The plastisphere is a newly recognized geospheric layer at a planetary scale, characterized by the presence of microorganisms, primarily as biofilms, that colonize inert and poorly decomposable organic matter, particularly plastics. The stability and diversity of substrate plastic fosters a consistent evolutionary trend among microorganisms, leading to specialized ecological niches that enhance particular physiological traits for plastic degradation. Biofilms have been observed on various types of plastics, including both conventional petroleum-based polymers (like polyethylene and polystyrene) and bioplastics (such as polyhydroxyalkanoates). The characterization of plastisphere objects is crucial and should be conducted with geodetic referencing and spatio-temporal metrics to understand the impacts of climatic and meteorological factors. The dynamic nature of species succession in response to environmental changes necessitates advanced analyzes of microbial communities’ potential for plastic degradation. The spatial turnover of core and occasional taxa complicates the precise identification of microbial functions within these communities. The question of “What is in the plastisphere?” emphasizes the need for detailed biogeographical and chemical mapping due to the small size and localized nature of microplastic particles. It is important to differentiate when plastics serve as growth resources (biodegrading) versus mere substrates for microbial growth, raising the question of “Food or just a free ride?” The geochemical and aerochemical activities within the plastisphere are crucial for understanding its broader environmental impacts. These activities include nitrogen metabolism and the biogeochemical cycling of nitrogen, phosphorus, and carbon, which encompasses greenhouse gas emissions associated with plastic degradation. Additionally, trace metals can accumulate in the plastisphere, potentially facilitating photo-Fenton processes that may occur on microplastic surfaces when exposed to sunlight.

Carbon nano-onions are unique, tiny, multilayered carbonaceous nanoparticles having distinct structural, microstructural, and a range of physical characteristics and high-tech uses. Similar to other carbonaceous nanoparticles (graphene, carbon nanotubes), carbon nano-onions, as well as modified carbon nano-onions, have been considered as valuable nanofillers for macromolecules. Along these lines, the present overview refers to the scientific impact of reinforcing carbon nano-onions in polymeric matrices. For this purpose, this manuscript has been systematically categorized into an initial section addressing fundamentals of carbon nano-onions, followed by a major section regarding design, structure-property, and performance aspects of carbon nano-onion nano-reinforced polymeric matrices (conducting, thermoplastics, thermosets). Subsequent review sections unfold promising application zones, challenges, and the future of polymer/carbon nano-onions hybrids. According to the literature, numerous facile and efficient routes (in situ, electrochemical, solution, solvent casting, curing) have been used for fabricating these nanomaterials. Herein, adding carbon nano-onions was noticed to valuably enhance the morphological, physical, and applied scope of the ensuing nanocomposites. Owing to design diversities, a myriad of technological deployments have been noticed for polymer/carbon nano-onions, including space engineering-to-energy production/storage/sensing devices and catalysis. Nevertheless, delimited systematic scientific studies have been performed so far regarding different types of polymer/carbon nano-onions and their applied specifications. Henceforth, focused and continuous research efforts by the field scientists/engineers seemed to be indispensable for overcoming the underlying challenges to attain next-generation industrial-scale carbon nano-onions derivative nanomaterials.