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© 2021 The Authors. Ultrasound-assisted liquid phase exfoliation is a promising method for manufacturing of 2D materials in large scale and sustainable manner. A large number of studies using ex-situ nano/micro structural characterization techniques have been made to investigate the underlying mechanisms, aiming to understand the exfoliation dynamics. Due to the complex multiphysics and multi-length nature of the process, those ex-situ methods cannot provide the real-time and in-situ dynamic information for understanding how exactly layer exfoliation starts and grows under ultrasound. Here, we used the ultrafast synchrotron-X-ray phase-contrast imaging (a combined temporal resolution of 3.68 μs and a spatial resolution of 1.9 μm/pixel) to study the exfoliation dynamics in real time and operando condition. We revealed, for the first time, the fatigue exfoliation phenomenon at the graphite surface caused by the imploding ultrasonic bubbles occurring cyclically in line with the ultrasound frequency. A multiphysics numerical model was also developed to calculate the shock wave produced at bubble implosion and the resulting cyclic and impulsive tensile and shear stresses acting on the graphite surface. Our research reveals that the graphite layer exfoliation rate and efficiency are predominantly determined by the number of imploding bubbles inside the effective cavitation bubble zone. The findings are valuable for developing industrial upscaling strategies for ultrasound processing of 2D materials. UK Engineering and Physical Sciences Research Council (Grant Nos. EP/R031665/1; EP/R031401/1; EP/R031819/1; EP/R031975/1); Royal Society.

This review presents the latest innovations and trends in the field of surface functionalization of various nanomaterials. The most recent protocols of smart materials fabrication as well as the main challenges which should be overcome in order to improve their final performance are discussed here. Particular attention has been paid to the properties improvement of polymer, silica, inorganic and hybrid nanomaterials and their potential for application in many fields, from industry, materials science, environmental protection to advanced biomedicine.

Photoluminescence properties of red-emitting Pr3+-doped Bi2ZnOB2O6 microcrystalline powder and PMMA-based composite materials were reported. Bi2ZnOB2O6:Pr3+ powders were synthesized by means of the modified Pechini method. The morphology and crystallographic structure of Bi2ZnOB2O6:Pr3+ microcrystals were investigated by XRD and HRTEM. The PMMA-based composite materials were prepared by embedding of Bi2ZnOB2O6:Pr3+ powder in the PMMA matrix. The vibrational properties of the powder and composite systems were investigated by μ-Raman spectroscopy. Emission spectra of the samples were measured under blue (451.6 nm) and UV (320 nm) excitation. Both, the powder and composite samples show enhancement of red emission (1D2 → 3H4) and quenching of greenish-blue luminescence from 3P0 level of Pr3+ ions after excitation in UV and VIS caused by the 3P0 ∼ 1D2 non-radiative relaxation of Pr3+ ion by low-lying charge transfer state and non-radiative de-excitation through Pr3+–Bi3+ energy transfer. The response of the powder and composite samples to pulsed excitation at 451.6 nm was measured by monitoring emission from the 1D2 level (595 nm/3P0 → 3H6 transition). The determined lifetimes τ1 and τ2 of the red emission at 595 nm (1D2 → 3H4 transition) of the composite are significantly longer in comparison to powder samples. Moreover, because of the good nonlinear optical properties of the Bi2ZnOB2O6 crystals and effective luminescence of the Pr3+-doped Bi2ZnOB2O6 powders and composites, they can be very useful as bi-functional materials in the new generation of optoelectronic devices.

In this study we examine multiwall carbon nanotube (MWCNT) based nanosystems i.e. aligned MWCNT matrices, as potential scaffolds for cell growth and tissue engineering. We present the effect of samples purification and surface modification on the viability, adhesiveness and morphology of human normal gingival fibroblasts (HGF-1) and human osteosarcoma (U2OS) cell lines. We employ spectroscopic and analytical techniques (Scanning Electron Microscopy, Thermal Gravimetric Analysis, Atomic Force Microscopy, Raman and Fourier Transform Infrared Absorption Spectroscopy and Confocal Microscopy) in order to characterize the obtained structures. Furthermore, we analyze the expression level of selected cell adhesion-related genes by the quantitative real-time (qRT-PCR) method and the cell viability for MWCNT powders. We show that the surface structure of MWCNTs carpets contributes to the adhesion of cells. Additionally, we report the increased expression level of integrin, talin and fibronectin, proteins which are involved in cell attachment. We speculate that carbon nanotube based materials can be consider as potential candidates for biomedical purposes and as a biocompatible scaffold for cell growth.

In this work, functionalized Multiwall Carbon Nanotubes of specified length and containing well-defined iron particles (O-MWCNT/Fe) were prepared. A significant enhancement in contrast in Magnetic Resonance Imaging was found for the investigated composites. The magnetic characterization revealed the ferromagnetic nature of iron particles embedded within O-MWCNTs. The enhancement of the 1 H spin–spin relaxation time of MRI scans using hydrophilic O-MWCNT/Fe as potential contrast agents was estimated for selected dispersive media. Moreover, the cytotoxicity of the hybrids was studied in two cell lines, i.e. cancer cells (HeLa) and fibroblasts (GM07492). The intracellular impact of O-MWCNT/Fes in HeLa cells was observed after staining of selected organelles (nuclei and mitochondria). Significant changes in cell morphology were found for water soluble MWCNT/Fes with diameters above 30 nm.

Composite coatings provide a promising way of in vitro cell behavior screening. Previous efforts included fabrication of single-walled carbon nanotubes (SWCNTs)-polymer materials, however in this work, for the first time we combined two polymers of different hydrophobic character: poly(maleic-alt-1-octadecene) and polyvinylpyrrolidone with multi-walled carbon nanotubes (MWCNTs) to produce composite coatings with varied hydrophobicity. Prior to their incorporation, MWCNTs were characterized using Raman spectroscopy during ball-milling procedure at different times to establish ideal fabrication conditions for their best quality. Electrostatic force microscopy was then used to look at the distribution and MWCNTs networks formation in the composite coatings. Atomic force and scanning electron microscopies were used to establish the topographical features and thicknesses of produced coatings, which varied with the content of MWCNTs. All composites as well as control pure polymer coatings proved to be biocompatible and exhibited a viability of >80% on two human cell lines: cancerous osteosarcoma (U2OS) and fibroblast (MSU-1.1) that varied by their tumorigenicity, irrespectively of the hydrophobicity of the coating. Both cell lines were further shown by scanning electron microscopy to remain in the typical morphological state with high proliferation and attachment to all formed composites. These results show the potential of formation of MWCNTs-polymer composites by facile preparation way (spin-coating) and their potential as coatings for 2D in vitro cell culture platforms.