International Journal of Chemistry

International Journal of Chemistry | Vol. 8, No. 2, February 2017 | pp. 9–16

DOI: 10.46882/2017/IJC/000101

Article Type: Original Research Paper

Title: Synthesis, Luminescent Properties, and Fluorimetric Detection of Nitroaromatic Explosives Using Novel Terbium(III) β-Diketone Complexes

Names of Authors: A. O. Balogun¹, J. E. Kim²*

Authors’ Affiliations:
¹Department of Chemistry, University of Ilorin, Ilorin, Nigeria.
²Department of Chemistry, Seoul National University, Seoul, South Korea.

Abstract: Rare-earth coordination materials displaying highly sensitive photoluminescent behaviors are increasingly sought for chemical sensor fabrications due to their sharp emission bands and high signal-to-noise ratios. This study reports the synthesis, material characterization, and analytical sensor optimization of a novel terbium(III) complex using 2-thenoyltrifluoroacetone and 1,10-phenanthroline ligands. Structural configurations were verified using elemental analysis, molar conductance, and Fourier-transform infrared (FT-IR) spectroscopy. Analytical calculations confirmed a 1:3:1 metal-to-ligand stoichiometric coordination pattern, conforming to the formula [Tb(TTA)₃(phen)]. Molar conductivity tests in acetonitrile confirmed a completely non-electrolytic layout. Photoluminescence scanning at room temperature showed intense green monochromatic emission peaks at 545 nm, corresponding to the characteristic ⁵D₄ to ⁷F₅ electronic transition of the central Tb(III) ion. The analytical potential of the complex as a fluorimetric sensor for trace nitroaromatic explosives was evaluated in aqueous media. The introduction of picric acid caused immediate, highly selective luminescence quenching of the green emission intensity. The fluorimetric quenching behavior followed the Stern-Volmer relationship with a high quenching constant (Ksv) of 4.5 x 10⁴ M⁻¹ and a low limit of detection (LOD) of 0.18 μM, pointing to a photoinduced electron transfer pathway.

Keywords: Terbium complexes; Rare earth elements; Photoluminescence; Fluorimetric sensor; Nitroaromatic explosives; Stern-Volmer relation

Manuscript Timeline: Received: May 12, 2016; Revised: June 25, 2016; Accepted: July 18, 2016; Published: February 04, 2017.

Citation: Balogun, A. O., & Kim, J. E. (2017). Synthesis, Luminescent Properties, and Fluorimetric Detection of Nitroaromatic Explosives Using Novel Terbium(III) β-Diketone Complexes. International Journal of Chemistry, 8(2), 9–16.

International Journal of Chemistry | Vol. 8, No. 8, August 2017 | pp. 57–64

DOI: 10.46882/2017/IJC/000107

Article Type: Original Research Paper

Title: Green Corrosion Inhibition of Carbon Steel in Acidic Medium Using Fruit Extract of Solanum melongena

Names of Authors: M. A. Haruna¹, S. K. Bhattacharya²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Minna, Nigeria.
²Department of Chemistry, Indian Institute of Technology, Kharagpur, India.

Abstract: The utilization of toxic synthetic chemical inhibitors in industrial acid descaling operations creates substantial environmental and safety hazards, driving research into sustainable green alternatives. The corrosion mitigation performance of the aqueous fruit extract of Solanum melongena (SM-Extract) on carbon steel in 0.5 M H₂SO₄ was investigated via gravimetric weight loss and electrochemical test protocols. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements were recorded across varying inhibitor dosages (0.2 to 2.0 g/L) and system temperatures (303 to 333 K). Weight loss metrics revealed that protection efficiency increased with extract concentration, peaking at 91.4% at a dose of 2.0 g/L. Polarization diagrams established that SM-Extract functions as a mixed-type inhibitor, suppressing both anodic iron dissolution and cathodic hydrogen gas evolution pathways. EIS scans confirmed that charge-transfer resistance (Rct) increased with higher extract amounts, indicating the formation of a robust organic protective film on the steel face. The adsorption behavior of the bioactive compounds conformed to the Langmuir isotherm model, yielding a negative standard free energy of adsorption (delta G°ads = -20.8 kJ/mol), denoting a spontaneous physical adsorption mechanism driven by the presence of rich plant anthocyanins.

Keywords: Carbon steel; Corrosion inhibition; Solanum melongena; Electrochemical impedance spectroscopy; Polarization; Adsorption isotherm

Manuscript Timeline: Received: August 14, 2016; Revised: September 25, 2016; Accepted: October 15, 2016; Published: August 03, 2017.

Citation: Haruna, M. A., & Bhattacharya, S. K. (2017). Green Corrosion Inhibition of Carbon Steel in Acidic Medium Using Fruit Extract of Solanum melongena. International Journal of Chemistry, 8(8), 57–64.

International Journal of Chemistry | Vol. 8, No. 3, March 2017 | pp. 17–24

DOI: 10.46882/2017/IJC/000102

Article Type: Original Research Paper

Title: Adsorptive Sequestration of Mercury(II) Ions from Simulated Saline Wastewater Using Thiolated Peppermint Waste

Names of Authors: E. N. Chidi¹, L. M. van der Westhuizen²*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Nigeria.
²Department of Chemical Engineering, Stellenbosch University, Stellenbosch, South Africa.

Abstract: Industrial wastewater from chlorine-alkali facilities often contains high residual levels of highly toxic mercury(II) ions, requiring affordable and chemically stable biopolymer extraction networks. This paper evaluates the adsorptive performance of modified peppermint (Mentha piperita) waste prepared via chemical functionalization with thioglycolic acid (thiolation). The surface morphology and active site modifications of the matrix were examined through scanning electron microscopy (SEM) and FT-IR spectroscopy. The structural evaluations confirmed that thiolation successfully integrated sulfur-rich thiol (-SH) ligand centers onto the lignocellulosic biomass strands. Batch adsorption tests evaluated variables of baseline solution pH, contact period, adsorbent load, and initial metal concentrations. Maximum Hg(II) extraction occurred at an optimum pH of 5.5, using an equilibrium contact period of 60 minutes. The equilibrium distribution datasets matched closely with the Langmuir isotherm expressions, yielding a high maximum monolayer adsorption capacity of 74.45 mg/g at 298 K. Sorption kinetics conformed perfectly to a pseudo-second-order mechanism with high correlation coefficients (R² > 0.999), proving that strong chemical surface coordination controlled the phase transfer rates. Thermodynamic constants established that the process was spontaneous and endothermic, positioning thiolated biomass as a highly viable material for toxic water remediation.

Keywords: Peppermint waste; Chemical modification; Thiolation; Mercury removal; Sorption kinetics; Coordination chemistry

Manuscript Timeline: Received: June 02, 2016; Revised: July 15, 2016; Accepted: August 10, 2016; Published: March 08, 2017.

Citation: Chidi, E. N., & van der Westhuizen, L. M. (2017). Adsorptive Sequestration of Mercury(II) Ions from Simulated Saline Wastewater Using Thiolated Peppermint Waste. International Journal of Chemistry, 8(3), 17–24.

International Journal of Chemistry | Vol. 8, No. 4, April 2017 | pp. 25–32

DOI: 10.46882/2017/IJC/000103

Article Type: Original Research Paper

Title: Phytochemical Fingerprinting, Essential Oil Profiling, and In Vitro Larvicidal Efficacy of Eucalyptus camaldulensis Leaf Extract

Names of Authors: S. A. Abdulrahman¹, G. E. D. M. Santos²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Minna, Nigeria.
²Department of Chemistry, University of Campinas, Campinas, Brazil.

Abstract: The rampant spread of mosquito vectors in tropical regions demands the identification of botanical insecticidal alternatives to replace hazardous synthetic chemicals that induce environmental toxicity. This research reports the qualitative chemical mapping, essential oil separation via Gas Chromatography-Mass Spectrometry (GC-MS), and in vitro larvicidal efficacy of Eucalyptus camaldulensis leaf fractions against Anopheles gambiae fourth-instar larvae. Essential oils obtained via hydro-distillation in a Clevenger apparatus were resolved into 22 distinct peaks via GC-MS, with 1,8-cineole (45.8%), alpha-pinene (14.2%), and p-cymene (11.5%) emerging as the primary bioactive constituents. Larvicidal bioassays were conducted across a suite of oil concentrations (20 to 100 mg/L) over 24-hour exposure periods. The essential oil displayed significant lethal potency, yielding an LC50 value of 42.6 mg/L and an LC90 value of 78.4 mg/L against the mosquito larvae. A linear relationship was observed between the concentration of 1,8-cineole and larval mortality. This confirms that volatile monoterpenes actively disrupt the respiratory and neurological pathways of insect vectors, offering a sustainable botanical framework for malaria vector management.

Keywords: Eucalyptus camaldulensis; Essential oils; GC-MS analysis; 1,8-Cineole; Larvicidal bioassay; Anopheles gambiae

Manuscript Timeline: Received: June 15, 2016; Revised: July 28, 2016; Accepted: August 22, 2016; Published: April 02, 2017.

Citation: Abdulrahman, S. A., & Santos, G. E. D. M. (2017). Phytochemical Fingerprinting, Essential Oil Profiling, and In Vitro Larvicidal Efficacy of Eucalyptus camaldulensis Leaf Extract. International Journal of Chemistry, 8(4), 25–32.

International Journal of Chemistry | Vol. 8, No. 12, December 2017 | pp. 89–96

DOI: 10.46882/2017/IJC/000111

Article Type: Original Research Paper

Title: Green Synthesis of Gold Nanoparticles Using Aqueous Leaf Extract of Alchornea cordifolia and Catalytic Reduction of Methylene Blue

Names of Authors: S. I. Musa¹, C. R. de Souza²*

Authors’ Affiliations:
¹Department of Chemistry, University of Jos, Jos, Nigeria.
²Department of Chemical Engineering, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.

Abstract: The biological synthesis of noble metal nanomaterials using tropical flora presents an eco-friendly and economically sustainable alternative to hazardous chemical reduction pathways. This study describes the green synthesis of stable gold nanoparticles (AuNPs) utilizing the aqueous leaf extract of Alchornea cordifolia as a powerful reducing and capping agent. The bioreduction process was monitored via UV-Vis spectrophotometry, which revealed a distinct surface plasmon resonance peak at 532 nm, confirming the nucleation of metallic gold. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses showed highly spherical nanoparticles with an average particle diameter of 15 nm. X-ray diffraction (XRD) patterns confirmed the face-centered cubic crystalline structure of the biosynthesized gold. Fourier-transform infrared (FT-IR) spectroscopy indicated that water-soluble polyphenols and flavonoids within the leaf matrix were responsible for capping and protecting the AuNPs against structural agglomeration. The catalytic efficiency of the synthesized AuNPs was evaluated by tracking the chemical reduction of methylene blue dye by sodium borohydride (NaBH₄) in an aqueous system. In the presence of the green catalyst, the reaction achieved 96.8% decolorization within 8 minutes. The dye degradation kinetics conformed tightly to the pseudo-first-order kinetic model with a rate constant of 0.295 min⁻¹, indicating excellent catalytic potential for textile wastewater treatment arrays.

Keywords: Gold nanoparticles; Green synthesis; Alchornea cordifolia; Biosynthesis; Heterogeneous catalysis; Methylene blue degradation

Manuscript Timeline: Received: October 12, 2016; Revised: November 24, 2016; Accepted: December 18, 2016; Published: December 04, 2017.

Citation: Musa, S. I., & de Souza, C. R. (2017). Green Synthesis of Gold Nanoparticles Using Aqueous Leaf Extract of Alchornea cordifolia and Catalytic Reduction of Methylene Blue. International Journal of Chemistry, 8(12), 89–96.

International Journal of Chemistry | Vol. 8, No. 6, June 2017 | pp. 41–48

DOI: 10.46882/2017/IJC/000105

Article Type: Original Research Paper

Title: Kinetic Studies and Mechanistic Pathway of the Chromic Acid Oxidation of L-Methionine in Aqueous Acidic Medium

Names of Authors: T. M. Usman¹, F. A. Al-Otaibi²*

Authors’ Affiliations:
¹Department of Chemistry, Bayero University, Kano, Nigeria.
²Department of Chemistry, King Abdulaziz University, Jeddah, Saudi Arabia.

Abstract: Investigating the kinetics of transition metal electron transfer processes involving sulfur-containing amino acids provides vital structural indicators required to map metabolic oxidation pathways. The oxidation of L-methionine by chromic acid (H₂CrO₄) was investigated spectrophotometrically in an aqueous perchloric acid medium at a constant ionic strength of 0.40 M (NaClO₄). The reaction progress was monitored under pseudo-first-order conditions by following the absorbance decay of Cr(VI) at its wavelength maximum of 350 nm. The empirical rate law showed a first-order dependence on [chromic acid] and a fractional-first-order dependence on [L-methionine]. The reaction rate increased with rising hydronium ion concentration, revealing an acid-catalyzed pathway governed by the active protonated oxidant species, [HCrO₃⁺]. Variations in the dielectric constant of the solvent medium produced significant kinetic shifts, confirming a rate-determining step involving two polar molecular species. Stoichiometric determinations confirmed that 3 moles of L-methionine consumed 2 moles of chromic acid, producing methionine sulfoxide and Cr(III) ions as the primary end products. Thermodynamic activation constants calculated from temperature-dependence datasets using the Eyring equation yielded an enthalpy of activation (delta H*) of 48.5 kJ/mol and an entropy of activation (delta S*) of -104.2 J/mol K, supporting an inner-sphere mechanism.

Keywords: Reaction kinetics; Spectrophotometry; Chromic acid oxidation; L-methionine; Activation parameters; Inner-sphere mechanism

Manuscript Timeline: Received: July 10, 2016; Revised: August 20, 2016; Accepted: September 15, 2016; Published: June 03, 2017.

Citation: Usman, T. M., & Al-Otaibi, F. A. (2017). Kinetic Studies and Mechanistic Pathway of the Chromic Acid Oxidation of L-Methionine in Aqueous Acidic Medium. International Journal of Chemistry, 8(6), 41–48.