The aim of this work is to study the physical-chemical, mechanical, and biocompatible properties of hydroxyapatite obtained by hydrothermal synthesis, at relatively low temperatures and high pressures, starting from natural sources (Rapana whelk shells), knowing that these properties influence the behavior of nanostructured materials in cells or tissues. Thus, hydroxyapatite nanopowders were characterized by chemical analysis, Fourier-transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). In vitro studies on osteoblast cell lines (cytotoxicity and cell proliferation), as well as preliminary mechanical tests, have been performed. The results showed that the obtained powders have a crystallite size below 50 nm and particle size less than 100 nm, demonstrating that hydrothermal synthesis led to hydroxyapatite nanocrystalline powders, with a Ca:P ratio close to the stoichiometric ratio and a controlled morphology (spherical particle aggregates). The tensile strength of HAp samples sintered at 1100 °C/90 min varies between 37.6–39.1 N/mm². HAp samples sintered at 1300 °C/120 min provide better results for the investigated mechanical properties. The coefficient of friction has an appropriate value for biomechanical applications. The results of cell viability showed that the cytotoxic effect is low for all tested samples. Better cell proliferation is observed for osteoblasts grown on square samples.

Metal oxide nanoparticles (MONs) are particles with at least one dimension in the nanoscale range (1–100 nm). Their unique properties, significantly different from their bulk counterparts, make them promising materials for a wide range of applications in fields such as medicine, electronics, catalysis, environmental remediation, and energy storage. The precise control of MONs’ properties, including size, shape, composition, crystallinity, and surface chemistry, is significant for optimizing their performance. This study aims to investigate the characteristics of synthesis methods of MONs. Correlation between synthesis parameters and properties highlights that creating nanomaterials with defined and controlled dimensions is a complex task that requires a deep understanding of various factors. Also, this study presents a model with adaptive parameters for synthesis conditions to acquire desired nanometric scale for particles size, which represents an essential task.

Core–shell nanoparticles are functional materials with tailored properties, able to improve the requirements of various applications. Both core and shell components can be inorganic or organic, and there are numerous studies in this field regarding their synthesis methods, properties, and applications. This review aims to study core–shell nanostructures with Fe₃O₄ cores and different shell types, observing their antibacterial and anticancer properties. By the type of coating, Fe₃O₄ core–shell nanoparticles (NPs) are classified into four categories: metal-coated NPs, metal-organic framework (MOF) coated NPs, metal oxide coated NPs, and polymer-coated NPs. Each category is briefly presented, emphasizing anticancer or antibacterial properties and specific applications (cancer diagnosis or therapy, drug carrier). Moreover, synthesis methods and particle size for both core and shell nanostructures, as well as the magnetic properties of the final core–shell material, are summarized in this review. Most of the consulted papers discussed sphere-like core–shell nanoparticles obtained by chemical methods such as coprecipitation, hydrothermal, and green synthesis methods using plant extract. These types of core–shell nanoparticles could be used as drug nanocarriers for tumor-targeted drug delivery, hyperthermia treatment, or contrast agents. Further work needs to be conducted to understand nanoparticles’ interaction with living cells and their traceability in the human body.

The aim of this paper was to investigate the structure and thermal properties of zirconia ceramics co-doped with rare earth (RE) elements in equimolar concentrations. We prepared (1 − x)ZrO₂ − x(yLa₂O₃ + yNd₂O₃ + ySm₂O₃ + yGd₂O₃ + yYb₂O₃) (x = 0.2; y = 0.2) powders by a hydrothermal method in mild conditions (200 °C, 2 h, 60–100 atm.) The powder was analyzed by XRD, SEM-EDAX, BET, and FT-IR after synthesis and heat treatments at 1200 °C and 1500 °C. The samples exhibit good thermal stability, with a single cubic phase presented after heat treatment at 1500 °C. The compound exhibits a low thermal conductivity (0.61 W·m⁻¹·K⁻¹), a low heat capacity (0.42 J·g⁻¹K⁻¹), and a low thermal diffusivity (0.34 mm²·s⁻¹). The values are lower than reported for conventional RE-doped zirconia.

According to literature data, different micro- and nanopowders have been used as a partial substitute for cement mortar due to their small size and large specific surface area. The aim of the work is to develop innovative materials based on cement mortar with antibacterial and self-cleaning properties, which can be used in the long-term maintenance of clean spaces. First, zinc oxide/hydroxyapatite (ZnO/Hap) powder denoted as ZH was synthesized by the hydrothermal method; then it was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM)/ energy dispersive spectroscopy (EDS), and adsorption–desorption isotherms. The second step was the cement mortar preparation: one plain, denoted E, and one with ZH powder inside, denoted MZH. Both mortars were subjected to self-cleaning and antibacterial tests. In the self-cleaning tests, two concentrated solutions of rhodamine B and methylene blue were used. MZH showed a better decolorating after 24 h of UV light than plain cement mortar denoted E for both solutions. In order to highlight the antibacterial effect of cement mortars on some strains of Gram-positive and Gram-negative bacteria, the direct contact method was used. The study revealed that, after 24 h of incubation, the planktonic growth of the E. coli strain is significantly inhibited in the presence of the MZH sample, compared to the control strain. MZH cement mortar exhibits a better growth inhibitory property than the plain cement mortar E.

Barium carbonate (BaCO₃) nanoparticles were synthesized by a facile hydrolysis route using BaCl₂ and KOH in aqueous solution, with atmospheric CO₂ as the carbonate source, without external agents. Their structural and morphological properties were investigated by XRD, ATR-FTIR, SEM, and BET, confirming the formation of a pure orthorhombic witherite phase with rod-like morphology and different surface specific areas. The crystallite size increased from 52 to 86 nm with higher precursor concentration and synthesis temperature, as predicted by a regression model correlating synthesis parameter with particle growth. When incorporated into polymer (PVC) and geopolymer (GP) matrices, BaCO₃ enhanced the photocatalytic degradation of methylene blue (MB) under solar light, with GP@Nano-BaCO₃ achieving a higher rate constant compared to PVC@Nano-BaCO₃. The results highlight that the synthesis strategy yields well-defined BaCO₃ nanoparticles with tunable structural features and promising photocatalytic potential when integrated in functional polymer matrices. Future work will address doping strategies and testing in real wastewater conditions. Overall, this synthesis strategy offers a reproducible and environmentally friendly route to BaCO₃ nanoparticles with potential applications in hybrid materials for visible light-driven environmental remediation.