Reducing Reagent Research Articles

Scalable Synthesis of Bilayer Graphene at Ambient Temperature.

In this work, we develop for the first time a facile chemical lithiation-assisted exfoliation approach to the controllable and scalable preparation of bilayer graphene. Biphenyl lithium (Bp-Li), a strong reducing reagent, is selected to realize the spontaneous Li-intercalation into graphite at ambient temperature, forming lithium graphite intercalation compounds (Li-GICs). The potential of Bp-Li (0.11 V vs Li/Li+), which is just lower than the potential of stage-2 lithium intercalation (0.125 V), enables the precise lithiation of graphite to stage-2 Li-GICs (LiC12). Intriguingly, the exfoliation of LiC12 leads to the bilayer-favored production of graphene, giving a high selectivity of 78%. Furthermore, the mild intercalation-exfoliation procedure yields high-quality graphene with negligible structural deterioration. The obtained graphene exhibits ultralow defect density (ID/IG ∼ 0.14) and a considerably high C/O ratio (∼29.7), superior to most current state-of-the-art techniques. This simple and scalable strategy promotes the understanding of chemical Li-intercalation methods for preparing high-quality graphene and shows great potential for layer-controlled engineering.

One-pot heat-up synthesis of short-wavelength infrared, colloidal InAs quantum dots.

III-V colloidal quantum dots (QDs) promise Pb and Hg-free QD compositions with which to build short-wavelength infrared (SWIR) optoelectronic devices. However, their synthesis is limited by the availability of group-V precursors with controllable reactivities to prepare monodisperse, SWIR-absorbing III-V QDs. Here, we report a one-pot heat-up method to synthesize ∼8nm edge length (∼6.5nm in height) tetrahedral, SWIR-absorbing InAs QDs by increasing the [In3+]:[As3+] ratio introduced using commercially available InCl3 and AsCl3 precursors and by decreasing the concentration and optimizing the volume of the reducing reagent superhydride to control the concentration of In(0) and As(0) intermediates through QD nucleation and growth. InAs QDs are treated with NOBF4, and their deposited films are exchanged with Na2S to yield n-type InAs QD films. We realize the only colloidal InAs QD photoconductors with responsivity at the technologically important wavelength of 1.55μm.

A Facile and Green Approach for the Preparation of Amine-Functionalized Poly(ethylene glycol) by Reducing Poly(ethylene glycol) Azide with Dithiothreitol.

A facile and green approach for the preparation of PEGn-NH2s from PEGn-N3s in water with DTT as the reduction reagent has been developed, avoiding the introduction of metal ions and difficulties in purification compared to the traditional synthesis process of PEGn-NH2s. A series of high-purity linear and multiarm PEGn-NH2s with different molecular weights were synthesized, demonstrating the versatility of this method. Additionally, HS-PEG45-NH2 with high fidelity of thiol and amine was easily prepared through the one-step two functional group conversion of N3-PEG45-S-S-PEG45-N3, and the PEG-based NH2-PEG@AuNPs were also prepared. This technology will promote the application of PEGn-NH2s in the fields of medicine and biomaterials.

Palladium-Catalyzed Reductive Heck Hydroarylation of Unactivated Alkenes Using Hydrosilane at Room Temperature.

The reductive Heck hydroarylation of unactivated alkenes has emerged as an essential reaction for regioselective hydroarylation. Herein, we report a palladium-catalyzed reductive Heck hydroarylation of unactivated alkenes under mild conditions with enhanced functional group tolerance using hydrosilane as the reducing reagent. Under the optimal conditions, the alkylarene yields increased, resulting in minimal undesired products. Mechanistic studies using deuterated reagents indicated the involvement of two competing catalytic cycles.

Highly efficient iron-catalyzed conjugate reduction of α,β-unsaturated ketones with polymethylhydrosiloxane.

An iron-catalyzed ligand free conjugate reduction of α,β-unsaturated ketones with PMHS (polymethylhydrosiloxane) was reported to deliver the corresponding carbonyl compounds with up to 93% yield. This operationally simple protocol shows a broad substrate scope using readily available PMHS as a cost-effective and easy-to-handle reductive reagent.

A rapid and convenient sample treatment method based on the dissolvable polyacrylamide gel for S-acylation proteomics.

Protein S-acylation is an important lipid modification and plays a series of biological functions. As a classic proteomic method for S-acylated proteome analysis, the acyl-biotin exchange and its derivative methods are known to be very labour-intensive and time-consuming all the time, and will result in significant sample loss. Multiple methanol-chloroform precipitations are involved in order to remove the substances that would interfere with enrichment and identification including detergents, the residual reduction and alkylation reagents. Here, we developed a rapid and convenient method for S-acylation proteomics by combining a dissolvable tube gel and the classic ABE method, a Dissolvable Gel based One-Tube sample Treatment method (DGOTT) method. The protein fixation rate, impact of the gel size on analysis performance and feasibility for analyzing complex samples were evaluated. This method enabled the alkylation and chemical substitution reactions to be conducted in a single EP tube, and convenient removal of interferents through gel washing, which could obviously simplify operations and shorten the sample treatment duration. Finally, we identified a total of 1625 potential S-acylated proteins from 800 μg of mouse brain cerebral cortex proteins. We believe that our method could offer potential for high-throughput analysis of protein S-acylation.

Intramolecular Cobalt/Visible Light Cocatalyzed Reductive Coupling of Unactivated Arenes with Unactivated Alkenes.

A protocol for the intramolecular reductive coupling of unactivated arenes with unactivated alkenes has been developed with the aid of a cooperative visible light/cobalt catalytic system. This coupling is achieved via radical cascade cyclization using amines as terminal reducing reagents and water as the main hydrogen source. In their form, readily available N-allyl benzamides are converted to the corresponding spiro cyclohexadiene-lactam or β-phenethylamine analogues in moderate to excellent yields.

Chemical characterization, antioxidant and anti-esophageal cancer properties of Au NPs over sodium lignosulfonate formulated by Cydonia oblonga

This study reports an eco-friendly procedure for the formulated Au NPs decorated over sodium lignosulfonate (NaLS) by using Cydonia oblonga extract. The NaLS acted as a stabilizing and capping agent and the Cydonia oblonga extract was used as a reducing reagent for converting the capped gold ions to gold nanoparticles in the polymeric matrix. Physicochemical characteristics of the prepared Au NPs@NaLS nanocomposite were analyzed by FT-IR, EDX, FE-SEM, elemental mapping, ICP-OES and TEM. The particles are mostly spherical with nano-size (10–20 nm). In the current study, the potentials of Au NPs@NaLS nanocomposite on esophageal carcinoma cells were evaluated. ESO26, FLO-1, KYSE-270, and OE33 cancer cells to check the anti-esophageal carcinoma potentials of Au NPs@NaLS nanocomposite. DPPH test results indicated removing 50 % radicals by nanoparticles and BHT in the doses of 161 and 53 μg/ml. MTT results showed that IC50 = 181, 130, 205, and 133 µg/ml of NPs against FLO-1, ESO26, OE33, and KYSE-270 esophageal carcinoma cells. The results indicated that Au NPs@NaLS nanocomposite prevented esophageal carcinoma cells more strongly than normal cells.

Synthesis and Photocatalytic CO2 Reduction of a Cyclic Zinc(II) Porphyrin Trimer with an Encapsulated Rhenium(I) Bipyridine Tricarbonyl Complex.

We previously reported a cyclic Zn(II) porphyrin trimer in which three Zn porphyrins are alternately bridged by three 2,2'-bipyridine (bpy) moieties, enabling the encapsulation of metal complexes within the nanopore formed by the Zn porphyrins. In this study, we introduced a [Re(CO)3 Br] fragment into one of the bpy moieties of the cyclic trimer to form the catalytic Re(4,4'-R2 -bpy)(CO)3 Br center (R=methyl ester). The ester groups (R) play an important role in the synthesis of the cyclic structure. However, it was observed that these ester groups significantly deactivated the photocatalytic CO2 reduction reaction. Therefore, we converted the ester groups with a suitable reducing reagent into hydroxymethyl groups, followed by acetylation to form acetoxymethyl groups. This modification remarkably enhanced the photocatalytic activity of the cyclic trimer=Re complex system for CO2 reduction. Moreover, in the modified system, the presence of the Re complex induced room-temperature phosphorescence of the Zn porphyrin. The phosphorescence was significantly quenched by 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole, indicating that efficient electron transfer mediated by the excited triplet state of the Zn porphyrin occurs during the photocatalytic CO2 reduction.

A novel synthesis of β-CD@SA@Ag composite hydrogel microspheres with high catalytic activity and environmental adaptability

The composite of hydrogels and noble metal nanoparticles has wide applications in the field of functional materials. In this paper, we developed a novel and green strategy to synthesize a kind of composite hydrogel microspheres containing silver nanoparticles and β-cyclodextrin (β-CD) modified sodium alginate (β-CD@SA@Ag) without use of strong reducing reagent. First, β-CD was chemical linked to SA by epichlorohydrin (ECH) to form the β-CD modified polymer (β-CD@SA). then AgNO3 was added to the as-prepared polymer solution, in which silver nanoparticles were formed by the reducing power of β-CD units. Subsequently, by reversed-phase emulsion method and ionic cross-linking, a kind of β-CD@SA@Ag hydrogel microspheres were obtained. The structure and morphology of the composite material were characterized in detail by Fourier infrared spectroscopy (FT-IR), thermogravimetric analysis (TG), scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). Test data indicated that silver nanoparticles evenly dispersed in the composite material. On the basis, the adsorption and catalytic performances of the β-CD@SA@Ag hydrogel microspheres were studied towards to the reduction of aromatic nitro compounds. Research results showed that the β-CD@SA@Ag hydrogel microspheres had excellent catalytic activity along with high environmental adaptability. whether in pure water, tap water or river water, aromatic nitro compounds can be completely reduced within 2–13 min. Moreover, the morphology of microspheres of the composite material endows the composite material with high stability and reusability. We believe that our work would provide a new idea for the green synthesis of organic-inorganic composite functional materials.

Gaining Insight into Mechanisms of Nonphotochemical Quenching of Chlorophyll Fluorescence in Chlamydomonas reinhardtii via the Observation of Dark-induced State Transitions

Photosynthetic organisms are usually exposed to fluctuating light, and therefore they evolved mechanisms enabling fast acclimation to changing light conditions. Among them, two important ones are energy-dependent quenching of excited chlorophyll (qE) and state transitions (ST). qE is a photoprotective mechanism regulated by pH gradient across thylakoid membranes, in which excessive energy is dissipated as heat. ST are rearrangements of antenna systems regulated by the phosphorylation of LHC II complexes. Both of these mechanisms result in changes in NPQ parameters. In the present article, changes of NPQ in the green microalga Chlamydomonas reinhardtii were evaluated in the dark period, after various lengths of actinic light exposure, and after the application of the thiol reducing reagent dithiotreitol and the cyt b6f inhibitor 2' ,4' -dinitrophenyl ether of 2-iodo-4-nitro-thymol. The impact of the length of actinic light exposure on xanthophyll cycle progression in C. reinhardtii was also analysed. The obtained results enabled us to gain more insight into the nonphotochemical quenching of chlorophyll fluorescence in model organism C. reinhardtii, i.e. the role of zeaxanthin-dependent quenching and chlororespiration-induced pH gradient, and the inhibitory action of tested compounds on state transitions in this species.

Metal-Free B-B Dehydrocoupling Reaction of a Simple Borane Adduct: Convenient Access to a Nucleophilic Diborane(4).

The selective formation of homonuclear bonds is of key importance in synthetic chemistry. Especially, dehydrocoupling reactions are attractive as ecologically and economically friendly alternatives to established reductive bond forming reactions, since they do not require the use of stoichiometric amounts of a reducing reagent and produce only valuable dihydrogen as by-product. Here, we report on a metal-free B-B dehydrocoupling reaction that starts directly from a simple, easily accessible BH3 adduct, providing convenient access to a new nucleophilic dihydridodiborane in excellent yield. The dihydridodiborane in turn activates dihydrogen, allowing to obtain quantitatively the dideuteridodiborane from the dihydridodiborane by D2 activation. On the basis of detailed quantum-chemical calculations, the mechanism of this unprecedented reaction is elucidated. Some key points that are essential for metal-free dehydrocoupling are disclosed, paving the way for their systematic evaluation and application.

Metallfreie B−B Dehydrokupplung eines Einfachen Boran‐Addukts: Bequemer Zugang zu einem Nukleophilen Diboran(4)

AbstractDie selektive Bildung homonuklearer Bindungen ist in der synthetischen Chemie von zentraler Bedeutung. Insbesondere Dehydrokupplungsreaktionen sind als ökologische und ökonomische Alternativen zu etablierten reduktiven Bindungsbildungsreaktionen attraktiv, da sie nicht den Einsatz stöchiometrischer Mengen eines Reduktionsmittels erfordern und nur wertvollen Wasserstoff als Nebenprodukt erzeugen. Hier berichten wir über eine metallfreie B−B‐Dehydrokupplungsreaktion, die direkt von einem einfachen, leicht zugänglichen BH3‐Addukt startet und einen bequemen Zugang zu einem neuen nukleophilen Dihydridodiboran in exzellenter Ausbeute bietet. Das Dihydridodiboran wiederum aktiviert Wasserstoff, sodass durch D2‐Aktivierung quantitativ das Dideuteridodiboran aus dem Dihydridodiboran erhalten werden kann. Auf Grundlage detaillierter quantenchemischer Berechnungen wird der Mechanismus dieser beispiellosen Reaktion aufgeklärt. Einige für die metallfreie Dehydrokupplung essenzielle Kernpunkte werden aufgezeigt und dadurch der Weg für einen systematischen Zugang und Anwendung bereitet.

MeOH‐Mediated Efficient Reduction with N‐Heterocyclic Carbene Boranes Towards the Synthesis of Cyclic Sulfamates and Sulfonamides

AbstractAn efficient approach for the reduction of cyclic N‐sulfonylimines using N‐heterocyclic carbene boranes as the hydride donor was developed, leading to various cyclic sulfamates and sulfonamides in excellent yields. The approach had broad scope including both the N‐sulfonyl aldimines and ketimines under mild reaction conditions, which proves that the NHC‐boranes are good alternatives as the reductive reagents.

Mercury-Mediated Epitaxial Accumulation of Au Atoms for Stained Hydrogel-Improved On-Site Mercury Monitoring.

Trivalent Au ions are easily reduced to be zerovalent atoms by coexisting reductant reagents, resulting in the subsequent accumulation of Au atoms and formation of plasmonic nanostructures. In the absence of stabilizers or presence of weak stabilizers, aggregative growth of Au nanoparticles (NPs) always occurs, and unregular multidimensional Au materials are consequently constructed. Herein, the addition of nanomole-level mercury ions can efficiently prevent the epitaxial accumulation of Au atoms, and separated Au NPs with mediated morphologies and superior plasmonic characteristics are obtained. Experimental results and theoretical simulation demonstrate the Hg-concentration-reliant formation of plasmonic nanostructures with their mediated sizes and shapes in the presence of weak reductants. Moreover, the sensitive plasmonic responses of reaction systems exhibit selectivity comparable to that of Hg species. As a concept of proof, polymeric carbon dots (CDs) were used as the initial reductant, and the reactions between trivalent Au and CDs were studies. Significantly, Hg atoms prevent the epitaxial accumulation of Au atoms, and plasmonic NPs with decreased sizes were in situ synthesized, corresponding to varied surface plasmonic resonance absorption performance of the CD-induced hybrids. Moreover, with the integration of sensing substrates of CD-doped hydrogels, superior response stabilities, analysis selectivity, and sensitivity of Hg2+ ions were achieved on the basis of the mercury-mediated in situ chemical reactions between trivalent Au ions and reductant CDs. Consequently, a high-performance sensing strategy with the use of Au NP-staining hydrogels (nanostaining hydrogels) was exhibited. In addition to Hg sensing, the nanostaining hydrogels facilitated by doping of emerging materials and advanced chem/biostrategies can be developed as high-performance on-site monitoring routes to various pollutant species.

Surface oxygen vacancies of TiO2–x enabled water transfer photocatalytic hydrogenation of nitrobenzene to aniline without use of co-catalyst

Water transfer photocatalytic hydrogenation of nitrobenzene to aniline is an attractive and environmentally friendly process in chemical manufacturing. Herein, through an in-situ CO reduction pathway, the TiO2-based photocatalysts with surface and subsurface VOs are prepared for water transfer hydrogenation of nitrobenzene to aniline. The CO originated from incomplete combustion of residual organic compounds of the TiO2 precursor (tetrabutyl titanate), can react with the lattice oxygen of TiO2 and obtain rich surface and subsurface VOs TiO2-based photocatalysts without additional reduction reagent. The as-prepared TiO2 catalyst exhibits a desired band structure and rapid separation of photogenerated carriers. Besides, the TiO2 catalyst with surface and subsurface VOs can stabilize intermediates for water transfer hydrogenation. Thus, compared with heteroatom doping and poor-VOs TiO2, the TiO2 catalyst exhibits highly selectivity and conversion for photocatalytic hydrogenation of nitrobenzene substrates without the use of any cocatalyst and reductant H2.

Control of Non-Ferrous Metal-Sulfide Minerals’ Flotation via Pulp Potential

Studies on the dependence of the technological results of non-ferrous sulfide ore (copper—arsenic-bearing and non-arsenic-bearing—lead–zinc, and polymetallic) flotation on the pulp potential Eh are reviewed. Findings on the relation of Eh and collectorless flotation are presented. Changes in the pulp potential due to different gas applications and various reagent additions are considered. The influence of the grinding medium on the pulp Eh and hence on the flotation results is presented through various examples. The relation between the oxidation–reduction potential and reagent effects is exhibited and explained. pH–Eh ranges of different minerals’ flotation, as recorded in various studies, are summarized and visualized jointly for all mentioned ores. It is concluded that the pulp Eh value, considered together with the pH value, is a useful means for flotation selection controlling and deserves further research, especially under industrial conditions. Some problems and difficulties in using pulp Eh for flotation control are discussed.

Electroreductive Umpolung Enabling Reformatsky‐Type Reaction of Bromodifluoroamides with Aldehydes/Ketones

AbstractAn electrochemical Reformatsky‐type reaction of bromodifluoroamides with aldehydes/ketones via electron reductive umpolung is reported, leading to the generation of a series of β‐hydroxy‐α,α‐difluoro amides in moderate to good yields. This protocol tolerated a variety of commercially available alkyl ketone, alkyl and aromatic aldehydes, featuring broad substrate scope and good functional group tolerance under transition metal‐free conditions without metal reduction reagents. Control experiment indicated that the reaction proceeded via an electron reductive umpolung pathway.

Application of combined hydrodynamic cavitation and Fenton reagent for COD reduction of cellulosic fiber industry effluents

The present work demonstrates the implementation of combined approach of hydrodynamic cavitation reactor and Fenton oxidation process for the treatment of three cellulosic fiber (CF) industry effluent streams using pilot scale reactor with operation at 500 L developed at an industrial site. In order to assess the techno-economic viability of the combined hydrodynamic cavitation (HC) and Fenton oxidation process, various sets of experimental runs were carried out. Effect of type of treatment approach, one step and stepwise addition of oxidants, number of cavitation passes, and finally the type of effluent varying in terms of initial chemical oxygen demand (COD) on the efficacy of treatment were studied. Based on the results, HC + Fenton oxidation scheme was demonstrated to be a viable option for the treatment of CF industry effluent streams. HC + Fenton treatment rapidly reduced COD, achieving almost 90 % reduction in just 10 min, highlighting its efficiency in industrial wastewater treatment. The treatment achieved substantial reduction in residual COD levels with actual value as up to 1000 mg/L COD in effluent-I, up to 150 mg/L COD in effluent-II, and up to 100 mg/L COD in effluent-III. The study also explored the operating cost expenditure (Opex) of the proposed system required to demonstrate it at a commercial level, including the cost of chemicals and electricity. The COD reduction cost evaluated were INR 140–230/kg COD depending on the effluent. The main highlight of the article is the practical demonstration at the manufacturing unit including the operating cost calculations.

Instantaneous and reversible flocculation of Scenedesmus via Chitosan and Xanthan Gum complexation

An instantaneous and reversible flocculation method for Scenedesmus harvesting was developed, based on the complexation of Chitosan (CTS) and Xanthan Gum (XG). Under rapid stirring, Scenedesmus cells formed centimeter-sized flocs within 20 s using binary flocculants of 4 mg/L CTS and 16 mg/L XG. These flocs exhibited a remarkable harvest efficiency exceeding 95 % when filtered through 500-μm-pore-sized sieves. Furthermore, the flocs could be completely disintegrated by using alkaline or NaCl solutions (pH > 11 or NaCl concentration > 1.5 mol/L). Adjusting pH allowed recovery of 50 % CTS and 75 % XG, resulting in microalgae biomass with lower flocculant content and reducing reagent costs. Electrostatic interaction of –COO– of XG and –NH3+ of CTS deduced the formation of polyelectrolyte complexes (PECs), which shrink and wrap the coexisting algal cells to form the flocs under stirring. CTS and XG complexation was instantaneous and reversible, explaining quick flocculation and disintegration.