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Dielectric properties of any particular material will determine the level of microwave (MW) heating. Therefore, measurement of the dielectric properties of MW treatment subject materials is necessary. This study investigated the dielectric properties of six roughages and three concentrate animal feeds across the microwave frequency range of 1 × 109 to 5 × 109 Hz. Six treatment groups, named control (at equilibrium moisture constant), oven dried (0% moisture), 25% moisture added, 50% moisture added, 75% moisture added, and 100% moisture added groups were prepared for the study. Three separate replications and five observations for each replication were used to assess the dielectric properties of these materials. The results showed that for increasing moisture content, from oven-dried, though the control status, to 100% added moisture, both the dielectric constant (real part) and the dielectric loss factor (imaginary part) increased for both the roughages and concentrates. However, the responses were not linear. The oven-dried plant samples' dielectric properties were very low compared with those of the higher moisture content samples. Thus, the sample's moisture content was the dominant contributor to the feed samples' dielectric behavior. Among all the feed samples, faba bean and wheat grain showed the highest response to added moisture. Mathematical models were developed to explain the dielectric properties of feeds as a function of frequency and moisture content. The goodness of fit (r2) for these models' real part varied between 0.85–0.99 for roughage and 0.98–0.99 for concentrate feed type. On the other hand, the goodness of fit for the imaginary part varied between 0.59–0.78 for roughage, and 0.81–0.93 for concentrate feeds.

Graphene and its derivatives have acquired substantial research attention in recent years because of their wide range of potential applications. Implementing sustainable technologies for fabricating these functional nanomaterials is becoming increasingly apparent, and therefore, a wide spectrum of naturally derived precursors has been identified and reformed through various established techniques for the purpose. Nevertheless, most of these methods could only be considered partially sustainable because of their complexity as well as high energy, time, and resource requirements. Here, we report the fabrication of carbon nano-onion-interspersed vertically oriented multilayer graphene nanosheets through a single-step, environmentally benign radio frequency plasma-enhanced chemical vapor deposition process from a low-cost carbon feedstock, the oil from the peel of Citrus sinensis orange fruits. C. sinensis essential oil is a volatile aroma liquid principally composed of nonsynthetic hydrocarbon limonene. Transmission electron microscopy studies on the structure unveiled the presence of hollow quasi-spherical carbon nano-onion-like structures incorporated within graphene layers. The as-fabricated nano-onion-incorporated graphene films exhibited a highly hydrophobic nature showing a water contact angle of up to 129(0). The surface energies of these films were in the range of 41 to 35 mJ.m(-2). Moreover, a chemiresistive sensor directly fabricated using C. sinensis-derived onion-structured graphene showed a p-type semiconductor nature and a promising response to acetone at room temperature. With its unique morphology, surface properties, and electrical characteristics, this material is expected to be useful for a wide range of applications.

Tunability and fine control of structure and morphology in the patterns of vertically-oriented graphenes is of high importance for their efficient functionalization and application. In this work, we present an experimental and simulation insight into the formation of graphene structures. Detailed simulations by an ad hoc model based on a large number of interacting elemental processes were implemented to ensure a deeper insight into the processes which cannot be directly measured and assessed in the experiments, such as relative densities of adsorbed species and density of ion current at the nanostructures. The combination of the experimental and simulation approaches provided a new level of understanding of the processes that govern formation of the graphene network morphology. Moreover, the potential of novel analytical techniques such as Hough transformations, fractal dimension distributions and Minkovski connectivity, 2D FFT transforms, Hough transformation spectra and others for analysis of the graphene array morphology was successfully demonstrated. The evolution of surface morphology of graphene derived from cold-pressed Citrus sinensis oil, a by-product of orange juice production by centrifugation, synthesised via a catalyst‒free process, was investigated using experimental analyses, Raman spectroscopy, scanning electron microscopy and X‒ray photoelectron spectroscopy, and numerous advanced analytical techniques such as distributions of fractal dimensions. National Research Foundation (NRF) This work was supported in part by the following funds and organizations: framework of the PEGASUS (Plasma Enabled and Graphene Allowed Synthesis of Unique nano-Structures) project, funded by the European Union’s Horizon research and innovation programme under grant agreement No. 766894; OSTIn-SRP/EDB, National Research Foundation, and AcRF (Rp6/16 Xs) Singapore; I. L. acknowledges support from the School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology. K.B. acknowledges support from the Australian Research Council.

Antifouling/antibacterial coating derived from a sustainable natural resource for biomedical devices have shown promising outcomes, especially in the prevention of bacterial growth. Herein, pulse-plasma chemical vapour deposition is used to fabricate antimicrobial coatings from Terpinen-4-ol, a tea tree oil-based precursor. In this manuscript, during RF plasma polymerisation, pulsed plasma is used to retain the pristine monomer structure in the developed stable coating and thereby enhance its antibacterial activity. The developed films have tunable physical and chemical properties. Diverse film surface properties were obtained by varying the plasma deposition parameters, mainly the deposition mode (pulse and continuous wave) and duty cycle. The role of film wettability on degree of bacterial attachment has been elucidated. Overall, the number of viable bacteria on all the deposited coatings (25–30%) were reduced to half with respect to the control (56%).

This paper explains carrier based PWM controlled single-phase to six-phase (1x6) Indirect Matrix Converter (IMC) to drive a six-phase Induction motor. Like six-phase inverter, six-phase matrix converter also able to develop the output voltages and currents shifted by 60°. The 1x6 IMC consist of a front end side current source rectifier (CSR) followed by voltage source inverter (VSI) without any energy storage element or any DC link capacitor, so that the total power to weight ratio of the whole converter get reduced. The front end side CSR is a three leg rectifier supplied with single-phase source through a filter inductor and two filter capacitors. A six-phase Induction motor is directly connected with conventional two level six-phase VSI. The 1x6 IMC control scheme is studied, analyzed and validate in MATLAB simulation software.

Two novel types of anion exchange membranes (AEMs) having imidazolium-type functionalised nanofibrous substrates were prepared using the facile and potentially scalable method. The membranes’ precursors were prepared by graft copolymerization of vinylbenzyl chloride (VBC) onto syndiotactic polypropylene (syn-PP) and polyamide-66 (PA-66) nanofibrous networks followed by crosslinking with 1,8-octanediamine, thermal treatment and subsequent functionalisation of imidazolium groups. The obtained membranes displayed an ion exchange capacity (IEC) close to 1.9 mmol g–1 and ionic (OH-) conductivity as high as 130 mS cm–1 at 80 °C. This was coupled with a reasonable alkaline stability representing more than 70% of their original conductivity under accelerated degradation test in 1 M KOH at 80 °C for 360 h. The effect of ionomer binder on the performance of the membrane electrode assembly (MEA) in AEM fuel cell was evaluated with the optimum membrane. The MEA showed a power density of as high as 440 mW cm−2 at a current density is 910 mA cm−2 with diamine crosslinked quaternized polysulfone (DAPSF) binder at 80 °C with 90% humidified H2 and O2 gases. Such performance was 2.3 folds higher than the corresponding MEA performance with quaternary ammonium polysulfone (QAPS) binder at the same operating conditions. Overall, the newly developed membrane was found to possess not only an excellent combination of physico-chemical properties and a reasonable stability but also to have a facile preparation procedure and cheap ingredients making it a promising candidate for application in AEM fuel cell.

In this present work, waste engine oil was explored as a precursor for the synthesis of carbon dots (CDs) by hydrothermal route for the first time. The obtained CDs showed excellent water solubility, photostability, bright blue emission under UV light (wavelength 365 nm), pH stability, high quantum yield, and greater biocompatibility. It was thoroughly studied by vital characterization techniques such as HR-TEM, UV–Visible spectroscopy, FTIR, SEM, PSA, Fluorescence spectroscopy with lifetime analysis. The fluorescence of synthesized CDs was quenched by the addition of Fe3+ as it showed excellent selectivity and sensitivity towards Fe3+. The sensing probe showed a good linear response (R2 = 0.9986) with a limit of detection 0.055 μM in the linear range of 0.6–3.3 μM. Due to excellent fluorescence properties of CDs, it have been applied as fluorescent ink for information storage. In addition, CDs coated polymer matrix was made and used for bead-based detection of Fe3+. Finally, the presented system could be considered as an efficient probe for Fe3+ detection and paved a way for efficient utilization of waste into value-added products.

Surface modification of thin films is often performed to enhance their properties. In this work, in situ modification of Terpinen-4-ol (T4) plasma polymer is carried out via simultaneous surface functionalization and nanoparticle immobilization. Terpinen-4-ol plasma polymers surface were decorated with a layer of ZnO nanoparticles in an oxygen plasma environment immediately after polymer deposition. A combination of hydrophilic modification and ZnO nanoparticle functionalization of the T4 polymer surface led to an enhancement in antibacterial properties by factor of 3 (from 0.75 to 0.25 CFU.mm&minus, 2). In addition, ZnO nanoparticle-modified coatings demonstrated improved UV absorbing characteristics in the region of 300&ndash, 400 nm by 60% relative to unmodified coatings. The ZnO modified coatings were transparent in the visible region of 400&ndash, 700 nm. The finding points towards the potential use of ZnO nanoparticle-modified T4 plasma polymers as optically transparent UV absorbing coatings.

Sustainable marine antifouling strategies aim to minimize long term environmental impacts while effectively preventing surface colonization. In this study, we report upon a biodegradable antifouling coating for marine applications. In two stages, thin bilayers were produced using plasma-enhanced chemical vapor deposition of terpinen-4-ol, at applied powers of 100 W initially and then 10 or 25 W. The resulting coatings were characterized for solubility, surface energy, surface roughness and optical transmission. Both coatings exhibited similar solubility over the initial 14 days of observation, though structures deposited at 25 W were significantly more stable after 14 days. Coatings were smoother than the control surface upon which they were deposited and had higher hydrophobicity with transmission efficiencies >90% (400–1000 nm). Field assessments of the samples were carried out in Curralea Lake (Townsville, Australia) to assess their real world performance. Results indicate that the environmentally friendly coatings, terpinen-4-ol plasma polymer influenced antifouling. The proposed mechanism for this effect is the dissolution of the coating coupled with possible antimicrobial properties of the terpinen-4-ol. These results point to the potential usefulness of developing multilayer coatings for extended deployments.

Dielectric properties are essential for application in: thermal processes using microwave and radio frequency; predicting heat uniformity in dielectric heating; and developing moisture measurement equipment based on electromagnetic waves. While the dielectric properties of many agricultural legumes have been studied, their response as a function of moisture content and temperature at microwave frequencies has not been well explored. In this study, dielectric properties of Kabuli chickpea, green and red lentils were measured, using an open-ended coaxial probe, at four moisture contents between 8% and 20% wet base (wb), temperatures up to 80 °C and in the microwave frequency range of 700–7000 MHz, which includes three allowed frequencies of 915, 2450, 5800 in the Industrial, Scientific and Medical microwave range. According to the results, at frequencies above 3000 MHz, there is a negative linear relation between loss factor and frequency and the linearity was more at higher moisture contents. Due to the linear correlation of the complex-plane plot, legumes’ densities could be predicted from their dielectric properties at 1800 MHz. At 2450 MHz, penetration depths at room temperature are below 5 and 15 cm for chickpea kernels and powdered lentils, respectively. Therefore, chickpeas need to be treated in one layer during microwave processing for more heat uniformity.

The present study describes an environmentally friendly approach to fabricate hydrocarbon-rich polymer thin films from a bio-renewable precursor, orange oil, cold extracted from orange peels using radio frequency plasma polymerization. The polymer thin films fabricated at different RF power level (10–75 W) were characterized with variable angle spectroscopic ellipsometry, UV–visible spectroscopy, Fourier transform infrared spectroscopy and atomic force microscopy. Optical characterization showed that independent of deposition power films exhibited good transparency (~ 90%) in the visible region and a refractive index of 1.55 at 500 nm. The optical band gap measured around 3.60 eV and falls within the insulating region. The atomic force microscopic images revealed that the surface is pinhole-free in nature and smooth at nanoscale, with average surface roughness dependent on the deposition power. Film hardness increased from 0.50 to 0.78 GPa as applied power increased from 10 to 75 W.

Microwave assisted pyrolysis (MWAP) is an alternative heating approach to convert biosolids into value-added products, such as biochar, biogas and bio-oil. Studying the dielectric properties of biosolids is fundamental to understand the behaviour of this material under microwave irradiation and to design microwave assisted pyrolysis systems. This study examined the dielectric properties of biosolids with changes in moisture content and applied microwave frequency. Results demonstrated that the dielectric constant decreases with decreasing moisture content and with increasing microwave frequency, but the dielectric loss factor of dry biosolids is almost zero. Simulations demonstrated that moisture content of biosolids impacts on the distribution and intensity of electromagnetic field. Because of the poor dielectric properties of dry biosolids, a microwave susceptor must be added to the biosolids to attract microwave energy so that the materials can reach temperatures required for pyrolysis. Therefore, this study also investigated the impact of four microwave susceptors (activated carbon, charcoal, biochar and glycerol) on biosolids pyrolysis and on biochar properties produced from biosolids via microwave assisted pyrolysis at 600 °C. The choice of microwave susceptor influences the heating rate of biosolids and the specific surface area of the resultant biochar. Results show that activated carbon favours the heating process, increases surface area, and the biochar produced with activated carbon has the highest carbon stability and energy value.

Plasma polymers such as polyterpenol have been investigated for use as biofunctional coatings, insulating/dielectric layers in electronics, and adhesion promoting interlayers in organic electronics. The commercialisation of plasma polymers in these and other biomaterial-related applications is contingent upon their ability to resist degradation in response to sterilising and potentially damaging ionising radiation, such as gamma rays. Hence, this study focusses on the stability of plasma polymerised polyterpenol thin films following exposure to gamma radiation doses ranging from 0 to 100 kGy. Irradiated films were subjected to ellipsometry, current–voltage, dielectric, Fourier transform infrared, and atomic force microscopy characterisation. Stability of polyterpenol was evidenced by the observed lack of radiation-induced variation in its complex refractive index, optical band gap, relative permittivity, dc conductivity, surface chemical functionalities, and surface morphology.

Graphene-based resistive random access memory devices is a promising non-volatile memory technology that combines low operation voltage and power, extremely fast write/erase speeds, excellent reliability and storage capacity of RRAM with low-cost, large area and flexibility of carbon-based technologies. However, low-cost single-step synthesis of high-quality graphene remains a challenge. In this paper, high quality graphene synthesized directly from sustainable carbon source (M. alternifolia oil) was used as electrode and pentacene/C60 as active layers in carbon-based RRAM. I-V measurements were used to demonstrate reproducible switching (rapid increase in current) at certain voltage which was reversible. Charge transport and accumulation was visualized using electric field induced optical second harmonic generation and charge modulation spectroscopy. Hole transport from graphene layer to the organic layer was the primary cause of the observed switching behavior.

In this report, the electrical properties of plasma polymer films functionalized with ZnO nanoparticles were investigated with respect to their potential applications in biomaterials and microelectronics fields. The nanocomposite films were produced using a single-step method that combines simultaneous plasma polymerization of renewable geranium essential oil with thermal decomposition of zinc acetylacetonate Zn(acac)2. The input power used for the deposition of composites were 10 W and 50 W, and the resulting composite structures were abbreviated as Zn/Ge 10 W and Zn/Ge 50 W, respectively. The electrical properties of pristine polymers and Zn/polymer composite films were studied in metal&ndash, insulator&ndash, metal structures. At a quantity of ZnO of around ~1%, it was found that ZnO had a small influence on the capacitance and dielectric constants of thus-fabricated films. The dielectric constant of films with smaller-sized nanoparticles exhibited the highest value, whereas, with the increase in ZnO particle size, the dielectric constant decreases. The conductivity of the composites was calculated to be in the in the range of 10&minus, 14&ndash, 10&minus, 15 &Omega, &minus, 1 m&minus, 1, significantly greater than that for the pristine polymer, the latter estimated to be in the range of 10&minus, 16&ndash, 17 &Omega, 1.

Resonator measurements allow to determine permittivity and losses of board materials with conducting strips such as microstrip. The resonant wavelength is related to the board permittivity and the resonator length. A linear regression yields the effective permittivity. To reduce the uncertainty of the linear regression, an Iterative Method is proposed. It combines the regression on measured datapoints with an additional analytical datapoint based on the electrical resonator length and results in reducing the permittivity's uncertainty by one magnitude. Measurements of composite material show, that permittivity can be modified as desired by adding graphene flakes. Also losses will be measured.

In the past several decades, processes that rely on the use of polymeric membranes have received considerable attention for the important role they play in biological and industrial fields. Surface properties are critical to membrane applications, yet a number of polymers that are both suitable for membrane manufacturing and possess necessary surface properties is often limited. Thus, modification of membrane surfaces is often used to fulfil diverse requirements. Nonequilibrium plasma treatment is an efficient method to tailor/adapt surface morphology and chemical structure of polymers without changing the bulk properties of the treated material. Plasma conditions play a significant role in controlling physico-chemical properties, and can be used to selectively modify surface energy, roughness, and biocompatibility of the polymer, as well as introduce new surface functional groups, e.g. carboxyl, hydroxyl, or amino functionalities, onto the surface of the membrane. This chapter will review the use of nonequilibrium plasma surface treatment for modification of polymeric membranes. First, the key interactions between physical and chemical effects of cold plasma and material surfaces will be briefly introduced. Then, specific examples for the usage of plasma to improve biological activities and mitigate biofouling properties of membranes will be discussed. Finally, plasma-induced grafting on membranes and plasma modification using several of the most common nonpolymerizable gases will be reviewed.

Nanocomposites offer attractive and cost-effective thin layers with superior properties for antimicrobial, drug delivery and microelectronic applications. This work reports single-step plasma-enabled synthesis of polymer/zinc nanocomposite thin films via co-deposition of renewable geranium essential oil-derived polymer and zinc nanoparticles produced by thermal decomposition of zinc acetylacetonate. The chemical composition, surfaces characteristics and antimicrobial performance of the designed nanocomposite were systematically investigated. XPS survey proved the presence of ZnO in the matrix of formed polymers at 10 W and 50 W. SEM images verified that the average size of a ZnO nanoparticle slightly increased with an increase in the power of deposition, from approximately 60 nm at 10 W to approximately 80 nm at 50 W. Confocal scanning laser microscopy images showed that viability of S. aureus and E.coli cells significantly reduced on surfaces of ZnO/polymer composites compared to pristine polymers. SEM observations further demonstrated that bacterial cells incubated on Zn/Ge 10 W and Zn/Ge 50 W had deteriorated cell walls, compared to pristine polymers and glass control. The release of ZnO nanoparticles from the composite thin films was confirmed using ICP measurements, and can be further controlled by coating the film with a thin polymeric layer. These eco-friendly nanocomposite films could be employed as encapsulation coatings to protect relevant surfaces of medical devices from microbial adhesion and colonization.

Polyoxometalate immobilized nanofiber was used to fabricate low gas permeable layer for composite membranes designed for proton exchange membrane fuel cell (PEMFC) operating at low relative humidity (RH). The composite membranes revealed enhanced proton conductivity in dry conditions compared with state-of-the-art pristine membrane (Nafion 112, N112). This was coupled with a low fuel crossover inheriting the composite membranes about 100 mV higher OCV than N112 when tested in PEMFC at 60 °C and 40% RH. A maximum power density of up to 930 mW cm−2 was also achieved which is substantially higher than the N112 under similar conditions (577 mW cm−2). Such remarkable performance enhancement along with undetectable leaching of immobilized polyoxometalate, high dimensional stability and low water uptake of the composite membranes suggest a strong potential for PEMFC under low RH operation.

Wound infections arising from bacterial contamination and colonisation are of substantial burden to healthcare. Currently, bandages are used to merely provide wounds with physical barriers to bacteria, however they quickly become saturated and ineffective. Silver containing wound dressings have gained commercial and scientific attention as a potential solution to the problem of wound infections. In this work, we compare the antibacterial efficacy of recently patented silver nanoparticle loaded plasma polymer film technology and a commercially available GranuFoam Silver® silver-coated wound dressings. The silver nanoparticle loaded foams contained lower amount of elemental silver than the commercially available wound dressings but both silver-loaded foams had comparable antibacterial capacity. Furthermore, the silver nanoparticle loaded foams had greater hydrophilicity which may be beneficial in applications. Collectively, the results demonstrate that the nanoparticle loaded plasma polymer coating can be used on medical devices such as wound dressings with similar efficacy to existing products. Refereed/Peer-reviewed

Three dimensional graphene nano-mesh (3D-GNM) has been synthesized by radio frequency plasma-enhanced chemical vapor deposition. The 3D-GNM with various shapes is obtained on nickel foam substrate without using any nano-network as a pattern mask. Moreover, non-synthetic precursor Melaleuca alternifolia oil, with environmentally-friendly properties, is used as the carbon source for synthesis of 3D-GNM. This synthesis route with low energy expenses and little environmental contamination provides a simple and cost effective fabrication of 3D-GNM for utilization in future fundamental studies related to graphene.

Radio frequency (R.F.) glow discharge polyterpenol thin films were prepared on silicon wafers and irradiated with I10+ ions to fluences of 1 × 1010 and 1 × 1012 ions/cm2. Post-irradiation characterisation of these films indicated the development of well-defined nano-scale ion entry tracks, highlighting prospective applications for ion irradiated polyterpenol thin films in a variety of membrane and nanotube-fabrication functions. Optical characterisation showed the films to be optically transparent within the visible spectrum and revealed an ability to selectively control the thin film refractive index as a function of fluence. This indicates that ion irradiation processing may be employed to produce plasma-polymer waveguides to accommodate a variety of wavelengths. XRR probing of the substrate-thin film interface revealed interfacial roughness values comparable to those obtained for the uncoated substrate's surface (i.e., both on the order of 5 A), indicating minimal substrate etching during the plasma deposition process.

Plasma processing, e.g., functionalisation and deposition of antibacterial coatings, is often used to enhance surface properties of biomaterials. Plasma is, however, a non-uniform active medium, and the result of processing depends on the nature of both the plasma and the substratum. Here we show that when an antibacterial coating (i.e., polyterpenol) is plasma polymerised onto four types of titanium substrata that differ in their micro- and nano-scale topography (but not the bulk chemistry), the distribution of functional groups, e.g., OH and C O, in the polymer across the surface differs sufficiently, and so does the antibacterial activity of the resulting material system. While the addition of a coating hinders biofilm formation by Staphylococcus aureus and Pseudomonas aeruginosa, the bactericidal effect is significantly stronger in polymers deposited onto surfaces possessing lower degrees of nanoscale roughness, e.g., substrata after mechanical and chemical polishing. The reduced antibacterial efficacy of polymers on substrata with greater surface roughness (e.g., on mechanically polished or lotus leaf-like surfaces) is attributed to a greater extent of thickness non-uniformity and heterogeneity in the functional group distribution across the surface. These findings suggest that the magnitude and distribution of topographical features of the substratum should be considered when designing plasma-enabled surface modification strategies.

Inherently volatile at atmospheric pressure and room temperature, plant-derived precursors present an interesting human-health-friendly precursor for the chemical vapour deposition of thin films. The electrical properties of films derived from Pelargonium graveolens (geranium) were investigated in metal–insulator–metal (MIM) structures. Thin polymer-like films were deposited using plasma-enhanced synthesis under various plasma input power. The J–V characteristics of thus-fabricated MIM were then studied in order to determine the direct current (DC) conduction mechanism of the plasma polymer layers. It was found that the capacitance of the plasma-deposited films decreases at low frequencies (C ≈ 10−11) and remains at a relatively constant value (C ≈ 10−10) at high frequencies. These films also have a low dielectric constant across a wide range of frequencies that decreases as the input RF power increases. The conductivity was determined to be around 10−16–10−17 Ω−1 m−1, which is typical for insulating materials. The Richardson–Schottky mechanism might dominate charge transport in the higher field region for geranium thin films.

Details of a fast and sustainable bottom-up process to grow large area high quality graphene films without the aid of any catalyst are reported in this paper. We used Melaleuca alternifolia, a volatile natural extract from tea tree plant as the precursor. The as-fabricated graphene films yielded a stable contact angle of 135°, indicating their potential application in very high hydrophobic coatings. The electronic devices formed by sandwiching pentacene between graphene and aluminum films demonstrated memristive behavior, and hence, these graphene films could find use in nonvolatile memory devices also.

The liquid phase effect of V(2)O(5) on the densification, microstructure and microwave dielectric properties of Mg(2)TiO(4) (MTO) ceramics has been investigated. The addition of V(2)O(5) significantly lowered the sintering temperature compared to pure MTO ceramics with improved microstructure, relative density and microwave dielectric properties. The increase in relative density and average grain size via growth of large grains and dissolution of small grains is explained by Ostwald ripening phenomena. Further, the microwave dielectric properties of the pure and MTO with V(2)O(5) samples were measured at cryogenic temperatures. It was observed that the loss tangent (tan ) and Q × f o of pure MTO increased with temperature, whereas the loss tangent and Q × f o of the samples with V(2)O(5) decreased with a rise in temperature. However, the MTO ceramics added with 0.5 and 1.0 wt% of V(2)O(5) manifested slightly higher loss tangents as compared to the pure MTO ceramics. The mechanism of the microwave loss is in agreement with the theory of intrinsic dielectric loss derived from the two phonon difference process. Further, the distinctive loss peak at 40 K is attributed to the orientation polarization having dispersion at the microwave frequency. The addition of V(2)O(5) did not cause any changes on the temperature stability of the MTO ceramics, whereas the temperature coefficient of the permittivity increases with an increase in temperature. The broadband dielectric measurement reveals that the V(2)O(5) doping increases the dielectric constant and enhances the stability over a wide frequency range, and shows a peak around 1.8 GHz. The tan of pure MTO still shows the peak whereas the samples doped with V(2)O(5) suppresses this peak significantly.

Bacterial colonisation of biomedical devices demands novel antibacterial coatings. Plasma-enabled treatment is an established technique for selective modification of physicochemical characteristics of the surface and deposition of polymer thin films. We investigated the retention of inherent antibacterial activity in geranium based plasma polymer thin films. Attachment and biofilm formation by Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli was significantly reduced on the surfaces of samples fabricated at 10 W radio frequency (RF) power, compared to that of control or films fabricated at higher input power. This was attributed to lower contact angle and retention of original chemical functionality in the polymer films fabricated under low input power conditions. The topography of all surfaces was uniform and smooth, with surface roughness of 0.18 and 0.69 nm for films fabricated at 10 W and 100 W, respectively. Hardness and elastic modules of films increased with input power. Independent of input power, films were optically transparent within the visible wavelength range, with the main absorption at ~290 nm and optical band gap of ~3.6 eV. These results suggest that geranium extract-derived polymers may potentially be used as antibacterial coatings for contact lenses.

Optically transparent, smooth, defect-free, chemically inert and with good adhesion to a variety of substrates, plasma polymers from plant-derived secondary metabolites have been identified as promising encapsulating materials for organic electronics and photovoltaics. Here, we demonstrate that an encapsulating layer of plasma polymerized γ-terpinene reduces degradation-related loss in conversion efficiency in PCPDTBT:PC70BM solar cells under ambient operating conditions. The stability of γ-terpinene films was then investigated under extreme UV irradiation conditions as a function of deposition power. When exposed to ambient air, prolonged exposure to UV–A and UV–B light led to notable ageing of the polymer. Photooxidation was identified as the main mechanism of degradation, confirmed by significantly slower ageing when oxygen was restricted through the use of a quartz cover. Under unnatural high-energy UV–C irradiation, significant photochemical degradation and oxidation occurred even in an oxygen-poor environment.

Owing to their amorphous, highly cross-liked nature, most plasma polymers display dielectric properties. This study investigates iodine doping as the means to tune optoelectronic properties of plasma polymer derived from a low-cost, renewable resource, i.e., Melaleuca alternifolia oil. In situ exposure of polyterpenol to vapors of electron-accepting dopant reduced the optical band gap to 1.5 eV and increased the conductivity from 5.05 × 10−8 S/cm to 1.20 × 10−6 S/cm. The increased conductivity may, in part, be attributed to the formation of charge-transfer complexes between the polymer chain and halogen, which act as a cation and anion, respectively. Higher levels of doping notably increased the refractive index, from 1.54 to 1.70 (at 500 nm), and significantly reduced the transparency of films.

Plasma polymerization (glow discharge or the cold plasma) is used for material surface processing as well as for fabrication of thin films and nanoclusters. The plasma polymerization is a simple, one-step, solvent-free technique used to fabricate materials with a broad spectrum of properties suitable for use in electronics, biomedical, and mechanical fields. The first section of this chapter briefly reviews the mechanisms of plasma polymerization, identifying key parameters that control this process. This is followed by an in-depth discussion of material characteristics, i.e., optical, electrical, chemical and structural properties, typical of plasma polymers, with select examples that focus on the use of plasma polymers as functional materials for advanced and emerging electronics and biomedical applications.

Organic electronics, such as displays, photovoltaics and electronics circuits and components, offer several advantages over the conventional inorganic-based electronics because they are inexpensive, flexible, unbreakable, optically transparent, lightweight and have low power consumption. In particular, organic displays exhibit high brightness, fast response time, wide viewing angle, and low operating voltage. [...]

Investigations on the wetting, solubility and chemical composition of plasma polymer thin films provide an insight into the feasibility of implementing these polymeric materials in organic electronics, particularly where wet solution processing is involved. In this study, thin films were prepared from 1-isopropyl-4-methyl-1,4-cyclohexadiene (γ-Terpinene) using radio frequency (RF) plasma polymerization. FTIR showed the polymers to be structurally dissimilar to the original monomer and highly cross-linked, where the loss of original functional groups and the degree of cross-linking increased with deposition power. The polymer surfaces were hydrocarbon-rich, with oxygen present in the form of O–H and C=O functional groups. The oxygen content decreased with deposition power, with films becoming more hydrophobic and, thus, less wettable. The advancing and receding contact angles were investigated, and the water advancing contact angle was found to increase from 63.14° to 73.53° for thin films prepared with an RF power of 10 W to 75 W. The wetting envelopes for the surfaces were constructed to enable the prediction of the surfaces’ wettability for other solvents. The effect of roughness on the wetting behaviour of the films was insignificant. The polymers were determined to resist solubilization in solvents commonly used in the deposition of organic semiconducting layers, including chloroform and chlorobenzene, with higher stability observed in films fabricated at higher RF power.

The microwave dielectric properties of CeO(2) nanoparticles (0.5, 1.0 & 1.5wt%) doped Mg(2)(TiO(4)(MTO) ceramics have been investigated at cryogenic temperatures. The XRD patterns of the samples were refined using the full proof program reveal the inverse spinel structure without any secondary phases. The addition of CeO(2) nanoparticles lowered the sintering temperature with enhancement in density and grain size as compared to pure MTO ceramics. This is attributed to the higher sintering velocity of the fine particles. Further, the microwave dielectric properties of the MTO ceramics were measured at cryogenic temperatures in the temperature range of 6.5-295 K. It is observed that the loss tangent (tanδ) of all the samples increased with temperature. However, the CeO(2) nanoparticles doped MTO ceramics manifested lower loss tangents as compared to the pure MTO ceramics. The loss tangents of the pure and MTO ceramics doped with 1.5 wt% of CeO(2) nanoparticles measured at 6.5K are found to be 6.6x10^-5 and 5.4x10^-5, respectively. The addition of CeO(2) nanoparticles did not cause any changes on the temperature stability of the MTO ceramics at cryogenic temperatures. On the other hand, the temperature coefficient of the permittivity increased with rise in temperature and with the wt% of CeO(2) nanoparticles. The obtained lower loss tangent values at cryogenic temperatures can be attributed to the decrease in both intrinsic and extrinsic losses in the MTO ceramics.

Low pressure radio frequency plasma-assisted deposition of 1-isopropyl-4-methyl-1,4-cyclohexadiene thin films was investigated for different polymerization conditions. Transparent, environmentally stable and flexible, these organic films are promising candidates for organic photovoltaics (OPV) and flexible electronics applications, where they can be used as encapsulating coatings and insulating interlayers. The effect of deposition RF power on optical properties of the films was limited, with all films being optically transparent, with refractive indices in a range of 1.57–1.58 at 500 nm. The optical band gap (Eg) of ~3 eV fell into the insulating Eg region, decreasing for films fabricated at higher RF power. Independent of deposition conditions, the surfaces were smooth and defect-free, with uniformly distributed morphological features and average roughness between 0.30 nm (at 10 W) and 0.21 nm (at 75 W). Films fabricated at higher deposition power displayed enhanced resistance to delamination and wear, and improved hardness, from 0.40 GPa for 10 W to 0.58 GPa for 75 W at a load of 700 μN. From an application perspective, it is therefore possible to tune the mechanical and morphological properties of these films without compromising their optical transparency or insulating property.

The measurement of dielectric properties of materials is critical to understanding the electromagnetic field distribution in the materials. Reliable knowledge of the dielectric constant is also important when designing a microwave pyrolysis unit for effective pyrolysis of materials of interest. The dielectric probe technique was used to evaluate the dielectric properties of biosolids. Biosolid samples were collected from various sources and the dielectric properties were measured across the microwave frequency range of 1.0 GHz to 10.0 GHz. The dielectric constant of the materials varied in the range from 80 to 2 and depended mainly on the origin of the sample, the electrical conductivity and the moisture content of the material. A mathematical model was developed to accurately predict the values of complex permittivity. This model was verified using the measured data.

This article presents low-temperature, one-step dry synthesis of optically transparent thermally-stable, biocompatible cis−β−ocimene-based thin films for applications as interlayer dielectric and encapsulating layer for flexible electronic devices, e.g. OLEDs. Morphological analysis of thin films shows uniform, very smooth (Rq

Low permeability layers of poly(1-vinylimidazole) were polymerised and deposited onto both sides of electrospun polyethersulfone (PES) nanofibrous sheet radiofrequency plasma. The layers not only act as an efficient fuel barrier layer but also impart high and stable proton conductivity, as well as better chemical and dimensional stabilities. Typically, the composite membrane exhibited methanol permeability as low as 33.20 x 10-8 cm2 s-1 and high through-plane proton conductivity of 52.4 mS cm-1 at 95% RH, indicating membrane selectivity of 0.675 x 108 mS.s cm-3, which is approximately 33 times greater than the selectivity of N115 under similar conditions.

The significant advancement and growth of organic and flexible electronic applications demand materials with enhanced properties. This paper reports the fabrication of a nonsynthetic polymer thin film using radio frequency plasma polymerisation of 3,7-dimethyl-1,6-octadien-3-ol. The fabricated optically transparent thin film exhibited refractive index of approximately 1.55 at 500 nm and rate of deposition was estimated to be 40 nm/min. The surface morphology and chemical properties of the thin films were also reported in this paper. The optical band gap of the material is around 2.8 eV. The force of adhesion and Young's modulus of the linalool polymer thin films were measured using force-displacement curves obtained from a scanning probe microscope. The friction coefficient of linalool polymer thin films was measured using the nanoscratch test. The calculated Young's modulus increased linearly with increase in input power while the friction coefficient decreased.

Plasma polymerized c-terpinene (pp2GT) thin films are fabricated using RF plasma polymerization. MIM structures are fabricated and using the capacitive structures dielectric properties of the material is studied. The dielectric constant values are found to be in good agreement with those determined from ellipsometric data. At a frequency of 100 kHz, the dielectric constant varies with RF deposition power, from 3.69 (10 W) to 3.24 (75 W). The current density–voltage (J2V) characteristics of pp–GT thin films are investigated as a function of RF deposition power at room temperature to determine the resistivity and DC conduction mechanism of the films. At higher applied voltage region, Schottky conduction is the dominant DC conduction mechanism. The capacitance and the loss tangent are found to be frequency dependent. The conductivity of the pp2GT thin films is found to decrease from 1.39 3 10212 S/cm (10 W) to 1.02 3 10213 S/cm (75 W) and attributed to the change in the chemical composition and structure of the polymer. The breakdown field for pp–GT thin films increases from 1.48 MV/cm (10 W) to 2 MV/cm (75 W). A single broad relaxation peak is observed indicating the contribution of multiple relaxations to the dielectric response for temperature dependent J2V. The distribution of these relaxation times is determined through regularization methods. VC 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42318.

By using electric-field-induced optical second-harmonic generation (EFISHG) measurement, we analyzed hysteresis behavior of capacitance-voltage (C-V) characteristics of IZO/polyterpenol (PT)/C₆₀/pentacene/Au diodes, where PT layer is actively working as a hole-transport electron-blocking layer. The EFISHG measurement verified the presence of interface accumulated charges in the diodes, and showed that a space charge electric field from accumulated excess electrons (holes) that remain at the PT/C₆₀ (C₆₀/pentacene) interface is responsible for the hysteresis loop observed in the C-V characteristics.

Electrical impedance spectroscopy measurements were performed on metal–insulator–metal structures using recently developed plasma deposited thin films of linalyl acetate as the insulating layer between frequencies of 10 Hz and 100 kHz in order to better understand this material's dielectric and structural properties. Furthermore, measurements were performed on samples fabricated under various input energy conditions to determine whether effects induced by these conditions influence the dielectric properties. The plasma deposited linalyl acetate thin films were found to be low dielectric constant across a wide range of frequencies, with primary contributions from electronic factors. Neither α- nor β-relaxation peaks were observed in the frequency range investigated at room temperature and no significant dependence of dielectric properties on input energy was observed. Samples were then investigated under heated conditions at four temperatures, where a single relaxation peak was found. This peak was quite broad, indicative of the contribution of multiple relaxations to the dielectric response. The distribution of these relaxation times was determined through regularisation methods. The breakdown field was investigated for samples at three thicknesses, and found to be approximately 1.8 MV/cm.

Contact angle and temperature-dependent variable angle spectroscopic ellipsometry measurements have been performed on plasma-deposited linalyl acetate thin films in order to provide insight into the compatibility of the material with current organic electronic fabrication techniques. XPS data on several substrates confirmed that the chemical properties of the thin films were substrate independent. The plasma-deposited layers were found to be insoluble in many solvents commonly used in the deposition of organic semiconducting layers, including chloroform and dichlorobenzene, and the wetting envelope for the surfaces presented. Thermal degradation was found to begin at ~200 °C, and up until this temperature the material’s thickness, refractive index and transparency in the visible region were constant. The exhibited properties show plasma-deposited linalyl acetate thin films to be compatible with state of the art organic electronic processing techniques.

Organic thin films have myriad of applications in biological interfaces, micro-electromechanical systems and organic electronics. Polyterpenol thin films fabricated via RF plasma polymerization have been substantiated as a promising gate insulating and encapsulating layer for organic optoelectronics, sacrificial place-holders for air gap fabrication as well as antibacterial coatings for medical implants. This study aims to understand the wettability and solubility behavior of the nonsynthetic polymer thin film, polyterpenol. Polyterpenol exhibited monopolar behavior, manifesting mostly electron donor properties, and was not water soluble due to the extensive intermolecular and intramolecular hydrogen bonds present. Hydrophobicity of polyterpenol surfaces increased for films fabricated at higher RF power attributed to reduction in oxygen containing functional groups and increased cross linking. The studies carried out under various deposition conditions vindicate that we could tailor the properties of the polyterpenol thin film for a given application.

The transparency of wood to microwave radiation is subject to changes in the wood's properties caused by softening of the wood material during fungal attack or the addition of moisture. A prototype microwave system that measures microwave attenuation and phase delay between two antennae was developed to detect fungal decay in wood at equilibrium moisture content. A total of twelve wooden stakes of 200 x 65 x 65 mm Pinus radiata (softwood) and twelve stakes of Eucalyptus regnans (hardwood) of the same dimensions were exposed to soil containing decay fungi for 12, 16, 20 and 24 weeks in an Accelerated Field Simulator (AFS), which is a climate conditioned room that simulates humid tropical conditions. A control set of three stakes of each wood type was also included in the experiment. Samples were washed and dried in an oven before testing with the prototype system. Orienting the antennae such that the microwave field was perpendicular to the wood grain could not distinguish between sound and decayed wood; however orienting the antennae so that the microwave fields were parallel to the wood grain and having the antennae pressed against the wood sample easily distinguished between sound wood and decayed wood. The phase delay data could not distinguish between sound or decayed wood.

Thin films of plasma polymerised linalyl acetate (PLA) were fabricated and their electrical properties investigated. The high frequency dielectric constant was determined using the split post dielectric resonator (SPDR) technique at frequencies of 10 GHz and 20 GHz and compared with the low frequency dielectric constant found from capacitive measurements of metal–insulator–metal (MIM) structures. Dielectric constants of 2.39 and 2.43 resulted from each of the respective techniques, in good agreement with each other. The J – V characteristics of MIM structures fabricated at various RF power levels were then investigated in order to determine the resistivity and DC conduction mechanism of the PLA thin films. From these data, the predominate mechanism of charge transport in the high voltage region was found to be consistent with Richardson–Schottky conduction, and the resistivity of the thin films found to increase with increasing RF power.