Organic Plastic Research Articles

Mechanism of plasmon-mediated enhancement of photovoltaic efficiency

Metallic nanospheres (Au, Ag, Cu) deposited on a photovoltaic (PV)-active semiconductor surface can act as light converters, collecting energy of incident photons in plasmon oscillations. This energy can be next transferred to a semiconductor substrate via a near-field channel, in a more efficient manner in comparison with the direct photo-effect. We explain this enhancement by inclusion of indirect interband transitions in a semiconductor layer due to the near-field coupling with plasmon radiation in nanoscale of the metallic components, where the momentum is not conserved as the system is not translationally invariant. The model of the nanosphere plasmons is developed (random phase approximation, analytical version, adjusted to description of large metallic clusters, with a radius of 10–60 nm) including surface and volume modes. Damping of plasmons is analysed via Lorentz friction, and irradiation losses in the far- and near-field regimes. Resulting resonance shifts are verified experimentally for Au and Ag colloidal water solutions with respect to particle size. Probability of the electron interband transition (within the Fermi golden rule) in the substrate semiconductor induced by coupling to plasmons in the near-field regime turns out to be significantly larger than for coupling of electrons to planar-wave photons. This is of practical importance for enhancement of thin-film solar cell efficiency, both for semiconductor type (such as III–V semiconductor based cells) and for conjugate-polymer-based or dye organic plastic cells, intensively developed at present. We have described also a non-dissipative collective mode of surface plasmons in a chain of near-field-coupled metallic nanospheres, for particular size, separation parameters and wavelengths. This would find an application in sub-diffraction electro-photonic circuit arrangement and for possible energy transport in solar cells, in particular in organic materials with low mobility of carriers.

Organic ionic plastic crystal electrolytes; a new class of electrolyte for high efficiency solid state dye-sensitized solar cells

Dye-sensitized solar cells are an increasingly promising alternative to conventional silicon solar cells as a method of converting solar energy to electricity and thus providing an effectively inexhaustible energy source. However, the most efficient of these devices currently utilize liquid electrolytes, which suffer from the associated problems of leakage and evaporation. Hence, significant research is currently focused on the development of solid state alternatives. Here we report a new class of solid state electrolyte for these devices, organic ionic plastic crystal electrolytes, that allow relatively rapid diffusion of the redox couple through the matrix, which is critical to the cell performance. A range of different organic ionic plastic crystal materials, utilizing different cation and anion structures, have been investigated and the conductivities, diffusion rates and photovoltaic performance of the electrolytes are reported. The best material, utilizing the dicyanamide anion, achieves efficiencies of more than 5%.

1,2-Bis[N-(N′-alkylimidazolium)]ethane salts: a new class of organic ionic plastic crystals

A new class of organic ionic plastic crystals was discovered. A series of alkylene 1,2-bis[N-(N′-alkylimidazolium)] salts with Br− and PF6− anions was prepared and most of the ethylene (C2) linked compounds undergo multiple solid–solid phase transitions as determined by differential scanning calorimetry (DSC). The salts with longer spacers (C3 or C4) between the imidazolium units do not display any solid–solid transitions. The PF6− salts with terminal C10 and C12n-alkyl moieties are “classical” organic ionic plastic crystals by Timmermans' definition; they have low ΔSf (11 J K−1 mol−1 for C10 and 12 J K−1 mol−1 for C12). Additionally, the C2 linked bis-imidazolium salts with n-butyl, n-hexyl, n-heptyl and n-octyl termini all undergo two, three or four solid state transitions and exhibit ΔSf values in the range of 36–49 J K−1 mol−1, which are similar to those of other known ionic plastic crystalline materials. These materials were additionally characterized via ionic conductivity and solid state NMR. These ionic plastic crystals are presumably single-ion conductors, but the ionic conductivities appear to be too low for practical applications. The activation energy for conduction decreases as these compounds are heated through each solid–solid transition. The lack of any change in solid state 2H NMR spectra with temperature indicates that there is no change in phenyl ring flipping, suggesting no change in the imidazolium local environment. A resolution of this apparent dichotomy is perhaps that the counterions reside with the ethylene spacers between imidazolium moieties.

An organic ionic plastic crystal electrolyte based on the triflate anion exhibiting high proton transport

A novel organic ionic plastic crystal (OIPC) electrolyte based on a quaternary ammonium cation and the triflate anion has been synthesized, which shows fast proton transport and high thermal stability in the solid state when doped with triflic acid.

Ionic liquids and organic ionic plastic crystals utilizing small phosphonium cations

The development of new liquid and solid state electrolytes is paramount for the advancement of electrochemical devices such as lithium batteries and solar cells. Ionic liquids have shown great promise in both these applications. Here we demonstrate the use of phosphonium cations with small alkyl chain substituents, in combination with a range of different anions, to produce a variety of new halide free ionic liquids that are fluid, conductive and with sufficient thermal stability for a range of electrochemical applications. Walden plot analysis of the new phosphonium ionic liquids shows that these can be classed as “good” ionic liquids, with low degrees of ion pairing and/or aggregation, and the lithium deposition and stripping from one of these ionic liquids has been demonstrated. Furthermore, for the first time phosphonium cations have been used to form a range of organic ionic plastic crystals. These materials can show significant ionic conductivity in the solid state and thus are of great interest as potential solid-state electrolyte materials.

Novel ionic liquids and plastic crystals utilizing the cyanate anion

In line with the continuing growth in the use of ionic liquids, and an ever-present requirement for high conductivity electrolytes for a range of electrochemical devices, there is a strong demand for the development of novel salts with the required physical properties. Thus, in this work a series of new cyanate-based ionic liquids and organic ionic plastic crystals have been synthesized and their physical properties are reported. Some of the salts form organic ionic plastic crystals with high ionic conductivity, indicating their potential use as solid state electrolytes. It is also shown that the ionic liquids have potential applications in the extraction of transition metal ions or the dissolution of metallic gold.

A crosslinked “polymer–gel” rechargeable lithium-ion battery electrolyte from free radical polymerization using nonionic plastic crystalline electrolyte medium

A cross-linked polymer–gel soft matter electrolyte with superior electrochemical, thermal and mechanical properties obtained from free radical polymerization of vinyl monomers in a semi-solid organic nonionic plastic crystalline electrolyte for application in rechargeable lithium-ion batteries is discussed here.

Lithium doped N,N-dimethyl pyrrolidinium tetrafluoroborate organic ionic plastic crystal electrolytes for solid state lithium batteries

The organic ionic plastic crystal material N,N-dimethyl pyrrolidinium tetrafluoroborate ([C1mpyr][BF4]) has been mixed with LiBF4 from 0 to 8 wt% and shown to exhibit enhanced ionic conductivity, especially in the higher temperature plastic crystal phases (phases II and I). The materials retain their solid state well above 100 °C with the melt not being observed up to 300 °C. Interestingly the conductivity enhancement is highest with the lowest level of LiBF4 addition in phase II, but then the order of enhancement is reversed in phase I. In all cases, a conductivity drop is observed at the II → I phase transition (105 °C) which is associated with increased order in the pure matrix, as previously reported, although the conductivity drop is least for the highest LiBF4 amount (8 wt%). The 8 wt% sample displays different conductivity behaviours compared to the lower LiBF4 concentrations, with a sharp increase above 50 °C, which is apparently not related to the formation of an amorphous phase, based on XRD data up to 120 °C. Symmetric cells, Li/OIPC/Li, were prepared and cycled at 50 °C and showed evidence of significant preconditioning with continued cycling, leading to a lower over-potential and a concomitant decrease in the cell resistivity as measured by EIS. An SEM investigation of the Li/OIPC interfaces before and after cycling suggested significant grain refinement was responsible for the decrease in cell resistance upon cycling, possibly as a result of an increased grain boundary phase.

The influence of different nanoparticles on a range of organic ionic plastic crystals

The addition of nanoparticles to an organic ionic plastic crystal can result in orders of magnitude increases in ionic conductivity, which makes these materials of interest as solid state electrolytes. However, this effect is not universal and depends on both the nature of the organic ionic plastic crystal and on the type of nanoparticle used. The effect of addition of TiO 2, Al 2O 3 and SiO 2 nanoparticles to a range of ionic materials with varying plasticity and rotator phase behaviour has been studied by thermal analysis and conductivity and the effect on the different materials is compared.

SSPM based radiation sensing: Preliminary laboratory and clinical results

Abstract Recent Solid State Photomultiplier (SSPM) technology has matured, reaching a performance level that is suitable for replacement of the ubiquitous photomultiplier tube in selected applications for environmental radiation monitoring, clinical dosimetry, and medical imaging purposes. The objective of this work is low signal level laboratory and high signal level clinical testing of the Hamamatsu MPPC (S10362-11-050C), Photonique SSPM (0810G1), and Voxtel SiPM (SQBF-EKAA/SQBF-EIOA) SSPMs coupled to different inorganic scintillator crystals (Prelude 420, BGO), inorganic doped glass scintillator material SiO2:Cu2+ and organic BCF-12 plastic scintillating fibers, used as detector elements. Plastic Optical Fibers (POFs) and Glass Optical Fibers (GOFs) are used as signal conduits for laboratory and clinical testing. Further, reduction of electron-beam-generated Cerenkov light in optical fibers is facilitated by the inclusion of metalized air-core capillary tubing between the BCF-12 plastic scintillating fiber and the POF. In a clinical setting dose linearity, percent depth dose, and angular measurements for 6 MV/18 MV photon beams and 9 MeV electron beams are compared with and without the use of the air-core capillary tubing for BCF-12 plastic scintillating fiber. These same measurements are repeated for SiO2:Cu2+ scintillator material without air-core capillary tubing.

Organic ionic plastic crystals: recent advances

Investigations into the synthesis and utilisation of organic ionic plastic crystals have made significant progress in recent years, driven by a continued need for high conductivity solid state electrolytes for a range of electrochemical devices. There are a number of different aspects to research in this area; fundamental studies, utilising a wide range of analytical techniques, of both pure and doped plastic crystals, and the development of plastic crystal-based materials as electrolytes in, for example, lithium ion batteries. Progress in these areas is highlighted and the development of new organic ionic plastic crystals, including a new class of proton conductors, is discussed.

Lithium-functionalised silicananoparticles for enhanced ionic conductivity in an organic ionic plastic crystal

Addition of silica nanoparticles functionalised with lithium propane sulfonate to the organic ionic plastic crystal N-ethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide ([C2mpyr][NTf2]) results in a significant increase in ionic conductivity. Analysis of these nanocomposites by impedance spectroscopy, NMR, positron annihilation lifetime spectroscopy (PALS) and Raman spectroscopy suggests that this is the result of higher matrix mobility due to an increase in defect size and concentration. The effect of these functionalised nanoparticles is compared to that previously observed for unfunctionalised nanoparticles in the lithium-doped and pure plastic crystal.

Unusual phase behaviour of the organic ionic plastic crystal N,N-dimethylpyrrolidinium tetrafluoroborate

Analysis of N,N-dimethylpyrrolidinium tetrafluoroborate by (1)H and (11)B NMR, Raman spectroscopy and powder XRD shows that this organic ionic plastic crystal material exhibits unusual phase behaviour. (1)H NMR analysis indicates that the mobility of the pyrrolidinium cation decreases when the material is heated into phase I, while the X-ray diffraction pattern changes from a simple, one peak structure in phase II to a more complex pattern in phase I. The possible origins of these unusual transitions are discussed.

Sustainable Solutions for Municipal Solid Waste Management in Thailand

General as well as the MSW management in Thailand is reviewed in this paper. Topics include the MSW generation, sources, composition, and trends. The review, then, moves to sustainable solutions for MSW management, sustainable alternative approaches with an emphasis on an integrated MSW management. Information of waste in Thailand is also given at the beginning of this paper for better understanding of later contents. It is clear that no one single method of MSW disposal can deal with all materials in an environmentally sustainable way. As such, a suitable approach in MSW management should be an integrated approach that could deliver both environmental and economic sustainability. With increasing environmental concerns, the integrated MSW management system has a potential to maximize the useable waste materials as well as produce energy as a by-product. In Thailand, the compositions of waste (86%) are mainly organic waste, paper, plastic, glass, and metal. As a result, the waste in Thailand is suitable for an integrated MSW management. Currently, the Thai national waste management policy starts to encourage the local administrations to gather into clusters to establish central MSW disposal facilities with suitable technologies and reducing the disposal cost based on the amount of MSW generated.

The influence of the structures and compounds of DLC coatings on the barrier properties of PET bottles

To reduce the oxygen transmission rate through a polyethylene terephthalate (PET) bottle (an organic plastic) diamond-like carbon (DLC) coatings on the inner surface of the PET bottle were deposited by radio frequency plasma-enhanced chemical vapour deposition (RF-PECVD) technology with C2H2 as the source of carbon and Ar as the diluted gas. As the barrier layer to humidity and gas permeation, this paper analyses the DLC film structure, composition, morphology and barrier properties by Fourier transform infrared, atomic force microscopy, scanning electron microscopy and oxygen transmission rate in detail. From the spectrum, it is found that the DLC film mainly consists of sp3 bonds. The barrier property of the films is significantly relevant to the sp3 bond concentration in the coating, the film thickness and morphology. Additionally, it is found that DLC film deposited in an inductively coupled plasma enhanced capacitively coupled plasma source shows a compact, homogeneous and crack-free surface, which is beneficial for a good gas barrier property in PET bottles.

An organic dye in a polymer matrix – A search for a scintillator with long luminescent lifetime

Abstract Fiber-coupled organic plastic scintillators enable dose rate monitoring in conjunction with pulsed radiation sources like linear medical accelerators. The accelerator, however, generates a significant amount of stray ionizing radiation. This radiation excites the long optical fiber cable (15–20 m), connecting the scintillator with the optical detector circuit, causing parasitic luminescence in the optical fiber. In this paper we propose a method for circumventing this problem. The method is based on the use of an organic scintillator with a long luminescent lifetime (room temperature phosphorescence). The long lifetime of the scintillator signal facilitates a temporal gating of the dose rate signal with respect to the parasitic luminescence from the optical fiber.

Investigation of linear accelerator pulse delivery using fast organic scintillator measurements

Fiber-coupled organic plastic scintillators present an attractive method for time-resolved dose measurements during radiotherapy. Most organic scintillators exhibit a fast response, making it possible to use them to measure individual high-energy X-ray pulses from a medical linear accelerator. This can be used in complex treatment procedures such as gated intensity-modulated radiotherapy (IMRT) 1 1 Abbrevations: Intensity-modulated radiotherapy (IMRT), linear accelerator (linac), radioluminescence (RL), photomultiplier tube (PMT), monitor unit (MU), source-to-surface distance (SSD). , where the advantage of dose rate measurements of high temporal resolution is highly emphasized. We report on development of a fast data acquisition scintillator-based system as well as measurements performed on Varian medical linear accelerators, delivering 6 MV X-ray beams. The dose delivery per radiation pulse was found to agree with expectations within roughly 1%, although minor discrepancies and transients were evident in the measurements.

Terbium β‐Diketonate Based Highly Luminescent Soft Materials

Abstract[C4mim][Tb(hfacac)4] (1) and [C4mpyr][Tb(hfacac)4] (2) (C4mim = 1‐butyl‐3‐methylimidazolium, C4mpyr = N‐butyl‐N‐methylpyrrolidinium) were obtained by reacting [C4mim]Cl (for 1) or [C4mpyr]Br (for 2) with (hexafluoroacetyl)acetone and terbium(III) chloride in a basic ethanol/water solution. Single‐crystal X‐ray structure analysis reveals TbIII to be chelated by four (hexafluoroacetyl)acetonate anions. Differential scanning calorimeter (DSC) investigations show both compounds to melt below 120 °C. For [C4mpyr][Tb(hfacac)4] (2) the DSC traces indicate an organic plastic crystal behavior (OPCB). Both compounds show very strong emission in the visible region of light which are characteristic for the terbium(III) ion.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Hydrophilic Dots on Hydrophobic Nanopatterned Surfaces as a Flexible Gas Barrier

The present study demonstrates a transparent polymeric gas barrier film mimicking the Namib Desert beetle's back. SiO(2) hydrophilic dots have been deposited on a nanopatterned hydrophobic surface. A nanopatterned surface was fabricated by UV-curable nanoimprinting techniques. The surface energies of the hydrophobic and hydrophilic domains were 7.29 and >73.12 mN/m, respectively. The characteristics of water vapor transfer from hydrophobic to hydrophilic regions due to difference of the attractive force at interfaces are shown to yield the enhanced barrier performance according to the Ca degradation measurements. This strategy is suitable for organic electronics, solar cells, and plastic optics applications requiring moisture-free properties with high transmission.

Internal calibration of gel dosimeters: A feasibility study

In this work we test the feasibility of a new calibration method for gel dosimetry. We examine, through Monte Carlo modelling, whether the inclusion of an organic plastic scintillator system at key points within the gel phantom would perturb the dose map. Such a system would remove the requirement for a separate calibration gel, removing many sources of uncertainty.