A novel approach to low-temperature synthesis of cubic HfO2 nanostructures and their cytotoxicity

Abstract

The development of a strategy to stabilise the cubic phase of HfO2 at lower temperatures is necessary for the emergence of unique properties that are not realised in the thermodynamically stable monoclinic phase. A very high temperature (>2600 °C) is required to produce the cubic phase of HfO2, whereas the monoclinic phase is stable at low temperature. Here, a novel rapid synthesis strategy was designed to develop highly crystalline, pure cubic-phase HfO2 nanoparticles (size <10 nm) using microwave irradiation. Furthermore, the as-prepared nanoparticles were converted to different morphologies (spherical nanoparticles and nanoplates) without compromising the cubic phase by employing a post-hydrothermal treatment in the presence of surface modifiers. The cytotoxicities and proliferative profiles of the synthesised cubic HfO2 nanostructures were investigated over the MCF-7 breast cancer cell line, along with caspase-3/7 activities. The low-temperature phase stabilisation was significantly attributed to surface imperfections (defects and deformations) induced in the crystal lattice by the desirable presence of Na2S·xH2O and NaOH. Our work provides unprecedented insight into the stabilisation of nanoscale cubic-phase HfO2 in ambient environments; the method could be extended to other challenging phases of nanomaterials.

Enhanced Thermo‐Mechanical Stiffness, Thermal Stability, and Fire Retardant Performance of Surface‐Modified 2D MoS2Nanosheet‐Reinforced Polyurethane Composites

“…As seen from Figure , the survey spectrum of MoS 2 exhibited the characteristic peaks of Mo (3d, 3p, 4p), S (2p), O (1s), and C (1s), whereas the new peak of N (1s) (probably arise from melamine) was noticed in case of M‐MoS 2 . The characteristic peak of C 1s and O 1s can be possibly ascribed to adsorbed PEG molecules on MoS 2 nanosheets . The increase in C1s peak intensity and appearance of N1s peak confirmed the incorporation of melamine within the MoS 2 nanosheets via intercalation as observed in XRD patterns.…”

“…Multigram‐scale synthesis of 2D‐MoS 2 nanosheets (from now abbreviated as MoS 2 ) was carried out using a hydrothermal process, with slight modification from the previous method . In the typical method, 5 g of sodium molybdate dihydrate was dissolved in 85 mL of deionized water, followed by the addition of 5 g of PEG.…”

Coordination‐Driven Hierarchical Assembly of Hybrid Nanostructures Based on 2D Materials

“…Therefore, the Mo atoms at the S vacancies were exposed, which could function as the coordination centers to bond with ligands, as shown in Figure a. With this strategy, various kinds of building blocks that involved sulfur‐, oxygen‐, nitrogen‐containing functional groups were employed as ligands to coordinate with MoS 2 through S vacancies, resulting in multifunctional hybrid nanostructures …”

“…Similar to the S atoms, the O and N atoms also contained lone pair electrons. Therefore, molecules possessing O‐ and N‐containing functional groups could also coordinate with MoS 2 at the S vacancies, constructing various hybrid nanostructures …”

“…Despite these merits, the main challenge to constructing reliable TMDs‐based hybrid nanostructure for biomedical applications was building strong interfacial interactions because of the chemical inertness of TMDs. With the aid of coordination bond, various types of functional molecules and biomolecules were hybridized with TMDs nanosheets for enhanced biosensing, antibacterial activity, etc., along with good stability . Based on these hybrid nanostructure, additional drugs and functional building blocks could be further assembled (e.g., Figure e), extending their biomedical applications with new functions and properties …”