Substrate-mediated plasmon hybridization toward high-performance light trapping.

High-performance light trapping in metamaterials and metasurfaces offers prospects for the integration of multifunctional photonic components at subwavelength scales. However, constructing these nanodevices with reduced optical losses remains an open challenge in nanophotonics. Herein, we design and fabricate aluminum-shell-dielectric gratings by integrating low-loss aluminum materials with metal-dielectric-metal designs for high-performance light trapping featuring nearly perfect light absorption with broadband and large angular tuning ranges. The mechanism governing these phenomena is identified as the occurrence of substrate-mediated plasmon hybridization that allows energy trapping and redistribution in engineered substrates. Furthermore, we strive to develop an ultrasensitive nonlinear optical method, namely, plasmon-enhanced second-harmonic generation (PESHG), to quantify the energy transfer from metal to dielectric components. Our studies may provide a mechanism for expanding the potential of aluminum-based systems in practical applications.

Nonlinear light amplification via 3D plasmonic nanocavities.

Plasmonic nanocavities offer prospects for the amplification of inherently weak nonlinear responses at subwavelength scales. However, constructing these nanocavities with tunable modal volumes and reduced optical losses remains an open challenge in the development of nonlinear nanophotonics. Herein, we design and fabricate three-dimensional (3D) metal-dielectric-metal (MDM) plasmonic nanocavities that are capable of amplifying second-harmonic lights by up to three orders of magnitude with respect to dielectric-metal counterparts. In combination with experimental estimations of quantitative contributions of constituent parts in proposed 3D MDM designs, we further theoretically disclose the mechanism governing this signal amplification. We discover that this phenomenon can be attributed to the plasmon hybridization of both dipolar plasmon resonances and gap cavity resonances, such that an energy exchange channel can be attained and helps expand modal volumes while maintaining strong field localizations. Our results may advance the understanding of efficient nonlinear harmonic generations in 3D plasmonic nanostructures.

Expression of miR-187 and miR-509-3p in serum of primary hepatocellular carcinoma patients and its evaluation of prognosis.

PURPOSE: Hepatocellular carcinoma (HCC) is a histological type of primary liver cancer, with high recurrence and mortality rates worldwide. At the moment, there are no diagnostic and prognostic markers. microRNAs (miRs) are short-chain non-coding RNAs, and play a vital role in tumor diagnosis and prognosis. METHODS: The miR-187 and miR-509-3p expression in primary HCC was evaluated via qRT-PCR and starBase, and the diagnostic and prognostic values were analyzed via receiver operating characteristic (ROC) curve and Kaplan-Meier method. RESULTS: qRT-PCR and starBase analysis showed that the miR-187 expression was low in the tissues and serum of primary HCC patients, while that of miR-509-3p increased. ROC analysis manifested that the area under the curves (AUCs) of miR-187 and miR-509-3p in primary HCC were 0.842 and 0.866, respectively, and that of joint diagnosis was > 0.9. The 5-year survival rates of miR-187 low expression group and miR-509-3p high expression group decreased markedly. Cox regression analysis identified that pathological differentiation, clinical stage and miR-187 were independent prognostic factors of primary HCC patients. CONCLUSION: miR-187 and miR-509-3p.

Quasi-Bragg plasmon modes for highly efficient plasmon-enhanced second-harmonic generation at near-ultraviolet frequencies.

Boosting nonlinear frequency conversions with plasmonic nanostructures at near-ultraviolet (UV) frequencies remains a great challenge in nano-optics. Here we experimentally design and fabricate a plasmon-enhanced second-harmonic generation (PESHG) platform suitable for near-UV frequencies by integrating aluminum materials with grating configurations involved in structural heterogeneity. The SHG emission on the proposed platform can be amplified by up to three orders of magnitude with respect to unpatterned systems. Furthermore, the mechanism governing this amplification is identified as the occurrence of quasi-Bragg plasmon modes near second-harmonic wavelengths, such that a well-defined coherent interplay can be attained within the hot spot region and facilitate the efficient out-coupling of local second-harmonic lights to the far-field. Our work sheds light into the understanding of the role of grating-coupled surface plasmon resonances played in PESHG processes, and should pave an avenue toward UV nanosource and nonlinear metasurface applications.

Multiband enhanced second-harmonic generation via plasmon hybridization.

Boosting nonlinear frequency-conversion efficiencies in hybrid metal-dielectric nanostructures generally requires the enhancement of optical fields that interact constructively with nonlinear dielectrics. Inevitably for localized surface plasmons, spectra subject to this enhancement tend to span narrowly. As a result, because of the spectral mismatch of resonant modes at frequencies participating in nonlinear optical processes, strong nonlinear signal generations endure the disadvantage of rapid degradations. Here, we experimentally design a multiband enhanced second-harmonic generation platform of three-dimensional metal-dielectric-metal nanocavities that consist of thin ZnO films integrated with silver mushroom arrays. Varying geometric parameters, we demonstrate that the introduction of ZnO materials in intracavity regions enables us to modulate fundamental-frequency-related resonant modes, resulting in strong coupling induced plasmon hybridization between localized and propagating surface plasmons. Meanwhile, ZnO materials can also serve as an efficient nonlinear dielectric, which provides a potential to obtain a well-defined coherent interplay between hybridized resonant modes and nonlinear susceptibilities of dielectric materials at multi-frequency. Finally, not only is the conversion efficiency of ZnO materials increased by almost two orders of magnitude with respect to hybrid un-pattered systems at several wavelengths over a 100-nm spectral range but also a hybrid plasmon-light coupling scheme in three-dimensional nanostructures can be developed.

A new demethyl abietane diterpenoid from the roots of Tripterygium wilfordii.

A new demethyl abietane diterpenoid, Triptotin K (3) together with three known compounds, friedelin (1), canophyllal (2), and triptonoterpene (4) were isolated from the roots of Tripterygium wilfordii Hook. f. by silica gel column and preparative high performance liquid chromatography. Their structures were determined by extensive NMR data and mass spectroscopic analysis. Triptotin K showed cytotoxic activities against KB, KBv200, HepG2, and MCF-7/ADM cells lines with IC50 values of 29.88, 36.50, 39.55, and 41.38 µM, respectively.

Ethyl lucidenates A reverses P-glycoprotein mediated vincristine resistance in K562/A02 cells.

Multidrug resistance is a major unresolved obstacle to successful cancer chemotherapy. It is often associated with an elevated efflux of a variety of anticancer drugs by ATP-binding cassette transporters including P-glycoprotein, BCRP and MRP1. In this study, the reversal effect of Ethyl lucidenates A on K562/A02 cells was investigated. At concentrations of 10 µM, Ethyl lucidenates A could reverse the resistance of K562/A02 to vincristine up to 7.59 folds. Mechanistically, Ethyl lucidenates A could increase the intracellular accumulation of vincristine in K562/A02 cells through inhibiting the P-glycoprotein mediated drug-transport activity by rhodamine accumulation assay and cell cycle analysis. Further mechanistic investigation found that Ethyl lucidenates A did not alter P-glycoprotein expression. In conclusion, Ethyl lucidenates A could reverse the multidrug resistance of K562/A02 cells via its influence on P-glycoprotein drug-transport activity and thus, be a potential multidrug resistance reversal agent.

Spatially-Controllable Hot Spots for Plasmon-Enhanced Second-Harmonic Generation in AgNP-ZnO Nanocavity Arrays.

Plasmon-enhanced second-harmonic generation (PESHG) based on hybrid metal-dielectric nanostructures have extraordinary importance for developing efficient nanoscale nonlinear sources, which pave the way for new applications in photonic circuitry, quantum optics, and biosensors. However, the relatively high loss of excitation energies and the low spatial overlapping between the locally enhanced electromagnetic field and nonlinear materials still limit the promotion of nonlinear conversion performances in such hybrid systems. Here, we design and fabricate an array of silver nanoparticle-ZnO (AgNP-ZnO) nanocavities to serve as an efficient PESHG platform. The geometry of AgNP-ZnO nanocavity arrays provides a way to flexibly modulate hot spots in three-dimensional space, and to achieve a good mutual overlap of hot spots and ZnO material layers for realizing efficient SH photon generation originating from ZnO nanocavities. Compared to bare ZnO nanocavity arrays, the resulting hybrid AgNP-ZnO design of nanocavities reaches the maximum PESHG enhancement by a factor of approximately 31. Validated by simulations, we can further interpret the relative contribution of fundamental and harmonic modes to Ag-NP dependent PESHG performances, and reveal that the enhancement stems from the co-cooperation effect of plasmon-resonant enhancements both for fundamental and harmonic frequencies. Our findings offer a previously unreported method for designing efficient PESHG systems and pave a way for further understanding of a surface plasmon-coupled second-order emission mechanism for the enhancement of hybrid systems.

Plasmon-enhanced second-harmonic generation from hybrid ZnO-covered silver-bowl array.

High-efficient, plasmon-enhanced nonlinear phenomena based on hybrid nanostructures, which combine nonlinear dielectrics with plasmonic metals, are of fundamental importance for various applications ranging from all-optical switching to imaging or bio-sensing. However, the high loss of the excitation energy in nanostructures and the poor spatial overlap between the plasmon enhancement and the bulk of nonlinear materials largely limit the operation of plasmon-enhanced nonlinear effects, resulting in low nonlinear conversion efficiency. Here, we design and fabricate a ZnO-covered, 2D silver-bowl array, which can serve as an efficient platform for plasmon-enhanced second-harmonic generation (PESHG). Validated by experiments and simulations, we demonstrate that the high spatial overlap between the near-field enhancement and the ZnO film plays the key role for this nanostructure-based PESHG process. The enhancement mainly originates from the fundamental wavelength-derived plasmon resonance, providing an enhancement factor of approximately 33 times. These results achieved pave the way for future applications, which require localized light sources at nanoscale.

Origin of the Avalanche-Like Photoluminescence from Metallic Nanowires.

Surface plasmonic systems provide extremely efficient ways to modulate light-matter interaction in photon emission, light harvesting, energy conversion and transferring, etc. Various surface plasmon enhanced luminescent behaviors have been observed and investigated in these systems. But the origin of an avalanche-like photoluminescence, which was firstly reported in 2007 from Au and subsequently from Ag nanowire arrays/monomers, is still not clear. Here we show, based on systematic investigations including the excitation power/time related photoluminescent measurements as well as calculations, that this avalanche-like photoluminescence is in fact a result of surface plasmon assisted thermal radiation. Nearly all of the related observations could be perfectly interpreted with this concept. Our finding is crucial for understanding the surface plasmon mediated thermal and photoemission behaviors in plasmonic structures, which is of great importance in designing functional plasmonic devices.

Plasmon-Enhanced Second-Harmonic Generation Nanorulers with Ultrahigh Sensitivities.

Attainment of spatial resolutions far below diffraction limits by means of optical methods constitutes a challenging task. Here, we design nonlinear nanorulers that are capable of accomplishing approximately 1 nm resolutions by utilizing the mechanism of plasmon-enhanced second-harmonic generation (PESHG). Through introducing Au@SiO2 (core@shell) shell-isolated nanoparticles, we strive to maneuver electric-field-related gap modes such that a reliable relationship between PESHG responses and gap sizes, represented by "PESHG nanoruler equation", can be obtained. Additionally validated by both experiments and simulations, we have transferred "hot spots" to the film-nanoparticle-gap region, ensuring that retrieved PESHG emissions nearly exclusively originate from this region and are significantly amplified. The PESHG nanoruler can be potentially developed as an ultrasensitive optical method for measuring nanoscale distances with higher spectral accuracies and signal-to-noise ratios.