The dark-field diffraction contrast of helical nanotubes (NTs) is show
n to be asymmetric when an NT is tilted at appropriate angle with resp
ect to the incident electron beam. This phenomenon was used for the ch
irality determination of multi-shell NTs observed in MoS2 layered comp
ound. Both kinds of NT - helical and non-helical were found. In the ca
se of helical NTs only right-hand chirality was observed.