Oxygen reduction reaction (ORR) is an important reaction for fuel cells and platinum on carbon (Pt/C) is a typical electrocatalyst for ORR in industrial applications. There is a constant search for a replacement for Pt/C with better ORR electrocatalytic performance but thus far, most materials show poorer electrocatalytic activity than Pt/C. Herein, we present electrocatalytical studies of platinum (Pt) dichalcogenides as alternative electrocatalyst for ORR. Interestingly, not only have we found that PtTe 2 demonstrates similar electrocatalytic performance for ORR but its toxicity is significantly lower than the toxicity of Pt/C. This study shows that layered transition metal dichalcogenide family members have strong application potential not only for hydrogen evolution reaction (HER − proton reduction), but also, unexpectedly, for oxygen reduction reaction. We demonstrate PtTe 2 as a safer alternative electrocatalyst material for ORR. These studies can allow better understanding of the electrocatalytic performance and toxicological profiles of Pt dichalcogenides in comparison to Pt/C to aid future mass application and commercialization in clean energy reactions such as ORR.

The production of large quantities of micromachines and microrobots is limited by fabrication methods and the use of synthetic templates. Pollen is one of the most stable structures in the world, capable of surviving harsh treatment and for millions of years. Pollen grains are available in large variety of shapes and sizes. The use of a wide variety of naturally abundant, nontoxic pollen grains for the efficient fabrication of platinum-pollen (Pt-pollen) hybrid microrobots capable of fast propulsion for environmental and biomedical applications is demonstrated. Nine different pollen grains are selected and modified (dandelion, pine, lotus, sunflower, poppy, camellia, lycopodium, cattail, and galla) to demonstrate the robustness of different types of pollen grains for potential applications in environmental remediation. The efficient mobility rendered by the fabricated microrobots enhances their performance in the removal of heavy metals in aqueous medium. Furthermore, they can be used as doxorubicin carriers.

Electrochemical and electrocatalytic properties of a class of layered materials known as MAX and MAB phases have yet to gain interest in the scientific community. Herein, electrochemical and toxicity studies of six MAX and MAB phases (Ti 2 AlC, Ti 2 AlN, Ti 3 AlC 2 , Ti 3 SiC 2 , Cr 2 AlB 2 , and MoAlB) were explored. The materials were found to possess high heterogeneous electron transfer (HET) rates, enhanced electrochemical sensing of ascorbic acid and uric acid, and promising electrocatalytic performances toward hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). MAB phases possessed better electrochemical properties than did MAX phases. In addition, in vitro cytotoxicity studies toward various human cells found near negligible toxicity toward the cells tested deeming them safe for handling and biocompatible for future biological applications. Therefore, MAX and MAB phases can be regarded as safe layered materials for potential electrochemical applications.

(1 of 11)2D monoelemental group 14 materials beyond graphene, such as silicene and germanene, have recently gained a lot of attention. Covalent functionalization of group 14 layered materials can lead to significant tuning of their properties. While optical and electronic properties of germanene, silicene, and their derivatives have been studied in detail previously, there is no information on their electrochemistry and toxicity. Herein, electrochemical applications of 2D siloxene, germanane, and methylgermanane, specifically for detection of an important biomarker, dopamine, as well as catalyzation of oxygen reduction and hydrogen evolution reactions, which are important in energy applications, are explored. Among the three materials, germanane portrays most superior properties for the electrochemical applications mentioned. All three materials possess fast heterogeneous electron transfer rates, relative to bare glassy carbon electrodes. In addition, toxicity studies of these materials are conducted to gain insights on their possible harmful effects toward human health. The results of this study show siloxene nontoxic while germanane and methylgermanane impose dose-dependent toxicity. Interestingly, methylation successfully reduce the toxicity of methylgermanane at lower concentrations. These studies provide fundamental insights into electrochemical and toxic properties of functionalized group 14 layered materials for future electrochemical applications.

Graphitic carbon nitride has attracted extensive interests recently because of its potential in biosensing, photocatalytic, and biomedical applications. Similar to graphene, it is a two-dimensional carbon and nitrogen-based nanomaterial with weak van der Waals forces between each layer. Carbon nitrides can have various structural moieties such as triazine and heptazine. Unlike graphene-substituted nanosheets, the toxicity of graphitic carbon nitrite is largely unknown. In respond to that, toxicological study was carried out to determine its toxicity toward human lung carcinoma epithelial cells (A549). Two formazan-based cell viability assays (water-soluble tetrazolium salt (WST-8) assay and methylthiazolyldiphenyltetrazolium bromide (MTT) assay) were utilized on the A549 cell line to derive the cytotoxicity profile. Both materials demonstrated a dose-dependent toxicological effect with triazine-based carbon nitrides being more cytotoxic than heptazine-based carbon nitrides. These findings are of great importance, and this paves the way for exploring carbon nitride materials in numerous fields such as photocatalysis and electrocatalysis.

Magnesium (Mg)-based micromotors have attracted considerable attention as they are capable of moving in water and human blood plasma without external fuels. It has also been demonstrated that they have potential for drug delivery in mouse stomach. However, their biocompatibility and cytotoxicity to human cells have yet to be studied. Therefore, we performed cytotoxicity study of Mg/Pt Janus micromotors with human lung carcinoma epithelial cells (A549), human breast cancer cells (MCF-7), human embryonic kidney cells (HEK-293), human liver carcinoma cells (HepG2) and human cervical cancer cells (HeLa). The highest concentration of micromotors tested, 200 µg mL−1, drastically induced a high toxic effect on the cells and reduced the cell viability to below 60%. This shows while Pt/Au nanomachines were found to be safe previously, this is not the case of the Mg/Pt micromachines.

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Graphene oxide (GO) has been widely explored by many in drug delivery strategies and toxicity assays. The toxicity of graphene oxide depends on the size of the sheets. Smaller sheets show lower toxicity, a quality which is essential for utilization in biomedical applications. However, despite vast research on GO, anticancer properties and drug carrier capabilities of graphene oxide nanoplatelets have yet to be fully explored. Herein, we have uniquely prepared graphene oxide nanoplatelets (GONPs) from well-defined stacked graphite nanofibers (SGNF) with a base of 50 × 50 nm 2 for toxicity and drug potentiation studies when coadministered with the chemotherapeutic drug cisplatin (CP) in human lung cancer cells, A549 cells. Results obtained from our studies have found that not only were GONPs able to act as drug carriers, but they can also significantly potentiate anticancer effect of CP in A549 cells.