MXenes with ordered triatomic-layer borate polyanion terminations.

Surface terminations profoundly influence the intrinsic properties of MXenes, but existing terminations are limited to monoatomic layers or simple groups, showing disordered arrangements and inferior stability. Here we present the synthesis of MXenes with triatomic-layer borate polyanion terminations (OBO terminations) through a flux-assisted eutectic molten etching approach. During the synthesis, Lewis acidic salts act as the etching agent to obtain the MXene backbone, while borax generates BO2- species, which cap the MXene surface with an O-B-O configuration. In contrast to conventional chlorine/oxygen-terminated Nb2C with localized charge transport, OBO-terminated Nb2C features band transport described by the Drude model, exhibiting a 15-fold increase in electrical conductivity and a 10-fold improvement in charge mobility at the d.c. limit. This transition is attributed to surface ordering that effectively mitigates charge carrier backscattering and trapping. Additionally, OBO terminations provide Ti3C2 MXene with substantially enriched Li+-hosting sites and thereby a large charge-storage capacity of 420 mAh g-1. Our findings illustrate the potential of intricate termination configurations in MXenes and their applications for (opto)electronics and energy storage.

Surface Modification and Enhancement of Ferromagnetism in BiFeO3 Nanofilms Deposited on HOPG.

BiFeO3 (BFO) films on highly oriented pyrolytic graphite (HOPG) substrate were obtained by the atomic layer deposition (ALD) method. The oxidation of HOPG leads to the formation of bubble regions creating defective regions with active centers. Chemisorption occurs at these active sites in ALD. Additionally, carbon interacts with ozone and releases carbon oxides (CO, CO2). Further annealing during the in situ XPS process up to a temperature of 923 K showed a redox reaction and the formation of oxygen vacancies (Vo) in the BFO crystal lattice. Bubble delamination creates flakes of BiFeO3-x/rGO heterostructures. Magnetic measurements (M-H) showed ferromagnetism (FM) at room temperature Ms ~ 120 emu/cm3. The contribution to magnetization is influenced by the factor of charge redistribution on Vo causing the distortion of the lattice as well as by the superstructure formed at the boundary of two phases, which causes strong hybridization due to the superexchange interaction of the BFO film with the FM sublattice of the interface region. The development of a method for obtaining multiferroic structures with high FM values (at room temperature) is promising for magnetically controlled applications.

Comparison of Different Approaches to Surface Functionalization of Biodegradable Polycaprolactone Scaffolds.

Due to their good mechanical stability compared to gelatin, collagen or polyethylene glycol nanofibers and slow degradation rate, biodegradable poly-ε-caprolactone (PCL) nanofibers are promising material as scaffolds for bone and soft-tissue engineering. Here, PCL nanofibers were prepared by the electrospinning method and then subjected to surface functionalization aimed at improving their biocompatibility and bioactivity. For surface modification, two approaches were used: (i) COOH-containing polymer was deposited on the PCL surface using atmospheric pressure plasma copolymerization of CO2 and C2H4, and (ii) PCL nanofibers were coated with multifunctional bioactive nanostructured TiCaPCON film by magnetron sputtering of TiC-CaO-Ti3POx target. To evaluate bone regeneration ability in vitro, the surface-modified PCL nanofibers were immersed in simulated body fluid (SBF, 1×) for 21 days. The results obtained indicate different osteoblastic and epithelial cell response depending on the modification method. The TiCaPCON-coated PCL nanofibers exhibited enhanced adhesion and proliferation of MC3T3-E1 cells, promoted the formation of Ca-based mineralized layer in SBF and, therefore, can be considered as promising material for bone tissue regeneration. The PCL-COOH nanofibers demonstrated improved adhesion and proliferation of IAR-2 cells, which shows their high potential for skin reparation and wound dressing.

Plasma Surface Polymerized and Biomarker Conjugated Boron Nitride Nanoparticles for Cancer-Specific Therapy: Experimental and Theoretical Study.

A new low-pressure plasma-based approach to activate the surface of BN nanoparticles (BNNPs) in order to facilitate the attachment of folate acid (FA) molecules for cancer-specific therapy is described. Plasma treatment of BNNPs (BNNPsPT) was performed in a radiofrequency plasma reactor using ethylene and carbon dioxide monomers. The carboxyl groups deposited on the surface of BNNPsPT were activated by N,N'-dicyclohexylcarbodiimide (DCC) and participated in the condensation reaction with ethylene diamine (EDA) to form a thin amino-containing layer (EDA-BNNPPT). Then, the DCC-activated FA was covalently bonded with BNNPsPT by a chemical reaction between amino groups of EDA-BNNPsPT and carboxyl groups of FA. Density functional theory calculations showed that the pre-activation of FA by DCC is required for grafting of the FA to the EDA-BNNPsPT. It was also demonstrated that after FA immobilization, the electronic characteristics of the pteridine ring remain unchanged, indicating that the targeting properties of the FA/EDA-BNNPsPT nanohybrids are preserved.

Immobilization of Platelet-Rich Plasma onto COOH Plasma-Coated PCL Nanofibers Boost Viability and Proliferation of Human Mesenchymal Stem Cells.

The scaffolds made of polycaprolactone (PCL) are actively employed in different areas of biology and medicine, especially in tissue engineering. However, the usage of unmodified PCL is significantly restricted by the hydrophobicity of its surface, due to the fact that its inert surface hinders the adhesion of cells and the cell interactions on PCL surface. In this work, the surface of PCL nanofibers is modified by Ar/CO2/C2H4 plasma depositing active COOH groups in the amount of 0.57 at % that were later used for the immobilization of platelet-rich plasma (PRP). The modification of PCL nanofibers significantly enhances the viability and proliferation (by hundred times) of human mesenchymal stem cells, and decreases apoptotic cell death to a normal level. According to X-ray photoelectron spectroscopy (XPS), after immobilization of PRP, up to 10.7 at % of nitrogen was incorporated into the nanofibers surface confirming the grafting of proteins. Active proliferation and sustaining the cell viability on nanofibers with immobilized PRP led to an average number of cells of 258 ± 12.9 and 364 ± 34.5 for nanofibers with ionic and covalent bonding of PRP, respectively. Hence, our new method for the modification of PCL nanofibers with PRP opens new possibilities for its application in tissue engineering.

Cell proliferation on modified DLC thin films prepared by plasma enhanced chemical vapor deposition.

Recently, diamondlike carbon (DLC) thin films have gained interest for biological applications, such as hip and dental prostheses or heart valves and coronary stents, thanks to their high strength and stability. However, the biocompatibility of the DLC is still questionable due to its low wettability and possible mechanical failure (delamination). In this work, DLC:N:O and DLC: SiOx thin films were comparatively investigated with respect to cell proliferation. Thin DLC films with an addition of N, O, and Si were prepared by plasma enhanced CVD from mixtures of methane, hydrogen, and hexamethyldisiloxane. The films were optically characterized by infrared spectroscopy and ellipsometry in UV-visible spectrum. The thickness and the optical properties were obtained from the ellipsometric measurements. Atomic composition of the films was determined by Rutherford backscattering spectroscopy combined with elastic recoil detection analysis and by x-ray photoelectron spectroscopy. The mechanical properties of the films were studied by depth sensing indentation technique. The number of cells that proliferate on the surface of the prepared DLC films and on control culture dishes were compared and correlated with the properties of as-deposited and aged films. The authors found that the level of cell proliferation on the coated dishes was high, comparable to the untreated (control) samples. The prepared DLC films were stable and no decrease of the biocompatibility was observed for the samples aged at ambient conditions.