Zibo Li

Panchromatic plasmonic color patterns: from embedded Ag nanohole arrays to elevated Ag nanohole arrays

Plasmonic structural color is one of the most fascinating applications of recently fast developing plasmonics, which is a promising candidate technology for information processing, color displays and optical measurement devices. However, the implementation of plasmonic structural color in modern optical and spectral imaging systems demands strongly a simple fabrication process, low power consumption, and complex color pattern integration. Thus far, tuning of the plasmonic color has been generally achieved by morphology alteration or adjusting the lattice constants of plasmonic nanostructures. Nevertheless, this strategy suffers greatly from high cost and low throughput when designing complex color patterns. Herein, by precisely controlling the refractive indices on two sides of Ag nanohole arrays (NAs) that are embedded between a silica coating and a glass substrate, we are capable of filtering white light into individual colors across the entire visible band. Moreover, the straightforward strategy we propose is compatible with the traditional photolithography process, with which complex color patterns can be easily achieved. We further experimentally demonstrate that these engineered colored samples can be used as chromatically switchable anti-counterfeit tags. We anticipate that the method we demonstrate can provide a new approach for the fabrication of compact color filtering devices.

Tunable Polymer Brush/Au NPs Hybrid Plasmonic Arrays Based on Host−guest Interaction

The fabrication of versatile gold nanoparticle (Au NP) arrays with tunable optical properties by a novel host-guest interaction are presented. The gold nanoparticles were incorporated into polymer brushes by host-guest interaction between β-cyclodextrin (β-CD) ligand of gold nanoparticles and dimethylamino group of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA). The gold nanoparticle arrays were prepared through the template of PDMAEMA brush patterns which were fabricated combining colloidal lithography and surface-initiated atom-transfer radical polymerization (SI-ATRP). The structure parameters of gold nanoparticle patterns mediated by polymer brushes such as height, diameters, periods and distances, could be easily tuned by tailoring the etching time or size of colloidal spheres in the process of colloidal lithography. The change of optical properties induced by different gold nanoparticle structures was demonstrated. The direct utilization of PDMAEMA brushes as guest avoids a series of complicated modification process and the PDMAEMA brushes can be grafted on various substrates, which broaden its applications. The prepared gold naoparticle arrays are promising in applications of nanosensors, memory storage and surface enhanced spectroscopy.

The fabrication of long-range ordered nanocrescent structures based on colloidal lithography and parallel imprinting

A method for fabricating nanocrescent structures is presented based on a combination of colloidal lithography and parallel imprinting. In this process, non-close-packed colloidal spheres were prepared by a simple lift-up soft lithography technique, and subsequently the individual particles were used as shadow masks to angle deposit a layer of silver on the silicon substrates. Then, the silver-coated samples were etched to get silicon crescent nanohole arrays, which served as templates to mold patterned photocurable resin membranes. The patterned photocurable resin membranes were used to print gold nanocrescent nanostructures onto glass substrates. The size of the opening and the width of the gold nanostructures could be freely adjusted by changing the azimuth angle and tilt angle. Very importantly, the central angle of the nanocrescents could be adjusted in the range of 0°-360°. This method provides a low-cost and highly reproducible way to prepare complex nanostructure arrays for applications related to near field enhancement materials, optical sensors and surface-enhanced Raman spectroscopy, etc.

Tuning the bandgap of graphene quantum dots by gold nanoparticle-assisted O2 plasma etching

In this article, we report a feasible etching method to tune the bandgap of graphene quantum dots (GQDs). Since the bandgap in fluorescent carbon materials is dependent on the GQDs’ size and chemical composition, GQDs with different sizes have been fabricated using the corresponding gold nanoparticle arrays as etching masks. During the O2 etching process, the diameter of the GQDs decreased gradually accompanied by an increase in oxygen ratio. Femtosecond broadband transient absorption (TA) spectroscopy was used to investigate the variation trend in the bandgap of the GQDs. The present work affords an efficient route to investigate the photoluminescence (PL) mechanism of GQDs by tuning the size and surface chemical groups.

Wrinkled single-layer graphenes fabricated by silicon nanopillar arrays

The degree of crumpling affects the optoelectronic properties of graphene, which are very important for the performance of graphene-based devices and materials. In this article, we report an approach to tune the formation of wrinkles on single-layer graphene (SLG) by silicon nanopillar (SNP) arrays. By using gold nanoparticles as an etching mask, SNP arrays with different heights could be prepared by tuning the duration of etching. The formation of wrinkles on these SNP arrays was studied systematically. We found that thermal treatment could lead to a wrapping behavior of graphene around SNP arrays, which was accompanied by the emergence of many more wrinkles. Controllable wettability, conductivity and transmittance were demonstrated. This ability to tune wrinkles using SNP arrays can be employed to engineer the fabrication of graphene-related devices and other optoelectronic applications.