DFT Results Research Articles

Development of green solvents for efficient post-combustion CO2 capture with good regeneration performance

CO2 emission from post-combustion causes severe impacts on global environment. Hence, to minimize greenhouse effect, it is urgent to develop green solvents for CO2 capture. Herein, deep eutectic solvents (DES) were prepared using glycine (Gly) and proline (Pro) as hydrogen bond acceptors and monoethanolamine (MEA) and ethyl diethanolamine (MDEA) as hydrogen bond donors. The MEA-based DESs exhibited better CO2 uptake capability than MDEA-based DESs. The introduction of ethylene glycol (EG) to [Gly][MEA]/[Pro][MEA] not only enhances the absorption kinetics but also improves the regeneration ability. [Gly][MEA][EG] shows a better CO2 capture performance than [Pro][MEA][EG], reaching to 0.2485 g-CO2/g-DES after 6 h absorption at room temperature. [Gly][MEA][EG] shows an excellent tolerance to water content and CO2 concentration in flue gases and exhibits a robust performance in regeneration with no sustainable solvent loss after 10 cycles of recycles. NMR, FTIR and DFT results indicate that CO2 interacts with DESs via the formation of carbamate through the amine group in MEA and amino acids and via the formation of CO32-/HCO3- via the –OH group in EG. This study offers a novel green solvent for CO2 capture, which is feasible for industrial applications.

Phosphorus-doped porous perovskite LaFe1-xPxO3-δ nanosheets with rich surface oxygen vacancies for ppb level acetone sensing at low temperature

• O v defect-rich phosphorus-doped porous perovskite LaFeO 3-δ nanosheets were prepared. • Characterizations and DFT results indicate that doping with P induces O v defects. • Perovskite LaFe 1-x P x O 3-δ sensor has excellent acetone sensing properties at 180 °C. • O v defects reconfigure electron distribution and promote gas adsorption. Perovskite-type oxide semiconductors (ABO 3 ) with defective conduction properties have been regarded as highly promising gas-sensitive materials due to their abundant structural types. However, pure ABO 3 gas sensors usually have suboptimal sensing response due to low specific surface area and few adsorption sites. Recently, surface oxygen vacancies (O v ) defects have been shown to be a remarkably effective way to enhance the sensing response of gas sensors by increasing the number of adsorption sites and changing the energy level structure. In view of the above, herein, P-doped perovskite LaFe 1-x P x O 3-δ (x = 0.005, 0.01, 0.03, 0.05) with abundant O v defects were prepared by sol–gel method and fabricated as sensors for the acetone detection. Characterization and test results show that LaFe 0.99 P 0.01 O 3-δ with porous nanosheet structure has excellent acetone gas-sensitive performance. Compared to pure LaFeO 3 gas sensor, the optimal operating temperature of LaFe 0.99 P 0.01 O 3-δ is reduced to 180 °C and response value is improved nearly twofold, whose limit of detection is even at the ppb level. Crucially, the results of electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) verify that the sensing characteristics of the LaFe 1-x P x O 3-δ sensor are strongly correlated with the O v defect. In addition, further theoretical analysis shows that P doping in LaFeO 3 induces O v defects and modulates frontier electron orbital energy levels of the material, thus increasing the chemisorbed oxygen species and enhancing the intermolecular interactions. In this work, the vital function of O v defects in perovskite-type gas sensors is highlighted, which also provides an effective and feasible way to improve the performance of gas sensors.

Strong Co-O-Si bonded ultra-stable single-atom Co/SBA-15 catalyst for selective hydrogenation of CO2 to CO

The design of efficient nonnoble metal catalysts for the hydrogenation of CO2 is a challenge. Cobalt-based catalysts demonstrate high activity in methanation reactions but low selectivity and stability in reverse water-gas shift reactions. Superstable Co2+ single atoms supported on SBA-15 with 2.6 wt% Co loading are synthesized by atomic layer deposition. The catalyst performs 99% CO selectivity with a turnover frequency of 304.6 mol CO2/mol Co/h at 600°C and stabilizes for 500 h. The performance is ascribed to the strong interaction between Co single atoms and SBA-15 through Co-O-Si bonds that maintain the valence state of Co2+ during the reaction. Based on DFT and experimental results, a reaction mechanism is proposed involving the dissociative activation of H2 on single Co atom sites, adsorption of CO2, and the formation of CO and H2O. The shift between the tetrahedral and the octahedral field of Co2+ single atoms drives the catalytic cycle.

Crystal structures of N-[4-(tri-fluoro-meth-yl)phen-yl]benzamide and N-(4-meth-oxy-phen-yl)benz-amide at 173 K: a study of the energetics of conformational changes due to crystal packing.

As a part of our study of the syntheses of aryl amides, the crystal structures of two benzamides were determined from single-crystal X-ray data at 173 K. Both crystal structures contain mol-ecular units as asymmetric units with no solvent in the unit cells. Crystal structure I, TFMP, is the result of the crystallization of N-[4-(tri-fluoro-meth-yl)phen-yl]benzamide, C14H10F3NO. Crystal structure II, MOP, is composed of N-(4-meth-oxy-phen-yl)benzamide, C14H13NO2, units. TFMP is triclinic, space group P , consisting of two mol-ecules in the unit cell related by the center of symmetry. MOP is monoclinic, space group P21/c, consisting of four mol-ecules in the unit cell. Both types of mol-ecules contain three planar regions; a phenyl ring, an amide planar region, and a para-substituted phenyl ring. The orientations of these planar regions within the asymmetric units are compared to their predicted orientations, in isolation, from DFT calculations. The aryl rings are tilted approximately 60° with respect to each other in both experimentally determined structures, as compared to 30° in the DFT results. These conformational changes result in more favorable environments for N-H⋯O hydrogen bonding and aryl ring π-stacking in the crystal structures. Inter-molecular inter-actions were examined by Hirshfeld surface analysis and qu-anti-fied by calculating mol-ecular inter-action energies. The results of this study demonstrate that both hydrogen bonding and dispersion are essential to the side-by-side stacking of mol-ecular units in these crystal structures. Weaker dispersion inter-actions along the axial directions of the mol-ecules reveal insight into the melting mechanisms of these crystals.

Oxidation reactions of carbaryl in aqueous solutions

Hydroxyl radical induced oxidation of carbaryl has been studied using steady state photolysis followed by high-resolution mass spectrometry (LC-Q-TOF-MS), pulse radiolysis, and theoretical (DFT) calculations. The reaction of ●OH with carbaryl resulted in a number of hydroxylated adduct radicals (λmax - 330 nm and 390 nm; k2 - 1.2 × 1010 dm3 mol-1 s-1). The DFT calculations and results obtained from LC-Q-TOF-MS analysis shows the possible addition of ●OH at C1 (energetically most stable) and C7 positions of carbaryl leading to the generation of resonance stabilized hydroxycyclohexadienyl-type radicals as the immediate intermediates, which eventually converted into naphthol and a hydroxylated naphthols. LC-Q-TOF-MS results also revealed the formation of other hydroxylated derivatives and naphthoquinones that are most likely originated from the consecutive ●OH attack on the initially formed products. Naphthoquinones are found to undergo ring opening and the corresponding products are identified. The reaction of SO4●- with carbaryl, on the other hand, results the radical cation of parent molecule (λmax - 320 nm and 390 nm) which exhibits reasonable stability in the pulse radiolysis timescale. Total organic carbon (TOC) analysis after H2O2/UV photolysis revealed that nearly 70% of the organic content is mineralized after 35 min of irradiation, which demonstrates the potential application of oxidative methods towards the degradation of carbaryl.

Density functional theory investigation to surface modification of boron nitride nanotubes.

We studied the boron nitride nanotube (BNNT) modification through pyrrole molecule properties by implementing B3LYP and M06-2X methods. The results of DFT show that the pyrrole molecule has a strong interaction with BNNT, showing that its adsorption onto the nanotube surface is corresponding to chemical functionalization. Also, after the chemical modification, density of states shows that there is a slight modification in the BNNT electronic properties. Furthermore, electrical conductivity of functionalized BNNT (f-BNNT) was increased compared to BNNT, which shows that an increase in the electron-donating nature of functional groups increases the functionalization energy. Maintaining the BNNT electronic properties along with the improved solubility gives us an idea that BNNT chemical modification through pyrrole can affect the way BNNTs are purified.

Mechanism of biochar functional groups in the catalytic reduction of tetrachloroethylene by sulfides

In recent years, biochar has become of considerable interest for environmental applications, it can be used as a catalyst for sulfides reduction of perchloroethylene, but the crucial role of biochar properties played in catalyzing dechlorination remained ambiguous investigation. To pinpoint the critical functional groups, the modified biochars were respectively produced by HNO3, KOH and H2O2 with similar dimensional structures but different functional groups. Combined with the adsorption and catalytic results of different biochars, the acid-modified biochar had the best catalytic performance (99.9% removal) due to the outstanding specific surface area and ample functional groups. According to characterization and DFT results, carboxyl and pyridine nitrogen exhibited a positive correlation with the catalytic rate, indicating that their contribution to catalytic performance. Customizing biochar with specific functional groups removed depth demonstrated that the carboxyl was essential component. Further, alkaline condition was conducive to catalytic reduction, while tetrachloroethylene cannot be reduced under acidic conditions, because HS− and S2− mainly existed in alkaline environment and the sulfur-containing nucleophilic structure formed with biochar was more stable under this condition. Overall, this study opens new perspectives for in situ remediation by biochar in chlorinated olefin polluted anoxic environment and promotes our insight of modifying for biochar catalyst design.

Regulating the coordination environment of Ru single-atom catalysts and unravelling the reaction path of acetylene hydrochlorination

In this work, DFT calculations were used firstly to simulate the nitrogen coordinated metal single-atom catalysts (M-Nx SACs, M = Hg, Cu, Au, and Ru) to predict their catalytic activities in acetylene hydrochlorination. The DFT results showed that Ru-Nx SACs had the best catalytic performance among the four catalysts, and Ru-Nx SACs could effectively inhibit the reduction of ruthenium cation. To verify the DFT results, Ru-Nx SACs were fabricated by pyrolyzing MOFs in-situ spatially confined metal precursors. The N coordination environment could be controlled by changing the pyrolysis temperature. Catalytic performance tests indicated that low N coordination number (Ru–N2, Ru–N3) exhibited excellent catalytic activity and stability compared to RuCl3 catalyst. DFT calculations further revealed that Ru–N2 and Ru–N3 had a tendency to activate HCl at the first step of reaction, whereas Ru–N4 tended to activate C2H2. These findings will serve as a reference for the design and control of metal active sites.

Multidimensional insight into the corrosion inhibition of salbutamol drug molecule on mild steel in oilfield acidizing fluid: Experimental and computer aided modeling approach

The study aims to establish detailed surface adsorption of expired salbutamol drug molecule as an emerging anticorrosion additive for mild steel corrosion in oilfield acidizing fluid. To achieve this, wide experimental data from weight loss, potentiodynamic polarization, and DFT studies were considered, statistically analyzed, and modeled. Artificial neural network-genetic algorithm (ANN-GA) and adaptive neural fuzzy inference system-genetic algorithm (ANFIS-GA) were utilized as optimization tools considering multiple inputs and a single output variable (MISO). Maximum inhibition efficiencies of 80 %, 89 % and 84 % were obtained from weight loss, potentiodynamics study and elcectrochemical impedance spectroscopy at concentration of 0.4 g/L-1SB and temperature of 323 K respectively. The results obtained from the polarization test confirmed SB as a mixed-type inhibitor and the kinetic studies fit well in the Langmuir isotherm for surface adsorption. The surface analysis via FTIR, SEM/EDAX, and AFM strongly complements the DFT results. In the soft computing method without (GA) via artificial neural network (ANN) and adaptive neural fuzzy inference system (ANFIS), optimal prediction of 79.74 and 81.24 % was attained at varying operating conditions. The predictive capabilities of the two methodologies were compared in terms of coefficient of determination (R2), chi square (χ2), root mean square error (RMSE) and model predictive error (MPE). Based on the statistical indices obtained, much credence was giving to ANFIS as the best predictive model over ANN. Effect of time and inhibitor concentration are the most significant parameters for the prediction of salbutamol drug as a potential anticorrosion additive for mild steel in oilfield acidizing conditions.

Flotation separation of smithsonite from calcite using an amino-acid collector

• ZnCO 3 rather than CaCO 3 could be efficiently floated by C16Gly at pH 10. • The DFT method successfully predicted the flotation selectivity of C16Gly. • C16Gly reacted with the ZnCO 3 /CaCO 3 surface forming bidentate binding models. • C16Gly preferred to binding with the ZnCO 3 surface rather than the CaCO 3 surface. Flotation separation of smithsonite (ZnCO 3 ) from calcite (CaCO 3 ) is not commonly satisfied using traditional fatty acids, and thus, more selective collectors are required. In this regard, a new collector, N-hexadecanoylglycine (C16Gly) was used to selectively collect ZnCO 3 from CaCO 3 in this work. The flotation selectivity of C16Gly was predicted by DFT calculations. The calculation results showed that the C16Gly anion adsorbed on the ZnCO 3 /CaCO 3 surface via two Zn–O/Ca–O bonds. Moreover, as the new Zn–O bonds were more covalent than Ca–O bonds, the adsorption of C16Gly on the ZnCO 3 surface was more stable. Therefore, this collector may be used as a specific collector for ZnCO 3 rather than for CaCO 3 . The DFT results were confirmed by experimental results. Single-mineral flotation and contact angle results both suggested that C16Gly efficiently floated ZnCO 3 rather than CaCO 3 at pH ≥ 10. As for the 1:1 ZnCO 3 and CaCO 3 mixture, the Zn recovery was much higher than that of CaO with 3 × 10 -4 mol/L of collector at pH 10, and the separation efficiency reached 64.53% under the same conditions. XPS analysis revealed that Zn/Ca atoms on ZnCO 3 /CaCO 3 surface were involved in the reaction of C16Gly with the mineral surface. In addition, a good coverage of C16Gly on the ZnCO 3 surface was observed by the time-of-flight secondary ion mass spectrometry system. In contrast, this collector was not found on the CaCO 3 surface due to its poor adsorption capacity. These experimental results confirmed that C16Gly is a promising collector for the selective flotation of ZnCO 3 from CaCO 3 and DFT calculations are a powerful tool to predict the flotation behavior of C16Gly for the ZnCO 3 –CaCO 3 system.

DFT and COSMO-RS studies on dicationic ionic liquids (DILs) as potential candidates for CO2 capture: the effects of alkyl side chain length and symmetry in cations.

A few studies on CO2 capture using dicationic ionic liquids (DILs) show that they are more promising absorbents for CO2 capture than monocationic ILs (MILs). Ion-ion, ion-CO2 and DIL molecule-CO2 interactions are important for understanding the performance-structure-property relationships for the rational design of DILs for CO2 capture applications. However, the role of these interactions in determining CO2 solubility in DILs is unclear. In this study, we used DFT methods to understand these interactions in three selected DILs)considering the effects of alkyl side chain length and symmetry in cations (by exploring different aspects, such as the electronic and geometrical structures, topological properties and the strength and nature of interactions, charge transfer, etc. The results showed that the most suitable solvent for CO2 is the symmetric DIL with a longer side chain length, i.e. [Bis(mim)C5-(C4)2][NTf2]2. In addition, we used the COSMO-RS calculations to obtain the macroscopic solubility of CO2 in the studied DILs, which was in good agreement with the DFT results. Gas selectivity results calculated using COSMO-RS theory indicated that the selectivity of CO2 from H2, CO and CH4 gases decreases slightly with increasing the length of side alkyl chains.

Understanding the high performance of PdSn–TaN(tantalum nitride)/C electrocatalysts for the methanol oxidation reaction: coupling nitrides and oxophilic elements

Palladium-modified transition metal nitrides (TaN) are investigated as electrochemical methanol oxidation reaction (MOR) catalysts. Combined in situ ATR-SEIRAS and DFT results demonstrate PdSn–TaN/C as an effective material to enhance MOR activity.

Water-gas shift reaction over supported Au nanoparticles

The water–gas shift (WGS) reaction rates per total mole of Au at 120 °C, 7% CO, 22% H2O, 8.5% CO2, 37% H2 decrease in the order Au/Anatase ∼ Au/Anatase001 (uniform anatase TiO2 single crystals with 64 per cent of the more {001} facets) ∼ Au/P25 ∼ Au/P25-WGC (obtained from the World Gold Council) ∼ Au/Rutile > Au/ZrO2 > Au/CeO2 > Au/ZnO when compared at the same number average Au particle size (d) and vary as ∼ d-3. From high resolution transmission electron microscopy images, the geometry of Au nanoparticles on these catalysts resembled truncated cubo-octahedra. A physical model of Au nanoparticles as truncated cubo-octahedra was used to calculate that the fractions of surface, perimeter and corner sites to the total Au sites vary as d-0.7, d-1.8 and d-2.9, respectively. Thus, the variation in the WGS reaction rate per total mole of Au (∼d-3) correlates well with the corner sites (d-2.9) allowing us to determine that the dominant active sites for these catalysts are the low coordinated metallic corner Au sites. In addition, as the apparent H2O order increases and the apparent activation energy decreases, the WGS reaction rate per total mole of Au systematically decreases for Au nanoparticles supported on anatase, anatase001, P25, rutile, ZrO2, CeO2, ZnO and Al2O3 at near 120 °C. Density functional theory calculations were carried out over Au nano-rods supported on rutile TiO2(100) and α-Al2O3(0001) surfaces to elucidate the differences in reactivity for the most reactive (Au/TiO2) and least reactive (Au/Al2O3) catalysts. Water preferentially adsorbs and dissociates at the Lewis acid- Lewis base Ti4+-Ob and Al3+-Ob site pairs at the Au/TiO2(110) and Au/α-Al2O3 interfaces with activation energies of 0.25 eV and 0.20 respectively. These barriers are significantly lower than those to activate water on the corner sites of unsupported Au nanoparticles (1.48 eV). The prediction that both the TiO2 and Al2O3 readily dissociate water supports the experimental findings that the support plays an important role in activating the water in the WGS reaction. The subsequent oxidation of CO appears to proceed at the Au/support interface via the reaction of CO adsorbed on Au with the OH on the support. DFT results indicate that OH binds 0.4 eV stronger to Al3+ sites at the Au/Al2O3 interface perimeter than to Ti4+ sites at the Au/TiO2 interface perimeter. As such, the barrier for OH to react with CO at an adjacent Au site is 0.52 eV higher for Au/Al2O3 (0.85 eV) than for Au/TiO2 (0.33 eV). The theoretical results suggest that the oxidation of CO is rate-limiting on Al2O3 whereas both the water dissociation as well as CO oxidation limit the rate on TiO2. This is consistent with the near first order CO dependence of the measured rates over both Au/TiO2 and Au/Al2O3 as well as the changes in the water reaction orders over Au/TiO2 (−0.2 to −0.5) and Au/Al2O3 (0.5 to 0.8).

Ruddlesden–Popper Oxychlorides Ba3Y2O5Cl2, Sr3Sc2O5Cl2, and Sr2ScO3Cl: First Examples of Oxide-Ion-Conducting Oxychlorides

Oxide-ion conductors are attractive materials due to their wide applications such as solid oxide fuel cells (SOFCs). Crucial to the developments of the applications is the discovery of a class of oxide-ion conductors. Some Ruddlesden–Popper (RP) oxychlorides are expected to show high oxide-ion conductivity, because they have larger free and lattice volumes than RP oxides, leading to low activation energies. Here, we discover RP oxychlorides Ba3Y2O5Cl2, Sr3Sc2O5Cl2, and Sr2ScO3Cl as a class of oxide-ion conductors. Rietveld analyses of X-ray powder diffraction data indicate that Ba3Y2O5Cl2 and Sr3Sc2O5Cl2 are tetragonal I4/mmm n = 2 RP phases and that Sr2ScO3Cl is a tetragonal P4/nmm n = 1 RP phase. The predominant conducting species in Ba3Y2O5Cl2, Sr3Sc2O5Cl2, and Sr2ScO3Cl is strongly suggested to be the oxide ion by (i) direct-current (DC) polarization measurements, (ii) electrolyte domains observed in the oxygen partial pressure dependence of DC electrical conductivities at constant temperatures, and (iii) wide optical band gaps. DFT calculations of Ba3Y2O5Cl2 show a lower energy barrier for oxide-ion migration than that for chloride-ion migration, which supports the oxide-ion conduction. The DFT results indicate that oxide ions in Ba3Y2O5Cl2 two-dimensionally migrate mainly through equatorial oxygen O1 sites along the O1–O1 edge of the YO5 square pyramid. The oxide-ion conductivity of Ba3Y2O5Cl2 is considerably higher than that of Sr3Sc2O5Cl2, mainly due to a lower activation energy for conductivity, which can be ascribed to the larger free and lattice volumes of Ba3Y2O5Cl2. The DFT energy barrier for oxide-ion migration and experimental activation energy for bulk conductivity in Ba3Y2O5Cl2 are as low as those of a leading oxide-ion conductor La0.9Sr0.1Ga0.95Mg0.05O3−δ. Thus, the present work suggests that RP oxychlorides are a class of potential oxide-ion conductors.

Efficient removal of Cr (VI) by modified sodium alginate via synergistic adsorption and photocatalytic reduction

Conventional photocatalytic removal of hexavalent chromium (Cr (VI)) suffers from low metal uptake capacity, expensive photocatalysts, and slow desorption of trivalent chromium from the catalyst surface. In this study, calcium chloride and iron(III) nitrate were used to cross-link with polyethyleneimine grafted sodium alginate (SA) to acquire two materials, named as SPC and SPF, respectively, for the efficient removal of Cr (VI) from aqueous solutions via adsorption and photocatalytic reduction. FT-IR, DFT, and XPS results indicated that polyethyleneimine was successfully grafted onto the SA matrix and could electrostatically attractted hexavalent chromium anions in solution. Fe (III) cross-linking forms a highly porous structure at ambient temperature, which could overcome the polysaccharide collapse in the dehydration process. The UV–vis DRS, EIS, and photocurrent density characterizations of SA, SPC, and SPF suggested that SPF has smaller charge transfer resistance and is conducive to the separation of photogenerated charges, thus SPF exhibited superior performance in the photocatalytic reduction of Cr (VI). As a result, SPF is an efficient photocatalyst for the removal of Cr (VI) and provides new sights on polysaccharide-based photocatalysts applications.

A Heterostructured Sulfonated CNT/Sulfur/CNT Cathode for Promoting the Binary Conversion of Polysulfides in Lithium‐Metal Batteries

AbstractThe shuttle effect of lithium polysulfides (LiPS) and sluggish redox kinetics hinder the commercialization of lithium‐sulfur (Li−S) batteries. Herein, we design a lightweight and multifunctional multi‐walled carbon nanotube (CNT)/sulfur/lithiated sulfonated CNT (M/S/M‐SO3Li) electrode as energy storage devices. Flexible CNT films ensure continuously electron/ion transmission and serve as LiPS shielding layer. Moreover, guided by DFT and experimental results, SO3 groups exert a vital adsorption effect toward sulfur species but not NH4+ groups. The SO3 groups can not only employ as LiPS immobilizer by Li−O bands between LiPS and SO3, but also serve as multifunctional electrocatalyst to propel LiPS conversion via generating thiosulfate and polythionate and Li2S decomposition by reducing reaction overpotential. As expected, M/S/M‐SO3Li electrode exhibits prominent rate capability (723.5 mAh g−1 at 5 C), high sulfur loading (7.09 mAh cm−2 at 5.0 mg cm−2 sulfur), favorable anti‐self‐discharge capabilities (rest for 72 h at 0.5 C with 2.17 %).

Steps toward Rationalization of the Enantiomeric Excess of the Sakurai-Hosomi-Denmark Allylation Catalyzed by Biisoquinoline N,N'-Dioxides Using Computations.

Allylation reactions of aldehydes are chemical transformations of fundamental interest, as they give direct access to chiral homoallylic alcohols. In this work, we focus on the full computational characterization of the catalytic activity of substituted biisoquinoline-N,N′-dioxides for the allylation of 2-naphthaldehyde. We characterized the structure of all transition states as well as identified the π stacking interactions that are responsible for their relative energies. Motivated by disagreement with the experimental results, we also performed an assessment of 34 different density functional methods, with the goal of assessing DFT as a general tool for understanding this chemistry. We found that the DFT results are generally consistent as long as functionals that correctly account for dispersion interactions are used. However, agreement with the experimental results is not always guaranteed. We suggest the need for a careful synergy between computations and experiments to correctly interpret the data and use them as a design tool for new and improved asymmetric catalysts.

A new tetramine bis(2-naphthol)-derivative fluorescent chemosensor for aluminum ion (Al3+)

A new tetramine bis(2-naphthol)-derivative was synthesized and its structure investigated by 1H- and 13C NMR, UV-Vis absorption and fluorescence spectroscopies, as well as through density functional theory calculations (including time-dependent DFT). The effect of a series of metal ions (Ag+, Al3+, Ba2+, Ca2+, Cd2+, Co2+, Cs +, Cu2+, Fe2+, Fe3+, K+, Mg2+, Mn2+, Ni2+, Pb2+ and Zn2+) on the fluorescence spectra of the synthesized compound was then investigated and it was observed that the presence of Al3+ ion causes a strong increase in the fluorescence emission of the ligand, by about 70 times. This exceptional intensification is specific for Al3+ within the whole series of ions investigated, together with the selectivity found for many of the remaining ions (in particular the ions of Groups I and II of the Periodic Table and Mn2+), makes the compound a promising candidate to act as chemosensor for Al3+. Possible structures for the ligand:Al3+ complex are suggested based on DFT results. TD-DFT calculations performed on these structures suggest that the fluorescence enhancement upon binding of Al3+ to the ligand results most probably from metal-to-ligand charge transfer where the acceptor groups of the ligand are the naphthol moieties.

Fluorescein dye derivative: Synthesis, characterization, quantum chemical and promising antimicrobial activity studies

AbstractThe dimethyl sulfite as an alkylating as well as alkoxylating reagent is well known in synthetic organic as well as organometallic chemistry for a long time. Herein, we have utilized dimethyl sulfite as an alkylating reagent and reacted with fluorescein derivative, N‐fluorescein‐lactam‐hydrazine (B). This reaction leads to the generation of tetramethylated fluorescein lactam hydrazine (A). The newly designed and synthesized molecule (A) has been characterized by 1H, 13C NMR and HRMS data. The antimicrobial activity of the synthesized alkylated fluorescein derivative has been tested against E. coli, P. aeruginosa, Salmonella typhimurium and S. aureus microbial agents. Time‐kill assay results also confirmed that fluorescein derivative is a potent antimicrobial agent and revealed that the time‐kill assay of fluorescein derivative is value‐added than the well‐known antibiotic. In addition, quantum chemical study was used to analyze its activity trend and correlated with the experimental data. The computed results of DFT revealed that the lipophilicity as well as the LUMO‐HOMO band gap (ΔELUMO‐HOMO = 4.75 eV) of compound A make it more suitable as an antimicrobial agent to match with in vitro antimicrobial experimental results. The MIC and MBC values of compound A were observed to be lower in contrast to fluorescein and ampicillin for all the tested bacterial strains, which were approximately 3‐ to 4‐fold lower than MIC and MBC values of the later. Results obtained from the study clearly indicate that compound A has better antimicrobial and bactericidal activity in comparison to ampicillin and fluorescein. Synthesized compound can be a better substitute of traditionally used antibiotics, Ampicillin.

Highly sensitive, ambient temperature CO sensor using tin oxide based composites

In the present work, we report an excellent gas sensing performance of the unique nanocomposite films prepared with the help of different materials such as semiconductor metal-oxide, polymer and metal for carbon monoxide gas sensing at ambient temperature. The fabrication of SnO2/PANI/Pd nanocomposite film was performed using the hydrothermal route. The fabricated films were characterized with various analytical techniques such as X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM), and Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) etc. Furthermore, DFT results are used to examine the transport and electronic properties of all prepared films. The computing results show that after hybridizing with Pd and SnO2, the response of the fabricated SnO2 and polyaniline (PANI) films to CO gas molecules is considerably improved. At room temperature, sensing characterization of the fabricated sensing films was carried out by using target gas concentrations with varying ppm level of 50–300. At ambient temperature, the SnO2/PANI/Pd film has the maximum sensitivity ~ 400.8% out of all the fabricated films at 0.3% of the target gas. Our findings show that SnO2, SnO2/Pd, PANI, and SnO2/PANI/Pd composite sensing films have a bright future in the gas sensing application with incredibly-higher sensitivity towards CO gas.