Research And Development Of Biomolecule Sensors Based On Solid-state Molybdenum Disulfide Nanopores

DNA detection technique based on nanopores is considered as the most competitive method of third-generation gene detection.As an ultra-thin two-dimensional material,molybdenum disulfide（MoS₂）nanopore shows potential application in next generation of DNA sequencing.To explore the performance of MoS₂ nanopores in biomolecules detection,nanopore fabrication and test platform were invetigated,and the transport characteristics of MoS₂ nanopores,and the tranlocation of DNA and BSA through MoS₂ nanopores were studied.Some interesting results are obtained as follows:1)MoS₂ nanopore was manufactured by mechanically exfoliating few-layer MoS₂ and transferring the film onto Si₃N₄ membranes,then the nanopore was etched by focused ion beam.2)By measuring the I-V curves of MoS₂ nanopores with different diameters in KCl solution with various concentrations and pH values,the rheological properties of MoS₂nanopores in electrolyte solutions in a nanoscale confined space were investigated.It is found that the conductance of the nanopores was positively correlated with the pore size.At low concentrations,the onductance is mainly determined by the charge of the nanopore surface.At high concentrations,the onductance gradually approaches the bulk KCl solution.At lower concentrations,the surface charge of the MoS₂ nanopores changes with pH,when the pH value increases,the surface charge density increases,and the conductance of the MoS₂ nanopores increases.3)By changing the applied voltage,the concentration of KCl solution,and the pH of KCl solution,the influence of these factors on the tranlocation of DNA molecules through the MoS₂nanopores was studied.The experimental results show that when DNA molecules translocate through MoS₂ nanopore,both the amplitude of the blockade current and normalized current increase while the translocation time decreases with the increase of the voltage.At the same voltage,when the concentration of KCl solution decreases from 1 to 0.1mol/L,the amplitude of blockade current decreases,while the normalized blockade current increases and translocation velocity become faster.While pH only has little impact on blockade current and translocation velocity.4)Comparison experiment ofλ-DNA through MoS₂ nanopores and Si₃N₄ nanopores was performed.Under the same experimental conditions,the blockade current induced by the DNA molecules through the MoS2nanopores is significantly higher than that of the Si₃N₄ nanopores,and the normalized blockade current increases by 3 times,which proves that the nanopore on molybdenum disulfide film has a higher sensitivity and signal to noise ratio compared to Si₃N₄nanopores.5)The influence of voltage and solution concentration on BSA molecular tanslocation through MoS₂ nanopore was investigated.It is found that both normalized current and translocation time decrease with the increase of voltage,proves that BSA unfolding phenomenon occurs under high voltage.When the concentration of KCl solution decreases,the normalized current increases and translocation velocity become faster.6)The translocation behavior of BSA molecules through the MoS₂ nanopore was studied.It was found that BSA molecules translocation through the MoS₂ nanopores mainly in three ways:folding,unfolding,and interaction with nanopores.