Nanosheet

From Wikipedia, the free encyclopedia

A nanosheet is a two-dimensional nanostructure with thickness in a scale ranging from 1 to 100 nm.[1][2] A typical example of nanosheet is graphene, the thinnest two-dimensional material (0.34 nm) in the world.[3] It only consists of single layer of carbon atoms with hexagonal lattices.

Synthesis

TEM image of PbO nanosheets with highly symmetric edge length. The edges of PbO nanosheets are surrounded with Au NPs seeds.

Currently, the most commonly used synthesis methods for nanosheet are based on bottom-up approach, e.g., solution phase synthesis and chemical vapor deposition (CVD).[4] For example, CdTe nanosheets could be synthesized by precipitating and aging CdTe nanoparticles in deionized water.[5] The formation of free-floating CdTe nanosheets were due to directional hydrophobic attraction and anisotropic electrostatic interactions causing by dipole moment and small positive charges. Molecular simulations through a coarse-grained model with parameters from semi-empirical quantum mechanics calculations can be used to prove the experimental process. Ultrathin single-crystal PbS sheets with micro scale in x-, y- dimensions can be obtained using a hot colloidal synthesis method.[6] Compounds with linear chloroalkanes like 1,2-dichloroethane containing chlorine were used during the formation of PbS ultra-thin sheets. It was found that the PbS ultrathin sheets probably resulted from the oriented attachment of the PbS nanoparticles in a two-dimensional fashion. The highly reactive <110> facets were preferentially consumed in the growth process that lead to the sheet-like PbS crystal growth.

Besides above-mentioned synthesis under high temperature conditions, nanosheets can also be prepared at room temperature. For instance, hexagonal PbO nanosheets were synthesized using gold nanoparticles (Au NPs) as seeds under room temperature.[7] The size of the PbO nanosheet can be tuned by Au NPs and Pb2+ concentration in the growth solution. No organic surfactants were employed in the synthesis process. Oriented attachment, in which the sheets form by aggregation of small nanoparticle that each has a net dipole moment,[8] and ostwald ripening[9] are the two main reasons for the formation of the PbO nanosheets.

See also

References

  1. ↑ Coleman, J. N.; Lotya, M.; O'Neill, A.; Bergin, S. D.; King, P. J.; Khan, U.; Young, K.; Gaucher, A. et al. (2011). "Two-Dimensional Nanosheets Produced by Liquid Exfoliation of Layered Materials". Science 331 (6017): 568–571. doi:10.1126/science.1194975. 
  2. ↑ Guo, Shaojun; Dong, Shaojun (2011). "Graphene nanosheet: synthesis, molecular engineering, thin film, hybrids, and energy and analytical applications". Chemical Society Reviews 40 (5): 2644–2672. doi:10.1039/C0CS00079E. 
  3. ↑ Geim, A. K. (2009). "Graphene: status and prospects". Science 324 (5934): 1530–1534. doi:10.1126/science.1158877. PMID 19541989. 
  4. ↑ Sreekanth, Kandammathe Valiyaveedu; Zeng, Shuwen; Shang, Jingzhi; Yong, Ken-Tye; Yu, Ting (2012). "Excitation of surface electromagnetic waves in a graphene-based Bragg grating". Scientific Reports 2. doi:10.1038/srep00737. 
  5. ↑ Tang, Z.; Zhang, Z.; Wang, Y.; Glotzer, S. C.; Kotov, N. A. (2006). "Self-assembly of CdTe nanocrystals into free-floating sheets". Science 314 (5797): 274–278. doi:10.1126/science.1128045. 
  6. ↑ Schliehe, C.; Juarez, B. H.; Pelletier, M.; Jander, S.; Greshnykh, D.; Nagel, M.; Meyer, A.; Foerster, S. et al. (2010). "Ultrathin PbS sheets by two-dimensional oriented attachment". Science 329 (5991): 550–553. doi:10.1126/science.1188035. 
  7. ↑ Zeng, Shuwen; Liang, Yennan; Lu, Haifei; Wang, Libo; Dinh, Xuan-Quyen; Yu, Xia; Ho, Ho-Pui; Hu, Xiao et al. (2012). "Synthesis of symmetrical hexagonal-shape PbO nanosheets using gold nanoparticles". Materials Letters 67: 74–77. doi:10.1016/j.matlet.2011.09.048. 
  8. ↑ Talapin, Dmitri V.; Shevchenko, Elena V.; Murray, Christopher B.; Titov, Alexey V.; Král, Petr (2007). "Dipole-dipole interactions in nanoparticle superlattices". Nano Letters 7 (5): 1213–1219. doi:10.1021/nl070058c. 
  9. ↑ Yang, Weiyou; Gao, Fengmei; Wei, Guodong; An, Linan (2010). "Ostwald Ripening Growth of Silicon Nitride Nanoplates". Crystal Growth & Design 10: 29–31. doi:10.1021/cg901148q. 
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