Rafizah Rahamathullah
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Preferred name
Rafizah Rahamathullah
Official Name
Rafizah, Rahamathullah
Alternative Name
Rahamathulla, Rafizah
Rahamathullah, R.
Main Affiliation
Scopus Author ID
55764144700
Researcher ID
DMZ-6313-2022

Research Output
Now showing 1 - 4 of 4
  • Publication
    Contribution of stilbene-imine additives on the structural, ionic conductivity performance and theoretical evaluation on CMC-based biopolymer electrolytes
    (Elsevier, 2020)
    Rafizah Rahamathullah
    ;
    Wan M. Khairul
    ;
    M.I.N Isa
    New solid biopolymer electrolytes (SBEs) were prepared by integrating stilbene-imine derivatives bearing vinylene (–CH[dbnd]CH–) and azomethine (–CH[dbnd]N–) as additives in carboxymethyl cellulose (CMC) based electrolyte. The investigation on their spectroscopic and theoretical assessments were conducted to alter the energy level in improving the structural and ionic conductivity performance. The simulated results from frontier molecular orbitals (FMO) and Mulliken-charge analysis revealed that -CF3 and -NO2 substituents significantly reduce the HOMO-LUMO gap up to 0.68 eV. The highest ionic conductivity of SBEs achieved at ambient temperature was ∼8 × 10−3 Scm-1 upon the addition of additive, obeying an Arrhenius model with reciprocal of temperature (303 K–373 K). The coordination interaction of C–O bond and CH[dbnd]N band facilitated the dissociation of more cation (H+) of NH4Cl which permits alternative route for H+ to hop into coordinating site in CMC. The outcomes are ideal in the development of electrochemical devices.
  • Publication
    The structure-property studies and mechanism of optical limiting action of methyl 4-((4-aminophenyl)ethynyl)benzoate crystal under continuous wave laser excitation
    (Elsevier, 2020)
    Muhamad Fikri Zaini
    ;
    Wan Mohd Khairul
    ;
    Suhana Arshad
    ;
    Mundzir Abdullah
    ;
    Dian Alwani Zainuri
    ;
    Rafizah Rahamathullah
    ;
    Muhammad Izz Rosli
    ;
    Muhammad Safwan Abd Aziz
    ;
    Ibrahim Abdul Razak
    This study focuses on the design of the new dye of donor-π-acceptor (D−π−A) system of methyl 4-((4-aminophenyl)ethynyl)benzoate (MAPEB) to highlight its structural-property relation through a combined experimental and quantum chemical calculation approaches for optical limiting applications. MAPEB was synthesized via aerobic condition palladium-catalysed Sonogashira cross-coupling reaction with good yield. This molecular structure was confirmed by single crystal X-ray crystallographic analysis and the crystal exhibits monoclinic non-centrosymmetric space group of Pc. The existence of intermolecular interactions was confirmed by Hirshfeld analysis, showing high contribution of C⋯H contact which suggested the high nonlinear optical response of the compound. The experimental spectroscopic data including Fourier Transform Infrared (FT-IR), 1H and 13C Nuclear Magnetic Resonance, electronic absorption spectra, HOMO-LUMO energy gap were compared with Density Functional Theory (DFT) at 6–311++G (d,p) basis set. The experimental results complement the theoretical findings in supporting anticipated electronic properties of the molecule. Additionally, the z-scan analysis unveils an excellent value of χ3 of MAPEB in the order of 10−6 esu which indicate good nonlinear optical material under 532 nm continuous wave laser. Low optical limiting action was measured at 110 kW/cm2 which is suitable for various continuous wave laser applications. These findings prove that MAPEB has the potential to be employed as NLO materials for photonic applications.
  • Publication
    Computational and experimental investigation of antibacterial properties of Some Fluorinated Thioureas
    (Taylor & Francis, 2023)
    Anisatul Aqidah Tagiling
    ;
    Wan Mohd Khairul
    ;
    Rafizah Rahamathullah
    ;
    Vigneswari Sevakumaran
    ;
    Mas Mohammed
    ;
    Syaharil Saidin
    Herein, fluorinated thioureas with various substituents (F1-F3) were synthesized and characterized spectroscopically and analytically to investigate their properties as antibacterial agents. Prior to experimental studies, Density Functional Theory (DFT) modeling was performed at B3LYP/6-31G (d,p) to complement and offer comparative overview with the experimental findings. With regards to all theoretical analyses, the Frontier Molecular Orbital (FMO) demonstrated a desirable low HOMO-LUMO gap for all three designated derivatives, particularly F1 (1.60 eV), which is consistent with its GCRDs values, namely its high electronegativity and low hardness values that corresponds to low LUMO energy, suggesting higher bacterial activity. Agar diffusion assay was used for the preliminary screening of in-vitro antibacterial activity against pathogenic Gram-positive and Gram-negative bacteria. All three derivates successfully inhibit at least two bacterial strains (B. cereus, S. aureus), but none were able to penetrate into E. coli. The highest inhibition rate was exhibited by F3 at 33.33 ± 0.71% against S. aureus, whilst F1 only managed to gain 29.63 ± 0.00% of inhibition rate for the same bacterium. Meanwhile, the lowest penetration rate was recorded at 1.53 ± 0.35% by F2 against B. cereus.
  • Publication
    Chitosan based solid electrolyte doped with new azo-azomethine additive for electric double-layer capacitor (EDLCs)
    (Elsevier Ltd, 2025-06-10)
    Tuan Siti Fatimah Tuan Mohd Pauzi
    ;
    Rafizah Rahamathullah
    ;
    M.N. Hafiza
    ;
    Qian Yee Ang
    ;
    Wan M. Khairul
    ;
    Artiqah Khairudin
    ;
    M.I. Rosli
    ;
    Fatin Saiha Omar
    Biopolymer-based solid electrolytes are gaining attention for their potential in electric double-layer capacitors (EDLCs). However, their practical application is limited by drawbacks such as low electrical performance and increased corrosive reactivity due to excessive amount of plasticizers. This present study investigates the effect of an azo-azomethine (AI) additive featuring hybrid (-N=N-) and (-CH=N-) groups, incorporated into a chitosan biopolymer matrix as a novel electrolyte for enhancing EDLC performance. Simulated results of the molecular electrostatic potential (MEP) and frontier molecular orbitals (FMO) suggest that the nitrogen (N) and oxygen (O) atoms from the azo and alkoxy substituents modulate the energy level of AI by reducing the HOMO-LUMO gap to 2.17 eV. The interaction between AI additive and chitosan was assessed using FTIR and powder-XRD analyses. The ionic conductivity of the prepared SBEs also increased by eight orders of magnitude from 7.38 × 10−10 S/cm to 1.27 × 10−2 S/cm with the contribution of 8 wt% of the additive. The EDLC cell was constructed by placing the prepared SBE within carbon-based electrodes, resulting in a specific capacitance 2.05 × 10−5 F/g. Thus, these findings demonstrate promising potential for electrochemical device applications.