Browsing by Author "Loyce, Namanya"

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Biomarker Raman bands of estradiol, follicle-stimulating, luteinizing, and progesterone hormones in blood
(Vibrational Spectroscopy, 2022-08) Annah, M. Ondieki; Zephania, Birech; Kenneth, A. Kaduki; Catherine, K. Kaingu; Anne, N. Ndeke; Loyce, Namanya
Variation of the levels of reproductive hormones outside the normal range indicates health problems that include cancer, infertility, and menstrual difficulties. This work reports on a potentially novel method of screening four (estradiol, follicle-stimulating hormone, FSH; luteinizing hormone, LH; and progesterone) hormones. The work involved first determining the characteristic Raman spectra of their standards. Thereafter, the Raman marker bands of the respective hormones in blood were determined experimentally. Simulate samples were prepared by mixing, at varying concentrations, the respective standard hormone samples with male mouse’s blood and concentration-sensitive Raman bands identified upon 785 nm laser excitation. The samples were applied, separately, onto prepared conductive silver paste smeared microscope glass slides. Spectral data analyses were done using both Principal Component Analysis (PCA) and Analysis of variance (ANOVA). The spectral profiles of respective standard hormones (with no blood) displayed common bands at 483, 1005, 1244, and 1455 cm−1 which were tentatively attributed to C-C stretching of glucose, lipid bands, and CH2/CH3 scissoring respectively. Other bands were observed at 542 cm−1 (for LH and progesterone), 859 cm−1 (for estradiol and FSH), 837 cm−1 (for FSH and LH) and at 1360 cm−1 (for progesterone). In blood, a large comparative Raman spectral intensity variation was observed at around 483 and 1450 cm−1 in LH; 902 and 1569 cm−1 in estradiol. These bands could be used as biomarker Raman bands for the respective hormones. The bands centered at 668 and 1219 cm−1 displayed almost identical intensity variation in the four hormones (estradiol, FSH, LH, and progesterone) and could be used as marker bands for level determination for the four combined. This work has shown the power of Raman spectroscopy in potential hormone concentration level determination when respective biomarker bands are employed.
Co-sensitization effect of chlorophyll and anthocyanin on optical absorption properties and power conversion efficiency of dye-sensitized solar cells
(Springer, 2024-04) Mukhokosi, Emma Panzi; Mohammed, Tibenkana; Loyce, Namanya; Botha, Nandipha L.; Maaza, Maliki; Velauthapillai, Dhayalan
In this article, the chemical structure, optical absorption and photoluminescence properties of un/adsorbed dyes of hibiscus flower (H), pumpkin leaf (P), sweet potato leaf (S) and their composites (H: P & H: S) have been studied. The chemical structural properties revealed the O–H, C–C and C = O as the main anchoring functional groups. The optical absorption properties revealed two definite bands in between 450–500 nm and 600–680 nm wavelength for chlorophyll-based dyes and a peak at 526 nm for anthocyanin based dye extract. The composite dye extracts revealed optical absorption bands corresponding to chlorophyll and anthocyanin pigments with enhanced absorption of light. Five different solar cells based on H, P, S, H:P-3:1 and H:S-3:1 were developed and revealed an efficiency of ~ 0.08, 0.3, 0.5, 0.7 and ~ 1% respectively. The efficiency was reduced by half after 30 days. The composites had the highest power conversion efficiency due to more O–H, C–C and C = O binding sites on TiO2 nanoparticles, reduced rate of electron–hole pair recombination and a wide range of optical absorption. These studies suggest that co-pigmentation can be an alternative strategy to increasing the power conversion efficiency in DSSCs.
Optical absorption and photoluminescence properties of Cucurbita maxima dye adsorption on TiO2 nanoparticles
(IOP Publishing Materials Research Express, 2023-04) Emma, Panzi Mukhokosi; Maliki, Maaza; Muhammed, Tibenkana; Nandipha, L Botha; Loyce, Namanya; Madiba, I G; Michael, Okullo
Dye-sensitised solar cells (DSSCs) are 3rd generation photovoltaic device that imitate photosynthesis in plants. The fundamental concept of a DSSCs is that the photoanode is covered by the dye as a sensitiser. Natural dyes from plant-based extracts have gained attention as alternatives to toxic and expensive commercial dye sensitisers. Various studies have been conducted on the use of natural plant dye extracts for DSSCs . However, more fundamental studies on their adsorption on TiO2 photoanode nanoparticles are still not well understood. In this study, we investigated the crystal structure, optical absorption, and photoluminescence properties of TiO2, Cucurbita maxima, and Cucurbita maxima dyes adsorbed on TiO2 nanoparticles as potential materials for DSSCs. Raman spectra confirmed the anatase phase of the TiO2 nanoparticles. The particle size of 12 ± 2 nm was confirmed through the transmission electron microscope. The optical absorption properties of Cucurbita maxima show two distinct absorption bands: blue visible (450–500 nm) and red visible (635–674 nm). The photoluminescence spectra of the dye extract and its adsorption onto the TiO2 nanoparticles showed two prominent peaks in the blue and red regions of the electromagnetic spectrum. No significant peak is observed in the green region of the electromagnetic spectrum. These studies shed more light on the fundamental properties of chlorophyll adsorption on TiO2 nanoparticles and their optical and photoluminescence properties for applications as sensitisers in DSSCs.