Tuning the Properties of 2D Materials via Chemical Functionalizations—From Hairy Nanosheets to Their Hetero-Networks

The already exceptional properties of 2D materials can be further modulated, enriched and enhanced by interfacing them with ad hoc molecules via chemical functionalization. Molecules can be designed and synthesized to integrate both one or more anchoring moieties to guarantee immobilization on the basal plane or edges of 2D nanosheets, and one or more functional groups to tune the properties of the 2D material or impart them additional ones. The engineering of such hybrid structures represents a viable strategy to confer novel dynamic chemical and physical properties to 2D materials. [1]<br/><br/>In my lecture I will present our recent endeavour on the covalent functionalization of 2D materials by using different chemical reactions including the healing of point vacancies such as missing S, Seand Te atoms in the lattice of transition metal dichalcogenides nanosheets, including 2D MoS₂, WSe₂ and MoTe₂ by exploiting sulfur exposing molecules (equipped with thiols or disulfides end groups).[2] Moreover, liquid phase exfoliated 2D nanosheets of MoS₂ have been functionalized with dithiolated molecules has thereby generating networks with enhanced inter-sheet electronic cross talk.[3] Depending on the chemical structure of the molecular bridge linking adjacent nanosheets, enhancement in the charge transport through the film [4] or higher selectivity in the recognition process of specific analytes can be attained.[5] Furthermore, enhanced compositional complexity could be achieved by sequential deposition of a series of multiple 2D nanosheets and molecular bridge making use of a microfluidic strategy thereby generating hetero-networks and hetero-structures.<br/><br/>Alongside the tunable opto-electronic properties, these hybrids can display also programmable mechanical properties which can be exploited for the realization of unprecedented physical sensors for medical diagnosis and health monitoring, with sensitivities in the low-pressure or medium-pressure range. Example of flexible piezoresistive pressure sensors compatible with wearable technologies for digital healthcare, human-machine interfaces and robotics will be provided. [6]<br/><br/>The presented modular strategies provide a glimpse on the chemist’s toolbox to generate multifunctional 2D materials -based hybrids with ad-hoc properties to address key global challenges in electronics, sensing and energy applications.<br/><br/><br/>[1] For reviews: (a) <i>Chem. Soc. Rev. </i><b>2018</b> <i>47</i>, 6845-6888. (b) <i>Adv. Mater.</i> <b>2018</b>, <i>30</i>, 1706103. (c) <i>Chem. Rev.</i>, <b>2022</b>, <i>122</i>, 50–131.<br/>[2]<i> (a) Adv. Mater.</i> <b>2017</b>, <i>29</i>, 1606760. (b) <i>ACS Nano</i><b>, 2023, </b><i>17</i>, 17956. (c) <i>Adv. Funct. Mater. </i><b>2020</b>, <i>30</i>, 2005045. (d) ACS Nano in press<br/>[3] <i>Nat. </i><i>Nanotech.</i> <b>2021</b>, <i>16</i>, 592.<br/>[4] <i>Adv. </i><i>Mater.</i> <b>2023</b>, <i>35</i>, 2211157.<br/>[5] <i>Small </i><b>2023</b>, <i>19</i>, 2208100.<br/>[6] <i>Adv. Mater.</i> <b>2019</b>, <i>31</i>, 1804600