Size distributions of aerosols in an indoor environment with engineered nanoparticle synthesis reactors operating under different scenarios

Size distributions of nanoparticles in the vicinity of synthesis reactors will provide guidelines for safe operation and protection of workers. Nanoparticle concentrations and size distributions were measured in a research academic laboratory environment with two different types of gas-phase synthesis reactors under a variety of operating conditions. The variation of total particle number concentration and size distribution at different distances from the reactor, off-design state of the fume hood, powder handling during recovery, and maintenance of reactors are established. Significant increases in number concentration were observed at all the locations during off-design conditions (i.e., failure of the exhaust system). Clearance of nanoparticles from the work environment was longer under off-design conditions (20 min) compared to that under normal hood operating conditions (4–6 min). While lower particle number concentrations are observed during operation of furnace aerosol reactors in comparison to flame aerosol reactors, the handling, processing, and maintenance operations result in elevated concentrations in the work area.     

Studies in [3, 3] Sigmatropic Rearrangement: Regioselective Cyclization of 5-(Cyclohex-2-Enyl)-6-Hydroxy-1-Methylquinolin-2(1H)-One

Thermal [3,3] sigmatropic rearrangement of 6-cyclohex-2-enyloxy-1-methylquinolin-2(1H)-one (3) afforded 5-cyclohex-2-enyl-6-hydroxy-l-methyl-quinolin-2(1H)-one (4) in 86% yield. Compound 4 on treatment with pyridine hydrotribromide in CH₂Cl₂ gave exclusively non-bridged product 6 (85%) whereas compound 4 by a different route viz., acetylation followed by bromine addition and cyclization gave the bicyclic product 7 (80%). Compound 4 also furnished a bicyclic product 11 (80%) on treatment with cone. H₂SO₄.     

An Improved Direct Oxidation of Alkyl Halides to Aldehydes

The oxidation of alkyl chlorides and bromides with dimethyl sulfoxide has been performed in the presence of sodium iodide. This method allows a convenient one-step procedure for the preparation of aldehydes from alkyl chlorides and bromides.     

Atom‐Efficient Gold(I)‐Chloride‐Catalyzed Synthesis of α‐Sulfenylated Carbonyl Compounds from Propargylic Alcohols and Aryl Thiols: Substrate Scope and Experimental and Theoretical Mechanistic Investigation

Gold(I)‐chloride‐catalyzed synthesis of α‐sulfenylated carbonyl compounds from propargylic alcohols and aryl thiols showed a wide substrate scope with respect to both propargylic alcohols and aryl thiols. Primary and secondary aromatic propargylic alcohols generated α‐sulfenylated aldehydes and ketones in 60–97 % yield. Secondary aliphatic propargylic alcohols generated α‐sulfenylated ketones in yields of 47–71 %. Different gold sources and ligand effects were studied, and it was shown that gold(I) chloride gave the highest product yields. Experimental and theoretical studies demonstrated that the reaction proceeds in two separate steps. A sulfenylated allylic alcohol, generated by initial regioselective attack of the aryl thiol on the triple bond of the propargylic alcohol, was isolated, evaluated, and found to be an intermediate in the reaction. Deuterium labeling experiments showed that the protons from the propargylic alcohol and aryl thiol were transferred to the 3‐position, and that the hydride from the alcohol was transferred to the 2‐position of the product. Density functional theory (DFT) calculations showed that the observed regioselectivity of the aryl thiol attack towards the 2‐position of propargylic alcohol was determined by a low‐energy, five‐membered cyclic protodeauration transition state instead of the strained, four‐membered cyclic transition state found for attack at the 3‐position. Experimental data and DFT calculations supported that the second step of the reaction is initiated by protonation of the double bond of the sulfenylated allylic alcohol with a proton donor coordinated to gold(I) chloride. This in turn allows for a 1,2‐hydride shift, generating the final product of the reaction.     

Transport of U(VI) from sulphuric acid medium across supported liquid membrane (SLM) containing di-(2-ethylhexyl) phosphoric acid (D2EHPA)/n-dodecane as a carrier

This paper reports on the supported liquid membrane (SLM) based transport studies of U(VI) from sulphate medium using di-(2-ethylhexyl) phosphoric acid/n-dodecane as carrier. Polytetrafluoroethylene membrane was used as solid support and H₂SO₄ as receiver phase. The effects of various parameters such as receiver phase concentration, feed acidity, carrier concentration, U(VI) concentration, membrane thickness and membrane pore size on U(VI) transport had been investigated. With increase in H₂SO₄ concentrations and pH of feed solution there is an increase in U(VI) transport across the SLM. Similarly with increase in membrane thickness the U(VI) transport decrease whereas in case of pore size variation reverse results are obtained. The membrane thickness variation results showed that the U(VI) transport across the SLM is entirely diffusion controlled and the diffusion coefficient the D _(o) was calculated as 1.36 × 10^?7 cm² s^?1. Based on optimized condition, a scheme had been tested for selective recovery of U(VI) from ore leach solution containing a large number of other metal ions.     

Linear {NiII–LnIII–NiII} Complexes Containing Twisted Planar Ni(μ‐phenolate)2Ln Fragments: Synthesis,Structure, and Magnetothermal Properties

Sequential reaction of a multisite LH₄ ligand {2‐[2‐hydroxy‐3‐(hydroxymethyl)‐5‐methylbenzylideneamino]‐2‐methylpropane‐1,3‐diol} with appropriate lanthanide salts followed by the addition of Ni(NO₃)₂ ? 6 H₂O in a 4:1:2 stoichiometric ratio in the presence of triethylamine afforded four heterobimetallic trinuclear complexes [Ni₂Gd(LH₃)₄] ? 3 NO₃ ? 3 MeOH ? H₂O ? CH₃CN ( 1 ), [Ni₂Tb(LH₃)₄] ? 3 NO₃ ? 3 MeOH ? CH₃CN ( 2 ), [Ni₂Dy(LH₃)₄] ? 3 NO₃ ? 3 MeOH ? H₂O ? CH₃CN ( 3 ), and [Ni₂Ho(LH₃)₄] ? 3 NO₃ ? 3 MeOH ? H₂O ? CH₃CN ( 4 ). Complexes 1 – 4 possess linear trimetallic cores with a central lanthanide ion. Magnetic studies revealed a predominant ferromagnetic interaction between the Ni and Ln centers. Alternating current susceptibility measurements of complex 3 showed a small frequency dependence of the out‐of‐phase signal, χ′′_M , under zero direct current field, but without achieving a net maximum above 2 K. Magnetic studies on 1 revealed that it has a significant magnetocaloric effect.     

Evaluation of novel ZnO–Ag cathode for CO2 electroreduction in solid oxide electrolyser

CO₂ and steam/CO₂ electroreduction to CO and methane in solid oxide electrolytic cells (SOEC) has gained major attention in the past few years. This work evaluates, for the very first time, the performance of two different ZnO–Ag cathodes: one where ZnO nanopowder was mixed with Ag powder for preparing the cathode ink (ZnO_mix–Ag cathode) and the other one where Ag cathode was infiltrated with a zinc nitrate solution (ZnO_inf –Ag cathode). ZnO_mix–Ag cathode had a better distribution of ZnO particles throughout the cathode, resulting in almost double CO generation while electrolysing both dry CO₂ and H₂/CO₂ (4:1 v/v). A maximum overall CO₂ conversion of 48% (in H₂/CO₂) at 1.7 V and 700 °C clearly indicated that as low as 5 wt% zinc loading is capable of CO₂ electroreduction. It was further revealed that for ZnO_inf –Ag cathode, most of CO generation took place through RWGS reaction, but for ZnO_mix–Ag cathode, it was the synergistic effect of both RWGS reaction and CO₂ electrolysis. Although ZnO_inf –Ag cathode produced trace amount of methane at higher voltages, with ZnO_mix–Ag cathode, there was absolutely no methane. This seems to be due to strong electronic interaction between Zn and Ag that might have suppressed the catalytic activity of the cathode towards methanation.

     

Synthesis,characterizations, and electrochemical studies of ZnO/reduced graphene oxide nanohybrids for supercapacitor application

Herein the present article reports the fabrication of ZnO/reduced graphene oxide (ZnG) nanohybrid following a reduction-based process using a non-hazardous material, i.e., ascorbic acid. The morphology, structure, and bonding in the nanohybrid were analyzed using different techniques. Atomic force microscopy and scanning electron microscopy images show spherical particles of ZnO distributed over reduced graphene oxide (rGO). The X-ray diffraction analysis gives calculated values of crystallite size for ZnO as 15.62 nm. The successful incorporation of ZnO nanoparticles into rGO was confirmed using energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses. The electrochemical studies were performed using an electrolyte (0.5 M H₂SO₄). The calculated value of specific capacitance for the nanohybrid was 345 Fg^-1, which was found to be almost double as compared to that of rGO, which is having a value of only 190.5 Fg^-1 at the same scan rate. The nanohybrid also showed excellent capacitance retention after 1,000 cycles.