Youzhuan Zhang

Bioinspired colloidal photonic crystals with controllable wettability.

Because of the combinatorial advantage of their unique light manipulation properties and potential applications in novel optical devices, colloidal photonic crystals (PCs), the periodic arrangement of monodispersed latex spheres, have attracted interest from researchers. In particular, colloidal PCs exhibit structural colors based on interference effects within their periodic structures. The wavelength of these colors lies in the visible range, making them particularly attractive for a variety of applications. Colloidal PCs are extensively used in templating, catalysis, and chromatographic separations. Inspired by biological PCs with both structural color and specific wettability, researchers have fabricated colloidal PCs with controllable wettability as described in this Account. The wettability can be adjusted by the intrinsic roughness of colloidal crystals in combination with the tunable chemical composition of latex surfaces. Changes in the chemical composition of the latex surface under external stimuli, such as light, electricity, and heat, can reversibly control the wettability of PCs. Furthermore, the hierarchical structure of latex particles can effectively alter the water adhesive force of superhydrophobic colloidal PCs. Patterned PCs with a variety of wettabilities can be assembled using inkjet printing from well-designed latex suspensions. By combining their structural color and specific wettability, we also exemplify some of the promising applications of colloidal PCs as templates for the construction of hierarchical structures, as indicators for controllable transport of liquid droplets, and as color-based sensors for the monitoring changes in their environment. These findings offer innovative insights into the design of novel colloidal PCs and will be of great importance for further applications of these materials.

Fabrication of large-area patterned photonic crystals by ink-jet printing

Large-area patterned photonic crystals (PCs) with multi-stopbands were facilely fabricated by common ink-jet printers using polymer latex suspensions as inks.

Ultra-Fast Fabrication of Colloidal Photonic Crystals by Spray Coating

An ultra-fast fabrication of large-scale colloidal PCs via spray coating was demonstrated. The latex spheres with hydrophobic core and hydrophilic shell were designed, and the latex shell with abundant COOH groups resulted in strong hydrogen bonding interaction among latex spheres, which boosted latex arrangement during the spray procedure. The resultant samples with area of 7 × 12 cm(2) were easily fabricated within 1 min on different substrates. This ultra-fast fabrication procedure would be of great importance for the practical application of PCs for optic devices and functional coatings.

Closed-air induced composite wetting on hydrophilic ordered nanoporous anodic alumina

We investigate wetting behaviors of two kinds of hydrophilic ordered nanoporous anodic alumina (PAA). The water contact angle (CA) increases at first and subsequently decreases with increasing pore diameter of PAA with closed-pore structure, while the water CA decreases monotonously on PAA with open-pore structure. These interesting wetting behaviors are mainly due to the presence/absence of closed-air in the PAA. The closed-air could prevent water from entering into the nanopores. This work offers insight to control wetting by tailoring the surface nanostructure and will be significant for applications in printing, coating, etc.

Photonic crystal concentrator for efficient output of dye-sensitized solar cells

A facile approach to improve the output power of a dye-sensitized solar cell by more than 5 times has been developed by an optimum wavelength-selective photonic crystal concentrator.

Tough and Hydrophilic Photonic Crystals Obtained from Direct UV Irradiation

Tough and hydrophilic polystyrene (PS) photonic crystals (PCs) were obtained from direct UV irradiation. The irradiation procedure results in photochemical cross-linking of PS spheres, which leads to the enhanced mechanical strength of the PC films, without degrading the spectra quality of the PCs. Otherwise, the irradiation induces the formation of the carbonyl groups upon the latex surface, which changes the wettability of the films from hydrophobicity to high hydrophilicity. The results provide a facile and effective approach to fabricate functional PC films with high mechanical strength and special wettability, which will be of great importance for the practical application of PCs.

Fabrication of phase-change polymer colloidal photonic crystals

This paper presents the preparation of phase-change polymer colloidal photonic crystals (PCs) by assembling hollow latex spheres encapsulated with dodecanol for the first time. The monodispersed hollow latex spheres were obtained by phase reversion of monodispersed core-shell latex spheres in the n-hexane, which dissolves the PS core and retains the PMMA/PAA shell. The asprepared phase-change colloidal PCs show stable phase-change behavior. This fabrication of phase-change colloidal PCs would be significant for PCs applications in functional coatings and various optic devices.