Noble metal-coated MoS2 nanofilms with vertically-aligned 2D layers for visible light-driven photocatalytic degradation of emerging water contaminants

Abstract

Two-dimensional molybdenum disulfide (2D MoS2) presents extraordinary optical, electrical, and chemical properties which are highly tunable by engineering the orientation of constituent 2D layers. 2D MoS2 films with vertically-aligned layers exhibit numerous 2D edge sites which are predicted to offer superior chemical reactivity owing to their enriched dangling bonds. This enhanced chemical reactivity coupled with their tunable band gap energy can render the vertical 2D MoS2 unique opportunities for environmental applications that go beyond the conventional applications of horizontal 2D MoS2 in electronics/opto-electronics. Herein, we report that MoS2 films with vertically-aligned 2D layers exhibit excellent visible light responsive photocatalytic activities for efficiently degrading organic compounds in contaminated water such as harmful algal blooms. We demonstrate the visible light-driven rapid degradation of microcystin-LR, one of the most toxic compounds produced by the algal blooms, and reveal that the degradation efficiency can be significantly improved by incorporating noble metals. This study suggests a high promise of these emerging 2D materials for water treatment, significantly broadening their versatility for a wide range of energy and environmental applications.

Scalable lateral heterojunction by chemical doping of 2D TMD thin films

“…The resistance of these devices varied from 185 to 490 MΩ with an average of 347 MΩ as shown in the box plot of Fig. 1 c. The measured values of resistance for our MoS 2 devices are consistent with what has been reported in the literature 34 , 49 – 51 , 53 , 54 . After characterizing the as-prepared samples, we doped the MoS 2 film by immersing it in BV solution for 36 h (see “Method” section for detail) and measured their electrical transport properties.…”

Improving Electrochemical Pb2+ Detection Using a Vertically Aligned 2D MoS2 Nanofilm

“…It is also interesting to note that the integral intensity ratio of the A 1g mode to the E 1 2g mode (A 1g /E 1 2g ) is very high ∼4.4, indicating the dominant presence of out-of-plane vibrations (A 1g ). This high value of A 1g /E 1 2g is a signature of the enlarged degree of freedom for lattice vibration in vertically aligned 2D layers, indicating the pronounced exposure of layer edge sites on the film surface. , The detailed crystalline structure of MoS 2 films with vertically aligned 2D layers was inspected by TEM characterization. A cross-sectional view of the MoS 2 film/Au taken in an annular dark-field TEM (ADF-TEM) mode is shown in Figure (d), revealing a distinguishable image contrast in between the MoS 2 and Au regions.…”

Centimeter-scale Green Integration of Layer-by-Layer 2D TMD vdW Heterostructures on Arbitrary Substrates by Water-Assisted Layer Transfer

“…2D TMDs obtained in this manner exhibit horizontally-aligned basal planes of well-resolved layers; for example, horizontally-aligned 2D MoS 2 layers of ~7–8 nm thickness obtained from the sulfurization of ~2.5 nm thick Mo have been confirmed by atomic force microscopy (AFM) and cross-sectional TEM characterization (Supplementary Information, S4). Maintaining the small thickness of metal seeds is critically important to ensure that 2D TMD layers grow in horizontal orientation as identified in our previous studies 32,34 . In this case, weak molecular vdW attraction will be responsible for holding the 2D basal planes of diminished defect density to the SiO 2 substrate surface, enabling facile water penetration in between them.…”