Journal of the Serbian Chemical Society

The features of the intrinsic photoconductivity spectra of silver-doped zinc sulphide

2026-04-07T22:32:12+02:00

The intrinsic photoconductivity of silver-doped zinc sulphide (ZnS:Ag) was investigated. It was shown that doping with silver leads to significant modifications in the electronic structure and optical properties of ZnS due to the formation of localized energy levels within the band gap. Mechanical polishing of the sample surface resulted in the appearance of an additional photoconductivity maximum near the fundamental absorption edge, which gradually disappears during sample ageing. These effects are attributed to the compensation of donor and acceptor states, as well as to changes in charge carrier recombination mechanisms. The dependence of the photoconductivity spectrum on ageing time, the applied electric field, and the position of illumination relative to the contacts was established. The results are explained by variations in the lifetime of non-equilibrium charge carriers with depth. A qualitative model describing the photoconductivity spectra is proposed, taking into account the influence of silver compensation on the energy structure of ZnS. The proposed model provides insight into the photoconductive mechanisms and supports the development of ZnS-
-based optoelectronic materials.

The effect of catalyst composition and surface properties on the selective catalytic dehydrogenation of bioethanol

2026-04-21T22:35:43+02:00

The article provides a comparative analysis of bioethanol dehydrogenation using Cr–Cu–O and Ce–Cu–O catalyst systems. For the Cr–Cu–O catalysts, bioethanol is converted into a range of products including acetaldehyde, acetone and ethylene. Advanced characterization revealed that these catalysts are structurally complex, containing not only individual copper and chromium oxides but also a distinct compound, Cu₂CrO₄. A key finding is the clear structure–property relationship: the catalyst’s crystallinity, which varied widely from 41.9 (mostly amorphous) to 73.8 % (highly crystalline), has a major effect on its catalytic activity. The Ce–Cu–O system converted bioethanol into a diverse mixture of products such as acetaldehyde, acetone and ethyl acetate, indicating the occurrence of multiple simultaneous reactions, including dehydrogenation and condensation. Most compositions resulted in separate CeO₂ and CuO phases; however, a specific Ce:Cu ratio of 1:9 is unique. At this ratio, the material is reduced to form CeO₂ with elemental copper, rather than CuO, and its crystallinity increased from 52.7 to 71.2 %. The research showed that structural order is crucial for steering the reaction pathway, as only catalysts with low crystallinity produce ethyl acetate. Furthermore, while the specific surface area of a catalyst (5.0 to 17.0 m²/g in this study) is a key factor in surface-driven reactions such as dehydrogenation, it does not affect all products equally.

Metal complexes with Schiff base and benzimidazolylphenol ligands with tert-butyl and methoxy groups: Structural characterization and biological evaluation

2026-05-18T11:16:03+02:00

Two chelating ligands bearing tert-butyl and methoxy groups, an ONO type Schiff base (H₂L¹) and a benzimidazolylphenol derivative (HL²), NO type ligand, and their complexes with CoCl₂, NiCl₂, CuCl₂, ZnCl₂ and K₂PdCl₄ (1a–e and 2a–e, respectively) were synthesized and characterized. Various physicochemical and spectroscopic techniques were used to characterize the ligands. In addition, the crystal structure of H₂L¹ was determined by X-ray diffraction spectroscopy. Keto–enol tautomerism is observed in H₂L¹ according to spectral data. Elemental analysis, molar conductivity, magnetic moment and thermogravimetric analysis, as well as FT-IR, fluorescence, UV–Vis and NMR (for diamagnetic complexes) spectroscopic techniques, were utilized to characterize the complexes. Then, antibacterial, antifungal and antiviral activities of the compound were investigated. Antimicrobial activities of the compounds were tested toward six bacteria and three fungi. Some of the complexes exhibited higher activity towards some microorganisms than the ligands. HL² and its complexes were observed to show higher activity compared to H₂L¹ and its complexes, especially against Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli bacteria, and the fungus Candida tropicalis. It was found that 2a has a potent activity against S. aureus and E. coli, 2b against both Gram-positive bacteria (S. aureus and S. epidermidis) and 2c against S. aureus, S. epidermidis and E. coli compared to other complexes. Antiviral activity of the compounds was tested against Parainfluenza type-2 virus. In terms of antiviral effect, H₂L¹ showed higher activity than HL² and the Co(II) and Cu(II) complexes of HL² had the highest activity among the compounds, with rates of 62 and 64 %, respectively.

Redox pathways in the carnosine–manganese system mediated by semiquinone radicals

2026-05-19T16:16:04+02:00

The interaction of carnosine histidine-containing dipeptide with the semiquinone radical of 3,4-dihydroxybenzoic dianion in dimethyl sulfoxide solution under aerobic conditions was investigated in the present study. The interaction of dipeptide–manganese system with the same semiquinone was also studied under the identical conditions. The metal-binding and redox chemistry of these systems were investigated using electronic, ESR, ¹H-NMR spectroscopies and cyclic voltammetry. The in situ formal semiquinone radicals (extensively studied in previous works) were significantly modified upon addition of carnosine, as evidenced by the redistribution of the visible absorption bands and the change of the redox couples of the catecholic product. Subsequent influence of Mn ions induced further spectral and electrochemical changes, consistent with metal centered oxidation and formation of ligand-stabilized manganese species. Paramagnetic broadening in the ¹H-NMR spectra supported the presence of higher-valent Mn intermediates in solution. The combined data support a cooperative redox pathway in which semiquinone species mediate both peptide oxidation and Mn centered electron transfer. These results provide chemical insight into the understanding of multicomponent systems usually present in nature.

Dyeing of polyester fabric with disperse dye in a natural deep eutectic solvent as an eco-friendly medium

2026-06-11T16:15:12+02:00

The present study proposed a sustainable, cleaner, alternative, safer and environmentally friendly method for dyeing polyester fabric using a natural deep eutectic solvent as a dyeing medium. Besides enabling water conservation and reducing wastewater generation, the process also successfully eliminated the use of toxic and environmentally harmful auxiliaries. Dyeing performance, measured by CIELab and K/S values, was compared to conventional dyeing. The NADES dyeing method achieved higher K/S values and eliminated the need for additional auxiliaries, such as leveling and dispersing agents. The polyester fabric structure remains intact, as confirmed by physical property results. SEM analysis shows that the surface morphology of all polyester samples is smooth and uniform with no visible changes, indicating the dyeing process did not affect the fiber surface. Fastness ratings are consistent across all dyed polyester samples.

Synthetic studies of lignanes: Attempted synthesis of arctigenin and enterolactone

2026-06-28T20:28:32+02:00

A synthetic approach to bioactive lignans was devised, which relies on photocatalyzed [2+2] cycloaddition of cinnamyl cinnamates, followed by catalytic hydrogenolysis of C–C bond between two benzylic positions in the strained cycloadduct. However, while feasible in the model study, this approach could not be applied to the synthesis of bioactive derivatives arctigenin and enterolactone. Calculations were performed in order to rationalize the surprising lack of reactivity of substituted cinnamates and cyclobutane-fused γ-butyrolactone.

Silica modified with choline chloride/urea DES for ligand-free Cu(II) adsorption

2025-12-28T23:37:28+01:00

In this study, silica modified with a hydrophilic deep eutectic solvent (DES) composed of choline chloride and urea (DES-Si) was synthesized and evaluated for ligand-free Cu(II) removal from aqueous solutions. The DES-Si was successfully characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, nuclear magnetic resonance and elemental analysis, confirming the effective immobilization of DES onto the silica surface. Batch adsorption experiments demonstrated that DES-Si achieved a Cu(II) removal efficiency exceeding 95 % under optimal conditions (pH 8, initial Cu(II) concentration 5 mg L^-1, contact time 45 min, at 25 °C). The maximum adsorption capacity obtained from the Langmuir model was 17.54 mg g^-1, indicating strong affinity toward Cu(II) ions. Kinetic studies revealed that the adsorption process followed the pseudo-second-order model (R² = 0.9964), suggesting that the rate-
-limiting step is governed by surface interactions. Equilibrium data were well described by the Langmuir, Freundlich and Temkin isotherm models, with the Temkin model providing the best fit (R² = 0.9914). Comparative studies showed that Cu(II) removal using DES-Si without a chelating ligand was significantly more efficient than in the presence of 1,10-phenanthroline, highlighting the effectiveness of ligand-free adsorption. These findings demonstrate that DES-Si is a promising and environmentally friendly adsorbent for efficient Cu(II) removal from aqueous media.

Magnetic Ambrosia artemisiifolia-based biosorbent for Congo red removal from water: A circular economy approach

2025-11-25T21:23:32+01:00

Biomass-based biosorbents have demonstrated significant potential for removing synthetic organic dyes from water. This study explores the use of a magnetic biosorbent (Fe₃O₄/MB) derived from Ambrosia artemisiifolia, as a novel material for the removal of Congo red (CR) dye from aqueous solutions. The biosorption process was investigated by varying key parameters: pH, Fe₃O₄/MB dosage, CR concentration and temperature, followed by kinetic and equilibrium analyses. The structural properties of Fe₃O₄/MB were characterized using Fourier transform infrared spectroscopy. The CR concentration was monitored via UV–Vis spectrophotometry. Kinetic studies indicated that the biosorption of CR followed a PSO model (R² = 0.99). Isotherm analysis revealed that the Langmuir model best described the biosorption of CR (R² = 0.97), with a maximum adsorption capacity (Q_max) of 33.56 mg g^-1. The implementation of Fe₃O₄/MB supports sustainable water management and contributes to the development of greener and more circular industrial practices.

Errata

2026-08-01T22:23:09+02:00

Process optimization and economic calculation of photocatalytic degradation of methylene blue over sulfur-doped g-C3N4

2026-04-22T13:58:21+02:00

Sulfur doping has been considered an effective strategy to enhance the photocatalytic activity of graphitic carbon nitride (g-C₃N₄). However, there are no reports on the process optimization and economic calculation to determine the optimal photocatalytic parameters and compare the operating costs, respectively. In this work, sulfur-doped g-C₃N₄ (S/g-C₃N₄) was prepared in situ by a one-pot pyrolysis approach using thiourea as the precursor and sulfur source. S/g-C₃N₄ was characterized by various instrumental techniques. Response surface methodology (RSM) was employed to determine the optimal photocatalytic conditions for the degradation of Methylene blue (MB) over S/g-C₃N₄. A central composite design (CCD) with four factors at five levels was established, comprising 30 experimental runs. The optimal conditions were determined as an initial MB concentration of 27.6 mg L^-1, a catalyst dosage of 4.1 g L^-1, a solution pH of 8.7 and a reaction time of 127 min. Under these conditions, the predicted degradation efficiency could reach 99.94 %, while the experimental value was 99.5 %. Cost accounting indicated that the optimization substantially reduced direct costs, greatly improved equipment utilization, and enhanced operational flexibility. This work will lay key foundation for cost control and efficiency improvement in the scale-up application of g-C₃N₄-based photocatalysts.

Development of a sensitive extraction–spectrophotometric method for Cu(II) based on 1-(o-tolylamino)- and 1-(phenylamino)propane-2-thiol complexes

2026-05-07T17:31:24+02:00

The reactions of copper(II) with 1-(o-tolylamino)-propane-2-thiol (L¹, TPT) and 1-(phenylamino)-propane-2-thiol (L², PPT) was studied by the extraction-photometric method. The ligands were characterized with IR and NMR spectroscopy. The influence of aqueous phase pH on the formation of CuL₂ complexes and thermal decomposition were studied. Chloroform was chosen as the best extractant. A single extraction with chloroform extracted 98.6–97.9 % of Cu(II). The yield of CuL₂ was maximum at c_L = 9×10^-3 M and did not decompose for 48 h or more than 45 days after extraction. Phase volume ratios of 5:5–140:5 did not affect the recovery. The optimum acidity is in the range of pH_opt 3.1–5.3 (pH_form 1.0–7.1). The molar absorption coefficients are, ε_450-470, (3.4–3.8)×10⁴. Compliance with the fundamental law of light absorption is achieved at c_Cu(II) = 0.08 – 19 μg mL^-1. Thermal decomposition of CuL₂ complexes ([C₂₀H₂₈N₂S₂Cu] and [C₁₈H₂₄N₂S₂Cu]; Cu²⁺:L = 1:2) occurs stepwise due to the different stability of the Cu–S and Cu–N bonds. In the range of 65–135 °C, a mass loss of 2.78–2.84 % is observed, associated with the removal of weakly coordinated water. At 345–400 °C, profound destruction of the ligand occurs with the rupture of coordination bonds and the destruction of the chelate cycle (mass loss of 87.06–87.35 %). The proposed methods were successfully applied to determine copper in various complex samples.

Optimizing fabrication of pharmaceutical capsule shell: A factorial design of corncob-MCC/carrageenan/starch biofilm

2026-03-20T11:18:55+01:00

This study develops biodegradable soft-capsule films using carrageenan, tapioca starch, glycerol and microcrystalline cellulose (MCC) derived from corncob waste as a halal- and vegetarian-friendly alternative to gelatin. A 2³ factorial design evaluated the effects of carrageenan (15–25 wt. %), MCC (5–15 wt. %) and glycerol (10–20 wt. %) on tensile strength (TS), elongation (EL) and Young’s modulus (YM). The produced biofilms were characterized using mechanical testing, FTIR, XRD, SEM, TGA, disintegration tests and ANOVA. Mechanical performance varied widely among samples. Among the synthesized biofilms, sample 2 exhibited the highest TS (6.565 MPa) and YM (97.029 MPa), while sample 5 showed the greatest ductility and the shortest disintegration time, reaching approximately 20 % and 12 min, respectively, indicating rapid water-induced matrix breakdown associated with the hygroscopic nature of the polysaccharide-
-based system. Regression models showed R² values of 84.48, 97.17 and 94.18 % for TS, EL and YM, respectively. XRD confirmed an MCC crystallinity of 62.6 %. The TGA results confirm the films’ thermal stability and show moisture uptake and char residue consistent with those of the other analyses. Overall, the carrageenan–starch–MCC–glycerol system offers tuneable properties, although further optimization is required for moisture control and purity.

Impact of silica gel G on mechanical and microstructural properties of magnesium oxychloride

2026-04-15T16:26:33+02:00

Magnesium oxychloride cement (MOC), a type of Sorel’s cement, has gained renewed attention as a sustainable building material due to its low carbon footprint and energy consumption. However, its application in construction remains limited, primarily due to its inadequate moisture resistance and reduced early-age strength under elevated temperature conditions. This research investigates the impact of silica gel G (SG) on the properties of MOC. SG was incorporated into MOC at varying proportions (0–20 wt. % MgO) to form MOC–SG composites. The study evaluated the physical and mechanical properties of these composites, including setting time, moisture ingress resistance and compressive strength. Additionally, FTIR, PXRD, SEM-EDX and TGA analyses were conducted to examine the crystalline phases of the composites. SG acts as a binding agent, enhancing the strength and durability of the composite. This research demonstrates the potential of MOC–SG composites as promising sustainable building material. Results indicate that the addition of 5 % SG significantly improves the properties of MOC.