Localized surface plasmon resonance (LSPR)-based sensing has found wide applications in medical diagnosis, food safety regulation and environmental monitoring. Compared with commercial propagating surface plasmon resonance (PSPR)-based sensors, LSPR ones are simple, cost-effective and suitable for measuring local refractive index changes. However, the figure of merit (FOM) values of LSPR sensors are generally 1-2 orders of magnitude smaller than those of PSPR ones, preventing the widespread use of LSPR sensors. Here we describe an array of submicrometer gold mushrooms with a FOM reaching B108, which is comparable to the theoretically predicted upper limit for standard PSPR sensors. Such a high FOM arises from the interference between Wood's anomaly and the LSPRs. We further demonstrate the array as a biosensor for detecting cytochrome c and alpha-fetoprotein, with their detection limits down to 200 pM and 15 ng ml À 1 , respectively, suggesting that the array is a promising candidate for label-free biomedical sensing.

Noble metal nanostructures, especially gold nanocrystals, have attracted intensive interest due to their rich plasmonic properties and enormous potential technological applications. The preparation process of gold nanocrystals can strongly affect their plasmonic properties and therefore their performances in various applications. Chemically synthesized colloidal gold nanocrystals are usually employed in biomedical fields, while lithographically fabricated ones are highly preferred for constructing optical meta-structures. A detailed careful comparison of the plasmonic performances between lithographical and chemical metal nanostructures is strongly desired for using them for different applications. Herein, we experimentally measured and quantitatively compared the plasmonic properties, including longitudinal localized surface plasmon wavelengths (LLSPWs) and plasmon peak widths, scattering intensities, and local electric field enhancements, of lithographically fabricated and chemically grown gold nanorods. The lithographical nanorods exhibit much weaker scattering, largely broadened spectral widths, and considerably reduced electric field enhancements. Electrodynamic simulations suggest that the reduction in the plasmonic performance of the lithographical nanorods is caused mainly by the use of an adhesive metal layer and slightly by their polycrystalline nature. Our quantitative comparison results will be very helpful in guiding the selection of proper types of metal nanostructures for targeted technological applications.

Carbon nanoparticles (CNPs) are grown on flexible carbon fabric via a simple and low‐cost flame synthesis process. The entire struture of the carbon fabric substrate retains its high flexibility after the growth of CNPs and can even be rolled‐up and twisted to a large degree without affecting the electric characteristics. No appreciable changes in the conductance can be observed under different bending curvatures after hundreds of bending cycles. The thermal conductivity of the carbon fabric with CNPs is about 2.34 W m−1 K−1, about one order of magnitude higher than that of most polymer substrates. The field emitter fabricated using the structure has a low threshold electric field of around 2.8 V μm−1, and a high field emission current density of 108 mA cm−2, which is about two to four orders of magnitude higher than that of most polymer substrate‐based flexible CNT field emitters. These results indicate that CNPs on carbon fabric have potential applications in flexible electronics devices and displays.

We report a systematic study about the anisotropic third-order optical nonlinearity of a single ZnO micro/nanowire by using the Z-scan method with a femtosecond laser. The two-photon absorption coefficient and nonlinear refraction index, which are measured as a function of polarization angle and sample orientation angle, exhibit oscillation curves with a period of π/2, indicating a highly polarized optical nonlinearity of the ZnO micro/nanowire. Further studies show that the polarized optical nonlinearity of the ZnO micro/nanowire is highly size-dependent. The results indicate that ZnO nanowire has great potential in applications of nanolasers, all-optical switching and polarizationsensitive photodetectors.

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