Mo-Based Layered Nanostructures for the Electrochemical Sensing of Biomolecules

Abstract

Mo-based layered nanostructures are two-dimensional (2D) nanomaterials with outstanding characteristics and very promising electrochemical properties. These materials comprise nanosheets of molybdenum (Mo) oxides (MoO₂ and MoO₃), dichalcogenides (MoS₂, MoSe₂, MoTe₂), and carbides (MoC₂), which find application in electrochemical devices for energy storage and generation. In this feature paper, we present the most relevant characteristics of such Mo-based layered compounds and their use as electrode materials in electrochemical sensors. In particular, the aspects related to synthesis methods, structural and electronic characteristics, and the relevant electrochemical properties, together with applications in the specific field of electrochemical biomolecule sensing, are reviewed. The main features, along with the current status, trends, and potentialities for biomedical sensing applications, are described, highlighting the peculiar properties of Mo-based 2D-nanomaterials in this field.

Keywords: Mo-layered compounds; biomolecules; electrochemical sensors; nanosheets.

Figure 1

(a) Number of papers mentioning the use of molybdenum (Mo)-based materials for biomolecule sensing; (b) Distribution of Mo-based 2D layered materials for electrochemical biomolecule sensing.

Figure 2

Examples of top-down and bottom-up strategies for the synthesis of 2D layered nanostructures: (a) mechanical exfoliation of layered host materials, (b) chemical intercalation induced exfoliation, (c) chemical vapor deposition (CVD) growth, and (d) wet-chemical self-assembly. Scanning electron microscopy (SEM) images of 2D nanomaterials obtained with the corresponding techniques: (e,g,h) TiO₂ and (f) VO₂ nanosheets.

Figure 3

(a) Schematization of the ultrasonication process for obtaining 2D-MoS₂ nanosheets; (b) SEM images showing 2D-MoS₂ deposited on the surface of a gold electrode; (c) Raman spectra carried out at 785 nm. The Inset shows the intensity of the Raman band as a function of MoS₂ loading. Adapted with permission from reference [49].

Figure 4

(A) UV–vis-NIR absorption spectra of (a) MoO₃ nanosheet and (b) MoO_3−x nanosheet dispersions. (B) XRD pattern of (a) the MoO_3−x nanosheets, and (b) JCPDs card no. 21-0569 of hexagonal phase of MoO₃. (C) AFM image of MoO_3−x nanosheets (scale bar, 500 nm). (D) Height profile. Reprinted with permission from reference [55].

Figure 5

Schematization of electrochemical techniques used for detection of biomolecules. Adapted with permission from reference [56].

Figure 6

(a) Cyclic voltammetry (CV) of the bare substrate and atomic layer deposition (ALD)-developed 2D α-MoO₃ in the absence and presence of 5 mM H₂O₂. (b) CV curves of 2D α-MoO₃ at different concentration of H₂O₂. (c) Amperometric current response to H₂O₂ concentration variation. (d) Current vs. H₂O₂ concentration. Reprinted with permission from reference [64].

Figure 7

(a) Schematic representations of Au-Pd/MoS₂/GCE sensor. (b) Differential pulse voltammetry (DPV) curves for different H₂O₂ concentrations. (c) DPV peak current as a function of H₂O₂ concentration. (d) Amperometric responses for different glucose concentrations. (e) Plot of amperometric response vs. the logarithm of glucose concentration. Reprinted with permission from reference [60].

Figure 8

(A) DPV curves of S-MoSe₂/NSG/Au/MIP/GCE to dopamine (DA) concentrations from 5 × 10⁻⁸ to 1 × 10⁻³ mol/L. (B) Peak current vs. DA concentration. Reprinted with permission from reference [83].

Figure 9

Scheme of the DPV signal of MoS₂-polyaniline sensors with completely matched and single base mismatched DNA. Reprinted with permission from reference [90].

Figure 10

(A) Low and (B) high magnification FESEM images of MoS₂ grown Al foil. Reprinted with permission from reference [93].