Kinetically Controlled Synthesis of Highly Emissive Au18SG14 Clusters and Their Phase Transfer: Tips and Tricks.

Glutathione (GSH) protected gold nanoclusters (Au n SG m NCs) have been attractive because of their novel properties such as enhanced luminescence and band gap tunability at their quantum confinement region (below ∼2 nm). Initial synthetic routes of mixed-size clusters and size-based separation techniques had latter evolved toward atomically precise nanoclusters via thermodynamic and kinetic control routes. One such exemplary synthesis taking the advantages of a kinetically controlled approach is producing highly red-emissive Au18SG14 NCs (where SG = thiolate of glutathione), thanks to the slow reduction kinetics provided by the mild reducing agent NaBH3CN. Despite the developments in the direct synthesis of Au18SG14, several meticulous reaction conditions still need to be understood for the highly adaptable synthesis of atomically pure NCs irrespective of the laboratory conditions. Herein, we have systematically studied a series of reaction steps involved in this kinetically controlled approach starting from the role of the antisolvent, formation of precursors to Au-SG thiolates, growth of Au-SG thiolates as a function of aging time, and exploring an optimal reaction temperature to optimize the desired nucleation under slow reduction kinetics. The crucial parameters derived in our studies guide the successful and large-scale production of Au18SG14 at any laboratory condition. Next, we investigated the effect of pH on the NCs to study the stability and the best suitable condition for the phase transfer of Au18SG14 clusters. The commonly implemented method of phase transfer at the basic conditions (pH > 9) is not successful in this case. However, we developed a feasible method for the phase transfer by diluting the aqueous NC solution to enhance the negative charges on the NCs' surface by increasing the degree of dissociation at the carboxylic acid group. It is interesting to note that after the phase transfer, the Au18SG14-TOA NCs in toluene as well as in other organic solvents exhibited enhanced luminescence quantum yields from 9 to 3 times and increased average photoluminescence lifetimes by 1.5-2.5 times, respectively.

Removal of hydrogen sulfide generated during anaerobic treatment of sulfate-laden wastewater using biochar: Evaluation of efficiency and mechanisms.

Removal of hydrogen sulfide (H2S) from biogas was investigated in a biochar column integrated with a bench-scale continuous-stirred tank reactor (CSTR) treating sulfate-laden wastewater. Synthetic wastewater containing sulfate concentrations of 200-2000mg SO42-/L was used as substrate, and the CSTR was operated at an organic loading rate of 1.5g chemical oxygen demand (COD)/L·day and a hydraulic retention time (HRT) of 20days. The biochar was able to remove about 98.0 (±1.2)% of H2S for the ranges of concentrations from 105-1020ppmv, especially at high moisture content (80-85%). Very high H2S adsorption capacity (up to 273.2±1.9mg H2S/g) of biochar is expected to enhance the H2S oxidation into S0 and sulfate. These findings bring a potentially novel application of sulfur-rich biochar as a source of sulfur, an essential but often deficient micro-nutrient in soils.

Chemically modified amino porphyrin/TiO2 for the degradation of Acid Black 1 under day light illumination.

In this paper, for the first time, chemically modified 5,10,15,20-meso-tetra-(para-amino)-phenyl-porphyrin/TiO2 (TPAPP/TiO2) was prepared and used for the degradation of an azo dye Acid Black 1 (AB 1) under direct sunlight. Initially, TiO2 was prepared by sol-gel method. Before making a TPAPP/TiO2 composite, the surface modification of TiO2 was carried out with glycidoxypropyltrimethoxy silane (GPTMS) which acts as a coupling agent. This is an epoxy terminated silane and could easily bond to the amino group of TPAPP through epoxy cleavage. The formation of TPAPP/TiO2 was confirmed by different characterization techniques such as FT-IR, XRD, SEM and DRS. The photocatalytic activity of TiO2 was highly influenced by TPAPP. A mechanism was proposed for AB 1 degradation by TPAPP/TiO2 under sun light.

Mechanisms of Bond Cleavage during Manganese Oxide and UV Degradation of Glyphosate: Results from Phosphate Oxygen Isotopes and Molecular Simulations.

Degradation of glyphosate in the presence of manganese oxide and UV light was analyzed using phosphate oxygen isotope ratios and density function theory (DFT). The preference of C-P or C-N bond cleavage was found to vary with changing glyphosate/manganese oxide ratios, indicating the potential role of sorption-induced conformational changes on the composition of intermediate degradation products. Isotope data confirmed that one oxygen atom derived solely from water was incorporated into the released phosphate during glyphosate degradation, and this might suggest similar nucleophilic substitution at P centers and C-P bond cleavage both in manganese oxide- and UV light-mediated degradation. The DFT results reveal that the C-P bond could be cleaved by water, OH- or •OH, with the energy barrier opposing bond dissociation being lowest in the presence of the radical species, and that C-N bond cleavage is favored by the formation of both nitrogen- and carbon-centered radicals. Overall, these results highlight the factors controlling the dominance of C-P or C-N bond cleavage that determines the composition of intermediate/final products and ultimately the degradation pathway.

5,10,15,20-Tetra-kis(4-acetyl-oxyphen-yl)porphyrin including an unknown solvate.

Mol-ecules of the title compound, C52H38N4O8, are located on an inversion center so that the asymmetric cell contains one half of the mol-ecule. The macrocycle exhibits a ruffled conformation with a maximum deviation of 0.16 Šfor the 24 macrocycle atoms: the dihedral angle between adjacent five-membered rings is 5.13 (19)°. The benzene rings are rotated by 70.25 (19)° with respect to their adjacent protonated five-membered rings, and by 65.56 (19)° with respect to the unprotonated rings. The porphyrin conformation is supported by bifurcated N-H⋯(N,N) hydrogen bonds. The structure contained poorly resolved solvent mol-ecules in voids of volume 217 Å(3) per unit cell. The latter were treated using the SQUEEZE routine in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148-155]. As the solvent could not be identified exactly, it was not included in the calculation of the overall formula weight, density and absorption coefficient.

One-step synthesis and bioassay of N-phosphoramidophosphonates.

A simple one-step synthesis was accomplished for the preparation of N-phosphoramidophosphonates by a direct reaction of phosphoramidate (1) with heterocyclic aldehydes (2a-j) and dialkyl phosphites at 60-70 degrees C in the presence of tetramethylguanidine. The tetramethylguanidine not only catalyses this reaction but also helps to form pure products in high yields in lesser time. They exhibited good insecticidal and antioxidant properties.

Synthesis, anti-bacterial and anti-oxidant properties of thiadiazaphosphol-2-ones.

4-Amino-5-phenyl-4H-1,2,4-triazole-3-thiol (1) underwent facile condensation with various phosphorus dichlorides (2a-j) in the presence of triethylamine in dry tetrahydrofuran at 60-65 degrees C and afforded corresponding thiadiazaphosphol-2-ones (3a-j). Their chemical structures were characterized using IR, (1)H-, (13)C-, (31)P-NMR and Mass spectral studies. All the title compounds were screened for antioxidant properties by radical scavenging methods such as 1,1-diphenyl-2-picryl hydrazyl (DPPH), hydroxyl and lipid peroxidation. They exhibited potent in vitro antioxidant activity dose dependently. Their bioassay showed them to possess significant antibacterial activity.