Mbuso Mlambo

Qualitative analysis of some alkanethiols on Au nanoparticles during SERS

The surface enhanced Raman spectroscopy enhancement factors (SERS EFs) for different AuNP–surfactant systems are measured and the observed trend is theoretically and qualitatively investigated. Four thiolated coumarin derivatives (HS–(CH2)11–NHCO–coumarin, HS–(CH2)11–NHCO–indole, HS–(CH2)11–triphenylimidazole and HS–(CH2)11–hydroquinone respectively) together with a stabilizing surfactant, HS–(CH2)11–PEG-COOH, were adsorbed in ratios of 1% and 50% onto different sized Au nanoparticles. Similar simulation experiments were done to determine the influence of the nanoparticle–surfactant binding energy (Eb) on SERS EFs. Other parameters that were qualitatively investigated were the dependency of the Raman enhancement on (a) the size of Au nanoparticles, (b) the relative surface-to-molecule orientation, (c) the molecular orbitals (HOMOs and LUMOs), (d) the molecule electro-and nucleophilic centres and cross-sectional areas as well as (e) the molecular electrostatic potentials. It was observed that each of these parameters contribute to the observed trend and the final Raman signal enhancement.

Google Analytics and quick response for advancement of gold nanoparticle-based dual lateral flow immunoassay for malaria – Plasmodium lactate dehydrogenase (pLDH)

A rapid dual lateral flow diagnostic assay fabricated with quick response (QR) barcodes was developed to improve the quality control of malaria diagnostic tests, as well as to enhance systems for transferring data from survey studies among community healthcare workers at a point-of-care facility and centralized laboratories. The lateral flow kit has been modified with QR technology encoded with Google Analytics information for the detection and real-time tracking of Plasmodium lactate dehydrogenase (pLDH). The QR barcode was fabricated by attaching two QR barcodes which were encoded with websites that were linked to Google Analytics. The optical and structural properties of gold nanoparticles (AuNPs) were studied using UV-visible spectroscopy, transmission electron microscopy and a Biodot XYZ. The anti-mouse IgG antibody was used as a secondary antibody to act as a control and anti-pLDH. The antibody binding with pLDH antigens shows a test line indicating a positive test in the presence of phosphate buffer as a mobile phase. The diagnostic kit for the rapid detection of pLDH was developed and validated for the detection of malaria antigens at the lowest detectable recombinant concentration of 10 ng ml−1. The diagnostic kit was incorporated with quick QR barcodes for positive, negative and invalid tests readable with a smartphone. These QR barcodes successfully allowed us to track the precise location of the test through Google Analytics.

Comparative study of the effect of swift heavy ion irradiation at 500 °C and annealing at 500 °C on implanted silicon carbide

Transmission electron microscopy (TEM), Raman spectroscopy and Rutherford Backscattering Spectrometry (RBS) were used to characterize polycrystalline SiC specimens individually implanted with 360 keV I+ or Kr+ ions at room temperature and thereafter either irradiated with 167 MeV Xe to a fluence of 5 × 1013 cm−2 at 500 °C or annealed at 500 °C under vacuum. Implantation of I and Kr resulted in an amorphous layer about 196 and 230 nm from the surface respectively. Randomly oriented SiC nanocrystallites nucleated and grew within the layer after both treatments. These nanocrystallites were more pronounced on the SHI irradiated at 500 °C as compared to the annealed samples. Raman results supported these observations. No diffusion or redistribution of the implanted ion species could be detected by RBS.