Reduction Of 4-nitroaniline Research Articles

Pd/CoFe2O4/chitosan: A highly effective and easily recoverable hybrid nanocatalyst for synthesis of benzonitriles and reduction of 2-nitroaniline

In this study, a novel catalyst system with high activity and easy recoverability was successfully prepared through the deposition of Pd nanoparticles (NPs) onto designed sustainable hybrid beads containing magnetic cobalt ferrite and chitosan (Pd/CoFe2O4/chitosan). The catalytic potential of Pd/CoFe2O4/chitosan hybrid nanocatalyst was then assessed in i) preparation of benzonitriles via aryl halides cyanation and ii) reduction of 2-nitroaniline (2-NA). Various aryl iodides and bromides were successfully cyanated by Pd/CoFe2O4/chitosan hybrid nanocatalyst with excellent reaction yields within 3 h. In addition to the production of benzonitriles, the hybrid nanocatalyst showed excellent activity by reducing 2-NA in 65 s. It was proved that the Pd/CoFe2O4/chitosan hybrid nanocatalyst outperformed many catalysts used in the cyanation of aryl halides and catalytic reduction of 2-NA previously reported in the literature. Moreover, it was found that the designed Pd/CoFe2O4/chitosan hybrid nanocatalyst was easily and effectively separated from the reaction mixture using an external magnet and reused several times in catalytic reactions without considerable loss of catalytic activity.

Cu/CuO Composite Track-Etched Membranes for Catalytic Decomposition of Nitrophenols and Removal of As(III).

One of the promising applications of nanomaterials is to use them as catalysts and sorbents to remove toxic pollutants such as nitroaromatic compounds and heavy metal ions for environmental protection. This work reports the synthesis of Cu/CuO-deposited composite track-etched membranes through low-temperature annealing and their application in catalysis and sorption. The synthesized Cu/CuO/poly(ethylene terephthalate) (PET) composites presented efficient catalytic activity with high conversion yield in the reduction of nitro aryl compounds to their corresponding amino derivatives. It has been found that increasing the time of annealing raises the ratio of the copper(II) oxide (CuO) tenorite phase in the structure, which leads to a significant increase in the catalytic activity of the composites. The samples presented maximum catalytic activity after 5 h of annealing, where the ratio of CuO phase and the degree of crystallinity were 64.3% and 62.7%, respectively. The catalytic activity of pristine and annealed composites was tested in the reduction of 4-nitroaniline and was shown to remain practically unchanged for five consecutive test cycles. Composites annealed at 140 °C were also tested for their capacity to absorb arsenic(III) ions in cross-flow mode. It was observed that the sorption capacity of composite membranes increased by 48.7% compared to the pristine sample and reached its maximum after 10 h of annealing, then gradually decreased by 24% with further annealing.

Hierarchically porous S-scheme CdS/UiO-66 photocatalyst for efficient 4-nitroaniline reduction

Unveiling the pore-size performance of metal organic frameworks (MOFs) is imperative for controllable design of sophisticated catalysts. Herein, UiO-66 with distinct macropores and mesopores were intentionally created and served as substrates to create advanced CdS/UiO-66 catalysts. The pore size impacted the spatial distribution of CdS nanoparticles (NPs): CdS tended to deposit on the external surface of mesoporous UiO-66, but spontaneously penetrated into the large cavity of macroporous UiO-66 nanocage. Normalized to unit amount of CdS, the photocatalytic reaction constant of macroporous CdS/UiO-66 over 4-nitroaniline reduction was ∼3 folds of that of mesoporous counterpart, and outperformed many other reported state-of-art CdS-based catalysts. A confinement effect of CdS NPs within UiO-66 cage could respond for its high activity, which could shorten the electron-transport distance of NPs-MOFs-reactant, and protect the active CdS NPs from photocorrosion. The finding here provides a straightforward paradigm and mechanism to rationally fabricate advance NPs/MOFs for diverse applications.

Catalytic activity of nickel(II) oxide nanoparticle-[C60]fullerene nanowhisker composite for reduction of 4-nitroaniline

Nickel(II) oxide nanoparticles were prepared using the sol-gel method. Subsequently, a nickel(II) oxide nanoparticle-[C60]fullerene nanowhisker composite was synthesized using the nickel oxide(II) nanoparticle dispersion, C60-saturated toluene, and isopropyl alcohol via the liquid-liquid interfacial precipitation (LLIP) method. The resulting composite was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and transmission electron microscopy (TEM). The catalytic activity of the nickel(II) oxide nanoparticle-[C60] fullerene nanowhisker composite for 4-nitroaniline reduction was evaluated with ultraviolet-visible (UV-vis) spectroscopy. The kinetic study confirmed that the reduction of 4-nitroaniline using the hybrid nanocomposite followed a pseudo-first order reaction.

Investigation of the band gap energy shift and photocatalytic properties of Bi3+-doped ceria

A series of Bi3+-doped CeO2 photocatalysts have been prepared using simple coprecipitation method. The effect of Bi3+ doping on structural surface morphology and optical properties of the prepared photocatalysts was characterized using diffuse reflectance spectroscopy (DRS), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) for determination of the specific surface area and porosity. All prepared photocatalysts exhibit fluorite-type structure with no phase change up to 10 mol percent Bi3+ doping when calcinated at 973 K for 1 h. A red shift in optical band gap measurements was observed with increasing Bi3+ ion percent doping. Photocatalytic performance of prepared photocatalysts were examined using visible-light-induced photocatalytic reduction of 4-nitroaniline to p-phenylenediamine. The highest photocatalytic efficiency was achieved using CeO2 photocatalyst with 5 mol percent Bi3+ doping.

Investigation of the band gap and photocatalytic properties of CeO2/rGO composites

CeO2 and CeO2/rGO composites photocatalysts has been prepared using simple coprecipitation method. The effect of rGO on structural surface morphology and optical properties of the prepared photocatalysts was characterized using diffuse reflectance spectroscopy (DRS), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller for determination of the specific surface area/ porosity (BET). All prepared photocatalysts exhibits fluorite-type structure with no phase change up to 5 wt percent rGO when calcinated at 700 °C for 1 h. A red shift in optical band gap measurements was observed with increasing rGO percent. Photocatalytic performance of prepared photocatalysts were examined using visible-light-induced photocatalytic reduction of 4-nitroaniline to p-phenylenediamine. The highest photocatalytic efficiency was achieved using CeO2 photocatalyst with 5 wt percent rGO.

Uniformly distributed ruthenium nanocrystals as highly efficient peroxidase for hydrogen peroxide colorimetric detection and nitroreductase for 4-nitroaniline reduction.

Here, we report highly dispersed small ruthenium nanoparticles (NPs) anchored onto a porous carbon (Ru/PC) with a clean catalytic surface and explore their excellent peroxidase-like activity for 3,3',5,5'-tetramethylbenzidine oxidation mediated by H2O2, which allows sensitive colorimetric detection of H2O2 with a low detection limit of 3.8 μM. Moreover, it is also found that the Ru/PC has a high nitroreductase-like activity for 4-nitroaniline reduction triggered by NaBH4.

Heterogeneous catalytic reduction of 4-nitroaniline by RGO-Ni nanocomposite for water resource management

Reduced graphene oxide (RGO)–Nickel nanocomposite was synthesized by the hydrothermal process and this work shows the catalytic efficiency of nickel nanoparticles (Ni NPs) stabilized by reduced graphene oxide (RGO) for reduction of toxic organic molecules into nontoxic moiety. Characterization by X-ray diffraction shows the ordered structure of Ni NPs on RGO surface and transmission electron microscopy indicates that the use of RGO as a supporting material reduces the aggregation of metallic Ni NPs resulting an enhancement in the reactivity. Approximately 4–5 nm Ni NPs are finely distributed on RGO surface. The UV–Visible study confirms the formation of nickel NPs and the catalytic experiments show that the degradation capability of organic dye is increased than that in absence of any catalyst, RGO and Ni NPs separately. A catalytic mechanism for the removal of 4-nitroaniline (4-NA) by RGO–Ni nanocomposite was proposed which involves catalytic reduction. This nanocomposite shows ferromagnetism behavior at room temperature.

Formation of Silver Rhombic Dodecahedra, Octahedra, and Cubes through Pseudomorphic Conversion of Ag2O Crystals with Nitroarene Reduction Activity.

Using ethanol as a co-solvent, relatively small-sized Ag2O octahedra (∼645 nm in opposite corner distance) and rhombic dodecahedra (∼540 and 655 nm in opposite face distance) were synthesized in aqueous solutions. Ag2O cubes synthesized in an aqueous solution have an edge length of ∼425 nm. Band gaps of these crystals have been obtained, revealing the presence of facet-dependent light absorption properties. The Ag2O rhombic dodecahedra, octahedra, and cubes were treated with ammonia borane in ethanol at 50 °C for just 10 min to pseudomorphically convert to Ag polyhedra of the corresponding morphologies. Transmission electron microscopy characterization confirms that the Ag cubes, octahedra, and rhombic dodecahedra are bound by the {100}, {111}, and {110} faces, respectively. The Ag rhombic dodecahedra, available for the first time, showed more superior catalytic activity toward 4-nitroaniline reduction at 50 °C than Ag octahedra and cubes, and gave 100% product yield after 1 h of reaction. This work demonstrates the value of forming Ag rhombic dodecahedra, exposing {110} surfaces that may be useful in other organic transformations.

Pd nanoparticles stabilized on the Schiff base-modified boehmite: Catalytic role in Suzuki coupling reaction and reduction of nitroarenes

Palladium nanoparticles (Pd NPs) were decorated on Schiff base-modified boehmite (Sch-boehmite) particles via a simple method without deploying any additional reducing agents and their structure was confirmed by different characterization methods. The ensuing Pd NPs@Sch-boehmite was evaluated as a retrievable catalyst for multiple cycles in Suzuki cross-coupling reactions with extensive substrate tolerance to produce biaryls in high yields within 6 min, and the reduction of 2-nitroaniline (2-NA) and 4-nitrophenol (4-NP) at room temperature in 3–4 min, respectively. Moreover, Pd NPs@Sch-boehmite catalyst could be conveniently recovered and reused multiple times.

Synthesis of silver nanoparticles assisted by chitosan and its application to catalyze the reduction of 4-nitroaniline

This paper reports on the fabrication of material comprised of chitosan stabilized silver nanoparticles on the carbon paste and its electro-catalytic reduction toward 4-nitroaniline. The synthesized material was obtained when AgNO3 was mixed with chitosan as a stabilizing agent and NaBH4 as a reducing agent. The developed Chitosan-AgNPs has been confirmed using UV–Vis spectroscopy, X-Ray diffraction analysis, scanning electron microscopy (SEM) and infrared spectroscopy. The synthesized chitosan-Ag NPs exhibit particle size around 51 nm. To build a voltammetric sensor (Chitosan-Ag NPs/CPE), a carbon paste electrode has immersed in the liquid suspension of chitosan-Ag NPs, thus, it could be employed for electro-catalytic reduction of 4-NA in 0.1 M Britton-Robinson buffer solution (B-R, pH 2). Therefore, the reduction over-potential of 4-NA shifted from −752.26 mV at CPE to −304 mV at chitosan-Ag NPs/CPE, and then showing a surface controlled process with the catalytic rate constant (Kcat) of 0.125 × 10−3 M−1 s−1 and a coefficient of diffusion (D) of 2.20 × 10−6 cm2 s−1 with an enhanced current response. Under optimized conditions, the electro-catalytic reduction peak current of 4-NA increased linearly with increasing of 4-NA concentration over the range of 1 μM to 0.5 mM (R2 = 0.9866) with a detection limit of 0.86 μM (3 × Sb/P).

Copper nanoparticles embedded chitosan for efficient detection and reduction of nitroaniline.

In this study, we proficiently designed metal nanoparticles embedded in chitosan biopolymeric matrices, which have the ability to be employed simultaneously for the recognition and complete reduction of 4-nitroaniline. Copper nanoparticles embedded chitosan (CuNPs-CH) were coated on glassy carbon electrode to design an efficient electrochemical sensor for 4-nitroaniline. The sensing ability of CuNPs-CH modified electrode toward 4-nitroaniline was assessed by cyclic voltammetry, amperometry and chronoamperometry at working potential of -0.76 V and pH 7.0, while the complete reduction of 4-nitroaniline was analyzed by UV-visible spectrophotometer. The sensing features of CuNPs-CH modified electrode include a sensitivity of -8.166 μA mM-1 cm-2, and detection limit of 0.37 μM. The catalytic ability of CuNPs-CH for 4-nitroaniline reduction reaction was investigated. The results displayed that 4-nitroaniline completely transformed to diaminobenzene in short contact time with a rate constant of 7.51 × 10-3 s-1. The reduction aptitude of CuNPs-CH was also examined toward 4-nitrophenol and rhodamine B; however, the designed system was more efficient toward 4-nitroaniline. The developed approach offered a new methodology for simultaneous detection and reduction of 4-nitroaniline simply for environmental safety purposes.

Shape dependent catalytic activity of unsupported gold nanostructures for the fast reduction of 4-nitroaniline

A one step seed mediated strategy is adopted here for synthesizing spherical, dog bone and rod shaped gold nanoparticles. Usually noble metals decorated by supporting materials are used for chemical catalysis. Here, a variety of unsupported gold nanoparticles (spherical, dog bone and rod shaped) originating from the same growth procedure are used for the catalytic reduction of para-nitroaniline (4-NA). The product obtained, para-phenylenediamine, is an important material, especially in the field of dye industry. The reaction kinetic values were analyzed based on to the Langmuir–Hinshelwood (LH) mechanism. A comparison of the rate constants obtained for gold nanoparticles of different shapes with almost similar volume pointy that gold nanorods are superior to that of spherical and dog bone like nanoparticles. The turnover frequency obtained here is high compared to other reported results and is found to be sensitive to the shape of the nanoparticles.

Polyurethane/Keratin/AgNPs nanofibrous mats as catalyst support for 4-nitroaniline reduction

Silver nanoparticles loaded polyurethane/keratin nanofibrous mats (PU/Keratin/AgNPs) were fabricated via electrospinning, silver ion immobilization, followed by in situ reduction. The size and loading amount of AgNPs were regulated by varying the solution concentration of silver ions. The mats were characterized with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The PU/Keratin/AgNPs mats were exploited as catalyst support to reduce 4-nitroaniline (4-NA) in presence of borohydride, and their excellent catalytic activity showed the loading dependent feature. Moreover, these mats exhibited a stable catalytic activity up to 5 cycles.

Catalytic Activities of Mono- and Bimetallic (Gold/Silver) Nanoshell-Coated Gold Nanocubes toward Catalytic Reduction of Nitroaromatics.

A new class of core-shell metallic nanostructures with tunable near-surface composition and surface morphology with excellent catalytic activity is reported. Very thin shells of metal nanoassemblies such as monolayer (Ag and Au), bilayer of Ag or Au, and AgAu alloy layer with controlled size and morphology were deposited onto a gold nanocube (AuNC) core. UV-vis absorption spectroscopy and high-resolution transmission electron microscopy analyses along with selected-area electron diffraction, energy dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometer, and X-ray diffraction techniques were used to characterize the prepared core-shell nanocubes. High-angle annular dark field scanning transmission electron microscopy-energy dispersive X-ray spectroscopy mapping images were recorded for the bilayer shell and alloy layer shell in the core-shell nanostructures. Reduction of 4-nitroaniline in the presence of sodium borohydride was chosen to validate the catalytic activity of the prepared core-shell metal nanocubes. Interestingly, the AgAu alloy shell layer over the AuNC (AuNC1@Ag0.25Au0.25) showed excellent catalytic activity compared with the pristine AuNC and monolayer and bilayer core-shell nanostructures.

Investigation of voltammetric behavior of 4-nitroaniline based on electrodeposition of silver particles onto graphite electrode

Electrochemical modification of carbon-paste electrode (CPEs) by silver particles and its applicability for electroanalytical determination of 4-nitroaniline (4-NA) were reported in this study. Electrochemical surface modification was performed by cyclic voltammetry within the range from 600 to − 400 mV in solution containing 0.5 mmol L−1 AgNO3 dissolved in 0.1 mol L−1 of KNO3 at the scan rate of 10 mV s−1 by applying 1.5 cycles (six segments). Silver particles deposited onto surface of carbon-paste electrode (Ag-CPE) were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The proposed catalyst exhibits remarkably an electro-catalytic performance toward 4-nitroaniline reduction. The catalytic peak current obtained by differential pulse voltammetry (DPV) was linearly dependent on the 4-NA concentration over the range of 8.0 × 10−8 to 1.0 × 10−4 mol L−1 with a detection limit of 4.18 × 10−8 mol L−1. The proposed sensor was successfully applied for 4-nitroaniline determination in drinking water samples.

Enhanced photocatalytic activity of CdS/SnS2 nanocomposite with highly-efficient charge transfer and visible light utilization for selective reduction of 4-nitroaniline

Photocatalytic reduction can be an effective and promising technology for the selective reduction of aromatic nitro organics. In this paper, a novel Z-scheme CdS/SnS2 photocatalyst was well-designed and fabricated via simple in-site reaction process containing thioacetamide as a sulfur sources and cubic CdSnO3 as template. The resulting CdS/SnS2 composite has well-constructed cubic nanostructure of strong adhesion between CdS and SnS2, presenting high absorption to visible light. Importantly, strong charge transfer between the contacting regions of CdS and SnS2 through the intermediate sulfur atoms combined with both metals was generated, which speeds up separation of photogenerated electron and hole. The advantageous combination of high light-harvesting and effective charge transfer is responsible for the excellent photocatalytic activity at the CdS/SnS2 heterointerface. Resultantly, the prepared CdS/SnS2 composites exhibit high conversion efficiency and selectivity on 4-nitroaniline (4-NA) reduction in the aqueous solution containing ammonium formate under visible light irradiation, which can reduce almost all 4-NA within 12 min. Trapping experiments and ESR analysis demonstrated that ammonium formate not only can effectively decrease recombination of photogenerated charge carriers but also react with holes to generate CO2− radicals possessing strong reduction ability. The 4-NA are effectively photo-reduced by the synergistic effect of electrons and CO2− radicals. According to the experimental results, a possible Z-scheme charge transfer mechanism was proposed. Besides, the photo-reduction of aromatic nitro organics possessed different para-groups (p-nitrophenol, nitrobenzene, and p-nitrobenzaldehyde) was also investigated. It is found that the electron-drawing group can decrease the electron density of its para-position nitryl, which quickens the nitro reduction.

Impregnation of silver in graphite carbon using solid reaction: Electrocatalysis and detection of 4-nitroaniline

In the present study, the proposed sensor was prepared by silver microparticles-impregnated carbon paste electrode (Ag-CPE) and used for electrocatalytic reduction of 4-nitroaniline (4-NA). The effect of the amount of silver into carbon paste on the peak potential shift was investigated. Electrochemical impedance spectroscopy (EIS) analyses were realized in the presence of [Fe(CN)6]3−/4− and KCl as a redox probe. The cell-electrolyte resistance (Rs), charge transfer resistance (Ret), and electron-transfer rate constant (kapp) were calculated for different modified electrode. The electrocatalysis of 4-nitroaniline by silver microparticles as a redox was studied in aqueous media at the surface of a carbon paste electrode using cyclic voltammetry (CV) and chronoamperometry methods. In addition to that, the Ag-CPE exhibits excellent electrocatalytic activity indicating that the modification with silver can greatly accelerate the electron transfer. The catalytic rate constant and diffusion coefficient for 4-nitroaniline were found to be 1.36 × 10−2 mol−1 L s−1 and 3.35 × 10−6 cm2 s−1 respectively.

Building a direct Z-scheme heterojunction photocatalyst by ZnIn2S4 nanosheets and TiO2 hollowspheres for highly-efficient artificial photosynthesis

Facing the requirement of modern industrial development, selective reduction of 4-nitroaniline (4-NA) into p-phenylenediamine (PPD) via a facile, economic and eco-friendly photocatalysis technique has attracted more and more attention in recent years. In this study, ZnIn2S4 (ZIS) nanosheets grew in-situ on the surface of TiO2 hollowspheres through a hydrothermal method and formed a direct Z-scheme heterojunction composite, which exhibited exceedingly better photocatalytic 4-NA reduction performance than bare ZIS and TiO2. Such enhancement was mainly attributed to the dissimilar dimensionalities, intimate contact, and matchable band edge positions between ZIS and TiO2 semiconductors. Moreover, the substantial mechanism for the photocatalytic reaction in the ZIS/TiO2 system was reasonably proposed. Inspired by recent applications of the Z-scheme heterostructured materials in solar energy conversion and artificial photosynthesis, this work would arouse an increasing interest in designing more Z-scheme photocatalyst systems with high efficiency and extensive applications.

Carbon quantum dots/Zn2+ ions doped-CdS nanowires with enhanced photocatalytic activity for reduction of 4-nitroaniline to p-phenylenediamine

It was widely accepted that pristine CdS showed weak photocatalytic activity for reduction of 4-nitroaniline (4-NA) to p-phenylenediamine (PPD) because of its poor photogenerated carriers separation and transfer efficiency. Yet the influence of conduction band (CB) and valence band (VB) redox potentials on its photocatalytic reduction reaction efficiency was often neglected, especially the VB potential. Considering the above facts, in this work, we design a highly efficient carbon quantum dots (CQDs)/Zn2+ ions doped-CdS nanowires (ZnCdS NWs) composite photocatalysts, where CQDs were acted as metal-free co-catalysts to promote the separation and transfer of photogenerated carriers and Zn2+ ions doping was used to adjust the redox of CdS NWs. As a result, under visible light irradiation, 4-NA could be completely converted to PPD with near 100% selectivity over the as-synthesized CQDs/ZnCdS NWs within 6 min in the presence of ammonium formate. It was found that Zn2+ ions doping increased VB potential of CdS rather than lowering its CB potential, which was responsible for its enhanced photocatalytic activity. The present strategy on the combination of co-catalyst and energy band engineering could open a new avenue to develop highly efficient visible-light-driven photocatalysts for green organic synthesis.