New ultrathin and multifunctional electromagnetic interference (EMI) shielding materials are required for protecting electronics against electromagnetic pollution in the fifth-generation networks and Internet of Things era. Micrometer-thin Ti 3 C 2 T x MXene films have shown the best EMI shielding performance among synthetic materials so far. Yet, the effects of elemental composition, layer structure, and transition metal arrangement on EMI shielding properties of MXenes have not been explored, despite the fact that more than 30 different MXenes have been reported and many more are possible. Here, we report on a systematic study of EMI shielding properties of 16 different MXenes, which cover single-metal MXenes, ordered double-metal carbide MXenes, and random solid solution MXenes of M and X elements. This is the largest set of MXene compositions ever reported in a comparative study. Films with thicknesses ranging from nanometers to micrometers were produced by spin-casting, spray-coating, and vacuumassisted filtration. All MXenes achieved effective EMI shielding (>20 dB) in micrometer-thick films. The EMI shielding effectiveness of sprayed Ti 3 C 2 T x film with a thickness of only ~40 nm reaches 21 dB. Adjustable EMI shielding properties were achieved in solid solution MXenes with different ratios of elements. A transfer matrix model was shown to fit EMI shielding data for highly conductive MXenes, but could not describe the behavior of materials with low conductivity. This work shows that many members of the large MXene family can be used for EMI shielding, contributing to designing ultrathin, flexible, and multifunctional EMI shielding films benefitting from specific characteristics of individual MXenes.

Wireless communication in the Internet of Things (IoT) is becoming ubiquitous with the large-scale deployment of the fifth-generation (5G) networks. [1] New communication protocols

Nanosecond-pulsed discharge in liquid nitrogen ignited using a needle electrode and positive 60 kV high voltage pulses was characterized using fast and shadow imaging, as well as optical emission spectroscopy. Estimation of temperature was done using molecular nitrogen emission of second positive system ro-vibrational transition spectra, and the maximum temperature increase is estimated to be ~60 K. We also report on the first observations of plasma-generated unstable material from liquid nitrogen, presumably a form of polynitrogen compound.

Thin films of two-dimensional MXene (Ti3C2Tx) are evaluated in terms of their conductivity over the radio frequency (RF) range of 1–10 GHz using a custom designed test fixture. A contactless method is developed for extracting the conductivity of MXene films of various thickness (1.0–4.3 μm) at RF frequencies. Open ended MXene transmission lines with various thicknesses are spray-coated on polyethylene terephthalate substrates capacitively coupled to a copper transmission line test fixture realized on a RT/duroid (filled polytetrafluoroethylene composite laminate) substrate to provide solderless repeatable RF connection. The extraction process is based on the least squares error method of curve fitting to minimize the difference between the full wave numerically simulated scattering parameters and the measured values of the test circuit for various samples. RF characterization was performed for three MXene samples, with thicknesses of about 1.0, 1.5, and 4.3 μm to extract the corresponding conductivity. Moreover, MXene performance was compared against copper and graphite films. The highest conductivity of 1.2 × 106 S/m was extracted for the 4.3 μm thick Ti3C2Tx film. The extracted MXene conductivity is used to predict the quality factor and efficiency of antennas. This study suggests that MXene films are attractive for RF applications and can be used as conductive layers on 3D-printed RF circuits.

Nanosecond-pulsed plasma ignited in liquid nitrogen is a unique tool for the synthesis of unconventional materials due to a combination of energetic properties of the discharge itself (high densities of reactive species, pressures and radiation) with the low temperature of the surrounding dense liquid. Here, we report on applications of such plasma for synthesis of a polymeric nitrogen compound, preliminarily identified as neutral or ionic N 6 , from sodium azide precursors.