Mass production of one-dimensional, V₂Se₉ crystals, was successfully synthesized using the solid-state reaction of vanadium and selenium. Through the mechanical exfoliation method, the bulk V₂Se₉ crystal was easily separated to nanoribbon structure and we have confirmed that as-grown V₂Se₉ crystals consist of innumerable single V₂Se₉ chains linked by van der Waals interaction. The exfoliated V₂Se₉ flakes can be controlled thickness by the repeated-peeling method. In addition, atomic thick nanoribbon structure of V₂Se₉ was also obtained on a 300 nm SiO₂/Si substrate. Scanning Kelvin probe microscopy analysis was used to explore the variation of work function depending on the thickness of V₂Se₉ flakes. We believe that these observations will be of great help in selecting suitable metal contacts for V₂Se₉ and that a V₂Se₉ crystal is expected to have an important role in future nano-electronic devices.

The fundamental issues related to the formation of mechanical cracks and the chemical residue during the transfer process of large-area CVD graphene by polymeric carrier-films are addressed in this work.

Electron–phonon coupling in monolayer graphene results in a modification of its Raman spectra upon charge transfer processes induced by interaction with its chemical environment or the presence of strain or defects in its structure. Modification of Raman spectra is examined in order to develop ultra-sensitive biosensing techniques for the detection, identification, differentiation and classification of bacteria associated with infectious diseases. Specifically, the electrochemical properties of top gated monolayer graphene on SiO₂/Si substrates, in the absence and presence of interaction with Gram-positive bacteria (Enterococcus faecalis, Bacillus subtilis) and Gram-negative bacteria (Escherichia coli and Salmonella typhimurium), are probed by Raman spectroscopy in an applied voltage range from 0 V to 3 V. Bacteria and monolayer graphene interactions are thus electrostatically tuned. The resulting correlation of specific bacterial chemical properties and Raman spectral characteristics is reported, along with density functional theory simulations of the charge transfer mechanism. The intensities of the G and D Raman vibrational modes are modulated as a function of the applied voltage in the presence of bacteria, but remain unchanged in bare monolayer graphene. A fingerprint region is also identified in the range of 200 cm⁻¹ to 600 cm⁻¹, with disulfide bonds observed at 490 cm⁻¹, associated with bacterial membrane proteins. Significantly, such observations are detected even in the absence of bacterial culturing, a time-consuming step.

Needle-like single crystalline wires of TaSe₃ were massively synthesized using the chemical vapor transport method. Since the wedged-shaped single TaSe₃ molecular chains were stacked along the b-axis by weak van der Waals interactions, a few layers of TaSe₃ flakes could be easily isolated using a typical mechanical exfoliation method. The exfoliated TaSe₃ flakes had an anisotropic planar structure, and the number of layers could be controlled by a repeated peeling process until a monolayer of TaSe₃ nanoribbon was obtained. Through atomic force and scanning Kelvin probe microscope analyses, it was found that the variation in the work function with the thickness of the TaSe₃ flakes was due to the interlayer screening effect. We believe that our results will not only help to add a novel quasi-1D block for nanoelectronics devices based on 2D van der Waals heterostructures, but also provide crucial information for designing proper contacts in device architecture.

Transition metal carbides (TMCs) have high melting points, hardness, and chemical stabilities in acidic media. In this work, a chemical vapor deposition method using CH₄ as a carbon source and reducing agent was employed to make an NbC film. NbCl₅ carried by Ar gas was used as an Nb precursor. An NbC thin film, deposited on a c-plane sapphire, exhibited a preferential orientation of the (111) plane, which can be explained by domain-matching epitaxy. A nanoindentation test showed that the NbC film with the preferential orientation of the (111) plane was stronger than that with a random orientation. Moreover, the results showed that H₂, which is conventionally used as a reducing agent in NbC synthesis, degraded the crystallinity and hardness of the fabricated NbC.