自下而上法制备金-介孔二氧化硅复合纳米管用作还原4-硝基苯酚的催化剂

采用自下而上方法制备了金-介孔二氧化硅复合纳米管,其中金纳米粒子作为催化剂嵌在介孔二氧化硅纳米管管壁内侧。金纳米颗粒的团聚、脱落和晶粒尺寸生长都可以被有效限制,而且催化剂负载量和尺寸大小均可实现简单控制。管壁中的介孔孔道、纳米管末端开口以及一维中空管道可以协同促进反应物扩散,从而提高4-硝基苯酚还原反应活性。循环实验证明这种复合纳米管催化剂具有良好的可重复使用性,而且在反应过程中未出现金纳米粒子脱落或团聚现象。     

Novel Ag2S nanoparticles on reduced graphene oxide sheets as a super-efficient catalyst for the reduction of 4-nitrophenol

Here,Ag_2S nanoparticles on reduced graphene oxide(Ag_2S NPs/RGO) nanocomposites with relatively good distribution are synthesized for the first time by conversing Ag NPs/RGO to Ag_2S NPs/RGO via a facile hydrothermal sulfurization method.As an noval catalyst for the reduction of 4-nitrophenol(4-NP),it only takes 5 min for Ag_2S NPs/RGO to reduce 98% of 4-NP,and the rate constant of the composites is almost 13 times higher than that of Ag NPs/RGO composites.The high catalytic activity of Ag_2S NPs/RGO can be attributed to the following three reasons:(1) Like metal complex catalysts,the Ag_2S NPs is also rich with metal center Ag(δ~+),with pendant base S(δ) close to it,and thus the Ag and basic S function as the electron-acceptor and proton-acceptor centers,respectively,which facilitates the catalyst reaction;(2)RGO features the high adsorption ability toward 4-NP which provides a high concentration of 4-NP near the Ag_2S NPs;and(3) electron transfer from RGO to Ag_2S NPs,facilitating the uptake of electrons by 4-NP molecules.     

Palladium supported on hydrotalcite as a catalyst for the Suzuki cross-coupling reaction

The efficiency of various palladium salts as catalysts in the Suzuki cross-coupling reaction, and the influence of the base and temperature used on its conversion, were studied. The use of PdCl₂ supported on hydrotalcite as catalyst in the presence of potassium carbonate as base was found to provide the best results. Reaction temperatures above 90 °C ensured conversion levels on a par with those for many homogeneous catalysts.     

Reduction of 4-nitrophenol catalyzed by nitroreductase

The reduction of 4-nitrophenol catalyzed by nitroreductase in the presence of NADH was investigated in this paper.4-Amino- phenol and 4-bydroxylamino-phenol were found in the reductive products.The relationship between reaction time and the reductive ratio were studied.The similar reducing ratios of 4-nitrophenol were obtained under aerobic and anaerobic conditions.The results indicated that an oxygen-insensitive reaction was proceeded in the reduction of 4-nitrophenol and nitroreductase was an oxygen- insensitive enzyme.The reductive products of 4-nitrophenol were determined by HPLC and MS.     

Single-walled carbon nanohorn as new solid-phase extraction adsorbent for determination of 4-nitrophenol in water sample

Single-walled carbon nanohorn (SWCNH) was developed as new adsorbent for solid-phase extraction using 4-nitrophenol as representative. The unique exoteric structures and high surface area of SWCNH allow extracting a large amount of 4-nitrophenol over a short time. Highly sensitive determination of 4-nitrophenol was achieved by linear sweep voltammetry after only 120 s extraction. The calibration plot for 4-nitrophenol determination is linear in the range of 5.0 × 10⁻⁸ M-1.0 × 10⁻⁵ M under optimum conditions. The detection limit is 1.1 × 10⁻⁸ M. The proposed method was successfully employed to determine 4-nitrophenol in lake water samples, and the recoveries of the spiked 4-nitrophenol were excellent (92-106%).     

Etching graphitic carbon nitride by acid for enhanced photocatalytic activity toward degradation of 4-nitrophenol

Graphitic carbon nitride （g-C3N4） with high photocatalytic activity toward degradation of 4-nitrophenol under visible light irradiation was prepared by HCI etching followed by ammonia neutralization. The structure, morphology, surface area, and photocatalytic properties of the prepared samples were studied. After treatment, the size of the g-C3N4 decreased from several micrometers to several hundred nanometers, and the specific area of the g-C3N4 increased from 11.5 m2/g to 115 m2/g. Meanwhile, the photocatalytic activity of g-C3N4 was significantly improved after treatment toward degradation of 4- nitrophenol under visible light irradiation. The degradation rate constant of the small particle g-C3N4 is 5.7 times of that of bulk g-C3N4, which makes it a promising visible light photocatalyst for future applications for water treatment and environmental remediation.     

One-pot green synthesis of Prussian blue nanocubes decorated reduced graphene oxide using mushroom extract for efficient 4-nitrophenol reduction

One-pot green approach to the synthesis of Prussian blue nanocubes/reduced graphene oxide (PBNCs/RGO) nanocomposite had been attempted. It was based on the extract of mushroom with K₃[Fe(CN)₆] and graphene oxide (GO) as precursors, where the reduction of GO and the deposition of PBNCs occurred simultaneously. The obtained nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and electrochemical techniques. With the introduction of β-cyclodextrin (β-CD), the β-CD/PBNCs/RGO system showed linear behavior in the range from 0.01 to 700 μM for 4-nitrophenol with a low detection limit of 2.34 nM (S/N = 3).     

Palladium nanoparticles supported on poly (N-vinylpyrrolidone)-grafted silica as new recyclable catalyst for Heck cross-coupling reactions

Novel catalytic system based on palladium nanoparticles supported on poly (N-vinylpyrrolidone) (PVP) grafted silica was prepared. Aminopropylsilica was reacted with acryloyl chloride to form acrylamidopropylsilica, and onto this functionalized silica vinylpyrrolidone monomer was polymerized by free-radical polymerization. The complexation of PVP-grafted silica with PdCl₂ was carried out to obtain the heterogeneous catalytic system. X-ray diffraction (XRD) technique and transmission electron microscopy (TEM) image showed that palladium dispersed through the support in nanometer size. This catalytic system exhibited excellent activity in cross-coupling reactions of aryl iodides, bromides and also chlorides with olefinic compounds in Heck-Mizoraki reactions in short reaction time and high yields. Elemental analysis of Pd by inductively coupled plasma (ICP) technique and hot filtration test showed low leaching of the metal into solution from the supported catalyst. The catalyst can be reused several times in repeating Heck reaction cycles without considerable loss in its activity.     

A facile approach for synthesizing molecularly imprinted graphene for ultrasensitive and selective electrochemical detecting 4-nitrophenol

In this work, a novel and convenient strategy was developed to prepare molecularly imprinted polymers (MIPs) on the surface of graphene sheet. In this route, vinyl group functionalized graphene (GR/NVC) was first prepared by immobilizing 4-vinylcarbazole onto the surface of graphene via π–π interaction. The subsequent grafting copolymerization of methacrylic acid and ethylene glycol dimethacrylate in the presence of 4-nitrophenol (4-NP, template molecule) was carried out at GR/NVC surface, leading to the formation of GR/MIPs composite. The GR/MIPs composite was characterized by FTIR, fluorescence, TGA, SEM and AFM, and was used to fabricate electrochemical sensor for the detection of 4-NP. The electrochemical behavior of GR/MIPs sensor for 4-NP was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The effects of the preparation conditions, such as concentration of the NVC and template, the solution pH, and incubation time, were also optimized. Under optimized conditions, the DPV current response of GR/MIPs sensor was nearly 12 times than that of the GR/NIPs sensor. It also should be noted that as compared to traditional MIP, shorter response time and much higher current response were demonstrated. In addition, the GR/MIPs sensor could recognize 4-NP from its structural analogs, indicating the excellent selectivity of the GR/MIPs sensor. The peak current is linearly proportional to the concentration of 4-NP ranging from 0.01 μM to 100 μM and 200 μM to 1000 μM with a significantly low detection limit of 5 nM, a wider response range and lower detection limits as compared to most of the previously reported electrochemical sensors for 4-NP. Furthermore, the GR/MIPs sensor exhibits good stability with adequate reproducibility and has been successfully used to determine 4-NP in water samples.     

Oxygen vacancy rich tungsten oxide with nitrogen doped mesoporous carbon as matrix for overall water splitting and 4-nitrophenol reductive removal

A nitrogen doped mesoporous carbon matrix supported oxygen vacancies rich tungsten oxide composite material, WO_3-x@NC (1 > x > 0), has been fabricated successfully with chitosan and H₃PW₁₂O₄₀ as precursors through calcination. In this composite material, WO_3-x particles with the size about 10–15 nm disperse evenly in nitrogen doped mesoporous carbon matrix. WO_3-x@NC presents low overpotentials (η₁₀) of 61 and 306 mV to reach a current density of 10 mA/cm² for HER and OER in 1.0 M KOH, respectively. With WO_3-x@NC as both cathode and anode at the same time, an electrolyzer, WO_3-x@NC//WO_3-x@NC was constructed for overall water splitting, which only needs a cell voltage of 1.60 V to achieve a current of 10 mA/cm². During this process, WO_3-x@NC//WO_3-x@NC exhibits remarkable stability in 48 h. Moreover, besides HER and OER, WO_3-x@NC also shows striking catalytic activity for reductive conversion of 4-nitrophenol to 4-aminophenol. Oxygen vacancies from WO_3-x and good electron transportation property of nitrogen doped carbon matrix play important roles in overall water electrocatalytic splitting and 4-nitrophenol reductive removal. We expect WO_3-x@NC will find its way as a new resource for hydrogen energy as well as a promising material in 4-nitrophenol removal from water.     

On-line selective solid-phase extraction of 4-nitrophenol with β-cyclodextrin bonded silica

The selective analysis of 4-nitrophenol (4-NP) from water samples using on-line solid-phase extraction (SPE) coupled to HPLC system was studied. The β-cyclodextrin bonded silica (CDS) was utilized as the selective sorbent. Using 100 ml of sample solution spiked with 4-nitrophenol and other six phenols (Ph) in double distilled water, the sorbent showed strong capacity in adsorbing 4-nitrophenol and the recovery was 104% with the detection limit of 0.017 μg/l. The selectivity was investigated by utilizing a washing step with acetonitrile after preconcentration and only 4-nitrophenol was detected with the recovery of 99%. Donghu lake (Wuhan, China) water sample was used to test the on-line SPE-HPLC system and 4-nitrophenol was selectively extracted with the recovery obtained as 90%.     

Voltammetric determination of 4-nitrophenol at a lithium tetracyanoethylenide (LiTCNE) modified glassy carbon electrode

The reduction of 4-nitrophenol (4-NP) has been carried out on a modified glassy carbon electrode using cyclic and differential pulse voltammetry (DPV). The sensor was prepared by modifying the electrode with lithium tetracyanoethylenide (LiTCNE) and poly-l-lysine (PLL) film. With this modified electrode 4-NP was reduced at −0.7 V versus SCE. The sensor presented better performance in 0.1 mol l⁻¹ acetate buffer at pH 4.0. The other experimental parameters, such as concentration of LiTCNE and PLL, pulse amplitude and scan rate were optimized. Under optimized operational conditions, a linear response range from 27 up to 23200 nmol l⁻¹ was obtained with a sensitivity of 3.057 nA l nmol⁻¹ cm⁻². The detection limit for 4-NP determination was 7.5 nmol l⁻¹. The proposed sensor presented good repeatability, evaluated in term of relative standard deviation (R.S.D.=4.4%) for n=10 and was applied for 4-NP determination in water samples. The average recovery for these samples was 103.0 (± 0.7)%.     

Palladium nanoparticles supported on mesoporous natural phosphate: An efficient recyclable catalyst for nitroarene reduction

We report the preparation of palladium nanoparticles supported on mesoporous natural phosphate (Pd@NP) using a wetness impregnation method. The prepared catalyst was characterized using various techniques. Furthermore, the reduction and preparation of the palladium nanoparticles was followed using UV–visible spectra. Based on the Scherrer equation, the crystallite size of the as‐synthesized palladium nanoparticles was 10.88 nm. The performance of the synthesized catalyst was investigated in the reduction of 4‐nitrophenol as a model substrate to 4‐aminophenol using NaBH₄ as a hydrogen source. Moreover, catalytic reduction of various nitroarenes was studied and monitored using UV–visible spectroscopy and gas chromatography. The Pd@NP catalyst showed a high activity for the selected reaction and could be recycled.     

(聚酰胺-胺树枝状大分子)-水杨醛席夫碱钯配合物的Heck反应催化性能研究(英文)

用元素分析、红外光谱、紫外光谱、荧光光谱和核磁等分析手段对合成出的1.0G树枝状大分子-水杨醛席夫碱钯配合物(PAMAMSAPd)进行了表征。用其作为催化剂,研究了碘代苯与丙烯酸在有机溶剂中的偶联反应。对于碘代苯与丙烯酸的偶联反应,最佳反应条件为:惰性气氛,10mmol PhI,nPhI∶nAA∶nEt3N=1∶1.5∶2.5,3.0×10-3g PAMAMSAPd, 4mL DMF和100°C的反应温度。在该条件下,产物肉桂酸的产率可达96.5%。该树枝状大分子配合物是一种无磷、高效和稳定的Heck反应催化剂。且该催化剂经简单的过滤、溶剂洗涤进行回收,重复使用3次,产率仍能达到90.2%。     

Computational and experimental study on the influence of the porogen on the selectivity of 4-nitrophenol molecularly imprinted polymers

In molecular imprinting the porogen plays a decisive role, as it not only affects the physical properties of the resulting polymer including its porosity, the specific surface area, and the swelling behavior, but also governs the stability of the prepolymerization complex, which in turn decisively determines the recognition properties of the resulting molecularly imprinted polymer (MIP).     

4-Amino-1,2,4-triazole Resin-supported Palladium Complex as Phosphine-free Catalyst for Suzuki Reaction in Aqueous Phase

<正>1 Introduction The Suzuki cross-coupling reaction is a powerful and versatile method for the generation of unsymme-trical biaryls from arylboronic acids and aryl halides in a single step[1―3].However,     

Palladium nanoparticles supported on gum arabic as a reusable catalyst for solvent-free Mizoroki-Heck reaction

Palladium nanoparticles (2–8 nm) supported on gum arabic has been prepared under green conditions in water. Gum arabic has been used as both support and reducing agent. These nanoparticles have been characterized by UV–Vis, XRD and EDX spectra as well as SEM and TEM images. The nanoparticles have been applied as the catalyst in Mizoroki-Heck reaction of different aryl halides (I, Br, Cl) with butyl acrylate in the presence of n-Pr₃N under solvent-free conditions at 140 °C. The reusability of the catalyst was also checked for five consecutive runs.     

Palladium incorporated on carbonaceous catalyst for Suzuki coupling reaction in water

A new palladium incorporated carbonaceous catalyst Pd@CCSO₃HNH₂ was synthesized by introducing palladium on glucose derived carbocatalyst. The catalyst was well characterized and was used for the Suzuki coupling of phenyl boronic acid with different aryl halides under aqueous conditions. This green methodology represents a ligand free, cost-effective and operationally convenient method for the synthesis of a variety of biaryl’s under the conditions that are tolerant for a broad range of functional groups with good to excellent yields. Moreover, the catalyst could be easily recycled and reused at least five times without any significant loss of its catalytic activity.