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Vertical integration of van der Waals (vdW) materials with atomic precision is an intriguing possibility brought forward by these two-dimensional (2D) materials. Essential to the design and analysis of these structures is a fundamental understanding of the vertical transport of charge carriers into and across vdW materials, yet little has been done in this area. In this report, we explore the important roles of single layer graphene in the vertical tunneling process as a tunneling barrier. Although a semimetal in the lateral lattice plane, graphene together with the vdW gap act as a tunneling barrier that is nearly transparent to the vertically tunneling electrons due to its atomic thickness and the transverse momenta mismatch between the injected electrons and the graphene band structure. This is accentuated using electron tunneling spectroscopy (ETS) showing a lack of features corresponding to the Dirac cone band structure. Meanwhile, the graphene acts as a lateral conductor through which the potential and charge distribution across the tunneling barrier can be tuned. These unique properties make graphene an excellent 2D atomic grid, transparent to charge carriers, and yet can control the carrier flux via the electrical potential. A new model on the quantum capacitance's effect on vertical tunneling is developed to further elucidate the role of graphene in modulating the tunneling process. This work may serve as a general guideline for the design and analysis of vdW vertical tunneling devices and heterostructures, as well as the study of electron/spin injection through and into vdW materials.

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β‐cyclodextrin (β‐CD) functionalized silver nanoparticles (AgNPs) and reduced graphene oxide (RGO) via one step electrochemical potentiodyanamic method has been prepared. Scanning electron microscopy, Energy‐Dispersive X‐ray spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry were used to study the role of β‐CD on preparation of AgNPs and RGO. RGO/β‐CD/AgNPs modified GCE showed good electrochemical activity towards electro‐oxidation of hydrazine in terms of decreasing the over potential and increasing the peak current. The kinetic parameters such as electron transfer coefficient (α) and diffusion coefficient (Do) of the modified electrode towards hydrazine were determined to be 0.66 and 0.97×10−6 cm2 s−1, respectively. The LOD of our sensor was many folds lower than that of recommended concentration of hydrazine in drinking water by United States Environmental Protection Agency and World Health Organization. The sensor exhibited a wide linear range from 0.08 to 1110 µM and a very low detection limit (LOD) of 1.4 nM. In addition, the sensor selectively determined hydrazine even in the presence of common interferents.