Directly and quickly detecting toxic gases in the air is urgently needed in industrial production and our daily life. However, the poor gas selectivity and low sensitivity under ambient conditions limit the development of gas sensors. In this work, we demonstrate that the penta-BeP2 monolayer is an excellent toxic gas sensor by using first-principles calculations. The calculated results show that the semiconducting penta-BeP2 monolayer can chemisorb toxic gas molecules (including CO, NH3, NO, and NO2) with distinct charge transfer (-0.182 to 1.129 e) but negligibly interact with ambient gas molecules (including H2, N2, H2O, O2, and CO2), indicating high gas selectivity for primary environmental gases. The calculated I-V curves show that the penta-BeP2 monolayer exhibits a fast response with toxic gas molecules. Upon interaction with CO, NH3, NO, and NO2 molecules at a bias voltage of 0.7 V, the currents are 10.23, 14.48, 32.10, and 129.90 times that of the pristine penta-BeP2 monolayer, respectively, which induces high sensitivity values of 9.23, 13.48, 31.10, and 128.90, respectively. Moreover, the moderate adsorption energies of all toxic gas molecules guarantee that the penta-BeP2 monolayer possesses good reversibility at room temperature with a short recovery time. Herein, all of our results indicate that the penta-BeP2 monolayer could be a superior candidate for sensing toxic gases with high selectivity, sensitivity, and reversibility.

Penta-BeP2 Monolayer: A Superior Sensor for Detecting Toxic Gases in the Air with Excellent Sensitivity, Selectivity, and Reversibility.

In this research, the adsorption of targeted noxious gases like H2S, HF and H2 on penta-PdAs2 monolayer are deeply studied by means of the density functional theory (DFT). After the capturing of three kind of pollutant gases (H2S, HF and H2), it is observed that, the electronic properties are slightly affected from the pristine one. In all cases, the physisorption interaction found with adsorption energy of - 0.49, - 0.39 and - 0.16 eV for H2S, HF and H2 gases, respectively. Which is exposed that H2S gas strongly absorbed on penta-PdAs2 nanosheet. In case of HF (H2) gas adsorbed systems, the obtained charge transfer is + 0.111 e (+ 0.037 e), revealed that the electrons are going to PdAs2 nanosheet from the HF (H2) molecules. Further, under the non-equilibrium Green's function (NEGF) theory, the IV response and sensitivity of absorbed H2S, HF and H2 have been discussed. The results demonstrate that the H2S molecules on PdAs2 has suitable adsorption strength and explicit charge transfer compared with other targeted molecules. Hence, our novel findings of H2S, HF and H2 targeted gas sensing on penta-PdAs2 nanosheet might provide reference-line to design modern gas sensor device at the nano-scale. 

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Detection of H2S, HF and H2 pollutant gases on the surface of penta-PdAs2 monolayer using DFT approach

Singlet fission is a new mechanistic pathway to overcome the Shockley–Queisser limit by generating twice the number of triplet excitons per singly absorbed photon in selected materials. The first step of the singlet fission (SF) is initiated by the capture of sunlight by chromophores in the visible region, which is the prime factor for subsequent transfer of the excited energies to the neighboring chromophores. The key electronic properties of organic chromophores for SF are dictated by the interplay of the electronic states involved in this process. The separation of two triplet excitons from the correlated triplet pair strongly depends on the molecular structure and their packing motif though either a covalent or noncovalent packing orientation that controls the efficiency of SF. In this Feature Article, we discuss the SF mechanism considering the thermodynamic condition, its correlation to the molecular structure, and, finally, its effects on the triplet yield generation from the first-principles computation. The discussion ranges from the single molecule to a dimeric pair of crystalline states in the context of technological importance and design principle rules for SF. Finally, we end this Feature Article with a brief overview of the experimental findings of our proposed chromophores in terms of the applicability in SF.

Krupa Lakhani

Papers

Dissociation of air pollutants on the uniform surface of pentagonal BeP2