Received 17 January 2007; accepted 4 April 2007The role of surface plasmon in second harmonic generation from arrays of gold nanorod particlesexcited by femtosecond laser pulses is investigated as a function of incident light polarization andirradiation wavelength. In addition to photoluminescence, a peak of second harmonic is observedand is found to depend on the polarization and wavelength of the fundamental frequency laser beam.In particular, the authors found similarities between extinction spectra of the nanoparticles andspectra of emmitted second harmonic. This behavior can be explained by resonant excitation oflocalized surface plasmon resonances. ©

PROOF COPY 108717APL Role of surface plasmon in second harmonic generation from gold nanorods

The environmental concerns in the current century is not only limited to the polluting effect of the fossil fuel consumption but also the recycling challenges of waste turns to be a substantial challenges of the industry. Recycling of colored discarded materials is very difficult because of the problems in relation to the dissociation of diverse chemical compounds present in the colorant agents. Single or double component materials which could create various colors by geometrical changes can be a great solution to the mentioned limitations. Metasurfaces’ and metamaterials’ structural color therefore draws attention as they enable generation of vivid colors only by geometrical arrangement of metals which not only ease the recycling but at the same time enhance the mechanical stability of the colors. In this review, the progress in the field of plasmonic metasurface- and metamaterial-based structural colors is reviewed.

Review of Metasurface Plasmonic Structural Color

In this paper, Au modified ZnO (Au/ZnO) nanosheets with high humidity performance were prepared by hydrothermal method. The position and the energy band of Au atoms in ZnO single crystals were simulated by first-principles based on density-functional theory (DFT), and the mechanism of Au/ZnO humidity sensors was studied further. The calculations show that Au atoms are adsorbed on the surface of ZnO supercell to provied more oxygen vacancies. Therefore, more water molecules can be adsorbed on the Au/ZnO humidity sensor to react with more electrons and hence to enhance the performance of the humidity sensor. Experiments show that the performance of humidity sensor based on Au/ZnO can be improved by changing the concentration of the modifier Au nanoparticles. Au/ZnO (0.5 mM HAuCl4) humidity sensor exhibits approximately 5 orders of magnitude variation in impedance realization with RH in a range from 11% to 95%, and it exhibits good linearity and narrow hysteresis loop (˜3.0%), as well as short response (16 s) time and recovery time (28 s). The performance of Au/ZnO humidity can be improved by modifier Au nanoparticles, because the Au/ZnO have more surface oxygen defects and special electronic storage capabilities. These results indicate that Au/ZnO nanosheets have a potential in the manufacture of humidity sensors and provide a new idea for high performance of ZnO humidity sensors.

Investigation of humidity sensor based on Au modified ZnO nanosheets via hydrothermal method and first principle

Ascendant bioinspired antireflective materials: Opportunities and challenges coexist

Localized surface plasmon resonance-based plasmonic biosensors are interesting candidates for the design of portable optical biosensor platforms owing to their integration, miniaturization, multiparameter, real-time, and label-free detection characteristics. Plasmonic biosensor arrays that have been combined with microfluidics have been developed herein to detect exosomes label-free. Gold nano-ellipsoid arrays were fabricated with low-cost anodic aluminum oxide thin films that act as shadow masks for evaporation of Au. The nano-ellipsoid arrays were integrated with a microfluidic chip to achieve multiparameter detection. The anti-CD63 antibody that is specific to the exosome transmembrane protein CD63 is modified on the surface of the nano-ellipsoids. Exosome samples were injected into the biosensor platform at different concentrations and detected successfully. The detection limit was 1 ng/mL. The proposed plasmonic biosensor array can be universally applicable for the detection of other biomarkers by simply changing the antibody on the surface of the Au nano-ellipsoids. Moreover, this biosensor platform is envisaged to be potentially useful in the development of low-cost plasmonic-based biosensors for biomarker detection and for the investigation of exosomes for noninvasive disease diagnoses.

Label-Free Exosome Detection Based on a Low-Cost Plasmonic Biosensor Array Integrated with Microfluidics.

Processing study of SU-8 pillar profiles with high aspect ratio by electron-beam lithography

We report our work on the development of subwavelength gold pillar arrays as local surface plasmonic (LSP) resonators for sensor applications. These arrays are fabricated by electron beam lithography combined with electroplating. The conical shape, instead of flat one, on the top of Au pillars, induced by uneven current density in the plating, may affect the LSP resonance (LSPR). This paper aims to carry out a systematic study of LSPR behavior in nanopillar arrays with both flat and conical shapes on the top, trying to prove the feasibility of the developed nanoprocess. Both numerical simulations by the finite-difference time-domain (FDTD) method and experimental characterization on fabricated LSP resonators for reflectance spectra were carried out. Our experiments indicate that the fabricated nanopillar arrays in Au demonstrate the promising capability of refractive index sensing with sensitivity of 270 nm/refractive index unit. FDTD simulation of electric field density in the gap between pillars reveals the correlation between the resonant absorption of the incident light and the standing waves of localized surface plasmon polaritons in the gaps of the pillar array, despite the conical shape of the pillars. Moreover, it was discovered that the resonant absorption becomes stronger when the light incident angle is increased. The proposed nanoprocess for pillar arrays should possess great prospects for manufacturing Au pillars with high aspect ratio for achieving higher sensitivity at an economical cost.

Gold nanopillar arrays as biosensors fabricated by electron beam lithography combined with electroplating

Ultra-tall sub-wavelength gold nano pillars for high sensitive LSPR sensors

For acquiring high-contrast and high-brightness images in hard-x-ray optics, Fresnel zone plates with high aspect ratios (zone height/zone width) have been constantly pursued. However, knowledge of aspect ratio limits remains limited. This work explores the achievable aspect ratio limit in polymethyl methacrylate (PMMA) by electron-beam lithography (EBL) under 100 keV, and investigates the lithographic factors for this limitation. Both Monte Carlo simulation and EBL on thick PMMA are applied to investigate the profile evolution with exposure doses over 100 nm wide dense zones. A high-resolution scanning electron microscope at low acceleration mode for charging free is applied to characterize the resultant zone profiles. It was discovered for what we believe is the first time that the primary electron-beam spreading in PMMA and the proximity effect due to extra exposure from neighboring areas could be the major causes of limiting the aspect ratio. Using the optimized lithography condition, a 100 nm zone plate with aspect ratio of 15/1 was fabricated and its focusing property was characterized at the Shanghai Synchrotron Radiation Facility. The aspect ratio limit found in this work should be extremely useful for guiding further technical development in nanofabrication of high-quality Fresnel zone plates.

Simulation and experimental study of aspect ratio limitation in Fresnel zone plates for hard-x-ray optics.

In this paper, we propose a new form of nanostructures with Al film deposited on a patterned dielectric material for generating structural color, which is induced by local surface plasmonic resonant (LSPR) absorption in sub-wavelength-indented hole/ring arrays. Unlike other reported results obtained by using focus ion beam (FIB) to create metallic nanostructures, the nano-sized hole/ring arrays in Al film in this work are replicated by high resolution electron beam lithography (EBL) combined with self-aligned metallization. Clear structural color is observed and systematically studied by numerical simulations as well as optical characterizations. The central color is strongly related to the geometric size, which provides us with good opportunities to dye the colorless Al surface by controlling the hole/ring dimensions (both diameter and radius), and to open up broad applications in display, jewelry decoration, green production of packing papers, security code, and counterfeits prevention.

https://iopscience.iop.org/article/10.1088/1674-1056/24/8/080702/pdf

Yaqi Ma

Papers

Processing study of SU-8 pillar profiles with high aspect ratio by electron-beam lithography

Gold nanopillar arrays as biosensors fabricated by electron beam lithography combined with electroplating

Ultra-tall sub-wavelength gold nano pillars for high sensitive LSPR sensors

Simulation and experimental study of aspect ratio limitation in Fresnel zone plates for hard-x-ray optics.

Design and fabrication of structural color by local surface plasmonic meta-molecules*