The design, engineering and electron microscopic characterization of anisotropic nanosized snowflake‐like structural assemblies (nanosnowflakes) is reported. They were fabricated through immobilization of double stranded amine‐modified and thiol‐terminated DNA oligonucleotides on the surface of ultra‐small isotropic gold nanoparticles used as nanocarriers. The transmission electron microscopy images combined with spectrophotometric data revealed the formation of self‐assembled structural aggregation between individual ligands‐coated nanoparticles. They act as seeds for the further spontaneous dendritic growth in different directions. Their anisotropic morphology is formed due to the occurrence of facilitated electrostatic interactions between positive charged amino‐groups and the negative sugar‐phosphate backbone of oligonucleotides. Thus, nanosnowflakes with size distribution between 40 and 80 nm were obtained. The microscopic analysis demonstrated also that the stable nanosnowflakes structure was highly dependent on the solution ionic strength, which effect the charge fluctuation within the assembly. The reported DNA functionalized nanostructures have potential to be applied as a platform for development of therapeutic materials, as well as drug delivery nanosystems.Research Highlights The engineering, fabrication, and microscopic characterization of DNA nanosnowflakes is reported. The electron microscopy analysis revealed formation of self‐assemblies with anisotropic morphology. The nanosnowflakes size distribution was between 40 and 80 nm.
The copper is the second largest strategic raw material. Since there is a huge gap between copper production and consumption, a green and eco-sustainable recycling technology is necessary that is able to process the copper from secondary sources of waste and scraps. Here we demonstrate the photo-oxidising properties of pyrrolic nitrogen-dominated carbon nanodots as eco-friendly and powerful oxidase-mimicking nanozyme for leaching of copper from metal scrap under irradiation with either ultraviolet or natural sun light (average intensity of 59 000 lux). The ultra-small nanoparticles with diameter < 5 nm were prepared by 600 W microwave-assisted pyrolysis, which might be considered as energy efficient synthetic method. The developed strategy enables to dissolve Cu metal at neutral pH range (between 5.1 – 8.3) and it might break the pH limitation for recycling of copper in the conventional chemical methods, where toxic and corrosive substances are used. The obtained yield was about 5 %, which is still not satisfactory for practical application in recycle technology. Nevertheless, according to our knowledge there is not any other reported photosensitizer nanozyme, which is capable to induce oxidation and dissolving of copper under natural light irradiation of neutral leaching solution.
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