Syarifah Abd Rahim

Nucleation Kinetics of Carbamazepine-Saccharin (CBZ-SAC) Co-crystal

In this study the effect of the heating/cooling rate of various CBZ-SAC mixture in ethanol was investigated in order to deduce the metastable zone width (MSZW) and the nucleation order. Nývlt’s equation involving the maximum temperature difference \(\varDelta T_{ \hbox{max} }\) between dissolution and crystallization temperatures of CBZ-SAC co-crystals with the heating/cooling rate r was applied for the study of nucleation kinetics by the polythermal method. A step towards the determination of dissolution temperature of the crystals has been improved. The results showed that dissolution temperature for CBZ-SAC co-crystal mixture increased with the increase in heating rate, CBZ-concentration and the ratio of SAC to CBZ in ethanol solution. The analysis revealed that a nucleation order for CBZ-SAC co-crystals increases with the SAC to CBZ ratio and is in the range of 1.58–6.31.

Solubility of carbamazepine co-crystals in ethanolic solution

The study aimed to determine the solubility of carbamazepine (CBZ) co-crystals formed from co-crystal formers (CCFs) of nicotinamide (NIC), saccharin (SAC), succinic acid (SUC) and fumaric acid (FUM) at various temperatures (25-50°C). High Performance Liquid Chromatography (HPLC) was used to determine the solubility and the X-Ray Powder Diffraction was used to characterize the crystals. The solubility of CBZ-NIC and CBZ-FUM co-crystals were found to be higher than the solubility of the CBZ for the range of studied temperatures. However, opposite findings was obtained for CBZ-SUC co-crystal as its solubility is lower than the solubility of CBZ. Different trend was found for CBZ-SAC co-crystal in which for temperature lower than 40°C, the solubility of CBZ crystal is higher than the CBZSAC co-crystal. The solubility of CBZ-SAC co-crystal is higher than the solubility of CBZ at a temperature above 40°C. CBZ co-crystals with NIC and FUM have shown to increase the solubility of CBZ by solubility ratio of 1.95 and 1.24 respectively. However, the CBZ co-crystal with SAC was found to have similar solubility value as the CBZ.

(CeO2-TiO2 untuk penurunan CO2 kepada metanol di bawah radiasi cahaya nampak: Kesan pemuatan ceria)

A visible light-driven photocatalyst, CeO2-TiO2 catalyst with different ceria loading was synthesized by impregnation method between TiO2 powder and cerium oxide nanoparticles slurry. The prepared catalyst samples were characterized by X-ray diffraction (XRD), surface area analysis, UV-vis absorption spectroscopy and photoluminescence spectroscopy (PL). The band gap of CeO2-TiO2 catalyst was found to be 2.15–2.4 eV. The band gap reduction clearly indicated the successful loading of CeO2 on TiO2. The photocatalytic activity was determined by measuring the photoreduction of CO2 to methanol in aqueous solution under visible light. The effect of cerium loading in the range of 1 to 5 wt% on the photocatalytic activity was studied and 2 wt% CeO2-TiO2 was found to exhibit the maximum photoactivity of 18.6 μmo l/g.catalyst after 6 hours irradiation. Results showed that the prepared photocatalyst is visible light active and may be used as effective catalyst in photoreduction of CO2 to methanol.