Vibrational characteristics of defective single walled BN nanotube based nanomechanical mass sensors: single atom vacancies and divacancies

• We performed vibrational characterization of defective single walled BN nanotube as a nanomechanical mass sensor.
• Molecular structural mechanics based simulation approach is implemented to simulate the defective single walled BNNT.
• Mass sensitivity limit of 10−25 kg can be obtained using SWBNNT based nanomechanical mass sensor.
• The presence of point defects affect the stiffness of the SWBNNT and ultimately alters its vibrational characteristics

In the present work, vibrational characteristics of a single walled BN nanotube (SWBNNT) is explored considering point defects (single atom vacancies and di-vacancies) to use SWBNNTs as nanomechanical mass sensors. Resonant frequency based analysis of SWBNNT with different types of point defect is performed using an atomistic finite element model based on molecular structural mechanics. The cantilevered configuration of zigzag (14,0) form of SWBNNT with different point defects is modeled considering it as a space frame structure with three dimensional elements and point masses, such that the proximity of the model to the actual atomic structure of nanotube is significantly retained. The finite element simulation approach is used to analyze the effect of point defects like single atom vacancies (VB – boron vacancy and VN – nitrogen vacancy) and divacancies (VBN). The present approach is validated by comparing the obtained simulation results for resonant frequency variation against attached mass at the tip of the cantilevered SWBNNTs, with continuum mechanics based analytical results for defect-free SWBNNT and are found in good agreement. An increase in resonant frequencies observed, when the point defects (VB, VN and VBN) move from fixed-end to the free end of the cantilevered configuration of the SWBNNTs. Also, the resonant frequency shift due to different point defects is analyzed against the attached mass at the free end, for the different positions of the point defect along the length of the nanotube and results indicate that the mass sensitivity limit of 10−25 kg can be obtained. Using present atomistic finite element model based simulation approach, different atomic structures, different types of point defect as well as boundary conditions can be simulated effectually. The present atomistic finite element model based resonant frequency analysis of defective SWBNNTs is useful to develop the algorithm for the detection of the added mass, identification of the type of point defect and its position along the length of the nanotube.