https://repository.sustech.edu/handle/123456789/1222 Sun, 05 Apr 2026 16:27:21 GMT 2026-04-05T16:27:21Z http://repository.sustech.edu:80/jspui/retrieve/a8bdc616-5b6d-4519-8b78-100b9f728a0f/ https://repository.sustech.edu/handle/123456789/1222 https://repository.sustech.edu/handle/123456789/2382 Title: Photobleaching of anthocyanins using tunable dye laser Authors: Ahmed,Wafa Omer; Supervisor, - Ahmed Hassan S. Elkheir Abstract: The flowers of Hibiscus sabdarifa were extracted with acidified methanol. The Anthocyanin of Hibiscus sabdarifa was obtained as red needles from absolute ethanol. A dye laser operating at 520 nm was used to bleach the red- colored anthocyanin. A mixture of the anthocyanin and triethylamine was irradiated with laser for 40 minutes. Under such conditions the iv ‫‪The anthocyanin then oxidizes triethylamine and reduces to a colourless‬‬ ‫.‪radical‬‬ ‫‪AS‬‬ ‫1‬ ‫*‪AS‬‬ ‫3‬ ‫‪hν‬‬ ‫0‪AS‬‬ ‫1*‬ ‫)‪(Red‬‬ ‫3*‪AS• + •NR‬‬ ‫3‬ ‫3‪AS* +:NR‬‬ ‫)‪(Colourless‬‬ ‫‬ Description: Thesis Fri, 01 Aug 2008 00:00:00 GMT https://repository.sustech.edu/handle/123456789/2382 2008-08-01T00:00:00Z https://repository.sustech.edu/handle/123456789/28150 Title: Detection of Heavy Metals Contents in Sudanese Cement Using Laser Induced Breakdown Spectroscopy Technique Authors: Abdalgader, Altaf Alsaid Mohamed; Supervisor, -Abdelmoneim M. Awadelgied Abstract: In this work, Laser Induced Breakdown Spectroscopy (LIBS) was used to Investigate, and identify, the heavy metals in samples of cement collected from different local markets in Khartoum state. Four cement samples were used as study samples (Atbara, Barbar, Mas and Sakhr Al Sudan) cement. Optimal experimental conditions were evaluated using Nd: YAG laser in Q-switched mode with ability to deliver maximum pulse energy of one joule with a pulse width of 8 ns and operating at a 10 Hz was employed for production of plasma spark at the sample surface. A convex lens having focal length 30 mm was used to focus Nd-YAG laser pulse onto the surface of sample at 266 nm. With pulse energy 30 mj. The spectrometer used was Ocean Optics LIBS 2000+ system. Our LIBS 2000+ has four spectrometers modules to provide high resolution (FWHM 0.1 nm) in the (200 to 620) nm wavelength region. The detector has a gated CCD camera having 14,336 pixels. This makes it possible to measure a LIBS spectrum over broad spectral range (200 to 620) nm simultaneously with high spectral resolution (0.1 nm). The emission is observed at a 90° angle to the laser pulse. The recorded spectra of the samples were analyzed using NIST data. The analysis of the spectra showed considerable amounts of neutral atoms like (Ca, Fe, Si, Na, Ti, Cr, V, Sr, Zr, Kr, K and Cs) that were found in all samples. In addition to the ions: (Ca+1, Fe+, Si+1, Na+1, Ti+1, Cr+1, and K+1). The heavy metals like: metals (Cr, Fe, Ti, Mn, V, Xe, Y and Zn) were appeared in the four samples with nearly amounts, they are toxic metals harmful to human and environment. To identify the relationship between the laser pulsed energy and the intensity of the LIBS signal, the Mas cement sample was irradiated by different pulse laser V energies (10, 15, 20, 25, 30 and 32) mJ .respectively and 200 ns delay time. We observed when the laser pulse energy increase the line intensity was increase. LIBS were applied for the determination of plasma temperature and electron density of Cr in Mas cement sample. The plasma temperature and electron density were calculated at (10, 20, 25 and 30) mJ laser pulse energy using standard equations and well resolved spectral lines in the (428.97 ,430.117,435.17,and 435.96) nm region. These parameters were found to increase with increase in laser pulse energy. The Boltzmann distribution and experimentally measured line intensities support the assumption that the laser-induced plasma was in local thermal equilibrium. To identify the relationship between the laser delay time and the intensity of the LIBS signal, the Mas cement sample was irradiated by 32mj laser pulse energy and (200,300,400 ,500, 600, 700, 800, 1000, and 2000) ns delay times. We observed LIBS signal decreases with increase in laser delay times. The plasma temperature and electron density were calculated at (300,500, and 700) ns laser delay time at 32mj laser pulse energy using standard equations and well resolved spectral lines of Ca in the (422.67, 430.25and 430.774) nm region. It was observed that when the delay time increases the plasma temperature and electron density were decreased. Then the electron density increased with increased in plasma temperature. Description: Thesis Tue, 21 Jun 2022 00:00:00 GMT https://repository.sustech.edu/handle/123456789/28150 2022-06-21T00:00:00Z https://repository.sustech.edu/handle/123456789/27784 Title: Spectroscopic Variability and Optical Properties of Sudanese Edible Oils Using Spectroscopy Methods Authors: Banaga, Mahasin Mohamed Daffalla; Supervisor, - Abul Moneim. M. Awad elgied Abstract: In this study, nondestructive test was applied on six types of edible oils (corn, extra virgin olive, sunflower, pressed sesame, factory sesame and peanuts) using spectroscopic methods. Raman spectroscopy and Fourier infrared spectroscopy were carried out to identify functional groups presence on oils while ultraviolet visible was used to study optical properties of edible oils. From Raman spectra of edible oils samples, the major bands can be found at (1084, 1266, 1303, 1441, 1657, 1749,) cm−1 . It is of particularly significance for edible oils that stretching of C=C bonds gave rise to strong Raman signals and C=O stretching bands were very weak; the contrary can be found in infrared spectra. FTIR spectrum of all samples in range from (400-4000) cm-1 . From comparison of IR and Raman spectra of edible oil samples, the frequencies of some characteristic peaks were identical, while the relative intensities differed markedly. On the contrary, Raman scattering signal at (560, 969) cm−1 was quite weak, but corresponding infrared absorption peak was obvious. The general appearance of the IR spectra of these vegetable oils was found to be very similar to a previously reported study. In the Raman spectrum, the spectrum of peanut and presses sesame differed from the previous studies. Thus, the combination of these two different methods has been very useful in the study of the oil which provides comprehensive information about the chemical compositions of edible oils. FTIR spectral data collected in MIR range 4000-400 cm-1 showed major peaks representing triglyceride functional groups which could be observed around 2925 cm-1 [C–H stretching (asymmetry)], 2854 cm-1 iv [C– H stretching (symmetry)], 1747 cm-1 [C=O stretching], 1463 cm-1 [C–H bending (scissoring)], 1238, 1163, 1118 and 1097 cm-1 [C–O stretching] and 722 cm-1 [C–H bending (rocking)]. A peak around 1653 cm-1 is attributed to C=C stretching (cis). A band shift at 3007 cm-1 ; assigned to C–H stretching vibration of cis- double bond (=C–H) characteristic to samples oils. The absorption spectrum of six important Sudanese oils can be divided into three main absorption regions the first region is from the beginning of the spectrum to 340 nm, the second region is (400 - 500) nm and the last region is from (600-800) nm. The shift in absorption peaks of these oils refer to different chemical group that oils contain. Absorption coefficient and refractive index of all oils under study were different because structure components of each oil were different and this confirm with Raman and FTIR results. High values of the absorption coefficient indicate the possibility of direct electronic transitions between the valence and conduction bands at these energies. Description: Thesis Fri, 22 Apr 2022 00:00:00 GMT https://repository.sustech.edu/handle/123456789/27784 2022-04-22T00:00:00Z https://repository.sustech.edu/handle/123456789/27700 Title: Evaluation of the Quality Parameters for Some Laser-Irradiated Edible Oils Authors: Mudawi, Alaa Ahmed Mohammed; Supervisor, -Ali Abdel-Rahman SaeedMarouf Abstract: This work focuses on the laser food irradiation; mainly on investigating of the influence of green laser (532nm) radiation on some physicochemical properties of sesame oil before and after storage period of 15 consecutive days, and the effect of heating and reheating on sunflower oil properties using carbon dioxide laser compared with the electrical heater was also studied. The samples of sesame oil were irradiated using diode laser beam with wavelength 532nm and 1 W output power, to duration times of 10, 20, 30, 40, 50 and 60 minutes, and kept for a storage period of 15 consecutive days along with an untreated control at ambient conditions. While two samples of sunflower oil were heated and twice heated with carbon dioxide laser beam up to 50c it takes 30 minutes; another two samples of sunflower oil were heated and twice heated up to 250c using electrical heater in two minutes, along with an unheated control sample at ambient conditions. Physicochemical properties like acid value, ester value, free fatty acids, peroxide value, density, refractive index, viscosity, and moisture of sesame oil and of sunflower oil samples were studied. Fourier transform infrared spectroscopy was used to evaluate the degree of oxidation after irradiation processes of sesame oil and sunflower to differentiate between the chemical changes in the oil samples. The properties of sesame oil were compared at the 1st and 15th day of storage. Color measurements of sunflower oil samples were studied too. Study reveals that green laser irradiation increases ester value, saponification value, acid value, free fatty acids, peroxide value, viscosity and moisture content of sesame oil; while, it slightly change refractive index and density. Study also indicates that the storage period of 15 days decreases the ester value, saponification value, and moisture content; while, it accelerate acid value, free fatty acid, peroxide value, density viscosity, and slightly increases the refractive index. Meanwhile, FTIR spectra of the stored samples revealed a notable difference due to the green laser irradiation and storage. The results also, demonstrated that when the same sunflower oil is reheated, the chemical reactions enhance foaming, darkening of oil color, increased viscosity, and off-flavor. Hence, repeated heating of the oil can lead to degradation of the cooking oil, both chemically and physically. These results suggest that exposing sesame oil to the green laser irradiation influences their oxidation stability and quality. It was also found that the long time of heating using laser rising temperature up to 50°c catalyzed chemical reactions that resulted in effects in the oil samples characteristics greater than the effects of the electrical heater in a few minutes with temperature 250°c. Description: Thesis Wed, 12 Jan 2022 00:00:00 GMT https://repository.sustech.edu/handle/123456789/27700 2022-01-12T00:00:00Z