Activity For Reduction Of 4-nitrophenol Research Articles

Fabrication of hollow SiO2 and Au (core)–SiO2 (shell) nanostructures of different shapes by CdS template dissolution

Core–shell silica (SiO2) coated CdS nanorods (NR) and nanospheres (NS) were prepared (SiO2@CdS) by deposition of a Si–O–Si amorphous layer over the CdS surface through the hydrolysis of 3-mercaptopropyltrimethoxysilane and tetraethylorthosilicate. Nanoporous SiO2 matrix (NPSM), hollow SiO2 nanotubes (HSNT) and nanospheres (HSNS) useful for efficient adsorption and catalytic processes were prepared by chemical dissolution of CdS–NS (size: 9–10 nm) and CdS–NR (length: 116–128 nm and width: 6–11 nm) template from SiO2@CdS with 2 M HNO3. These SiO2 nanostructures were characterized by optical absorption, TEM, EDX, SAED and BET surface area analysis. TEM images revealed the fabrication of slightly distorted HSNS (size: 9–12 nm) and closed HSNT (length: 30–45 nm and diameter: 9–14 nm) of shorter dimensions than the CdS–NR template used. The BET surface area (112–134 m2 g−1) of NPSM and HSNS is found to be larger than the surface area (29–51 m2 g−1) of SiO2@CdS composites indicating hollow SiO2 morphology. Silica coated Au (SiO2@Au) composites formed by CdS dissolution from Au (2 wt%) deposited CdS–NR core-encapsulated into SiO2 shell (SiO2@Au–CdS–NR) exhibited a surface plasmon band at 550 nm and displayed high catalytic activity for 4-nitrophenol reduction by Au nanoparticle.

Green synthesis of silver nanoparticles by microorganism using organic pollutant: its antimicrobial and catalytic application

A novel approach for the green synthesis of silver nanoparticles (AgNPs) from aqueous solution of AgNO3 using culture supernatant of phenol degraded broth is reported in this work. The synthesis was observed within 10h, and AgNPs showed characteristic surface plasmon resonance around 410nm. Spherical nanoparticles of size less than 30nm were observed in transmission electron microscopy. X-ray diffraction pattern corresponding to 111, 200, 220, and 311 revealed the crystalline nature of the as-formed nanoparticles. It was found that the colloidal solution of AgNP suspensions exhibited excellent stability over a wide range of ionic strength, pH, and temperature. The effect of pH and ionic strength indicated that stabilization is due to electrostatic repulsion arising from the negative charge of the conjugate proteins. The AgNPs showed highly potent antimicrobial activity against Gram-positive, Gram-negative, and fungal microorganisms. The as-prepared AgNPs showed excellent catalytic activity in reduction of 4-nitrophenol to 4-aminophenol by NaBH4. By manufacturing magnetic alginate beads, the reusability of the AgNPs for the catalytic reaction has been demonstrated.

Biosynthesis of Au nanoparticles by Gymnocladus assamicus and its catalytic activity

Here we first report synthesis of gold (Au) nanoparticles by using Gymnocladus assamicus pod extract in aqueous medium. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis revealed that the Au nanoparticles predominantly formed planar structure and size range 4.5±0.23–22.5±1.24nm with 2θ values at 38.22°, 44.38°, 64.34°, 77.6° and 81.24° for lattice plane. The formation of pure metallic nanoparticles by reduction of the metal ions is possibly facilitated by reducing by phenolic acids like gallic acid, protocatechuic acid and kaempferol present in the G. assamicus pod extract. The Au solution shows potential catalytic activity in reduction of 4-nitrophenol to 4-aminophenol.

Facile Synthesis of Silver Nanoparticles Stabilized by Cationic Polynorbornenes and Their Catalytic Activity in 4-Nitrophenol Reduction

We report the facile one-pot single-phase syntheses of silver nanoparticles stabilized by norbornene type cationic polymers. Silver nanoparticles (AgNPs) stabilized by polyguanidino oxanorbornenes (PG) at 5 and 25 kDa and polyamino oxanorbornenes (PA) at 3 and 15 kDa have been synthesized by the reduction of silver ions with NaBH4 in aqueous solutions at ambient temperature. The four different silver nanoparticles have been characterized by UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and transmission electron microscopy (TEM) for their particle size distributions. Interestingly, PG stabilizes the silver nanoparticles better than PA as evident from our spectroscopic data. Furthermore, the AgNP-PG-5K (5K = 5 kDa) was found to serve as an effective catalyst for the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4. The reduction has a pseudo-first-order rate constant of 5.50 × 10(-3) s(-1) and an activity parameter of 1375 s(-1) g(-1), which is significantly higher than other systems reported in the literature.

Magnetite–Polypeptide Hybrid Materials Decorated with Gold Nanoparticles: Study of Their Catalytic Activity in 4-Nitrophenol Reduction

The preparation and physical–chemical characterization of gold decorated hybrid materials based on individual magnetite nanoparticles coated with a poly(γ-benzyl-l-glutamate) shell is here presented. First, the synthesis of hybrid magnetite–polypeptide is achieved using a mimetic adhesive molecule, dopamine, which is responsible of both, anchoring the magnetite and initiating the ring-opening polymerization of γ-benzyl-l-glutamate N-carboxyanhydride. Besides, and in a second step, new molecules of dopamine are introduced to provide functionality to the poly(γ-benzyl-l-glutamate) by simple aminolysis reaction, which allow the growth and the stabilization of gold nanoparticles inside the polypeptide shell. Finally, the potential of these nanoparticles as a magnetic catalyst is proved by the reduction reaction of nitrophenol to aminophenol. The 100% efficiency with the magnetic recovery after eight catalytic cycles is also demonstrated.

Preparation of Ag nanoparticle loaded mesoporous γ-alumina catalyst and its catalytic activity for reduction of 4-nitrophenol

In this paper, we report a simple chemical reduction method for synthesis of spherical Ag nanoparticles (average size ~ 7 nm) within mesoporous alumina matrix. Shape and size of the Ag nanoparticles and structure of the catalysts are investigated by using high resolution transmission electron microscopy, diffuse reflectance spectroscopy, N2 adsorption-desorption analysis, XRD and particle size analysis. The synthesized catalysts possess BET surface area of 281.6 m2/g and average pore size 6.38 nm. The synthesized Ag nanoparticle loaded mesoporous aluminas exhibit catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol.

A Facile Method for Preparation of Ag Nanoparticle Loaded MCM-41 and Study of Its Catalytic Activity for Reduction of 4-Nitrophenol

A Facile Method for Preparation of Ag Nanoparticle Loaded MCM-41 and Study of Its Catalytic Activity for Reduction of 4-Nitrophenol

In situ assembly of well-dispersed gold nanoparticles on electrospun silica nanotubes for catalytic reduction of 4-nitrophenol

The tubular nanocomposite with well-dispersed distribution of small gold nanoparticles (AuNPs) assembled on the inside and outside surfaces of silica nanotubes (SNTs) was fabricated by combining the single capillary electrospinning technique and an in situ reduction approach. The AuNPs/SNTs nanocomposite exhibited a good catalytic activity for reduction of 4-nitrophenol (4-NP).

Preparation of PAMAM− and PPI−Metal (Silver, Platinum, and Palladium) Nanocomposites and Their Catalytic Activities for Reduction of 4-Nitrophenol

Dendrimer-metal (silver, platinum, and palladium) nanocomposites are prepared in aqueous solutions containing poly(amidoamine) (PAMAM) dendrimers with surface amino groups (generations 3, 4, and 5) or poly(propyleneimine) (PPI) dendrimers with surface amino groups (generations 2, 3, and 4). The particle sizes of the metal nanoparticles obtained are almost independent of the generation as well as the concentration of the dendrimer for both the PAMAM and the PPI dendrimers; the average sizes of silver, platinum, and palladium nanoparticles are 5.6-7.5, 1.2-1.6, and 1.6-2.0 nm, respectively. It is suggested that the dendrimer-metal nanocomposites are formed by adsorbing the dendrimers on the metal nanoparticles. Studies of the reduction reaction of 4-nitrophenol by these nanocomposites show that the rate constants are very similar between PAMAM and PPI dendrimer-silver nanocomposites, whereas the rate constants for the PPI dendrimer-platinum and -palladium nanocomposites are greater than those for the corresponding PAMAM dendrimer nanocomposites. In addition, it is found that the rate constants for the reduction of 4-nitrophenol involving all the dendrimer-metal nanocomposites decrease with an increase in the dendrimer concentrations, and the catalytic activity of dendrimer-palladium nanocomposites is highest.

銀, 白金, ならびにパラジウムーデンドリマーナノコンポジットの調製と4-ニトロフェノールの還元に対する触媒活性

銀, 白金, ならびにパラジウムーデンドリマーナノコンポジットの調製と4-ニトロフェノールの還元に対する触媒活性

Comparison of PAMAM–Au and PPI–Au Nanocomposites and Their Catalytic Activity for Reduction of 4-Nitrophenol

Dendrimer–Au nanocomposites are prepared in aqueous solutions using poly(amidoammine)dendrimers (PAMAM) (generation 2, 3, and 5) and poly(propyleneimine)dendrimers (PPI)(generation 2, 3, and 4) by wet chemical NaBH 4 method. The Au nanoparticles thus obtained are 2–4 nm in diameter for both dendrimers and no generation dependence on the particle size is observed, whereas the generations of the dendrimers are increased as stabilization of Au–nanoparticles is achieved with lower dendrimer concentrations. Studies of the reduction reaction of 4-nitrophenol using these nanocomposites show that the rate constants for the PAMAM dendrimers (generations 2 and 3) are higher than those for the PPI dendrimers (generations 2 and 3), while a distinct difference in the rate constants is not seen for the PAMAM dendrimer (generation 5) or the PPI dendrimer (generation 4). In addition, the rate constants for the reduction of 4-nitrophenol involving all the dendrimers decrease with increases in dendrimer concentrations.