Simple and Precise Quantification of Iron Catalyst Content in Carbon Nanotubes Using UV/Visible Spectroscopy

Iron catalysts have been used widely for the mass production of carbon nanotubes (CNTs) with high yield. In this study, UV/visible spectroscopy was used to determine the Fe catalyst content in CNTs using a colorimetric technique. Fe ions in solution form red–orange complexes with 1,10-phenanthroline, producing an absorption peak at λ=510 nm, the intensity of which is proportional to the solution Fe concentration. A series of standard Fe solutions were formulated to establish the relationship between optical absorbance and Fe concentration. Many Fe catalysts were microscopically observed to be encased by graphitic layers, thus preventing their extraction. Fe catalyst dissolution from CNTs was investigated with various single and mixed acids, and Fe concentration was found to be highest with CNTs being held at reflux in HClO₄/HNO₃ and H₂SO₄/HNO₃ mixtures. This novel colorimetric method to measure Fe concentrations by UV/Vis spectroscopy was validated by inductively coupled plasma optical emission spectroscopy, indicating its reliability and applicability to asses Fe content in CNTs.     

Ceramic fuel cells using novel proton-conducting BaCe0.5Zr0.3Y0.1Yb0.05Zn0.05O3-δ electrolyte

Journal of Solid State Electrochemistry - Protonic ceramic fuel cells have become extremely interesting due to their high power output at the intermediate temperature range...     

Stable and high conductivity ceria/bismuth oxide bilayer electrolytes for lower temperature solid oxide fuel cells

A highly conductive bismuth oxide/ceria bilayer electrolyte was developed to reduce solid oxide fuel cell (SOFC) operating temperatures. Bilayer electrolytes were fabricated by depositing a layer of Er_0.2Bi_0.8O_1.5 (ESB) of varying thickness via pulsed laser deposition and dip-coating on a Sm_0.2Ce_0.8O_1.9 (SDC) substrate. The open-circuit potential (OCP) and ionic transference number (t _i) of ESB/SDC electrolytes were tested in a fuel cell arrangement as a function of relative thickness, temperature, and with H₂/H₂O and CO/CO₂ on the anode side and air on the cathode side. These EMF measurements showed a significant increase in OCP and t _i with the bilayer structure, as compared to the cells with a single SDC electrolyte layer. Furthermore, improvement in the OCP and t _i of bilayer SOFCs was observed with increasing relative thickness of the ESB layers. Hence, the bilayer structure overcomes the limited thermodynamic stability of bismuth oxides and prevents electronic conductivity of ceria-based oxides in reducing atmosphere.     

Analysis of underivatized amino acid mixtures using high performance liquid chromatography/dual oscillating nebulizer atmospheric pressure microwave induced plasma ionization-mass spectrometry

A dual oscillating capillary nebulizer (OCN) in conjunction with an atmospheric pressure microwave induced plasma ionization (AP-MIPI) source was applied to the analysis of underivatized amino acid mixtures. It was found that, compared to the single OCN, the dual OCN enhanced the sensitivity of detection several fold. Enhanced sensitivity was compound dependent. For small molecules, such as amino acids, it was 2-5 times more sensitive, while for larger molecules such as peptides it was more than an order of magnitude. The increase in sensitivity was attributed to the enhanced nebulization of the new torch. By using water/ acetonitrile containing 0.1% nonafluoropentanoic acid as the high performance liquid chromatography (HPLC) mobile phase and a C18 column, all common amino acids were separated and detected. A comparison between the results obtained using microwave induced plasma, atmospheric pressure chemical ionization (APCI), and electrospray ionization (ESI) at flow rates compatible with micro LC (10-100 microL/min) showed a higher sensitivity of detection with the AP-MIPI technique for the analysis of underivatized amino acids.     

Hydrogen adsorption in microporous hypercrosslinked polymers

A microporous hypercrosslinked polymer resin was synthesized and shown to adsorb 3.04 wt.% hydrogen at 77 K and 15 bar; this represents the highest level of hydrogen adsorption yet observed for an organic polymer.     

Preparation of Aromatic Polycarbonate Nanoparticles using Supercritical Carbon Dioxide

A novel synthetic process for producing aromatic polycarbonate (PC) nanoparticles using supercritical CO₂ was developed. The objective of the present research work was to synthesize high molecular weight PC nanoparticles using transesterification between bisphenol-A (BPA) and diphenyl carbonate (DPC) in supercritical CO₂ which is an excellent plasticizing agent and a good solvent for phenol, a by-product of the reaction. Poly(propylene oxide)–poly(ethylene oxide)–poly(propylene oxide) tri-block copolymer with CO₂-phobic anchor and CO₂-philic tail group was used as a stabilizer for the preparation of stable dispersions of BPA–DPC mixture in a CO₂ continuous phase. As the reaction was proceeding, phenol formed from the reaction was dissolved and diffused into supercritical CO₂ phase. The PC nanoparticles were isolated by simple venting of the supercritical CO₂ from the reactor. Spherical morphology of PC particles was confirmed by scanning electron microscopy. Particle size and morphology of PC particles were modified upon variation of the process conditions. The resulting PC particles with a nano-size of 30–140nm have a high molecular weight (M _w) of 3.1×10⁵ (g/mol).     

Transparent,thermally stable methyl siloxane hybrid materials using sol-gel synthesized vinyl-methyl oligosiloxane resin

Journal of Sol-Gel Science and Technology - Vinyl-methyl oligosiloxane resin was synthesized by a hydrolytic sol-gel reaction of vinyltriethoxysilane and dimethyldiethoxysilane. Hydrochloric acid...     

Process Characterization of hCTLA4Ig Production in Transgenic Rice Cell Cultures Using a 3-L Bioreactor

Most of the technical know-how and experience of bioreactor engineering is applicable to plant cell cultures. In this study, transgenic rice cell cultures using RAmy3D promoter were used for the production of human cytotoxic T-lymphocyte antigen 4-immunoglobulin (hCTLA4Ig). In process aspect, the rice cells during production phase are strongly influenced by hydrodynamic stresses, such as shear stress and bubble burst. Therefore, the effects of agitation and aeration rates on cell growth and hCTLA4Ig production were investigated in a 3-L multi-bioreactor. By increasing over 240 rpm, the detrimental effects on cell growth and hCTLA4Ig production were observed. At an aeration rate of 0.3 vvm, relative cell viability sharply decreased 2 days earlier than those of lower aeration rates. In addition, it was confirmed that the specific yields and the specific productivity at 0.3 vvm were superior to those values at 0.05 vvm. Overall, higher aeration rate showed the improved hCTLA4Ig production in combination experiment. High aeration rates in general, however, have an undesired effect as excessive aeration was found to negatively affect the quality of hCTLA4Ig. Consequently, the hydrodynamic conditions must be tightly regulated during bioreactor operation in order to enhance hCTLA4Ig productivity and quality in transgenic rice cell cultures.     

Liquid crystal alignment and pretilt angle generation on a photopolymer layer based on N-(phenyl)maleimide

A photopolymer based on N-(phenyl)maleimide was synthesized and the liquid crystal (LC) alignment effects of the photopolymer layer on homeotropic alignment were studied. Good LC alignment with UV exposure of PMI5CA (N-(phenyl)maleimide with a 5-carbon chain cinnamoyl group) was obtained. However, defective LC alignment was observed for PMI3CA (N-(phenyl)maleimide with a 3-carbon chain cinnamoyl group) and PMIF (N-(phenyl)maleimide including a fluoro-cinnamoyl group). Good LC alignment with UV exposure on the PMI5CA surface was observed with annealing temperature up to 150°C. It seems that the LC aligning ability of the photopolymer layers based on N-(phenyl)maleimide depends on the side chain length of the photopolymer.