On the dynamics of contact line freezing of water droplets on superhydrophobic carbon soot coatings

Hydrophobic soot nanoparticles as a non-cytotoxic motility activator of human spermatozoa

“…2), repeatedly observable elsewhere too. 34,37–39 Independently of the surface morphology and chemistry, all samples are superhydrophobic and possess SCA ∼160–164° and CAH ∼1–2° due to their non-polarity and nanoscale roughness. 34,37–39…”

“…For accomplishing the cytotoxicity studies, a variety of soot nanoparticles were generated by accurately regulating the air ow rate, via a ow meter/controller (Fisher Scientic 11998014, Germany), required to maintain the incomplete combustion of a rapeseed oil-impregnated wick situated in a steel conical combustion chambera well-known technique ensuring reproducible synthesis of extremely water-repellent soot. 32,34,[37][38][39] Three basic types of soot particles/aggregates with adjustably variable shape, size, surface oxidation and zeta potential, clas-sied as soot1 -soot2 -soot3, were deposited as coatings on a series of microscope glass slides at air ow values of 0.0052 m 3 min À1 , 0.0042 m 3 min À1 and 0.0033 m 3 min À1 , and stored in Petri dishes.…”

“…The controlled combustion of vegetable oils is a well-developed method offering inexpensive, facile and one-step fabrication of non-wettable soot with exhaustively examined physicochemical characteristics. 32,34,[37][38][39][40][41][42] Therefore, the morphochemical features shown in Fig. 1 and 2 are routinely discussed and are intended to serve as a benchmark for interpreting the impact of this group of soot nanoparticles on the sperm cells' motility.…”

“…2), repeatedly observable elsewhere too. 34,[37][38][39] Independently of the surface morphology and chemistry, all samples are superhydrophobic and possess SCA $160-164 and CAH $1-2 due to their nonpolarity and nanoscale roughness. 34,[37][38][39] Since the human spermatozoa are negatively charged (À16 mV/À20 mV) and their functionality correlates with the cell membrane's zeta potential, 43 which, on the other hand, governs the cytotoxicity of nanomaterials to different microorganisms, 44,45 it is imperative to measure the surface charge of soot samples, as illustrated in Fig.…”

“…32 Further experiments have conrmed the hypothesis that an osmotic movement outwards the cell matrix is mainly responsible for the semen's uniform dehydration, similarly to the germplasm freezing, 33 because the cooling of water droplets residing on a soot-coated surface leads to simultaneous freezing of the three-phase contact line and the liquid's entire outer shell (the shell is approximated to a cell membrane), but the bulk remains slurry. 34 Although the International Society for Cryobiology has qualied the study as eye-opening, part of this community has claimed that it goes against the basic principles of cryobiology. 32 Moreover, the European Green Deal, approved in 2020, and the aspirations for the decarbonization of the industry, aiming to gain lower output of greenhouse gases (e.g., soot emissions) in the troposphere, enforce the common perception that carbon soot is a highly hazardous substance and must remain in history.…”