Trifluoromethylation of 2D Transition Metal Dichalcogenides: A Mild Functionalization and Tunable p-Type Doping Method

Chemical modification is a powerful strategy for tuning the electronic properties of 2D semiconductors. Here we report the electrophilic trifluoromethylation of 2D WSe2 and MoS2 under mild conditions using the reagent trifluoromethyl thianthrenium triflate (TTT). Chemical characterization and density functional theory calculations reveal that the trifluoromethyl groups bind covalently to surface chalcogen atoms as well as oxygen substitution sites. Trifluoromethylation induces p-type doping in the underlying 2D material, enabling the modulation of charge transport and optical emission properties in WSe2. This work introduces a versatile and efficient method for tailoring the optical and electronic properties of 2D transition metal dichalcogenides.

Direct Characterization of Buried Interfaces in 2D/3D Heterostructures Enabled by GeO2 Release Layer

Inconsistent interface control in devices based on two-dimensional materials (2DMs) has limited technological maturation. Astounding variability of 2D/three-dimensional (2D/3D) interface properties has been reported, which has been exacerbated by the lack of direct investigations of buried interfaces commonly found in devices. Herein, we demonstrate a new process that enables the assembly and isolation of device-relevant heterostructures for buried interface characterization. This is achieved by implementing a water-soluble substrate (GeO2), which enables deposition of many materials onto the 2DM and subsequent heterostructure release by dissolving the GeO2 substrate. Here, we utilize this novel approach to compare how the chemistry, doping, and strain in monolayer MoS2 heterostructures fabricated by direct deposition vary from those fabricated by transfer techniques to show how interface properties differ with the heterostructure fabrication method. Direct deposition of thick Ni and Ti films is found to react with the monolayer MoS2. These interface reactions convert 50% of MoS2 into intermetallic species, which greatly exceeds the 10% conversion reported previously and 0% observed in transfer-fabricated heterostructures. We also measure notable differences in MoS2 carrier concentration depending on the heterostructure fabrication method. Direct deposition of thick Au, Ni, and Al2O3 films onto MoS2 increases the hole concentration by >1012 cm-2 compared to heterostructures fabricated by transferring MoS2 onto these materials. Thus, we demonstrate a universal method to fabricate 2D/3D heterostructures and expose buried interfaces for direct characterization.

In vivo hydroxylation of 3H-acetanilide--evaluation of a new radiospirometric method in the rat

The proposed in vivo methodology for the investigation of hydroxylation rates consists of of the i.v. administration of tritiated substrates and the collection of tritiated water (HTO) from exhaled air as a measure of HTO accumulation in body water. Specifically, HTO was assessed in exhaled water after i.v. administration of 3H-acetanilide. Over a wide range the half lives of accumulation of HTO in exhaled water (T50) were almost identical with the half lives of elimination of 3H-acetanilide in blood, evaluated by an inverse isotope dilution method (r = 0.96, N = 18). Average T50 amounted to 29 min in controls, was reduced to 20 min after enzyme induction by phenobarbital or 3-methylcholanthrene, and prolonged to 45, 46 and 66 min after bile duct ligation, portacaval shunt and a single dose of ethanol, respectively. It is concluded that the chosen pharmacokinetic approach corrects for the NIH-shift and the results adequately reflect changes in acetanilide hydroxylation related to enzyme induction or inhibition and to liver pathology.