Pusat Pengajian Sains Kimia - Tesis

Browse

Recent Submissions

Now showing 1 - 5 of 473
  • Thumbnail Image
    Publication
    Kinetics Improvement Of Lithium Aluminium Hydride And 9- Ethylcarbazole Complex For Hydrogen Storage
    (2025-08)
    Liu, Huilin
    Hydrogen storage remains a critical bottleneck in the realization of a sustainable hydrogen economy. Lithium aluminum hydride (LiAlH4) and 9- ethylcarbazole (NCZ) are two promising hydrogen storage materials due to their high theoretical hydrogen capacities. However, their practical applications are limited by the poor reversibility of LiAlH4 and the sluggish (de)hydrogenation kinetics of NCZ. In this work, a novel composite system composed of LiAlH4 and NCZ in a 1:1 molar ratio (denoted as LA–NCZ) was synthesized and investigated. The composite exhibited a synergistic enhancement in hydrogen storage behavior: NCZ significantly reduced the dehydrogenation temperature of LiAlH4, enabling rapid dehydrogenation in a narrow temperature window between 150 °C and 160 °C. Differential scanning calorimetry (DSC) revealed dehydrogenation peaks at lower temperatures compared to pristine LiAlH4, and Kissinger analysis yielded significantly reduced apparent activation energies of 36.76 ± 1.33 kJ/mol and 83.11 ± 2.87 kJ/mol for the first and second steps, respectively. Interestingly, the dehydrogenation products of LiAlH4 (LiH and Al) further promoted the hydrogenation rate and selectivity of NCZ, achieving a hydrogen uptake of 5.6 wt% under 90 °C and 70 bar H2 with 5 wt% Ru catalyst, close to the theoretical value of fully hydrogenated NCZ.
  • Thumbnail Image
    Publication
    Catalytic Dehydrogenation Of Hydrazine Borane Over Cu@Ni/Moo3 Core Shell Catalyst For Hydrogen Storage Application
    (2025-08)
    Lei, Yunfeng
    Hydrogen energy is a promising clean energy source, and efficient hydrogen storage remains a critical challenge. Hydrazine borane (N2H4BH3, HB), with a high hydrogen content of 15.4 wt%, has attracted attention as a potential chemical hydrogen storage material. However, conventional methanolysis reactions typically utilize only the BH3 moiety, limiting hydrogen release. In this study, we developed a highly efficient MoO3-supported copper–nickel core–shell catalyst (Cu@Ni/MoO3) to enable complete hydrogen release from both the BH3 and N2H4 moieties. At 50 °C, the system achieved a yield of 5.5 moles of gas, the highest reported for HB methanolysis under mild conditions. Kinetic studies showed a low activation energy of 36.5 ± 3.5 kJ/mol for the second dehydrogenation step, indicating rapid hydrogen evolution at relatively low temperatures.
  • Thumbnail Image
    Publication
    Synthesis, Characterization, And In Vitro Anticancer Activities Of Benzyl-Functionalized Benzimidazolium Salts And Their Silver(I)-N-Heterocyclic Carbene Complexes
    (2025-09)
    Wong, Choon Hoe
    Cancer remains a persistent global health challenge, necessitating innovative therapeutic agents. Metal-based drugs, particularly those with silver(i) ions, are promising due to their high reactivity and ability to form stable complexes with biological molecules, offering potential advantages over traditional treatments. Current chemotherapeutic drugs often cause severe toxicity and suffer drug resistance, which drives the development of new compounds with improved efficacy and selectivity. In this study, two new series of unsymmetrical benzyl-functionalized and their silver(i)-n-heterocyclic carbene (nhc) complexes were prepared. The benzimidazolium salts, c2-c11, were prepared via n-alkylation of 1-decylbenzimidazole with benzyl or substituted benzyl bromides, followed by in situ deprotonation with silver(i) oxide (ag2o) and a metathesis reaction with potassium hexafluorophosphate (kpf6) to yield silver(i)-nhc complexes, c12-c21. These compounds were characterized using fourier-transform infrared (ft-ir) spectroscopy and fourier-transform nuclear magnetic resonance (ft-nmr) spectroscopy, liquid chromatography mass spectrometry (lc-ms), ultra-performance liquid chromatography mass spectrometry (uplc-ms), and chn elemental analysis. Their in vitro cytotoxicity was evaluated against human cervical cancer (hela) and breast cancer (mcf-7) cells, as well as normal skin fibroblast (hs27) were evaluated via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (mtt) assay.
  • Thumbnail Image
    Publication
    Chemical Characterisation, Enantioselective Profiling And Bioactivites Of Malaysian Citrus Spp. Leaf Extracts
    (2025-08)
    Al Othman, Haneen Ibrahim Ahmad
    Authentication and quality control of Citrus essential oils remain challenging due to their complex chemical composition, the presence of trace adulterants, and the lack of robust analytical methodologies. While Citrus-derived peel essential oils are widely recognized for their therapeutic and medicinal applications, systematic characterization of leaf-derived Citrus spp. essential oils rand their bioactivity remains underexplored. This study examined the volatile constituents of essential oil distilled from the leaves of Malaysian C. hystrix, C. limon, C. pyriformis, and C. microcarpa, using gas chromatography–quadrupole mass spectrometry. Additionally, headspace solid-phase microextraction (HS-SPME) was used to profile the biogenic volatile organic compounds emitted from the freshly collected leaves of these four Citrus spp. to allow near-real-time measurement of leaf volatiles without physicochemical stress.
  • Thumbnail Image
    Publication
    Anti-Diabetic Activity Of Chemical Constituents Isolated From Kopsia Teoi And Catharanthus Roseus (Apocynaceae), And Corrosion Inhibition Studies Of Its Extracts
    (2025-05)
    Jaf, Muhammad Tahir Muhammad Al
    This research involved extracting dried ground bark from kopsia teoi (k. Teoi) and catharanthus roseus (c. Roseus) using n-hexane, dichloromethane (dcm), and methanol (meoh) solvents to produce the crude extracts. Alkaloids were isolated from dragendorff-positive dcm extracts via acid-base extraction with hcl and nh4oh, yielding a dcm alkaloid extract. Fractionation by cc and analysis by tlc led to further purification, isolating alkaloids. From k. Teoi, ten compounds were isolated, including four new compounds: 16-epi-deacetylakuammiline n(4)-methylene chloride (602), n(1)-methoxycarbonyl-11-methoxy-12-hydroxy-δ14‒17-kopsinine (603), n(1)-methoxycarbonyl-11,12-methylenedioxy-δ14‒17-kopsinine (604), and n(4)-hydroxymethyl-kopsinine (605). Additionally, known compounds were isolated, including leuconolam (301), kopsiloscine g (413), e-akuammidine (132), n(1)-methoxycarbonyl-12-methoxy-δ16,17-kopsinine (302), kopsininate (312), and n(1)-methoxycarbonyl-11,12-methylenedioxy-δ16,17-kopsinine (383). Meanwhile, from c. Roseus, five compounds were isolated, including one new compound: 16-epi-deacetylakuammiline-7-methyl-n(4)-methylene chloride (606), and four known compounds, namely: β-amyrin (590), ursolic acid (591), dodecanoic acid (596), and oleic acid (598). The isolated compounds were characterised using ft-ir (atr), 1d- and 2d- nmr, uv spectroscopy, and high-resolution electrospray ionisation mass spectroscopy (hresims), with comparison to literatures data.