title: Less-Common Nanostructures: Nanobuds: A Micro-Review.
abstract: BACKGROUND
  Synthesis, properties, structural peculiarities, and applications of nanobuds and related nanostructures are discussed. In addition, few relevant patents to the topic have been reviewed and cited. According to observed properties and those predicted by DFT calculations, the nanobuds are semiconducting and stable in normal conditions, can accept adatoms and molecules. They contain a relatively chemically inert carbon nanotubes and more active fullerene species and can be compatible with a variety of other materials, in particular polymers. In addition to nanobuds for SWCNTs, the nanobuds with graphene, small fullerenes or metal nanobud-like structures are also known.
  
  
  METHODS
  We have undertaken an extensive search of bibliographic databases for peer-reviewed research literature using a focused review question and inclusion/exclusion criteria. The characteristics of screened papers were described and critically compared.
  
  
  RESULTS
  Thirty-six papers were included in the review, mainly from high-impact international journals. The published articles correspond to the range 2006-2016; the term "nanobuds" appeared in 2006 after their discovery. The reports included approaches of the synthesis of carbon nanobuds, their formation mechanism, in situ engineering, different modes of attachment of fullerene on carbon nanotubes, DFT and MD calculations, nanobuds containing small fullerenes and graphene nanobuds, information about related noble metal nanobuds, and applications of carbon nanobuds.
  
  
  CONCLUSIONS
  The findings of this review confirm the importance of novel less-common nanostructures on the basis of carbon for fundamental science, their unusual properties and current and possible applications.
authors.affiliation: Department of Chemistry, Universidad Autónoma de Nuevo León, Monterrey. Mexico.
authors.forename: Boris I
authors.initials: BI
authors.lastname: Kharisov
authors.affiliation: Department of Physico- Mathematic, Universidad Autónoma de Nuevo León, Monterrey 66455. Mexico.
authors.forename: Oxana V
authors.initials: OV
authors.lastname: Kharissova
authors.affiliation: Department of Chemistry, Universidad Autónoma de Nuevo León, Monterrey. Mexico.
authors.forename: Yolanda P
authors.initials: YP
authors.lastname: Méndez
keywords: Carbon nanotubes; DFT calculations; fullerenes; gas storage; inorganic adatoms; nanobuds; semiconductor; small fullerenes