Thomas Borrmann

Silver nanoparticle–clay composites

Composite materials of the alumino silicate minerals, kaolinite and halloysite, with silver nanoparticles have been successfully synthesised. This was achieved by a layer-by-layer deposition process in which kaolinite or halloysite was dispersed in successive solutions of the cationic polymeric linker polydiallyldimethylammonium chloride and anionic polymethacrylic acid capped silver nanoparticles. The optical properties of the metallic nanoparticles were retained in the composites and attractively coloured powders were produced. Electron microscopy revealed the silver to be nanospheres, ranging in diameter from 5–40 nm depending on the method of preparation. The chemical and physical characterisation of the resultant composites, particularly the mode of bonding between the nanoparticles and clays, was undertaken through X-ray diffraction, X-ray photoelectron spectroscopy and solid state NMR. The composites showed effective anti-microbial activity against Staphylococcus aureus bacteria.

Calcium-phosphorus interactions at a nano-structured silicate surface.

Nano-structured calcium silicate (NCS), a highly porous material synthesized by controlled precipitation from geothermal fluids or sodium silicate solution, was developed as filler for use in paper manufacture. NCS has been shown to chemisorb orthophosphate from an aqueous solution probably obeying a Freundlich isotherm with high selectivity compared to other common environmental anions. Microanalysis of the products of chemisorption indicated there was significant change from the porous and nano-structured morphology of pristine NCS to fibrous and crystalline morphologies and non-porous detritus. X-ray diffraction analysis of the crystalline products showed it to be brushite, CaHPO42H2O, while the largely X-ray amorphous component was a mixture of calcium phosphates. A two-step mechanism was proposed for the chemisorption of phosphate from an aqueous solution by NCS. The first step, which was highly dependent on pH, was thought to be desorption of hydroxide ions from the NCS surface. This was kinetically favoured at lower initial pH, where the predominant form of phosphate present was H2PO(-)4, and led to decreased phosphorus uptake with increasing pH. The second step was thought to be a continuing chemisorption process after stabilization of the pH-value. The formation of brushite as the primary chemisorption product was found to be consistent with the proposed mechanism.

Hybrid materials of conducting polymers with natural fibres and silicates

The preparation, characterisation and properties of new hybrid materials of the conducting polymers polypyrrole and polyaniline with cellulose substrates in the form of paper fibres, paper sheets and wood; merino wool fibres; and kaolinite particles are presented. The conducting polymers form as spheres of about 50-150 nm that are fused together as a continuous coating which fully encapsulates the substrate fibre or particulate surface. The polymer is chemically bound to the hydroxyl or amine groups on the substrate surface by hydrogen bonding. The resulting hybrid materials exhibit the properties of both precursors. Thus the electrical conductivity, optical and chemical properties of the particular conducting polymer are combined with the mechanical strength and integrity of the wood and cement board, the tensile strength and flexibility of the wool and paper fibres and paper sheets, and particulate nature of the silicates respectively. The redox properties of the conducting polymer can be used to deposit silver nanoparticles on the hybrid surface thereby imparting anti-microbial activity to it. These new hybrid materials provide an attractive approach to overcoming the inherent processability difficulties encountered with conducting polymers and open up opportunities for the development of new consumer products and applications.

N-chlorination and Orton Rearrangement of Aromatic Polyamides, Revisited

Polyamide membranes are widely used in water desalination. It is known that they suffer degradation due to the presence of free chlorine. This communication shows a detailed chemical reaction mechanism for the N-chlorination and Orton rearrangement of poly (m-phenylene isophthalamide), which is the linear aromatic polyamide component of the commonly used B-9 Permasep® membrane. The N-chlorination of this aromatic polyamide causes the loss of hydrogen bonding. This triggers conformational changes in the polymer; the polymer becomes less rigid and, void spaces open up, which decreases solute rejection and increases water flux. The N-Chlorination reaction is reversible in alkaline media. Therefore, if the polymer is suspected to have come into contact with hypochlorite anions or hypochlorous acid immediate cleaning with sodium hydroxide could reverse the N-chlorination. Conversely, the N-chlorination is acid catalyzed; hence, special care has to be taken during the cleaning stage, when HCl is used. Furthermore, N-chlorinated aromatic polyamides can undergo an Orton rearrangement, which is also promoted in acidic media, resulting in the formation of ortho- or para-chloro substituted analogues of the aromatic amide moiety. The chloro group causes a strong negative inductive effect weakening the amide bond making it more susceptible to hydrolysis, which eventually produces chain scission.

Rhodium catalysts build into the structure of a silicate support in the hydroformylation of alkenes

AbstractRhodium is build into a nano-structured calcium silicate during the synthesis of the silicate. Thereby, it was desired to create a robust heterogeneous catalyst, which does not suffer from catalyst leaching like rhodium impregnated on a pre-formed silicate. While this was achieved, the silicate structure was adversely affected by the incorporation of rhodium — the surface area and pore volume of the material were found to be comparatively low. Alcohol and acid washing were tested to address this issue. The alcohol treatment proved detrimental as catalytic material was leached from the silicate. The acid washed rhodium containing calcium silicate was quite active in the hydroformylation of alkenes and did not suffer loss of catalyst into the product phase. Acid treated rhodium containing silicates were more active than their untreated counterparts but less selective due to access to the rhodium centers being opened.

Nano-structured calcium silicate hydrate functionalised with iodine

Nano-structured calcium silicate hydrate can physisorb or chemisorb iodine, making it interesting for medical or materials science applications, where a slow, controlled release of iodine is desired. It was found that iodine can be sorbed and released by applying the elemental halogen in solution, either as a gas or as a solid. At ambient temperatures the sorption and desorption process is quantitative and physical, meaning that the same amount of iodine is taken up and released. At temperatures above 32.5 degrees C (305.7K) iodine reacts with the calcium silicate hydrate forming a complex, which is stable above the sublimation temperature of iodine. The formation energy for the iodine calcium silicate hydrate complex was established to be 41.8+/-0.8kJmol(-1) by calorimetry and the nature of the complex was investigated using X-ray photoelectron spectroscopy.

Nano-structured calcium silicate as sorbent in a study of artificial mining waste

Nano-structured calcium silicate can adsorb a wide variety of ionic species. The mechanism of the uptake observed depends on the nature of the species and is selective towards the more insoluble hydroxides for cationic and insoluble calcium compounds for anionic sources. Additionally, waterborne solids can become trapped, with the silicate, acting as a filter. Artificial mining waste samples have been studied to show synergies and challenges, if the silicate is applied in commercial systems. From this investigation interesting possibilities for the synthesis of silicate derivatives aimed at the sorption of specific ions were formulated and tested.

Gold nanoparticles on wool in a comparative study with molecular gold catalysts

The catalytic activity of gold chloride nanoparticles is compared to the activity of two molecular gold(I) chloride phosphine complexes for the addition of methanol to 3-hexyne. The phosphines are triphenylphosphine and the bispidinone related bulky 6,8-bis-(4-dimethylamino-phenyl)-3-methyl-9-oxo-7-phenyl-3-aza-7-phospha-bicyclo[3.3.1]nonan-1,5-dicarboxylic acid dimethyl ester. Use of the bulky ligand made the addition reaction selective towards the enol product, meaning that no addition of methanol or water to alkenes, which were produced during the reaction, occurred. In contrast, use of triphenylphosphine gold(I) chloride resulted in the synthesis of a variety of products. The phosphines decomposed during reaction leading to the formation of gold nanoparticles, which were found to be catalytically inactive. Artificially produced gold nanoparticles also proved to be inactive. In contrast, gold chloride nanoparticles deposited on wool were active comparable to the gold phosphine-containing catalysts tested previously. Overall activities observed were low compared to results from the literature suggesting that the operating conditions chosen could be optimised.

Aulana : Novel Nanogold Coloured Wool Textiles for Luxury Markets

Aulana® is a new technology and luxury nanogold-wool textile product suite, which innovatively combines the nanoscience of gold with wool fibres to produce nanogold-wool textiles in a boutique colour range for high value international luxury markets. Aulana® captures the exciting and unique opportunity whereby the prestige and high value of gold are linked directly to the high quality of New Zealand wool through the use of nanogold as novel stable colourfast colourants in the wool, for the international high quality fashion apparel, luxury textiles and rug markets 1 (Figure 1). This utilises the localised surface plasmon resonance properties of nanogold wherein the colour exhibited by the gold is dependent upon the size and shape of the nanogold particles and the dielectric constant of the surrounding material 1,2. These nanoparticles are chemically bound to the sulfur and nitrogen containing amino acids in the wool fibre proteins on the cuticle surfaces and edges (Figure 2). Spherical particles of gold about 10-20 nm are pink-red in colour 1-3. Precise control of the particle size enables the colour to be changed progressively through shades of pink, red, purple, blue-grey to grey (Figure 3). Gold nanorods potentially offer shades of blue, green and red colours, depending upon the aspect ratio of the gold nanorods 4, however their commercial production is problematic. We have developed an alternative synthesis for blue nanoparticles 5. Nanogold colourants cannot fade or denature in sunlight and hence the nanogold coloured wool products exhibit excellent lightfastness. Electronmicroscopy and associated X-ray elemental mapping and X-ray photoelectron spectroscopy show the nanogold is primarily bound to N and S entities on the cuticle edges. The proprietary Aulana® technology and product suite have been developed on a laboratory scale and progressed to pilot and commercial scale production using combed top wool, yarn (Figure 3) and fabric, in stainless steel textile dyeing equipment. Noble Bond Ltd which owns the Aulana® brand, is commercialising Aulana® products in luxury apparel, upholstery textiles and bespoke rugs. Aulana® is a world first technology and product suite, which has attracted interest from UK, Italian and French fashion houses. The journey along this pathway, together with the nanoscience and nanotechnology are presented here.W need vitamin B and vitamin C every day for our growth, but if we take them in surplus/less amounts, our growth will be hampered. If these vitamins are taken into our body in encapsulated form, body takes these vitamins according to its requirements and the growth will be normal. Encapsulation of the vitamins is very important to protect these important biomolecules from external hazards, i.e., oxidation, sensitization, photolytic cleavage etc.; for the regulatory delivery of necessary amount of vitamin at the targeted site for a period of time efficiently and precisely and; to prevent overdose. In this work, encapsulation of β-cyclodextrin with two vitamins namely, nicotinic acid and ascorbic acid in aqueous medium have been explored by reliable spectroscopic, physicochemical and calorimetric methods as stabilizer, carrier and regulatory releaser of the guest molecules. Stereochemical nature of the inclusion complexes has been explained by 2D NMR spectroscopy. Surface tension and conductivity studies further support the inclusion process. Isothermal titration calorimetric studies have been performed to determine the stoichiometry, association constant and thermodynamic parameters with high accuracy. The outcomes reveal that there is a drop in ∆SO, which is overcome by higher negative value of ∆HO, making the overall inclusion process thermodynamically favorable. Hence, this exclusive study describes that the inclusion complexes can be used as controlled delivery systems in the field of modern biomedical sciences.The ethanolic extract of Vitex doniana stem bark (11.9g) was subjected to a silica gel accelerated column chromatography and eluents fractions (150ml aliquots) obtained were collected and monitored with thin layer chromatography (TLC).. Fractions with similar R f values from same solvents system were poled together. Phytochemical test of all the fractions were perform. Complete elution yielded 48 fractions (150ml/fraction) which were pooled to 24 fractions and finally to eight (8) eight fractions and coded. Fraction Vd 8-a (56mg) has gave a single spot a white crystal compound coded V 1 on checking with TLC and observed under Ultraviolet lamp .The R f values was calculated to be 0.433 and melting point was found to be 241-243°C uncorrected. The infra red spectrum of compound V 1 shows prominent peaks that corresponds to OHstr (3365cm-1) and C=0 (1652cm-1). The 1 H NMR (400 MHZ) spectrum of compound V 1 in DMSO-d6 displayed five singlet signals. It further showed a broad singlet at δ 5.58 integrated for 1 H is due to an olefinic H-atom adjacent to the carbonyl carbon atom. Three signals at δ 3.10` (d, J = 9.0 Hz, H-22), 3.59 (m, 1H, 2H-a) and 3.72 (m, 1H, 3H-e) each integrating for one proton is due to an oxymethine protons indicating that three oxymethine H-atoms were present in the compound. The 13 C-NMR spectrum showed the presence of 27 Carbon atoms, suggesting that may be steroid skeleton and The DEPT-135 spectra showed the presence of five CH 3 , eight CH 2 , and seven CH groups, and seven quaternary Catoms. The Molecular formula was established as C 27 H 44 O 7 by HRES-MS positive ion mode m/z 481.3179. Based on the spectral analysis, the compound V 1 is thus concluded to have ecdysteriod skeleton and conclusively conforms with 2β, 3β 14α, 20R, 22R, 25hexahydroxy-5 β cholest-7-ene-6one, commonly known as 20-hydroxyecdysone. This is the first time this compound was isolated from vitex doniana sweet.

Batch and continuous phosphate uptake studies employing a ferrimagnetic calcium silicate hydrate composite

Composite particles of ferrimagnetic magnetite and a nano-structured calcium silicate hydrate were synthesized and used for the sorption of phosphate from solution. The composite was very effective achieving phosphate uptakes of up to 5.5 mmol phosphate per gram of composite. The amount of phosphate sorbed depended on the ratio of silicate to magnetite in the composite as the silicate component was proven to be far more effective in the uptake than the iron oxide component. Although no definitive distinction was possible the uptake of phosphate appeared to follow second order kinetics and a Freundlich isotherm model. Continuous uptake studies were carried out which showed the importance of controlling the flow rate of liquid through a column containing the sorbent. While the attractive magnetic force kept the sorbent together for lower flow rates, at a high flow of feed solution sorbent material was lost into solution. The continuous uptake studies indicated furthermore that agglomeration limits the number of available active sorption sites and hence the effectiveness of the composite.