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[Display omitted] The formation of soft colloidal crystals, which are nonclose-packed ordered arrays of colloidal particles suspended in a solvent, is dictated by a single physical factor that yields a fixed threshold at order–disorder boundaries for different experimental conditions such as ion concentration, solvent type, and particle size. Identifying the determinant factor and its threshold value should enable the prediction of the critical concentrations of colloidal particles to form soft colloidal crystals. Soft colloidal crystals were fabricated using a series of monohydric alcohols as dispersion media and reflectance spectra were measured to locate order–disorder boundaries. The interaction forces acting between particles were also measured by employing atomic force microscopy. The interparticle forces at the order–disorder boundaries exhibited a universal threshold that was independent of the solvent types including alcohols and water. Therefore, the determinant factor for the formation of soft colloidal crystals was determined to be the force acting between the particles. Furthermore, a priori calculation of this critical force and consequently the critical particle concentration in colloidal systems was demonstrated by referring to the pressure at the liquid-to-solid transition in a hard sphere system (Alder transition). [ABSTRACT FROM AUTHOR]

Polyvinyl alcohol (PVA)/TiO2/colloidal photonic crystal (CPC) films with photocatalytic properties are presented, where TiO2 nanoparticles were introduced into the PVA gel network. Such PVA/TiO2/CPC films possess three-dimensional periodic structures that are supported with a PVA/TiO2 composite gel. The unique structural color of CPCs can indicate the process of material preparation, adsorption, and desorption. The shift of diffraction peaks of CPCs can be more accurately determined using fiber-optic spectroscopy. The effect of the PVA/TiO2/CPC catalyst films showed better properties as the degradation of methylene blue (MB) by the PVA/TiO2/CPC film catalyst in 4 h was 77~90%, while the degradation of MB by the PVA/TiO2 film was 33% in 4 h, indicating that the photonic crystal structure was 2.3~2.7 times more effective than that of the bulk structure. [ABSTRACT FROM AUTHOR]

Opal, a renowned gemstone, exhibits an optical phenomenon known as "play of color," which is classified as a kind of structural color. This unique property makes opal a highly valuable material from the natural science, industry, and humanity perspectives. Opal has a complex internal structure called colloidal polycrystalline, and thus, representations of opal remain unestablished in computer graphics. In this study, to approximate the complex internal structure of opal, we imitate its formation process using the three-dimensional additively weighted Voronoi tessellation and percolation model. Further, we apply path tracing to compute the diffraction patterns of visible light inside opal by utilizing the Ewald construction employed in X-ray diffraction theory. Finally, we achieve a visually plausible output through spectral rendering. [ABSTRACT FROM AUTHOR]

The development of self‐replicating systems is of great importance in research on the origin of life. As the most iconic molecules, nucleic acids have provided prominent examples of the fabrication of self‐replicating artificial nanostructures. However, it is still challenging to construct sophisticated synthetic systems that can create large‐scale or three‐dimensionally ordered nanomaterials using self‐replicating nanostructures. By integrating a template system containing DNA‐functionalized colloidal seeds with a simplified DNA strand‐displacement circuit programmed subsystem to produce DNA‐functionalized colloidal copies, we developed a facile enthalpy‐mediated strategy to control the replication and catalytic assembly of DNA‐functionalized colloids in a time‐dependent manner. The replication efficiency and crystal quality of the resulting superlattice structures can be effectively increased by regulating the molar ratio of the template to the copy colloids. By constructing binary systems from two types of gold nanoparticles (or proteins), superlattice structures with different crystal symmetries can be obtained through the replication and catalytic assembly processes. This programmable enthalpy‐mediated approach was easily leveraged to achieve the phase transformation and catalytic amplification of colloidal crystals starting from different initial template crystals. This work offers a potential way to construct self‐replicating artificial systems that exhibit complicated phase behaviors and can produce large‐scale superlattice nanomaterials. [ABSTRACT FROM AUTHOR]

Fabrication of ceramic materials has been developed through building up block particles. One of the commonest process of building blocks is a sintering process, in which dense sintered bodies are fabricated via building up particles. This work shows a different type of building blocks. Oriented ZnO seed layers composed of hexagonal plate-like ZnO particles were prepared by dip-coating convective self-assembly method through adjusting the particle volume fraction in suspension and the substrate withdrawal rate. Oriented ZnO rod films were fabricated by growing seed layers using a hydrothermal method. Concentration of the precursor, and hydrothermal treatment time was optimized to synthesize homogeneous ZnO rod arrays. The uniformity of the rod arrays was improved by applying a strong magnetic field (12 T) during hydrothermal treatment. [ABSTRACT FROM AUTHOR]

A novel approach is reported that harnesses laser‐induced shockwave spallation technique to selectively remove clusters of polystyrene (PS) microspheres from close‐packed monolayers for the creation of 2D colloidal micropatterns. The strategic design of the layer structure by incorporating a thin layer of poly(vinyl alcohol) (PVA) on top of the PS monolayer enables the complete delamination of PS particle clusters. Its use is demonstrated for creating different sizes of circular microscale spallation patterns by regulating the tensile force of the shockwave with laser fluence adjustments. To further control the diameter of the spallation pattern, various shadow masks are utilized to tune the shockwave generation region. The finding reveals that both PVA thickness and spallation force play key roles in adjusting cluster spallation size with complete removal. The study highlights the potential of laser spallation techniques as a rapid and non‐contact method for 2D colloidal crystal patterning by leveraging spatially regulated shockwave spallation forces. [ABSTRACT FROM AUTHOR]

Colloidal crystals formed with attractive interactions are used for in-situ observations of homogeneous nucleation processes in density-matched dispersion. We found globular and plate-like polycrystalline clusters stably suspended in the dispersion. Both clusters rotated randomly and moved freely with suspending in the dispersion. They were probably formed through homogeneous nucleation processes. [ABSTRACT FROM AUTHOR]

Abstract A novel approach is reported that harnesses laser‐induced shockwave spallation technique to selectively remove clusters of polystyrene (PS) microspheres from close‐packed monolayers for the creation of 2D colloidal micropatterns. The strategic design of the layer structure by incorporating a thin layer of poly(vinyl alcohol) (PVA) on top of the PS monolayer enables the complete delamination of PS particle clusters. Its use is demonstrated for creating different sizes of circular microscale spallation patterns by regulating the tensile force of the shockwave with laser fluence adjustments. To further control the diameter of the spallation pattern, various shadow masks are utilized to tune the shockwave generation region. The finding reveals that both PVA thickness and spallation force play key roles in adjusting cluster spallation size with complete removal. The study highlights the potential of laser spallation techniques as a rapid and non‐contact method for 2D colloidal crystal patterning by leveraging spatially regulated shockwave spallation forces.

Polyvinyl alcohol (PVA)/TiO2/colloidal photonic crystal (CPC) films with photocatalytic properties are presented, where TiO2 nanoparticles were introduced into the PVA gel network. Such PVA/TiO2/CPC films possess three-dimensional periodic structures that are supported with a PVA/TiO2 composite gel. The unique structural color of CPCs can indicate the process of material preparation, adsorption, and desorption. The shift of diffraction peaks of CPCs can be more accurately determined using fiber-optic spectroscopy. The effect of the PVA/TiO2/CPC catalyst films showed better properties as the degradation of methylene blue (MB) by the PVA/TiO2/CPC film catalyst in 4 h was 77~90%, while the degradation of MB by the PVA/TiO2 film was 33% in 4 h, indicating that the photonic crystal structure was 2.3~2.7 times more effective than that of the bulk structure.

Structural colors materials are profoundly explored owing to their fantastic optical properties and widespread applications. Development of structural color materials bearing flexible morphologies and versatile functionalities is highly anticipated. Here, a droplet-confined, magnetic-induced self-assembly strategy for generating rotary structural color spindles (SCSPs) by fast solvent extraction is proposed. The as-prepared SCSPs exhibit an orderly close-packed lattice structure, thus appearing brilliant structural colors that serve as encoding tags for multiplexed bioassays. Besides, benefitting from the abundant specific surface area, biomarkers can be labeled on the SCSPs with high efficiency for specific detection of analytes in clinical samples. Moreover, the directional magnetic moment arrangement enables contactless magnetic manipulation of the SCSPs, and the resultant rotary motions of the SCSPs generates turbulence in the detection solution, thus significantly improving the detection efficiency and shortening the detection time. Based on these merits, a portable point-of-care-testing strip integrating the rotary SCSPs is further constructed and the capability and advantages of this platform for multiplexed detection of tumor-related exosomes in clinical samples are demonstrated. This study offers a new way for the control of bottom-up self-assembly and extends the configuration and application values of colloidal crystal structural colors materials. [ABSTRACT FROM AUTHOR]

Abstract Structural colors materials are profoundly explored owing to their fantastic optical properties and widespread applications. Development of structural color materials bearing flexible morphologies and versatile functionalities is highly anticipated. Here, a droplet‐confined, magnetic‐induced self‐assembly strategy for generating rotary structural color spindles (SCSPs) by fast solvent extraction is proposed. The as‐prepared SCSPs exhibit an orderly close‐packed lattice structure, thus appearing brilliant structural colors that serve as encoding tags for multiplexed bioassays. Besides, benefitting from the abundant specific surface area, biomarkers can be labeled on the SCSPs with high efficiency for specific detection of analytes in clinical samples. Moreover, the directional magnetic moment arrangement enables contactless magnetic manipulation of the SCSPs, and the resultant rotary motions of the SCSPs generates turbulence in the detection solution, thus significantly improving the detection efficiency and shortening the detection time. Based on these merits, a portable point‐of‐care‐testing strip integrating the rotary SCSPs is further constructed and the capability and advantages of this platform for multiplexed detection of tumor‐related exosomes in clinical samples are demonstrated. This study offers a new way for the control of bottom‐up self‐assembly and extends the configuration and application values of colloidal crystal structural colors materials.

Colloidal crystals are interesting as functional structures due to their emergent photonic properties like photonic stop bands and bandgaps that can be used to redirect light. They are commonly formed by a drying process that is assisted by capillary forces at the drying fronts. In this manuscript, we demonstrate the optically induced dynamic thermofluidic assembly of 2D and 3D colloidal crystals. We quantify in experiment and simulation the structure formation and identify thermo-osmosis and temperature induced depletion interactions as the key contributors to the colloidal crystal formation. The non-equilibrium nature of the assembly of colloidal crystals and its dynamic control by laser-induced local heating promise new possibilities for a versatile formation of photonic structures inaccessible by equilibrium processes.

Recent advances in high-performance flexible electronic devices have increased the demand for more diverse and complex nanofabrication methods; high-resolution, high-efficiency, and low-cost patterning strategies for next-generation devices are therefore required. In this study, we demonstrate the formation of dewetting-induced hierarchical patterns using two self-assembled materials: block copolymers (BCPs) and colloidal crystals. The combination of the two self-assembly methods successfully generates multiscale hierarchical patterns because the length scales of the periodic colloidal crystal structures are suitable for templating the BCP patterns. Various concentric ring patterns were observed on the templated BCP films, and a free energy model of the polymer chain was applied to explain the formation of these patterns relative to the template width. Frequently occurring spiral-defective features were also examined and found to be promoted by Y-junction defects. [ABSTRACT FROM AUTHOR]

Carbon materials possessing many merits including chemical stability, large specific surface, high electrical conductivity, low cost and easy to synthesize have considered as promising electrode materials for electrochemical energy storage devices. Especially, three-dimensional (3D) ordered hierarchically porous carbon (3D OHPC) materials templated from colloidal crystals have attracted much attention. These materials have special advantages such as 3D continuous carbon network that can enhance the charge transfer, interconnected ordered macropores that can promote the rapid diffusion of electrolyte/ions, and meso- or micropores that can provide high surface areas and accommodate guest active materials. In the present review, the synthetic strategies and main features for two main structures of 3D OHPC, inverse opal and opal, are reported and concisely described. Recent progresses in the alkali-metal ion batteries based on 3D OHPC, such as Li-ion batteries, Na-ion batteries, K-ion batteries, Li–S(Se) batteries, are discussed. At last, current challenges in the controlled synthesis of 3D OHPC-based electrode and prospects for the applications in alkali-metal ion batteries are proposed. The review could offer a guidance for rational design and synthesis of 3D OHPC materials toward alkali metal-ion batteries with high-performances. [Display omitted] [ABSTRACT FROM AUTHOR]

We show that both the optical stopband wavelength and effective bandwidth of films of gel-immobilized loosely packed colloidal photonic crystals can be controlled over a wide range. When the gelation reagent of the charge-stabilized colloidal crystals was photopolymerized under ultraviolet light using different upper- and bottom-light intensities, it resulted in a gel-immobilized colloidal crystal film with a broadened Bragg reflection peak. Moreover, the width of the Bragg peak increased from 30 to 190 nm as the difference between the light intensities increased. Films with wider Bragg peaks exhibited a brighter reflection color because of the superposition of the shifted Bragg reflections. Furthermore, the Bragg wavelength could be varied over a wide range (500–650 nm) while maintaining the same broadened effective bandwidth by varying the swelling solvent concentration. These findings will expand the applicability of colloidal crystals for use in photonic devices and color pigments. [ABSTRACT FROM AUTHOR]

Vacancy dynamics of high‐density 2D colloidal crystals with a polydispersity in particle size are studied experimentally. Heterogeneity in vacancy dynamics is observed. Inert vacancies that hardly hop to other lattice sites and active vacancies that hop frequently between different lattice sites are found within the same samples. The vacancies show high probabilities of first hopping from one lattice site to another neighboring lattice site, then staying at the new site for some time, and later hopping back to the original site in the next hop. This back‐returning hop probability increases monotonically with the increase in packing fraction, up to 83%. This memory effect makes the active vacancies diffuse sluggishly or even get trapped in local regions. Strain‐induced vacancy motion on a distorted lattice is also observed. New glassy properties in the disordered crystals are discovered, including the dynamical heterogeneity, the presence of cooperative rearranging regions, memory effect, etc. Similarities between the colloidal disordered crystals and the high‐entropy alloys (HEAs) are also discussed. Molecular dynamics simulations further support the experimental observations. These results help to understand the microscopic origin of the sluggish dynamics in materials with ordered structures but in random energy landscapes, such as high‐entropy alloys. [ABSTRACT FROM AUTHOR]

Previous reports have shown that colloidal crystal (CC) films with visible Bragg reflection characteristics can be fabricated by the surface modification of monodisperse silica particles (SiPs) with poly(methyl methacrylate) (PMMA) chains, followed by hot-pressing at 150 °C. However, the reflection bands of the CC films were very broad due to their relative disordering of SiPs. In this report, we attempted to fabricate the CC films using SiPs surface-modified with poly(n-octyl acrylate) (POA) chains by hot-pressing. When the cast films of POA-grafted SiPs were prepared by hot-pressing at 100 °C, the reflection bands were narrow rather than those of CC films of PMMA-grafted SiPs. This can be ascribed to easy disentanglement of POA chains during the hot-pressing process, thereby enabling the formation of well-ordered CC structures. Moreover, the reflection colors of CC films could be easily tuned by controlling the molecular weight of POA chains grafted on the SiP surface. [ABSTRACT FROM AUTHOR]

Abstract Vacancy dynamics of high‐density 2D colloidal crystals with a polydispersity in particle size are studied experimentally. Heterogeneity in vacancy dynamics is observed. Inert vacancies that hardly hop to other lattice sites and active vacancies that hop frequently between different lattice sites are found within the same samples. The vacancies show high probabilities of first hopping from one lattice site to another neighboring lattice site, then staying at the new site for some time, and later hopping back to the original site in the next hop. This back‐returning hop probability increases monotonically with the increase in packing fraction, up to 83%. This memory effect makes the active vacancies diffuse sluggishly or even get trapped in local regions. Strain‐induced vacancy motion on a distorted lattice is also observed. New glassy properties in the disordered crystals are discovered, including the dynamical heterogeneity, the presence of cooperative rearranging regions, memory effect, etc. Similarities between the colloidal disordered crystals and the high‐entropy alloys (HEAs) are also discussed. Molecular dynamics simulations further support the experimental observations. These results help to understand the microscopic origin of the sluggish dynamics in materials with ordered structures but in random energy landscapes, such as high‐entropy alloys.

[Display omitted] Self-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. Self-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. The nanoporous substrate can induce strong capillary flow that will direct the rapid self-assembly of particles into colloidal crystals. 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. [ABSTRACT FROM AUTHOR]

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.

A rapid curing method for the preparation of colloidal photonic crystal films is presented. Firstly, a colloidal crystal array template was prepared by self-assembly of nanospheres, and then a dilute polymer solution was poured into the gap of the template. Then the composite photonic film was obtained as the polymer solution was cured. Such films have good properties in mechanical strength, anti pH interference, rapid solvent response and are easy to preserve. The films show good linear response to ethanol aqueous solutions of different concentrations, and the response equilibrium takes less than 20 s. The films also show long-term stability and reusability, and further functionalization can make the films multi-sensitive.

Rapid, sensitive, selective and portable virus detection is in high demand globally. However, differentiating non-infectious viral particles from intact/infectious viruses is still a rarely satisfied sensing requirement. Using the negative space within monolayers of polystyrene (PS) spheres deposited directly on gold electrodes, we fabricated tuneable nanochannels decorated with target-selective bioreceptors that facilitate the size-selective detection of intact viruses. Detection occurred through selective nanochannel blockage of diffusion of a redox probe, [Fe(CN)6]3/4−, allowing a quantifiable change in the oxidation current before and after analyte binding to the bioreceptor immobilised on the spheres. Our model system involved partial surface passivation of the mono-assembled PS spheres, by silica glancing angle deposition, to confine bioreceptor immobilisation specifically to the channels and improve particle detection sensitivity. Virus detection was first optimised and modelled with biotinylated gold nanoparticles, recognised by streptavidin immobilised on the PS layer, reaching a low limit of detection of 37 particles/mL. Intact, label-free virus detection was demonstrated using MS2 bacteriophage (~23–28 nm), a marker of microbiological contamination, showing an excellent limit of detection of ~1.0 pfu/mL. Tuneable nanochannel geometries constructed directly on sensing electrodes offer label-free, sensitive, and cost-efficient point-of-care biosensing platforms that could be applied for a wide range of viruses. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

At the studying the Mannesmann piercing process, we unify two approaches to the problem solving. Namely, the commercial FEM software procedure and the mathematical model of the process via the mathematical model of the considered FEM-simulation bound by certain unifying symmetries. Such phenomenon seemingly exists only if the FE-mesh is initiated to be physically interpreted. We shortly outline, how to come to the slightly modified Cahn-Hilliard equation as to the mathematical model of the FE-simulation possessing quasi-symmetry given by a lattice of colloidal assembly formed by the chosen FE-mesh. Separation of two cylindrical surfaces of the pierced product together with the inpainting role of the piercing plug are described with respect to the background given by the Navier-Stokes equations related to the flow between the both surfaces. Influence of the involved groups related to the considered quasi-symmetry is illustrated by the convergence/divergence of the Newton-Raphson number in the CPU-time. [ABSTRACT FROM AUTHOR]

Two-dimensionally Ordered macroporous films have attracted attention for their potential application such as sensors and optoelectronic devices. Here, highly ordered ZnO nanonets film were successfully prepared by a facile method, which uses monolayer colloidal crystal template composed of polystyrene spheres and sol-gel spin-coating method. Furthermore, ZnO nanonets-based ultraviolet photodetector are constructed, which showed high on/off current ratio of 2.7 × 105 under 370 nm UV light illumination with an intensity of 0.85 mW/cm2.

• Janus microrobots with magnetic control and stable structure color. • Prickly surface endowed the microrobot with large surface for enriching targets. • Induced self-assembly in combination with hydrothermal synthesis. • Highly sensitive multiplex exosome assays. Microrobots have been widely reported as a powerful tool for biosensing. Attempts in this field tend to improve their functions by using different fabrication technologies. In this paper, a novel prickly Janus magnetic and photonic microrobot is presented for efficient exosome assays by integrating induced self-assembly and hydrothermal synthesis techniques. The induced self-assembly results in Janus magnetic and photonic microrobots with magnetic controllability and striking structure colors, making them ideal for efficient multiplex assays. The hydrothermal synthesis helps the formation of prickly surface, endowing the microrobot with large surface for capturing targets. It was demonstrated that these prickly Janus magnetic and photonic microrobots can carry out multiplex exosome assays with high sensitivity benefiting from their stable structure colors, magnetic autonomous motion, and capacity of enriching. [ABSTRACT FROM AUTHOR]

NaYF 4 :Er/Yb nanorods, colloidal crystal (CC) and Ag nanoparticles were obtained by solvothermal, self-assembly and hydrothermal methods, respectively. The hybrid structure of NaYF 4 :Er/Yb nanorods-colloidal crystal-Ag film (Ag-CC-NaYF 4 :Er/Yb) with low cost and large area was prepared for upconversion luminescence (UCL). The UCL enhancement was achieved by synergistic use of local reflection of incident light by colloidal crystal and reflection of incident light by Ag film. Compare with that of NaYF 4 :Er/Yb nanorods, the UCL intensity of Ag-CC-NaYF 4 :Er/Yb was increased by 33.2-folds. The UCL enhancement mechanism in Ag-CC-NaYF 4 :Er/Yb was investigated systematically. Our work has certain guiding value for promoting the application of upconversion nanocrystals in the fields of anti-counterfeiting, biological imaging, display and so on. • The hybrid of Ag-CC-NaYF 4 :Er/Yb with low cost and large area was prepared for UCL. • Compare with that of NaYF 4 :Er/Yb nanorods, the UCL intensity of Ag-CC-NaYF 4 :Er/Yb was increased by 33.2-folds. • The UCL enhancement mechanism in Ag-CC-NaYF 4 :Er/Yb was investigated systematically. [ABSTRACT FROM AUTHOR]

A label-free molecular imprinted polymer (MIP) sensor was fabricated for the detection of progesterone in aqueous solutions, by polymerization inside the void spaces of colloidal crystals, which gave them photonic properties. The prepolymerization mixture was prepared from acrylic acid as the functional monomer, ethylene glycol as the cross-linker agent, ethanol as solvent, and progesterone as the imprinted template. After polymerization, the colloidal crystal was removed by acid etching and the target eluted with a solvent. Material characterization included as follows: attenuated total reflectance-Fourier-transform infrared spectroscopy, dynamic light scattering, swelling experiments, and environmental scanning electron microscopy. MIPs were investigated by equilibrium binding, kinetics experiments, and UV–visible spectra to investigate Bragg diffraction peak shift that occurs with the rebinding at different progesterone concentrations in deionized water and 150-mM NaCl solutions. The MIP response was investigated with progesterone concentration in the 1–100 μg L−1 range, with LOD of 0.5 μg L−1, reaching the detected range of hormone in natural waters. Furthermore, hydrogel MIP films were successfully tested in various real water matrices with satisfactory results. Moreover, the MIP film exhibited good selectivity toward the progesterone hormone evidenced by a larger response than when exposed to structurally similar molecules. Computational studies suggested that size along with surface potential influenced the binding of analog compounds. Due to their ease of use and low cost, the sensors are promising as screening tools for the presence of progesterone in aqueous samples. [ABSTRACT FROM AUTHOR]

A functional lens coating, based on the structure of inversed colloidal photonic crystals, is proposed. The color-reflecting colloidal crystal was first prepared by self-assembly of nano-colloids and was infiltrated by adhesive polymer solution. As the polymer was crosslinked and the crystal array was removed, a robust mesh-like coating was achieved. Such a functional coating has good transmittance and has a shielding efficiency of ~9% for UV–blue light according to different particle sizes of the nano-colloids, making it an ideal functional material. [ABSTRACT FROM AUTHOR]

Because of the unique features of spherical symmetry, angle-independency, good monodispersity, controllable components and morphologies, structural color particles (SCPs) have found great significances in various fields such as sensing, monitoring, biological assays, etc. Here, inspired by the melanosome-derived bright structural colors and the self-adhesivity of mussels, we present a kind of bioinspired SCPs assembled from polydopamine (PDA)-adhered multi-layer graphene oxide (GO) encapsulated silica nanoparticles (SNs). It is demonstrated that compared with traditional SCPs, the designed particles possess brighter and more vibrant structural colors, and no complicated modification is required during the functionalization process due to the abundant inherent functional groups of GO. The resultant SCPs are verified to be capable for direct hybridization chain reaction and multiplexed nucleic acid assays. These properties indicate the promising prospects of our designed SCPs.

Recent advances in high-performance flexible electronic devices have increased the demand for more diverse and complex nanofabrication methods; high-resolution, high-efficiency, and low-cost patterning strategies for next-generation devices are therefore required. In this study, we demonstrate the formation of dewetting-induced hierarchical patterns using two self-assembled materials: block copolymers (BCPs) and colloidal crystals. The combination of the two self-assembly methods successfully generates multiscale hierarchical patterns because the length scales of the periodic colloidal crystal structures are suitable for templating the BCP patterns. Various concentric ring patterns were observed on the templated BCP films, and a free energy model of the polymer chain was applied to explain the formation of these patterns relative to the template width. Frequently occurring spiral-defective features were also examined and found to be promoted by Y-junction defects.

We show that both the optical stopband wavelength and effective bandwidth of films of gel-immobilized loosely packed colloidal photonic crystals can be controlled over a wide range. When the gelation reagent of the charge-stabilized colloidal crystals was photopolymerized under ultraviolet light using different upper- and bottom-light intensities, it resulted in a gel-immobilized colloidal crystal film with a broadened Bragg reflection peak. Moreover, the width of the Bragg peak increased from 30 to 190 nm as the difference between the light intensities increased. Films with wider Bragg peaks exhibited a brighter reflection color because of the superposition of the shifted Bragg reflections. Furthermore, the Bragg wavelength could be varied over a wide range (500–650 nm) while maintaining the same broadened effective bandwidth by varying the swelling solvent concentration. These findings will expand the applicability of colloidal crystals for use in photonic devices and color pigments.

We explore the potential of nanocrystals (a term used equivalently to nanoparticles) as building blocks for nanomaterials, and the current advances and open challenges for fundamental science developments and applications. Nanocrystal assemblies are inherently multiscale, and the generation of revolutionary material properties requires a precise understanding of the relationship between structure and function, the former being determined by classical effects and the latter often by quantum effects. With an emphasis on theory and computation, we discuss challenges that hamper current assembly strategies and to what extent nanocrystal assemblies represent thermodynamic equilibrium or kinetically trapped metastable states. We also examine dynamic effects and optimization of assembly protocols. Finally, we discuss promising material functions and examples of their realization with nanocrystal assemblies.

Previous reports have shown that colloidal crystal (CC) films with visible Bragg reflection characteristics can be fabricated by the surface modification of monodisperse silica particles (SiPs) with poly(methyl methacrylate) (PMMA) chains, followed by hot-pressing at 150 °C. However, the reflection bands of the CC films were very broad due to their relative disordering of SiPs. In this report, we attempted to fabricate the CC films using SiPs surface-modified with poly(n-octyl acrylate) (POA) chains by hot-pressing. When the cast films of POA-grafted SiPs were prepared by hot-pressing at 100 °C, the reflection bands were narrow rather than those of CC films of PMMA-grafted SiPs. This can be ascribed to easy disentanglement of POA chains during the hot-pressing process, thereby enabling the formation of well-ordered CC structures. Moreover, the reflection colors of CC films could be easily tuned by controlling the molecular weight of POA chains grafted on the SiP surface.

Rapid, sensitive, selective and portable virus detection is in high demand globally. However, differentiating non-infectious viral particles from intact/infectious viruses is still a rarely satisfied sensing requirement. Using the negative space within monolayers of polystyrene (PS) spheres deposited directly on gold electrodes, we fabricated tuneable nanochannels decorated with target-selective bioreceptors that facilitate the size-selective detection of intact viruses. Detection occurred through selective nanochannel blockage of diffusion of a redox probe, [Fe(CN)6]3/4−, allowing a quantifiable change in the oxidation current before and after analyte binding to the bioreceptor immobilised on the spheres. Our model system involved partial surface passivation of the mono-assembled PS spheres, by silica glancing angle deposition, to confine bioreceptor immobilisation specifically to the channels and improve particle detection sensitivity. Virus detection was first optimised and modelled with biotinylated gold nanoparticles, recognised by streptavidin immobilised on the PS layer, reaching a low limit of detection of 37 particles/mL. Intact, label-free virus detection was demonstrated using MS2 bacteriophage (~23–28 nm), a marker of microbiological contamination, showing an excellent limit of detection of ~1.0 pfu/mL. Tuneable nanochannel geometries constructed directly on sensing electrodes offer label-free, sensitive, and cost-efficient point-of-care biosensing platforms that could be applied for a wide range of viruses.

"Coffee rings" structures formed by the evaporation of a nanosphere colloidal drop which rests on a substrate can be grown as thick, good quality colloidal crystals if the drop is settled onto the flat upper side of a pillar in such a way that its spreading is inhibited by the pillar edge. The colloidal crystal thus obtained has a torus shape of a 6 mm in diameter (~ 19 mm in length), with a semi-elliptical cross section (width ~ 0.7 mm, height ~ 1 mm) and has a shape factor (the ratio between its width and its height) around 1, much lower than that formed in a classical manner, onto a semi-infinite surface, which is usually very flat. These microsphere crystals can be detached from the substrate as free-standing, cut and manipulated without special precaution. Growing thick rings in only few hours, in a simple set-up, the method could be useful for the researchers which currently use these colloidal crystals as sacrificial templates for inverse-opals synthesis. [ABSTRACT FROM AUTHOR]

Series of high-quality spherical poly(methyl methacrylate) particles with a polydispersity less than 5% are prepared by chain-growth emulsifier-free controlled radical emulsion polymerization of methyl methacrylate in water. The average diameters in the series varied from 237 nm to 447 nm. The physico-chemical properties of obtained submicrospheres can be varied to make them more stable and stronger by a modified classical synthesis technology whereby 4-10 vol.% of dispersion medium is replaced by acetone. 2D and 3D photonic crystal structures, opals, are prepared from poly(methyl methacrylate) submicrospheres. The crystal structure of the opals is studied by IR spectroscopy and scanning electron microscopy. According to the spectroscopic data, the poly(methyl methacrylate) particles contain significant amounts of water whose evaporation leads to the shrinkage of the spheres. The stereoregularity of the synthesized polymer is studied, the glass-transition temperatures of obtained samples are determined. [ABSTRACT FROM AUTHOR]

A photonic sensor based on inversed opal molecular imprinted polymer (MIP) film to detect the presence of chlorantraniliprole (CHL) residue in tomatoes was developed. Acrylic acid was polymerized in the presence of CHL inside the structure of a colloidal crystal, followed by etching of the colloids and CHL elution. Colloidal crystals and MIP films were characterized by scanning electron microscopy and FT-IR, confirming the inner structure and chemical structure of the material. MIP films supported on polymethylmethacrylate (PMMA) slides were incubated in aqueous solutions of the pesticide and in blended tomato samples. The MIP sensor displayed shifts of the peak wavelength of the reflection spectra in the visible range when incubated in CHL concentrations between 0.5 and 10 μg L−1, while almost no peak displacement was observed for non-imprinted (NIP) films. Whole tomatoes were blended into a liquid and spiked with CHL; the sensor was able to detect CHL residues down to 0.5 μg kg−1, significantly below the tolerance level established by the US Environmental Protection Agency of 1.4 mg kg−1. Stable values were reached after about 30-min incubation in test samples. Control samples (unspiked processed tomatoes) produced peak shifts both in MIP and NIP films; however, this matrix effect did not affect the detection of CHL in the spiked samples. These promising results support the application of photonic MIP sensors as an economical and field-deployable screening tool for the detection of CHL in crops. [ABSTRACT FROM AUTHOR]

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.

A functional lens coating, based on the structure of inversed colloidal photonic crystals, is proposed. The color-reflecting colloidal crystal was first prepared by self-assembly of nano-colloids and was infiltrated by adhesive polymer solution. As the polymer was crosslinked and the crystal array was removed, a robust mesh-like coating was achieved. Such a functional coating has good transmittance and has a shielding efficiency of ~9% for UV–blue light according to different particle sizes of the nano-colloids, making it an ideal functional material.

Quasicrystals have been discovered in a variety of materials ranging from metals to polymers. Yet, why and how they form is incompletely understood. In situ transmission electron microscopy of alloy quasicrystal formation in metals suggests an error-and-repair mechanism, whereby quasiperiodic crystals grow imperfectly with phason strain present, and only perfect themselves later into a high-quality quasicrystal with negligible phason strain. The growth mechanism has not been investigated for other types of quasicrystals, such as dendrimeric, polymeric, or colloidal quasicrystals. Soft-matter quasicrystals typically result from entropic, rather than energetic, interactions, and are not usually grown (either in laboratories or in silico) into large-volume quasicrystals. Consequently, it is unknown whether soft-matter quasicrystals form with the high degree of structural quality found in metal alloy quasicrystals. Here, we investigate the entropically driven growth of colloidal dodecagonal quasicrystals (DQCs) via computer simulation of systems of hard tetrahedra, which are simple models for anisotropic colloidal particles that form a quasicrystal. Using a pattern recognition algorithm applied to particle trajectories during DQC growth, we analyze phason strain to followthe evolution of quasiperiodic order. As in alloys, we observe high structural quality; DQCs with low phason strain crystallize directly from the melt and only require minimal further reduction of phason strain. We also observe transformation from a denser approximant to the DQC via continuous phason strain relaxation. Our results demonstrate that soft-matter quasicrystals dominated by entropy can be thermodynamically stable and grown with high structural quality--just like their alloy quasicrystal counterparts. [ABSTRACT FROM AUTHOR]

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Using a combination of fluorescence and bright-field optical imaging, the solid-state packing structures of semi-confined two-layer spherical colloidal crystals were observed during modulation of an external AC electric field. Upon increasing field strength, the bottom layer of colloids (layer 1) transitioned from the entropically favored hexagonal packing structure with p6m symmetry to a square-packing structure with p4m symmetry. The packing structure of layer 2 was determined by the packing structure of layer 1, with layer 2 particles resting in, and moving in registry with, the low-energy interstitial sites of layer 1. Modulation of the field strength thus resulted in a reversible transition between a face-centered cubic crystal structure and a body-centered cubic crystal structure at low and high field strengths, respectively. These structures were found to be sensitive to the particle density in the wells, with vacancies and insertions leading to the formation of mixed crystal phases at high field strengths. [ABSTRACT FROM AUTHOR]

In this study, a novel strategy for manipulating fluorescence emission of organic dyes is reported, which is based on coupling optical properties of colloidal crystals (CCs) with responsive microgels. Firstly, SiO2 microspheres doped with three kinds of organic dyes (Rhodamine B, RhB; fluorescein isothiocyanate, FITC; commercial cationic Fluorescent Yellow, X-10GFF) were prepared and they were used as the cores to synthesize SiO2/PNIPAm complex microgels doped with organic dyes by free radical polymerization. Then 3D self-assembled CCs of the complex microgels were fabricated by centrifugation. The microstructure of the complex microgel was characterized by Fourier transform infrared (FTIR), transmission electron microscopy (TEM), thermogravimetric (TG), dynamic light scattering (DLS), and differential scanning calorimeter (DSC). Moreover, the effect of doping organic dyes and temperature on self-assembly of the microgels were investigated. Manipulation of fluorescence emission for organic dyes by CCs was studied by photoluminescence (PL) and UV-visible spectrophotometer (UV-Vis). The results indicate that, due to the soft and thermosensitive property of PNIPAm shell, continuous adjustment to the photonic bandgap (PBG) of the CCs can be achieved conveniently by varying concentrations of the complex microgels or ambient temperatures, and when PBG of the CCs overlaps with the fluorescence emission peak of the organic dye, fluorescence emission of the organic dye can be manipulated. [ABSTRACT FROM AUTHOR]