Fabrication of Large-area 3-D Ordered Silvercoated Colloidal Crystals and Macroporous Silver Films Using Polystyrene Templates

The highly ordered silver-coated colloidal crystals arrays and macroporous silver films were derived through an electrostatics-induced adsorption effect using polystyrene(PS) as templates. Carboxyl-modified PS microspheres were prepared by emulsifier-free emulsion polymerization using methacrylic acid(MAA) as the functional monomer. PS microspheres were self-assembled into close packing colloidal crystals of facecentered cubic arrays to the substrate with vertical deposition method. These colloidal crystals were modified using dopamine(DA) to form poly-dopamine(PDA) during its oxidative polymerization. Through electrostatic interaction, the silver nanoparticles were deposited and adsorbed onto the surfaces of colloidal crystals templates by exposing [Ag(NH_3)_2]^+solution to infrared irradiation. Removal of the polymeric template by etching with methylbenzene solvent resulted in 3D ordered macroporous silver films. The structural and properties of the ordered silver-coated arrays and macroporous silver films were characterized by field emission scanning electron microscopy(FE-SEM), X-ray diffraction(XRD), UV-vis spectroscopy and surface-enhanced Raman spectroscopy(SERS). The results indicate that the prepared silver-coated arrays and macroporous silver films possess the features of ordered multilayer arrangement, uniformity and repeatability as well as an ideal SERS effect.

Facile Fabrication of Large Area Polystyrene Colloidal Crystal Monolayer via Surfactant-free Langmuir-Blodgett Technique

A facile and novel method for the production of a large area of well-ordered polystyrene （PS） colloidal crystal monolayer was established using the surfactant-free Langmuir-Blodgett （LB） technique. The hydrophobic property （film-forming ability） of PS spheres was improved by a thermo-rheology treatment before LB assembly, and a large film was obtained. In contrast to the traditional LB technique, no surfactant was needed in this method, which could eliminate the additional contamination of surfactants in the preparation process and provided the products with versa- tile applications in nanosphere lithography （NSL） for biosensor, surface plasmon resonance, and surface enhanced Raman spectroscopy .

INVERSE OPALINE STRUCTURE TITANIA PHOTONIC CRYSTALS BY FUNCTIONALLY MODIFIED COLLOIDAL CRYSTALS TEMPLATING

Ordered macroporous titania photonic crystals （PCs） and photonic balls were fabricated by functional modified polymer colloidal crystals. The TiO2 PCs and balls formed through this method exhibit no cracks and lacunae in large areas on their surface and their inner structures.

Improving self-assembly quality of colloidal crystal guided by statistical design of experiments

A versatile and reliable approach is created to fabricate wafer-scale colloidal crystal that consists of a monolayer of hexagonally close-packed polystyrene （PS） spheres. Making wafer-scale colloidal crystal is usually challenging, and it lacks a general theoretical guidance for experimental approaches. To obtain the optimal conditions for self-assembly, a systematic statistical design and analysis method is utilized here, which applies the pick-the-winner rule. This new method combines spin-coating and thermal treatment, and introduces a mixture of glycol and ethanol as a dispersion system to assist self-assembly. By controlling the parameters of self-assembly, we improve the quality of colloidal crystal and reduce the effect of noise on the experiment. To our best knowledge, we are first to pave this path to harvest colloidal crystals. Importantly, a theoretical analysis using an energy landscape base on our process is also developed to provide insights into the PS spheres＇ self-assembly.

Preparation and properties of polymeric colloidal crystals containing rare earth complexes

Rare earth organic complexes were introduced into the polymerization system, and the polymeric colloidal nanospheres containing rare earth complexes were prepared by emulsion copolymerization. The characterization results indicated that the polymeric spheres were small at nanometer size and the diameter was monodisperse, particularly the nanospheres possessed good fluorescent properties. Moreover, the polymeric nanospheres were self-assembled to fabricate the colloidal crystals, which were three-dimensional regular multilayer films. The polymeric colloidal crystal films exhibited excellent luminescent and novel optical properties.

DEFORMATION OF SOFT COLLOIDAL CRYSTALLINE STRUCTURE-THEORETICAL CONSIDERATIONS AND EXPERIMENTAL EVIDENCES BY SYNCHROTRON SMALL-ANGLE X-RAY SCATTERING ON TENSILE STRETCHED POLYMERIC LATEX FILM

Films obtained via drying a polymeric latex dispersion are normally colloidal crystalline where latex particles are packed into a face centered cubic (fcc) structure.Different from conventional atomic crystallites or hard sphere colloidal crystallites,the crystalline structure of these films is normally deformable due to the low glass transition temperature of the latex particles.Upon tensile deformation,depending on the drawing direction with respect to the normal of specific crystallographic plane,one obs...

Applied electric field to fabricate colloidal crystals with the photonic band-gap in communication waveband

The macropore silica colloidal crystal templates were assembled orderly in a capillary glass tube by an applied electric field method to control silica deposition. In order to achieve the photonic band gap （PBG） of colloidal crystal in optical communication waveband, the diameter of silica microspheres is selected by Bragg diffraction formula. An experiment was designed to test the bandgap of the silica crystal templates. This paper discusses the formation process and the close-packed fashion of the silica colloidal crystal templates was discussed. The surface morphology of the templates was also analyzed. The results showed that the close-packed fashion of silica array templates was face-centered cubic （FCC） structure： The agreement is very good between the experimental data and the theoretical calculation.

A colloidal crystal double-heterostructure fabricated with the angle controlled inclined deposition method

A self-assembly method, named the angle controlled inclined deposition method, is developed for fabricating well- ordered silica and polystyrene colloidal crystals. A high-quality colloidal crystal with a flat and uniform surface over a large area can be produced rapidly using a minute quantity of suspension and without any additional equipment. By controlling the inclined angle, we can fabricate colloidal crystals with diverse numbers of layers. A colloidal crystal double-heterostructure （composed of three different colloidal photonic crystals） can be rapidly fabricated with this method. Both experimental and simulation results show that the photonic band gap of the double-heterostructure is not a simple superposition of that of the compositional colloidal crystals along the stacking direction.

Preparation of polystyrene spheres in different particle sizes and assembly of the PS colloidal crystals

Monodisperse polystyrene (PS) colloidal spheres were successfully prepared through emulsifier-free emulsion polymerization by controlling the polymerization reaction time, ionic strength of the system, concentration of the ionic copolymer (sodium p-styrenesulfonate) and other factors. The PS colloidal spheres were assembled into colloidal crystals whose structures were mainly face-centered cubic (fcc) close-packed. Then FDTD method was used to calculate the color-rendering characteristics of the colloidal crystals surface. The calculated results were consistent with the experimental results.

Recent research progress in wettability of colloidal crystals

The wettability of solid surfaces has attracted extensive interest in both theoretical research and industrial applications. This paper reviews recent research progress in the fabrication and applications of the colloidal crystals with special wettability. Based on the modified equation of Wenzel and Cassie, the colloidal crystals with special wettability have been obtained by either application of the intrinsic rough structure or modification of the surface chemical composition. Some typical applications of colloidal crystals with special wettability have also been demonstrated.

Self-assembly of latex particles for colloidal crystals

Self-assembly of latex particles is of great importance for fabricating various functional colloidal crystals. In this paper, we review recent research on the self-assembly of latex particles for colloidal crystals, covering the assembly forces and various assembly approaches of latex particles, including self-assembly by gravity sedimentation, vertical deposition, physical confinement, electric field, and magnetic field. Furthermore, some simple methods for assembling latex particles such as spin coating, spray coating, and printing are also summarized.

Magnetic Properties of Co 2D Antidot Arrays with Hexagonal Holes Using Colloidal Crystal Template Method

In this work, Co 2D antidot arrays with well-ordered hexagonal holes ranging in size from 1.3 to 6.2 μm were fabricated by colloidal crystal template method. The geometry configuration and magnetic properties of the samples were investigated. An enormous increase in coercivity and squareness, as compared with the corresponding continuous film, was observed. Magnetic properties of Co 2D antidot arrays showed a close dependence on pore diameter. According to geometric calculation, the effect of the pore diameter on magnetic properties was also discussed. The Co 2D antidot arrays obtained by this method are promising candidates for high-density information storage.

Small angle X-ray scattering of the colloidal crystal

The monodisperse polystyrene spheres are assembled into the colloidal crystal on the glass substrate by vertical deposition method, which is aimed at the so-called photonic crystal applications. The structural information of the bulk colloidal crystal is crucial for understanding the crystal growth mechanism and devel- oping the various applications of colloidal crystal. Small-angle X-ray scattering （SAXS） technique was used to obtain the bulk structure of the colloidal crystal at Beamline lW2A of BSRF. It is found that the SAXS pattern is sensitive to the relative orientation between the colloidal sample and the incident X-ray direction. The crystal lattice was well distinguished and determined by the SAXS data.

The infrared transmission through gold films on ordered two-dimensional non-close-packed colloidal crystals

We studied the infrared transmission properties of gold films on ordered two-dimensional nonclose- packed polystyrene （PS） colloidal crystal. The gold films consist of gold half-shells on the PS spheres and gold film with 2D arrays of holes on the glass substrate. An extraordinary optical transmission phenomenon could be found in such a structure. Simulations with the finite-difference time-domain method were also employed to get the transmission spectra and electric field distribution. The transmission response of the samples can be adjusted by controlling the thickness of the gold films. Angle-resolved measurements were performed using polarized light to obtain more information about the surface plasmon polariton resonances of the gold films. As the angle changes, the transmission spectra change a lot. The transmission spectra of p-polarized light have quite different properties compared to those of s-polarized light.

Influence of Sedimentation on Crystallization of Charged Colloidal Particles

密度在固体和液体阶段之间匹配的方法经常被采用有效地在一个胶体的系统的动态行为上消除暂停的沉积的效果。有在匹配密度、无敌的媒介(在合适的比例的 H2O 和 D2O 的混合物) 驱散的 98 nm 的直径的控告的胶体的 microspheres 的结晶化的实验与相比检验沉积的影响。胶体的暂停的思考系列被用来监视结晶化进程。结果证明水晶缩放密度无敌(也就是，面对沉积) 样品变得比的快匹配密度(当沉积不在时) 在结晶化的起始的阶段的大小写，然后后者追上并且超过前者。解释这些观察，我们假设在安定晶体，沉积在进入水晶结构的更多的粒子便于结果。当晶体增加到改变尺寸，安定速度不管多么变得大并且水动力学磨擦从精细的水晶结构剥去一些粒子。总的来说，沉积看起来开始加速水晶尺寸生长然后延迟生长。另外，在 microgravity 下面形成的水晶结构更仔细在正常严肃比那被包装。

Hexagonal trumpet-like flowers growth induced by a colloidal crystal composite film

Hexagonal trumpet-like sodium hexafluorosilicate （SFS） flowers, grown on an ordered porous polystyrene film （OPPF）, were prepared via a synchronous dissolution/regrowth process. Their formation process can be divided into several steps： first, the dissolution of the silica spheres induced the crystallization of SFS onto the OPPF; second, some pores emerged on the closely packed bumps when being blown by the SiF4 gas; third, when the crystal was blown by continuous gas from the pores, the span of the top became larger than that of the bottom.

Modification of the spontaneous emission of quantum dots near the surface of a three-dimensional colloidal photonic crystal

This paper demonstrates experimentally and numerically that a significant modification of spontaneous emission rate can be achieved near the surface of a three-dimensional photonic crystal. In experiments, semiconductor coreshell quantum dots are intentionally confined in a thin polymer film on which a three-dimensional colloidal photonic crystal is fabricated. The spontaneous emission rate of quantum dots is characterised by conventional and time-resolved photoluminescence （PL） measurements. The modification of the spontaneous emission rate, which is reflected in the change of spectral shape and PL lifetime, is clearly observed. While an obvious increase in the PL lifetime is found at most wavelengths in the band gap, a significant reduction in the PL lifetime by one order of magnitude is observed at the short-wavelength band edge. Numerical simulation reveals a periodic modulation of spontaneous emission rate with decreasing modulation strength when an emitter is moved away from the surface of the photonic crystal. It is supported by the fact that the modification of spontaneous emission rate is not pronounced for quantum dots distributed in a thick polymer film where both enhancement and suppression are present simultaneously. This finding provides a simple and effective way for improving the performance of light emitting devices.

Influence of colloidal particle transfer on the quality of self-assembling colloidal photonic crystal under confined condition

The relationship between colloidal particle transfer and the quality of colloidal photonic crystal（CPC） is investigated by comparing colloidal particle self-assembling under the vertical channel（VC） and horizontal channel（HC） conditions.Both the theoretical analyses and the experimental measurements indicate that crystal quality depends on the stability of mass transfer.For the VC,colloidal particle transfer takes place in a stable laminar flow,which is conducive to forming high-quality crystal.In contrast,it happens in an unstable turbulent flow for the HC.Crystals with cracks and an uneven surface formed under the HC condition can be seen from the images of a field emission scanning electron microscope（SEM） and a three-dimensional（3D） laser scanning microscope（LSM）,respectively.

Real-time quantitative optical method to study temperature dependence of crack propagation process in colloidal photonic crystal film

A real-time quantitative optical method to characterize crack propagation in colloidal photonic crystal film（CPCF）is developed based on particle deformation models and previous real-time crack observations. The crack propagation process and temperature dependence of the crack propagation rate in CPCF are investigated. By this method, the crack propagation rate is found to slow down gradually to zero when cracks become more numerous and dense. Meanwhile, with the temperature increasing, the crack propagation rate constant decreases. The negative temperature dependence of the crack propagation rate is due to the increase of van der Waals attraction, which finally results in the decrease of resultant force. The findings provide new insight into the crack propagation process in CPCF.

Preparation and Characterization of Three-dimensionally Ordered Crystalline Macroporous CeO_2

A stable 3DOM CeO2 with well-defined inverse opal microstructure and crystalline walls structure has been successfully synthesized by application of three-dimensional order PMMA beads as templates. Structural feature of products was characterized by using SEM, DTA-TG XRD.