Synthesis, functionalisation and characterisation of germanium nanocrystals & their applications

In the last two decades, semiconductor nanocrystals have been the focus of intense research due to their size dependant optical and electrical properties. Much is now known about how to control their size, shape, composition and surface chemistry, allowing fine control of their photophysical and electronic properties. However, genuine concerns have been raised regarding the heavy metal content of these materials, which is toxic even at relatively low concentrations and may limit their wide scale use. These concerns have driven the development of heavy metal free alternatives. In recent years, germanium nanocrystals (Ge NCs) have emerged as environmentally friendlier alternatives to II-VI and IV-VI semiconductor materials as they are nontoxic, biocompatible and electrochemically stable. This thesis reports the synthesis and characterisation of Ge NCs and their application as fluorescence probes for the detection of metal ions. A room-temperature method for the synthesis of size monodisperse Ge NCs within inverse micelles is reported, with well-defined core diameters that may be tuned from 3.5 to 4.5 nm. The Ge NCs are chemically passivated with amine ligands, minimising surface oxidation while rendering the NCs dispersible in a range of polar solvents. Regulation of the Ge NCs size is achieved by variation of the ammonium salts used to form the micelles. A maximum quantum yield of 20% is shown for the nanocrystals, and a transition from primarily blue to green emission is observed as the NC diameter increases from 3.5 to 4.5 nm. A polydisperse sample with a mixed emission profile is prepared and separated by centrifugation into individual sized NCs which each showed blue and green emission only, with total suppression of other emission colours. A new, efficient one step synthesis of Ge NCs with in situ passivation and straightforward purification steps is also reported. Ge NCs are formed by co-reduction of a mixture of GeCl4 and n-butyltrichlorogermane; the latter is used both as a capping ligand and a germanium source. The surface-bound layer of butyl chains both chemically passivates and stabilises the Ge NCs. Optical spectroscopy confirmed that these NCs are in the strong quantum confinement regime, with significant involvement of surface species in exciton recombination processes. The PL QY is determined to be 37 %, one of the highest values reported for organically terminated Ge NCs. A synthetic method is developed to produce size monodisperse Ge NCs with modified surface chemistries bearing carboxylic acid, acetate, amine and epoxy functional groups. The effect of these different surface terminations on the optical properties of the NCs is also studied. Comparison of the emission properties of these Ge NCs showed that the wavelength position of the PL maxima could be moved from the UV to the blue/green by choice of the appropriate surface group. We also report the application of water-soluble Ge NCs as a fluorescent sensing platform for the fast, highly selective and sensitive detection of Fe3+ ions. The luminescence quenching mechanism is confirmed by lifetime and absorbance spectroscopies, while the applicability of this assay for detection of Fe3+ in real water samples is investigated and found to satisfy the US Environmental Protection Agency requirements for Fe3+ levels in drinkable water supplies.

Reductive ligation mediated one-step disulfide formation of S-nitrosothiols.

A one-step reductive ligation mediated disulfide formation of S-nitrosothiols was developed. This reaction involves the reaction of the S-nitroso group with phosphine-thioesters to form sulfenamide and thiolate intermediates, which then undergo a fast intermolecular disulfide formation to form stable conjugates. This reaction can be used to design new biosensors of S-nitrosated proteins.

Two steps forward, one step back: developing the curriculum for training teachers for technical and further education England 1945-1956

This paper discusses the development of provision for the training of teachers in English further and technical education from 1945 to 1956. While these years saw little growth in this provision, they were formative in that the institutional and curricular patterns of teacher training for the diverse fields of technical and further education were developed at this time. The work of the three national centres in Bolton, London and Huddersfield, during the period of the Emergency Training Scheme (ETS) is summarised with particular reference to the influence of the Ministry of Education‟s conditions for ETS colleges and courses. With the ending of the ETS in 1951 the three centres were given permanent status as teacher training colleges which in turn brought them into association with their local universities as constituent colleges of their Area Training Organisations. The consequences of this transfer to the universities for the curriculum and assessment of technical teacher training and the 'policy dichotomy' of teacher training for secondary and technical education are examined.

Development of a minor groove binder assay for real-time one-step RT-PCR detection of swine vesicular disease virus

The design and development of a 5' conjugated minor groove binder (MGB) probe real-time RT-PCR assay are described for rapid, sensitive and specific detection of swine vesicular disease virus (SVDV) RNA. The assay is designed to target the 2C gene of the SVDV genome and is capable of detecting 2 x 10(2) copies of an RNA standard per reaction. It does not detect any of the other RNA viruses that cause vesicular disease in pigs, or the human enterovirus, Coxsackie B5 virus (CVB5) which is closely related antigenically to SVDV. The linear range of this test was from 2 x 10(2) to 2 x 10(8) copies/mu l. The assay is rapid and can detect SVDV RNA in just over 3.5 h including the time required for nucleic acid extraction. The development of this assay provides a useful tool for the differential diagnosis of SVD or for the detection of SVDV in research applications. This study demonstrates the suitability of MGB probes as a real-time PCR chemistry for the diagnosis of swine vesicular disease. (C) 2010 Elsevier B.V. All rights reserved.

'Leptorapide' - a one-step assay for rapid diagnosis of human leptospirosis

Leptospirosis is a globally important zoonotic infection caused by spirochaetes of the genus Leptospira. It is transmitted to humans by direct contact with infected animals or indirectly via contaminated water. It is mainly a problem of the resource-poor developing countries of the tropical and sub-tropical regions of the world but outbreaks due to an increase in travel and recreational activities have been reported in developed and more industrialized areas of the world. Current methods of diagnosis are costly, time-consuming and require the use of specialized laboratory equipment and personnel. The purpose of this paper is to report the validation of the 'Leptorapide®' test (Linnodee Ltd, Northern Ireland) for the diagnosis of human leptospirosis. It is a simple one-step latex agglutination assay performed using equal volumes of serum sample and antigen-bound latex beads. Evidence of leptospiral antibodies is determined within minutes. Agglutination is scored on a scale of 1-5 and the results interpreted using a score card provided with the kit. Validation has been performed with a large sample size obtained from individuals originating from various parts of the world including Brazil and India. The test has shown sensitivity and specificity values of 97·1% and 94·0%, respectively, relative to the microscopic agglutination test. The results demonstrate that Leptorapide offers a cost-effective and accurate alternative to the more historical methods of antibody detection.

CONVENIENT ONE-POT SYNTHESIS OF HEXA-N-BUTYLDITIN FROM BIS(TRI-N-BUTYLTIN) OXIDE

Hexa-n-butylditin is prepared in high yield (83%), by reduction of bis(tri-n-butyltin) oxide with sodium borohydride in ethanol. The first stage is reduction. to tri-n-butyltin hydride (not isolated), which rapidly gives hexa-n-butylditin with the Loss of hydrogen under the basic reaction conditions.

Unusual framework stabilization of Cu(II) and Cu(I) ions in a novel copper-substituted aluminophosphate with AEN topology prepared by one pot synthesis

A novel copper-substituted aluminophosphate (CuIST-2) has been synthesized using methylamine as a templating agent. X-Ray diffraction studies provide evidence for an AEN topology similar to the parent Cu-free IST-2.

Simple and surprisingly effective one-step extraction-cleanup by Soxflo for DDT and its metabolites from environmental samples

A pilot study found that DDT breakdown at the GC inlet was extensive in extracts from some-but not all-samples with high organic carbon contents. However, DDT losses could be prevented with a one-step extraction-cleanup in the Soxflo instrument with dichloromethane and charcoal. This dry-column procedure took 1 h at room temperature. It was tested on spiked soil and peat samples and validated with certified soil and sediment reference materials. Spike recoveries from freshly spiked samples ranged from 79 to 111% at 20-4000 mug/kg concentrations. Recoveries from the real-world CRMs were 99.7-100.2% of DDT, 89.7-90.4% of DDD and 89.6-107.9% of DDE. It was concluded that charcoal cleanups should be used routinely during surveys for environmental DDX pollution in order to mitigate against unpredictable matrix-enhanced breakdown in the GC. (C) 2004 Elsevier B.V. All rights reserved.

One-pot synthesis of multivalent arrays of mannose mono- and disaccharides

The synthesis of a selection of multivalent arrays of mannose mono- and disaccharides, that are of potential use as anti-infective agents against enterobacteria infections, is described. (C) 2003 Elsevier Ltd. All rights reserved.

One-step catalytic cyclohexane oxidation to adipic acid using molecular oxygen

Using combination of Mn-Co transition metal species with N-hydroxyphthalimide as a catalyst for one-step oxidation of cyclohexane with molecular oxygen in acetic acid at 353 K can give more than 95% selectivity towards oxygenated products with adipic acid as a major product at a high conversion (ca. 78%). A turnover number of 74 for this partial oxidation are also recorded.