Ultrasound-assisted synthesis of monodisperse Ru–B amorphous alloys with enhanced catalytic activity in maltose hydrogenation

Monodisperse Ru–B amorphous alloy catalysts were synthesized by ultrasound-assisted chemical reduction of (NH₄)₂RuCl₆ with BH ₄ ^? . With the characterization of X-ray diffraction (XRD), selective area electronic diffraction (SAED), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM), the resulting Ru–B nanoparticles were identified to be amorphous alloys ranging in size from 2.4 to 4.9 nm. During liquid-phase maltose hydrogenation, the as-synthesized Ru–B catalyst was extremely active compared to the regular Ru–B obtained via the reduction of RuCl₃ with BH ₄ ^? . The Ru–B sample prepared under ultrasonication with 60 W was proven to be the most active catalyst. Its catalytic activity was nearly 11 times that of industrial Raney Ni, and could be used repetitively for more than six times without significant deactivation.     

Cellulose-TiO2 nanocomposite with enhanced UV–Vis light absorption

TiO₂/N-cellulose nanocomposite was successfully prepared in the (cyclohexyl)hexyl-dimethylammonium acetate–dimethyl sulfoxide solution. The obtained composite was characterized with various techniques like UV–Vis/DR, FTIR/DRS, X-ray diffraction, thermogravimetric analysis, DLS method and BET SSA measurements. TiO₂/N-cellulose nanocomposite exhibited high UV–Vis light absorption with energy gap shifted to the visible region. Additive of TiO₂/N photocatalyst to cellulose-IL-DMSO solution leads to obtaining the material with higher thermostability and limited photoactivity.     

Colorimetric sensing of cyanide anion in aqueous media with a fluorescein–spiropyran conjugate

A fluorescein–spiropyran conjugate (2) behaves as a receptor for colorimetric sensing of cyanide anion (CN^?) in aqueous media under irradiation of UV light. The compound 2, which exists as a spirocycle-closed (SP) form in the dark condition, is isomerized to the spirocycle-opened merocyanine (MC) form upon irradiation of UV light and shows absorption bands at 467 and 568 nm. Addition of CN^? to the solution leads to a decrease in these bands and an appearance of new absorption band at 512 nm, via a nucleophilic interaction between CN^? and the spirocarbon of MC form. This absorption change occurs selectively with CN^? and enables ratiometric quantification of CN^? by absorption analysis.     

Trace Ir(Ⅲ) complex enhanced electrochemiluminescence of AIE-active Pdots in aqueous media

Trace Ir(Ⅲ) complex enhanced aggregation-induced electrochemiluminescence(AIECL) of poly-tetraphenylethene(p TPE) in aqueous media was investigated for the first time. The poly-TPE end-capped by Ir(Ⅲ) complex(Ir@p TPE) and its corresponding model polymer poly-TPE(Ph@pTPE) could be synthesized by Suzuki coupling polymerization reaction of 1,2-bis(4-bromophenyl)-1,2-diphenylethene(M-1) with 1,2-diphenyl-1,2-bis(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)ethene(M-2) and the continuous Suzuki coupling end-capped reaction of poly-TPE-pinacol boronate with(pq)2 Ir(pico)Br and bromobenzene, respectively. Subsequently, the corresponding Ir@p TPE Pdots and Ph@p TPE Pdots encapsulated with poly(styrene-co-maleicanhydride)(PSMA) could be obtained by nanoprecipitation method. Compared with Ph@p TPE Pdots, the Ir@p TPE Pdots with a trace amount of Ir(Ⅲ) complex(1.34‰ of Ir(Ⅲ) content, wt) could exhibit 9.9-fold enhancement of the electrochemiluminescence(ECL) signal for visual emission. This work provided a novel strategy on designing highly efficient ECL materials based on trace Ir(Ⅲ)-end capping AIE-active polymer dots.     

Lead-promoted Barbier-type reaction of aldehydes with propargyl bromides in aqueous media

This paper reports that the reaction of the propargyl bromides with aldehydes promoted by powdered lead in aqueous media.The selectivity and possible mechanism of these reactions are discussed.The yields of products for reaction of propargyl bromide are 31~71%.The ratios of al-lenyl alcohol and homopropargyl alcohol are 1:1.5 to 1:3.The product for reaction of phenyl propargyl bromide is allenyl alcohol and the yields are 52~84%.     

Rh–Cu alloy nano-dendrites with enhanced electrocatalytic ethanol oxidation activity

The application of direct ethanol fuel cell(DEFC) has been bottlenecked by the sluggish ethanol oxidation reaction(EOR). Efficient electrocatalysts for the C-C bond cleavage are essential to promote EOR with high efficiency and C1 selectivity. Here, we prepared Rh–Cu alloy nano-dendrites(RhCu NDs) with abundant surface steps through controlled co-reduction, which exhibited significantly enhanced activity and C1 selectivity(0.47 m A cm₍(ECSA))^-2, 472.4 mA mg_Rh     

Irradiation of Fe–Mn@SiO2 with microwave energy enhanced its Fenton-like catalytic activity for the degradation of methylene blue

Research on Chemical Intermediates - The application of microwave energy in the synthesis of catalytic materials has been indicated to induce desirable effects that lead to improved activity....     

Fabrication of magnetically separable palladium–graphene nanocomposite with unique catalytic property of hydrogenation

One step solvothermal route has been developed to prepare a well dispersed magnetically separable palladium–graphene nanocomposite, which can act as a unique catalyst against hydrogenation due to the uniform decoration of palladium nanoparticles throughout the surface of the magnetite–graphene nanocomposite and hence can be reused for several times. In addition to catalytic activity, palladium nanoparticles also facilitate the formation and homogeneous distribution of magnetite (Fe₃O₄) nanoparticles onto the graphene surfaces or else an agglomerated product has been obtained after the solvothermal reduction of graphene oxide in presence of Fe³⁺ alone.     

One-pot synthesis of graphene–cuprous oxide composite with enhanced photocatalytic activity

In this paper, graphene–cuprous oxide (G–Cu₂O) composites were synthesized at room temperature using graphene oxide (GO) as two-dimensional support. From Zeta potential analysis, the surface charge of G–Cu₂O composites altered from positive to negative, which favors the adsorption and photodegradation of positively charged dyes. Compared with Cu₂O under similar synthesis condition, the G–Cu₂O composites demonstrated improved photodegradation activity for methylene blue (MB) dye under visible light. Controlled experiments indicated that the G–Cu₂O composite synthesized with 80 mg GO in the reaction system possessed more negative Zeta potential, highest specific surface area and thus presented the highest photocatalytic activity. Electrons mechanism for the improved photocatalytic performance of G–Cu₂O composite was proposed in the degradation of MB.     

Electrocatalytic activity of palladium–polypyrrole nanocomposite in the formaldehyde oxidation reaction

Palladium–polypyrrole nanocomposite materials with high electrocatalytic activity toward formaldehyde in an alkaline solution (methylene glycolate) have been synthesized via a one-step redox route. Key factors that have an effect on the sensor properties of palladium nanoparticles have been determined. It has been demonstrated for the first time that the emergence of not only the forward but also the reverse wave of formaldehyde oxidation on palladium particles is associated with the oxidation of methylene glycolate rather than intermediate species.     

CeO2 nanofibers-CdS nanostructures n–n junction with enhanced visible-light photocatalytic activity

In the present work, the n-cerium (IV) oxide (CeO₂)/n-cadmium sulfide (CdS) composite nanofibers were successfully synthesized via a facile electrospinning and hydrothermal synthesis strategy. The physicochemical properties of the synthesized composite nanofibers were investigated by using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy Dispersive X-Ray Spectroscopy (EDS), diffuse Reflectance Spectroscopy (DRS), Fourier-transform infrared (FTIR), photoluminescence (PL), Brunauer–Emmett–Teller (BET) and Raman spectroscopy analysis. The activities of the CeO₂/CdS were evaluated through the photocatalytic degradation of Rose Bengal (RB) in an aqueous solution under blue LED light radiation. CeO₂/CdS composites exhibit higher photocurrent density in photocurrent response experiment and smaller charge-transfer resistance in electrochemical impedance spectroscopy (EIS). Overall, the results confirmed higher charge separation efficiency in CeO₂/CdS composites compared to pristine CeO₂ nanofibers, and CdS, which is related to intimately contact among the CeO₂, and CdS. The present work provides a new approach to construct n-n heterojunction photocatalysts based on electrospinning and a deeper insight for the photocatalytic degradation activity. In addition, possible degradation mechanism and pathways were proposed according to the identified intermediates.     

Gold nanoparticles immobilized on metal–organic frameworks with enhanced catalytic performance for DNA detection

In this work, gold nanoparticles (AuNPs) assembled on the surface of iron based metal–organic frameworks (MOFs), Fe-MIL-88, are facilely prepared through electrostatic interactions using polyethyleneimine (PEI) molecules as linker. The resulting hybrid materials possess synergetic peroxidase-like activity. Because iron based metal–organic frameworks, Fe-MIL-88, exhibits highly peroxidase-like activity, and AuNPs has the distinct adsorption property to single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The peroxidase-like activity of Au@Fe-MIL-88 exhibit excellent switchable in response to specific DNA, ssDNA is easily adsorbed on the surface of the Au@Fe-MIL-88 hybrids, resulting in the reduce of the peroxidase-like activity of the hybrids. While it is recovered by the addition of target DNA, and the recovery degree is proportional to the target DNA concentration over the range of 30–150 nM with a detection limit of 11.4 nM. Based on these unique properties, we develop a label-free colorimetric method for DNA hybridization detection. In control experiment, base-mismatched DNA cannot induce recovery of the peroxidase-like activity. This detection method is simple, cheap, rapid and colorimetric.     

Heterogeneous Fenton-like reactions with a novel hybrid Cu–Mn–O catalyst for the degradation of benzophenone-3 in aqueous media

This study focuses on the heterogeneous Fenton-like reaction performed over a novel hybrid Cu–Mn–O catalyst for the degradation of a model compound benzophenone-3 (BP-3) in aqueous media. The hybrid Cu–Mn–O catalysts with different Cu/Mn molar ratios were synthesized using co-precipitation and hydrothermal methods, and their composition and morphology were characterized using XRD and SEM analyses. Key parameters including the Cu/Mn ratio in the synthesis, pH and titration of H₂O₂ were shown to significantly influence the degradation of BP-3. A hybrid catalyst with a chemical composition of Cu_1.4Mn_1.6O₄, Mn₃O₄, and Mn₂O₃ exhibiting a morphology of nanofibers and nanoparticles demonstrated the highest catalytic activity in the degradation of BP-3. After 240 min of degradation, 81.5% of BP-3 was removed, which could be mostly related to the presence of hydroxyl radicals (˙OH). Unlike the conventional Fenton reaction that performs well under highly acidic conditions, BP-3 can be degraded in a wider pH range (2.6–7.1) in the Fenton-like reaction presented herein. Considering the mild conditions used for this Fenton-like system, this novel hybrid catalyst remains promising for wastewater treatment.     

Indium-mediated allylation of aryl trichloromethyl ketones in aqueous media

It is described that indium-mediated allylation of trichloromethyl ketones could afford the corresponding homoallylic alcohols smoothly in aqueous media.     

One-pot tandem Barbier-Prins synthesis of tetrahydropyrans in aqueous media

Tetrahydropyran is an important structural core ofmany carbohydrates and their polymers. Its structure ispresent in numerous natural compounds such as poly-ether antibiotics, marine toxins and pheromones[1,2].Thus many reactions have been developed toward…     

Core–shell magnetic Fe3O4/CNC@MOF composites with peroxidase-like activity for colorimetric detection of phenol

Rapid and accurate detection of phenolic wastewater from industries has created global concern. Herein, core–shell magnetic cellulose nanocrystal supported MOF (Fe₃O₄/CNC@ZIF-8) with robust peroxidase-like activity was synthesized with tannic acid as modifier and bridge. The peroxidase-mimic catalytic activity of as-prepared Fe₃O₄/CNC@ZIF-8 was further investigated using o-phenylenediamine (OPD) as peroxidase substrates in the presence of H₂O₂. Moreover, the experimental conditions were optimized and the kinetic analysis results showed that Fe₃O₄/CNC@ZIF-8 had higher affinity towards both the substrate OPD and H₂O₂ than horseradish peroxidase (HRP). Finally, a phenol colorimetric assay with a linear range of 2–200 µM and a detection limit of 0.316 µM was constructed. The catalytic mechanism of Fe₃O₄/CNC@ZIF-8 with phenol was further investigated by fluorescence test and the generated ·OH was proved to act a crucial role to produce quinoid radicals. Additionally, the synthesized magnetic material had excellent stability and recyclability and ease to separation. These results suggest that the Fe₃O₄/CNC@ZIF-8 may be one of the promising candidates as peroxidase mimic for colorimetric detection of phenol.

     

Photophysical properties of CdSe/ZnS quantum dot–porphyrin surface complexes in aqueous media

We have studied complexes between CdSe/ZnS quantum dots and metal-free porphyrin molecule in aqueous solution and in human blood plasma. We have established that in aqueous solution, transition of the porphyrin to a stable form occurs 2-5 h after formation of the complexes. We have observed that the porphyrin molecules react with the components of the blood plasma, which hinders direct formation of complexes between them and quantum dots in this medium. When previously prepared complexes between quantum dots and porphyrin molecules are added to the blood plasma, they partially dissociate. In aqueous solutions and in human blood plasma, we observe efficient intracomplex transfer of the photoexcitation energy from the quantum dots to the porphyrin molecules.     

Platinum–titanium intermetallic nanoparticle catalysts for oxygen reduction reaction with enhanced activity and durability

A facile method to prepare Pt–Ti intermetallic nanoparticles supported on carbon was developed. Starting from a commercial Pt/C catalyst, TiO₂ layers were formed on the Pt/C then thermal annealing under a reducing condition successfully produced intermetallic Pt–Ti nanoparticles with an average size of 4.2 nm. The intermetallic Pt–Ti/C showed enhanced activity and durability for oxygen reduction reaction due to the change in electronic structure and less aggregation.     

An approach to the Paal–Knorr pyrroles synthesis in the presence of β-cyclodextrin in aqueous media

An efficient and facile method for the synthesis of N-substituted pyrroles in moderate to good yields by the Paal–Knorr reaction of γ-diketones with amines in the presence of β-cyclodextrin in aqueous media has been developed.Moreover,this process tolerated diamines(e.g.,para-,meta- or orthophenylenediamine)to construct bis-pyrrole or mono-pyrrole derivates.β-Cyclodextrin can be recovered easily after the reactions and reused without evident loss in activity.