Likui Wang

Titanium Oxide/Silicon Moth-Eye Structures with Antireflection, p–n Heterojunctions, and Superhydrophilicity

By employing KOH etching of silicon and hydrothermal growth of titanium oxide (TiO2), TiO2 nanorods assembled on the silicon micropyramids to form biomimetic composite coating, similar to moth-eye structures. The biomimetic composite coating possessed not only the micro-nano hierarchical structures but also the p-n heterojunctions, resulting in a decrease in the reflection of incident light and an increase in the separation efficiency of photogenerated carriers. Meanwhile, the structures showed excellent superhydrophilicity, making for the self-cleaning of the material surface. We further demonstrate that by exploiting the advantages of this method, the application of such structures in the photocatalysis field is thus straightforward.

Functional polyaniline-assisted decoration of polystyrene microspheres with noble metal nanoparticles and their enhanced catalytic properties

The use of polystyrene (PS) microsphere modified by polyaniline (PANi) as a functional support for Au nanoparticles (NPs) is described herein. Specifically, a simple strategy, involving swelling followed by diffusion and interfacial polymerization of aniline monomer, was applied to fabricate the PS/PANi composite particles, independent of any surface treatments of the PS seed microspheres. At mildly acidic pH, the surface of PANi was enriched with positive charge, hence enabling the negatively charged Au NPs (stabilized by trisodium citrate) to be uniformly attached onto the PS/PANi composite particles via a simple electrostatic self-assembly approach. The prepared PS/PANi-Au composite particles exhibit high catalytic activity and superior reusability in the reduction of p-nitrophenol using NaBH4. Notably, this type of self-assembly could not only effectively control the density of the supported Au NPs with different sizes but could also easily immobilize other noble metal (Ag, Pt, and Pd) NPs onto the surface of the PS/PANi composite particles. More significantly, in addition to providing anchoring sites for immobilizing noble metal NPs, the PANi coating also contributes to the higher catalytic activity of PS/PANi-Au composite particles due to the synergistic effect of PANi and Au NPs.

Facile fabrication of PS/Fe3O4@PANi nanocomposite particles and their application for the effective removal of Cu2+

This work presents a simple and straightforward approach to fabricating multifunctional nanocomposite particles which possess a core of a polystyrene (PS) particle, a transition layer of magnetic Fe3O4 nanoparticles (NPs), and an outer shell of adsorbable polyaniline (PANi). In detail, the positively charged Fe3O4 NPs synthesized via the chemical co-precipitation method are directly loaded onto the negatively charged surfaces of the PS particles obtained by emulsifier-free emulsion polymerization through electrostatic self-assembly; subsequently, the coating of the resultant PS/Fe3O4 nanocomposite particles with PANi was successfully achieved by virtue of the “swelling–diffusion–interfacial-polymerization method” (SDIPM). Furthermore, the adsorption of Cu2+ by PS/Fe3O4@PANi nanocomposite particles was investigated by changing the initial pH value, adsorption time, and initial concentration of the adsorbate. The adsorption data in our work follow a pseudo-second-order kinetics model and fit the Langmuir isotherm model. The PS/Fe3O4@PANi nanocomposite particles show that the maximum adsorption capacity is up to 181.5 mg g−1 at pH 5. More importantly, these nanocomposite particles can be easily recovered using an external magnetic field owing to the presence of Fe3O4 NPs, and the regenerated nanocomposite particles can be repeatedly used for eight cycles without significant loss of their adsorption capacity.

Micro-nano fabrication of hierarchical PPy/TiO2/Si by continuous self-assembly technology

ABSTRACT Combining TiO2 with conducting polymer could enhance the photoelectric transformation efficiency of absorbed light, due to the formation of P-N heterojunctions. However, few people considered to increase the adsorption efficiency of incident light for the composites. In this manuscript, we demonstrate a facile approach of sequentially assembling TiO2 nanorods and polypyrrole (PPy) on the monocrystalline silicon wafer by the method of hydrothermal synthesis and chemical oxidation. The PPy/TiO2/Si composites with hierarchical structures possessed broadband antireflection and dual P-N heterojunctions, enhancing not only the incident light absorption efficiency but also the utilization efficiency of absorbed light. Thus, PPy/TiO2/Si with hierarchical structures is the excellent candidate materials for the photoelectric device and the photocatalyst.

Synthesis of SiOH-functionalized composite particles with buckled surface by seeded emulsion polymerization

We demonstrate the synthesis of SiOH-functionalized composite particles with buckled surface via a seeded emulsion polymerization method, their evolution into bicompartmental particles and their application in superhydrophobic coatings. By using polystyrene spheres swelled with non-polymerizable solvent as seeds, emulsion polymerization of 3-(trimethoxysily) propyl methacrylate and styrene leads to the formation of deflated ball- or dried plum-shaped composite particles. The change of solvent amount causes the variation of the morphologies of the obtained particles. With these composite particles as seeds for further emulsion polymerization, bicompartmental particles with unique morphologies are fabricated. On account of the silanol groups generated by hydrolysis of 3-methacryloxy propyl trimethoxysilane (MPS) on their surface, these particles are easily functionalized with organosilane for various applications and also could be applied in the synthesis of more complex organic–inorganic hybrid materials. The modification of the particles with fluorinated silane and their application in the fabrication of superhydrophobic surfaces are demonstrated.

Facile synthesis of PS/RGO@AuNP composite particles as highly active and reusable catalyst for catalytic reduction of p-nitrophenol

Herein, we successfully fabricate a ternary composite particle of polystyrene/reduced graphene oxide@gold nanoparticle (PS/RGO@AuNP) by hydrophobic interaction-driven self-assembly combined with a one-step reduction process, without involving any surface pretreatments of support microspheres in the whole process. The as-prepared PS/RGO@AuNP composite particles have been extensively characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, and inductively coupled plasma-optical emission spectroscopy. The results demonstrate that these ternary raspberry-like composite particles have uniform size and controllable surface morphology. In addition, the PS/RGO@AuNP composite particles have good dispersibility in water and, moreover, exhibit high catalytic activity and excellent reusability during the reduction of p-nitrophenol by sodium borohydride in aqueous solution.

Synthesis of Janus Particle Arrays and Janus Films through an Interfacial Polymerization Method

We report the fabrication of Janus particle arrays and Janus films through the combination of selfassembly of spheres on a water surface and interfacial polymerization of pyrrole or aniline around the spheres. With a low concentration of monomer, it is found that only the water-exposed side of the spheres are coated with a thin layer of polypyrrole (PPy) or polyaniline (PANI), leading to the formation of Janus particle arrays. At an elevated monomer concentration an additional PPy or PANI layer forms on the water surface and further increase in the concentration leads to the coalescence of the layers on water surface and on the waterexposed side of spheres, both of which produce Janus films with PS spheres embedded in a structured conducting polymer.

A polyaniline inverse opal/nanofiber network film fabricated at an air–water interface

Nanostructured polyaniline (PANI) films with well-defined structures have received great research attention due to their various applications in energy storage and conversion, sensors and catalysis. Herein, an air–water interface polymerization method has been developed to fabricate PANI inverse opal/nanofiber network (IO/NFN) films, with the NFN rooted in the bottom of the IO. Colloidal crystals (CCs) are transferred to the surface of an aqueous aniline solution, where aniline could polymerize on the surface of the CC after addition of an oxidant. With a molar ratio of oxidant to aniline of 3 or larger, PANI nanofibers form at the bottom of the PANI coated CC. After removal of the spheres, a PANI IO/NFN film could be obtained. The top layer of IO is composed of a nanobowl array with pores connected to the underlayers, without being covered by overlayers. Such IO/NFN composite structures represent a new family of Janus materials, providing a platform for various potential applications.