Non-covalent ruthenium polypyridyl complexes-carbon nanotubes composites: an alternative for functional dissolution of carbon nanotubes in solution

The dispersion of single-walled carbon nanotubes (SWCNTs) in the presence of water soluble polypyridyl complexes of the general formula [Ru(x)(bpy)(y)L](2+) (L = dppz, dppn, tpphz) is reported. These ligands have extended planar π systems, which aid in the solubilization of SWCNTs via π-π interactions.     

Dual template approach for the synthesis of hierarchically mesocellular carbon foams

We demonstrated a simple and effective dual-templating approach for the synthesis of hierarchically mesocellular carbon foams by using nonionic surfactant of sorbitan monooleate and silica colloid particles as sacrificial templates, and resorcinol/ formaldehyde as carbon source. The representative carbon foam has dual mesopore sizes of 4 and 10 nm, and possesses the specific surface area of 580 m2/g and the total pore volume of 0.80 cm3/g.     

Low-cost and facile synthesis of mesocellular carbon foams

Mesocellular carbon foam composed of nanometer sized primary particles was synthesized using hydrothermally synthesized MSU-F silica as a template and poly(furfuryl alcohol) as a carbon source.     

Design and characterization of three-dimensional carbon nanotube foams

We demonstrate a new method that makes use of colloidal silica templates to fabricate porous three-dimensional architectures of carbon nanotubes (CNTs). CNTs were grown on monolayered and multilayered structures of colloidal silica using chemical vapor deposition. Porous CNT membranes and three-dimensional carbon nanotube foams were obtained by treating these silica-CNTs structures with HF. The membranes and foams of CNT so obtained were chemically and mechanically stable and were characterized by using scanning electron microscopy and energy dispersive spectroscopy.     

Spray desorption collection: an alternative to swabbing for pharmaceutical cleaning validation

Spray Desorption Collection (SDC) allows for much larger areas of surfaces to be sampled compared to traditional swabbing techniques, providing a valuable pre-concentration advantage. Closely related to desorption electrospray ionization (DESI), analytes from the sample surface are collected onto a selected collection surface, which in a second step can be analyzed directly. Here we demonstrate the application of SDC as a large surface area sampling tool coupled with paper spray MS (PS-MS) and demonstrate its capabilities for cleaning validation of pharmaceutical equipment for both acidic and basic active ingredients from an aluminium surface.     

Use of dichloromethane with dithizone as an alternative solvent to carbon tetrachloride restricted by Montreal protocol

The spectral characteristics of dithizone and its metal complexes were measured in dichloromethane as an alternative solvent to carbon tetrachloride which will be illegal to manufacture by the year 2000, according to the revised Montreal Protocol. The extraction equilibria of its metal complexes were also reported and discussed. Dichloromethane was found to enhance the sensitivity of dithizone towards Co(II), Cu(II), Hg(II), Pb(II), Zn(II), Bi(III), Ag(I), In(III) and Tl(I). It was also found to be a better solvent than carbon tetrachloride for the separation of Cd(II) from Zn(II) and for the separation of Co(II) from Ni(II).     

Spectroscopic detection of Saxitoxin: an alternative to mouse bioassay

Herein, we report the surface modification of quartz with a coumaryl-aza-crown-6 derivative to detect Saxitoxin using fluorescence enhancement through Photoinduced Electron Transfer and the sensitivity with this system approaches the limit of the mouse bioassay which is the current benchmark for Saxitoxin detection.     

Photochemistry of p-chloromercurobenzophenone: Photoreduction as an alternative to demercuration

p-Chloromercurobenzophenone exhibits dual reactivity during photolysis: in solvents that are hydrogen donors it is photoreduced with the formation of a mercury-containing ketyl radical, while in other solvents it undergoes demercuration. Photolysis of p-chloromercurobenzophenone by both paths occurs from the triplet excited state.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1738–1742, August, 1990.     

Investigation of graphitic carbon foams/LiNiPO4 composites

The characterization of composites consisting of graphitic carbon foams coated with a structured lithium nickel phosphate is reported. The LiNiPO₄ as cathode material for lithium-ion batteries is prepared by a Pechini-assisted sol-gel process. The coating is performed by soaking the graphitic carbon foams in aqueous solutions containing lithium, nickel salts, and phosphates at 70?°C for 2–4?h and then by treating in flowing air and nitrogen. The formation of the olivine-like structured LiNiPO₄ is confirmed by X-ray diffraction analysis performed on powders prepared under very similar conditions. However, crystalline reflections attributed to Li₄P₂O₇ and to Ni₃P as secondary phases have been observed. The morphological investigation revealed the presence of a layer on the graphitic foams that consists of interconnected blend of grains with different size. The voltammetric curves show values of the mean peak maxima in the anodic region between 5.1–5.3?V and in the cathodic region at ~4.9?V. The electrochemical measurements deliver a discharge specific capacity of 86?mAhg^?1 (at discharge rate of C/10 and RT). The electrochemical impedance spectroscopy data confirm an increase of the electrical resistance after cycling and the decrease of the ionic contribution which indicate the formation/growth of phases behaving like resistors.     

CHEMLEARN: microcomputer-based training for CHEMLINE, an alternative to formal classroom training

CHEMLINE (CHEMical Dictionary OnLINE), the National Library of Medicine's online chemical dictionary file, is primarily used by librarians and information scientists to enhance the retrieval of bibliographic information associated with chemical substances. This paper will discuss CHEMLEARN, a microcomputer-based training program designed to provide inexpensive, easily accessible self-instruction as an alternative to formal classroom training in the use of CHEMLINE. CHEMLEARN allows novice users to learn at their own pace and with considerable program feedback. In addition, it provides the skilled searcher with a way to reinforce or recall previously learned search techniques without incurring online charges. CHEMLEARN may be used in place of formal training or as a precursor to or a refresher following formal training.     

Measurement uncertainty evaluation for a non-negative measurand: an alternative to limit of detection

The interpretation and reporting the results of measurements on materials where the concentration of the analyte is close to or may even be zero has been the subject of much discussion with the use of such concepts as limit of detection (LOD) and limit of quantification (LOQ). While these concepts have taken into account the measurement uncertainty, they have not utilised the fact that the value of the measurand, i.e., the concentration, is constrained to be zero or greater. Taking this into account the distribution of values attributable to the measurand can be derived from the probability density function (PDF) that determines the distribution of the observed values. When this PDF is normal the distribution of the values attributable to the measurand is a truncated t distribution with a lower limit of re-normalised so that the total probability is one, where x _m is the mean of the n observed values and s their standard deviation. When x _m much greater than then the distribution reverts to the unmodified t distribution. The probability that the value of the measurand is above or below a limit can be calculated directly from this truncated t distribution and the interpretation of the result does not require the use of concepts such as LOD and LOQ. Also it deals with the problem of negative observations. This Report was written by Alex Williams (e-mail: aw@camberley.demon.co.uk) for the Statistical Subcommittee and approved by the Analytical Methods Committee.     

Zwitteration as an alternative to PEGylation

A direct, head-to-head comparison of the efficacy of a zwitterionic versus a poly(ethylene glycol), PEG, coating in preventing protein adsorption to silica and aggregation of silica nanoparticles is presented. The same siloxane coupling chemistry was employed to yield surfaces with similar coverages of both types of ligand. Nanoparticle and planar surfaces were challenged with salt, serum, lysozyme, and serum albumin at 25 and 37 °C. While both types of surface modification are highly effective in preventing protein adsorption and nanoparticle aggregation, the zwitterion provided monolayer-type coverage with minimal thickness, whereas the PEG appeared to yield a more three-dimensional coating. The mechanism for adsorption resistance is thought to be based on preventing ion pairing between protein and surface charges, which releases counterions and water molecules, an entropic driving force enough to overcome a disfavored enthalpy of adsorption.     

Bioelectrosynthesis as an alternative to photosynthesis

The CO₂ reduction processes have been discussed as a way of designing an ecologically totally closed technology. An electric current and molecular hydrogen are the two related available agents that can be discussed as ecologically pure reductants. The most important products are liquid and gaseous fuels, the products of large-scale organic synthesis, monomers, and amino acids. For CO₂ reduction, the necessary energy consumption and H₂ costs were calculated. For complex organic molecules, amino acids for instance, the energy consumption does not make up the main portion of the costs. The biocatalytic systems of CO₂ reduction based on cryoimmobilized cells are described. Conversion of CO₂ into L-lysine with electrochemical decomposition of water was effected on the laboratory scale. A general unit for diverse technological processes can be a bioelectrosynthetic Index Entries: Bioelectrosynthesis; CO₂ reduction; liquid fuels; amino acids; immobilized cells; economic estimates. modulus, an electrochemical hydrogen generator coupled with a biocatalytic converter of hydrogen and oxygen. The systems for bioelectrosynthesis of motor fuels and essential amino acids have been economically estimated and characterized. The possibilities of combining the solar energy transformation and H₂–CO₂ conversion have been discussed.     

ESCA investigations on pyrolytic carbon films for fiber coatings

Photoelectron spectroscopy on pyrolytic carbon films revealed a main part of carbon atoms in graphitic planes and a smaller part of functional groups with oxygen bonded to carbon atoms. Oxygen totalled a share of 10 at% and more of the carbon coating. The films with a turbostratic structure consist of nearly parallel oriented atomic layers of hexagonal rings with dimensions in the nanometer scale, which is well known from HREM investigations. The oxygen atoms are proposed to saturate the numerous dangling bonds around these individual atomic planes. The oxygen atoms form double bonds or bridges between carbon atoms. Received: 15 July 1998 / Revised: 28 January 1998 / Accepted: 2 February 1998     

Diamond-like carbon coatings with Ca-O-incorporation for improved biological acceptance

Diamond-like carbon (DLC) coatings were modified by doping the thin films with Ca-O compounds. Raman spectroscopy indicates growth of sp(2)-hybridised, ordered regions in size and/or number within the amorphous carbon-hydrogen network as a result of the Ca-O-incorporation. CaCO(3) was identified by X-ray induced photoelectron spectroscopy. Proliferation and morphology of L929 mouse fibroblasts reveal improved biocompatibility of Ca-O-modified DLC.     

Polyphosphonium polymers for siRNA delivery: an efficient and nontoxic alternative to polyammonium carriers

A water-soluble polyphosphonium polymer was synthesized and directly compared with its ammonium analog in terms of siRNA delivery. The triethylphosphonium polymer shows transfection efficiency up to 65% with 100% cell viability, whereas the best result obtained for the ammonium analog reaches only 25% transfection with 85% cell viability. Moreover, the nature of the alkyl substituents on the phosphonium cations is shown to have an important influence on the transfection efficiency and toxicity of the polyplexes. The present results show that the use of positively charged phosphonium groups is a worthy choice to achieve a good balance between toxicity and transfection efficiency in gene delivery systems.     

Stepwise acid-promoted double-Michael process: an alternative to Diels-Alder cycloadditions for hindered silyloxydiene-dienophile pairs

The hindered diene 1 reacts with 3-methylcyclohexenone 6 catalyzed by triflimide to produce the Mukaiyama Michael product 7 (low-temperature quenching) or the [4+2] cycloadduct 8 (quenching at 0 degrees C). Reaction of the hindered diene 23 with 2-methylcyclohexenone 12 with 5:1 AlBr3:AlMe3 afforded a 71% yield of a 1.9:1 mixture of two cycloadducts. Hydrolysis of the major isomer gave the dione 27', a model for the BCD ring system of pentacyclic triterpenes. [reaction: see text].