Robert James Eldridge

Adsorption characteristics of arsenic(III) and arsenic(V) on iron(III)-loaded chelating resin having lysine-Nα,Nα-diacetic acid moiety

Abstract An iron(III)-loaded chelating resin (Fe-LDA) with lysine-N α ,N α -diacetic acid functional groups has been prepared and its adsorption characteristics for arsenic(III) and arsenic(V) have been examined. Arsenic(V) was strongly adsorbed to the resin in the pH range from 2 to 4, while arsenic(III) was moderately adsorbed between pH 8 and 10. The isotherm data for arsenic(V) at pH 3.5 fitted well to a Langmuir equation with a very large binding constant of 7.2 × 10 4 dm 3 mol −1 and a capacity constant of 0.74 mmol g −1 The data for arsenic(III) at pH 9 also fitted to a Langmuir equation, with a binding constant of 190 dm 3 mol −1 and a capacity constant of 0.84 mmol g −1 . Regeneration of the resin was successfully carried out with 0.1 mol dm −3 sodium hydroxide solution. Both arsenic compounds can be almost quantitatively recovered from the resin under these conditions. Only a small amount of ferric ions (less than 0.1 %) was observed to come off the resin during the regeneration with alkaline solutions. Since the Fe-LDA resin showed little affinity for arsenic(III) in acidic media, the present adsorption system can provide satisfactory separation of arsenic(V) from arsenic(III). Arsenic(V) was successfully concentrated in the column packed with Fe-LDA resin from its dilute solution.

Conjugation of Transferrin to Azide‐Modified CdSe/ZnS Core–Shell Quantum Dots using Cyclooctyne Click Chemistry

Twinkle twinkle quantum dot: Conjugation of biomolecules to azide-modified quantum dots (QDs) through a bifunctional linker, using strain-promoted azide-alkyne cycloaddition with the QD and a squaramide linkage to the biomolecule (see scheme). Transferrin-conjugated QDs were internalized by transferrin-receptor expressing HeLa cells.

Concentrated synthesis of metal nanoparticles in water

The synthesis of a range of metal nanoparticles (Ag, Au, Pd, Pt) in water through reduction from the acid soluble salt at abnormally high concentrations (>1 mol L−1) is demonstrated using a comb polymer of methoxypoly(ethylene glycol) acrylate and maleic anhydride (PEG-MA) as the particle stabiliser during particle formation. The results show that at high concentrations in water, the general growth mechanism in these systems is through aggregation of nuclei of an approximate diameter of 0.6 nm. Aggregation resulted in formation of single crystals up to a particle diameter of approximately 5 nm but thereafter, further aggregation resulted in polygonal twinned particles. Continued aggregation caused agglomerate particles to be formed at larger sizes (>30 nm). Stabiliser adsorption was found to be critical to size control whereby the aggregation process was interrupted, preventing further growth. A case of the synthesis of Ag nanoparticles with a mean size of 8 nm at concentrations of up to 2.5 mol L−1 is elaborated.

Concentrated aqueous synthesis of nanoparticles using comb-graft copolymer stabilisers: the effect of stabiliser architecture

Silver nanoparticles have been synthesised at high concentration (>1 mol L−1) in water using a series of comb-graft copolymers. The copolymers were synthesised and then derivatised from methoxypoly(ethylene glycol) acrylate and maleic anhydride. The degree of polymerisation (number of backbone units), the nature of the adsorption group and length (MW) of the steric component were all found to be critical to the stabilisation of the nanoparticles during synthesis. The results demonstrate that a minimum steric length is required to prevent particle aggregation during synthesis. For Ag particles less than 30 nm in diameter, this corresponded to a polyethylene glycol (PEG) chain with a molecular weight of 454 g mol−1. It was shown that stabiliser molecules with a low number of backbone units were readily displaced, whereas stabilisers that possess numerous adsorption groups bind irreversibly to the particle surface. Adsorption groups were modified to test both chemisorption and physisorption functionality. Chemisorbed species were shown to be more effective stabilisers whereby concentrated Ag nanoparticles were synthesised at a smaller particle size. This was attributed to the adsorption strength and greater diffusive capabilities of the molecule.