Search

Aqueous-solution-based hybridization approaches based on the chemical conversion of the surface of 2D Cu nanostructures are used to prepare high-performance catalysts.

A novel method that combines the concepts of nanocomposite hydrogels and flow catalysis was developed for the efficient conversion of Cr(vi) to Cr(iii) in water.

In this study, we report that the high-performance transparent conductive films based on silver nanowires (AgNWs) can be fabricated in a single-step spin-coating process by simply introducing a bio...

The preparation of expended polypropylene (EPP) by a bead foam processing is of great significance for their potential applications, but the development of a facile method adopting the actual manufacturing process remains a great challenge. In this study, a new bead foam processing based on the actual manufacturing process was successfully developed to produce high quality EPP. Suitable processing conditions as well as the effect of the precursor sample properties associated with expanded polypropylene (EPP) manufactured by the bead foam process were investigated. The elongational viscosity was firstly measured using polypropylene (PP) samples with different crystallinities and molecular weights in order to investigate the relevant foaming temperatures. The crystallinity and molecular weight of each sample were controlled by the addition of comonomer, and the melting behavior and cell morphology of the foamed specimens were analyzed utilizing a pilot-scale foaming experiment. Based on our results and observations, a plausible mechanism for formation of high quality EPP was proposed. This work offers a new method for fabricating EPP with a high quality by the bead foam processing. It also provides important information about how the morphology and cell numbers of EPP may be finely controlled by the processing conditions.

Thermo-responsive polymers have attracted much attention in recent years because they can provide a variety of applications for smart devices, but the lack of sufficient mechanical properti...

Silver (Ag) nanocrystals with a dendritic structure have attracted intensive attention because of their unique structural properties, which include abundant sharp corners and edges that provide a large number of active atoms. However, the synthesis of Ag dendrites via a simple and environmentally friendly method under ambient conditions remains a challenge. In this paper, we report a simple water-based green method for the production of biopolymer hydrogel beads embedded with Ag dendrites without using an additional reducing agent, stabilizer, or crosslinking agent. The obtained Ag dendrites exhibit a unique two-dimensional (2D) structure rather than a conventional three-dimensional structure because Ag+ ions are reduced on the surface of the solid-phase hydrogel beads and grow into crystals. Reasonable mechanisms explaining the formation of the nanocomposite hydrogel beads and the formation of 2D Ag dendrites in the hydrogel are proposed on the basis of our observations and results. The hydrogel beads embedded the 2D Ag dendrites were used as an environmentally friendly catalytic reactor, and their catalytic performance was evaluated by adopting the reduction of 4-nitrophenol to 4-aminophenol with NaBH4 as a model reaction.

Sharp-tipped anisotropic silver (Ag) nanostructures are attracting increasing attention because of their unusual optical properties. However, the sharp tips make such nanostructures thermodynamically unstable; thus, they have been considered unsuitable for use in colorimetric sensing because of their tendency to aggregate or transform in a solution state. In the present study, a colorimetric sensing platform for detecting bromide (Br−) in an aqueous medium was developed. The platform is based on the localized surface plasmon resonance (LSPR) properties of Ag nanoprisms with sharp tips. The key to using such Ag nanocrystals with extreme anisotropic structures is to adopt a solid-phase sensing platform. A Ag-nanoprism-embedded tough hydrogel with interpenetrating polymer networks was synthesized via aqueous-phase polymerization and crosslinking processes. The Ag nanoprisms immobilized inside the hydrogel were stable and did not exhibit aggregation or degradation over time; specifically, when the hydrogel was dried, the nanoprisms retained their inherent LSPR properties for an extended period. By taking advantage of the rapid and spontaneous morphological transformation of Ag nanoprisms inside the hybrid hydrogel exposed to Br− and the corresponding changes in their LSPR properties, we designed a plasmonic sensing platform for the sensitive and selective detection of Br− in an aqueous medium. The proposed colorimetric sensing platform was found to exhibit a wide sensing range and high selectivity, with a low limit of detection (LOD) of 10 μM, and offers substantial advantages over previously developed systems; specifically, it is portable, eco-friendly, safe to use and handle, stable for extended periods, and enables naked-eye detection. We believe that the as-proposed sensing platform can be used as a point-of-care analytical tool for detecting Br− in a broad range of samples.

Hollow nanostructured polymer microspheres have various potential applications; however, the development of a facile method to synthesize such particles has proved challenging. In the current work, an easy-to-use, green and low-cost method adopting a heterophase polymer dispersion strategy was developed to produce monodisperse hollow microparticles with well-defined nanostructures. When polystyrene (PS) seed microparticles prepared using modified dispersion polymerization were dispersed in an ethanol-water mixture at 70 °C, they transformed into hollow PS microparticles as a result of uptake of the continuous phase by the particles. Via consecutive heterophase polymer dispersion processes involving the addition of metal precursors, hollow PS microparticles covered with bimetallic nanocrystals were obtained. That is, metal nanocrystals were produced in situ from metal precursors on the polymer particles. Based on our results and observations, we propose plausible mechanisms for the formation of these hollow microparticles. The hollow PS microparticles covered with bimetallic nanocrystals exhibited high catalytic activity at a low concentration and excellent reusability when used as catalysts for the reduction of 4-nitrophenol to 4-aminophenol using sodium borohydride as the reducing agent.

The preparation of hierarchical nanoporous films is of great significance for their potential applications, but the development of a facile method to synthesize such films method remains a great challenge. In the current work, hierarchically honeycomb-patterned polydimethylsiloxane (PDMS) films with unique nanostructures were synthesized by simply depositing an acid solution, specifically consisting of a mixture of H 2 SO 4 , HNO 3 , and DI water, on PDMS films displaying regular concave structures. During the post-processing, secondary extrusions were generated on the surfaces of such PDMS films, leading to the formation of highly hierarchical honeycomb-shaped patterns. In the synthesis, the composition of the acid solution played a critical role in the formation and growth of the secondary extrusions. The morphological evolution of the PDMS films during the post-processing proceeded along different pathways depending on the experimental conditions of the process. Based on our results and observations, a plausible mechanism explaining the formation of the hierarchical honeycomb-shaped patterns and the morphological evolution during the synthesis was proposed. The developed approach provides a simple route for fabricating polymer films with unique hierarchical honeycomb-shaped patterns and without the need for any expensive or sophisticated lithographic patterning instruments.

Triangular silver (Ag) nanoplates with sharp corners exhibit fascinating optical properties, but their triangular shapes make them thermodynamically unstable. In the current work, we used this intrinsic instability as the basis for a novel sensing platform for the quantification of water in water-ethanol mixtures. Specifically, we designed a system that uses the color and spectral changes associated with the spontaneous rounding of the sharp corners of triangular Ag nanoplates exposed to bromide ions (Br−) to quantify the water fraction in water-ethanol mixtures. The rate of change of the color and spectral features of a water-ethanol mixture containing Ag nanoplates resulting from the introduction of KBr was found to be strongly correlated with the volume fraction of water in the mixture. This relationship, which was attributed to the dependence of the solubility of KBr on the volume fraction of water in water-ethanol mixtures, allowed the quantification of water in water-ethanol mixtures having any water volume fraction (from 0 to 1.0). The proposed colorimetric sensing platform exhibited reliable sensing results in two real products containing water and ethanol (an alcoholic beverage and an ethanol-based hand sanitizer). It was also successfully applied to determining the relative amount of water in water-isopropyl alcohol mixtures, suggesting that it can be applied to mixtures of water and other alcohols. The present findings suggest that the proposed nanocrystal-based sensing platform holds great potential for use as a point-of-care analytical tool for the quantification of water in the fine chemical, pharmaceutical, and food and beverage industries.

Porous polymer microspheres with interconnective open pores have attracted significant interest, owing to their unique properties as compared to those of traditional microspheres. However, developing a facile synthetic method to produce these unique particles remains a challenge. Herein, a method is proposed to produce highly porous polystyrene (PS) microspheres with interconnective open pores and a uniform size distribution, which were prepared by simply dispersing PS seed particles in an oil-in-water emulsion system. The morphological evolutions of the PS microspheres exposed to different types of oil-in-water emulsions were systematically investigated, and the relationship between the colloidal stability of the emulsions and the final structure of the PS microspheres was studied. Based on these results, the best oil-in-water system for synthesizing highly porous PS microspheres with interconnected open pores was found. The proposed synthetic method was demonstrated to offer significant advantages over previously developed techniques; it was simple, fast, and easy to process, and did not require special additives such as surfactants, complex techniques, etching processes to generate pores, and sophisticated equipment. Catalytic microreactors were fabricated by synthesizing mono- and bimetallic nanocrystals on the surface of the porous microspheres via in situ chemical reduction. When the microreactors were used as a heterogenous catalyst for the 4-nitrophenol (4-NP) reduction reaction by sodium borohydride (NaBH4), they exhibited extremely high catalytic activity and excellent recyclability. These results demonstrated that the highly porous microspheres have very high porosity, huge surface area per unit volume, and good chemical stability, indicating their great potentials as a supporting material for practical applications in catalysis.

Gold (Au) nanocrystal-embedded PDMS films were synthesized by simply depositing a precursor solution on the PDMS film. The resulting PDMS films, inside which many Au nanocrystals with dimensions smaller than 50 nm were uniformly embedded, showed unique nanostructured surface patterns. The morphological evolution of the films proceeded along different pathways depending on whether the film was chemically treated with O 2 plasma. The hybrid films were systematically characterized by carrying out scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy analyses. Mechanisms explaining the formation of the Au nanocrystal-embedded PDMS films and the morphological evolutions during the synthesis were proposed based on the results. The developed approach provides a simple route for fabricating metal nanocrystal-embedded polymer films with unique structures and without the need for special equipment.

This study examined the efficiency of pH-dependent, fluorescent carbon dots for the sensing of hazardous anions in aqueous media and cell imaging. The nitrite anion, an important water-soluble element for environmental and biological systems, requires continuous monitoring because a high concentration can affect the systems severely. The as-synthesized carbon dots efficiently detected the nitrite anion in aqueous solution through a fluorescent ‘Turn Off’ phenomenon. The quenching mechanism was investigated through proper microscopic and spectroscopic studies. The limit of detection and linear detection range were 7.9 nM and 2.3μM-7.7 mM, respectively. The sensitivity was tested with different water samples. In a parallel experiment, the as-synthesized carbon dots were used as a cell-imaging probe for HeLa cells, highlighting their potential in different biological studies.

Although triangular silver (Ag) nanoplates are intrinsically unstable, this characteristic has been taken advantage of in the development of a novel sensing platform. However, most of these applications have relied on halide ions as etchants. In the current work, we used sodium 4-vinylbenzenesulfonate (Na-VBS) as a new powerful etchant of triangular silver (Ag) nanoplates. When aged with Na-VBS at room temperature, Na-VBS etched Ag nanoplates nearly as powerfully as halides did, and these nanoplates rapidly transformed into oblate nanospheroids. This shape evolution permitted tuning of the corresponding localized surface plasmon resonance (LSPR) features of the Ag nanostructures. Interestingly, passivation of the Ag nanoplate surface with melamine was shown to protect the nanoplates from Na-VBS-induced etching. The rate of change of the color and spectral features of the Ag nanoplate solution exposed to Na-VBS was found to be strongly correlated with the concentration of melamine in the solution. This association allowed us to apply this system to the development of a novel platform for sensing melamine.

Hybrid nanostructures comprising plasmonic noble metal and semiconductor have attracted attention owing to their novel properties and potential applications. However, the facile synthesis of these hybrid nanostructures with well-defined heterostructures and high porosity still remains challenging. Herein, we report a facile method for preparing porous triangular Au-Ag-Ag2S bimetal-semiconductor hybrid nanostructures. Following the selective etching of Ag in the Ag-Ag2S hybrid nanostructures, Au was deposited in a controlled manner. Using triangular Ag-Ag2S hybrid nanoplates with new heterostructures as templates and introducing an additional reducing agent in the galvanic replacement reaction with HAuCl4, the prepared Au-Ag-Ag2S had a porous structure, with plasmonic nanocavities on their surfaces and high absorbance in the visible and near-infrared regions. These hybrid nanostructures exhibited enhanced catalytic performance and very high photothermal conversion properties.

To utilize water-responsive hydrogels in biomedical devices and soft robotics, hydrogels with high response speed and good mechanical properties are required. However, fabrication of such hydrogels remains challenging. In this study, a facile method for producing a one-dimensional (1D) hydrogel with water-responsive programmable deformations was developed. A tough hydrogel fiber with an interpenetrating polymer network based on a biopolymer was synthesized using a template-directed method. A 1D hydrogel that shrinks quickly in contact with water was fabricated by simply stretching and drying the hydrogel fiber under ambient conditions. The fabricated 1D hydrogel exhibited excellent mechanical properties, accurately controlled and programmable deformations, and an extraordinarily high degree of deformation with dimensional changes greater than 300%. Based on such 1D hydrogels, one-way soft actuators, which can be bent or can lift a weight when exposed to water, and a chemical sensing platform, which can detect ethanol in a water–ethanol mixture, were developed.

Carbon nanotubes have incorporated in poly(methyl methacrylate) (PMMA) nanocomposites as a synergist of zinc oxalate nanoparticles in order to enhance the flame retardancy. PMMA nanocomposites filled with the newly developed environmentally friendly zinc oxalate nanoparticles and with multi-walled nanotubes (MWNTs), both serving as flame retardants, were prepared by applying the solution blending method. The fire behavior of these composites was systematically studied by carrying out limiting oxygen index (LOI) and pyrolysis combustion flow calorimetry (PCFC) tests. The introduction of MWNTs into the PMMA/zinc oxalate nanocomposites improved the LOI values and markedly decreased the peak heat release rate. It can be suggested that this improvement in the flame retardancy resulted from the formation of stable protective char layers during the combustion process.

The single-step production of Ag nanoplates with high aspect ratios is of great significance for their applications to bendable or stretchable electrodes, but the development of a facile synthetic method remains a great challenge. In this paper, a coordination-based strategy was successfully employed to produce, in a single step, Ag nanoplates with high aspect ratios. Optimal Ag nanoplates were synthesized in the presence of acetonitrile, which served both as the co-solvent and as the ligand to form complexes with the Ag+ ions. Coordination effect of the Ag+ ions by acetonitrile apparently decreased the rate of the reduction of these ions, leading to a decrease in the number of seeds formed in the nucleation step. Decreasing the number of seeds in this way, while keeping the concentration of the Ag precursor constant, resulted in the formation of larger Ag nanoplates. This new synthetic method specifically enabled the formation of Ag nanoplates with lateral dimensions exceeding 1 μm and with thickness values of approximately 30 nm. These Ag nanoplates were found to show electrical percolation in a short sintering time and high electrical conductivity when they were directly used as metal inks to produce conductive patterns for printed electronics.

Soft materials with layered structure such as membranes, block copolymers and smectics exhibit intriguing morphologies with nontrivial curvatures. Here, we report restructuring the Gaussian and mean curvatures of smectic A films with free surface in the process of sintering, that is, reshaping at elevated temperatures. The pattern of alternating patches of negative, zero and positive mean curvature of the air–smectic interface has a profound effect on the rate of sublimation. As a result of sublimation, condensation and restructuring, initially equilibrium smectic films with negative and zero Gaussian curvature are transformed into structures with pronounced positive Gaussian curvature of layers packing, which are rare in the samples obtained by cooling from the isotropic melt. The observed relationship between the curvatures, bulk elastic behaviour and interfacial geometries in sintering of smectic liquid crystals might pave the way for new approaches to control soft morphologies at micron and submicron scales., The self-assembly of soft matter is sensitive to their morphology, which is changeable. Here, Kim et al. show how evaporation and condensation at high temperature modify the surface of a smectic liquid crystal film in a way controlled by the local Gaussian and mean curvature of its layered structure.

Ag nanocrystal-embedded metal–organic frameworks (MOF) were synthesized using a one-pot synthetic method by introducing melamine into a polyol process for the synthesis of Ag nanocrystals. The resulting MOF frameworks showed needle-like structures, inside which many Ag nanocrystals smaller than 10 nm were uniformly embedded, and exhibited electrical bistability reproducibly.

Because water contamination by barium ion (Ba2+) is still common, the ability to detect Ba2+ in aqueous media is important. However, the development of an easy-to-use and point-of-care sensing method for detecting Ba2+ in aqueous media has proven challenging. In the present study, a colorimetric sensing platform for detecting Ba2+ in an aqueous medium was developed. The platform stands on the basis of the localized surface plasmon resonance (LSPR) properties of Ag nanoprisms, where a strong polyelectrolyte, poly(styrene-4-sulfonate) (PSS), is used as a powerful chemical etchant for the nanoprisms. Upon the addition of PSS to a solution of the Ag nanoprisms, the sharp tips of the Ag nanoprisms were immediately etched and the nanoprisms spontaneously transformed into spheroidal nanostructures, giving rise to dramatic changes in their LSPR properties. The chemical etching reaction of Ag nanoprisms exposed to PSS was retarded in the presence of Ba2+, which enabled the design of a new chemical sensing platform for the sensitive and selective detection of Ba2+ in aqueous media. The proposed Ba2+ sensing platform using highly anisotropic Ag nanostructures and a polyelectrolyte etchant offers numerous advantages over existing platforms, including naked-eye recognition and safe use and handling; hence, the developed platform can be used at the point of care.

Ag–Ag2S hybrid nanostructures are of particular interest because of their novel properties and applications; however, the development of a facile method to synthesize Ag–Ag2S hybrid nanostructures with well-defined heterostructures has remained a great challenge. In the current work, a simple and rapid synthetic approach based on the wet-chemical sulfidation of silver (Ag) nanocrystals was developed to prepare Ag–Ag2S hybrid nanoplates with new heterostructures. The key to achieving the unusual hybrid nanostructures was the use of hexagonal Ag nanoplates with anisotropic shapes, and hence spatially varying chemical reactivity, as seed materials. By adjusting the experimental parameters during the sulfidation reaction, Ag–Ag2S hybrid nanoplates with various compositions and morphologies could be obtained, and the localized surface plasmon resonance properties of the hybrid nanoplates could be tuned. The as-prepared Ag–Ag2S hybrid nanoplates were used as photocatalysts for the decomposition of methylene blue under solar irradiation, and their photocatalytic activities and stabilities were investigated. Finally, a facile chemical treatment strategy involving a galvanic replacement reaction was also developed to enhance the photocatalytic activity of the hybrid nanostructures.

Zigzag-shaped Ag nanoplates display unique anisotropic planar structures with unusual jagged edges and relatively large lateral dimensions. These characteristics make such nanoplates promising candidates for metal inks in printed electronics, which can be used for realizing stretchable electrodes. In the current work, we used a one-pot coordination-based synthetic strategy to synthesize zigzag-shaped Ag nanoplates. In the synthetic procedure, cyanuric acid was used both as a ligand of the Ag+ ion, hence producing complex structures and controlling the kinetics of the reduction of the cation, and as a capping agent that promoted the lateral growth of the Ag nanoplates. Hence, cyanuric acid played a crucial role in the formation of zigzag-shaped nanoplates. In contrast to previous studies that reported oriented attachment to be the predominant mechanism responsible for the growth of zigzag-shaped nanoplates, Ostwald ripening was the dominant growth mechanism in the current work. Our findings on the particle...

Most polymers are not inherently stable to light, but this weakness of polymers can be exploited in a positive way. In this paper, we report a simple approach to modifying the surface patterns produced by polystyrene (PS) colloidal crystals by taking advantage of their instabilities under UV illumination. Colloidal crystals grown from PS colloidal suspension were prepared and exposed to the UV light. As a consequence of photochemical reactions, UV irradiation induced morphological changes in the film surface including changes in size and shape of PS particles. Specifically, the particle surface areas illuminated by the UV light in the colloidal crystal films could be controlled by tilting the films, to yield unique surface patterns, including complex and delicate surface patterns. The proposed approach provides a simple route to fabricating colloidal crystal masks with unique structures and without the need for special equipment.

A novel fabrication method has been developed for the preparation of a periodic array of nanoparticle clusters (NPCs) using a sublimable liquid crystal (LC) material. The defect structures of the LC film provide the specific topographical confinement to trap nanoparticles (NPs) and assemble the NPs to generate NPCs during thermal annealing. This system shows a simple regulation of the size of NPCs by varying the concentration of the NP-suspension. Additionally, an illumination system using quantum dots (QDs) is fabricated using the manipulation method reported here.

Silver nanoplates were synthesized by reducing silver nitrate (AgNO3) with poly(vinyl pyrrolidone) (PVP) in N,N-dimethylformamide (DMF). In the synthesis, the hydroxyl end groups of the PVP served as a mild reductant in the kinetically controlled synthesis, and DMF played a critical role as a reaction medium (solvent) for the formation and growth of the nanoplates. In the present study, the growth of the nanoplates proceeded along different pathways, as evidenced by variations in the shape evolution, depending on the PVP to AgNO3 weight ratio. When the concentration of PVP is below a certain value, a large number of small nanoplates with different sizes were initially formed and then fused together along their lateral planes, leading to the formation of a secondary large nanoplate (bimodal particle growth). When the PVP concentration became higher and the surface capping was enhanced, the small nanoplates continued to grow individually without fusing (unimodal particle growth). This study not only advanced our understanding of the role played by PVP in the kinetically controlled synthetic reaction but also allows us to produce Ag nanoplates with a high aspect ratio in a single step.

While there has been remarkable success in generating silver (Ag) nanoplates, and they have considerable potential applications, their degradation behavior in certain environments remains poorly understood. In the current work, we investigated the chemical stability of triangular Ag nanoplates. A one-step water-based synthesis method regulated by the coordination of ligands to Ag cations was successfully employed to produce triangular Ag nanoplates with a high yield. The Ag nanoplates were irreversibly degraded when they were aged with poly(styrene-4-sulfonate) (PSS) at room temperature, and the corresponding localized surface plasmon resonances (LSPR) of the Ag nanoplates changed as well. In contrast, when the Ag nanoplates were aged with potassium persulfate (KPS), the shape evolution of Ag nanoplates was found to depend on the external temperature, and the Ag nanoplate solutions showed different final colors when different external temperatures were applied. These results exhibit important implications for the behavior of triangular Ag nanoplates in a wide variety of plasmonic applications and can be applied to the colorimetric sensing of the temperature history.

The design and preparation of hollow nonspherical microparticles are of great significance for their potential applications, but the development of a facile synthetic method using only one production step remains a great challenge. In the current work, a new template-free method based on dispersion polymerization was successfully developed to produce anisotropic hollow polystyrene (PS) microparticles in a single step. In the synthesis, ammonium persulfate (APS) played a critical role in the formation and growth of highly uniform and stable hollow PS microparticles. By varying the concentration of APS and that of the stabilizer used, polyvinylpyrrolidone, we were able to control the average size of the PS particles and their degree of concavity. Based on our results and observations, a plausible mechanism for formation of these unusually shaped PS microparticles was proposed.

We preprocessed and pickled Deodeok with Doenjang to improve its preservability and to distribute it widely, and we stored Deodeok for 3 weeks at 7°C and measured its quality. The sample pre-treated with 20% of dextrin retained its early texture better than the samples pre-treated with other methods after 3 weeks of storage (p

Dual-scale structures showing superhydrophobic characteristics have been fabricated using sublimable smectic liquid crystals (LCs). Here, toric focal conic domains (TFCDs) of smectic LCs were prepared on micron-sized square pillar patterns. And the layer by layer reconstruction of TFCDs under a thermal sublimation process was followed to form nano-scale hemi-cylinders. Based on this dual-scale roughness, the superhydrophobic surface was successfully created with a water contact angle (CA) of ∼150° and a low CA hysteresis of ∼9°. The resulting superhydrophobic surface is the first application using sublimable LCs, suggesting a new approach for potential applications in LC science and engineering.

There is increasing interest in freshly cut products, that is, foods produced without washing and cutting. In this study, the quality of freshly cut sliced Deodeok was compared with that of what based on its washing methods. In bubble washing, the Deodeok rises to the water surface apace and is broken into centimeter sizes. Microbubble washing calls for the production of a great number of 0.1 mm-sized bubbles in anions-bearing water and their passing through a trumpet-shaped hole at a high pressure. To compare the product deterioration rates of the specimens, they were stored at 10°C for 10 days. In the specimens washed with the control method and with hand washing, the deterioration rate was 80%; and in the specimens washed with bubble and microbubble washing, 20~30%. The L-value (an index of browning) was higher in the bubble and microbubble washing than in the control and the hand washing, which implies that browning was minimized during the storage. As for the viable cell and coliform group counts that were measured during the storage, the specimens washed with the control method showed the highest values. In contrast, the specimens washed with microbubble washing showed the lowest values. In the sensory test, the specimens washed with microbubble were highest in storage preference. In conclusion, the Deodeok that was stored after it was washed with microbubble washing was found to have had the best quality.

The deformation behavior of polymeric colloidal photonic crystals (CPCs) during UV irradiation was investigated. A CPC grown from a polystyrene (PS) colloidal suspension was prepared and exposed to UV light. The UV irradiation resulted in photochemical reactions that induced morphological changes in the surfaces of CPC, including deformations in the sizes, shapes, and packing structures of the PS particles. The crystal morphology evolution resulting from UV irradiation differed significantly from the photoaging behavior observed during exposure to a light source that mimicked natural sunlight. The structural deformations destroyed the optical properties (by deteriorating the photonic bandgap). The UV irradiation induced photooxidation processes that altered the composition of the polymer material surface. Open image in new window

The white-colored inner surface of a polypropylene (PP) material containing water discolored and turned yellow. The discoloration occurred selectively on the surface at the point of contact with the air–water interface. Since the polymer surface was exposed to water in darkness at room temperature, no sign of deterioration or degradation of the polymer at the discolored surface was confirmed. This study conducts an in-depth analysis of the discoloration mechanism of the polymer surface. A variety of technical approaches, including microscopic, spectroscopic, and chromatographic analysis techniques, were used to investigate the nature of discoloration and the root cause. From the analysis results, the discoloration was ascribed principally to a phenol transformation compound having the structure of a quinone methide, which was identified as a degradation product of a primary antioxidant. Based on the observations and experimental results, a plausible discoloration mechanism was proposed.

Since most polymers are not inherently stable to light, their photochemical behavior remains a subject of constant interest. In this study, we investigated the photoaging behavior of polymeric colloidal photonic crystal films. As a consequence of photochemical reactions containing chain-scission, photoaging induced morphological changes in the film surface including changes in the size, surface roughness, shape, and packing structure of PS particles. These structural modifications came about the deterioration of optical properties (photonic bandgap) during photoaging. Based on our results and observations, a plausible correlation between the evolutions of the optical properties and the structural modifications during photoaging was established. Finally, the compositional modifications of the surface based on oxygen incorporation behavior caused by the photooxidation process are discussed based on the ATR–FTIR and XPS analyses.