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

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Exploring ethynyl-based chalcones as green semiconductor materials for optical limiting interests

2024 , Wan M. Khairul , Fatimah Hashim , Rafizah Rahamathullah , Mas Mohammed , Siti Aisyah Razali , Syed Ahmad Tajudin Tuan Johari , Suha Azizan

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The structure-property studies and mechanism of optical limiting action of methyl 4-((4-aminophenyl)ethynyl)benzoate crystal under continuous wave laser excitation

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.

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The influence of Ammonium Formate concentration on the electrical performance of 2-Hydroxyethyl cellulose solid biopolymer electrolytes

2025 , Nur Maisarah Batrisyia Mohd Bahaudin , Mohd Ibnu Haikal Ahmad Sohaimy , Syahida Suhaimi , Wan Mohd Khairul Wan Mohamed Zin , Md Uwaisulqarni Osman , Mohamad Fakhratul Ridwan Zulkifli , Rafizah Rahamathullah , Muthuvinayagam Muthiah , Mohd Ikmar Nizam Mohamad Isa

Novel solid biopolymer electrolytes (SBE) with various amounts of ammonium formate (AF) salt doped into 2-hydroxyethyl cellulose (2-HEC) are fabricated by using a well-known technique, solution casting. The SBEs are developed mainly to address the leakage, toxic material issues, safety concerns, and costs associated with conventional liquid-based electrolytes. The 2-HEC-based SBE is analyzed for its ionic conductivity and electrical properties. The highest ionic conductivity achieved was 2.40 × 10-3 S/cm for AF40 (40 wt.% AF salt). The bulk resistance value obtained at ambient and elevated temperatures emphasizes its effect on ionic conductivity and electrical behavior regarding its dielectric permittivity. The activation energy from the temperature-dependent ionic conductivity indicates that activation energy decreases with increasing temperature. The two primary transport parameters affecting the system's ionic conductivity based on the Rice and Roth model are the diffusion coefficient (D) and ion mobility (µ). This study showed that the rise in ionic conductivity depends on the concentration of ammonium formate salt.

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Deciphering ethynyl single crystal for NLO applications: Synergistic studies on the structural, Hirshfeld surface, photophysical and DFT assessment

2024 , Wan M. Khairul , Mas Mohammed , Rafizah Rahamathullah , Muhamad Fikri Zaini , Suhana Arshad , Abdul Razak Ibrahim , Fazira Ilyana Abdul Razak , Suhaila Sapari

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An integrated DFT calculation and adsorption study of desiccated coconut waste-based biochar in CO2 environment

2024-01-01 , Rafizah Rahamathullah , Zakaria D.S. , Siti Khalijah Mahmad Rozi , Hairul Nazirah Abdul Halim , Razak F.I.A. , Sapari S.

Abstract: This study presents a new series of amine-functionalized biochar derived from desiccated coconut waste (amine-biochar@DCW) as potential CO2 adsorbents. The CO2 adsorption experiment revealed that TETA-biochar@DCW had the highest adsorption capacity of 61.78 mg/g. Prior to the experimental studies, Density Functional Theory (DFT) was conducted at B3LYP/6-31G (d,p) to evaluate the energy band gap, global chemical reactivity descriptors (GCRD), and molecular electrostatic potentials (MEP) to compare the experimental findings. The results from the simulated data indicate that TETA-biochar@DCW has the lowest HOMO–LUMO gap at 2.7890 eV before adsorption, and it increases after CO2 adsorption occurs. The 3D plots from MEP also show that TETA-biochar@DCW is a reactive adsorbent for CO2 gases. Overall, the theoretical and experimental results of the amine-biochar@DCW suggest its potential as a promising and cost-effective adsorbent for CO2 capture. Highlights: • Newly prepared amine-biochar@DCW was assessed as CO2 adsorbents. • TETA-biochar@DCW presents the highest CO2 capture capacity. • TETA substituents significantly reduce the HOMO-LUMO gap values. • 3D MEP plots confirm the adsorption ability of TETA-biochar@DCW towards CO2 gases. Graphical Abstract: [Figure not available: see fulltext.]

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Computational and experimental investigation of antibacterial properties of Some Fluorinated Thioureas

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.

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Chitosan based solid electrolyte doped with new azo-azomethine additive for electric double-layer capacitor (EDLCs)

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.

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Contribution of stilbene-imine additives on the structural, ionic conductivity performance and theoretical evaluation on CMC-based biopolymer electrolytes

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.

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The effect of NHâ‚„Br composition on electrical behaviour of 2-Hydroxyethyl cellulose solid biopolymer electrolytes

2025-02 , Nurul Faeqah Mazalan , Mohd Ibnu Haikal Ahmad Sohaimy , Azwani Sofia Ahmad Khiar , Wan Mohd Khairul Wan Mohamed Zin , Md Uwaisulqarni Osman , Mohammad Fakhratul Ridwan Zulkifli , Rafizah Rahamathullah , Muthiah Muthuvinayagam , Mohd Ikmar Nizam Mohamad Isa

In this study, solid biopolymer electrolytes (SBEs) were developed as an alternative to liquid electrolytes for battery applications. 2-hydroxyethyl cellulose (2HEC) served as the polymer host in the preparation of SBE films, incorporating varying amounts of ammonium bromide (NH4Br). The films were then analysed using electrical impedance spectroscopy (EIS) to investigate its electrical properties. The system containing 20 wt.% of NH₄Br achieved the highest conductivity at 3.9510-5 Scm-1 at ambient temperature of 303 K. The 2HEC-NH₄Br SBE film system was subjected to temperature variations between 303 K – 373 K in increments of 10 °C, revealing an increase in conductivity with rising temperature. This observation suggests that the SBE system adheres to the Arrhenius law, enabling the determination of the activation energy (Ea) through temperature dependence plotting. The Ea for the most conductive system reflects the lowest energy, indicating minimal energy required for the excitation process within the polymer chain. This Ea value offers a deeper insight into the transport parameters, including the number of mobile ions, ions mobility and diffusion coefficient, as determined through the Rice and Roth method.

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The experimental and DFT approaches on electronic, thermal and conductivity properties of non-linear optical bearing fused aromatic chalcones towards prospective OLEDs

2025-01 , Wan M. Khairul , Anisatul Aqidah Tagiling , Ain Qarina Muzaman , Rafizah Rahamathullah , Mas Mohammed , Syaharil Saidin , Suhana Arshad , Ibrahim Abdul Razak , Fazira Ilyana Abdul Razak , Suhaila Sapari

New derivatives of push-pull chalcone was successfully synthesized to demonstrate as NLO active on the impact of organic light emitting diode (OLED) materials. A total of three fused-aromatic chalcones (AA, AB, AC) with different substituents have been characterized through TGA, Z-scan analysis, 1H & 13C NMR, IR and UV–Vis. All the targeted compounds are nonlinear refraction (NLR) active with the range of χ(3) (∼ × 10–6 esu). AC reveals the highest value of first order hyperpolarizability (βtot) at 528.08 × 10–30 esu upon the substitution of strong electron acceptor. Theoretical investigation was performed by employing the theory of B3LYP/6–31 G (d,p) level via density functional theory (DFT) to optimize the geometries, molecular electrostatic potential (MEP) and frontier molecular orbitals (FMO). The predicted electronic properties of the molecule are supported by the experimental results, confirming the theoretical conclusions. The examination of its potential as emissive layer in OLED application was constructed on ITO substrate for electroluminescence behaviour evaluation under various direct current (DC) voltages supply. The preliminary outcomes reveal that these simple chalcone derivatives are capable of being utilised in any optoelectronic application.

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