Ag2O@UiO-66 new thin film as p-n heterojunction: permanent photoreduction of hexavalent Cr.

The new nanosphere Ag2O@UiO-66 thin-film was synthesized on a stainless steel mesh surface via an electrophoretic deposition method, and is used as an effective and low-cost photocatalyst using visible light. The synthesized nanocomposite was used to perform photo-reduction of Cr(vi) ions under white light irradiation. The best removal rate (72% after 15 minutes) was obtained by the film with 0.034 grams of deposited composite having relative percentages of Ag2O : UiO-66 of 70 : 30. The interesting obtained results confirm that the p-n heterojunction of the composite is the main cause of the desired charge separation and the photoreduction speed increase. In the following, the resulting compounds were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmittance electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy diffraction X-ray spectroscopy (EDAX) and the Brunauer, Emmett, and Teller (BET) method. Scavenging studies performed in the presence of familiar scavengers confirmed that superoxide radicals (˙O2-) and dissolved oxygen gas have a significant role in the photocatalytic reduction process.

An accurate DFT study within conformational survey of the D-form serine-alanine protected dipeptide.

The conformational analysis of N-formyl-D-serine-D-alanine-NH2 dipeptide was studied using density functional theory methods at B3LYP, B3LYP‒D3, and M06‒2X levels using 6‒311 + G (d,p) basis set in the gas and water phases. 87 conformers of 243 stable ones were located and the rest of them were migrated to the more stable geometries. Migration pattern suggests the more stable dipeptide model bears serine in ßL, γD, γL and the alanine in γL and Î³D configurations. The investigation of side‒chain‒backbone interactions revealed that the most stable conformer, γD-γL, is in the ß‒turn region of Ramachandran map; therefore, serine-alanine dipeptide model should be adopted with a ß‒turn conformation. Intramolecular hydrogen bonding in ß‒turns consideration by QTAIM disclosed γD-γL includes three hydrogen bonds. The computed UV‒Vis spectrum alongside of NBO calculation showed the five main electronic transition bands derived of n → n* of intra‒ligand alanine moiety of dipeptide structure.

A novel γ‒BMO@BMWO Z‒Scheme heterojunction for promotion photocatalytic performance: Nanofibers thin film by Co‒axial‒electrospun.

Bismuth molybdate has three phases α-Bi2MoO6, ß-Bi2Mo2O9, and γ- Bi2Mo3O12, each of which has unique properties that distinguish them from each other. Among them, Bi2MoO6 and Bi2Mo3O12 have the most stability. In this research, γ-Bi2MoO6@Bi2Mo2.66W0.34O12 core‒shell nanofibers were deposited on the stainless steel mesh as effective and low‒cost substrate. The co‒axial electrospinning as a simple method was applied to form nanofibers on the substrate. Both of the abovementioned bismuth molybdates contents include different crystal facets, controlling the Red‒Ox properties. α-Bi2MoO6 possesses the vast numbers of oxygen vacancies in Mo-O bonding makes the oxidant {100} crystal facet. Likewise, γ‒Bi2Mo2.66W0.34O12 contains brittle facet of {010} with high concentration of Oxygen vacancies resulted in oxidative capability of the core‒shell composite. The obtained data indicated the key role of OH radical through photocatalytic reactions and a new heterojunction having direct Z‒scheme standing.

New highly efficient 2D/1D HAp/g‒C3N4 photocatalyst thin film insight into crystal orientation and C‒vacancy effects.

The novel synthetic Sol‒EPD process of a thin film including of well decorated g‒C3N4 nanotubes on plate‒like hydroxyapatite (HAp) were applied. Using Sol‒EPD designable method anisotropic growth of HAp nanocrystals on the substrate were achieved. It has provided the orientation of the different crystal facets resulted in the photogenerated O‒vacancy from phosphate groups. Based on the studied XRD pattern, EPD deposited film of HAp was oriented along c‒plane that can improve the photocatalytic activity of the designed composited film. Systematic designing was applied for decoration of g‒C3N4 nanotubes on the HAp under thermal condensation of melamine coincide with calcination of HAp. This new designed HAp/g‒C3N4 nanofilm was shown high photocatalytic efficiency and completely degradation of persistent pollutant of 4‒nitrophenol in the aqueous solution. According to the electrochemical impedance spectroscopy and current density studies, the higher charge separation/low charge recombination results were obtained for composited g‒C3N4/HAp nano‒film comparing with the single films of HAp and urchin like g‒C3N4. This high separation of charge pairs should be also assigned to the special designed morphology. In addition, wrapped like structure of g‒C3N4 nanotubes with C‒vacancy around HAp nanoplates play key role in separation of photo‒induced charge pairs, light diffusion, and high light harvesting within hollow nanotube. It can be highlighted that the composite degraded more than 95% of 4‒nitrophenol during 90 min that after 5 runs the photocatalytic activity was not significantly changed.

Dendritic structured palladium complexes: magnetically retrievable, highly efficient heterogeneous nanocatalyst for Suzuki and Heck cross-coupling reactions.

The recyclable nanomagnetic Pd-complex PAMAM G0-Pd@γ-Fe2O3 is reported for catalytic C-C cross-coupling reactions of challenging substrates. Mainly, a great variety of aryl chlorides can be used as substrates for Suzuki-Miyaura and Mizoroki-Heck reactions under mild reaction conditions (60-90 °C) and low catalyst loading (<1 mol% Pd) in aqueous media. The presence of numerous polar groups in the polymer matrix increases the solubility of the catalyst in water, thus facilitating its operation in aqueous environments. The immobilization of the catalyst on the surface of a magnetic platform allows its effective recovery and reuse without significant loss of catalytic activity for at least six cycles with total leaching of <1% palladium metal, meeting the requirements for acceptable metal residues in the pharmaceutical industry.

Correction to New Task-Specific and Reusable ZIF-like Grafted H6P2W18O62 Catalyst for the Effective Esterification of Free Fatty Acids.

[This corrects the article DOI: 10.1021/acsomega.0c00358.].

In situ synthesis of holey g-C3N4 nanosheets decorated by hydroxyapatite nanospheres as efficient visible light photocatalyst.

The interesting g-C3N4 nanosheet morphology has drawn huge attention in photocatalytic applications because of its special features. Nonetheless, the relative activity of these nanosheets is still controversial due to the low available active sites and the high recombination probability of photo-induced charge carriers. In this work, in situ sol-gel approach was applied to synthesize holey g-C3N4 nanosheets/hydroxyapatite (HAp) nanospheres with plentiful in-plane holes. Herein, the presence of Ca2+ plays a key role in the formation of holey defects on 2D g-C3N4. In-plane holes provide nanosheets with more active edges and diffusion channelsv, resulting in a tremendous enhanced mass and photo-induced charge transfer speed. Moreover, the holes make highly numbered boundaries, which lead to the prevention of aggregation. On the other hand, distributed nano-HAp spheres on these nanosheets can form effective heterojunctions having high photo-degradation ability of pollutants. Intrinsic O-vacancies inside HAp unit cells mainly affect the capture of photogenerated electrons, pollutant molecules, and O2 gas. The synergistic presence of O-vacancies and holey defects (C-vacancies) on 2D g-C3N4 plays a key role in raising the photocatalytic performance of holey g-C3N4/HAp. It can be concluded that the proposed preparation method is a promising approach for simultaneous synthesis of holey g-C3N4 and surface heterojunctions of Ca-based materials. This new structure has shown significant degradation ability of bisphenol A, a prominent pollutant, with a low amount (0.01 g) and short time.

Crystal and molecular structure of [Ni{2-H2NC(=O)C5H4N}2(H2O)2][Ni{2,6-(O2C)2C5H3N}2]·4.67H2O; DFT studies on hydrogen bonding energies in the crystal.

[Ni{2-H2NC(=O)C5H4N}2(H2O)2][Ni{2,6-(O2C)2C5H3N}2]·4.67H2O, a new complex salt containing a bis(2,6-dicarboxypyridine)nickel(II) anion and a bis(2-amidopyridine)diaquanickel(II) cation, was synthesized and characterized. The crystal is stabilized by an extensive network of hydrogen bonds. Alternate layers of anions and cations/water molecules parallel to (010) can be distinguished. Computational studies of the network packing of the title compound by high-level DFT-D/B3LYP calculations indicate stabilization of the networks with conventional and non-conventional intermolecular O-H...O, N-H...O and C-H...O hydrogen bonds along with π-stacking contacts. Due to the presence of water molecules and the importance of forming hydrogen bonds with the involvement of water clusters to the stability of the crystal packing, the importance and role of these water clusters, and the quantitative stability resulting from the formation of hydrogen bonds and possibly other noncovalent bonds such as π-stacking are examined. The binding energies obtained by DFT-D calculations for these contacts indicate that hydrogen bonds, especially O-H...O and N-H...O, control the construction of the crystalline packing. Additionally, the results of Bader's theory of AIM for these interactions agree reasonably well with the calculated energies.

Functionalized magnetic PAMAM dendrimer as an efficient nanocatalyst for a new synthetic strategy of xanthene pigments.

A green protocol has been developed for preparation of the wide variety of colored xanthene derivatives using a new efficient magnetic solid acid catalyst bearing polyamidoamine dendrimer moiety as a nanoscopic compound. Dendrimers, highly symmetric molecules around a core and 3D spherical morphology, show interesting traits based on their functionalized groups on the branched surface. They can be designed to provide water soluble structures or pseudo-active sites of biomolecules. The catalyst was assembled via a polyamidoamine dendrimer immobilized on the surface of γ-Fe2O3 followed by the sulfonylation of the amine groups by chlorosulfonic acid resulting in γ-Fe2O3@PAMAM-SO3H. Herein, PAMAM dendrimer with repeating amine/amide branches as catchable sites of sulfonic acid groups was introduced as transformer of homogeneous to heterogeneous acidic catalysts. The physicochemical properties of synthesized catalyst were studied using by FT-IR, FE-SEM, XRD, VSM, EDS, TGA/DTG, and TEM. Finally, the catalytic activity of γ-Fe2O3@PAMAM-SO3H was evaluated for the preparation of xanthene derivatives via a one-pot, three components reaction of aromatic aldehydes with i) ß-naphthol, ii) cyclic 1,3-dicarbonyl, iii) ß-naphthol and cyclic 1,3-dicarbonyl compounds, iv) 2-hydroxy-1,4-naphthoquinone, leading to the eco-riendly preparation of the target compounds in good to excellent yields. The catalyst could be easily recycled for at least five consecutive runs without significant loss in its catalytic activity.

New Task-Specific and Reusable ZIF-like Grafted H6P2W18O62 Catalyst for the Effective Esterification of Free Fatty Acids.

The catalytic esterification of free fatty acids is an important reaction pathway for chemical synthesis and biodiesel production, wherein efficient heterogeneous catalysts are sought to replace mineral acids. Herein, the esterification of oleic acid together with some familiar fatty acids is demonstrated with methanol over a heterogeneous heteropolyacid-functionalized zeolite imidazolate framework [H6-n P2W18O62 n-/ZIF(H n His.)+n ]. This new heterogeneous catalyst (named as HPA/ZIF(His.) throughout the text) with an average particle size of 80 nm was prepared via condensation of histamine with zinc chloride and characterized by means of Fourier transform infrared (FT-IR), X-ray diffraction (XRD), UV-vis, energy-dispersive X-ray spectrometry, Brunauer-Emmett-Teller, thermogravimetric analysis (TGA), inductively coupled plasma - optical emission spectrometry (ICP-OES), and scanning electron microscopy. According to the performed characterizations, an HPA loading of 40.5 wt % is obtained for HPA/ZIF(His.) from ICP-OES analysis. Moreover, a typical type-IV isotherm with similar adsorption-desorption properties as seen for ZIF-8 is attained. In addition, TGA measurement confirms less stability of HPA/ZIF(His.) compared to that of pure ZIF(His.). The catalytic performance of the nanomaterial is evaluated with respect to temperature, catalyst loading, and methanol/oleic acid ratio and leads to a high yield of methyl ester (>90%) under reflux for 4 h. The preliminary kinetic studies confirm a pseudo-first-order kinetic model for the esterification of oleic acid. To explore the scope of the HPA/ZIF(His.) catalyst in methyl ester production, other free fatty acids with various chain lengths are also successfully tested. Although the nanocatalyst loses a part of its activity during reuse, however, it is stable over at least four recycles as confirmed by XRD and FT-IR. Eventually, the response surface methodology (RSM) is used as a statistical modeling approach to get the best-optimized reaction conditions compared to the performed single-variable benchmarking experiments. Therefore, the central composite design (CCD) and RSM attained a platform to determine the relationship among the reaction time, acid/methanol molar ratio, and catalyst dosage.

A reconnaissance DFT study of the full conformational analysis of N-formyl-L-serine-L-alanine-NH2 dipeptide.

Theoretical conformational analysis of N-formyl-L-serine-L-alanine-NH2 dipeptide model was investigated using B3LYP/6-311+G(d,p) and M06-2X/6-311+G(d,p) calculations. In this research, 243 total possible conformations of the dipeptide model were optimized including 87 stable conformers and the other disappeared ones migrated to more stable geometries. Migration pattern suggests more stability of the dipeptide model with the serine (ser) in ßL, γL, and γD and the alanine (ala) in γD and γL configurations, along with 26 of the found conformers having ß-turn structures. Our calculations reveal that the most stable conformer, γL+γD, is in ß-turn region of Ramachandran map; therefore, serine-alanine (ser-ala) dipeptide model should be adopted with a ß-turn conformation. The atoms in molecules (AIM) topological analysis was carried out to characterize the nature of the intramolecular hydrogen bonding in ß-turn structures. The γL+γD, including three hydrogen bonds, has the highest stability, while αLaγL as the most unstable ß-turn conformer bears two and one hydrogen bonds at the B3LYP/6-311+G(d,p) and M06-2X/6-311+G(d,p) levels of theory, respectively. Graphical abstract.

New water based EPD thin BiVO4 film: Effective photocatalytic degradation of Amoxicillin antibiotic.

New thin BiVO4 film using facile water‒based electrophoretic deposition process was synthesized on the webbed stainless steel surface. This work can be considered as a green method owing to use of safe, non-flammable, and cheap media of water as solvent of electrophoretic deposition. Structural and morphological properties of the resultant film were studied by X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), Elemental and Mapping analyses (EDS), Optical Microscopy, Atomic Force Microscopy (AFM), and X-ray Photoelectron Spectroscopy (XPS) analysis. The moderate diameter size of nanorods of the deposited BiVO4 was measured in the range of 100 to 150 nm. The prepared three layered thin film was shown permanent photocatalytic degradation rate of Amoxicillin pharmaceutical pollution as high as 97.45 % after 90 min. It can be suggested that BiVO4 nanorods have the high ability of hole-electron separation and electron transferring through the alternative routes. Indeed, the prepared thin films of BiVO4 having nanoroad morphology possess great potential for light harvesting. Moreover, webbed stainless steel with electron acceptor character leads to severe separation of photogenerated hole‒electron. The mechanistic study of the scavenging reaction introduced the hydroxyl radicals as the main specie in the photocatalytic process. It is interesting that obtained results of photocatalytic process of this BVO film within different pollutants (dyes, phenol, and drugs) demonstrated the high efficiency and mineralization rate.

Novel method of square wave voltammetry for deposition of Bi2S3 thin film: Photocatalytic reduction of hexavalent Cr in single and binary mixtures.

In this work a new method of square‒wave voltammetry was performed for electrodepositing of Bi2S3 film on the stainless steel mesh surface as low-cost and effective substrate in visible light harvesting. First, the obtained porous film was characterized by X‒ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), and Raman analysis. In following, photocatalytic activity of film for reduction of hexavalent Cr was evaluated under sunlight irradiation. Results suggested that the presence of voids having several nanometers to 2 µm diameters on the film surface plays key role in photocatalytic processes. Indeed, surface voids as trapping cites and producing routs leads to multiple scattering of visible light. It can be noted that morphology of thin film, substrate structure, and diameters of voids are the main parameters to achieving the high reduction efficiency. Cr(VI) was completely reduced within 100  min under sunlight irradiation. Photoreduction mechanistic studies induced by Bi2S3 film suggested that active oxygen species such as HOO• and O2 have significant role in photocatalytic reaction. Finally, the evaluation of simultaneous photocatalytic process of binary mixture (Cr(VI) and Rhodamin B) was shown synergistic improvement of Cr(VI) and Rhodamin B degradation due to rapid surface reactions.

Synthesis of nano-hydroxyapatite sorbent for microextraction in packed syringe of phthalate esters in water samples.

An easy alkoxide-based sol-gel method using Ca(NO3)2·4H2O and tri-ethyl phosphate (PO(OC2H5)3; TEP) precursors employed to synthesize nano-hydroxyapatite (HAP). The structural characterization of samples was studied using XRD, TEM and elemental analysis of SEM. Scherrer and Williamson-Hall equations were applied to measurement of the crystallite size distributions and micro-strain of the synthesized HAP powder. The synthesized HAP nanoparticles were applied as an efficient sorbent for the microextraction in packed syringe (MEPS) of phthalate esters (PAEs) from water samples. Separation and determination of the PAEs were performed by gas chromatography-flame ionization detection (GC-FID). Several variables affecting the extraction efficiency of the analytes i.e., desorption solvent, volume of desorption solvent and number of extraction cycles were investigated and optimized. Under optimized conditions, the calibration curves were linear (R > 0.9916) in the concentration range of 0.05-100 ng mL-1. The method displays detection limits (at an S/N ration of 3) in the range from 0.02 to 0.1 ng mL-1, and the limits of quantification (at an S/N ratio of 10) are between 0.07 and 0.25 ng mL-1. Relative standard deviations (RSDs) for intra- and inter-day precision are 4.8-8.3%, and 6.1-8.5%, respectively. The applicability of the developed method was examined by analyzing different water samples (river water, bottled mineral water and tap water) and the relative recovery values for the spiked water samples were found to be in the range of 85.5-99.2%.

Investigation of simple and water assisted tautomerism in a derivative of 1,3,4-oxadiazole: a DFT study.

Investigation of tautomerism and transition states in a derivative of 1,3,4-oxadiazole (A, B, C and D) in the gas phase and in solution and in a micro hydrated environment with 1-3 water molecules was performed by calculations at the DFT-B3LYP/6-311++G(d,p) level of theory. The solvent effect is taken into account via the self-consistent reaction field (SCRF) method. The geometries of four possible tautomers of 5-amino-1,3,4-oxadiazole-2(3H)-one were optimized in the gas phase and solution with polarized continuum model (PCM). It was found that in the gas phase and different solvents, A and C tautomers are the most stable and unstable forms, respectively. The results show that the tautomeric interconversion C to D has the lowest Gibbs free energy changes and so the highest equilibrium constant in the gas phase and solution. The equilibrium and rate constants of intermolecular tautomerism in the absence and presence of 1-3 molecules of water were also calculated. The calculated results show that the presence of water molecules considerably reduces the barrier energy of the various reactions. Therefore, this water-assisted tautomerism can be performed fast, especially, with the assistance of two molecules of water.