to deterministic gap-plasmon field which is produced by nanometrically gapped collapsed nanofingers. The gap-plasmon field which is completely parallel to the in-plane excitons in WSe2 will drive a strong exciton–plasmon coupling at room temperature. More interestingly, it is experimentally observed that the luminescence of exciton–polariton cannot be influenced by the temperature in the range from 77 K to 300 K due to the presence of nanofingers. According to the theoretical analysis results, we attribute this finding to the dielectric screening effect arising from the extremely strong localized electric field of plasmonic nanofingers. This work proposes a feasible way to harness and manipulate the exciton of low-dimensional semiconductor, which might be potential for quantum optoelectronics.

Higher-order topological insulators have drawn great research attention in nanophotonics due to their ability to both support robust edge states and lower dimensional corner states. In this work, we present a theoretical proposal for achieving topologically switchable and valley-selective corner states based on two-dimensional C3-symmetric photonic crystals (PCs), with breaking of inversion symmetry. Through the concatenation of two valley PCs with contrasting topological indices, we demonstrate the emergence of two types of valley-locked chiral topological edge states resulting from the valley–valley interaction. More importantly, we find that the system exhibits two distinct types of corner states, characterized by strong robustness and high localization, when the PCs are spliced at a 60° angle. However, the corner states are absent when the splicing angle is set as 120°. According to the theoretical analysis, the selective activation of topological valley corner states is related to the sign flip of valley Chern number at the corner. Based on this feature, we further propose a topological photonic switching device, in which the corner can be lighted up or off selectively. By combining the benefits of higher-order topology and valley degree of freedom, our work provides an efficient and flexible method for light manipulation. [ABSTRACT FROM AUTHOR]

All‐inorganic perovskites have recently drawn considerable attention due to their excellent optoelectronic properties. With the help of gap‐plasmon nanostructures, the optical properties of perovskites can be tuned through the coupled near‐field. Here, the optical coupling between CsPbBr3 quantum dots (QDs) and gap‐plasmon through placing QDs in a 2‐nm tetrahedral amorphous carbon gap region of collapsible Ag nanofingers is demonstrated. Compared to the CsPbBr3 QDs on SiO2, the photoluminescence (PL) of CsPbBr3 QDs on collapsed nanofinger is enhanced by 4 times and the lifetime decreases from 11.04 to 3.8 ns. A Purcell‐enhanced emission can be achieved by combining QDs and plasmonic nanofingers. In addition, the intensity of PL can be manipulated by the polarization of incident light because of the different polarization responses of dimer nanofingers. More importantly, PL intensity shows a quadric dependence on the incident power and lasing‐like PL spectra can be observed at room temperature by continuous‐wave laser excitation. Such observations can be ascribed to the strong coupling between CsPbBr3 QDs and surrounding Ag nanofingers. This finding indicates that it is possible to achieve lasing‐like PL through coupling CsPbBr3 QDs to the near‐field of plasmonic nanostructures, which can enrich the applications of CsPbBr3 QDs in nanolasing devices. [ABSTRACT FROM AUTHOR]

Surface‐enhanced Raman spectroscopy (SERS) is known as a powerful technique to provide label‐free analyses for chemical sensing. While the sensitivity of SERS is heavily dependent on the prepared SERS functional substrates, finding appropriate substrates is critical to achieve sufficient signal enhancement. Meanwhile, the capture of targets to such effective enhancing region becomes challenging especially for low concentration. Here, we report a coupled Au/DNAs/Au gap plasmon platform that provides remarkable SERS enhancement and sensitivity for mercury ion sensing. Through nanoimprint lithography, large area of Au nanofingers can be fabricated with excellent uniformity and flexibility. These Au nanofingers can be further modified by DNA aptamers to construct Au/DNAs/Au gap plasmon nanostructures with well‐defined gap sizes. Due to the subnanometer gap size, strong interaction between collapsed Au nanofingers can be induced to create extremely enhanced near‐field with nanoscale mode volume. When Hg2+ ions exist around the platform, they can specially bind to thymine (T) bases of DNA and form T‐Hg2+‐T pairs between adjacent single strand DNAs. As a result, DNAs that initially lie on the Au surface are forced to stand in rigid duplex‐structures. This morphology change can be directly indicated by the ratio between adenine (A) and guanine (G) SERS signals to reveal the Hg2+ concentration. Given the strong field enhancement as well as the close distance between DNA and hotspot, ultralow Hg2+ concentration down to 10−9 M is successfully detected. This work demonstrates a SERS platform with high selectivity and sensitivity, which exhibits significant potential for molecule sensing applications. [ABSTRACT FROM AUTHOR]

The transition metal dichalcogenides (TMDs) have drawn great research attention, motivated by the derived remarkable optoelectronic properties and the potentials for high-efficient excitonic devices. The plasmonic nanocavity, integrating deep-sub wavelength confinement of optical mode with dramatic localized field enhancement, provides a practical platform to manipulate light–matter interaction. In order to obtain strong exciton–plasmon coupling effects, it's crucial to match the vibration direction of exciton to the available strong localized in-plane electric field. Herein, we demonstrate the coupling effect of in-plane exciton in monolayer tungsten diselenide (WSe2) to deterministic gap-plasmon field which is produced by nanometrically gapped collapsed nanofingers. The gap-plasmon field which is completely parallel to the in-plane excitons in WSe2 will drive a strong exciton–plasmon coupling at room temperature. More interestingly, it is experimentally observed that the luminescence of exciton–polariton cannot be influenced by the temperature in the range from 77 K to 300 K due to the presence of nanofingers. According to the theoretical analysis results, we attribute this finding to the dielectric screening effect arising from the extremely strong localized electric field of plasmonic nanofingers. This work proposes a feasible way to harness and manipulate the exciton of low-dimensional semiconductor, which might be potential for quantum optoelectronics. [ABSTRACT FROM AUTHOR]

ABSTRACT: To evaluate the effects of intraarticular injections of autologous platelet‐rich plasma (PRP) or bone marrow concentrate (BMC) on osteoarthritis (OA), 24 adult goats were equally divided into control (Ctrl), saline (NS), PRP, and BMC groups, and OA was induced by surgery in NS, PRP, and BMC groups. Autologous PRP and BMC were obtained from whole blood and bone marrow aspirates, respectively. The data revealed, platelets were increased in BMC by 1.8‐fold, monocytes by 5.6‐fold, TGF‐β1 by 7.7‐fold, and IGF‐1 by 3.6‐fold (p < 0.05), and platelets were increased in PRP by 2.9‐fold, and TGF‐β1 by 3.3‐fold (p < 0.05). From the sixth week post‐operation, saline, PRP, and BMC were administered by intraarticular injection once every 4 weeks, three consecutive times. After the animals were sacrificed, inflammatory cytokines in the synovial fluid was measured, and bone and cartilage degeneration progression was observed by macroscopy, histology, and immunohistochemistry. Compared with the NS group, the level of inflammatory cytokines was reduced in the PRP and BMC groups (p < 0.05). Histologically, delayed cartilage degeneration and higher levels of extracellular matrix (ECM) were observed in both PRP and BMC treated groups (p < 0.05). Furthermore, the BMC group showed greater cartilage protection and less ECM loss than the PRP group (p < 0.05). In summary, this study showed that intraarticular injection of autologous PRP and BMC has therapeutic efficacy in a goat osteoarthritis model, with the greater benefit in terms of cartilage protection being observed in the BMC‐treated group than PRP. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2140–2146, 2018. [ABSTRACT FROM AUTHOR]

Plasmonic nanostructures exhibit intriguing optical properties due to spectrally selective plasmon resonance and thus have broad applications, including biochemical sensing and photoelectric detections. However, excited plasmons are often strongly influenced by the substrates supporting the metallic nanostructures, which not only weakens the intrinsic plasmon coupling effect, but also results in a great reduction of optical near‐field enhancement. Here, a plasmonic nanostructure combining collapsible Au‐nanofingers with selective‐etching that enables Au to be suspended is demonstrated, thus avoiding the undesirable influence of the substrates on the local near‐field distribution and forming symmetric electromagnetic‐field enhancements at both the top and bottom surfaces. The polymer support of the Au‐nanofingers is selectively etched by oxygen plasma, while the Au‐cap retains its original size. After an ultrathin dielectric coating is applied on the Au‐nanofingers, suspended Au‐caps with extremely small dielectric gaps are formed via the collapse of neighboring Au‐nanofingers by exposing them to ethanol. These nanostructures can provide a surface‐enhanced Raman scattering (SERS) enhancement of up to ≈109, which is nearly twice that in the nonsuspended system. As a highly active SERS substrate, the label‐free detection of low‐concentration harmful plastic phthalates in a child's urine without any pretreatment is successfully demonstrated, which suggests that this method is suitable for medical prediagnosis. [ABSTRACT FROM AUTHOR]