Microwire formation based on dielectrophoresis of electroless gold plated polystyrene microspheres

Microspheres coated with a perfectly conductive surface have many advantages in the applications of biosensors and micro-electromechanical systems. Polystyrene microspheres with the diameter of 10 μm were coated with a 50 nmthick gold layer using an electroless gold plating approach. Dielectrophoresis （DEP） for bare microspheres and shelled microspheres was theoretically analysed and the real part of the Clausius Mossotti factor was calculated for the two kinds of microspheres. The experiments on the dielectrophoretic characterisation of the uncoated polystyrene microspheres and gold coated polystyrene microspheres （GCPMs） were carried out. Experimental results showed that the gold coated polystyrene microspheres were only acted by a positive dielectrophoretic force when the frequency was below 40M Hz, while the uncoated polystyrene microspheres were governed by a negative dielectrophoretic force in this frequency range. The gold coated polystyrene microspheres were exploited to form the rnicrowire automatically according to their stable dielectrophoretic and electric characterisations.

One-step polymerized lanthanide-based polystyrene microsphere for sensitive lateral flow immunoassay

Lateral flow immunoassays(LFIAs)provide a powerful tool for rapid real-time assay of cancer biomarkers,which is vital for cancer detection and treatment follow-up.Lanthanide-based LFIAs is one of the most widely used methods,especially Eu(Ⅲ)chelates,which possess distinctive and attractive characteristics,such as time-resolved fluorescence and large Stokes shift.Herein,we adopted a new onestep mini-emulsion polymerization method to synthesize carboxyl-modified fluorescent microsphere(OS-EuCM),which shows good stability,resistance to non-specific adhesion and uniform particle size distribution compared with traditional microspheres synthesized through the swelling method.Benefiting from the above advantages,OS-EuCM was successfully used in LFIAs to detect tumor marker Alpha-fetoprotein with high sensitivity and selectivity in concentration as high as 320 ng/mL,as well as a detection limit of 0.683 ng/mL This lanthanide-based microsphere holds great potential for rapid pointof-care screening and clinical application.

Seed-mediated growth of gold nanoparticles using self-assembled monolayer of polystyrene microspheres as nanotemplate arrays

Arrays of noble metal nanoparticles show potential applications in （bio-）sensing, optical storage, surface-enhanced spectroscopy, and waveguides. For all such potential devices, controlling the size, morphology, and interparticle spacing of the nanoparticles is very important. Here, we combine seed-mediated growth with nanosphere lithography to study the controllable growth of gold nanoparticles （Au NPs）, in which the self-assembly monolayer of polystyrene （PS） on a silicon surface is used to guide the modification of allaunesilanes and the subsequent adsorption of gold seeds; seed-mediated growth is applied to controlling the morphology and size of Au NPs. The size of adsorption region （determining the number of adsorbed gold seeds） is controlled by etching PS microspheres with oxygen plasma or annealing PS microspheres at the glass transition temperature. The size and morphology of the Au NPs are controlled by changing growth conditions. In such a way, we have achieved the dual control of the obtained Au NPs. Preliminary results show that this strategy holds a great promise. This approach can also be extended to a wide range of materials and substrates.

Polystyrene microsphere-immobilized palladium(Ⅱ)porphyrin as mild,reusable,and highly efficient catalyst for Heck reaction

A novel Heck reaction catalyst consisting of a palladium（ll） complex of meso-tetra（p- hydroxyphenyl）porphyrin （MTP） and cross-linked chloromethylated polystyrene microspheres （PMs） was successfully prepared via covalent ether bonds between the chloride groups in the PMs and the hydroxyl groups in MTP. The catalyst was characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, and inductively coupled plasma atomic emission spectroscopy （ICP-AES）. This polystyrene-supported palladium-complex was an efficient heterogeneous catalyst for cross-coupling of aryl iodides with ethyl acrylate. The reaction of iodobenzene and ethyl acrylate under N2 at 100 °C and a catalyst concentration of 0.1% gave a gas chromatography product yield of 99.8%, which is much higher than that achieved using a free palladium（II） complex of MTP as the catalyst （41.3%）. The catalyst was recycled up to six times without significant loss of catalytic activity. These results suggest that the immobilized palladium（II） MTP catalyst has potential applications in synthetic and industrial chemistry.

Preparation of microsized crosslinked microspheres by dispersion copolymerization of polystyrene/polyethylene glycol 200-dimethacrylae

Dispersion copolymerization of styrene with polyethylene glycol 200-dimethacrylae as the cross-linking agent was completed by using poly（N-vinyl pyrrolidone） and 2,2-azo-bisisobutyronitrile as the steric stabilizer and initiator, respectively. Crosslinked copolymeric microspheres were prepared directly by the one-step method of dispersion copolymerization. The effects of the content of polyethylene glycol 200-dimethacrylae on the particle morphology and the copolymerization rate were investigated. It shows that the crosslinking agent plays an important role in the particle morphology and the system stability. When the content of crosslinking reached 2.5wt%, the floriated particles were obtained.

Facile and Controllable Assembly of Multiwalled Carbon Nanotubes on Polystyrene Microspheres

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.

A Miniature Fiber Tip Polystyrene Microsphere Temperature Sensor With High Sensitivity

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 pm,a high OPD-temperature sensitivity of about-0.61796nm/℃and a good linearity of 0.9916 were achieved in a temperature range of 20℃-70℃.

Polystyrene Microspheres Coupled with Hybridization Chain Reaction for Dual‑Amplified Chemiluminescence Detection of Specific DNA Sequences

We report on a highly sensitive chemiluminescence(CL)assay for the detection of specific DNA sequence,where streptavidin-modified polystyrene microspheres(PS–SA)coupled with hybridization chain reaction(HCR)were employed as dual amplification platform.Briefly,a“sandwich-type”detection strategy was proposed in our design,which involved capture probe DNA immobilized on the surface of carboxyl-terminated magnetic beads(MB)and the reporter DNA combined with the HCR trigger immobilized on the surface of PS–SA.After that,two hairpin-type monomers were added to initiate the HCR.In the detection system,CL signal was obtained via the instantaneous derivatization reaction between 3,4,5-trimethoxylphenylglyoxal(TMPG)and guanine bases in the target and the HCR complex binding on the magnetic beads.As compared to traditional sandwich type(capture/target/reporter)assays,this dual-amplified strategy for sequence-specific DNA detection showed better specificity,lower detection limit and wider linear response range(linear range of 0.01 fmol–10 pmol and a low detection limit of 5 amol).Moreover,this approach could be easily extended to detect a wide range of specific DNA sequences by modification of the hybridization region.We believe this simple technique will present a significant step towards early diagnoses of diseases.

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

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

Preparation and Catalytic Performance of Microporous Polymer/Au Nanoparticles Composite Microspheres

Polystyrene crosslinked microspheres were prepared by soap-free emulsion polymerization using styrene (St) and divinylbenzene (DVB) as monomers;then,the microporous structure was knitted by the Friedel-Crafts alkylation reaction,and the Au nanoparticles (AuNPs) were loaded into the pores through thermal reduction,to obtain AuNPs/ hyper-crosslinked microporous polymer composite microspheres.SEM and particle-size test results show that the microspheres show good monodispersity.The micropore analysis indicates that the specific surface area and the pore volume of the microporous polymer microspheres decrease with increasing DVB content,and when the DVB content is 0.1%,the specific surface area reaches a maximum of 1 174.6 m2/g.After loading AuNPs,the specific surface area and the amount of micropores of the composite microspheres decrease obviously.The results of XRD and XPS analyses suggest that HAuCl4 is reduced to AuNPs.The composite microspheres show a good catalytic performance for the reduction catalyst of 4-nitrophenol.

A review of recent progress in preparation of hollow polymer microspheres

The preparation methods of hollow polymer microspheres both at home and abroad are summarized, and their preparation mechanisms and developmental states are presented. These methods include the liquid droplet method, dried-gel droplet method, self-assembly method, microencapsulation method, emulsion polymerization method and the template method. Hollow polystyrene microspheres are the most extensively studied in the research of hollow polymer microspheres. Through comparison of the advantages and disadvantages of different preparation methods, it is concluded that microencapsulation method is most suitable for preparing polystyrene hollow microspheres.

Metathesis of 1-butene and 2-butene to propene over Re_2O_7 supported on macro-mesoporous γ-alumina prepared via a dual template method

Macro-mesoporous γ-alumina support（MMA） was prepared by a sol-gel route in aqueous medium using pseudo-boehmite as aluminum source and polystyrene microspheres and Pluronic P123 as hard and soft dual templates,respectively.MMA had a BET specific surface area of about 259 m2 g-1,total pore volume of about 1.61 cm3 g-1,macropore diameter of about 102 nm,and mesopore diameter of about 14 nm.Re2O7/MMA and conventional Re2O7/Al2O3 were prepared by a incipient-wetness impregnation method,and their catalytic performances in the metathesis of 1-butene and 2-butene were tested in a fixed-bed tubular reactor.The result showed that Re2O7/MMA possessed higher activity and far longer working life-span than conventional Re2O7/Al2O3.

Fabrication of macroporous polystyrene/graphene oxide composite monolith and its adsorption property for tetracycline

Macroporous polystyrene microsphere/graphene oxide（PS/GO） composite monolith was first prepared using Pickering emulsion droplets as the soft template. The Pickering emulsion was stabilized by PS/GO composite particles in-situ formed in an acidic water phase. With the evaporation of water and the oil phase（octane）, the Pickering emulsion droplets agglomerated and combined with each other, forming a three-dimensional macroporous PS/GO composite matrix with excellent mechanical strength. The size of the macrospores ranged from 4 mm to 20 mm. The macroporous PS/GO composite monolith exhibited high adsorption capacity for tetracycline（TC） in an aqueous solution at p H 4–6. The maximum adsorption capacity reached 197.9 mg g 1at p H 6. The adsorption behaviour of TC fitted well with the Langmuir model and pseudo-second-order kinetic model. This work offers a simple and efficient approach to fabricate macroporous GO-based monolith with high strength and adsorption ability for organic pollutants.

Comparison of Two Rhodamine-Polyamine Polystyrene Solid-phase Fluorescence Sensors for Hg(Ⅱ) Detection Based on Theoretical Calculation

Two novel rhodamine-based polystyrene solid-phase fluorescence sensors PS-PA-Ⅰ and PS・PA-Ⅱ with different lengths of polyamines were synthesized for Hg(Ⅱ)determination.Thedetection mechanism involving the Hg(Ⅱ)chelation-induced spirocycle open of rhodamine was proposed with the aid of theoretical calculation.The stronger N—Hg bond and the longer polyamine chain in PS-PA-Ⅱ led to a better selectivity,much higher and more quickly fluorescence response to Hg(Ⅱ).

Application of Optical Tweezers in the Research of Molecular Interaction between Lymphocyte Function Associated Antigen-1 and Its Monoclonal Antibody

Lymphocyte function associated antigen-1 （CD11a/CD18, LFA-1） plays an important role in the structure of the immunological synapse and is required for efficient lysis of cytotoxic T lymphocytes （CTLs） and natural killer （NK） cells. To study the activation mode of LFA-1 on the NK cell surface, optical tweezers were used in the work. As an emerging technology, optical tweezers are widely used to manipulate microscopic objects and measure the forces of molecular interactions in the field of biological research. In our study, a new platform was constructed to study the single molecular behavior of receptor on cell surface using optical tweezers. Based on the platform, the interaction between an NK cell and a polystyrene microsphere coated with anti-LFA-1 antibody was observed. The result confirmed that the adhesion forces between an NK cell and a polystyrene bead were time-dependent. According to our findings, we propose that anti-LFA-1 antibody may cause the clustering of LFA-1 on NK cell surface. Cellular ＆ Molecular Immunology.