Size-selective synthesis of gold and platinum nanoparticles using novel thiol-functionalized ionic liquids

One-phase synthesis of gold and platinum nanoparticles using new thiol-functionalized ionic liquids (TFILs) is described for the first time. TFILs as stabilizing agents for gold and platinum nanoparticles were designed to have thiol groups on either the cation or anion and symmetrical or unsymmetrical positions only in the cation. Transmission electron microscopy, electron diffraction, and NMR were used for the characterization of nanoparticles. The metal nanoparticles formed using TFILs are crystalline structures with face-centered cubic packing arrangements and have small sizes (the average diameters are 3.5, 3.1, and 2.0 nm for Au and 3.2, 2.2, and 2.0 nm for Pt, respectively) and uniform distributions (the standard deviations are 0.7, 0.5, and 0.1 nm for Au and 1.1, 0.2, and 0.1 for Pt, respectively). It is believed that the nanoparticle size and distribution depend on the number and position of thiol groups in the IL.     

CO-assisted synthesis of finely size-controlled platinum nanoparticles

We present a surfactant-free approach for synthesizing size-dependent carbon supported Pt nanoparticles with mean sizes ranging from 4.8 to 1.7 nm by increasing ratios of CO/Ar. In this work, gas stabilizer exhibits the originality on the design of the supported size-controllable clusters.     

聚甲基丙烯酸钠辅助的金纳米颗粒的绿色制备

利用聚甲基丙烯酸钠的弱还原性和螯合作用,建立了一种水溶性金纳米颗粒合成的新方法.借助紫外可见分光光度计和透射电子显微镜对金纳米颗粒进行了表征,初步讨论了反应物浓度以及反应温度对产物的影响.     

Honey mediated green synthesis of silver nanoparticles

The paper reports the pH controlled synthesis of silver nanoparticles using honey as reducing and stabilizing agents. By adjusting the pH of the aqueous solution containing metal ions and honey, nanoparticles of various size could be obtained at room temperature. The nanoparticles were characterized by UV–visible, high-resolution TEM, XRD and FTIR measurements. The colloid obtained at a pH of 8.5 is found to consist of monodispersed and nearly spherical silver nanoparticles of size ～4 nm which is a significant advancement in biosynthesis. The high crystallinity with fcc phase is evidenced by clear lattice fringes in the high-resolution TEM image and peaks in the XRD pattern corresponding to (1 1 1), (2 0 0), (2 2 0), (3 1 1) and (2 2 2) planes. FTIR spectrum indicates that the nanoparticles are bound to protein through the carboxylate ion group.     

Size control synthesis of polymer-stabilized water-soluble platinum oxide nanoparticles

A series of narrowly distributed nanoparticles with different sizes of platinum oxide stabilized by polyvinylpyrrolidone (PVP) were synthesized by hydrolytic decomposition of platinum chloride. The as-synthesized nanoparticles were characterized by UV-vis, TEM, and XPS examination. Studies on the parameters influencing the size of the as-synthesized platinum oxide nanoparticles were carried out. The pH of the solution was demonstrated to be the main factor affecting the particle diameter. The particles size also decreased with the increasing molar ratio of stabilizer (PVP):PtCl(4). The influence of the concentration of sodium acetate on the rate of hydrolytic decomposition and the condensation reaction was studied. It was found that increasing the concentration of sodium acetate increased the rate of the condensation reaction nearly linearly.     

Methylviologen-mediated electrochemical synthesis of platinum nanoparticles in solution bulk

Platinum nanoparticles (PtNPs) are synthesized by methylviologen-mediated reduction of PtCl₂ at the potentials of the MV²⁺/MV^?+ redox couple in 40% aqueous DMF solution. In the absence of stabilizing agents and in the presence of a stabilizer in the form of spherical silica NPs or alkylamine-modified silica NPs (SiO₂-NHR), a part of PtNPs (14–18%) are deposited on the electrode while the rest of particles remain in solution to form coarse aggregates which precipitate. In the latter case, PtNPs are also partly bound to form individual ultrafine NPs (3 ± 2 nm) on the SiO₂-NHR surface. In the presence of polyvinylpyrrolidone (PVP), the generated PtNPs (18 ± 9 nm) neither aggregate nor deposit on the cathode but are completely stabilized in solution being encapsulated within the PVP matrix. The obtained PtNPs are characterized by the methods of dynamic light-scattering and electron microscopy.     

Stabilisation of water-soluble platinum nanoparticles by phosphonic acid derivatives

Sodium 2-(diphenylphosphino)ethyl phosphonate (1) was investigated as a stabilising agent for platinum nanoparticles (Pt-NPs) in aqueous solution. This phosphino phosphonate is known to stabilise rhodium nanoparticles (NPs) in water. Here we report that in the case of Pt-NPs this ligand is indirectly involved in the stabilisation mechanism and the actual stabilisation agent is the platinum complex Na(2)[Pt(1)(2)] (2). The reduction of platinum(II) salts in the presence of the phosphonates 1, 2, sodium 2-(diphenylphosphoryl)ethyl phosphonate (3) and 3,3,3-triphenylpropyl phosphonate (4) leads to stable platinum NPs with a remarkably narrow particle size distribution. These platinum NPs show high catalytic activity in the hydrogenation of 1-hexene and 1-chloro-3-nitrobenzene under biphasic as well as heterogeneous (supported on charcoal) conditions. The activity of the supported NPs was 30 times higher than the commercially available catalyst Pt(0) EnCat?. Furthermore, the single-crystal X-ray structures of (1)(MeOH)(2)(H(2)O)(2), (3)(H(2)O)(4), and (4)(2)(H(2)O)(17) have been determined.     

Facile green synthesis of gold nanoparticles using leaf extract of antidiabetic potent Cassia auriculata

A simple biological method for the synthesis of gold nanoparticles (AuNPs) using Cassia auriculata aqueous leaf extract has been carried out in the present study. The reduction of auric chloride led to the formation of AuNPs within 10 min at room temperature (28°C), suggesting a higher reaction rate than chemical methods involved in the synthesis. The size, shape and elemental analysis were carried out using X-ray diffraction, TEM, SEM-EDAX, FT-IR and visible absorption spectroscopy. Stable, triangular and spherical crystalline AuNPs with well-defined dimensions of average size of 15-25 nm were synthesized using C. auriculata. Effect of pH was also studied to check the stability of AuNPs. The main aim of the investigation is to synthesize AuNPs using antidiabetic potent medicinal plant. The stabilizing and reducing molecules of nanoparticles may promote anti-hyperglycemic if tested further.     

Rapid green synthesis of gold nanoparticles using Rosa hybrida petal extract at room temperature

This study reports a green method for the synthesis of gold nanoparticles using the aqueous extract of rose petals. The effects of gold salt concentration, extract concentration and extract quantity were investigated on nanoparticles synthesis. Gold nanoparticles were characterized with different techniques such as UV-vis spectroscopy, FT-IR spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, dynamic light scattering and transmission electron microscopy. Transmission electron microscopy experiments showed that these nanoparticles are formed with various shapes. FT-IR spectroscopy revealed that gold nanoparticles were functionalized with biomolecules that have primary amine group (-NH2), carbonyl group, -OH groups and other stabilizing functional groups. X-ray diffraction pattern showed high purity and face centered cubic structure of gold nanoparticles. Dynamic light scattering technique was used for particle size measurement, and it was found to be about 10nm. The rate of the reaction was high and it was completed within 5 min.     

Process intensification for synthesis of triglycerides of capric acid using green approaches

The present research focuses on intensified synthesis of tricaprin by esterification reaction between capric acid and glycerol catalysed by dry amberlyst-15 using ultrasonication approach. Effect of several reaction conditions like molar ratio, reaction temperature, and amberlyst-15 loading on the rate of conversion has been studied. Effect of ultrasonic conditions like duty cycle and irradiation time on the intensified synthesis is investigated. Recyclability of amberlyst-15 is studied to make process more economical. It is investigated that the optimum reaction conditions which gave maximum conversion of 95% were molar ratio of capric acid: glycerol as 3:5, reaction temperature 90 ​°C, 4% amberlyst −15 loading. It was further investigated that ultrasonic conditions which gave intensified synthesis were 70% duty cycle and irradiation time of 120 ​min. The ultrasonic assisted process was compared with conventional synthesis. Conventional synthesis gave 30% yield in 120 ​min and 82% in 18 ​h. Amberlyst-15 was successfully reused for 13 cycle without any change in the conversion (%) of reaction.     

Piperidone synthesis using amino acid: A promising scope for green chemistry

Piperidone is a family of organic chemicals characterized by a 6-carbon ring substituted with nitrogen and a double-bonded oxygen atom. Piperidones are named by the location of the nitrogen or amine group on the ring. It differs from piperidine by the presence of oxygen molecule (from ketone). It is used in pharmaceutical companies and chemical manufacturers as intermediates having anti microbial activity. It is usually synthesized using ammonia both in laboratory and industry. In present study, amino acid namely aspartic acid is used instead of ammonia. The amino acid incorporated piperidones is purified and analyzed using NMR spectroscopy. It has antimicrobial activity against Pseudomonas aeruginosa and Salmonella aboni.     

Controlled synthesis of highly dispersed platinum nanoparticles in ordered mesoporous carbons

A novel route has been developed to fabricate ordered carbon mesoporous materials with well-dispersed, highly stable Pt nanoparticles of ca. 2-3 nm on the pore walls using platinum acetylacetonate as the co-feeding carbon and Pt precursor.     

Silver nanoparticles: green synthesis and their antimicrobial activities

This review presents an overview of silver nanoparticles (Ag NPs) preparation by green synthesis approaches that have advantages over conventional methods involving chemical agents associated with environmental toxicity. Green synthetic methods include mixed-valence polyoxometallates, polysaccharide, Tollens, irradiation, and biological. The mixed-valence polyoxometallates method was carried out in water, an environmentally-friendly solvent. Solutions of AgNO(3) containing glucose and starch in water gave starch-protected Ag NPs, which could be integrated into medical applications. Tollens process involves the reduction of Ag(NH(3))(2)(+) by saccharides forming Ag NP films with particle sizes from 50-200 nm, Ag hydrosols with particles in the order of 20-50 nm, and Ag colloid particles of different shapes. The reduction of Ag(NH(3))(2)(+) by HTAB (n-hexadecyltrimethylammonium bromide) gave Ag NPs of different morphologies: cubes, triangles, wires, and aligned wires. Ag NPs synthesis by irradiation of Ag(+) ions does not involve a reducing agent and is an appealing procedure. Eco-friendly bio-organisms in plant extracts contain proteins, which act as both reducing and capping agents forming stable and shape-controlled Ag NPs. The synthetic procedures of polymer-Ag and TiO(2)-Ag NPs are also given. Both Ag NPs and Ag NPs modified by surfactants or polymers showed high antimicrobial activity against gram-positive and gram-negative bacteria. The mechanism of the Ag NP bactericidal activity is discussed in terms of Ag NP interaction with the cell membranes of bacteria. Silver-containing filters are shown to have antibacterial properties in water and air purification. Finally, human and environmental implications of Ag NPs to the ecology of aquatic environment are briefly discussed.     

Green synthesis of silver nanoparticles using green alga (Chlorella vulgaris) and its application for synthesis of quinolines derivatives

Nanoparticles have been used century ago but have regained their importance in recent years being simple, ecofriendly, pollutant free, nontoxic, low-cost approach, and due good atom economy. In this report, we have demonstrated the synthesis of silver nanoparticles using green algae (Chlorella vulgaris) which in turn was used for synthesis of biologically important quinolines. Algal extract was prepared and treated with silver nitrate solution for the synthesis of silver nanoparticles. Synthesized nanoparticles were characterized with the help of analytical tools like UV, FTIR, X-ray, and SEM and used as a catalyst for the synthesis of quinolines.     

Completely "green" synthesis and stabilization of metal nanoparticles

In the present Communication, a completely "green" synthetic method for producing silver nanoparticles is introduced. The process is simple, environmentally benign, and quite efficient. By gentle heating of an aqueous starch solution containing silver nitrate and glucose, we produce relatively monodisperse, starched silver nanoparticles. beta-d-Glucose serves as the green reducing agent, while starch serves as the stabilization agent.     

Green synthesis of platinum nanoparticles using Atriplex halimus leaves for potential antimicrobial,antioxidant, and catalytic applications

Herein, green platinum nanoparticles (PtNPs) were synthesized using an aqueous extract of Atriplex halimus leaves as a reductant. Atriplex platinum nanoparticles (At-PtNPs) were stable for up to three months. At-PtNPs were characterized by several techniques including UV–Visible spectroscopy, Fourier Transform Infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), Energy Dispersive X-ray spectroscopy (EDX), EDX elemental mapping, High-resolution Transmission electron microscope (HRTEM), Selected Area Electron Diffraction (SAED), and X-ray Photoelectron Spectroscopy (XPS) and Zeta measurements. At-PtNPs were black-colored and mainly spherical with a plasmon peak at 295 nm with ultra-small particle size (1–3 nm) and high surface charge (?25.4 mV). At-PtNPs were verified as a superb catalyst as they were able to catalytically degrade MB dye. At-PtNPs exhibited a high antibacterial efficiency against gram-negative bacteria. At-PtNPs were proved as a highly efficient antioxidant agent. Thus, the attained results offer a promising route of the green synthesis of PtNPs using the aqueous extract of Atriplex halimus.     

Diffusion of platinum ions and platinum nanoparticles during photoreduction processes using the transient grating method

The photoreduction process of PtCl(6)2- to Pt nanoparticles in poly(N-vinyl-2-pyrrolidone) solutions upon UV light irradiation was investigated by monitoring the change in the diffusion coefficient (D). The D values of chemical species during UV irradiation was measured by the laser-induced transient grating (TG) method. The TG signal of the PtCl(6)2- solution before UV irradiation was composed of three kinds of contributions, the thermal grating, the species grating due to the creation of PtCl4(2-), and the species grating due to the depletions of PtCl6(2-). Upon UV irradiation of the solution, the species grating signal due to PtCl6(2-) diminished and then the TG signal of Pt nanoparticles gradually appeared. This result indicates that the gradual clustering of Pt0 atoms into Pt nanoparticles occurs after all PtCl(6)2- ions are photochemically reduced to PtCl(4)2- and subsequently transformed to Pt0 atoms with a short delay. With increasing time of the UV irradiation, the TG signal intensity increased, while D of the Pt nanoparticles did not change. This suggests that the number of Pt nanoparticles increases, but the size of the Pt nanoparticles with the polymer layer is unchanged, in the course of the UV irradiation.