Silicene Quantum Dots: Synthesis, Spectroscopy, and Electrochemical Studies

Rapid and Sensitive Identification and Discrimination of Bound/Unbound Ligands on Colloidal Nanocrystals via Direct Analysis in Real-Time Mass Spectrometry

Direct analysis in real-time mass spectrometry (DART-MS) has been applied to the characterization of colloidal nanocrystal surface ligands. The nanocrystals (NCs) in colloidal suspension were purified and deposited onto a solid substrate, and the solvent was allowed to evaporate. Ligand desorption was thermally stimulated using a temperature ramp from 30 °C up to 530 °C, and the desorbed ligands were introduced into a DART-MS instrument where metastable He atoms provide energy for ionization and fragmentation through the reaction with ambient vapors including O₂ and H₂O. The method allows the identification of ligand species with various functional groups, even in complex, mixed-ligand samples. Bound and unbound molecules can be distinguished based on the desorption temperature. In ideal cases, the desorption profile for a given molecule can be analyzed according to methods adapted from thermal desorption spectroscopy (TDS) to estimate desorption activation energy for NC-bound ligands. Results are presented and discussed for different nanocrystal and ligand types. The method is a promising complement to the range of existing tools for NC ligand analysis.

Imparting α-Borophene with High Work Function by Fluorine Adsorption: A First-Principles Investigation

Increasing the work function of borophene over a large range is crucial for the development of borophene-based anode materials for highly efficient electronic devices. In this study, the effect of fluorine adsorption on the structures and stabilities, particularly on the work function, of α-borophene (BBP), was systematically investigated via first-principles density functional theory. The calculations indicated that BBP was well-stabilized by fluorine adsorption and the work functions of metallic fluorine-adsorbed BBPs (F_n-BBPs) sharply increased with increasing fluorine content. Moreover, the work function of F-BBP was close to that of the frequently used anode material Au and even, for other F_n-BBPs, higher than that of Pt. Furthermore, we have comprehensively discussed the factors, including substrate deformation, charge transfer, induced dipole moment, and Fermi and vacuum energy levels, affecting the improvement of work function. Particularly, we have demonstrated that the charge redistribution of the substrate induced by the bonding interaction between fluorine and the matrix predominantly contributes to the observed increase in the work function. Additionally, the effect of fluorine adsorption on the increase in the work function of BBP was significantly stronger than that of silicene or graphene. Our results concretely support the fact that F_n-BBPs can be extremely attractive anode materials for electronic device applications.

Size engineering optoelectronic features of C, Si and CSi hybrid diamond-shaped quantum dots

Based on the density functional theory and many-body ab initio calculations, we investigate the optoelectronic properties of diamond-shaped quantum dots based graphene, silicene and graphene-silicene hybrid. The HOMO-LUMO (H-L) energy gap, the exciton binding energy, the singlet-triplet energy splitting and the electron-hole overlap are all determined and discussed. Smaller nanostructures show high chemical stability and strong quantum confinement resulting in a significant increase in H-L gap and exciton binding energy. On the other hand, the larger configurations are reactive which implies characteristics favorable to possible electronic transport and conductivity. In addition, the typically strong splitting between singlet and triplet excitonic states and the big electron-hole overlap make these QDs emergent systems for nanomedicine applications.

Beyond Graphene: Chemistry of Group 14 Graphene Analogues: Silicene, Germanene, and Stanene

Two-dimensional materials have been extensively studied over the last two decades as they represent a class of materials with properties applicable in catalysis, sensing, optical devices, nanoelectronics, supercapacitors, and semiconductors. The properties of 2D materials can be tuned by exfoliation into mono- or few-layered systems and mainly by surface modification, which can result, for example, in altering the band gap or enhancing material stability toward degradation. This review focuses on the derivatization of group 14 layered materials beyond graphene silicene, germanene, and stanene and summarizes their preparation as well as chemical and physical properties. This review provides the current state-of-the-art in the field and provides a perspective for future development in the field of chemical derivatization of 2D materials beyond graphene.