Abstract
The nanopore sensor as a high-throughput and low-cost technology can detect single nanoparticle in solution. In the present study, the silicon nitride nanopores were fabricated by focused Ga ion beam (FIB), and the surface was functionalized with 3-aminopropyltriethoxysilane to change its surface charge density. The positively charged nanopore surface attracted negatively charged nanoparticles when they were in the vicinity of the nanopore. And, nanoparticle translocation speed was slowed down to obtain a clear and deterministic signal. Compared with previous studied small nanoparticles, the electrophoretic translocation of negatively charged polystyrene (PS) nanoparticles (diameter ~100 nm) was investigated in solution using the Coulter counter principle in which the time-dependent nanopore current was recorded as the nanoparticles were driven across the nanopore. A linear dependence was found between current drop and biased voltage. An exponentially decaying function (td ~ e−v/v0) was found between the duration time and biased voltage. The interaction between the amine-functionalized nanopore wall and PS microspheres was discussed while translating PS microspheres. We explored also translocations of PS microspheres through amine-functionalized solid-state nanopores by varying the solution pH (5.4, 7.0, and 10.0) with 0.02 M potassium chloride (KCl). Surface functionalization showed to provide a useful step to fine-tune the surface property, which can selectively transport molecules or particles. This approach is likely to be applied to gene sequencing.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1255-6) contains supplementary material, which is available to authorized users.
Highlights
In recent years, the nanopores have become multifunction single-molecule detection devices [1]
Characterization of Nanopores The silicon nitride nanopores with ~150-nm diameter were fabricated by focused Ga ion beam (FIB), and the surface was covered by siloxane bonds, silanol (Si–OH) groups, and sialic acid
In this study, the silicon nitride nanopores were fabricated by FIB, which was functionalized with 3-APTES
Summary
The nanopores have become multifunction single-molecule detection devices [1]. The appearance of the nanoparticle in the pore apparently changes the nanopore’s resistance; it brings a sharp change of the current signal. The pulse frequency is related to the number and concentrations of nanoparticles, and the amplitude of current blockage is proportional to the size of the particles. Change of the current signal provides the size and concentrations of particles, but Nanoparticles with different sizes and surface charges have been detected by nanopores, and the results were consistent with other methods [2,3,4,5,6,7]. Saleh et al fabricated a microchip Coulter counter based on a quartz substrate which was used to detect single nanoscale colloidal particles, antibody binding to latex colloids, and to distinguish different sized colloids [8, 9]. More attention is focused on a chemically modified nanopore which is expected to have a major impact on bioanalysis and fundamental
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