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UV-B radiation acts as an important environmental factor for aging micro-/nanoplastics (MNPs) in the marine environments, while the effect of aged MNPs on plankton is lacking specific research. Referencing to the UV-B radiation intensity in natural environments (2.29 W·m -2 ), we chose the floating polystyrene (PS) MNPs (50 nm, 1 µm) as the research target in this study. The results indicated that UV-B radiation aging for 30 days led to a rougher surface, increased S BET , increased hydrophobicity, and decreased negative charges of PS MNPs. Correspondingly, aged MNPs increased their adsorption abilities for 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), especially for the initial stage. After UV-B radiation aging processes, the individual toxicities of the two sized MNPs on Thalassiosira pseudonana and Brachionus plicatilis both increased, while their joint toxicities with BDE-47 decreased on T. pseudonana but increased on B. plicatilis. The changes in toxicity were more pronounced in 1 µm PS MNPs under air-aged conditions. This study provided the data basis for evaluating the changes of MNPs environmental behaviors under UV-B radiation in the marine environments, with important ecological significance., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Algae-derived organic matter (ADOM) is a key source of chromophoric dissolved organic matter (CDOM) in natural waters. When exposed to solar irradiation, ADOM undergoes gradual degradation and transformation. The escalating presence of microplastics (MPs) can act as a novel type of environmental photosensitizer, however its impacts on ADOM photodegradation remains largely unexplored. Thus, in this study, ADOM were extracted from four common algal species (Microcystis aeruginosa, Synechococcus sp., Chlorella pyrenoidosa and Scenedesmus obliquus) and exposed to UV irradiation with or without polystyrene (PS) MPs, namely ADOM+PS groups and ADOM groups, respectively. The results indicated that a more rapid degradation of amino acid-like substances (∼38 % vs. ∼22 %) and more ammonia products (1.86 vs. 1.21 mg L -1 ) were observed in the ADOM+PS groups compared to the ADOM groups after a five-day exposure. This enhanced photodegradation might be attributed to the production of environmentally persistent free radicals and reactive species during the photoaging of PS. Furthermore, PS-derived high electron transfer belt activity of ADOM led to the production of highly aromatic and humified products. These humic-like products could potentially accelerate the degradation of amino acid-like compounds by exciting the generation of excited triplet CDOM. This study underscores the role of MPs as environmental photosensitizers in promoting ADOM degradation and ammonia generation, providing insights on the transformation of ADOM mediated by emerging pollutants and its impact on aquatic carbon and nitrogen cycles., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Cell sheet engineering represents a new era of precise and efficient regenerative medicine, but its efficacy is limited by the elaborative preparation and the weak mechanics. Herein, a near-infrared (NIR)-triggered dynamic wrinkling biointerface was designed for rapid acquisition of practical cell sheets. The biocompatible NIR can initiate the photothermal-mechanical linkage cascade to efficiently dissolve the collagen supporting layer and release the high-quality cell sheets. The interfacial shear force generates with the dynamic wrinkling, playing an active role in accelerating the cell sheet release. High-quality and self-supporting cell sheets can be harvested within a few minutes, demonstrating a new paradigm of photothermal-mechanical manipulation. The transplantable cell sheets with outstanding physiological and mechanical performances were proven to promote wound healing in skin regeneration. This method may open a completely new front in thermal and mechanical responsive cascade to harvest cell sheets, facilitating their wide applications in regenerative medicine.

Recent developments in the field of polymer vesicles, i.e. polymersomes, have demonstrated that disrupting the equilibrium conditions of the milieu could lead to shape transformation into stable non-spherical morphologies, bringing on-demand shape control to reality and bearing great promise for cell mimicry and a variety of biomedical applications. Here, we studied the self-assembly behavior of glassy amphiphilic triblock copolymers, poly(ethylene glycol)-block-polystyrene-stat-poly(coumarin methacrylate)-block-poly(ethylene glycol) (PEG-b-P(S-stat-CMA)-b-PEG), and their response to various stimuli. By changing the respective molecular weights of both the hydrophobic P(S-stat-CMA) and the hydrophilic PEG blocks, we varied the hydrophobic volume fraction thereby accessing a range of morphologies from spherical and worm-like micelles, as well as polymersomes. For the latter, we observed that slow osmotic pressure changes induced by dialysis led to a decrease in size while rapid osmotic pressure changes by addition of a PEG fusogen led to morphological transformations into rod-like and tubular polymersomes. We also found out that chemically crosslinking the vesicles before inducing osmotic pressure changes led to the vesicles exhibiting hypotonic shock, atypical for glassy polymersomes. We believe that this approach combining the robustness of triblock copolymers and light-based transformations will help expand the toolbox to design ever more complex biomimetic constructs.

In the environment, aging obviously changes physicochemical properties of microplastics (MPs), but the effects of aging process on adsorption behavior of MPs are not fully understood. In this study, the aging of polystyrene (PS) was accelerated by photo-Fenton reaction. The adsorption mechanism of different aged PS toward atorvastatin (ATV) and amlodipine (AML) and the role of PS-derived intermediates in adsorption process were investigated. Results showed that the adsorption of pristine PS toward pharmaceuticals relied on hydrophobic and π-π interaction, while for aged PS, electrostatic interaction and hydrogen bonding controlled the adsorption. The study revealed that the intermediates released from aging process in high concentration (TOC of 10 mg/L) significantly decreased the adsorption of ATV (10 mg/L) on PS (5.0 g/L) but increased the adsorption of AML (10 mg/L). However, those intermediates at environmental concentration (0.1 mg/L) exhibited low effects on adsorption of pharmaceuticals (1.0 mg/L) on MPs (0.5 g/L of PS). The impact mainly depended on electrostatic interaction between MPs and aging intermediates. Besides, the adsorption of low-degree aged PS was more susceptible to the aging intermediates than that of high-degree aged ones. These findings highlight significant implication of MP-derived intermediates in aquatic environments., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Water sensors are a type of level sensor that can be used in various applications requiring the sensing of water levels, such as in dams, nuclear power plants, water pipes, water tanks, and dehumidifiers. In particular, water sensors in water ingress monitoring systems (WIMS) protect lives and property from disasters caused by water leakage and flooding. Here, a resistive water sensor for WIMS that incorporates poly(3,4-ethylenedioxythinophene):poly(styrene sulfonate) (PEDOT:PSS) grafted with poly(ethylene glycol) methyl ether (PEGME) (PEDOT:PSS- g -PEGME copolymer) as high-conductivity electrodes and laser-treated PEDOT:PSS- g -PEGME copolymer as the low-conductivity resistive component is reported. The configuration of the water sensor is modeled as two parallel resistors ( R laser treated PEDOT:PSS || R water ) when water comes into contact with the sensor surface. The two-resistor configuration exhibits a better performance in comparison with single-resistor configurations comprising only PEDOT:PSS- g -PEGME copolymer or laser-treated PEDOT:PSS- g -PEMGE copolymer. Moreover, PEDOT:PSS- g -PEGME copolymer is applied to the sensor to improve the stability of PEDOT:PSS in water. We demonstrate that the sensor can detect the water level in real time with high sensitivity and accuracy, and thus has potential in applications for monitoring water-related hazards.

Pluripotent stem cells (PSCs), especially induced PSCs (iPSCs), have great potential for regenerative medicine. Conventionally, PSCs are cultured and expanded efficiently on feeder cell layers or on cell-adhesive matrices. Large-scale iPSC expansion in an undifferentiated state without laborious culturing procedures and high manufacturing costs for the adhesive matrix is urgently required to integrate iPSCs into therapeutic applications. For this, feeder layers or cell-adhesive matrix coating have to be removed from the iPSC culture system. To enable feeder- and matrix coating-free culture conditions, we focused on a UV/ozone surface treatment technique for polystyrene cell culture substrates to improve PSC adhesion and proliferation. In this study, changes in the molecular structure of UV/ozone-modified polystyrene were characterized to optimize the surface chemistry for iPSC. Mouse iPSCs (miPSCs) were cultured on the UV/ozone-modified polystyrene substrates without feeder layers. As a result, large polymeric chains of polystyrene were dissociated into small polymeric chains and oxidized to form ester and carboxylic acid functional groups by the UV/ozone treatment. Moreover, it was suggested that optimal valance of these modified molecules enabled the feeder- and matrix coating-free culture of miPSC with maintaining pluripotency., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This work reports the development of three-dimensional (3D) semiconducting polymer/graphene (SP/G) networks toward sensitive photocathodic enzymatic bioanalysis. Specifically, the porous 3D graphene was first synthesized via the hydrothermal and freeze-dry processes and then mixed with semiconducting polymer to obtain the designed hierarchical structure with unique porosity and large surface area. Afterward, the as-prepared hybrid was immobilized onto the indium tin oxide (ITO) for further characterizations. Exemplified by sarcosine oxidase (SOx) as a model biocatalyst, an innovative 3D SP/G-based photocathodic bioanalysis capable of sensitive and specific sarcosine detection was achieved. The suppression of cathodic photocurrent was observed in the as-developed photocathodic enzymatic biosystem due to the competition of oxygen consumption between the enzyme-biocatalyst process and O 2 -dependent photocathodic electrode. This work not only presented a unique protocol for 3D SP/G-based photocathodic enzymatic bioanalysis but also provided a new horizon for the design, development, and utilization of numerous 3D platforms in the broad field of general photoelectrochemical (PEC) bioanalysis.

Microplastics that are released into the environment undergo aging and interact with other substances such as organic contaminants. Understanding the sorption interactions between aged microplastics and organic contaminants is therefore essential for evaluating the impact of microplastics on the environment. There is little information available on how the aging of microplastics affects their sorption behavior and other properties. We have therefore investigated the effects of an accelerated UV-aging procedure on polystyrene microplastics, which are used in products such as skin cleaners and foams. Physical and chemical particle characterizations showed that aging led to significant surface oxidation and minor localized microcrack formation. Sorption coefficients of organic compounds by polystyrene microplastics following aging were up to one order of magnitude lower than for pristine particles. Sorption isotherms were experimentally determined using a diverse set of probe sorbates covering a variety of substance classes allowing an in-depth evaluation of the poly-parameter linear free-energy relationship (ppLFER) modelling used to investigate the contribution of individual molecular interactions to overall sorption. The ppLFER modelling was validated using internal cross-validation, which confirmed its robustness. This approach therefore yields improved estimates of the interactions between aged polystyrene microplastics and organic contaminants., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Different from the most extensively used inorganic quantum dots (Qdots) for the current state-of-the-art photoelectrochemical (PEC) bioanalysis, this work reports the first demonstration of polymer dots (Pdots) for novel PEC bioanalysis. The semiconducting Pdots were prepared via the reprecipitation method and then immobilized onto the transparent indium tin oxide glass electrode for PEC biodetection of the model molecule l-cysteine. The experimental results revealed that the as-fabricated Pdots exhibited excellent and interesting PEC activity and good analytical performance of rapid response, high stability, wide linear range, and excellent selectivity. In particular, the PEC sensor could easily discriminate l-cysteine from reduced l-glutathione (l-GSH). This work manifested the great promise of Pdots in the field of PEC bioanalysis, and it is believed that our work could inspire the development of numerous functional Pdots with unique properties for innovative PEC bioanalytical purposes in the future.

The photocleaving dynamics of colloidal microRNA-functionalized nanoparticles are studied using time-dependent second harmonic generation (SHG) measurements. Model drug-delivery systems composed of oligonucleotides attached to either silver nanoparticles or polystyrene nanoparticles using a nitrobenzyl photocleavable linker are prepared and characterized. The photoactivated controlled release is observed to be most efficient on resonance at 365 nm irradiation, with pseudo-first-order rate constants that are linearly proportional to irradiation powers. Additionally, silver nanoparticles show a 6-fold plasmon enhancement in photocleaving efficiency over corresponding polystyrene nanoparticle rates, while our previous measurements on gold nanoparticles show a 2-fold plasmon enhancement compared to polystyrene nanoparticles. Characterizations including extinction spectroscopy, electrophoretic mobility, and fluorimetry measurements confirm the analysis from the SHG results. The real-time SHG measurements are shown to be a highly sensitive method for investigating plasmon-enhanced photocleaving dynamics in model drug delivery systems.

Materials matter in microfluidics. Since the introduction of soft lithography as a prototyping technique and polydimethylsiloxane (PDMS) as material of choice the microfluidics community has settled with using this material almost exclusively. However, for many applications PDMS is not an ideal material given its limited solvent resistance and hydrophobicity which makes it especially disadvantageous for certain cell-based assays. For these applications polystyrene (PS) would be a better choice. PS has been used in biology research and analytics for decades and numerous protocols have been developed and optimized for it. However, PS has not found widespread use in microfluidics mainly because, being a thermoplastic material, it is typically structured using industrial polymer replication techniques. This makes PS unsuitable for prototyping. In this paper, we introduce a new structuring method for PS which is compatible with soft lithography prototyping. We develop a liquid PS prepolymer which we term as "Liquid Polystyrene" (liqPS). liqPS is a viscous free-flowing liquid which can be cured by visible light exposure using soft replication templates, e.g., made from PDMS. Using liqPS prototyping microfluidic systems in PS is as easy as prototyping microfluidic systems in PDMS. We demonstrate that cured liqPS is (chemically and physically) identical to commercial PS. Comparative studies on mouse fibroblasts L929 showed that liqPS cannot be distinguished from commercial PS in such experiments. Researchers can develop and optimize microfluidic structures using liqPS and soft lithography. Once the device is to be commercialized it can be manufactured using scalable industrial polymer replication techniques in PS--the material is the same in both cases. Therefore, liqPS effectively closes the gap between "microfluidic prototyping" and "industrial microfluidics" by providing a common material.

In the present article, the effect of UV on PS-b-PMMA micelles in solution is discussed. Micellar solutions of the amphiphilic poly(styrene-b-methylmethacrylate) block copolymer in selective solvent (methanol for the PMMA block) were exposed to UV radiation, which has simultaneously led to cross linking of the micellar core (PS) and degradation of the micellar corona (PMMA). The kinetics of such process were investigated in situ by means of dynamic light scattering, allowing the measurement of hydrodynamic radius as a function of UV exposure time. Results indicate that the size of micelles has decreased with UV exposure time down to a minimum value. Such reduced size resulted from PMMA degradation, which later promoted aggregation and coagulation because the micellar core was no longer well protected by PMMA. Addition of good solvent for both blocks (toluene) to non-UV exposed micelles has led to core swelling (PS) and, ultimately, system disassembly (free copolymer chain). The effect of adding toluene on the UV-exposed micelles has only caused core swelling as a consequence of the PS cross-linking., (Copyright © 2013 Elsevier Inc. All rights reserved.)

We report the preparation of different functional surface patterns based on the optimization of the photo-cross-linking/degradation kinetics of polystyrene (PS) upon exposure to UV-light. We employed a PS-b-PGA (polystyrene-block-poly(l-glutamic acid)) block copolymer that will, in addition to the surface pattern, provide functionality. By using short irradiation times, PS can be initially cross-linked, whereas an excess of the exposure time provokes the degradation of the material. As a result of the optimization of time of exposure, the use of an appropriate cover, or the incorporation of an appropriate amount of absorbing active species (photoinitiator), different tailor-made surface patterns can be obtained, from boxes to needles. Moreover, in addition to the surface pattern, we introduced changes on the chemical composition of the polystyrene using an amphiphilic block copolymer (for instance, we employ PS-b-PGA) that will provide functional surfaces with major advantages. In particular, the presence of carboxylic functional groups provides a unique opportunity to anchor, for instance polypeptide sequences. We describe the immobilization of polypeptide sequences in precise surface positions that allows the use of the surfaces for protein recognition purposes. The immobilization of the proteins evidence the success of the recognition and opens a new alternative for protein patterning on surfaces for many biotechnological and biomedical applications.

A sensitive surface enhanced Raman scattering (SERS) substrate with metallic nanogap array (MNGA) is fabricated by etching of an assembled polystyrene (PS) spheres array, followed by the coating of a metal film. The substrate is reproducible in fabrication and sensitive due to the nanogap coupling resonance (NGCR) enhancement. The NGCR is analyzed with the finite difference time domain (FDTD) method, and the relationship between the gap parameter and the field enhancement is obtained. Experimental measurements of R6G on demonstrate that the enhancement factor (EF) of the MNGA SERS substrate is increased by more than two fold compared with the control sample.

The autofluorescence intensity of bacteria and fungal spores was quantified by fluorescence microscopy in order to obtain the information for evaluating fluorescence-based bioaerosol detectors and was comparable to that of some types of polystyrene microspheres (PSMs). Although the intensity for microbes was distributed across a wide range over an order of magnitude in gray scale, it was in the intensity range of certain PSMs. Furthermore, some of those bacteria and PSMs were aerosolized in a test chamber and the fluorescence intensity was measured with a bioaerosol detector. Although there was a slight difference in the order of intensity from the results obtained by fluorescence microscopy, the fluorescence-based bioaerosol detector showed the intensity was in a comparable range.

Pellet injection and repetitive laser illumination are key technologies for realizing inertial fusion energy. Numerous studies have been conducted on target suppliers, injectors, and tracking systems for flying pellet engagement. Here we for the first time demonstrate the pellet injection, counter laser beams' engagement and neutron generation. Deuterated polystyrene (CD) bead pellets, after free-falling for a distance of 18 cm at 1 Hz, are successfully engaged by two counter laser beams from a diode-pumped, ultra-intense laser HAMA. The laser energy, pulse duration, wavelength, and the intensity are 0.63 J per beam, 104 fs, and 811 nm, 4.7 × 10(18) W/cm(2), respectively. The irradiated pellets produce D(d,n)(3)He-reacted neutrons with a maximum yield of 9.5 × 10(4)/4π sr/shot. Moreover, the laser is found out to bore a straight channel with 10 μm-diameter through the 1-mm-diameter beads. The results indicate potentially useful technologies and findings for the next step in realizing inertial fusion energy.

The main purpose of this study was to select an appropriate photochromic dye and to develop a series of photochromic indicators showing ultraviolet (UV) degradation of selected background materials made from different polymers. The photochemistry of a series of photochromic compounds of oxazine and diarylethenes in thin polystyrene films were studied with spectroscopic methods. This paper also discusses the design and results of tests of UV photochromic indicators for high-visibility clothing.

We present spatially resolved photovoltage spectra of a bulk heterojunction solar cell film composed of phase-separated poly(9,9'-dioctylfluorene-co-benzothiadiazole) (F8BT) and poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine) (PFB) polymers prepared on ITO/PEDOT:PSS and aluminum substrates. Over both PFB- and F8BT-rich domains, the photopotential spectra were found to be proportional to a linear combination of the polymers' absorption spectra. Charge trapping in the film was studied using photopotential fluctuation spectroscopy, in which low-frequency photoinduced electrostatic potential fluctuations were measured by observing noise in the oscillation frequency of a nearby charged atomic force microscope cantilever. Over both F8BT- and PFB-rich regions, the magnitude, distance dependence, frequency dependence, and illumination wavelength dependence of the observed cantilever frequency noise are consistent with photopotential fluctuations arising from stochastic light-driven trapping and detrapping of charges in F8BT. Taken together, our findings suggest a microscopic mechanism by which intermixing of phases leads to charge trapping and thereby to suppressed open-circuit voltage and decreased efficiency in this prototypical bulk heterojunction solar cell film.

One-dimensionally periodic block copolymer photonic lamellar gels with full-color tunability as a result of a direct exchange of counteranions were fabricated via a two-step procedure comprising the self-assembly of a hydrophobic block-hydrophilic polyelectrolyte block copolymer, polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP), followed by sequential quaternization of the P2VP layers in 1-bromoethane solution. Depending on the hydration characteristics of each counteranion, the selective swelling of the block copolymer lamellar structures leads to large tunability of the photonic stop band from blue to red wavelengths. More extensive quaternization of the P2VP block allows the photonic lamellar gels to swell more and red shift to longer wavelength. Here, we investigate the dynamic swelling behavior in the photonic gel films through time-resolved in situ measurement of UV-vis transmission. We model the swelling behavior using the transfer matrix method based on the experimentally observed reflectivity data with substitution of appropriate counterions. These tunable structural color materials may be attractive for numerous applications such as high-contrast displays without using a backlight, color filters, and optical mirrors for flexible lasing.

Successful treatment for permanent implant brachytherapy is based on accurate measurement of dosimetry parameters for the seed sources. Literature describes the application of various types of phantom to determine the AAPM TG-43 dosimetry parameters for permanent implant seeds. Previously we created a new type of phantom used to measure the dosimetry parameters of a high dose-rate (192)Ir source. In this study, we modified the phantom to suit to a common type of (125)I seed source (Sinko BT-125-1). The dose-rate constant, radial dose function and anisotropy function of this source were measured in detail and compared with the published values of other similar in-design (125)I seed sources. The experimental results exhibit fairly small measurement uncertainties and good self-consistency. The modified phantom is demonstrated on the measurement of dosimetry parameters for the Sinko BT-125-1 (125)I seed, however, it could easily be used for similar measurements of other permanent implantation seed sources.

In this article, we report resistive-pulse sensing experiments with cylindrical track-etched PET pores, which reveal that the diameters of these pores fluctuate along their length. The resistive pulses generated by polymer spheres passing through these pores have a repeatable pattern of large variations corresponding to these diameter changes. We show that this pattern of variations enables the unambiguous resolution of multiple particles simultaneously in the pore, that it can detect transient sticking of particles within the pore, and that it can confirm whether any individual particle completely translocates the pore. We demonstrate that nonionic surfactant has a significant impact on particle velocity, with the velocity decreasing by an order of magnitude for a similar increase in surfactant concentration. We also show that these pores can differentiate by particle size and charge, and we explore the influence of electrophoresis, electroosmosis, and pore size on particle motion. These results have practical importance for increasing the speed of resistive-pulse sensing, optimizing the detection of specific analytes, and identifying particle shapes.

We observed the photo-decomposition process of polystyrene latex (PSL) spheres on a rutile TiO₂(110) single crystal surface by using atomic force microscopy. During the decomposition process, both the height and width of the PSL spheres linearly decreased with the irradiation time in a similar way from the beginning, suggesting that the PSL spheres are isotropically decomposed. This indicates that the interface between the PSL spheres and the TiO₂ surface is not a dominant reaction site, as expected from normal photocatalytic reactions.

We report on a low-level detection of anti-cancer drug (paclitaxel) in blood plasma using microwave-treated gold (Au) film-polystyrene (PS) beads as surface-enhanced Raman scattering (SERS) substrates. SERS spectra of paclitaxel can be acquired within 10s at a concentration of 1×10(-8) M in blood plasma adsorbed on the modified Au-PS SERS substrates. The concentrations of paclitaxel ranging from 1.0×10(-8) to 1.0×10(-7) M in blood plasma can be well estimated with an accuracy of ∼3.8×10(-9) M using SERS technique. This work shows the promise of applying microwave-modified Au-PS as SERS substrates for rapid and accurate monitoring of the anti-cancer drug in blood plasma for immediate treatment decisions during cancer therapy., (Copyright © 2010 Elsevier B.V. All rights reserved.)

The ultrasonic degradation of poly (styrene-co-methyl methacrylate) (SMMA), poly (styrene-co-ethyl methacrylate) (SEMA) and poly (styrene-co-butyl methacrylate) (SBMA) copolymers of different compositions was studied. The copolymers were synthesized and NMR spectroscopy was used to determine the composition, and the glass transition temperatures were determined by DSC. The reactivity ratios were determined by the Kelen-Tudos method and it indicated that the copolymers were random. The effect of solvent, temperature and copolymer composition on the ultrasonic degradation rate of these copolymers was investigated. A model based on continuous distribution kinetics was employed to study the degradation kinetics. The degradation rate coefficients of the copolymers decreased with an increase in the styrene content in the copolymer. At any particular copolymer composition the rate of degradation follows the order: SBMA>SEMA>SMMA. Thermogravimetric analysis (TGA) of the copolymers was carried in order to assess their thermal stability. The same order of degradation was observed for the thermal degradation of the copolymers as that observed for ultrasonic degradation., ((c) 2010 Elsevier B.V. All rights reserved.)

The ultrasonic irradiation (28 kHz, 50 W) in pre-cavitations regime was employed to enhance the degradation rate of styrene-acrylic acid copolymer in aqueous media with nano titania photocatalyst particles. A stainless steel cylindrical sono-photo reactor with capacity of about 1.25 L, equipped with a UV lamp (250 W) was used. The influence of operational parameters, i.e. catalyst concentration, pH and temperature was studied and the role of active species was also distinguished. For an initial substrate concentration of 30 mg L(-1), under mild applied conditions of 30 mg L(-1) of photocatalyst, 25 degrees C and natural pH, a degradation and mineralization conversion of 96% and 91%, respectively, was achieved using sono-assisted photocatalysis process in about only 60 min. These efficiencies are much higher than those obtained with only photocatalysis process. Meanwhile, the threshold of cavitations was found corresponded to catalyst concentration of about 70 mg L(-1). Kinetic studies based on Langmuir-Hinshelwood and power law models in addition to the results from radical scavenger usage revealed that for sono-assisted process, the substrate undergoes degradation mainly via electron-hole redox on the surface of titania particles. It is while for the only photocatalysis process, the reaction proceeds via hydroxyl radicals in the solution bulk., (Copyright (c) 2010 Elsevier B.V. All rights reserved.)

We have been investigating the mid-infrared (MIR) reflection spectrum of microparticles on mirrored substrates. Gold-coated porous alumina filters were used as a substrate to layer the particles and provide consistent reflection spectra. Polystyrene spheres with measured diameters of 0.42 microm were studied using Fourier transform infrared (FT-IR) reflection microspectroscopy, and spectra are shown for coverages in the range 0.5-6 monolayers (ML). Results show that absorption has a nonlinear, stairstep-like dependence on particle coverage and a wavelength dependence that can be explained by electric field standing waves (EFSW) caused by the mirrored substrate. The same effect is found to cause progressive weakening of the observed spectra as a function of increasing wavelength in sub-monolayer coverage measurements. Scattering effects in the spectra are consistent with surface scattering at the antinodes of the EFSW. These observations provide explanations for differences seen between optical properties of particles calculated using the specular-reflection method versus those calculated using traditional aerosol methods. A simple multilayer method for estimating particle absorption coefficients is demonstrated that compares well with values reported using ellipsometry for bulk polystyrene. Another simple method based on submonolayer coverage spectra provides spectra suitable for classification analysis but is only semi-quantitative at determining absorption coefficients.

We present the first optical measurement of a single nitrogen-vacancy (NV) center in a three-dimensional photonic crystal. The photonic crystal, fabricated by self-assembly of polystyrene microspheres, exhibits a photonic stopband that overlaps the NV photoluminescence spectrum. A modified emission spectrum and photon antibunching were measured from the NV centers. Time-resolved fluorescence measurements revealed a 30% increase in the source lifetime. Encapsulation of single NV centers in a three-dimensional photonic crystal is a step towards controlling emission properties of a single photon source.

Polystyrene microtitre plates modified by (60)Co gamma-ray irradiation were used in an indirect enzyme-linked immunosorbent assay (ELISA) for detection of anti-human immunodeficiency virus type 1 (anti HIV-1). The plates with 9 kGy (optimum dose) irradiation showed 2-5-fold higher detection sensitivity in serodiagnosis tests compared to untreated ones, and a 3-fold lower enzyme concentration than the control used was still detectable. Adsorption/desorption experiment results, atomic force microscopy (AFM) images, and X-ray photoelectron spectroscopy (XPS) analysis provide the reason for this improvement. The oxidized surface formed during irradiation presented much more binding affinity for coating antigens and could adsorb a larger amount (1.5-3-fold) of protein uniformly.

We report a novel postgrowth microwave heating implementation by selectively modifying hierarchical polystyrene (PS) bead substrates coated with gold (Au) films to effectively improve the surface-enhanced Raman scattering (SERS) effect on the analytes. The SERS signal of probe molecule rhodamine 6G (Rh 6G) on the microwave-treated Au-PS substrates can be improved by 10-fold, while the detection limit of Rh 6G in concentration can be enhanced by two orders of magnitude compared to the as-growth substrates. The high-quality SERS spectrum of saliva can also be acquired using the modified substrates, demonstrating the potential for the realization of the high-performance SERS substrates for biomedical applications.

We investigate the dynamics of an array of polystyrene micron-sized spheres in a dual-beam fiber-optic trap. Experimental results show non-uniform equilibrium particle spacing and spontaneous self-sustained oscillation for large particle numbers. Results are analyzed with a Maxwell- Stress Tensor method using the Generalized Multipole Technique, where hydrodynamic interactions between particles are included. The theoretical analysis matches well with the experimentally observed equilibrium particle spacing. The theory shows that an offset in the trapping beams is the underlying mechanism for the oscillations and influences both the oscillation frequency and the damping rate for oscillations. The theory presented is of general interest to other systems involving multi-particle optical interactions.

An unconventional and straightforward route to fabricate morphology-controlled 2D ordered carbonaceous nanoarrays is presented. This route is based on the electron irradiation of a polystyrene colloidal monolayer followed by thermal decomposition. This strategy has the advantages of low-cost fabrication and easy manipulation compared to conventional lithography technique and furthermore overcomes the disadvantage of the self-assembly technique that generally has the defect of irregular units in ordered arrays. Various nanoarrays with irregular units, including network-like and star-like ordered arrays as well as hexagonal non-close-packed dot arrays, were fabricated by this novel route. These ordered arrays can be used as templates or masks to fabricate other ordered structures and then can be removed completely by thermal decomposition at a high temperature. Additionally, these arrays are carbonaceous materials that have higher thermal stability and higher refractive index compared with those of the pristine polymer, which are important for real applications such as optical devices. This method might also be used for the fabrication of other unique ordered arrays if different polymer precursor materials are used.

Microwave irradiation can provide a viable alternative to the traditional means such as ultraviolet light and thermal initiation for the preparation of monolithic capillary columns. Polystyrene-based monolithic stationary phases were prepared in situ in fused-silica capillaries and simultaneously in vials. The column permeability, electrophoretic and chromatographic behavior were evaluated using pressure-assisted capillary electrochromatography (pCEC), capillary electrochromatography (CEC) and low pressure liquid chromatography (LPLC). With an optimal monolithic material, the largest theoretical plates for preparing the column could be close to 18,000 plates/m for thiourea in the mode of pCEC. Furthermore, the influence of the composition of the porogenic solvents (toluene/isooctane) on the morphology of organic-based monoliths [poly(styrene-divinylbenzene-methacrylic acid)] was systematically studied with mercury intrusion porosimetry and scanning electron microscopy. The monoliths which were prepared with a high content of isooctane had a bigger pore size and better permeability, and hence resulted in a faster separation.

We prepared polymeric microparticles with coordinated patches using oil-in-water emulsion droplets which were stabilized by adsorbed colloidal polystyrene (PS) latex particles. The oil phase was photocurable ethoxylated trimethylolpropane triacrylate (ETPTA), and the particle-armored oil droplets were solidified by UV irradiation within a few seconds to produce ETPTA-PS composite microparticles without disturbing the structures. Large armored emulsion drops became raspberry-like particles, while small emulsion drops with a few anchored particles were transformed into colloidal clusters with well-coordinated patches. For high-molecular-weight PS particles with low chemical affinity to the ETPTA monomer, the morphology of the patchy particle was determined by the volume of the emulsion drop and the contact angle of the emulsion interface on the PS particle surface. Meanwhile, for low-molecular-weight PS particles with high affinity, the ETPTA monomers were likely to swell the adsorbed PS particles, and distinctive morphologies were induced during the shrinkage of emulsion drops and the phase separation of ETPTA from the swollen PS particles. In addition, colloidal particles with large open windows were produced by dissolving the PS particles from the patchy particles. We observed photoluminescent emission from the patchy particles in which dye molecules were dispersed in the ETPTA phase. Finally, we used Surface Evolver simulation to predict equilibrium structures of patchy particles and estimate surface energies which are essential to understand the underlying physics.

On the basis of the combined technologies of photolithography and reaction-induced phase separation (RIPS), a facile approach has been successfully developed for the fabrication of a micropattern possessing nanoscale substructure on the thin film surface. This approach involves three steps. In the first step, a thin film was prepared by spin coating from a solution of a commercial random copolymer, polystyrene-r-poly(methyl methacrylate) (PS-r-PMMA) and a commercial crosslinker, trimethylolpropane triacrylate (TMPTA). In the second step, photolithograph was performed with the thin film using a 250 W high-pressure mercury lamp to produce the micropattern. Finally, the resulting micropattern was annealed at 200 degrees C for a certain time, and reaction-induced phase separation occurred. After soaking in chloroform for 4 h, nanoscale substructure was obtained. The whole processes were traced by atomic force microscopy (AFM), X-ray photoelectron spectrometry (XPS), and Fourier transform infrared (FTIR) spectroscopy, and the results supported the proposed structure.

Nanocomposites with multi-walled carbon nanotubes (MWNT) and polystyrene (PS) were synthesized via an in-situ bulk sonochemical polymerization under the application of ultrasonication to open pi-bonds in the MWNT, thus enhancing the PS polymerization. Sonication of vinyl monomers such as styrene leads to radical initiation of polymerization. Various characteristics such as morphology, thermal property of the synthesized PS in the presence of the MWNT in the PS/MWNT composites were examined by SEM, TEM, thermogravimetric analysis, respectively. Their rheological properties were also investigated using a stress-controlled rotational rheometer under small amplitude oscillation and steady transient shear in their melt state.

Electromagnetic interference (EMI) shielding characteristics of carbon nanofiber-polystyrene composites were investigated in the frequency range of 12.4-18 GHz (Ku-band). It was observed that the shielding effectiveness of such composites was frequency independent, and increased with increasing carbon nanofiber loading within Ku-band. The experimental data exhibited that the shielding effectiveness of the polymer composite containing 20 wt% carbon nanofibers could reach more than 36 dB in the measured frequency region, indicating such composites can be applied to the potential EMI shielding materials. In addition, the results showed that the contribution of reflection to the EMI shielding effectiveness was much larger than that of absorption, implying the primary EMI shielding mechanism of such composites was reflection of electromagnetic radiation within Ku-band.

Ultrasonically initiated miniemulsion polymerization of styrene in the presence of Fe3O4 nanoparticles was successfully employed to prepare polystyrene (PS)/Fe3O4 magnetic emulsion and nanocomposite. The effects of Fe3O4 nanoparticles on miniemulsion polymerization process, the structure, morphology and properties of PS/Fe3O4 nanocomposite were investigated. The increase in the amount of Fe3O4 nanoparticles drastically increases the polymerization rate due to that Fe3O4 nanoparticles increase the number of radicals and the cavitation bubbles. Polymerization kinetics of ultrasonically initiated miniemulsion polymerization is similar to that of conventional miniemulsion polymerization. PS/Fe3O4 magnetic emulsion consists of two types of particles: latex particles with Fe3O4 nanoparticles and latex particles with no encapsulated Fe3O4 nanoparticles. Fe3O4 nanoparticles lower the molecular weight of PS and broaden the molecular weight and particle size distribution. Thermal stability of PS/Fe3O4 nanocomposite increases with the increase in Fe3O4 content. PS/Fe3O4 emulsion and nanocomposite exhibit magnetic properties. PS/Fe3O4 magnetic particles can be separated from the magnetic emulsion by an external magnetic field and redispersed into the emulsion with agitation.

Rapid, efficient and selective alkene epoxidation and alkane hydroxylation with sodium periodate catalyzed by Mn (TPyP) supported on chloromethylated polystyrene, [Mn(TPyP)-CMP], under ultrasonic irradiation were reported. This catalytic system showed high selectivity in epoxidation of stilbenes and R-(+)-limonene and exhibits a particular ability to epoxidize linear alkenes such as 1-heptene. This supported catalyst can catalyze the oxidation of very inert saturated hydrocarbons as well as alkylbenzene derivatives with NaIO4 under ultrasonic irradiation. Under mild reaction conditions, this catalyst was consecutive reused five times without detectable catalyst leaching and gave over 95% epoxide yield in the epoxidation of styrene.

The photochemical interaction of 193 nm light with polystyrene nanospheres is used to produce particles with a controlled size and morphology. Laser fluences from 0 to 0.14 J/cm2 at 10 and 50 Hz photofragment nearly monodisperse 110 nm spherical polystyrene particles. The size distributions before and after irradiation are measured with a scanning mobility particle sizer (SMPS), and the morphology of the irradiated particles is examined with a transmission electron microscope (TEM). The results show that the irradiated particles have a smaller mean diameter ( approximately 25 nm) and a number concentration more than an order of magnitude higher than nonirradiated particles. The particles are formed by nucleation of gas-phase species produced by photolytic decomposition of nanospheres. A nondimensional parameter, the photon-to-atom ratio (PAR), is used to interpret the laser-particle interaction energetics.

UV/ozone oxidation was combined with a photomasking technique to produce adjacent regions of different chemistry on polystyrene (PS) surfaces. The surface chemistry and topography were studied using AFM, XPS and contact angle measurements. The physicochemical patterns were visualised by the condensation of water vapour upon the surfaces and by the differential attachment of Chinese hamster ovarian (CHO) cells. The orientation of CHO cells on 55 and 125 microm wide oxidised PS strips were measured and found to be highly dependent on the width of the oxidised feature. CHO cells in relatively close proximity to a linear polar/non-polar border showed significant axial alignment along the border. CHO cells can also be confined to specific regions of the polymer surface. Cells attached to larger areas (75 microm x 75 microm) were found to have a smaller average cell size than cells attached to the smaller (56 microm x 56 microm) areas.

Electrohydrodynamics were studied in a trilayer thin film system consisting of two different polymeric layers and air. A polymer with a higher dielectric constant, poly(methyl methacrylate), was sandwiched between air and a lower dielectric constant polymer, polystyrene. An electric field was applied normal to the interfaces. Along with electrostatic forces, dewetting forces were significant at two of the interfaces, namely, the polystyrene/silicon wafer and the polystyrene/poly(methyl methacrylate) interfaces. These two combined forces produce novel closed-cell structures that are difficult to produce by other existing techniques.

A styrene-based water-soluble polymer has been explored for its use as a host for lipophilic substrates in aqueous medium. Unimolecular reactions, namely, photo-Fries rearrangement of naphthyl esters, alpha-cleavage reaction of 1-phenyl-3-p-tolyl-propan-2-one, and Norrish type I and type II reactions of benzoin alkyl ethers were examined. We find that the hydrophobic domains generated by the polymer not only restrict the mobility of the radicals but also modestly incarcerate the substrate, intermediates, and products during the time scale of the reactions. Comparative studies of the same photoreactions in micelles formed from small molecule surfactants and an amphiphilic diblock copolymer demonstrate that the styrene-based water-soluble polymer aggregates in aqueous medium offer better selectivity.

A multiple-trap single-beam scanning laser tweezer system was developed and characterized. Different stationary and mobile multiple-trap modes were generated for polystyrene beads in a water environment. Trapping efficiency and stability were investigated for several dynamic parameters such as transition time between the sites, waiting time on a single site, number of trapping sites, and IR laser power. Optimal parameters for efficient generation of complex arrays and matrices were determined. We demonstrate an example of a single laser beam multiple-trap application by measuring the trap's stiffness in water for our laser tweezer setup.

In this work, a route for the synthesis of inorganic/polymer core/shell composite nanoparticles was proposed, which can be called the antisolvent-ultrasound method. Compressed CO2 was used as antisolvent to precipitate the polymer from its solution dispersed with inorganic nanoparticles, during which ultrasonic irradiation was used to induce the coating of precipitated polymers on the surfaces of the inorganic nanoparticles. TiO2/polystyrene (PS) core/shell nanocomposites have been successfully prepared using this method. The transmission electronic micrographs (TEM) of the obtained nanocomposites show that the TiO2 nanoparticles are coated by the PS shells, of which the thickness can be tuned by the pressure of CO2. The phase structure, absorption properties, and thermal stability of the composite were characterized by X-ray diffraction (XRD), UV-vis spectra, and thermogravimetry, respectively. The results of X-ray photoelectron spectra (XPS) indicate the formation of a strong interaction between PS and TiO2 nanoparticles in the resultant products. This method has some potential advantages for applications and may be easily applied to the preparation of a range of inorganic/polymer core/shell composite nanoparticles.

Nowadays, more than one million percutaneous transluminal coronary angioplasties are being performed annually throughout the world. Restenosis is a significant problem associated with these angioplasty procedures. Radiation treatment with catheter-based beta-emitter sources is currently under clinical trial to prevent this problem. Due to fast and worldwide introduction of beta-sources for intravascular application, there is a growing interest in the dosimetry aspects. However, accurate dosimetry of beta-radiation is more difficult than that of gamma-radiation. Suitable detectors are not yet available with accuracy down to a tenth of a millimeter. Conventional measuring systems are not capable of such spatial resolution, except radiochromic film. However, film dosimeters have limited sensitivity and their radiation characteristics are different than those of tissue; therefore dose measurements require corrections. An alternative is to use water-equivalent plastic scintillators. In this work, organic plastic scintillator (BCF-10) dosimetry is studied using the Monte Carlo (MC) technique PENELOPE, and its radiation stability, after irradiation, is experimentally studied through electron paramagnetic resonance (EPR). Depth dose and dose profile are measured and compared to film dosimetry results. The EPR technique shows that the recovery time is dose independent in this kind of fiber and shows good stability.

Counterpropagating light fields provide a stationary optical potential well for a Brownian particle. Introducing variability in the relative strengths of the counterpropagating beams allows us to create a more general configuration-the optical elevator. An optical elevator dynamically controls the axial location of the potential minimum where the particle finds a stable equilibrium position. We describe the implementation of multiple real-time reconfigurable optical elevators with the generalized phase contrast method for dynamic manipulation of polystyrene spheres and yeast cells S. cerevisiae in three dimensions.

Linear, branched, and arborescent fluoropolymer-Si hybrids were prepared via surface-initiated atom transfer radical polymerization (ATRP) from the 4-vinylbenzyl chloride (VBC) inimer and ClSO(3)H-modified VBC that were immobilized on hydrogen-terminated Si(100), or Si-H, surfaces. The simple approach of UV-induced coupling of VBC with the Si-H surface provided a stable, Si-C bonded monolayer of "monofunctional" ATRP initiators (the Si-VBC surface). The aromatic rings of the Si-VBC surface were then sulfonated by ClSO(3)H to introduce sulfonyl chloride (-SO(2)Cl) groups and to give rise to a monolayer of "bifunctional" ATRP initiators. Kinetics study indicated that the chain growth of poly(pentafluorostyrene) from the functionalized silicon surfaces was consistent with a "controlled" or "living" process. The chemical composition and functionality of the silicon surface were tailored by the well-defined linear and branched fluoropolymer brushes. Atomic force microscopy images revealed that the surface-initiated ATRP of pentafluorostyrene (PFS) had proceeded uniformly on the Si-VBC surface to give rise to a dense and molecularly flat surface coverage of the linear brushes. The uniformity of surfaces with branched brushes was controlled by varying the feed ratio of the monomer and inimer (VBC in the present case). The living chain ends on the functionalized silicon surfaces were used as the macroinitiators for the synthesis of diblock copolymer brushes, consisting of the PFS and methyl methacrylate polymer blocks.

Nonmagnetic particles in a carrier ferrofluid acquire an effective dipolar moment when placed in an external magnetic field. This fact leads them to form chains that will roughen due to Brownian motion when the magnetic field is decreased. We study this process through experiments, theory and simulations, three methods that agree on the scaling behavior over 5 orders of magnitude. The rms width goes initially as t(1/2), then as t(1/4) before it saturates. We show how these results complement existing results on polymer chains, and how the chain dynamics may be described by a recent non-Markovian formulation of anomalous diffusion.