Nanodiamonds (NDs) are amongst the most investigated carbon-based nanostructures due to their chemical stability and favorable mechanical properties. Despite the number of works on methods for NDs production, one of the main challenges is to achieve their colloidal stability in aqueous suspension. Additionally, NDs are normally obtained by expensive, complex and time-consuming process. Herein, it was presented a facile method to obtain NDs in aqueous suspension by using columnar structure diamond from Hot-Filament Chemical Vapour Deposition reactor (HFCVD). CVD diamond leftover thick film from CVDVale Company was used. Therefore, this method has the advantage of being not only practical but also cost-effective since it brings a profitable use of CVD diamond leftover. The Diamond thick film was submitted to ultrasonic cavitation in the presence and absence of ZrO 2 microbeads in aqueous medium. The NDs hydrodynamic diameter and the stability in aqueous suspension were monitored by light scattering, size and morphology were analyzed by transmission electronic microscopy. Considering the wide application of NDs in biomedical devices, cytotoxicity of aqueous suspensions of NDs was evaluated against murine embryonic fibroblast cells. Furthermore, NDs were functionalized with hydrogen and carboxyl groups. NDs aqueous suspension of straight size distribution was obtained even in the absence of ZrO 2 beads, indicating that they may be dispensable in order to decrease NDs size. NDs of average hydrodynamic diameter of 22 nm and − 35 mV of Zeta-potential were obtained after ultrasonic cavitation followed by 2 h of centrifugation, not demonstrating cytotoxicity to cells at very low (0.05-0.5 μg/mL) nor at higher concentrations (116 μg/mL). Nevertheless, NDs showed a moderate cytotoxicity at intermediary concentration range (0.5-2.2 μg/mL). From our knowledge, this is the first work that reports on a facile method for providing NDs aqueous suspension with high colloidal stability from HFCVD diamond leftover.
DLC films were grown with Zn via a combined plasma-enhanced chemical vapor deposition (PECVD) and high-power impulse magnetron sputtering (HIPIMS) process. The films were deposited on textiles in an atmosphere of Ar and C2H2, and the percentage of metal in the DLC was varied by controlling the acetylene gas flow. At first, to evaluate the antimicrobial activity, a screening test with the ISO 22196 standard was carried out. Afterward, AATCC TM100:2019 was used to evaluate the antimicrobial effectiveness of the films on textiles. The antimicrobial effectiveness of the coating was studied against a Gram-negative bacterium ( Escherichia coli), a Gram-positive bacterium ( Staphylococcus aureus), and a fungus ( Candida albicans), after a 24 h contact. In addition, the cytotoxicity of the samples to mammalian cells was evaluated by indirect contact. For this, the samples were soaked into the growth media for 1 and 7 days, and then, the extracts were collected and put in contact with keratinocytes for 24 h. Finally, the properties of the films were also evaluated as a function of the Zn content, such as their structural quality, morphology, hardness, wear resistance, and coefficient of friction. The films showed excellent results against all microorganisms, with 100% effectiveness in some cases. The pure extracts obtained from all the samples with the incorporation of metals were cytotoxic. Despite that, the cell viability after contact with some Zn-DLC diluted extracts (10%) was not different from that observed in the uncoated group. Besides, increasing the Zn content resulted in a film with poorer mechanical properties but did not affect the coefficient of friction of the coating.
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