Synthesis, Crystal Structure, and Luminescence Properties of a Novel Green-Yellow Emitting Phosphor LiZn_1−<i>x</i>PO₄:Mn_<i>x</i> for Light Emitting Diodes

Synthesis, Crystal Structure, and Luminescence Properties of a Novel Green-Yellow Emitting Phosphor LiZn1−xPO4:Mnx for Light Emitting Diode

Monitoring Ti₃C₂T_<i>x</i> MXene Degradation Pathways Using Raman Spectroscopy

Extending applications of Ti3C2Tx MXene in nanocomposites and across fields of electronics, energy storage, energy conversion, and sensor technologies necessitates simple and efficient analytical methods. Raman spectroscopy is a critical tool for assessing MXene composites; however, high laser powers and temperatures can lead to the materials’ deterioration during the analysis. Therefore, an in-depth understanding of MXene photothermal degradation and changes in its oxidation state is required, but no systematic studies have been reported. The primary aim of this study was to investigate the degradation of the MXene lattice through Raman spectroscopic analysis. Distinct spectral markers were related to structural alterations within the Ti3C2Tx material after subjecting it to thermal- and laser-induced degradation. During the degradation processes, spectral markers were revealed for several specific steps: a decrease in the number of interlayer water molecules, a decrease in the number of −OH groups, formation of C–C bonds, oxidation of the lattice, and formation of TiO2 nanoparticles (first anatase, followed by rutile). By tracking of position shifts and intensity changes for Ti3C2Tx, the spectral markers that signify the initiation of each step were found. This spectroscopic approach enhances our understanding of the degradation pathways of MXene, and facilitating enhanced and dependable integration of these materials into devices for diverse applications, from energy storage to sensors

Chitosan-Modified Stable Colloidal Gold Nanostars for the Photothermolysis of Cancer Cells

The preparation and properties of plasmonic gold nanostars (Au NSs) modified with a biopolymer chitosan are reported. The colloidal stability of Au NSs at the physiological pH of 7.5 and their performance in the photothermolysis of cancer cells in vitro were compared with those of gold nanorods (Au NRs). The optical characteristics of chitosan-modified Au NSs dispersed in a medium with pH = 7.5 had higher stability than those of chitosan-capped NRs because of the slower aggregation of NSs. At pH = 7.5, the chitosan-modified Au NRs formed aggregates with highly nonuniform sizes. On the other hand, Au NSs formed small chain-like clusters, in which individual NSs were connected to one another, preferably via association of branches with central cores. It is possible that the difference in areal charge density at these parts of NSs is responsible for their preferred association. Flow cytometry analysis showed the relatively nonequivalent distribution of the chitosan-capped Au NRs across the cell line compared with that of Au NSs because of the fast and nonuniform aggregation of NRs. An in-vitro photothermolysis experiment on J5 cancer cells showed that energy fluences of 23 and 33 mJ/cm² are necessary to cause complete death of J5 cells incubated with 4 μg/mL chitosan-capped Au NSs and NRs, respectively. When chitosan was used as a surface-capping agent, the Au NSs exhibited higher colloidal stability at the physiological pH than the NRs and lower energy fluence necessary for cell photothermolysis because of more uniform cellular uptake

MXene-Assisted Ablation of Cells with a Pulsed Near-Infrared Laser

Innovative therapies are urgently needed to combat cancer. Thermal ablation of tumor cells is a promising minimally invasive treatment option. Infrared light can penetrate human tissues and reach superficial malignancies. MXenes are a class of 2D materials that consist of carbides/nitrides of transition metals. The transverse surface plasmons of MXenes allow for efficient light absorption and light-to-heat conversion, making MXenes promising agents for photothermal therapy (PTT). To date, near-infrared (NIR) light lasers have been used in PTT studies explicitly in a continuous mode. We hypothesized that pulsed NIR lasers have certain advantages for the development of tailored PTT treatment targeting tumor cells. The pulsed lasers offer a wide range of controllable parameters, such as power density, duration of pulses, pulse frequency, and so on. Consequently, they can lower the total energy applied and enable the ablation of tumor cells while sparing adjacent healthy tissues. We show for the first time that a pulsed 1064 nm laser could be employed for selective ablation of cells loaded with Ti3C2Tx MXene. We demonstrate both low toxicity and good biocompatibility of this MXene in vitro, as well as a favorable safety profile based on the experiments in vivo. Furthermore, we analyze the interaction of MXene with cells in several cell lines and discuss possible artifacts of commonly used cellular metabolic assays in experiments with MXenes. Overall, these studies provide a basis for the development of efficient and safe protocols for minimally invasive therapies for certain tumors

Polycaprolactone–MXene Nanofibrous Scaffolds for Tissue Engineering

New conductive materials for tissue engineering are needed for the development of regenerative strategies for nervous, muscular, and heart tissues. Polycaprolactone (PCL) is used to obtain biocompatible and biodegradable nanofiber scaffolds by electrospinning. MXenes, a large class of biocompatible 2D nanomaterials, can make polymer scaffolds conductive and hydrophilic. However, an understanding of how their physical properties affect potential biomedical applications is still lacking. We immobilized Ti3C2Tx MXene in several layers on the electrospun PCL membranes and used positron annihilation analysis combined with other techniques to elucidate the defect structure and porosity of nanofiber scaffolds. The polymer base was characterized by the presence of nanopores. The MXene surface layers had abundant vacancies at temperatures of 305–355 K, and a voltage resonance at 8 × 104 Hz with the relaxation time of 6.5 × 106 s was found in the 20–355 K temperature interval. The appearance of a long-lived component of the positron lifetime was observed, which was dependent on the annealing temperature. The study of conductivity of the composite scaffolds in a wide temperature range, including its inductive and capacity components, showed the possibility of the use of MXene-coated PCL membranes as conductive biomaterials. The electronic structure of MXene and the defects formed in its layers were correlated with the biological properties of the scaffolds in vitro and in bacterial adhesion tests. Double and triple MXene coatings formed an appropriate environment for cell attachment and proliferation with mild antibacterial effects. A combination of structural, chemical, electrical, and biological properties of the PCL–MXene composite demonstrated its advantage over the existing conductive scaffolds for tissue engineering