Colloidal Crystals Research Articles

Two-dimensional binary colloidal crystals formed by particles with two different sizes

The formation of mathrm {AB_2} type two-dimensional binary colloidal crystals was studied by performing Monte Carlo simulations with two different size particles. The effect of interactions between particles and between particles and a wall, and the particles size ratios on the formation of mathrm {AB_2} structure were examined. mathrm {AB_2} structures formed efficiently when the interaction between equivalently sized particles was smaller than that between differently sized particles. To create mathrm {AB_2} on a wall, it was necessary to choose a suitable particles size ratios, and the attraction between the particles and the wall was greater than that between particles.

Detection of Atrazine and its metabolites by photonic molecularly imprinted polymers in aqueous solutions

Water contamination caused by atrazine (ATZ) application in agriculture is a risk to the environment and human health. Common analytical methods are expensive and complex. A sensor for low-cost and simple detection of ATZ and its metabolites, deethylatrazine (DEA) and deisopropylatrazine (DIA), in aqueous solutions was developed by combining colloidal crystal with molecular imprinting technique. The sensor is formed by 3D interconnected macroporous structure with numerous nanocavities derived from ATZ and its metabolites imprinting in a thin polymeric film. Molecularly Imprinted Polymers (MIPs) were characterized by Fourier Transform Infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) and were incubated in solutions at variable concentrations. Target molecules were specifically absorbed in nanocavities and caused swelling in the polymer resulting in changes of Bragg diffraction peak wavelength. Kinetic tests showed that rebinding equilibrium was reached within 20 minutes. The sensor had a dynamic range of 0.1 to 10 ppb for quantifying target analytes in aqueous solutions with limit of detection of 0.1, 0.2, and 0.3 ppb, and limit of quantification of 0.33, 0.66, and 1 ppb for ATZ, DEA, and DIA, respectively. Cross-reactivity tests were conducted in 1 and 5 ppb solutions combining all three targets and showed absence of positive interference effects and low probability of false positives given by individual sensors. MIPs were examined in natural waters containing ATZ and its metabolites contamination, showing good agreement with real concentrations of targets. The MIP yields rapid and efficient detection of target molecules in aqueous solutions close to environmentally relevant concentrations.

Size-Controllable Synthesis of Monodisperse Magnetite Microparticles Leading to Magnetically Tunable Colloidal Crystals

Colloidal crystals (CCs) are periodic arrays of monodisperse microparticles. Such CCs are very attractive as they can be potentially applicable as versatile photonic devices such as reflective displays, sensors, lasers, and so forth. In this article, we describe a promising methodology for synthesizing monodisperse magnetite microparticles whose diameters are controllable in the range of 100–200 nm only by adjusting the base concentration of the reaction solution. Moreover, monodisperse magnetite microparticles in aqueous suspensions spontaneously form the CC structures under an external magnetic field, leading to the appearance of Bragg reflection colors. The reflection peak can be blue-shifted from 730 nm to 570 nm by the increase in the external magnetic field from 28 mT to 220 mT. Moreover, the reflection properties of CCs in suspension depend on the microparticle concentration in suspension and the diameter of the magnetite microparticles. Both fine-control of microparticle diameter and investigation of magneto-optical properties of CCs would contribute to the technological developments in full-color reflective displays and sensors by utilizing these monodisperse magnetite microparticles.

Catalytic C–C bond formation over platinum nanoparticle catalyst on three-dimensional porous carbon

Three-dimensional porous carbon was prepared via a hard templating method using a colloidal crystal of monodispersed silica nanospheres (SNSs). Platinum nanoparticle catalyst on thus prepared porous carbon was prepared by a liquid-phase method using hydrogen hexachloroplatinate (IV) hexahydrate as Pt source in the presence of ethylene glycol. The prepared Pt catalyst on the carbon was characterized in detail and applied for the C-methylation reaction to elucidate the influence of the pore structure and morphology of the replicated porous carbon supports.

Highly efficient adsorption of radioiodine by a three-dimensional ordered macroporous bismuth-silica composite aerogel

At present, the iodine adsorbents used in the post-treatment iodine removal system are silver-loaded zeolites (AgZ and AgX), because silver and iodine have higher reactivity. The main advantages of bismuth over silver in iodine capture include high-cost performance, non-toxicity and high adsorption capacity. In this work, the sol–gel method combined with the colloidal crystal template method was used to introduce the three-dimensional ordered macroporous structure into the bismuth-silica aerogels. The detected adsorption capacity reaches 696 ± 21 mg/g, which is approximately 3-fold higher than that of silver-loaded zeolites. And the adsorption mechanism of iodine by the bismuth-silica aerogels was revealed. It is found that the bismuth-silica aerogels have chemical adsorption and physical adsorption for iodine, and BiI3 is mainly formed by the chemical reaction between Bi and I2.

(Digital Presentation) Synthesis of Multisize Layered Silica Inverse Opal Photonic Crystals

Today, human beings have found an increasing need for energy. The ever-increasing effort to shrink information systems at higher speeds has led to the common idea that photons are used as carriers of information instead of electrons. Photonic crystals have a structure whose dielectric constants and refractive indices change alternately in one, two, or three dimensions, which are called one-dimensional, two-dimensional, and three-dimensional photon crystals. Periodicity in the refractive index of the crystal structure causes a photonic bandgap that includes a range of frequencies in which light with a frequency of this range is not allowed to pass the crystal structure and is reflected or absorbed.In this work, Poly(methyl methacrylate) (PMMA) microspheres of different sizes were first synthesized using the suspension polymerization method. Concentrations of used materials including initializer, monomer, reaction temperature, reaction time, and rotation speed play important roles in determining the final diameter of PMMA microspheres. Then, the vertical deposition method is used for the growth of multi-layered opals of different sizes, one on top of another. On the other hand, inverse opals have porous and organized structures that are made using opals as the template. The method used in this study to make multisize layered inverse opal made of silica is as follows: 1- Fabrication of a uniform layer of polymer microspheres on a glass substrate with a specified size as a colloidal crystal template 2- Infiltration of void space between the microspheres of the opal template 3- Creating the next layer with different size on the first layer 4- Reinjection of the silica precursor. 5- Repeating the coating layer and injection of the precursor. 6- Finally, selective removal of the opal template by calcination or etching with an organic solvent to create the porous structure of the multisize layered Silica inverse opal photonic crystals. The silica precursor contains a mixture of ethanol, TEOS tetraethyl orthosilicate, and hydrochloric acid.The results show that the fabricated inverse opals are organized, crack-free, and uniform. It is possible to make the desired number of layers by changing the concentration of the PMMA microspheres' colloidal suspension. By changing the characteristics of photonic crystals, such as their constituent materials and refractive indices, lattice constants, and the number of layers, it is possible to control their photonic properties which are beneficial for different applications.

Lattice Induced Short-Range Attraction between Like-Charged Colloidal Particles.

We perform experiments and computer simulations to study the effective interactions between like-charged colloidal tracers moving in a two-dimensional fluctuating background of colloidal crystal. By a counting method that properly accounts for the configurational degeneracy of tracer pairs, we extract the relative probability of finding a tracer pair in neighboring triangular cells formed by background particles. We find that this probability at the nearest neighbor cell is remarkably greater than those at cells with larger separations, implying an effective attraction between the tracers. This effective attraction weakens sharply as the background lattice constant increases. Furthermore, we clarify that the lattice-mediated effective attraction originates from the minimization of free energy increase from deformation of the crystalline background due to the presence of diffusing tracers.

Tuning the Electronic Properties of Mesocrystals

Colloidal crystals are arguably one of the most promising candidates when it comes to the fabrication of nanostructured metamaterials. Especially mesocrystals show exciting new properties that emerge from their inherent directional oriented assembly. With this work, the electrical conductivity of well‐defined micrometer‐sized platinum nanocube‐based mesocrystals is demonstrated and tuned through the variation of different capping agents. Herein, a method is presented to reproducibly quantify the intrinsic resistance of individual mesocrystals through electrical nanoprobing and focused ion beam deposition contacting. A thermally activated tunneling mechanism is identified as the main effect for electron propagation. In addition, the mesocrystals are altered through organically linking and mineral bridging the individual nanoparticles. This results in an increase in mesocrystal rigidity and, more importantly, conductivity by seven orders of magnitude while retaining shape, structure, and composition. In addition, these observations are transferred onto multicomponent superstructures in the form of binary mesocrystals. There, it is demonstrated that the electrical properties could be tuned through the ratio of nanoparticles incorporated into a mesocrystalline host system while simultaneously maintaining potential catalytic or superparamagnetic features of the guest particles.

Factors Influencing Recognition Capability of Inverse Opal Structured Photonic Crystal Sensors

Nowadays, many kinds of colloidal photonic crystal (PC) sensors with inverse opal (IO) structures have been developed. However, there are few systematic studies on the factors influencing their recognition capability and responsiveness capability. In this paper, the relationships between recognition capability of IO structured PC sensors and all the parameters in Bragg–Snell’s law have been explored. In addition, research on the recognition ability of PC sensors typically focuses only on the refractive index difference between the identified substances. Herein, we define two concepts, namely the absolute refractive index difference and the relative refractive index difference, and prove that the recognition ability not only relies on the absolute refractive index between the identified substances, but also on the relative refractive index. Bragg–Snell’s law analysis confirms that the responsiveness capability is directly proportional to the void size of the IO structure, which is also confirmed by the finite difference time domain (FDTD) method. It is believed that these systematic studies have important guiding significance for creating advanced IO structured PC sensors.

Biomineral-Inspired Colloidal Liquid Crystals: From Assembly of Hybrids Comprising Inorganic Nanocrystals and Organic Polymer Components to Their Functionalization.

ConspectusBioinspired organic/inorganic synthetic composites have been studied as high-performance and functional materials. In nature, biominerals such as pearls, teeth, and bones are self-organized organic/inorganic composites. The inorganic components are composed of calcium carbonate (CaCO3) and hydroxyapatite (HAp), while the organic components consist of peptides and polysaccharides. These composites are used as structural materials in hard biological tissues. Biominerals do not show significantly higher performances than synthetic composites such as glass-fiber- or carbon-fiber-reinforced plastics. However, biominerals consist of environmentally friendly and biocompatible components that are prepared under mild conditions. Moreover, they form elaborate nanostructures and self-organized hierarchical structures. Much can be learned about material design from these biomineral-based hierarchical and nanostructured composites to assist in the preparation of functional materials.Inspired by these biological hard tissues, we developed nanostructured thin films and bulk hybrid crystals through the self-organization of organic polymers and inorganic crystals of CaCO3 or HAp. In biomineralization, the combination of insoluble components and soluble acidic macromolecules controls the crystallization process. We have shown that poly(acrylic acid) (PAA) or acidic peptides called polymer additives induce the formation of thin film crystals of CaCO3 or HAp by cooperation with insoluble organic templates such as chitin and synthetic polymers bearing the OH group. Moreover, we recently developed CaCO3- and HAp-based nanostructured particles with rod and disk shapes. These were obtained in aqueous media using a macromolecular acidic additive, PAA, without using insoluble polymer templates. At appropriate concentrations, the anisotropic particles self-assembled and formed colloidal liquid-crystalline (LC) phases.LC materials are generally composed of organic molecules. They show ordered and mobile states. The addition of stimuli-responsive properties to organic rod-like LC molecules led to the successful development of informational displays, which are now widely used. On the other hand, colloidal liquid crystals are colloidal self-assembled dispersions of anisotropic organic and inorganic nano- and micro-objects. For example, polysaccharide whiskers, clay nanosheets, gibbsite plate-shaped particles, and silica rod-shaped particles exhibit colloidal LC states.In this Account, we focused on the material design and hierarchical aspects of biomineral-based colloidal LC polymer/inorganic composites. We describe the design and preparation, nanostructures, and self-assembled behavior of these new bioinspired and biocompatible self-organized materials. The characterization results for these self-assembled nanostructured colloidal liquid crystals found using high-resolution transmission electron microscopy, small-angle X-ray scattering, and neutron scattering and rheological measurements are also reported. The functions of these biomineral-inspired liquid crystals are presented. Because these biomineral-based LC colloidal liquid crystals can be prepared under mild and aqueous conditions and they consist of environmentally friendly and biocompatible components, new functions are expected for these materials.

Poly(hydroxyethyl methacrylate) inverse colloidal crystal membrane for efficient adsorption of lysozyme

In this paper, we provide the adsorption behavior of lysozyme on the inverse colloidal crystal (ICC) membrane under different parameters (such as temperature, pH value, adsorption time). Besides, this also studied lysozyme adsorption behavior by changing the Hydroxyethyl methacrylate (HEMA) ratio of the ICC membrane. Furthermore, we found that ICC membranes containing Hydroxyethyl methacrylate have significantly improved lysozyme adsorption than ICC membranes without Hydroxyethyl methacrylate. With the increasing lysozyme concentration, the ICC membrane containing 50% HEMA showed an excellent selective adsorption effect. At the same time, we describe the adsorption mechanism of lysozyme on the ICC membrane containing HEMA. Finally, after ten adsorption-desorption cycles on the ICC membrane, the membranes adsorption effect on lysozyme has not significantly decreased.

Colloidal photonic crystals formation studied by real-time light diffraction

Abstract Colloidal suspensions crystallize by a natural sedimentation process under certain conditions, the initial volume fraction being one of the parameters that govern this process. Here, we have developed a simple in-situ, real-time, optical characterization technique to study silica colloidal suspensions during natural sedimentation in order to shed new light on this crystallization process. This technique monitors small variations in the wavelength of the reflectance features, allowing the analysis of the formation of the first layers of the crystal with sub-nanometer precision, and their dynamics, which is crucial to ensure a high quality in the final sample. The experimental results indicate that, in certain range of volume fraction, spontaneous crystallization of a colloidal fluid occurs at the bottom of the suspension, as a phase change, then through evaporation of the water it compacts to near close-packed and, eventually, dries. Understanding self-assembly at these scales is paramount in materials science and our results will contribute to improve and characterize the quality and crystallinity of the materials used in this process.

Grain boundary dynamics driven by magnetically induced circulation at the void interface of 2D colloidal crystals.

The complexity of shear-induced grain boundary dynamics has been historically difficult to view at the atomic scale. Meanwhile, two-dimensional (2D) colloidal crystals have gained prominence as model systems to easily explore grain boundary dynamics at single-particle resolution but have fallen short at exploring these dynamics under shear. Here, we demonstrate how an inherent interfacial shear in 2D colloidal crystals drives microstructural evolution. By assembling paramagnetic particles into polycrystalline sheets using a rotating magnetic field, we generate a particle circulation at the interface of particle-free voids. This circulation shears the crystalline bulk, operating as both a source and sink for grain boundaries. Furthermore, we show that the Read-Shockley theory for hard-condensed matter predicts the misorientation angle and energy of shear-induced low-angle grain boundaries based on their regular defect spacing. Model systems containing shear provide an ideal platform to elucidate shear-induced grain boundary dynamics for use in engineering improved/advanced materials.

Double-Base Plate Cooperative Assembly Strategy for the Construction of Ordered Macro-/Mesoporous Noble-Metal Materials for Enhanced Electrochemical Oxidation of Formic Acid

Herein, we propose a general and mild double-base plate cooperative assembly strategy to synthesize the three-dimensional ordered macro-/mesoporous (3DOM/m) noble-metal materials (including Pd, Pt, and Ru), in which the unique double-base plate can play the role of restricting growth area and effectively stabilizing the porous structure of the noble-metal material. In this synthesis process, poly(styrene-b-acrylic acid) (PS-b-PAA) micelles and polymer colloidal crystals are used as templates for the construction of mesopores and macropores, respectively. By adjusting the particle size of polymer colloidal nanospheres, the size of three-dimensional ordered macropores can be precisely adjusted from 160 to 320 nm. Benefiting from the synergistic effect of hierarchical pore structures, the as-prepared 3DOM/m Pd film exhibits outstanding electrocatalytic performance for formic acid oxidation. These results provide an effective and universal method for the designed synthesis of the three-dimensional hierarchical architecture of high-catalytic-activity noble-metal materials.

Photonic Crystals: A Review as Promising Tool for the Selective Detection of Toxic Gases

Photonic crystals (PhCs) based sensing nanotechnology has gained a lot of attention because of its unique structural and morphological characteristics. With the potential utility, these PhC materials are promising as sensitive, selective, economical, portable, and visually detectable gas/vapor sensors for environment quality monitoring. This review focuses on current progress in the natural and artificial PhCs for gas sensing. We will discuss different PhCs including morpho butterfly wings and their nanostructure mimics, porous silicon, Bragg stacks, and colloidal crystals. Moreover, their fabrication techniques for PhCs sensing materials, structural modifications, and sensing mechanisms will be analyzed. In this review article, we highlighted the problem and solution as emerging trends for recent advances in PhCs-based sensors and their applications in environmental monitoring and pollution control. Furthermore, this study envisions new methodologies for PhCs-based sensors that will be highly advanced and effective.

Single-Step Fabrication of Longtail Glasswing Butterfly-Inspired Omnidirectional Antireflective Structures.

Most bio-inspired antireflective nanostructures are extremely vulnerable and suffer from complicated lithography-based fabrication procedures. To address the issues, we report a scalable and simple non-lithography-based approach to engineer robust antireflective structures, inspired by the longtail glasswing butterfly, in a single step. The resulting two-dimensional randomly arranged 80/130/180 nm silica colloids, partially embedded in a polymeric matrix, generate a gradual refractive index transition at the air/substrate interface to suppress light reflection. Importantly, the randomly arranged subwavelength silica colloids display even better antireflection performance for large incident angles than that of two-dimensional non-close-packed silica colloidal crystals. The biomimetic coating is of considerable technological importance in numerous practical applications.

Shaping in the Third Direction; Fabrication of Hemispherical Micro-Concavity Array by Using Large Size Polystyrene Spheres as Template for Direct Self-Assembly of Small Size Silica Spheres.

Silica and polystyrene spheres with a small size ratio (r = 0.005) form by sequential hanging drop self-assembly, a binary colloidal crystal through which calcination transforms in a silica-ordered concavity array. These arrays are capable of light Bragg diffraction and shape dependent optical phenomena, and they can be transformed into inverse-opal structures. Hierarchical 2D and 3D super-structures with ordered concavities as structural units were fabricated in this study.

Imbibition-induced ultrafast assembly and printing of colloidal photonic crystals

HypothesisSelf-assembly of colloidal particles enables the versatile fabrication of highly ordered structures and materials for optical, sensing, and other applications. Nevertheless, many traditional assembly processes are inefficient, because there exists an inevitable contradiction between time efficiency and crystalline quality. In this work, we introduce an ultrafast, robust, and scalable approach of imbibition-induced assembly. We assume that the instantaneous solvent imbibition induced by the nanoporous media could direct ultrafast self-assembly of colloidal particles into ordered structures. ExperimentsSelf-assembly of colloidal particles from a droplet on a nanoporous substrate was firstly observed and investigated. A phase diagram of the thickness of the colloidal crystal as a function of the printing speed and the particle volume fraction was presented through systematic experiments. FindingsThe nanoporous substrate can induce strong capillary flow that will directthe rapid self-assemblyof particles intocolloidalcrystals. The imbibition-induced assembly was spatially and temporally combined with the meniscus-guided printing approach, and the printing speed can be improved by two orders of magnitude than the traditional evaporative assembly methods. We finally demonstrate an effective and ultrafast approach for assembling colloidal particles into photonic crystals with controllable sizes and shapes on the macroscale.

Copper Ion Imprinted Hydrogel Photonic Crystal Sensor Film

An ion-imprinted photonic crystal (IIPC) sensor for visual detection of copper ions was prepared by the combination of ion-imprinting polymer and colloidal photonic crystal (CPC) structure. Monodisperse polystyrene (PS) colloidal nanospheres synthesized by the boiling soap-free emulsion polymerization method were used to prepare the CPC template by the solvent evaporation method. An ion-imprinted polymer based on poly(vinyl alcohol) and chitosan (PVA/CS) is infiltrated therein. The IIPC sensor film was then prepared by solvent-assisted freeze–thaw method while the CPC template was strengthened as the air pores of the template were replaced by PVA/CS hydrogel. The shift of the diffraction wavelength can be directly observed by the naked eye through the color change of the IIPCS according to the concentration change of copper ion. Such sensor film showed good selectivity and sensitivity with a lower detection limit of 10–4 M.

Angular X-ray cross-correlation analysis applied to the scattering data in 3D reciprocal space from a single crystal.

An application of angular X-ray cross-correlation analysis (AXCCA) to the scattered intensity distribution measured in 3D reciprocal space from a single-crystalline sample is proposed in this work. Contrary to the conventional application of AXCCA, when averaging over many 2D diffraction patterns collected from different randomly oriented samples is required, the proposed approach provides an insight into the structure of a single specimen. This is particularly useful in studies of defect-rich samples that are unlikely to have the same structure. The application of the method is shown on an example of a qualitative structure determination of a colloidal crystal from simulated as well as experimentally measured 3D scattered intensity distributions.