| Jan 13, 2025 |
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(Nanowerk News) Combining the best of different crystals to obtain the ultimate material is the motto that drives two-dimensional (2D) materials research. 2D structures are typically built by atomic deposition and weakly bonded to each other by van der Waals interactions. In the last few years, an alternative approach for creating robust 2D structures has been introduced, involving the chemical linkage of nanosheets of distinct materials. Now, researchers are leveraging this technique to create improved devices with a richer optoelectronic response.
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In a recent collaboration among IMDEA Nanociencia, INMA-Zaragoza, ICMM and ARAID Foundation, researchers have synthesized and characterised a 2D structure composed of palladium nanosheets and molybdenum disulfide (MoS2). MoS2 is one of the most popular 2D materials because of its facile exfoliation and excellent optoelectronic properties. It features a well-defined bandgap in its 2H type and good absorbance in the visible range of the spectrum.
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However, a notable limitation of MoS2 is its poor absorbance in the infrared. The broadband optical detection ability, especially from ultraviolet to the near infrared range, is critical for applications including medical monitoring, video imaging or optical communications.
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In their latest work, researchers have combined MoS2 with palladium nanosheets to create 2D structures with broadband detection that provide absorbance in the infrared. The prototype device, consisting on a single layer of MoS2 covalently functionalised with palladium nanosheets, showed an enhanced optoelectronic response, both in terms of width and intensity, in comparison with a van der Walls structure with the same components.
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Researchers proved that the enhancement stemmed from the chemically bonded interface between the two materials. The spectroscopic analysis of the palladium-MoS2 device revealed an electronic interaction between the two materials that evidence the effectiveness of the chemical connection.
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| Illustration of a molybdenum disulphide layer attached to a palladium layer via functional molecule. (Image: Ramiro Quirós)
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The device reported here presents three key features. First, a MoS2 large lateral size in the micrometer range combined with ultrathin thickness of less than 5 nanometres. Second, the palladium nanosheets 2D morphology that enables a strong absorbance in the infrared region. Last, the chemical connection between the two nanomaterials facilitated via a bifunctional molecule.
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The work, recently published in Small (“Chemically-Linked Heterostructures of Palladium Nanosheets and 2H-MoS2“), highlights the advantages of the covalent connection. First, the device is robust against solvents or thermal processes. Further, the covalent connection between its 2D components improves the device’s optoelectronic response in comparison to its van der Waals counterpart. These findings demonstrate that covalent linked 2D materials hold promise for its application in broad-band photodetection.
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