Electron Density Drift Research Articles

Novel Technology for the Removal of Brilliant Green from Water: Influence of Post-Oxidation, Environmental Conditions, and Capping.

Chemical dyes are used in a wide range of anthropogenic activities and are generally not biodegradable. Hence, sustainable recycling processes are needed to avoid their accumulation in the environment. A one-step synthesis of Fecore–maghemiteshell (Fe–MM) for facile, instantaneous, cost-effective, sustainable, and efficient removal of brilliant green (BG) dye from water has been reported here. The homogenous and monolayer type of adsorption is, to our knowledge, the most efficient, with a maximum uptake capacity of 1000 mg·g–1, for BG on Fe–MM. This adsorbent was shown to be efficient in occurring in time-scales of seconds and to be readily recyclable (ca. 91%). As iron/iron oxide possesses magnetic behavior, a strong magnet could be used to separate Fe–MM coated with BG. Thus, the recycling process required a minimum amount of energy. Capping Fe–MM by hydrophilic clay minerals further enhanced the BG uptake capacity, by reducing unwanted aggregation. Interestingly, capping the adsorbent by hydrophobic plastic (low-density polyethylene) had a completely inverse effect on clay minerals. BG removal using this method is found to be quite selective among the five common industrial dyes tested in this study. To shed light on the life cycle analysis of the composite in the environment, the influence of selected physicochemical factors (T, pH, hν, O3, and NO2) was examined, along with four types of water samples (melted snow, rain, river, and tap water). To evaluate the potential limitations of this technique, because of likely competitive reactions with metal ion contaminants in aquatic systems, additional experiments with 13 metal ions were performed. To decipher the adsorption mechanism, we deployed four reducing agents (NaBH4, hydrazine, LiAlH4, and polyphenols in green tea) and NaBH4, exclusively, favored the generation of an efficient adsorbent via aerial oxidation. The drift of electron density from electron-rich Fecore to maghemite shells was attributed to be responsible for the electrostatic adsorption of N+ in BG toward Fe–MM. This technology is deemed to be environmentally sustainable in environmental remediation, namely, in waste management protocol.

Multiscale modeling and run-to-run control of PECVD of thin film solar cells

In this work, we focus on the development of a multiscale modeling and run-to-run control framework with the purpose of improving thin film product quality in a batch-to-batch plasma-enhanced chemical vapor deposition (PECVD) manufacturing process. Specifically, at the macroscopic scale, gas-phase reaction and transport phenomena yield deposition rate profiles across the wafer surface which are then provided to the microscopic domain simulator in which the complex microscopic surface interactions that lead to film growth are described using a hybrid kinetic Monte Carlo algorithm. Batch-to-batch variability has prompted the development of an additional simulation layer in which an exponentially weighted moving average (EWMA) control algorithm operates between serial batch deposition sequences to adjust the operating temperature of the PECVD reactor to overcome drift in the electron density of the plasma. Application of the run-to-run (R2R) control system developed here is shown to reduce offset in the product thickness from 5% to less than 1% within 10 batches of reactor operation. Finally, we propose an extension of the EWMA algorithm to four independent, radial wafer zones in order to improve thickness uniformity in the presence of spatially non-uniform species concentrations. It is demonstrated that the produced thin films can be driven to the desired thickness set-point of 300 nm in less than 10 batches in the presence of both electron density drift and non-uniform deposition rate profiles.

Synthesis and Characterization of Homoleptic and Heteroleptic Complexes Involving Dithiocarbamates, Triphenylphosphine, and Nickel(II)

Six new nickel complexes of two dithiocarbamate ligands (cyfdtc = N-cyclohexyl-N- furfuryldithiocarbamate and bztpedtc = N-benzyl-N-[2-thiophenylethyl]dithiocarbamate) namely, (Ni[cyfdtc]2) (1), (Ni[bztpedtc]2) (2), (Ni[cyfdtc][NCS][PPh3]) (3), (Ni[bztpedtc] [NCS][PPh3]) (4), (Ni[cyfdtc][PPh3]2)ClO4 (5), and (Ni[bztpedtc][PPh3]2)ClO4 (6) have been prepared and characterized using IR, electronic, and NMR (1H and 13C) spectra. A single crystal X-ray structural analysis was carried out for complex 3 and showed that nickel is in a distorted square planar arrangement with the NiS2PN chromophore. The shift in νC˭N of the heteroleptic complexes to higher frequencies compared with the parent complex is assigned to mesomeric delocalization of electron density from the dithiocarbamate ligand toward the metal atom, which increases the contribution of polar thioureide form in mixed ligand complexes. Electronic spectral studies suggest square planar geometry for the complexes. In the 13C NMR spectra, the upfield shift of NCS2 carbon signal for 3 and 4 from the chemical shift value of 1 and 2 is due to effect of PPh3 on the mesomeric drift of electron density toward nickel throughout thioureide C˭N bond.

Synthesis of Highly Fluorescent Silver Clusters on Gold(I) Surface

Evolution of fluorescence from a giant core-shell particle is new and synergistic, which requires both gold and silver ions in an appropriate ratio in glutathione (GSH) solution. The formation of highly fluorescent Ag(2)/Ag(3) clusters on the surface of Au(I) assembly results in giant Au(I)(core)-Ag(0)(shell) water-soluble microparticles (~500 nm). Here, Au(I) acts as the template for the generation of fluorescent Ag clusters. The presence of gold under the synthetic strategy is selective, and no other metal supports such synergistic evolution. The core-shell particle exhibits stable and static emission (emission maximum, 565 nm; quantum yield, 4.6%; and stroke shift, 179 nm) with an average lifetime of ~25 ns. The drift of electron density by the Au(I) core presumably enhances the fluorescence. The positively charged core offers unprecedented long-term stability to the microparticles in aqueous GSH solution.

Synthesis, spectral and antibacterial studies on Ni(II) and Zn(II) complexes involving N-furfuryl-N-isopropyldithiocarbamate (f iprdtc) and Lewis bases: X-ray structure of [Ni(f iprdtc)(NCS)(PPh3)

[Ni(fiprdtc)2] (1), [Ni(fiprdtc)(PPh3)(NCS)] (2), [Ni(fiprdtc)(PPh3)2]ClO4 (3), [Zn(fiprdtc)2] (4), [Zn(fiprdtc)2(1,10-phen)] (5) and [Zn(fiprdtc)2(2,2′-bipy)] (6) (f iprdtc=N-furfuryl-N-isopropyldithio- carbamate, 1,10-phen=1,10-phenanthroline and 2,2′-bipy=2,2′-bipyridine) complexes were prepared and characterized by elemental analysis, electronic, IR and NMR spectra and the structure of 2 was determined by single-crystal X-ray crystallography. UV–Vis spectral data of 1–3 are consistent with the formation of square planar complexes. IR spectra of the complexes show the contribution of the thioureide form to the structure. A single-crystal X-ray structural analysis of 2 proved four-coordinated nickel in a distorted square planar arrangement with a S2PN donor set. Significant asymmetry in Ni–S bond distances was observed in [Ni‒ S1=2.1655(8); Ni‒ S2=2.2120(8) Å]. This observation clearly supports the less effective trans of SCN− over PPh3. The observed shielding in N13CS2 chemical shifts of heteroleptic nickel complexes 2 and 3 when compared with homoleptic nickel complex 1 indicates the effect of PPh3 on the mesomeric drift of electron density toward nickel through the thioureide C‒ N bond. The N13CS2 chemical shift of 5 and 6 are additionally deshielded compared with 4 owing to the increase in coordination number. Complexes were screened for in vitro antibacterial activity and significant activity has been found.

Structural variations of nickel complexes in NiS4 and NiS2PN coordination environments: spectral and single-crystal X-ray structural studies on bis(4-methylpiperidinecarbodithioato-S,S′)nickel(II) and (4-methylpiperidinecarbodithioato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II)

Abstract[Ni(4-mpipdtc) 2 ] and [Ni(4-mpipdtc)(PPh 3 )(NCS)] (4-mpipdtc = 4-methylpiperidinecarbodithioate anion) have been characterized by electronic, IR, and NMR spectroscopy, single crystal X-ray analysis, and cyclic voltammetry. IR spectra of the complexes show the contribution of the thioureide form to the structures. 1 H NMR spectra show the deshielding of α-CH 2 protons on complexation. 13 C NMR spectra shows interesting differences between the N 13 CS 2 carbon signals of the parent complex [Ni(4-mpipdtc) 2 ] and the mixed ligand complex [Ni(4-mpipdtc)(PPh 3 )(NCS)]. The N 13 CS 2 carbon signal for [Ni(4-mpipdtc)(PPh 3 )(NCS)] is observed at 204.85 ppm with an upfield shift of about 3.8 ppm compared with that found in [Ni(4-mpipdtc) 2 ] (201.06 ppm). The observed shielding in [Ni(4-mpipdtc)(PPh 3 )(NCS)] indicates the effect of PPh 3 on the mesomeric drift of electron density toward nickel through the thioureide C-N bond. Single crystal X-ray analysis of [Ni(4-mpipdtc) 2 ] and [Ni(4-mpipdtc)(PPh 3 )(NCS)] confirms the presence of four-coordinated nickel in a distorted square-planar arrangement with the NiS 4 and NiS 2 PN chromophores, respectively. The C-N (thioureide) bond lengths of [Ni(4-mpipdtc)(PPh 3 )(NCS)] are shorter than those found in [Ni(4-mpipdtc) 2 ], because of the presence of the π-acid (triphenylphosphine) in [Ni(4-mpipdtc)(PPh 3 )(NCS)]. Significant asymmetry in Ni-S bond distances was observed in Ni(4-mpipdtc)(PPh 3 )(NCS)] (2.162(2) and 2.211(2) A). This observation clearly supports the less effective trans effect of SCN - over PPh 3 . The piperidine ring in the dithiocarbamate fragment is in the normal chair conformation.Graphical Abstract[IMAGE]

Trans influences of Cl−, NCO− and NCS− donors on planar NiS2PN(CO), NiS2PN(CS), NiS2PCl and NiS2P2 chromophores: synthesis, NMR spectral and single crystal X-ray structural studies

Planar [Ni(bedtc)(PPh3)Cl] (1), [Ni(bedtc)(PPh3)(NCO)] (2), [Ni(bedtc)(PPh3)(NCS)] (3), [Ni(bedtc)(PPh3)(CN)] (4) and [Ni(bedtc)(dppe)]ClO4 (5) (where bedtc = N-benzyl-N-(2-hydroxyethyl)dithiocarbamate anion, PPh3 = triphenylphosphine and dppe = 1,2-bis((diphenylphosphino)ethane)) were prepared from [Ni(bedtc)2]. Complexes 1–5 were characterized by elemental analysis, electronic, IR and NMR (1H, 13C, and 31P) spectra. Electronic spectra of the complexes show bands corresponding to dz 2 → dxy/dx 2 − y 2 transitions. The complexes were diamagnetic. IR and 13C NMR studies indicate the mesomeric flow of π-electron density from the dithiocarbamate towards the nickel. In 1H NMR, α-CH2–and β-CH2–protons of–CH2–CH2–OH were equally deshielded. The deshielding for the coordinated phosphorus signals in 31P NMR spectra for all the cases compared with the free phosphine clearly manifests the drift of electron density from the phosphorus toward the metal on complexation. Single crystal X-ray structures of 1–3 indicate that nickel is in a planar environment with short >S2C–N bond distances. In 2, a rare mode of coordination between nickel and cyanate (NCO−) through the nitrogen is observed. Significant asymmetry in Ni–S bond distances were observed for 1–3 clearly supporting the trans influences of Cl−, NCO− and NCS−, respectively, over PPh3.