Self-assembled monolayer-protected nanoparticles are promising candidates for applications, such as sensing and drug delivery, in which the molecular ligands' interactions with the surrounding environment play a crucial role. We recently showed that, when gold nanoparticles are coated with a binary mixture of immiscible ligands, ordered ribbon-like domains of alternating composition spontaneously form and that their width is comparable with the size of a single solvent molecule. It is usually assumed that nanoparticles' solubility depends solely on the core size and on the molecular composition of the ligand shell. Here, we show that this is not always the case. We find that the ligand shell morphology affects the solubility of these nanoparticles almost as much as the molecular composition. A possible explanation is offered through a molecular dynamics analysis of the surface energy of monolayers differing only in their domain structure. We find that the surface free energy of such model systems can vary significantly as a function of ordering, even at fixed composition. This combined experimental and theoretical study provides a unique insight into wetting phenomena at the nano- and subnanometer scale.

Tunability of the electronic properties of two-dimensional bilayer hetero structures of transitionmetal dichalcogenides (i.e., MX 2-M 0 X 0 2 with (M, M 0 ¼ Mo, W; X, X 0 ¼ S, Se) is investigated. Application of both strain and electric field is found to modify the band gap and carrier effective mass in the hybrid bilayers considered. The calculated results based on density functional theory suggest that the tensile strain considerably changes the band gap of semiconducting bilayers; it makes the band gap to be indirect, and later initiates the semiconductor-to-metal transition. Application of the external electric fields, on the other hand, shows asymmetric variation in the band gap leading to the closure of the gap at about 0.5-1.0 V/Å. Tuning of the band gap and carrier effective mass in such a controlled manner makes the hybrid bilayers of transition metal dichalcogenides to be promising candidates for application in electronic devices at nanoscale.

Electronic, optical and transport properties of DNA nucleobase adsorbed on monolayer MoS 2 has been investigated using density functional theory. A significant polarization in MoS 2 has been observed upon DNA nucleobase adsorption. The nucleobase origin of the modulation in the electronic properties is clearly captured in the simulated STM measurements. The electronic transport through conjugate systems allows the clear distinction of nucleobase from one another.The modulation in electron energy loss spectra and transport properties of pristine MoS 2 has been observed on nucleobase adsorption which could serve as a fingerprint for realization of next generation DNA sequencing devices. We believe that these results also bring out a possibility of fabrication of MoS 2 based biosensors for selective detection of DNA bases in real long-chain DNA molecules.

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