covalent bonding
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Crystals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 88
Author(s):  
Anthony Ruth ◽  
Michael Holland ◽  
Angus Rockett ◽  
Erin Sanehira ◽  
Michael Irwin ◽  
...  

Metal halide perovskite materials (MHPs) are a family of next-generation semiconductors that are enabling low-cost, high-performance solar cells and optoelectronic devices. The most-used halogen in MHPs, iodine, can supplement its octet by covalent bonding resulting in atomic charges intermediate to I− and I0. Here, we examine theoretically stabilized defects of iodine using density functional theory (DFT); defect formation enthalpies and iodine Bader charges which illustrate how MHPs adapt to stoichiometry changes. Experimentally, X-ray photoelectron spectroscopy (XPS) is used to identify perovskite defects and their relative binding energies, and validate the predicted chemical environments of iodine defects. Examining MHP samples with excess iodine compared with near stoichiometric samples, we discern additional spectral intensity in the I 3d5/2 XPS data arising from defects, and support the presence of iodine trimers. I 3d5/2 defect peak areas reveal a ratio of 2:1, matching the number of atoms at the ends and middle of the trimer, whereas their binding energies agree with calculated Bader charges. Results suggest the iodine trimer is the preferred structural motif for incorporation of excess iodine into the perovskite lattice. Understanding these easily formed photoactive defects and how to identify their presence is essential for stabilizing MHPs against photodecomposition.


2021 ◽  
Author(s):  
Zichen Qin ◽  
Yiying Zhu ◽  
Yu Xiang

SARS-CoV-2 uses its spike protein receptor-binding domain (RBD) to interact with the angiotensin-converting enzyme 2 (ACE2) receptor on host cells. Inhibitors of the RBD-ACE2 interaction are therefore promising drug candidates in treating COVID-19. Here, we report a covalent bonding aptamer that can block the RBD-ACE2 interaction and neutralize SARS-CoV-2 pseudovirus infection by forming covalent bonds on RBD, resulting in more than 25-fold enhancement of pseudovirus neutralization efficacy over the original binding aptamer. The chemically modified aptamer is equipped with sulfur(VI) fluoride exchange (SuFEx) modifications and covalently targets important RBD residues within the RBD-ACE2 binding interface, including Y453 and R408. The covalent bonding is highly specific to RBD over other proteins such as human serum albumin (HSA), ACE2 and immunoglobulin G1 (IgG1) Fc. Our study demonstrates the promise of introducing covalent inhibition mechanisms for developing robust RBD-ACE2 inhibitors against SARS-CoV-2 infection.


Molecules ◽  
2021 ◽  
Vol 26 (24) ◽  
pp. 7688
Author(s):  
Igor K. Petrushenko ◽  
Nikolay A. Ivanov ◽  
Konstantin B. Petrushenko

Recently, the capture of carbon dioxide, the primary greenhouse gas, has attracted particular interest from researchers worldwide. In the present work, several theoretical methods have been used to study adsorption of CO2 molecules on Li+-decorated coronene (Li+@coronene). It has been established that Li+ can be strongly anchored on coronene, and then a physical adsorption of CO2 will occur in the vicinity of this cation. Moreover, such a decoration has substantially improved interaction energy (Eint) between CO2 molecules and the adsorbent. One to twelve CO2 molecules per one Li+ have been considered, and their Eint values are in the range from −5.55 to −16.87 kcal/mol. Symmetry-adapted perturbation theory (SAPT0) calculations have shown that, depending on the quantity of adsorbed CO2 molecules, different energy components act as the main reason for attraction. AIMD simulations allow estimating gravimetric densities (GD, wt.%) at various temperatures, and the maximal GDs have been calculated to be 9.3, 6.0, and 4.9% at T = 77, 300, and 400 K, respectively. Besides this, AIMD calculations validate stability of Li+@coronene complexes during simulation time at the maximum CO2 loading. Bader’s atoms-in-molecules (QTAIM) and independent gradient model (IGM) techniques have been implemented to unveil the features of interactions between CO2 and Li+@coronene. These methods have proved that there exists a non-covalent bonding between the cation center and CO2. We suppose that findings, derived in this theoretical work, may also benefit the design of novel nanosystems for gas storage and delivery.


2021 ◽  
Vol 144 ◽  
pp. 107412
Author(s):  
T.V. Bezrodna ◽  
A.A. Ishchenko ◽  
V.I. Bezrodnyi ◽  
A.M. Negriyko ◽  
L.F. Kosyanchuk ◽  
...  
Keyword(s):  

2021 ◽  
Author(s):  
Li Cao ◽  
Lei Wang
Keyword(s):  

Author(s):  
S. Vijayalakshmi ◽  
S. Mahalakshmi ◽  
M. Muthujothi

Electronic properties of orthorhombic SSM ([Formula: see text] and monoclinic SSM ([Formula: see text] are investigated using the first-principles calculation. The half-metallic behavior that leads to the mixed ionic and electronic conductivity (MIEC) property is identified in orthorhombic SSM. In addition, the strong covalent bonding between [Formula: see text]-p and [Formula: see text]-s orbitals of orthorhombic SSM is identified from the PDOS plot. The strong covalent bonding enhances the [Formula: see text] molecular adsorption on Mn atom. On the other hand, monoclinic SSM shows the pure conducting behavior and there is no covalent bonding between Mn and O atoms. Thus, the results suggest that the half-metal Sm[Formula: see text]Sr[Formula: see text]MnO3 might be a suitable cathode material for intermediate-temperature solid oxide fuel cells.


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