Growth, Characterization, and Application of Vertically Aligned Carbon Nanotubes Using the RF-Magnetron Sputtering Method

The aim of this work is to synthesize and characterize a nanostructured material with improved parameters suitable as a chemiresistive gas sensor sensitive to propylene glycol vapor (PGV). Thus, we demonstrate a simple and cost-effective technology to grow vertically aligned carbon nanotubes (CNTs) and fabricate a PGV sensor based on Fe₂O₃:ZnO/CNT material using the radio frequency magnetron sputtering method. The presence of vertically aligned carbon nanotubes on the Si(100) substrate was confirmed by scanning electron microscopy and Fourier transform infrared (FTIR), Raman, and energy-dispersive X-ray spectroscopies. The uniform distribution of elements in both CNTs and Fe₂O₃:ZnO materials was revealed by e-mapped images. The hexagonal shape of the ZnO material in the Fe₂O₃:ZnO structure and the interplanar spacing in the crystals were clearly visible by transmission electron microscopy images. The gas-sensing behavior of the Fe₂O₃:ZnO/CNT sensor toward PGV was investigated in the temperature range of 25-300 °C with and without ultraviolet (UV) irradiation. The sensor showed clear and repeatable response/recovery characteristics in the PGV range of 1.5-140 ppm, sufficient linearity of response/concentration dependence, and high selectivity both at 200 and 250 °C without UV radiation. This is a basis for concluding that the synthesized Fe₂O₃:ZnO/CNT structure is the best candidate for use in PGV sensors, which will allow its further successful application in real-life sensor systems.

Flexible, ultrathin and light films from one-dimensional nanostructures of polypyrrole and cellulose nanofibers for high performance electromagnetic interference shielding

Combining highly conducting one-dimensional nanostructures of polypyrrole with cellulose nanofibers (CNF) into flexible films with tailored electrical conductivity and mechanical properties presents a promising route towards the development of eco-friendly electromagnetic interference shielding devices. Herein, conducting films with a thickness of 140 μm were synthesized from polypyrrole nanotubes (PPy-NT) and CNF using two approaches, i.e., a new one-pot synthesis consisting of in situ polymerization of pyrrole in the presence of structure guiding agent and CNF, and a two-step synthesis, in which CNF and PPy-NT were physically blended. Films based on one-pot synthesis (PPy-NT/CNF_in) exhibited higher conductivity than those processed by physical blending, which was further enhanced up to 14.51 S cm^-1 after redoping using HCl post-treatment. PPy-NT/CNF_in containing the lowest PPy-NT loading (40 wt%), thus the lowest conductivity (5.1 S cm^-1), displayed the highest shielding effectiveness of -23.6 dB (>90 % attenuation), thanks to the good balance between its mechanical properties and electrical conductivity.

Room Temperature Detection of Hydrogen Peroxide Vapor by Fe2O3:ZnO Nanograins

In this report, a Fe₂O₃:ZnO sputtering target and a nanograins-based sensor were developed for the room temperature (RT) detection of hydrogen peroxide vapor (HPV) using the solid-state reaction method and the radio frequency (RF) magnetron sputtering technique, respectively. The characterization of the synthesized sputtering target and the obtained nanostructured film was carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX) analyses. The SEM and TEM images of the film revealed its homogeneous granular structure, with a grain size of 10-30 nm and an interplanar spacing of Fe₂O₃ and ZnO, respectively. EDX spectroscopy presented the real concentrations of Zn in the target material and in the film (21.2 wt.% and 19.4 wt.%, respectively), with a uniform distribution of O, Al, Zn, and Fe elements in the e-mapped images of the Fe₂O₃:ZnO film. The gas sensing behavior was investigated in the temperature range of 25-250 °C with regards to the 1.5-56 ppm HPV concentrations, with and without ultraviolet (UV) irradiation. The presence of UV light on the Fe₂O₃:ZnO surface at RT reduced a low detection limit from 3 ppm to 1.5 ppm, which corresponded to a response value of 12, with the sensor's response and recovery times of 91 s and 482 s, respectively. The obtained promising results are attributed to the improved characteristics of the Fe₂O₃:ZnO composite material, which will enable its use in multifunctional sensor systems and medical diagnostic devices.

Pressure-Sensitive Conducting and Antibacterial Materials Obtained by in Situ Dispersion Coating of Macroporous Melamine Sponges with Polypyrrole

Melamine sponges were coated with polypyrrole during the in situ polymerization of pyrrole. The precipitation polymerization was compared with the dispersion mode, that is, with the preparation in the presence of poly(N-vinylpyrrolidone) and nanosilica as colloidal stabilizers. The coating of sponges during the dispersion polymerization leads to the elimination of the undesired polypyrrole precipitate, improved conductivity, and increased specific surface area. The sponges were tested with respect to their conductivity and as pressure-sensitive conducting materials with antibacterial performance.

One-Dimensional Nanostructures of Polypyrrole for Shielding of Electromagnetic Interference in the Microwave Region

Polypyrrole one-dimensional nanostructures (nanotubes, nanobelts and nanofibers) were prepared using three various dyes (Methyl Orange, Methylene Blue and Eriochrome Black T). Their high electrical conductivity (from 17.1 to 60.9 S cm-1), good thermal stability (in the range from 25 to 150 °C) and resistivity against ageing (half-time of electrical conductivity around 80 days and better) were used in preparation of lightweight and flexible composites with silicone for electromagnetic interference shielding in the C-band region (5.85-8.2 GHz). The nanostructures' morphology and chemical structure were characterized by scanning electron microscopy, Brunauer-Emmett-Teller specific surface measurement and attenuated total reflection Fourier-transform infrared spectroscopy. DC electrical conductivity was measured using the Van der Pauw method. Complex permittivity and AC electrical conductivity of respective silicone composites were calculated from the measured scattering parameters. The relationships between structure, electrical properties and shielding efficiency were studied. It was found that 2 mm-thick silicone composites of polypyrrole nanotubes and nanobelts shield almost 80% of incident radiation in the C-band at very low loading of conductive filler in the silicone (5% w/w). Resulting lightweight and flexible polypyrrole composites exhibit promising properties for shielding of electromagnetic interference in sensitive biological and electronic systems.

Influence of non-thermal plasma on structural and electrical properties of globular and nanostructured conductive polymer polypyrrole in water suspension

Non-thermal plasma has proved its benefits in medicine, plasma assisted polymerization, food industry and many other fields. Even though, the ability of non-thermal plasma to modify surface properties of various materials is generally known, only limited attention has been given to exploitations of this treatment on conductive polymers. Here, we show study of non-thermal plasma treatment on properties of globular and nanostructured polypyrrole in the distilled water. We observe that plasma presence over the suspension level doesn't change morphology of the polymer (shape), but significantly influences its elemental composition and physical properties. After 60 min of treatment, the relative concentration of chloride counter ions decreased approximately 3 and 4 times for nanostructured and globular form, respectively and concentration of oxygen increased approximately 3 times for both forms. Simultaneously, conductivity decrease (14 times for globular and 2 times for nanostructured one) and changes in zeta potential characteristics of both samples were observed. The modification evolution was dominated by multi-exponential function with time constants having values approximately 1 and 10 min for both samples. It is expected that these time constants are related to two modification processes connected to direct presence of the spark and to long-lived species generated by the plasma.

Synthesis of silver-anchored polyaniline–chitosan magnetic nanocomposite: a smart system for catalysis

A novel and smart four component system composed of chitosan, polyaniline, magnetite and silver was exploited for catalysis.

Dye-stimulated control of conducting polypyrrole morphology

Three azo dyes bearing hydrophilic functional groups at different positions on a hydrophobic naphthylphenyldiazene skeleton were used as structure-guiding agents in the synthesis of highly organised supramolecular structures of PPy in aqueous media.

Polypyrrole Nanotubes and Their Carbonized Analogs: Synthesis, Characterization, Gas Sensing Properties

Polypyrrole (PPy) in globular form and as nanotubes were prepared by the oxidation of pyrrole with iron(III) chloride in the absence and presence of methyl orange, respectively. They were subsequently converted to nitrogen-containing carbons at 650 °C in an inert atmosphere. The course of carbonization was followed by thermogravimetric analysis and the accompanying changes in molecular structure by Fourier Transform Infrared and Raman spectroscopies. Both the original and carbonized materials have been tested in sensing of polar and non-polar organic vapors. The resistivity of sensing element using globular PPy was too high and only nanotubular PPy could be used. The sensitivity of the PPy nanotubes to ethanol vapors was nearly on the same level as that of their carbonized analogs (i.e., ~18% and 24%, respectively). Surprisingly, there was a high sensitivity of PPy nanotubes to the n-heptane vapors (~110%), while that of their carbonized analog remained at ~20%. The recovery process was significantly faster for carbonized PPy nanotubes (in order of seconds) compared with 10 s of seconds for original nanotubes, respectively, due to higher specific surface area after carbonization.

Polypyrrole salts and bases: superior conductivity of nanotubes and their stability towards the loss of conductivity by deprotonation

Polypyrrole nanotubes exhibit conductivity of tens S cm⁻¹ which is one of the highest among the current conducting polymers.

Chromosome pairing of individual genomes in tall fescue (Festuca arundinacea Schreb.), its progenitors, and hybrids with Italian ryegrass (Lolium multiflorum Lam.)

A diploid-like pairing system prevents meiotic irregularities and improves the efficiency of gamete production in allopolyploid species. While the nature of the system is known in some polyploid crops including wheat, little is known about the control of chromosome pairing in polyploid fescues (Festuca spp.). In this work we studied chromosome pairing in allohexaploid F. arundinacea, its progenitors F. pratensis and F. glaucescens, and two intergeneric hybrids Lolium multiflorum (2x) x F. arundinacea (6x) and L. multiflorum (4x) x F. glaucescens (4x). The use of genomic in situ hybridization (GISH) permitted the analysis of homoeologous chromosome pairing and recombination of different genomes involved. We detected a diploid-like pairing system in polyploid fescues F. arundinacea and F. glaucescens, the latter being one of the progenitors of F. arundinacea. The pairing control system was absent in the second progenitor F. pratensis. Detailed analysis of intergeneric hybrids confirmed the presumed haploinsufficiency of the fescue system, which resulted in homoeologous pairing between all component genomes. This indicates that introgression of any specific chromosome segment from one genome to another is possible in all genome combinations. Our results not only contribute to the quest to discover the nature of the system controlling chromosome pairing in polyploid fescues, but may also have serious implications for design of hybrid breeding schemes in forage grasses.

Cytogenetics of Festulolium (Festuca x Lolium hybrids)

Grasses are the most important and widely cultivated crops. Among them, ryegrasses (Lolium spp.) and fescues (Festuca spp.) provide high quality fodder for livestock, are used for turf and amenity purposes, and play a fundamental role in environment protection. Species from the two genera display complementary agronomic characteristics and are often grown in mixtures. Breeding efforts to combine desired features in single entities culminated with the production of Festuca x Lolium hybrids. The so called Festuloliums enjoy a considerable commercial success with numerous cultivars registered all over the world. They are also very intriguing from a strictly cytogenetic point of view as the parental chromosomes recombine freely in hybrids. Until a decade ago this phenomenon was only known in general quantitative terms. The introduction of molecular cytogenetic tools such as FISH and GISH permitted detailed studies of intergeneric chromosome recombination and karyotyping of Festulolium cultivars. These tools were also invaluable in revealing the origin of polyploid fescues, and facilitated the development of chromosome substitution and introgression lines and physical mapping of traits of interest. Further progress in this area will require the development of a larger set of cytogenetic markers and high-resolution cytogenetic maps. It is expected that the Lolium-Festuca complex will continue providing opportunities for breeding superior grass cultivars and the complex will remain an attractive platform for fundamental research of the early steps of hybrid speciation and interaction of parental genomes, as well as the processes of chromosome pairing, elimination and recombination.

Genome constitution and evolution in Lolium x Festuca hybrid cultivars (Festulolium)

Festulolium hybrids are being increasingly used worldwide as forage grasses. This is due to their superior agronomic characteristics, which combine yield performance of ryegrasses (Lolium multiflorum and L. perenne) and tolerance against abiotic stress of fescues (Festuca pratensis, F. arundinacea and F. arundinacea var. glaucescens). Despite the widespread use, only fragmentary information exists on their genomic constitution. We used genomic in situ hybridization (GISH) to analyze genomic constitution of over 600 plants from almost all commercially available cultivars of Festulolium. Our results revealed a surprisingly large range of variation in the proportions of parental genomes and in the extent of intergenomic recombination. Using fluorescence in situ hybridization (FISH) with probes for ribosomal DNA, we assessed the frequency of recombination and elimination of particular chromosomes and chromosome groups in three contrasting Festulolium cultivars. This study provides novel information that will aid in understanding the relationship between a genetic make-up and the phenotype of Festulolium hybrids. Our results indicate that GISH might be a useful tool to aid in Festulolium breeding and provide data for a more detailed description of registered cultivars.