Chemically-Linked Heterostructures of Palladium Nanosheets and 2H-MoS₂

The burgeoning field of 2D heterostructures targets the combination of 2D materials with 3D, 1D, or 0D nanomaterials. Among the most popular 2D materials, the 2H polytype of molybdenum disulfide (MoS₂) features a well-defined bandgap that becomes direct at the monolayer level, which can be exploited for photodetection. A notable limitation of 2H-MoS₂ is its curtailed absorbance beyond the visible range. Here, a covalently-linked Pd nanosheet (PdNS)/functionalized MoS₂ (f-MoS₂) heterostructure is introduced, leveraging PdNS infrared-absorbing properties to surmount this constraint. A bifunctional molecule, featuring a maleimide for attachment to MoS₂ and a phenyl bromide for connection to PdNS, enables the synthesis of the heterostructure. Comprehensive spectroscopic and microscopic characterization shed light on the structure of PdNS@f-MoS₂ and the electronic interaction between its components. Prototype devices show an enhancement in the width and intensity of the optoelectronic response of PdNS@f-MoS₂ in the infrared, up to 1700 nm. In comparison, a van der Waals heterostructure with the same components shows poorer photoresponse. The results prove that the covalent linkage of metal nanostructures to 2D materials is a promising approach to build mixed-dimensional heterostructures.