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We have studied photoluminescence (PL) properties of vacuum pump mineral oil as a function of the type and intensity of ionizing radiation exposure. The mineral oil has a simple aliphatic structure, which possesses no chromophore in the traditional sense. Unexpected PL in the mineral oil has characteristic features such as variation of the emission peak wavelength depending on the excitation wavelength and intensity dramatically increasing with radiation dose. The observed behavior can be understood in the framework of a previously suggested model introducing aggregation-induced PL and the formation of conjugated clusters comprising nontraditional chromophores. Our findings can be used for the development of optical sensors for real-time monitoring of oil utilized in vacuum pumps in nuclear fusion reactors. [ABSTRACT FROM AUTHOR]

Helium ion microscopy (HIM) is a relatively new high-resolution nanotechnology imaging and nanofabrication tool. HIM offers a near-molecular resolution (approaching that of TEM) combined with a simplicity of sample preparation and high depth of field similar to SEM. Simultaneously, the technique is not limited by the surface roughness as scanning probe microscopy (SPM) techniques or by the surface charging or radiation damage like SEM. In our review, we consider general principles, advantages, and prospects of HIM application in polymer science. Examples of high-resolution imaging of polymer-based nanocomposites, polymer nanoparticles, nanofibers, nanoporous materials, polymer nanocrystals, biopolymers, and polymer-based photovoltaic and sensor devices are presented. We compare the HIM’s applicability with other modern imaging techniques: SPM and SEM.

We explored two approaches to recover uranium and plutonium from aqueous solutions at pH 4 and pH 7 using water-soluble star-like polyacrylamide polymers with a dextran core. In the first approach, a solution comprising a neutral or ionomer polymer was mixed with a radionuclide solution to form polymer–metal complexes that were then retained by ultrafiltration (UF) membranes under applied pressure. The same polymers were first deposited on the membrane in the second approach using pressure-driven flow. The applied polymers had an overall diameter of gyration of 120 nm, which exceeded the nominal diameter of the UF membrane pores. The polymers showed a high affinity to uranyl but could also be used to extract Pu from neutral or near-neutral pH solutions. Direct-flow single-step filtration and alpha spectrometry demonstrated that the UF membranes containing star-like copolymers could recover 99% of U and up to 60% of Pu from deionized water after filtering 15 mL solutions containing 25 ppm and 33 ppb of the actinides, correspondingly. The sorption capacity of the polymers for uranium could be measured as 1mg U per mg of the polymer after six subsequent filtration steps. Alpha spectroscopy of the deposited actinides revealed peculiarities of the structural organization of polymers and their complexes with U or Pu, depending on the approach. Though both approaches were efficient, the second approach (deposition of the polymer on the membrane followed by filtration) has an additional advantage of protecting the membrane pores from capillary collapse by filling them with the polymer chains. Therefore, these polymer-modified membranes could be used either in continuous or multi-step filtration process with drying after each step without deterioration of their sorption characteristics. [ABSTRACT FROM AUTHOR]

Plastic scintillators (PS) allow design of portative lightweight devices for quantification of low‐activity radiation sources. We have recently suggested a new type of organic fluorophores based on triphenyl pyrazoline (PZ) derivatives with high fluorescence quantum yield showing high radioluminescence when combined with a polyvinyltoluene (PVT) matrix. In this publication we report on radioluminescence properties of the PZ−X family with various halogen substitution (X=F, Cl, Br, I), or having vinyl functional group (vPZ, X=vinyl). PS based on such fluorophores and PVT matrix can be prepared as bulk samples, micrometer size beads or cladding on optical fibers. Application of fluorophores with vinyl functional groups enabled their enhanced interaction with the matrix due to covalent bonding between the components. We demonstrate high performance of PZ−X fluorophores and especially vPZ fluorophore in fabrication of nanocomposites for detection of various types of radiation. Scintillators have enhanced gamma ray detection capabilities with an addition of triphenyl Bi, or Gd2O3 nanoparticles. High fluorescence quantum yield and luminosity of PZ fluorophores allows dramatical reduction of their content in PS systems. Mechanisms of energy transfer and conversion during scintillation process are discussed. Special consideration is given to enhancement of α/β and neutron/gamma (n/γ) pulse shape discrimination (PSD) function of the developed scintillators. [ABSTRACT FROM AUTHOR]

Frictional characteristics of several types of boundary lubricants were tested using scanning probe microscopy (SPM). These include Langmuir monolayers of stearic acids (STA), their cadmium salts (STCd), self-assembling monolayers (SAMs) of alkylchlorsilanes, and complexes of STA with rigid naphthoylene benzimidazole (x-NBI) fragments. We observed that a Langmuir monolayer deposited on a silicon surface had a very low friction coefficient against a silicon nitride tip (about 0.01-0.05) but also low mechanical stability. SAMs were found to be much more stable but had the drawback of growth in the friction coefficient at high sliding velocities. Composite NBI/STA monolayers were much more stable and were not damaged by the highest normal load applied. The frictional behavior of different monolayers was analyzed in relation to their structural organization (the type of tethering to the surface and packing density). We introduced a figure of merit (FOM) parameter which allowed comparison of frictional properties of very different lubricant materials to those of the supporting substrate. For Langmuir monolayers the FOM increased strongly with surface packing density whereas for SAMs and x-NBI/STA complexes it possessed a maximum at surface densities in the range 3.5-4.5 molecules per [nm.sup.2]. Because of the possibility of tailoring the surface packing density of aliphatic tails in the complexes, they are a promising alternative to both LB films and SAMs. For such composite monolayers, the surface packing density can be optimized to give a desired frictional behavior.

Abstract: Combining extraction and scintillation properties within the same material is a relatively new approach in development of sensors for detection of radioactive elements. Structural organization of such materials at a nanoscale typically offers higher efficiency of detection and shorter response time. In this contribution, several new protocols are discussed for fabrication of stable extractive scintillating systems based on commercial Superlig 620 (SL) material with high affinity to radiostrontium. Application of hybrid organic–inorganic beads with SL particles used as core and halloysite clay nanotubes (HNT) modified with a polyvinyltoluene (PVT) brush as a permeable shell combines high‐performance extracting properties of the SL material with efficient light emission properties of the polymer scintillator. The developed SL–HNT–PVT hybrid extractive scintillating material allows real‐time detection of low‐level concentrations of radiostrontium in water. Moreover, the suggested approach is not limited to detection of Sr but can find broader application in development of chemical, biological, or radioluminescent sensors and multifunctional materials. [ABSTRACT FROM AUTHOR]

We report significant improvements in the structure and electronic properties of a poly(3-alkylthiophene) representative, namely poly(3-methylthiophene) (P3MT), when it is synthesized in the presence of submicron electroactive poly(vinylidene fluoride) (PVDF) particles. The applied template oxidative synthesis leads to the formation of the PVDF/P3MT composite consisting of core–shell particles. The shells are constituted with a monolayer of 20–40 nm nanoparticles of the doped P3MT (P3MT-Cl) precipitated at the surface of the spherical PVDF cores. This morphology differs strongly from the hierarchical one of the neat P3MT synthesized without PVDF particles. In the latter case, 20–60 nm P3MT nanoparticles form ∼200 nm aggregates, which, in turn, are arranged in a few micrometer agglomerates. Furthermore, we demonstrate that compared to the neat polymer, doped P3MT in the shells of the composite is characterized with higher effective conjugation length, regioregularity of the molecular structure, improved intrachain packing order and lower bipolaron/polaron ratio. These features of the PVDF/P3MT composite strongly suggest applicability of this material in various electronic devices. As a proof of concept, we report on an improved sensing performance of the PVDF/P3MT-Cl composite compared with the neat P3MT-Cl in detection of several volatile organic compounds known as markers for some diseases and toxic substances. We have discovered that the maximal improvement in the sensor response magnitude corresponds to the case when the values of the analyte electronegativity and polythiophene work function are close. We associate this behavior with a higher surface dipole component of the work function of the PVDF/P3MT-Cl composite compared to that of the neat conducting polymer. [ABSTRACT FROM AUTHOR]

The synthesis, chemical characterization and optical properties of 2-(1-naphthyl)-4-vinyl-5-phenyloxazole (vNPO) and 2-(1-naphthyl)-4-allyl-5-phenyloxazole (allylNPO) monomers are reported. Starting with the organic fluor 2-(1-naphthyl)-5-phenyloxazole (αNPO), the vNPO and allylNPO monomers were synthesized using Stille coupling followed by purification. The final products were obtained with yields of ∼95% and ∼55% for vNPO and allylNPO. The absorption/emission spectra of αNPO, vNPO and allylNPO revealed that vNPO has the largest red-shifted in emission with an average wavelength of ∼420 nm, which is an advantage for increasing photomultiplier tube sensitivity without the need to add a wavelength shifter. Stable scintillating resin beads were prepared through copolymerization of the newly synthesized fluor monomers with styrene or 4-methylstyrene and divinylbenzene in the presence of toluene porogen. The resin beads were chemically stable and retained the ability to scintillate efficiently after energy deposition of beta particles from 99Tc. This result indicates efficient energy transfer occurs from the base polymer to the covalently attached fluors with subsequent fluorescence in the presence of ionizing radiation. [ABSTRACT FROM AUTHOR]

We studied peculiarities of the structural reconstruction within holographically recorded gratings on the surface of several different amorphous azobenzene-containing polymers. Under illumination with a light interference pattern, two processes take place in this type of polymer. The first process is the light-induced orientation of azobenzene units perpendicular to the polarization plane of the incident light. The second one is a transfer of macromolecules along the grating vector (i.e. perpendicular to the grating lines). These two processes result in the creation of a volume orientation grating (alternating regions of different direction or degree of molecular orientation) and a surface relief grating (SRG)—i.e. modulation of film thickness. One can assume that both orientation of molecules and their movement might change the local mechanical properties of the material. Therefore, formation of the SRG is expected to result also in modulation of the local stiffness of the polymer film. To reveal and investigate these stiffness changes within the grating, spin-coated polymer films were prepared and the gratings were recorded on them in two different ways: with an orthogonal circular or orthogonal linear polarization of two recording light beams. A combination of atomic force microscopy (AFM) and ultrasonic force microscopy (UFM) techniques was applied for SRG development monitoring. We demonstrate that formation of the phase gratings depends on the chemical structure of polymers being used, polymer film thickness, and recording parameters, with the height of grating structures (depth of modulation) increasing with both the exposure time and the film thickness. UFM images suggest that the slopes of the topographic peaks in the phase gratings exhibit an increased stiffness with respect to the grating depressions. [ABSTRACT FROM AUTHOR]