Green synthesis of silver nano-catalyst using ionic liquid and their photocatalytic application to the reduction of p-nitrophenol (original) (raw)
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Silver nanoparticles of various sizes were prepared at room temperature using silver nitrate as a precursor, various molar ratios of sodium citrate as a surfactant stabilizing material and sodium borohydride as a reducing agent. The morphology, distribution and sphericity of the particles were assessed in images from a transmission electron microscope (TEM). The sizes of the particles were calculated as being 9, 11 and 14 nm. The effects of the particles' sizes on the plasmon bands were confirmed by ultraviolet-visible spectra measurements. The prepared samples were applied in photo catalysis of 4-Nitrophenol (4-NP), and the rate constant was determined as 0.05 s −1 , 0.0015 s −1 and 0.00021 s −1 for particles of 9 nm, 11 nm and 14 nm, respectively. Due to their high surface energy, the smaller particle sizes were more active in the photo catalytic application.
Silver nanostructures (silver nanopaerticles e.g AgNPs and silver nanoplates e.g AgNPls) of various sizes and shapes were prepared using different reducing agents in ionic liquid media. The ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, which acts both as a cosolvent and a surfactant, was used to synthesize smaller and more ordered silver nanostructures. Spherical nanoparticles (silver NPs) were prepared using sodium borohydride as a reducing agent. On the other hand, plate-shaped silver nanostructures (silver NPls) were prepared using hydrazine hydrate as a reducing agent. The as-synthesized silver nanostructures were characterized by scanning electron microscopy, powder X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, and Brunauer-Emmett-Teller analysis. The resulting materials were applied for the photodegradation of methyl orange under visible light irradiation. Because of their large surface area, the silver NPs showed better photocatalytic activity compared with that of Ag NPls.
Direct synthesis of silver nanoparticles in ionic liquid
Journal of Nanoparticle Research, 2016
Silver nanoparticles were synthesized using block copolymer (Pluronic ® P123) spherical micelles as a template. In aqueous Ag + ions may be electrostatically complexed with the anionic surfactant or ionic liquids. The silver ions were reduced in situ by introducing sodium borohydride as a reducing agent. We found that the size of the silver nanoparticles was exclusively depends on the size of block copolymer micelles. Addition of ionic liquid (IL) (1-decyl-3-methyl imidazolium dodecyl sulphate (C 10 MimDs)) induced sphere-ribbon transition of Silver nanoparticles. The size of the nano ribbon can be tuned by controlling concentration of ionic liquid as well as reducing agents. The silver nanoparticles were observed to be extremely stable in solution suggesting that the modified IL molecules stabilized them. The nanoparticles were characterized by UV-Vis absorbance, dynamic light scattering (DLS) as well as Transmission electron microscope (TEM).
Synthesis of Small Silver Nanoparticles and Their Catalytic Activity in 4-NITROPHENOL Reduction
2013
This work is aimed at preparation of small silver nanoparticles (Ag NPs) with various sizes using two-step preparation method. The silver bromide nanoparticles were prepared in the first step and they were reduced to metal silver nanoparticles in the second step. Size of prepared silver nanoparticles was controlled by using of several modifiers. Two surfactants (SDS and Tween 80) and two natural polymers (casein and gelatin) were used. Sodium borohydride was used as a reducing agent due to its high reducing power allowing preparation of small AgNPs. The prepared Ag NPs were used as heterogeneous catalysts in a model reaction based on reduction of 4-Nitrophenol using sodium borohydride under alkaline conditions. The realized experiments showed that the used modifiers significantly influence the catalytic effect of the prepared Ag NPs.
An efficient and blistering reduction of 4-nitrophenol by green synthesized silver nanoparticles
SN Applied Sciences, 2019
The present work describes a clean, green and cost efficient approach for the synthesis of biogenic silver nanoparticles from the Psidium guajava leaf extract. The UV-Visible spectrum shows a sharp peak at 413 nm revealing the formation of silver nanoparticles (Ag NPs). The optical and morphological characterization confirms the formation of stable and mono disperse biogenic silver nanoparticles having average diameter in range of 20-30 nm. FTIR study confirms that the strong capping and reduction potential Psidium guajava leaf extract for the synthesis of Ag NPs. The synthesized Ag NPs shows the prodigious potential for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) within 8 min (ultra-high speed) with rate constant 0.159 min -1 . Kinetic study elucidate that the catalytic reduction follows the pseudo first order with R 2 value of 0.975.
Langmuir, 2013
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 NaBH 4 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 4aminophenol in the presence of NaBH 4. 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.
A new " seed mediated " strategy was designed and demonstrated for the higher loading of silver nanoparticles (Ag NPs) onto silica (SiO 2) to obtain a Ag NPs enriched SiO 2 (designated as Ag(E)–SiO 2) catalyst. Simplified two steps were utilized for the preparation of Ag(E)–SiO 2. In the first step, SiO 2 was functionalized with a negatively charged p-toluene sulfonic acid ion and embedded with a few Ag NPs(seed) and obtained as Ag(seed)–SiO 2 (p-TSA À). In the subsequent step, excessive Ag + ions were pre-concentrated onto the SiO 2 surface using the negative charges on the SiO 2 surface and reduced to Ag NPs. The pre-existing Ag NPs(seed) and pre-concentrated Ag + ions enabled the growth of a further layer of Ag NPs to obtain Ag(E)–SiO 2. Results from FTIR spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements clearly supported our strategy of simultaneous functionalization of SiO 2 and Ag(seed) formation through the first step. Detailed FESEM, TEM and XPS analysis revealed higher loading ($80 weight% (wt%)) of Ag NPs in Ag(E)–SiO 2 with a metallic valence state. The catalysts, Ag(seed)–SiO 2 (p-TSA À) and Ag(E)–SiO 2 , containing low Ag ($10 wt%) and higher Ag loading ($80 wt%) of Ag NPs, respectively, were tested for the reduction of toxic organic compounds such as 4-nitrophenol (4-NP) and methylene blue (MB). The Ag(E)–SiO 2 catalyst exhibited superior catalytic performance for 4-NP/MB reduction as compared to Ag(seed)–SiO 2 (p-TSA À) (conventional) as well as over several other Ag NPs supported catalysts reported in the literature. The enhanced catalytic performance of Ag(E)–SiO 2 for 4-NP and MB reduction suggests that our new strategy is promising for the preparation of efficient supported catalysts for water purification and related applications.