ELMERHI, Nada, ALKHATIB, Sara Awni, KUMAR, Sushil, MARTINEZ, Jose Ignacio, YASMEEN, Nabila, ALDAQQA, Najat Maher, BELEC, Blaž, PAPPA, Anna-Maria, SHETTY, Dinesh. Tuning core flexibility and curvature in azine-linked covalent organic frameworks for attomolar-level impedimetric sensing of glucose. 

Journal of the American Chemical Society.  2025, vol. 147, issue 43, 39247-39258,

Glucose serves as a key biomarker of metabolic health, requiring continuous and reliable monitoring. Nonenzymatic impedimetric sensors have emerged as a promising alternative to enzymatic glucose sensors, which dominate current clinical practice. However, their sensitivity is limited by weak molecular recognition and inefficient charge transport at the sensing interface. In this study, we tuned the core flexibility and curvature of azine-linked covalent organic frameworks (COFs) by substituting the central triazine ring in the C₃ symmetric building unit with a nitrogen atom. This modification maximized glucose–framework interactions, thereby enhancing signal transduction and detection sensitivity. The results confirmed the sensitivity and selectivity of the COFs toward glucose, with a linear response over a wide concentration range [1 aM–5 mM], surpassing previously reported glucose sensors. The sensors achieved a subattomolar limit of detection (LOD), with excellent stability and reproducibility compared to traditional enzymatic sensors, offering a simpler and more practical alternative for integration into wearable and implantable devices. Experimental findings are supported by molecular simulations, which reveals the mechanism of sensing and charge transfer dynamics. This work establishes a versatile design strategy for enzyme-free designed-to-purpose transducers, opening new pathways for ultrasensitive and selective molecular detection.

BASHRI, Mahira, KUMAR, Sushil, BHANDARI, Pallab, STEPHEN, Sasi, O'CONNOR, Matthew J., GABER, Safa, ŠKORJANC, Tina, FINŠGAR, Matjaž, LUCKACHAN, Gisha Elizabeth, BELEC, Blaž, et al. Hydrazone-linked covalent organic framework catalyst via efficient Pd recovery from wastewater. 

ACS applied materials & interfaces. 2025, vol. 17, issue 12, 17804-17812

Global consumption and discharge of palladium (Pd) have raised environmental concerns but also present an opportunity for the sustainable recovery and reuse of this precious metal. Adsorption has proven to be an efficient method for the selective recovery of Pd from industrial wastewater. This study investigated a hydrazone-linked covalent organic framework (Tfpa-Od COF) as a potential material for the high-affinity adsorption of Pd²⁺ ions from wastewater, achieving a K_d value of 3.62 × 10⁶ mL g^–1. The electron-rich backbone of the COF contributes to its excellent selective removal efficiency (up to 100%) and adsorption capacity of 372.59 mg g^–1. Furthermore, the Pd-adsorbed COF was evaluated as a sustainable catalyst for the Suzuki–Miyaura coupling reaction, demonstrating good catalytic conversion and recyclability. This work attempts to showcase a protocol for reusing waste palladium generated in water to fabricate heterogeneous catalysts and, thereby, promote the circular economy concept.

Sushil Kumar, Mahira Bashri, Safa Gaber, Jose I Martinez, Matthew J. O Connor, Sabu Varghese, Blaž Belec, Gisha Elizabeth Luckachan, Dinesh Shetty. Enhanced selective gold recovery from e-waste via synergetic hetero-atom controlled quasi-planar benzoxazine-based covalent organic frameworks

Materials Horizons, 2025, vol. 12, no. 20, 8472-8480,

Efficient and selective gold recycling from e-waste mixtures is crucial for advancing sustainability, the circular economy, and waste management objectives. However, the complex composition of e-waste and the underdeveloped practical potential of current adsorbents highlight the need for innovative sorbent development. Here, we present quasi-planar, benzoxazine-core-based two-dimensional covalent organic frameworks (COFs) with synergistic hetero-atom control across the network, achieved via a multi-component synthetic approach. These COFs, designed with specific gold interaction sites, were explored for the highly selective recovery of gold from real e-waste mixtures. By tuning the hetero-atom distribution, we achieved an impressive gold uptake capacity of 3467 mg g⁻¹ and over 92% selectivity in presence of 12 competing metal ions from e-waste leachate. These findings underscore the critical role of molecular-level engineering in COF sorbents, paving the way for the practical recovery of noble metals from e-waste.

ŽIVALJ, Edin, BELEC, Blaž, VALANT, Matjaž. Selective Room-Temperature Catalytic Decomposition of Hypochlorite to Oxygen and Chloride

 ACS Omega, 2025, vol. 10, issue 27, 29143-29153,

This study explores a low-temperature route for hydrogen production using chlorine and water via thermochemical cycles. We investigated the catalytic decomposition of hypochlorous acid—an intermediate in the cycle—using ruthenium and iridium oxide nanopowders under UV light. Both catalysts enabled oxygen release, while UV light favored chlorate formation. Ruthenium(IV) oxide showed higher catalytic efficiency across pH ranges and excellent stability and reusability, confirmed by XRD, Raman, and TEM analyses.

UČAKAR, Aleksander, KOCJAN, Andraž, BELEC, Blaž, KOŠIR, Janez, KALLIO, Tanja, MAČEK, Marjeta, ARAH, Bor, JENUŠ, Petra. The role of carbon presence on the strontium hexaferrite phase decomposition during pressureless spark plasma sintering (pSPS). 

Open ceramics. 2025, vol.100804, 1-21

Sr-hexaferrite ceramics were rapidly sintered via pressureless spark plasma sintering (pSPS) in a graphite crucible under vacuum. Modeling of the temperature profile revealed that the reductive environment caused phase decomposition into Sr-rich and Sr-deficient phases, degrading magnetic properties. Some new phases had lower melting points, shifting the sintering mechanism from solid-state to partial liquid-phase sintering.

BELEC, Blaž, KOSTEVŠEK, Nina, DELLA PELLE, Giulia, NEMEC, Sebastjan, KRALJ, Slavko, BERGANT MARUŠIČ, Martina, GARDONIO, Sandra, FANETTI, Mattia, VALANT, Matjaž. Silica coated Bi2Se3 topological insulator nanoparticles : an alternative route to retain their optical properties and make them biocompatible. Nanomaterials. Nanomaterials.  2023, vol. 13, no. 5,  1-14, 

Bi₂Se₃ nanoparticles exhibit strong photothermal effects due to localized surface plasmon resonance from topological surface states. To improve stability and biocompatibility, we coated the nanoparticles with silica instead of ethylene glycol, which was shown to mask optical properties and be cytotoxic. Silica-coated Bi₂Se₃ retained photothermal performance (except at ~200 nm thickness) and showed significantly improved heat conversion, requiring much lower concentrations. In vitro tests confirmed their biocompatibility, making them promising for medical applications.

MAVRIČ, Andraž, ŽERJAV, Gregor, BELEC, Blaž, ROŠKARIČ, Matevž, FINŠGAR, Matjaž, PINTAR, Albin, VALANT, Matjaž. Structural disorder of AlMg-oxide phase supporting Cu/ZnO catalyst improves efficiency and selectivity for CO2 hydrogenation to methanol. 

ChemCatChem. Jul. 2023, vol. 15, issue 13, str. 1-8, ilustr. ISSN 1867-3880.

The performance of the Cu/ZnO catalyst system with the AlMg-oxide phase is studied for CO₂ hydrogenation to methanol. The catalyst is prepared by thermal treatment of the hydrotalcite phase containing intimately mixed metal cations in the hydroxide form. CuO in the presence of ZnO and disordered AlMg-oxide phase gets easily reduced to Cu during the hydrogenation reaction. Its catalytic activity at relatively low Cu metal content (∼14 at.%) remains stable during 100 hours on stream at 260 °C with constant space-time yield for methanol (∼1.8 g_MeOH g_cat⁻¹ h⁻¹) and high methanol selectivity (>85 %) The improved performance is attributed to the neutralization of surface acidity, increased number of weak basic sites in the disordered phase, and lower tendency for coke formation.

RMUŠ, Jelena, BELEC, Blaž, MILANOVIĆ, Igor, FANETTI, Mattia, GARDONIO, Sandra, VALANT, Matjaž, KURKO, Sandra V. Composites of transition metal dichalcogenides and topological insulators as catalytic materials for HER. 

Journal of energy storage. Sep. 2023, vol. 68,  1-11

We developed composite catalysts combining MoS₂, a transition metal dichalcogenide, with Bi₂Se₃, a topological insulator, to improve hydrogen evolution reaction (HER) activity. Composites were prepared by mechanical milling, high-power sonication, and spin-coating using hydrothermally synthesized precursors. Structural and morphological features were linked to electrochemical performance through impedance spectroscopy and voltammetry. Mechanical milling induced the greatest defect density, significantly enhancing catalytic activity and lowering the overpotential for 10 mA/cm² current density by up to 50 mV. Bi₂Se₃ facilitates electron transfer to MoS₂, reducing charge transfer resistance by 25 Ω, highlighting the synergistic effect in boosting HER efficiency.

MEHTA, Akansha, RATHER, Rayees Ahmad, BELEC, Blaž, GARDONIO, Sandra, FANG, Ming, VALANT, Matjaž. Plastic waste precursor-derived fluorescent carbon and construction of ternary FCs@CuO@TiO2 hybrid photocatalyst for hydrogen production and sensing application. 

Energies. 2022, vol. 15, iss. 5, str. 1-16

This study presents a cost-effective and eco-friendly approach linking plastic waste management, wastewater treatment, and renewable hydrogen generation. Fluorescent carbon nanoparticles (FCs) were hydrothermally synthesized from low-density polyethylene (LDPE) waste and demonstrated sensitive detection of Cu²⁺ ions in water with a low detection limit of 86.5 nM. The Cu²⁺-loaded FCs were combined with TiO₂ to form a ternary FCs@CuO@TiO₂ composite, which exhibited enhanced photocatalytic hydrogen production under simulated solar light, achieving an H₂ evolution rate of ~1800 μmol g⁻¹ and a solar-to-hydrogen efficiency of ~0.95%. This performance results from the fluorescent properties of FCs and the synergistic CuO-TiO₂ interaction, improving light absorption and charge separation, offering a promising sustainable route for waste valorization and clean energy.

D'ELIA, Alessandro, REZVANI, S. J., ZEMA, Nicola, ZUCCARO, F., FANETTI, Mattia, BELEC, Blaž, LI, B. W., ZOU, C. W., SPEZZANI, Carlo, SACCHI, Maurizio, MARCELLI, Augusto, CORENO, Marcello. Stoichiometry and disorder influence over electronic structure in nanostructured VOx films.

 Journal of nanoparticle research. 2021, vol. 23, iss. 1, 1-9

We investigate how nanoparticle size and stoichiometry influence the local atomic structure of VOx nanostructured films using in situ X-ray absorption near-edge structure (XANES) spectroscopy. Focusing on VO₂, we reveal that nanoscale size disrupts the bulk ligand symmetry, creating a continuum of distorted atomic configurations. This leads to stoichiometry-dependent disorder in the ligand matrix and modulation of the electronic structure. Our findings open pathways to novel disordered VOx phases and offer a powerful approach to study complex oxide nanomaterials.

JENUŠ, Petra, UČAKAR, Aleksander, REPŠE, Sandra, SANGREGORIO, Claudio, PETRECCA, Michele, ALBINO, M., CABASSI, R., DE JULIÁN FERNÁNDEZ, Cesár, BELEC, Blaž. Magnetic performance of SrFe12O19−Zn0.2Fe2.8O4 hybrid magnets prepared by Spark Plasma Sintering. 

Journal of physics. D, Applied physics. 2021, vol. 54, no. 20, 1-8, 

In the last few years, significant effort has again been devoted to ferrite-based permanent magnet research due to the so-called rare-earth crisis. In particular, a quest to enhance ferrites maximum energy product, BH_max, is underway. Here, the influence of composition and sintering conditions on the microstructure and consequently magnetic properties of strontium ferrite-based hybrid composites was investigated. The powder mixtures consisted of hydrothermally synthesised Sr-ferrite with hexagonally shaped platelets with a diameter of 1 μm and thickness up to 90 nm, and a soft magnetic phase in various ratios. Powders were sintered using a spark plasma sintering furnace. The crystal structure, composition and microstructure of the starting powders and hybrid magnets were examined. Their magnetic properties were evaluated by vibrating sample magnetometer, permeameter and by single-point-detection measurements.

DE JULIÁN FERNÁNDEZ, Cesár, SANGREGORIO, Claudio, DE LA FIGUERA, Juan, BELEC, Blaž, MAKOVEC, Darko, QUESADA, Adrian. Progress and prospects of hard hexaferrites for permanent magnet applications : topical review. 

Journal of physics. D, Applied physics. 2021, vol. 54, no. 15, 1-30.

Permanent magnets based on hard hexaferrite represent the largest family of magnets being used today by volume. They generate moderate remanence induction, but present crucial advantages in terms of availability, cost, resistance to demagnetization and corrosion and absence of eddy current losses. As a consequence, ferrites are the most logical candidate for substitution of rare-earths in selected applications that do not demand the best performing magnets. If the remanence of ferrite-based magnets was to be improved, even mildly, the door to a larger scale substitution could be opened. In this framework, we review here current strategies to improve the properties of hexaferrites for permanent magnet applications. We first discuss the potential of exploring the nanoscale. Second, progress related to controllably doping hexaferrites is revised. Third, results achieved by fabricating hard-soft magnetic composites using ferrites as the hard phase are presented. Finally, future prospects and new potential end applications for ferrite magnets are discussed

D'ELIA, Alessandro, CEPEK, Cinzia, SIMONE, Monica de, MACIS, Salvatore, BELEC, Blaž, FANETTI, Mattia, PISERI, Paolo, MARCELLI, Augusto, CORENO, Marcello. Interplay among Work Function, electronic structure and stoichiometry in nanostructured VOxVOx films. 

PCCP. Physical chemistry chemical physics : a journal of European Chemical Societies. 2020, vol. 22, iss. 11,6282-6290, i

We synthesized vanadium oxide nanostructured films with controlled stoichiometry and work function (3.7–7 eV) using room-temperature supersonic cluster beam deposition. Through in situ Auger and valence-band photoemission spectroscopy, we revealed how oxygen content and hybridization of V 3d, O 2p, and V 4s states shape the electronic structure. Our findings show that precise stoichiometry control enables tuning of the work function, with nanoscale quantum confinement further enhancing it beyond bulk values—key for optimizing oxide materials in electronic and energy applications.

BELEC, Blaž, FERFOLJA, Katja, GORŠAK, Tanja, KOSTEVŠEK, Nina, GARDONIO, Sandra, FANETTI, Mattia, VALANT, Matjaž. Inherent surface properties of adsorbent-free ultrathin Bi2Se3 topological insulator platelets. 

Scientific reports. 2019, vol. 9, 190571-1-19057-9,

We demonstrate a novel hydrothermal method for synthesizing ultra-thin hexagonal Bi₂Se₃ platelets without using organic reactants, resulting in particles with truly clean surfaces. This allowed, for the first time, direct measurement of their intrinsic surface charge and optical properties, including localized surface plasmon resonance linked to topological surface states. The clean synthesis approach overcomes limitations of conventional solvothermal methods and opens new possibilities for studying and applying Bi₂Se₃ in plasmonic and topological materials research.

MAKOVEC, Darko, GYERGYEK, Sašo, GORŠAK, Tanja, BELEC, Blaž, LISJAK, Darja. Evolution of the microstructure during the early stages of sintering barium hexaferrite nanoplatelets. 

Journal of the European ceramic society.  2019, vol. 39, 4831-4841,

This study explores how the distinct iron-rich structure of hydrothermally synthesized barium hexaferrite nanoplatelets influences microstructural development during sintering. Through advanced microscopy and magnetic analysis, we show that fusion of nanoplatelets drives grain thickening, often leading to planar defects and Fe₂O₃ formation. Notably, Sc-substitution induces superstructural ordering and exaggerated grain growth, providing valuable insight for tailoring hexaferrite ceramics.

GORŠAK, Tanja, MAKOVEC, Darko, JAVORNIK, Uroš, BELEC, Blaž, KRALJ, Slavko, LISJAK, Darja. A functionalization strategy for the dispersion of permanently magnetic barium-hexaferrite nanoplatelets in complex biological media. Colloids and surfaces. A, Physicochemical and Engineering Aspects. 2019, vol. 573, 119-127. I

We present a breakthrough strategy for stabilizing nanoparticles in complex biological environments—a key challenge in nanomedicine. Using a covalent dextran coating anchored via a silane linker, we ensured long-term colloidal stability even for highly agglomeration-prone barium hexaferrite nanoplatelets. This multi-step method overcomes limitations of conventional coatings and enables the use of magnetic nanoplatelets in biomedical applications, with stability verified by TEM, NMR, and dynamic light scattering.

MAKOVEC, Darko, KOMELJ, Matej, DRAŽIĆ, Goran, BELEC, Blaž, GORŠAK, Tanja, GYERGYEK, Sašo, LISJAK, Darja. Incorporation of Sc into the structure of barium-hexaferrite nanoplatelets and its extraordinary finite-size effect on the magnetic properties. Acta materialia. [Print ed.]. Jun. 2019, vol. 172, 84-91

This study reveals a striking reversal in magnetic behavior between bulk and nanoscale barium hexaferrite. While Sc-substitution reduces magnetization in bulk, it significantly enhances it in nanoplatelets. Using atomic-resolution microscopy and simulations, we show that this unexpected boost in saturation magnetization arises from unique two-dimensional magnetic ordering at the nanoscale—offering new insights for engineering high-performance magnetic nanomaterials.

MAKOVEC, Darko, BELEC, Blaž, GORŠAK, Tanja, LISJAK, Darja, KOMELJ, Matej, DRAŽIĆ, Goran, GYERGYEK, Sašo. Discrete evolution of the crystal structure during the growth of Ba-hexaferrite nanoplatelets. 

Nanoscale. 2018, vol. 10, iss. 30, 14480-14491, 

We investigated how the crystal structure of barium hexaferrite nanoplatelets evolves during low-temperature hydrothermal synthesis. Starting with ultra-thin SRS*-structured platelets, we observed discrete growth via RS segment additions, directly impacting their magnetic properties. This stepwise structural adaptation links nanoscale morphology with magnetism, offering insights for designing functional magnetic nanomaterials for advanced technologies.

BELEC, Blaž, DRAŽIĆ, Goran, GYERGYEK, Sašo, PODMILJŠAK, Benjamin, GORŠAK, Tanja, KOMELJ, Matej, NOGUÉS, Julio J., MAKOVEC, Darko. Novel Ba-hexaferrite structural variations stabilized on the nanoscale as building blocks for epitaxial bi-magnetic hard/soft sandwiched maghemite/hexaferrite/maghemite nanoplatelets with out-of-plane easy axis and enhanced magnetization. 

Nanoscale. 2017, vol. 9, no. 44,  17551-17560

Atomic-resolution microscopy revealed a unique nanoscale structure of barium hexaferrite (BHF) nanoplatelets, enabling strong uniaxial magnetic anisotropy. By epitaxially coating them with maghemite layers, we formed uniform M/BHF/M composite nanoplatelets with significantly enhanced magnetization. These engineered nanostructures hold promise for advanced magnetic applications requiring directional alignment and improved performance.

PLOHL, Olivija, KRAFT, Marco, KOVAČ, Janez, BELEC, Blaž, PONIKVAR-SVET, Maja, WÜRTH, Christian, LISJAK, Darja, RESCH-GENGER, Ute. Optically detected degradation of NaYF4:Yb,TmNaYF4:Yb,Tm-based upconversion nanoparticles in phosphate buffered saline solution.

 Langmuir. 2017, vol. 33, no. 2, 553-560. 

This proof-of-concept study evaluates analytical methods to monitor the stability of β-NaYF₄:Yb³⁺,Tm³⁺ upconversion nanoparticles in phosphate-buffered saline. By combining fluoride ion release measurements, XPS surface analysis, and fluorescence techniques, we identified the 800 nm luminescence lifetime as the most effective indicator of nanoparticle stability and surface chemistry changes under physiological conditions.