Nanoparticles For Catalytic Applications Research Articles

Structure and Stability of Core–Shell Cu–Pt Nanoparticles for Catalytic Applications

Structure and Stability of Core–Shell Cu–Pt Nanoparticles for Catalytic Applications

Pd Thickness Optimization on Silicate Sheets for Improving Catalytic Activity

AbstractMaximizing surface‐to‐body ratio demands ever smaller metallic palladium (Pd) nanoparticles for catalytic applications. The quest for miniaturization is now reaching the single‐atom limit. However, if the supported Pd is below a critical size, the Pd hybridization with the supporting material can detrimentally reduce the labile electrons that facilitate the catalytic reactions. Thus, the smallest attainable size, i.e., single‐atom Pd, may not offer the best efficiency. Here, it is demonstrated that Pd with at least six atomic layers (or thickness of ≈1 nm) on the silicate sheets, synthesized via the partial exfoliation of a layered silicate, exhibits a metallic‐like electronic property, yielding an excellent catalytic activity (e.g., turnover frequency) for dehydrogenating formic acid higher than both isotropic Pd nanoparticles and single‐atom Pd.

A copper(ii) complex containing pyridine-2-carbaldehyde and its direct binding onto ethylenediamine functionalized with Fe3O4@SiO2 nanoparticles for catalytic applications.

In the present study, a copper(ii) complex containing a pyridine-2-carbaldehyde ligand and its direct binding onto ethylenediamine functionalized with Fe3O4@SiO2 nanoparticles [Cu(ii)-Schiff base-(CH2)3-SiO2@Fe3O4] as a heterogeneous magnetic nanocatalyst can be easily prepared using a multi-step method. Next, the structural and magnetic properties of the synthesized nanoparticles were identified using Fourier-transform infrared spectroscopy (FT-IR), inductively coupled plasma (ICP), vibrating-sample magnetometry (VSM), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), PXRD (Powder X-ray diffraction), Brunauer-Emmett-Teller (BET), and energy-dispersive X-ray spectrometry (EDX) techniques. TEM images reveal that the average particle size distribution was found to be in the range of 45-55 nm with spherical shape. The PXRD analysis indicated that the crystallite size was found to be 35.2 nm. The synthesized nanocatalyst exhibited a very good catalytic ability in the synthesis reaction of pyran derivatives and 2-benzylidenemalononitrile derivatives. Product 2-amino-7,7-dimethyl-4-(4-nitrophenyl)-5-oxo-5,6,7,8-tetrahydrobenzo[b]pyran 4e was achieved in 97% yield with a TON of 129.3 and a TOF of 646.6 h-1 and product 2-(4-cyanobenzylidene)malononitrile 3j was achieved in 96% yield with a TON of 128 and a TOF of 984.6 h-1. In addition, the synthesized nanocatalyst was easily separated from the reaction mixture by a magnet and used 7 consecutive times without significant loss of catalytic activity. Also, leaching of copper metal from the synthesized nanocatalyst was very insignificant for this reaction.

Special Issue: Gold Nanoparticles for Catalytic Applications

Catalysis by gold nanoparticles is a topic of increasing interest [...]

A new sustainable approach towards preparation of sunlight active Ag/AgBr Janus nanoparticles using non-toxic surface active ionic liquid

A benign and easily implementable method for preparation of symmetry controlled Ag/AgBr nanoparticles for catalytic applications under sunlight or white light is presented.

Gold-doped ceria–lanthana solid solution: surfactant assisted preparation, nanostructural and catalytic properties

The effect of preparation methods on the formation of gold doped ceria–lanthana solid solution (Au-CLSS) nanoparticles (NPs) was studied. The nanoparticles were prepared by surfactant assisted precipitation methods viz., co-precipitation (CP) and deposition precipitation (DP) in the presence of cetyltrimethylammonium bromide (CTAB). The as prepared nanoparticles were characterized using BET, FESEM, EDS, Raman, TEM, XRD and UV–Vis. spectroscopic techniques to investigate the preferred method for the preparation of nanoparticles for catalytic applications. The cubic fluorite phase formation of nanoparticles was confirmed by XRD analysis and the average crystallite size was calculated to be around 7–10 nm. Surface area studies revealed that the NPs formed by CTAB assisted method have higher surface area. The morphology of NPs formed by both methods was flaky. Raman studies confirmed that the samples prepared by DP method generated increased oxygen vacancies than those prepared by CP method. In the present work, catalytic oxidation efficiency of the catalysts studied with toluene vapours showed maximum efficiency for Au-CLSS at low temperatures (450 K) as compared to undoped CLSS.

Sintering and Nanostability: The Thermodynamic Perspective

Sintering and nanostability (defined as the stability against sintering) are critical phenomena present in the processing and application of nanoparticles. With important implications in obtaining high‐quality dense ceramics with fine grains or in enabling high surface areas in nanoparticles for catalytic applications, the control of these interrelated phenomena has been the focuses of several studies. From a thermodynamic perspective, it is recognized that surface energy is a fundamental parameter in both cases, since it is the main driving force for sintering and also the reason that nanoparticles are thermodynamically unstable and have the tendency to coarsen at elevated temperatures. The role of grain‐boundary energies is less recognized as relevant, but is also connected to densification, grain growth, and nanoparticle stability. In this paper, we review the critical aspects of the role of interfacial energies in the microstructure evolution, in particular addressing them as parameters to allow better control in addition to more conventional kinetic parameters. The concept is based on the nonsingularity of interfacial energies in a given system, which varies with temperature, atmosphere, and most importantly, chemical composition—this last offering a method to induce particular microstructural evolutions. While the model assumes isotropic grain boundaries but consequences to anisotropy are also discussed. The paper presents examples of the role of dopants on interfacial energies, how this is quantitatively related to their segregation at the interfaces, and the impact in sintering and nanostability. Given the importance of interface energetics to these phenomena, we also present a short review on the current methods used to obtain reliable interface thermodynamic data.

Hollow Microporous Organic Capsules Loaded with Highly Dispersed Pt Nanoparticles for Catalytic Applications

Hollow microporous organic capsules embedded with small and monodisperse Pt nanoparticles (NPs) are designed and synthesized successfully. The transmission electron microscopy (TEM) results show that the materials with amine groups and a microporous structure act as a better support for obtaining highly dispersed Pt NPs in the micropores. After several successive catalytic reactions, the TEM and porous structure of the heterogeneous catalysts do not show any observable changes. The heterogeneous catalysts are highly stable in air and no decrease in activity is observed after the catalyst is exposed to air for several days. These heterogeneous catalysts exhibit excellent catalytic activity and recyclability potential, combined with mild conditions, and the possibility of using alcoholic reaction media for the nitroaromatic hydrogenation. image

ChemInform Abstract: Progress in Controlling the Size, Composition and Nanostructure of Supported Gold‐Palladium Nanoparticles for Catalytic Applications

AbstractReview: 77 refs.

Responsive Hybrid Polymeric/Metallic Nanoparticles for Catalytic Applications

AbstractThe aims of the current study were to synthesize new responsive polymeric microgels with embedded silver nanoparticles and then to employ these particles as catalyst for reduction reactions. To these ends, stimuli‐responsive microgels from PNIPAAm and the chitosan derivative were firstly synthesized by free radical precipitation polymerization. Then, silver nanoparticles were synthesized inside these microgel networks by in situ reduction of AgNO3. These microgels were temperature/pH sensitive with a phase transition temperature of 32–35 °C in water at pH = 3 and 8, respectively. The catalytic activity of the Ag nanoparticles for the reduction of 4‐nitrophenol can be tuned through the swelling or collapse of the responsive microgel network hosting the active nanoparticles. magnified image

Synthesis and characterisation of palladium nanoparticles for catalytic applications

We report a simple wet chemical method to synthesise palladium nanoparticles and test their performance as an activator for the electroless copper deposition reaction. A mixture of ethylene glycol and alkaline hydroxide ions is indispensable to initiate and catalyse the chemical reduction of palladium salt. The presence of a polyvinylpyrrolidone (PVP) in the solution mixture was also found to be essential and acted as a protective agent to isolate the nanoparticles and prevent the agglomeration. The crystallinity, size and morphology and structural features of the produced nanoparticles are investigated by powder X-ray diffraction (XRD), transmission electron microscopy (TEM). The performance of the nanoparticles as a catalyst for electroless deposition of copper on both silicon and epoxy substrates is also presented.