Reduction Of 4-nitroaniline Research Articles

A novel approach for the synthesis of ultrathin silica-coated iron oxide nanocubes decorated with silver nanodots (Fe3O4/SiO2/Ag) and their superior catalytic reduction of 4-nitroaniline.

A novel sonochemical approach was developed for the synthesis of different core/shell structures of Fe3O4/SiO2/Ag nanocubes and SiO2/Ag nanospheres. The total reaction time of the three sonochemical steps for the synthesis of Fe3O4/SiO2/Ag nanocubes is shorter than that of the previously reported methods. A proposed reaction mechanism for the sonochemical functionalization of the silica and the silver on the surface of magnetic nanocubes was discussed in detail. Transmission electron microscopy revealed that the surface of Fe3O4/SiO2 nanocubes was decorated with small Ag nanoparticles of approximately 10-20 nm in size, and the energy dispersive spectroscopy mapping analysis confirmed the morphology of the structure. Additionally, X-ray diffraction data were used to confirm the formation of both phases of a cubic inverse spinel structure for Fe3O4 and bcc structures for Ag in the core/shell structure of the Fe3O4/SiO2/Ag nanocubes. The as-synthesized Fe3O4/SiO2/Ag nanocubes showed a high efficiency in the catalytic reduction reaction of 4-nitroaniline to 4-phenylenediamine and a better performance than both Ag and SiO2/Ag nanoparticles. The grafted silver catalyst was recycled and reused at least fifteen times without a significant loss of catalytic efficiency.

Bacterial surface display of metal binding peptides as whole-cell biocatalysts for 4-nitroaniline reduction

Using recombinant microorganisms expressing metal binding peptides as whole-cell biocatalysts for 4-nitroaniline reduction.

Photocatalytic applications with CdS • block copolymer/exfoliated graphene nanoensembles: hydrogen generation and degradation of Rhodamine B

Amphiphilic block copolymer poly(isoprene-b-acrylic acid) (PI-b-PAA) was used to stabilize exfoliated graphene in water, allowing the immobilization of semiconductor CdS nanoparticles forming CdS • PI-b-PAA/graphene. Characterization using high-resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy proved the success of the preparation method and revealed the presence of spherical CdS. Moreover, UV–Vis and photoluminescence assays suggested that electronic interactions within CdS • PI-b-PAA/graphene exist as evidenced by the significant quenching of the characteristic emission of CdS by exfoliated graphene. Photoillumination of CdS • PI-b-PAA/graphene, in the presence of ammonium formate as a quencher for the photogenerated holes, resulted in the generation of hydrogen by water splitting, monitored by the reduction of 4-nitroaniline to benzene-1,4-diamine (>80 ± 4% at 20 min; 100% at 24 min), much faster and more efficient compared to when reference CdS • PI-b-PAA was used as the photocatalyst (<30 ± 3% at 20 min; 100% at 240 min). Moreover, Rhodamine B was photocatalytically degraded by CdS • PI-b-PAA/graphene, with fast kinetics under visible light illumination in the presence of air. The enhancement of both photocatalytic processes by CdS • PI-b-PAA/graphene was rationalized in terms of effective separation of holes and electrons, contrary to reference CdS • PI-b-PAA, in which rapid recombination of the hole–electron pair is inevitable due to the absence of exfoliated graphene as a suitable electron acceptor.

Flowerlike Bi2S3microspheres: facile synthesis and application in the catalytic reduction of 4-nitroaniline

Flowerlike Bi2S3 microspheres have been successfully synthesized via a facile wet chemical route in air at 110 °C for 10 min, employing bismuth nitrate and thiourea in a molar ratio of 1 : 2 as the starting reactants, ethylene glycol as the reaction medium and polyvinylpyrrolidone (PVP) as the structure-directing reagent. Electron microscopy observations showed that the as-obtained product looked like an Asteraceae plant called Echinops Sphaerocephalus Linn in nature. The N2 sorption–desorption experiments showed that the Brunauer–Emmett–Teller (BET) area of the flowerlike microspheres was 32.4 m2 g−1. Some factors influencing the formation of flowerlike Bi2S3 microspheres were investigated, including the reaction temperature, and the sort and amount of the surfactant. The experiments showed that the Bi2S3 micro/nanostructures prepared in the present work could be used as new-type catalysts for the reduction of some aromatic nitro compounds, such as 4-nitroaniline, 2-nitrophenol and 4-nitrophenol. It was found that the as-obtained flowerlike Bi2S3 microspheres contributed to the best catalytic activity.

Constructing robust liquid marbles for miniaturized synthesis of graphene/Ag nanocomposite.

Miniaturized synthesis is attracting much attention due to many potential applications; a challenge remains in exploring versatile microreactors capable of producing pure products. In this study, we reported a kind of thermally robust liquid marbles and their application for miniaturized synthesis of graphene/Ag nanocomposite. The liquid marbles were constructed by using superhydrophobic Fe3O4/C microsheets as encapsulating agents. Results revealed that the morphology of the encapsulating agent as well as the humidity of atmosphere strongly affected the robustness of liquid marbles at elevated temperature. The resulting graphene/Ag nanocomposite showed one of the best catalytic characteristics for 4-nitroaniline reduction among the reported catalysts. The findings of this study not only offer an alternative insight into the stability of liquid marbles at elevated temperature but also provide a facile strategy for miniaturized synthesis.

The self-assembling of DNA-templated Au nanoparticles into nanowires and their enhanced SERS and catalytic applications

A simple photochemical technique is described for the synthesis of organized assemblies of Au nanoparticles (NPs) on a DNA template in a shorter time scale. The smaller Au nanoparticles (NPs) are initially formed in the DNA solution, self-assembled together, and generate the nanowire structures. The diameter and the length of the nanowires can be tuned by controlling the different reaction parameters. The average diameters of the individual Au NPs could be varied in the range of 10–50 nm, whereas their lengths could be extended to the level of several micrometres. The mechanism for the formation of the self-assembled structure of Au NPs on DNA is elaborated upon. The DNA–Au nanowire shows a highly stable and reproducible signal in surface enhanced Raman scattering (SERS) studies. The SERS activity was examined with Rhodamine 6 G (R6G) as a model dye molecule and the observed enhancement factor (EF) was ∼106. The catalytic activity was tested for the reduction of 4-nitroaniline (4-NA) with sodium borohydride in aqueous solution. The synthesized Au nanowires were found to be stable for more than six months under ambient conditions at room temperature without any change of the optical properties. The superior SERS and catalytic activities of the material might be useful in future for different applications in organic catalysis reactions and in a variety of SERS based detections of bio-molecules, as sensors etc.

A new insight into the photocatalytic reduction of 4-nitroaniline to p-phenylenediamine in the presence of alcohols

Photoreduction of 4-nitroaniline to p-phenylenediamine over TiO2, ZnO, PbBi2Nb2O9 and CdS photocatalysts in the presence of CH3OH was investigated under light irradiation (hv≥band gap) upon purging with N2. Compared with PbBi2Nb2O9 and CdS, TiO2 and ZnO showed photocatalytic activities for the photoreduction of 4-nitroaniline. Electron spin resonance analysis results revealed that a methanol radical could be detected in the present of TiO2 and ZnO. Its formation was attributed to the reaction between the hydroxyl radical and CH3OH molecule. The species had strong reductive ability, and therefore could reduce 4-nitroaniline to p-phenylenediamine. Other alcohols (C2H5OH and i-C3H7OH) were also found to be efficient additives for the photoreduction of 4-nitroaniline. The results of the 2H-labeled experiments indicated that the p-phenylenediamine formation was formed by the hydrogen transfer reaction between the 4-nitroaniline and H2O molecules. A mechanism was proposed to explain the photoreduction of 4-nitroaniline to p-phenylenediamine in the present alcohols.

Facet-Dependent Catalytic Activity of Gold Nanocubes, Octahedra, and Rhombic Dodecahedra toward 4-Nitroaniline Reduction

In this study, cubic, octahedral, and rhombic dodecahedral gold nanocrystals synthesized by a seed-mediated growth method were employed as catalysts for the examination of facet-dependent catalytic activity toward NaBH4 reduction of p-nitroaniline to p-phenylenediamine at different temperatures. Different amounts of the nanocrystal solutions were used so that all samples contain particles with the same total surface area. UV–vis absorption spectra monitored the reaction progress. Rhombic dodecahedra showed the best catalytic efficiency at all the temperatures examined. Nanocubes have higher reaction rates than those of octahedra from 25 to 36 °C, so the catalytic activity for the reduction reaction follows the order of {110} > {100} > {111}. However, the reaction rates for octahedra increase rapidly with rising temperature; their reaction rate surpasses that for the nanocubes at 40 °C. Rate constants and activation energies were determined, again showing that the activation energy is lowest for rhombic dodecahedra. Density functional theory (DFT) calculations indicate highest binding energy between p-nitroaniline and the Au(110) plane. The results reveal rhombic dodecahedral gold nanocrystals as highly efficient catalysts.

Synthesis and characterization of NiFe2O4–Pd magnetically recyclable catalyst for hydrogenation reaction

Herein we report the fabrication and characterization magnetically recyclable catalysts of NiFe2O4–Pd nanocomposite as highly effective catalysts for reduction reactions in liquid phase. The reduction Pd2+ was accomplished with polyethylene glycol 400 (PEG-400) instead of sodium borohydride (NaBH4) and NiFe2O4 nanoparticles was prepared by sonochemically using FeCI3·6H2O and NiCl2. The chemical characterization of the product was done with X-ray diffractometry, Infrared spectroscopy, transmission electron microscopy, UV–Vis spectroscopy, thermal gravimetry and inductively coupled plasma. Thus formed NiFe2O4–Pd MRCs showed a very high activity in reduction reactions of 4-nitro aniline and 1,3-dinitrobenzene in liquid phase. It was found out that the catalytic activity of NiFe2O4–Pd MRCs on the reduction of 4-nitro aniline and 1,3-dinitrobenzene in liquid phase are between 99–93% and 98–93%, respectively. Magnetic character of this system allowed recovery and multiple use without significant loss of its catalytic activity. It is found that NiFe2O4–Pd MRCs showed very efficient catalytic activity and multiple usability.

Gold nanoparticle embedded hydrogel matrices as catalysts: Better dispersibility of nanoparticles in the gel matrix upon addition of N-bromosuccinimide leading to increased catalytic efficiency

A simple and convenient method for generating and immobilizing gold NPs into polyethylene glycol-polyurethane (PEGPU) matrices is presented. The gold NP immobilized PEGPU (Au NP-PEGPU) hydrogel matrices are easy to handle and can be used as catalysts. The efficiency, reusability and durability of the Au NP-PEGPU catalyst matrices were investigated using the reduction of 4-nitroaniline (4NA) to p-phenylenediamine (p-PDA) by sodium borohydride in the presence of the catalyst as a test reaction. The Au NPs in the PEGPU matrix got aggregated after 3 cycles of catalysis but dispersion could be regenerated by the addition of N-bromosuccinimide (NBS). After this regeneration process the Au NPs-PEGPU matrix showed excellent efficiency without any aggregation, leaching or degradation. The reusability of the catalyst for 28 cycles yielding a total turnover number of 3220 and turn over frequency of 0.152s−1 is demonstrated.

Efficient visible-light-induced photocatalytic reduction of 4-nitroaniline to p-phenylenediamine over nanocrystalline PbBi2Nb2O9

Nanocrystalline PbBi2Nb2O9 was successfully prepared by a modified sol–gel method. The as-prepared nanocrystalline PbBi2Nb2O9 was an active visible-light-driven photocatalyst for the photoreduction of 4-nitroaniline to p-phenylenediamine in aqueous solution upon purging with N2. Its photocatalytic activity was determined by the balance between the surface area and crystallinity. The best sample was obtained after calcination at 650°C, giving 4-nitroaniline conversion of ∼100% and p-phenylenediamine selectivity of ∼99% after irradiation for 150min, which was much higher than those of bulk PbBi2Nb2O9 and TiO2−xNx photocatalysts. Further experiments revealed that oxalate anion (as a hole scavenger) was indispensable for the photocatalytic reduction of 4-nitroaniline. Moreover, on the basis of the electron spin resonance analysis result, a mechanism was proposed to explain the photoreduction of 4-nitroaniline over nanocrystalline PbBi2Nb2O9.

A simple and highly efficient route for the preparation of p-phenylenediamine by reducing 4-nitroaniline over commercial CdS visible light-driven photocatalyst in water

Highly efficient photocatalytic reduction of 4-nitroaniline to p-phenylenediamine over a commercial CdS photocatalyst was observed under visible light irradiation (λ ≥ 420 nm) in water. The conversion of 4-nitroaniline and the selectivity of p-phenylenediamine were ∼100% and ∼98% after 9 min of visible light irradiation, respectively. The photoreduction efficiency of 4-nitroaniline over the CdS photocatalyst remained above 95% in the 5th cycle of testing. Its photocatalytic activity was much higher than those of nitrogen-doped TiO2 and commercial TiO2 photocatalysts. Further experimental results revealed that the ammonium formate and N2 atmosphere were indispensable for the photocatalytic reduction of 4-nitroaniline over the CdS photocatalyst. On the basis of the results of electron spin resonance, photoexcited electrons and ·CO2− radicals were detected in the present system. These species had strong reductive powers, and were therefore able to efficiently reduce 4-nitroaniline to p-phenylenediamine.

High efficient photocatalytic reduction of 4-nitroaniline to p-phenylenediamine over microcrystalline SrBi2Nb2O9

Abstract High efficient photocatalytic reduction of 4-nitroaniline to p-phenylenediamine over microcrystalline SrBi2Nb2O9 was observed upon purging with N2 under UV-light irradiation. Its photocatalytic activity was higher than that of sample P25 (commercial TiO2, Degussa Co.). The analysis results of X-ray diffraction and X-ray photoelectron spectroscopy revealed that microcrystalline SrBi2Nb2O9 had high stability for the photocatalytic reduction of 4-nitroaniline. Further experiments indicated that ammonium oxalate was indispensable for the photocatalytic reduction of 4-nitroaniline. Moreover, the high efficient photocatalytic reduction of 4-nitroaniline over microcrystalline SrBi2Nb2O9 might be ascribed to its relatively high conduction band.

Ampholyte polystyrene spheres self-regulated deposition of noble metal nanoparticles for catalyst applications

The polystyrene (PS) spheres having dual functional groups were synthesized using emulsifier-free emulsion polymerization based on St/potassium persulfate/water system in the presence of V-50 as co-initiator. Fourier transform infrared (FTIR) confirms the presence of the sulfate and the amino groups on the surfaces of PS spheres. Transmission electron microscopy and X-ray photoelectron spectra revealed that the PS spheres were successfully deposited with catalytic palladium (Pd) or gold (Au) nanoparticles (NPs). The reduction of 4-nitroaniline to 4-phenylenediamine used as a model reaction was performed for catalysis studies and examined by ultraviolet. It was found that both Au and Pd PS dispersions show high catalytic activity. The Pd PS dispersion of 200 μl with only Pd content of 1.09 wt.% exhibits an excellent catalytic effect superior to the commercial Pd/C catalyst, i.e., less than 35 s taken for the completion of the reduction of 4-nitroaniline.

Constructing magnetic polyaniline/metal hybrid nanostructures using polyaniline/Fe 3O 4 composite hollow spheres as supports

Polyaniline (PANI)/Fe 3O 4 composite hollow spheres have been successfully synthesized in one step using sulfonated polystyrene (PS) spheres as templates. The magnetic PANI hollow spheres were used as supports for noble metal nanoparticles (NPs) such as Au and Pd. The morphology, composition and magnetic properties of the resulting products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, inductively coupled plasma (ICP) atomic spectra and vibrating sample magnetometer. The catalytic activity of magnetic PANI/Au composite shells on the oxidation of dopamine was investigated by cyclic voltammetry. The obtained results provide our product with a practical application for the detection of dopamine. On the other hand, the catalytic activity of magnetic PANI/Pd composite shells on the reduction of 4-nitroaniline was investigated by spectroscopic methods and compared with Pd/C catalyst which was already widely used in industrial production.

Two-dimensional assembly of silver nanoparticles for catalytic reduction of 4-nitroaniline

Silver nanoparticles were assembled into a two-dimensional submonolayer structure on the surface of glass slides. The immobilized silver nanoparticles showed excellent catalytic activity for the reduction of 4-nitroaniline by borohydride. The immobilized catalyst can be conveniently recovered from the reaction system, leading to easy monitoring of the catalytic reaction by the spectroscopic methods. Results indicate that the silver nanoparticles function as the electron relay in the catalytic reduction process. The direct contact of 4-nitroaniline molecules with silver nanoparticles is necessary for the electron transfer from the electron-donating molecules to the accepting molecules through the silver nanoparticles.