Pusat Pengajian Sains Kimia - Tesis
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- PublicationSynthesis, Characterisation And Determination Of Mesophase Transition Of Cyclotriphosphazene Derivatives With Azo Linking Unit(2017-07)Loh, Miyeko Lotus Leh ChiingA series of intermediates were synthesised via azo coupling reactions to give the alkylated compounds with one azo linking unit, 2a-c and with two azo linking units, 5a-c. These intermediates were subjected to further monosubstitution and hexasubstitution reactions with cyclotriphosphazene to produce a series of final compounds 7a-f. These compounds were characterised using FT-IR (Fourier Transform Infrared), 1D and 2D NMR (Nuclear Magnetic Resonance) spectros copy and CHN elemental analysis. Intermediates 2d-f and 4a-c were found to be mesogenic with nematic and smectic phases, as determined under the POM (Polarised Optical Microscopy). The endotherms obtained from the DSC (Differential Scanning Calorimetry) showed the respective phase transitions of crystal-mesophase, mesophase-mesophase if any, and mesophase-isotropic phases during the heating cycle; and vice versa during the cooling cycle. The influence of terminal groups and linking groups on mesogenic properties was discussed.
- PublicationIdentification Of parS In Megaplasmid pHG1 Of Cupriavidus Necator H16(2018-10)Pow, Kah CheeThe active partitioning system (ParABS system) that coordinates the migration of plasmid replicons to two separate poles is consist of three elements, ParA, ParB and parS. In the megaplasmid pHG1 of Cupriavidus necator H16, the ParA and ParB had been annotated while the ParB-binding parS remained unknown. This study aims to identify the position ofparS in the megaplasmid pI-IG 1. Bioinformatic analysis shows that ParB has a conserved I-ITH motif which is a determinative characteristic of type la active partitioning system. This led to the hypothesis that the parS ofpHG 1 is located downstream of the par operon where two palindromes, Pld_l and Pld_2, were identified and determined as the probable parS candidates. However, the sequences of the palindromes as well as the sequence of defined PAR region (consisting par operon) showed no significant similarity to any of the eight parS consensus when aligned. This suggest that pHG 1 parS could be a new parS consensus representing an unknown subset of ParABS system. Aside of the PAR region, another parS was also hypothesised to reside in ORI region (the immediate upstream of PAR region). To support this hypothesis, a parS-ParB binding assay was conducted to detect the ParB binding activity in region PAR and region ORI.
- PublicationSynthesis Of Silicoaluminophosphate Zeolite Catalysts Directed By Benzyltrimethylammonium Hydroxide Template For The Chemical Production Of Biofuel Additives(2025-08)Wang, GuanchenSilicoaluminophosphate (SAPO) zeolites are very useful catalysts. Usually, they are synthesized with aliphatic quaternary ammonium compounds as organic template. However, benzyltrimethylammonium hydroxide (BTMAOH) containing cyclic functional group as a template has not been studied. Here, the crystallization of SAPO-34 and SAPO-20 zeolites using BTMAOH is studied by following their evolutional formation. The BTMA+ has shown its effective structure-directing and pore-filling roles whereby pure SAPO-34 and SAPO-20 with unique surface properties (surface area, porosity, acidity) are formed after 24 and 42 h at 180 °C. Compared with SAPO-20, SAPO-34 with larger pore size exhibits better catalytic activity (conversion 100%, ethyl levulinate (EL) yield 72.5%) in microwave-assisted furfuryl alcohol (FA) ethanolysis. The spent SAPO-34 catalyst is stable and recyclable, offering it as a cost-effective catalyst for various petrochemical reactions. This work also studies the preparation of hierarchical SAPO-5 using various surfactants, namely dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (TP), hexadecyltrimethylammonium bromide (CTA) and hexadecylpyridinium chloride (CP). The results show that these ionic compounds experience interactions with inorganic reagents during crystallization, which in turn altering the morphological (crystal size and shape) and structural (porosity and acidity) properties of SAPO-5. Among hierarchical SAPO-5 samples, TP-SAPO-5 with the highest hierarchical factor (HF = 0.074) and second highest acidity (0.73 mmol·g-1) is the best catalyst for producing ethyl pyruvate (EP) via esterification. After parametric optimization, its performance (conversion 92.0%, selectivity 85.9%) is comparable to homogeneous HCl and H2SO4 catalysts (conversion 88-92%, selectivity 84-92%) and much superior than H-Y, H-MOR, SAPO-34 zeolites (conversion 56-100%, selectivity 67-76%). The hierarchical TP-SAPO-5 is also reusable for up to five reaction cycles, making it as a green and excellent catalyst for biomass product conversion.
- PublicationSynthesis And Mechanistic Study Of Heterojunction Biobr-Based Composites For Antibiotics Photodegradation(2025-08)Sun, YanliPhotocatalysis based on semiconductors has garnered increasing attention due to its potential to utilize solar energy and applications in environmental remediation. Recently, BiOBr has emerged as a promising candidate owing to its non-toxicity, low cost, and distinctive physicochemical properties. However, the fast recombination of electron-hole (e-/h+) pairs in these materials often limits its practical applications. This study aims to explore BiOBr-based semiconductors for the degradation of various antibiotics under visible light. First, two pristine BiOBr photocatalysts (BiOBr-W and BiOBr-EG) were first synthesized using water and ethylene glycol, respectively.
- PublicationKaedah Penyimenan Galvani Untuk Memendakkan Emas Dari Larutan Sianida Pada Grafit(1996-06)Ngah, Che Wan Zanariah Che WanPemulihan emas dari larutan konvensional emas-sianida dengan kaedah penyimenan galvani menggunakan grafit poros sebagai katod dan logam zink sebagai anod akan dihurai. Membran pertukaran kation raipore RAI-4010 digunakan untuk mengelakkan percampuran di antara anolit dan katolit serta litar pintas ion-ion dalam larutan. Eksperimen dilakukan dalam sistem berkelompok (batch system) untuk melihat kecekapan pemulihan emas secara penyimenan galvani. Keputusan yang diperolehi menunjukkan kaedah iru berupaya memulihkan lebih 99% daripada emas dari larutan konvensional emas-sianida yang telah disediakan secara sintetik. Kemuatan awal emas pada grafit dan perubahan ph larutan katolit didapati tidak mempengaruhi peratus pemulihan emas dengan kaedah ini. Manakala kepekatan spesies ion-ion emas, sianida dan kalsium di dalam katolit pula didapati meningkatkan peratus pemulihan emas secara penyimenan galvani ini.