Thermionic electron emission in the 1D edge-to-edge limit

Thermionic emission is a tunneling phenomenon, which depicts that electrons on the surface of a conductor can be pulled out into the vacuum when they are subjected to high electrical tensions while being heated hot enough to overtake their work functions. This principle has led to the great success of the so-called vacuum tubes in the early 20th century. To date, major challenges still remain in the miniaturization of a vacuum channel transistor for on-chip integration in modern solid-state integrated circuits. Here, by introducing nano-sized vacuum gaps (~200 nm) in a van der Waals heterostructure, we successfully fabricated a one-dimensional (1D) edge-to-edge thermionic emission vacuum tube using graphene as the filament. With the increasing collector voltage, the emitted current exhibited a typical rectifying behavior, with the maximum emission current reaching 200 pA and an On-Off ratio of 103. Besides, it is found that the maximum emission current was proportional to the number of the layers of graphene. Our results expand the studies of the nano-sized vacuum tube to an unexplored physical limit of 1D edge-to-edge emission, and hold great promise for future nano-electronic systems based on it.

Influence of accelerating gap configuration on parameters of a forevacuum plasma-cathode source of pulsed electron beam

The research of influence of accelerating gap configuration on parameters of a forevacuum plasma-cathode source of a pulsed low-energy (up to 10 keV) large-radius electron beam is presented. An increase in cell sizes of a mesh emission electrode increases electron emission efficiency, but leads to a decrease in electric strength of an accelerating gap. Larger cell sizes of a mesh extractor provide higher electron beam current. An increase in the length of the accelerating gap first leads to an increase in the electron emission efficiency, but when optimal value is reached, a further increase in the length leads to a decrease in the emission efficiency. This optimal length of the accelerating gap is about 25 mm. However, the electron emission efficiency changes relatively small (within 15%). The dependencies of maximum emission current and maximum operating gas pressure on the length of acceleration gap is similar to the dependence for the emission efficiency, but the gap length much stronger influences on these maximum values. Moreover, the optimal length, at which maximum emission current or maximum pressure is provided, is depended on gas pressure (for current) or emission current (for pressure), accelerating voltage and pulse duration.

Combustion temperature analysis in a fluidized-bed reactor by utilizing palm oil biomass for a renewable energy

Biomass from palm oil is a renewable energy source that can be utilized and has very promising availability. Biomass energy is a renewable and sustainable energy that can replace conventional (fossil) fuels. The main objective of the experiment in this article is to analyze the combustion temperature, emissions, and efficiency of palm oil biomass fuel to use and applied in rural/remote areas. The palm oil biomass used in this study is palm kernel shells, empty fruit bunches, oil palm midrib, and oil palm fibers. The experiments in the research carried out in a fluidized-bed combustion chamber designed explicitly with capacities of up to 5 kg of biomass. The results of operations on fluidized-bed when the valve is open 100%, 75%, and 50% with overall palm oil biomass show a high combustion temperature. The highest combustion temperature was recorded in the TC test for 100% open valves with 3 kg biomass of 943°C. While the minimum combustion temperature obtained on TF2 at 50% open valve with 1 kg biomass of 619°C, overall combustion temperatures in this experiment showed high results. The maximum emission for O2 is 20.4% which is obtained at 50% open valve, while for CO2 the maximum emission is produced when 100% open valve is 19.9% with a biomass weight of 1 kg and 3 kg, respectively. The yield for maximum combustion efficiency when using 1 kg of biomass recorded at 50% open valve was 94.9%. While the minimum efficiency of 87.7% is obtained when the valve is 100% open with biomass of 2 kg. As the biomass fuel used in fluidized-bed increases, the combustion temperature also increases significantly.

An Attempt to Boost Molecular Descriptors with Quantum-Derived Features in Prediction of Maximum Emission Wavelengths of Chromophores

The following research assesses the capability of machine learning in predicting maximum emission wavelength of organic compounds. The predictions are based on structure descriptors and fingerprints widely applied in cheminformatics. In an attempt to further improve accuracy, developed machine learning models were enriched with quantum mechanics derived features. Multi linear, gradient boosting and random forest regressions were applied. Computers were trained and tested with database of experimental data of optical properties.

An Attempt to Boost Molecular Descriptors with Quantum-Derived Features in Prediction of Maximum Emission Wavelengths of Chromophores

The following research assesses the capability of machine learning in predicting maximum emission wavelength of organic compounds. The predictions are based on structure descriptors and fingerprints widely applied in cheminformatics. In an attempt to further improve accuracy, developed machine learning models were enriched with quantum mechanics derived features. Multi linear, gradient boosting and random forest regressions were applied. Computers were trained and tested with database of experimental data of optical properties.

Enhanced brightness and electron affinity of terrylenediimide with sulfone-bridged substituents on the bay region

Electron-withdrawing sulfone-bridged substituents endow terrylenediimide dyes with low LUMO levels, strong electron affinity, red-shifted maximum emission, and high photoluminescence quantum yield.

Multicolor Emission and Photophysical Properties of Proton-Responsive Cyclometallated Iridium(III) Complex in Transparent Cation-Exchange Membrane

A transparent film allowing tunable multicolor emission based on a composite of an organometallic compound and a cation-exchange membrane has been developed, in which the cyclometallated iridium(III) complex [IrIII(4Py-ppy)3] (=tris[2-(2-pyridinyl-κN)-4-(4-pyridinyl)phenyl-κC]iridium) (1) with pH-dependent emission wavelengths has been incorporated into Nafion by cation exchange. Soaking Nafion in the solution of 1 for 24 h and exposed to buffers at pH 2, 4, and 10 resulted in maximum emission wavelengths of 587, 560, and 503 nm, respectively. The photophysical properties of 1@Nafion were also enhanced, as its maximum emission wavelength was more blue-shifted than those of 602, 564, and 503 nm in the solutions. The emission quantum yields (Φ) and lifetimes (τ) of 1@Nafion prepared under an acidic condition were up to Φ = 1.8% and τ = 0.11, 0.92 μs, which are considerably higher than the corresponding solutions of Φ = 0.5% and τ = 0.02, 0.18 μs. This is attributed to the fact that 1 is surrounded by the polymer chains of Nafion and immobilized in a relatively rigid medium, which hinders non-radiative deactivation such as thermal relaxation.