Semiconducting Properties of Delaminated Titanium Nitride Ti4N3Tx MXene with Gate-Tunable Electrical Conductivity.

MXenes have garnered significant attention due to their atomically thin two-dimensional structure with metallic electronic properties. However, it has not yet been fully achieved to discover semiconducting MXenes to implement them into gate-tunable electronics such as field-effect transistors and phototransistors. Here, a semiconducting Ti4N3Tx MXene synthesized by using a modified oxygen-assisted molten salt etching method under ambient conditions, is reported. The oxygen-rich synthesis environment significantly enhances the etching reaction rate and selectivity of Al from a Ti4AlN3 MAX phase, resulting in well-delaminated and highly crystalline Ti4N3Tx MXene with minimal defects and high content of F and O, which led to its improved hydrophobicity and thermal stability. Notably, the synthesized Ti4N3Tx MXene exhibited p-type semiconducting characteristics, including gate-tunable electrical conductivity, with a current on-off ratio of 5 × 103 and a hole mobility of ∼0.008 cm2 V-1 s-1 at 243 K. The semiconducting property crucial for thin-film transistor applications is evidently associated with the surface terminations and the partial substitution of oxygen in the nitrogen lattice, as corroborated by density functional theory (DFT) calculations. Furthermore, the synthesized Ti4N3Tx exhibits strong light absorption characteristics and photocurrent generation. These findings highlight the delaminated Ti4N3Tx as an emerging two-dimensional semiconducting material for potential electronic and optoelectronic applications.

SABRE hyperpolarization of nicotinamide derivatives and their molecular dynamics properties.

Signal amplification by reversible exchange hyperpolarization explores the chemical structure and kinetic properties of nicotinamide derivatives. N-Benzyl nicotinamide and nicotinic acid hydrazide compounds display relatively fast dissociation rates of approximately 7-8 s-1 and long proton T1 relaxation times of 5-20 s, respectively. Consequently, these substrates exhibit remarkable signal enhancements, reaching approximately 175 and 102 fold, respectively, underscoring the efficacy of the hyperpolarization technique in elucidating the behavior of these compounds.