International Journal of Chemistry

International Journal of Chemistry | Vol. 12, No. 11, November 2021 | pp. 81–88

DOI: 10.46882/2021/IJC/000157

Article Type: Original Research Paper

Title: Electrochemical Properties and Supercapacitive Characterization of Polyaniline-Graphene Oxide Micro-Electrode Arrays

Names of Authors: U. B. Aliyu¹, K. Y. Lee²*

Authors’ Affiliations:
¹Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria.
²Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore.

Abstract: Fabricating highly efficient electrochemical energy storage units requires the development of hybrid polymer electrodes that exhibit high specific capacitance and fast ion diffusion kinetics. This research details the synthesis and electrochemical characterization of polyaniline-graphene oxide (PANI-GO) thin-film micro-electrode arrays prepared via in situ chemical oxidative polymerization pathways. The surface topology and morphological features of the hybrid films were analyzed using field emission scanning electron microscopy (FESEM), FT-IR, and Raman spectroscopy. FESEM imaging confirmed that a highly continuous, ultra-thin polyaniline layer was uniformly deposited across the conductive graphene oxide skeletal network. Electrochemical performance was investigated via cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) loops in a 1.0 M H₂SO₄ electrolyte system. The optimized PANI-GO hybrid electrode delivered a maximum specific capacitance of 412 F/g at a current density of 1.0 A/g, which was substantially higher than standalone pure polyaniline films (145 F/g). Electrochemical impedance spectroscopy (EIS) data showed a very low charge-transfer resistance of 0.38 ohms, confirming accelerated ionic transport across the polymeric interface. Cyclic stability evaluations proved that the composite material retained 89.2% of its capacitive profile after 2000 continuous cycles.

Keywords: Polyaniline; Graphene oxide; Energy storage; Supercapacitors; Cyclic voltammetry; Specific capacitance

Manuscript Timeline: Received: January 22, 2021; Revised: February 25, 2021; Accepted: March 18, 2021; Published: November 09, 2021.

Citation: Aliyu, U. B., & Lee, K. Y. (2021). Electrochemical Properties and Supercapacitive Characterization of Polyaniline-Graphene Oxide Micro-Electrode Arrays. International Journal of Chemistry, 12(11), 81–88.

International Journal of Chemistry | Vol. 12, No. 8, August 2021 | pp. 57–64

DOI: 10.46882/2021/IJC/000154

Article Type: Original Research Paper

Title: Spatial Analysis, Geochemical Speciation, and Environmental Carcinogenicity of Hexavalent Chromium in Well Waters Near Chemical Plants

Names of Authors: T. H. Awotunde¹, R. A. Silva²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Agriculture, Abeokuta, Nigeria.
²Department of Environmental Chemistry, University of São Paulo, São Paulo, Brazil.

Abstract: Industrial chemical operations discharge substantial amounts of chromium-rich wastes into surrounding topsoils, causing toxic heavy metal leaching into shallow drinking water wells. This study monitors the spatial variations, chemical speciation, and carcinogenic health risk profiles of chromium compounds across twenty household wells positioned around an active chemical manufacturing estate. Water monitoring was carried out over consecutive wet and dry cycles. Total chromium levels and carcinogenic hexavalent chromium [Cr(VI)] fractions were quantified utilizing ion chromatography coupled with inductively coupled plasma mass spectrometry (IC-ICP-MS). Total chromium concentrations ranged from 12.5 to 145.8 μg/L, with 45% of monitored groundwater sites surpassing the strict WHO drinkable contaminant threshold of 50.0 μg/L. Speciation analysis showed that toxic Cr(VI) was the dominant species, accounting for up to 68.4% of the total metal burden profiles at down-gradient coordinates. Seasonal mapping confirmed elevated chromium mobilization during the rainy period, indicating rain-induced plume leaching. Chronic Daily Intake (CDI) projections and Lifetime Cancer Risk (LCR) indices for child consumption cohorts surpassed 2.4 in 10,000 near industrial boundaries, emphasizing an immediate public healthcare concern and a need for local membrane filtration arrays.

Keywords: Groundwater pollution; Chromium speciation; Hexavalent chromium; Ion chromatography; Chemical effluents; Cancer risk assessment

Manuscript Timeline: Received: December 02, 2020; Revised: January 14, 2021; Accepted: February 10, 2021; Published: August 03, 2021.

Citation: Awotunde, T. H., & Silva, R. A. (2021). Spatial Analysis, Geochemical Speciation, and Environmental Carcinogenicity of Hexavalent Chromium in Well Waters Near Chemical Plants. International Journal of Chemistry, 12(8), 57–64.

International Journal of Chemistry | Vol. 12, No. 2, February 2021 | pp. 9–16

DOI: 10.46882/2021/IJC/000146

Article Type: Original Research Paper

Title: Synthesis, Computational Modeling, and Enzymatic Inhibition Screening of Novel N-Substituted Phthalimide Derivatives

Names of Authors: O. M. Kolawole¹, E. R. Watson²*

Authors’ Affiliations:
¹Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeria.
²Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.

Abstract: Inhibiting alpha-glucosidase represents a critical therapeutic target for managing postprandial hyperglycemia in type 2 diabetes mellitus. In this work, five novel N-substituted phthalimide derivatives were synthesized via the condensation of phthalic anhydride with various substituted aniline compounds in the presence of catalytic glacial acetic acid. The molecular frameworks of the synthesized targets were verified using elemental analysis, FT-IR, and ¹H-NMR spectroscopy. In vitro alpha-glucosidase enzyme inhibition assays revealed that compound 3c, bearing a p-nitro substituent, possessed the highest inhibitory potency, showing an IC50 value of 12.4 μM, compared to the acarbose clinical standard (IC50 = 38.2 μM). To investigate specific binding configurations, in silico molecular docking simulations were run inside the catalytic domain of alpha-glucosidase using AutoDock Vina software. The computational docking models demonstrated that the phthalimide carbonyl forms stable hydrogen bonds with Asp214 and Arg315 residues. The aromatic ring extensions fit well into the hydrophobic pocket, engaging in significant pi-pi stacking interactions with Phe178. These structural contacts stabilize the ligand-protein topology, explaining the sub-micromolar inhibition constants and presenting a potential scaffold for further antidiabetic drug design.

Keywords: Phthalimide; Chemical synthesis; Alpha-glucosidase; Enzyme inhibition; Molecular docking; Antidiabetic drug design

Manuscript Timeline: Received: June 12, 2020; Revised: July 25, 2020; Accepted: August 18, 2020; Published: February 06, 2021.

Citation: Kolawole, O. M., & Watson, E. R. (2021). Synthesis, Computational Modeling, and Enzymatic Inhibition Screening of Novel N-Substituted Phthalimide Derivatives. International Journal of Chemistry, 12(2), 9–16.

International Journal of Chemistry | Vol. 12, No. 4, April 2021 | pp. 25–32

DOI: 10.46882/2021/IJC/000148

Article Type: Original Research Paper

Title: Green Synthesis of Silver-Platinum Bimetallic Nanoparticles Using Podocarpus falcatus Extract and Their Catalytic Efficiency

Names of Authors: S. I. Musa¹, K. A. Al-Jubouri²*

Authors’ Affiliations:
¹Department of Chemistry, University of Jos, Jos, Nigeria.
²Department of Chemistry, University of Baghdad, Baghdad, Iraq.

Abstract: The biological synthesis of bimetallic platinum-silver nanoparticles using medicinal plant extracts offers an eco-friendly and economically sustainable alternative to traditional chemical reduction protocols. This study details the green synthesis of stable platinum-silver (Pt-Ag) alloy nanoparticles utilizing the aqueous leaf extract of Podocarpus falcatus as both a reducing and stabilizing agent. The bioreduction process was monitored via UV-Vis spectrophotometry, which revealed the gradual decay and disappearance of the metal precursor bands over 60 minutes. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses showed highly spherical nanoparticles with an average particle diameter of 16 nm. X-ray diffraction (XRD) patterns confirmed the alloyed crystalline structure of the biosynthesized bimetallic system. Fourier-transform infrared (FT-IR) spectroscopy indicated that water-soluble biomolecules, primarily flavonoids and terpenoids within the leaf matrix, were responsible for capping and protecting the nanoparticles against structural agglomeration. The catalytic efficiency of the synthesized Pt-Ag nanoparticles was evaluated by tracking the reduction of rhodamine B dye by sodium borohydride (NaBH₄) in an aqueous system. In the absence of a catalyst, the reaction proceeded slowly, but the introduction of bimetallic nanoparticles accelerated the degradation process, achieving 97.4% decolorization within 10 minutes, outperforming monometallic controls.

Keywords: Bimetallic nanoparticles; Green synthesis; Podocarpus falcatus; Alloy structure; Heterogeneous catalysis; Rhodamine B degradation

Manuscript Timeline: Received: October 12, 2020; Revised: November 24, 2020; Accepted: December 18, 2020; Published: April 02, 2021.

Citation: Musa, S. I., & Al-Jubouri, K. A. (2021). Green Synthesis of Silver-Platinum Bimetallic Nanoparticles Using Extract of Podocarpus falcatus and Their Catalytic Efficiencies. International Journal of Chemistry, 12(4), 25–32.

International Journal of Chemistry | Vol. 12, No. 7, July 2021 | pp. 49–56

DOI: 10.46882/2021/IJC/000153

Article Type: Original Research Paper

Title: Synthesis, Microstructural Framework, and Swelling Kinetics of Xanthan Gum-Graft-Polyacrylamide Hydrogels

Names of Authors: J. K. Mensah¹, S. K. Roy²*

Authors’ Affiliations:
¹Department of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
²Department of Chemical Engineering, Indian Institute of Technology, Kharagpur, India.

Abstract: The development of durable biopolymeric hydrogel networks is essential for agricultural soil water retention and controlled agrochemical delivery due to the requirement for specific structural coordination sites. This study describes the chemical synthesis and rheological optimization of a hybrid hydrogel fabricated via the free-radical graft copolymerization of acrylamide onto a high-viscosity xanthan gum backbone. The grafting reaction was initiated using potassium persulfate (KPS) and crosslinked via N,N'-methylenebisacrylamide (MBA) under optimized atmospheric conditions. Structural networks and morphology features were characterized using FT-IR spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Swelling kinetics were evaluated as a function of time, pH, and saline concentration. The hydrogel showed highly responsive pH-dependent swelling profiles, achieving a maximum water absorption capacity of 410 g/g at pH 7.4 due to structural carboxylate ionizations causing intermolecular chain repulsions. Rheological analysis confirmed strong non-Newtonian shear-thinning characteristics with a storage modulus (G') that remained constant up to 80°C. Batch adsorption tests showed high affinity for divalent zinc and copper ions, matching the Langmuir isotherm with monolayer capacities of 72.4 mg/g and 85.6 mg/g at 298 K, confirming high remediation potential.

Keywords: Xanthan gum; Acrylamide; Graft copolymerization; Hydrogel; Swelling kinetics; Heavy metal adsorption

Manuscript Timeline: Received: November 15, 2020; Revised: December 22, 2020; Accepted: January 20, 2021; Published: July 08, 2021.

Citation: Mensah, J. K., & Roy, S. K. (2021). Synthesis, Microstructural Framework, and Swelling Kinetics of Xanthan Gum-Graft-Polyacrylamide Hydrogels. International Journal of Chemistry, 12(7), 49–56.

International Journal of Chemistry | Vol. 12, No. 10, October 2021 | pp. 73–80

DOI: 10.46882/2021/IJC/000156

Article Type: Original Research Paper

Title: Mechanochemical Optimization and Structural Framework of Slag-Based Geopolymer Binders Reinforced with Alumina Nanoparticles

Names of Authors: T. S. Ani¹, M. F. de Oliveira²*

Authors’ Affiliations:
¹Department of Electronic and Chemical Engineering, Enugu State University of Science and Technology, Enugu, Nigeria.
²Department of Chemical Engineering, Instituto Superior Técnico, Lisbon, Portugal.

Abstract: Developing high-performance geopolymer grouts from industrial wastes decreases production carbon footprints, though enhancing mechanical integrity requires structural optimization via reactive nanomaterial additives. This research tracks the structural development and mechanical profiles of geopolymer cements synthesized from ground granulated blast furnace slag (GGBS) integrated with nano-alumina (nano-Al₂O₃) particles at dosages from 0% to 3.0% by weight. Alkaline activation was executed utilizing structural mixtures of sodium silicate and 12 M sodium hydroxide solutions. Hardening kinetics and microstructural phases were analyzed using X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, and Scanning Electron Microscopy (SEM). FT-IR spectra demonstrated the formation of a rigid silicate network, indicated by the prominent framework stretching bands shifting to 1012 cm⁻¹. Compressive strength experiments showed that grout cubes prepared with 2.0% nano-alumina substitution reached a maximum compressive value of 58.4 MPa after 28 days of curing at room temperature, outperforming pure slag controls. SEM characterization revealed a highly dense matrix featuring intense structural crosslinking of calcium silicate hydrate (C-S-H) gel structures, which significantly reduces internal cracking.

Keywords: Geopolymer grout; Slag activation; Nano-alumina; Compressive strength; Microstructure; C-S-H gel networks

Manuscript Timeline: Received: January 14, 2021; Revised: February 18, 2021; Accepted: March 12, 2021; Published: October 05, 2021.

Citation: Ani, T. S., & de Oliveira, M. F. (2021). Mechanochemical Optimization and Structural Framework of Slag-Based Geopolymer Binders Reinforced with Alumina Nanoparticles. International Journal of Chemistry, 12(10), 73–80.