Faculty of Technology and Metallurgy
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Item type:Publication, Reflectivity from electrochemically protected Nb surfaces(Engineering Society of Corrosion, 2015-06-15)Corrosion resistance of fine mechanically polished and electro-polished Nb surfaces were tested by elliposmetric measurements the reflectivity at various angle of incidence. The same measurements were also repeated on electro-polished Nb surface anodic ally oxidized in 1M H2SO4 during 30 s in the potential/voltage range from 0 to 100 V. From the minimum value of measured reflectivity parallel to plane of incidence, the Brewster angle for each investigated sample was determined. The simultaneous measurements of corrosion parameters Brewster angle have shown that the values of Brewster's angle should be used for fast testing the quality of protected metal surfaces. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Photoelectrochemical Study of Anodically Formed Oxide Films on Niobium Surfaces(CROATIAN CHEMICAL SOC, 2010-07)The semi-conducting properties of electrochemically formed oxide films onto Nb surface in 1 M H(2)SO(4) have been studied by photo-electrochemical measurements. By cyclic voltammetry the I vs. E profile of active/passive transition of Nb electrode has been recorded in the potential region from -0.5 to 8 V (SCE). The photocurrent maximums, band gap energies and flat potentials of anodic oxide films formed by stepwise rising of anodic voltage from 10 to 100 V on Nb electrode have been determined. Using Raman spectroscopy the development of crystalline structure in the films with different resultant thickness has been analysed. The semi-conducting properties of niobium oxides with development of crystalline structure have been discussed in term of breakdown processes in the films. The thresholds of transition from amorphous to crystalline form of anodic oxide films depending of applied voltages and time of polarization have been determined. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, TOWARDS SUSTAINABLE EXTRACTION OF OIL FROM APRICOT KERNELS(2026-02-12); Deep eutectic solvents (DES) are gaining attention as green alternatives to conventional volatile organic solvents for the extraction of natural products. Their ease of preparation from inexpensive, biodegradable components, along with low toxicity and tunable physicochemical properties, makes them promising candidates for designing eco-efficient extraction processes. In this work, four DES systems based on choline chloride (ChCl) as hydrogen bond acceptor and different hydrogen bond donors glycerol, lactic acid, acetic acid, and glucose were synthesized and evaluated as co-solvents with n-hexane for the ultrasonic-assisted extraction of oil from apricot kernels. The DESs were characterized in terms of pH, density (δ), viscosity (μ), and electrical conductivity (σ) to better understand how their physical properties influence extraction performance. Oil extraction experiments demonstrated that the DES composition and its physical properties have a marked impact on extraction efficiency. Under optimized ultrasonic conditions, the use of ChCl:AA (1:2) as a co-solvent with n-hexane yielded the highest oil recovery of 26.62%, surpassing pure n-hexane, which afforded only 24.10% under the same conditions. In contrast, ChCl:GLY (1:2), ChCl:LA (1:2), and ChCl:GLU (2:1) resulted in lower oil yields of 18.95%, 22.23%, and 13.26%, respectively. The superior performance of ChCl:AA is attributed to its combination of relatively low viscosity, and high conductivity, which collectively promote enhanced mass transfer, more efficient cell disruption, and improved solubilization of lipophilic components when assisted by ultrasonic cavitation. Overall, this study highlights the importance of tailoring the physicochemical properties of DES to maximize performance and demonstrates the potential of DES n-hexane systems as green, efficient, and scalable alternatives to conventional solvent based processes for the valorization of apricot kernel oil and other plant derived lipids. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Optimization of Oil Extraction Process from White Mustard Seeds Using Response Surface Methodology(National and University Library of the Republic of Srpska, 2024-02-21); ; In this study, response surface methodology (RSM) was used for the determination of the effect of two process parameters (extraction temperature and extraction time) and their interaction on the yield of the total extract from white mustard seeds (Sinapis alba l.), as well as the creation of a mathematical model, 3D response surface, and the establishment of an optimal extraction region. Ethanol 96% as a green solvent was employed to separate biological compounds from white mustard (Sinapis alba l.) seeds by applying ultrasound-assisted extraction (UAE). UAE was performed at the temperature of 25, 30, and 35℃ for a duration of 30, 60, and 90 min. UAE as a modern extraction technique showed great performance, while the ethanol solvent provided a high yield of compounds. The utilized RSM design adequately fit the experimental data with a high coefficient of determination (R2= 0.9365) and low mean absolute error (MAE= 1.12242). Estimated effects for the yield of the total extract showed that the extraction time, the temperature, and the interaction between time and temperature influenced positively, while the time-squared and the temperature-squared influenced negativity on the yield of the total extract. Analysis of variance showed that 2 effects have P-values less than 0.05. The optimal yield of the total extracted oil was 15.19% at the temperature of 35℃ for a duration of 70.3 min. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Photoelectrochemical Study of Anodically Formed Oxide Films on Niobium Surfaces(CROATIAN CHEMICAL SOC, 2010-07) - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Electrochemical sensors based on polymer-modified screen-printed graphene electrodes for the detection of pharmaceuticals in aquatic environments(SAGE Publications, 2025-10-06); - Some of the metrics are blocked by yourconsent settings
Item type:Publication, REDUCING THE BAND-GAP ENERGY OF TiO2 AS A CRUCIAL OBJECTIVE IN GREEN PHOTOCATALYSIS(Ss Cyril and Methodius University in Skopje, Faculty of Technology and Metallurgy, 2025-06-12)Perica Paunović, Anita Grozdanov, Petre Makreski, Martin Stojčevski, Kiril Stoimčev, Gorazd ČepiševskiGreen photocatalysis focuses on developing processes to address various environmental challenges, such as the treatment of contaminated water and air, the generation of renewable energy, biomass management, carbon monoxide oxidation, and organic synthesis. TiO2 nanoparticles are relatively inexpensive, non-toxic, and chemically stable. They are available in diverse structural forms and exhibit unique semiconductive properties, making them the most widely utilized photocatalysts in this domain. TiO2 has a wide array of applications in green photocatalysis, including i) photocatalytic remediation and ii) the development of alternative, sustainable energy sources. A significant challenge in modern green photocatalysis is the reduction of the band gap energy (Eg), which is essential for determining the suitability of materials for photocatalytic activity. Decreasing Eg enables TiO2 to effectively harness visible light rather than being limited to ultraviolet light. This study investigates the structural changes and subsequent reduction in Eg resulting from two types of TiO2 modification: i) ionizing irradiation and ii) the incorporation of carbon nanotubes. We synthesized TiO2 nanoparticles using our proprietary sol-gel method, followed by thermal treatment at 400 °C. Structural changes were analyzed using X-ray powder diffraction (XRPD) and Raman spectroscopy, while the band gap energy of the samples was assessed through UV-Vis spectroscopy. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Polymer-modified screen-printed electrode-based electrochemical sensors for doxorubicin detection(The Association of South-East European Electrochemists (ASEEE), 2025-02-27)Iva Dimitrievska, Perica Paunovikj, Anita GrozdanovIn the last decade, intensive research has been performed in the field of analytical electrochemistry, seeking designs of electrochemical sensors capable of providing better analytical characteristics in terms of sensitivity, selectivity, reliability, ease of fabrication and use, and low cost, especially for pharmaceutical drug monitoring. Our research has primarily focused on developing screen-printed electrode-based sensors and their application as electrochemical platforms for drug determination and monitoring, specifically emphasizing their suitability for surface modification. A commercial screen-printed graphene electrode was used as the electrochemical sensing component, which was subsequently modified with polymers, such as polyvinylidene fluoride and chitosan. All studied electrodes were tested using a doxorubicin hydrochloride (DOX) solution with a concentration of 0.002 mol L-1 dissolved in 0.1 mol L-1 phosphate-buffered saline at pH 6.7. Cyclic voltammetry was used as an electrochemical characterization technique to gather data on all tested electrodes' electrochemical activity. The morphological characterization of the electrodes was done using scanning electron microscopy. The changes in the electrolyte during the electrochemical measurements were followed through ultraviolet-visible spectroscopy. The modified electrodes demonstrated a favorable electrochemical response to DOX and exhibited higher electrical conductivity than the commercial one. The characterization results indicated that the Ch-modified electrode exhibited excellent electrochemical conductivity and demonstrated strong electrochemical performance. The evaluations of this electrode comprised the definition of the lowest limit of detection and limit of quantification among the tested electrodes, with values of 9.822 and 32.741 µmol L-1, respectively, within a linear concentration range from 1.5 to 7.4 µmol L-1. Additionally, the electrodes showed excellent repeatability, stability, and reproducibility, confirming their suitability for sensitive DOX detection. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Influence of irradiation treatment on sensing performances of screen-printed electrodes aimed for doxorubicin monitoring(Association of South-East European Electrochemists (ASEEE), 2025-05-05)Perica Paunovikj, Iva Dimitrievska, Marija Katerina Paunovikj, Marija Mitevska, Anita GrozdanovThe subject of study is the development of nanosensors based on carbon nanotubes (CNTs) and polyaniline (PANI) aimed at effective detection and monitoring of doxorubicin - a chemotherapy drug used in the treatment of different types of cancer. The main goal is the design of nanosensors that provide precise and reliable detection and monitoring of doxorubicin, providing an effective approach to monitor drug levels during treatment. The research was carried out on the screen-printed electrodes (SPE) with a working electrode of commercial CNTs and PANI and their modification by irradiation with electron irradiation (50 kGy). The structural changes resulting from the e-beam irradiation were observed by scanning electron microscopy, Raman and FTIR spectroscopy, and thermogravimetric analysis. An electrochemical study employing cyclic voltammetry was done to characterize and test the performance of the nanosensors. Modification with electron irradiation was shown as an effective approach to improve the sensing characteristics of the studied SPE, resulting in a lower limit of detection for the modification. The irradiated SPEs exhibit a limit of detection of 12.674 µmol L⁻¹ for the modified multi-walled CNT (MWCNT) electrode and 12.712 µmol L⁻¹ for the modified PANI electrode, compared to 12.773 µmol L⁻¹ for the MWCNT and 12.712 µmol L⁻¹ for the PANI commercial electrodes.