Exploring the Sensing Potential of g-C3N4 versus Li/g-C3N4 Nanoflakes toward Hazardous Organic Volatiles: A DFT Simulation Study.

Ab initio calculations were performed to determine the sensing behavior of g-C3N4 and Li metal-doped g-C3N4 (Li/g-C3N4) quantum dots toward toxic compounds acetamide (AA), benzamide (BA), and their thio-analogues, namely, thioacetamide (TAA) and thiobenzamide (TAA). For optimization and interaction energies, the ωB97XD/6-31G(d,p) level of theory was used. Interaction energies (Eint) illustrate the high thermodynamic stabilities of the designed complexes due to the presence of the noncovalent interactions. The presence of electrostatic forces in some complexes is also observed. The observed trend of Eint in g-C3N4 complexes was BA > TAA > AA > TBA, while in Li/g-C3N4, the trend was BA > AA > TBA > TAA. The electronic properties were studied by frontier molecular orbital (FMO) and natural bond orbital analyses. According to FMO, lithium metal doping greatly enhanced the conductivity of the complexes by generating new HOMOs near the Fermi level. A significant amount of charge transfer was also observed in complexes, reflecting the increase in charge conductivity. NCI and QTAIM analyses evidenced the presence of significant noncovalent dispersion and electrostatic forces in Li/g-C3N4 and respective complexes. Charge decomposition analysis gave an idea of the transfer of charge density between quantum dots and analytes. Finally, TD-DFT explained the optical behavior of the reported complexes. The findings of this study suggested that both bare g-C3N4 and Li/g-C3N4 can effectively be used as atmospheric sensors having excellent adsorbing properties toward toxic analytes.

Nonlinear Optical Properties and Phototunable Absorption of a Substituted Dihydroazulene-Vinylheptafulvene Pair of Photochromes.

Quantum calculations were used to study UV-vis absorption properties and nonlinear optical characteristics of a variety of substituted dihydroazulene (DHA)/vinylheptafulvene (VHF) photoswitches. The absorption properties are substantially based on the position and nature of the substituent. In general, electron-donating groups cause red shifts compared to the parent compound. Any electron-withdrawing group, on the other hand, would generate a blue shift. Furthermore, the steric effect at some positions is accountable for the loss of planarity and, as a response, a decrease in electronic conjugation within the molecule, which in most cases result in blue shifts in maximum absorption. The purpose of this research is to investigate the influence of substitution at the seven-membered ring of the DHA/VHF system on the absorption spectra and nonlinear optical characteristics of dihydroazulene photoswitches. UV-vis spectra and hyperpolarizability are determined since a prospective photoswitch should have a minimum overlap of absorption spectra from both isomers. Furthermore, the differential in hyperpolarizability between DHA and VHF is critical for practical applications.

Chiral Recognition of Amino Acids Using CC2 Porous Organic Cages.

Enantiomers have the same physical properties but different chemical properties due to the difference in the orientation of groups in space and thus Chiral discrimination is quite necessary, as an enantiomer of drug can have lethal effects. In this study, we used the CC2 cage for chiral discrimination of amino acids using density functional theory. The results indicated the physisorption of amino acids in the central cavity of the cage. Among the four selected amino acids, proline showed maximum interactions with the cage and maximum chiral discrimination energy is also observed in the case of proline that is 2.78 kcal/mol. Quantum theory of atoms in molecules and noncovalent interaction index analyses showed that the S enantiomer in each case has maximum interactions. The charge transfer between the analyte and surface is further studied through natural bond orbital analysis. It showed sensitivity of cage for both enantiomers, but a more pronounced effect is seen for S enantiomers. In frontier molecular orbital analysis, the least EH-L gap is observed in the case of R proline with a maximum charge transfer of -0.24 e-. Electron density difference analysis is carried out to analyze the pattern of the charge distribution. The partial density of state analysis is computed to understand the contribution of each enantiomer in overall density of the complexes. Our results show that S-CC2 porous organic cages have a good ability to differentiate between two enantiomers. S-CC2 porous organic cages efficiently differentiated the S enantiomer from the R enantiomers of selected amino acids.

Therapeutic potential of oxo-triarylmethyl (oxTAM) as a targeted drug delivery system for nitrosourea and fluorouracil anticancer drugs; A first principles insight.

In this study, oxygenated triarylmethyl (oxTAM) is investigated by DFT calculations as a drug carrier framework for Nitrosourea (NU) and Fluorouracil (FU) drugs. Based on the adsorption analysis i.e., energies and distances between interacting atoms, it is found that oxTAM exhibits excellent carrier abilities for the delivery of FU (-1.53 eV & 2.00 Å) and NU (-1.33 eV & 2.12 Å) drugs. NCI and QTAIM results indicate the presence of hydrogen bonding in drug-carrier complexes. The values of dipole moment and global chemical descriptors show the significant reactivity of oxTAM for NU and FU drugs. Based on electronic property analysis, FU@oxTAM has a higher adsorption trend for complexation with oxTAM as compared to NU@oxTAM. Moreover, FU can easily release from the carrier due to the decreasing adsorption stability after protonation under an acidic environment as well as a short recovery time observed for the oxTAM carrier surface. Keeping in view all the above parameters, we inferred that oxTAM can serve as a potential drug delivery system for anticancer drugs including, Nitrosourea and Fluorouracil drugs.

Nano-porous C4N as a toxic pesticide's scavenger: A quantum chemical approach.

The sensing affinity of C4N is the most fascinating topic of research due to its excellent chemical and electronic properties. Moreover, owing to the highly active porous cavity, C4N can easily accommodate foreign molecules. Herein, we studied the adsorption properties of carbamate insecticides (CMs) namely, Dimetalin (DMT), Carbanolate (CBT), Isolan (ISO) and Propoxur (PRO) using density functional theory calculations. All the results are calculated at widely accepted ωB97XD functional along with 6-31G(d, p) basis set. The calculated counterpoise corrected interaction energy of the reported complexes ranges between -20.05 and -27.04 kcal/mol, however, the interaction distances are found to be higher than 2.00 Å. The values of interacting parameters depict that the carbamate molecules are physisorbed via noncovalent interactions that can easily be reversible. Moreover, the binding of selected insecticides notably changes the electronic structure of C4N. The electronic changes are characterized by the energies of HOMO & LUMO, their energy gaps and CHELPG charge transfer. The charge density difference between C4N surface and carbamate pesticides are characterized by EDD and CDA analysis. Moreover, the ab initio molecular dynamic study reveals that the complexes are stable even at 500 K. The photochemical sensing properties of C4N are estimated by time dependent UV-Vis calculations. The high sensitivity of C4N towards considered analytes enable it to act as a promising sensor for toxic pesticides.

Electrochemical sensing behavior of graphdiyne nanoflake towards uric acid: a quantum chemical approach.

Though the gas sensing applications of graphdiyne have widely reported; however, the biosensing utility of graphdiyne needs to be explored. This study deals with the sensitivity of graphdiyne nanoflake (GDY) towards the uric acid (UA) within the density functional framework. The uric acid is allowed to interact with graphdiyne nanoflake from all the possible orientations. Based on these interacting geometries, the complexes are differentiated with naming, i.e., UA1@GDY, UA2@GDY, UA3@GDY, and UA4@GDY (Fig. 1). The essence of interface interactions of UA on GDY is derived by computing geometric, energetic, electronic, and optical properties. The adsorbing affinity of complexes is evaluated at ωB97XD/6-31 + G(d, p) level of theory. The stabilities of the complexes are quantified through the interaction energies (Eint) with reasonable accuracy. The calculated Eint of the UA1@GDY, UA2@GDY, UA3@GDY, and UA4@GDY complexes are - 31.13, - 25.87, - 20.59, and - 16.54 kcal/mol, respectively. In comparison with geometries, it is revealed that the higher stability of complexes is facilitated by π-π stacking. Other energetic analyses including symmetry adopted perturbation theory (SAPT), noncovalent interaction index (NCI), and quantum theory of atoms in molecule (QTAIM) provide the evidence of dominating dispersion energy in stabilizing the resultant complexes. The HOMO-LUMO energies, NBO charge transfer, and UV-vis analysis justify the higher electronic transition in UA1@GDY, plays a role of higher sensitivity of GDY towards the π-stacked geometries over all other possible interaction orientations. The present findings bestow the higher sensitivity of GDY towards uric acid via π-stacking interactions. Fig. 1 Optimized geometries (with interaction distances in Å) of UA@GDY complexes.

Spectrum of Joint Deformities in Children with Juvenile Idiopathic Arthritis.

OBJECTIVE: To determine the frequency and types of joint deformities in children with juvenile idiopathic arthritis and their association with clinical parameters and rheumatoid factor. STUDY DESIGN: Cross-sectional study. PLACE AND DURATION OF STUDY: Rheumatology Outpatient Clinic, the Children's Hospital and the Institute of Child Health, Lahore, from September 2014 to February 2015. METHODOLOGY: All patients of both genders of less than 16 years of age, who fulfilled the International League of Association for Rheumatology (ILAR) criteria for Juvenile Idiopathic Arthritis (JIA), were enrolled in this study. Their demographic data, duration of disease at the time of presentation, types of JIA, various joint deformities and rheumatoid factor (RF) were documented. Statistical analysis of data was done on SPSS version 16. Chi-square test was applied to determine the association of clinical deformity with age of patients, disease duration at presentation, types of JIA and RF. RESULTS: Out of 70 patients enrolled during the study period, 51.4% were boys with mean age at presentation being 9.44 ±3.89 years (2-7 years) and median duration of disease being 24 months (interquartile range 42 months). Forty patients (57.1%) had joint deformities. Most common joints involved were hand (50%), wrist (50%), and knee (35.7%). The common types of joint deformities were boutonniere deformity (28.6%), ulnar deviation of wrist (28.6%), fixed flexion deformity of wrist (22.9%), and knee (31.4%). The most common type of JIA was polyarthritis RF negative with or without deformity. There was a strong association of deformities with older age of patients at presentation (p=0.036), longer duration of disease at presentation (p=0.028), polyarthritis (RF seronegative / seropositive) (p=0.013), and seropositivity (p=0.04). CONCLUSION: More than 50% patients with JIA have joint deformities. Joint deformities are more likely to be seen in children with long-standing disease, those with polyarthritis JIA and seropositive patients.