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With the increasing difficulty in exploitation of low-permeability, high water content and other unconventional reservoirs, a new kind of proppants that possess not only ultra-light weight and high strength and but also hydrophobic performances have attracted more and more interests. Here, this kind of proppants were designed and prepared successfully in the form of polymer microspheres. What's more is that the polymer microspheres (named O-MSDBs) showing high strength and stable hydrophobicity were prepared by a one-step suspension polymerization between styrene, divinyl benzene and γ-methacryloxypropyl-trimethoxy silane accompanying with the formation of silica through sol–gel process. When compared with reported ultra-lightweight proppants (ULWPs), the O-MSDBs not only perform better in ultra-lightweight (0.9917 g·cm−3) and are comparable in high strength (low crushing ratio of 0.89–2.53% at 55–69 MPa), but also show new hydrophobic function. The water contact angle on the surface of O-MSDBs is 140.7° that keeps about more than 80% after mechanical abrasion or acid dissolution. The one-step facile preparation method and brilliant performances make O-MSDBs very promising to large-scale preparation and widely applied in fracturing technology as proppants. [ABSTRACT FROM AUTHOR]

A fiber-optic temperature sensor based on fiber tip polystyrene microsphere is proposed. The sensor structure can be formed simply by placing and fixing a polystyrene microsphere on the center of an optical fiber tip. Since polystyrene has a much larger thermal expansivity, the structure can be used for high-sensitive temperature measurement. By the illuminating of the sensor with a broadband light source and through the optical Fabry-Perot interference between the front and back surfaces of the polystyrene microsphere, the optical phase difference (OPD) or wavelength shift can be used for the extraction of temperature. Temperature measurement experiment shows that, using a fiber probe polystyrene microsphere temperature sensor with a spherical diameter of about 91.7 µm, a high OPD-temperature sensitivity of about −0.617 96 nm/°C and a good linearity of 0.991 6 were achieved in a temperature range of 20°C–70°C. [ABSTRACT FROM AUTHOR]

Through liquid phase deposition (LPD) of TiO2 photocatalyst films on an 800 nm polystyrene (PS) microsphere template, this study prepared a porous, LPD-TiO2 hollow layer (HL) with high specific surface area. An aqueous solution of ammonium hexafluorotitanate mixed with boric acid was used to prepare a TiO2 photocatalyst film. The effects of H3BO3 concentration and PS microsphere solid content on the surface morphology, film composition, and photocatalytic property of the films were investigated. The findings revealed that the LPD-TiO2 hollow film prepared using 0.6 M H3BO3 and a substrate containing 0.4 wt% PS microspheres had higher specific surface area and hydrophilicity than a LPD-TiO2 dense layer (DL). Such properties considerably increase the degradation efficiency of a photocatalyst film. After 6 h, the degradation achieved by the LPD-TiO2 hollow layer prepared using a substrate with PS microsphere concentration of 0.4 wt% was 90.7%, whereas that achieved by the dense LPD-TiO2 was only 64.7%. Moreover, the porous, hollow LPD-TiO2 film exhibited excellent photocatalytic performance and may be widely applied to environmental purification in the future. [ABSTRACT FROM AUTHOR]

Particle shape is one of the most important parameters that can influence the characteristics and properties of dispersion systems. In this study, we have developed a straightforward and facile method to generate oblate spheroidal particles via a film squeezing process. Representative methods so far developed to prepare oblate spheroidal particles, such as film blowing and mechanical stretching based on a biaxial process, have serious problems, including being difficult methods to adopt, very low yield, and non-uniform particle size. Our film squeezing process involves simply squeezing a sandwiched array comprised of an arbitrarily shaped film with embedded polymer spheres between two identical circular elastomeric sheets, on the basis that homogeneous deformation is possible in the mid-plane of simple squeeze flow. This method utilizes a unified uniaxial process for producing both prolate and oblate spheroidal particles. The advantages of the method are easier access, much higher yield, and more uniform sizes and shapes than previously reported methods. This process can be helpful for the fundamental studies utilizing oblate spheroidal particles with controlled geometries. [ABSTRACT FROM AUTHOR]

The unique photoproperties of quantum dots are promising for potential application in bioassays. In the present study, quantum dots were applied to a luminescent oxygen channeling assay. The reaction system developed in this study was based on interaction of biotin with streptavidin. Carboxyl-modified polystyrene microspheres doped with quantum dots were biotinylated and used as acceptors. Photosensitizer-doped carboxyl-modified polystyrene microspheres were conjugated with streptavidin and used as donors. The results indicated that the singlet oxygen that was released from the donor beads diffused into the acceptor beads. The acceptor beads were then exited via thioxene, and were subsequently fluoresced. To avoid generating false positives, a high concentration (0.01 mg/mL) of quantum dots is required for application in homogeneous immunoassays. Compared to a conventional luminescent oxygen channeling assay, this quantum dots-based technique requires less time, and would be easier to automate and miniaturize because it requires no washing to remove excess labels. [ABSTRACT FROM AUTHOR]

Composite films composed of polystyrene (PS) microsphere monolayers and gold (Au) and/or silver (Ag) nanoparticles (NPs) decorations were prepared by a novel size-dependent filtration effect on close-packed PS microsphere arrays. The uniform pores inlaid in the PS monolayer films acted as the transport tunnels for NPs. The steric restriction induced by the size of the pores was used as a main strategy to fabricate hybrid micro/nano films, which were composed of PS microspheres with inhomogeneous anisotropic decorations. The Au and Ag NPs were used as the building blocks to decorate the PS microspheres through a layer-by-layer self-assembly technique with the aid of polyelectrolyte coupling agents. Only the small particles which could pass through the micropores could reach to and deposit on the inner surfaces of the PS microsphere monolayer films. Large particles remained on the outside and could only deposit on the outer surfaces. Thus, the inhomogeneous anisotropic decoration was obtained. This study provides a novel strategy for fabricating anisotropic micro/nanostructures by the size-dependent filtration effect of NPs on porous films and has the potential in applications of anisotropic self-assembly, sensor, and surface modifications at nanoscale. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this paper, we report the controlled fabrication of ordered arrays of pumpkin-shaped (i.e., shapes having the equatorial diameter greater than the polar diameter and being flattened at the poles) Janus polystyrene (PSt) particles with tailored morphologies. It is based on simple microcontact hot embossing of monodispersed PSt microsphere monolayers using different stamps such as glass slides, colloidal sphere monolayers, and wrinkled sheets. The resultant pumpkin-shaped particles have the stamp-defined surface topographies, with one side flat and the other flat or patterned with small beads/holes and striped/dotted bulges. We systematically investigate the effect of the embossing conditions on the surface morphologies, which include the annealing temperature/time, the external load, and the structured stamps. Benefiting from the hexagonal close packing of original symmetric microspheres, well-ordered Janus particle arrays are obtained using the combined bottom-up/top-down strategy. Compared with the traditional two-stage process of fabrication and self-assembly, this method is much simpler and more straightforward, which is of significant importance for the related applications. [ABSTRACT FROM AUTHOR]

High-quality three-dimensional ordered TiO hollow-spheres (3DOH-TiO) materials were fabricated using polystyrene spheres colloidal crystals (ca. 290 nm in center-to-center distance) as sacrificial templates and titanium tetrachloride as titanium sources. The obtained samples were characterized by X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and N adsorption-desorption. The results showed that the films are composed of a closely packed, hexagonal array of the TiO hollow-spheres with a center-center separation of ca. 260 nm. The homogeneity in the shell thickness (ca. 40 nm), the physical contact among adjacent hollow-spheres, and the long-range order in the sample were also confirmed by FESEM and TEM analysis. HRTEM results indicated the walls of the hollow-spheres consist of anatase TiO nanoparticles (15-20 nm). The porous framework structure of the 3DOH-TiO films was further characterized using N physical adsorption, and the Brunauer-Emmett-Teller specific surface area and the total pore volume are around 77.72 m/g and 0.262 cm/g, respectively. [ABSTRACT FROM AUTHOR]

Herein a facile and controllable heterocoagulation between polystyrene (PS) microspheres and multiwalled carbon nanotubes (MWCNTs) is introduced based on colloid thermodynamics. The MWCNTs play the role of steric stabilizer for stabilizing the metastable PS microspheres and thus immobilize spontaneously on the surface of PS microspheres. The synthesized MWCNTs-coated PS composite particles have been extensively characterized by scanning electron microscopy, transmission electron microscopy, thermogravimetry and Raman spectroscopy. The results indicate that the structure and morphology of the resultant MWCNTs-coated PS composite particles are significantly affected by the weight ratio of PS and MWNCTs and the amount of poly(vinylpyrrolidone) that is injected into PS dispersion before they are mixed with MWCNTs. Therefore, these composite particles have the potential to produce MWCNTs-based composite materials with controllable mass loading and dispersity of MWCNTs. [ABSTRACT FROM AUTHOR]

The fabrication of highly dense gold nanoparticles (NPs)-coated sulfonated polystyrene (PS) microspheres and their application in surface-enhanced Raman spectroscopy (SERS) were reported. After the preparation of PS microsphere using dispersion polymerization and subsequent sulfonation, [Ag(NH)] ions were adsorbed on the surfaces of the sulfonated PS microspheres and then reduced to silver nanoseeds for further growth of gold NPs shell by seeded growth approach. Reaction conditions such as the concentration of the growth solution and growth time were adjusted to achieve nonspherical gold NPs-coated PS microspheres with different coverage degree. The application of the as-prepared spiky gold NPs-coated PS microsphere hybrid composite in SERS was finally investigated by using 4-aminothiophenol as probe molecules. The results showed that as-prepared gold NPs-coated PS microspheres could be used as functional hybrid materials to exhibit excellent enhancement ability in SERS. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Gold (Au) nanoparticle arrays with tunable morphology and optical characteristics were synthesized by in-situ self-assembly process that occurred on the surface of aniline-modified polystyrene (PS) microspheres. The method can be used to control the growth of both single and aggregated Au nanoparticle arrays on PS microsphere surface. This method could also be adapted for synthesis of other noble metals hybrid materials, which opens exciting opportunities for their practical applications. [ABSTRACT FROM AUTHOR]