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MAX phases, characterized as nanolaminates of ternary carbides/nitrides structure, possess a unique combination of ceramic and metallic properties, rendering them pivotal in materials research. In this study, chromium aluminum carbide ternary compounds, Cr2AlC (211), Cr3AlC2 (312), and Cr4AlC3 (413) were successfully synthesized with high purity using a facile and cost-effective sol-gel method. Structural, morphological, and chemical characterization of the synthesized phases was conducted to understand the effects of composition changes and explore potential applications. Comprehensive characterization techniques including XRD for crystalline structure elucidations, SEM for morphological analysis, EDX for chemical composition, Raman spectroscopy for elucidation of vibrational modes, XPS to analyze elemental composition and surface chemistry, and FTIR spectroscopy to ensure the functional groups analysis, were performed. X-ray diffraction analysis indicated the high purity of the synthesized Cr2AlC phase as well as other ternary compounds Cr3AlC2 and Cr4AlC3, suggesting its suitability as a precursor for MXenes production. Additionally, the antimicrobial activity against Candida albicans and biocompatibility assessments against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and HepG2 cell line were investigated. The results demonstrated significant antifungal activity of the synthesized phases against Candida albicans and negligible impact on the viability of E. coli and S. aureus. Interestingly, lower concentrations of Cr2AlC MAX phase induced cytotoxicity in HepG2 cells by triggering intercellular oxidative stress, while Cr3AlC2 and Cr4AlC3 exhibited lower cytotoxicity compared to Cr2AlC, highlighting their potential in biomedical applications.

Recently, quantum-dot-based core/shell structures have gained significance due to their optical, optoelectronic, and magnetic attributes. Controlling the fluorescence lifetime of QDs shells is imperative for various applications, including light-emitting diodes and single-photon sources. In this work, novel Cu-doped CdS/ZnS shell structures were developed to enhance the photoluminescence properties. The objective was to materialize the Cu-doped CdS/ZnS shells by the adaptation of a two-stage high-temperature doping technique. The developed nanostructures were examined with relevant characterization techniques such as transmission electron microscopy (TEM) and ultraviolet–visible (UV–vis) emission/absorption spectroscopy. Studying fluorescence, we witnessed a sharp emission peak at a wavelength of 440 nm and another emission peak at a wavelength of 620 nm, related to the fabricated Cu-doped CdS/ZnS core/shell QDs. Our experimental results revealed that Cu-doped ZnS shells adopted the crystal structure of CdS due to its larger bandgap. Consequently, this minimized lattice mismatch and offered better passivation to any surface defects, resulting in increased photoluminescence. Our developed core/shells are highly appropriate for the development of efficient light-emitting diodes.

Manganese-doped CdS/ZnS quantum dots have been used as energy donors in a Förster-like resonance energy transfer (FRET) process to enhance the effective lifetime of organic fluorophores. It was possible to tune the effective lifetime of the fluorophores by about six orders of magnitude from the nanosecond (ns) up to the millisecond (ms) region. Undoped and Mn-doped CdS/ZnS quantum dots functionalized with different dye molecules were selected as a model system for investigating the multiple energy transfer process and the specific interaction between Mn ions and the attached dye molecules. While the lifetime of the free dye molecules was about 5 ns, their linking to undoped CdS/ZnS quantum dots led to a long effective lifetime of about 150 ns, following a non-exponential transient. Manganese-doped core–shell quantum dots further enhanced the long-lasting decay time of the dye to several ms. This opens up a pathway to analyse different fluorophores in the time domain with equal spectral emissions. Such lifetime multiplexing would be an interesting alternative to the commonly used spectral multiplexing in fluorescence detection schemes. [ABSTRACT FROM AUTHOR]