Formation Of Pd Nanoparticles Research Articles

Dispersed single-atom Co and Pd nanoparticles forming a PdCo bimetallic catalyst for CO oxidation

PdCo bimetallic catalysts were synthesized using oleyamine and oleaic acid as capping agents to effectively disperse the metals over activated carbon via incipient impregnation. The synthesis, in conjunction with the carbon support, resulted in single-atom dispersion of Co over the carbon with the formation of Pd nanoparticles. Thermal activation of the catalysts, under a reducing atmosphere, allowed sufficient Pd and Co mobility leading to the formation of a PdCo alloy, according to STEM, in situ XRD and XANES analysis. Furthermore, molar percentages between 0.2 to 0.3 in Co were effective in producing Pd nanoparticles that are partially decorated with Co to produce a highly active catalyst for CO oxidation. The optimized catalyst formulation and synthesis method provide active sites for CO absorption onto Pd while maintaining active sites, in close proximity, for O2 activation via Co. The resulting catalyst showed a marked reduction in CO light-off temperatures compared to the monometallic formulations.

Highly dispersed Pd clusters/nanoparticles encapsulated in MOFs via in situ auto-reduction method for aqueous phenol hydrogenation

In this work, a novel in situ auto-reduction strategy was developed to encapsulate uniformly dispersed Pd clusters/nanoparticles in MIL-125-NH2. It is demonstrated that the amino groups in MIL-125-NH2 can react with formaldehyde to form novel reducing groups (-NHCH2OH), which can in situ auto-reduce the encapsulated Pd2+ ions to metallic Pd clusters/nanoparticles. As no additional reductants are required, the strategy limits the aggregation and migration of Pd clusters and the formation of large Pd nanoparticles via controlling the amount of Pd2+ precursor. When applied as catalysts in the hydrogenation of phenol in the aqueous phase, the obtained Pd(1.5)/MIL-125-NH-CH2OH catalyst with highly dispersed Pd clusters/nanoparticles with the size of around 2 nm exhibited 100% of phenol conversion and 100% of cyclohexanone selectivity at 70 °C after 5 h, as well as remarkable reusability for at least five cycles due to the large MOF surface area, the highly dispersed Pd clusters/nanoparticles and their excellent stability within the MIL-125-NH-CH2OH framework.

Magnetically Recoverable Nanoparticulate Catalysts for Cross-Coupling Reactions: The Dendritic Support Influences the Catalytic Performance.

Carbon-carbon cross-coupling reactions are among the most important synthetic tools for the preparation of pharmaceuticals and bioactive compounds. However, these reactions are normally carried out using copper, phosphines, and/or amines, which are poisonous for pharmaceuticals. The use of nanocomposite catalysts holds promise for facilitating these reactions and making them more environmentally friendly. In the present work, the PEGylated (PEG stands for poly(ethylene glycol) pyridylphenylene dendrons immobilized on silica loaded with magnetic nanoparticles have been successfully employed for the stabilization of Pd2+ complexes and Pd nanoparticles. The catalyst developed showed excellent catalytic activity in copper-free Sonogashira and Heck cross-coupling reactions. The reactions proceeded smoothly in green solvents at low palladium loading, resulting in high yields of cross-coupling products (from 80% to 97%) within short reaction times. The presence of magnetic nanoparticles allows easy magnetic separation for repeated use without a noticeable decrease of catalytic activity due to the strong stabilization of Pd species by rigid and bulky dendritic ligands. The PEG dendron periphery makes the catalyst hydrophilic and better suited for green solvents. The minor drop in activity upon the catalyst reuse is explained by the formation of Pd nanoparticles from the Pd2+ species during the catalytic reaction. The magnetic separation and reuse of the nanocomposite catalyst reduces the cost of target products as well as energy and material consumption and diminishes residual contamination by the catalyst. These factors as well as the absence of copper in the catalyst makeup pave the way for future applications of such catalysts in cross-coupling reactions.

In-situ one-step deposition of highly dispersed palladium nanoparticles into zirconium metal–organic framework for selective hydrogenation of furfural

• Pd nanoparticles are deposited on SBUs of UiO-66 by an in-situ method. • UiO-66-Pd catalyst is active in the furfural hydrogenation in liquid phase. • The UiO-66-Pd shows 71% furfural conversion and 94% furfuryl alcohol selectivity. • In comparison to two-step method, UiO-66-Pd demonstrates higher activity (17%). Palladium nanoparticles highly dispersed into UiO-66 as an efficient and selective hydrogenation catalyst is synthesized by a one-step in-situ method of incorporation of the Pd centers on the secondary building units (SBUs) of UiO-66 as the support and compared to a two-step method. Using DMF as both a solvent and a reducing agent, HCl as an enhancer of the terminal OH groups on Zr-clusters by linker elimination, and a temperature profile result in the incorporation of Pd precursor at lower temperatures and generation of Pd nanoparticles at higher temperatures. The catalysts were characterized by BET surface area measurement, SEM, XRD, HR-TEM, XPS, H 2 -TPR, and CO pulse chemisorption methods. The regulation of the temperature and time in the one-step method results in the formation of Pd nanoparticles embedded in the MOF with a higher dispersion and accessibility in comparison to the two-step method. An automated high-pressure semicontinuous setup was used for the furfural hydrogenation. The 1 wt% Pd on UiO-66 exhibits a high conversion of 71% and selectivity of 94% for hydrogenation of furfural to furfuryl alcohol in the liquid phase at 20 bar H 2 , 110 ˚C and 4 h reaction. The catalyst was used repeatedly without significant deactivation.

X-ray absorption spectroscopy study of metal–organic frameworks functionalized by Pd: formation and growth of Pd nanoparticles

X-ray absorption spectroscopy study of metal–organic frameworks functionalized by Pd: formation and growth of Pd nanoparticles

Markovnikov Wacker‐Tsuji Oxidation of Allyl(hetero)arenes and Application in a One‐Pot Photo‐Metal‐Biocatalytic Approach to Enantioenriched Amines and Alcohols

AbstractThe Wacker‐Tsuji aerobic oxidation of various allyl(hetero)arenes under photocatalytic conditions to form the corresponding methyl ketones is presented. By using a palladium complex [PdCl2(MeCN)2] and the photosensitizer [Acr‐Mes]ClO4 in aqueous medium and at room temperature, and by simple irradiation with blue led light, the desired carbonyl compounds were synthesized with high conversions (>80%) and excellent selectivities (>90%). The key process was the transient formation of Pd nanoparticles that can activate oxygen, thus recycling the Pd(II) species necessary in the Wacker oxidative reaction. While light irradiation was strictly mandatory, the addition of the photocatalyst improved the reaction selectivity, due to the formation of the starting allyl(hetero)arene from some of the obtained by‐products, thus entering back in the Wacker‐Tsuji catalytic cycle. Once optimized, the oxidation reaction was combined in a one‐pot two‐step sequential protocol with an enzymatic transformation. Depending on the biocatalyst employed, i. e. an amine transaminase or an alcohol dehydrogenase, the corresponding (R)‐ and (S)‐1‐arylpropan‐2‐amines or 1‐arylpropan‐2‐ols, respectively, could be synthesized in most cases with high yields (>70%) and in enantiopure form. Finally, an application of this photo‐metal‐biocatalytic strategy has been demonstrated in order to get access in a straightforward manner to selegiline, an anti‐Parkinson drug.magnified image

Preparation and Investigation of Pd and Bimetallic Pd-Sn Nanocrystals on γ-Al2O3

One of the key factors for producing highly dispersed controlled nanoparticles is the method used for metal deposition. The decomposition of metal-organic precursors is a good method for deposition of metal nanoparticles with very small sizes and narrow size distributions on the surface of various supports. The preparation process of Pd and bimetallic Pd-Sn nanoparticles supported onto γ-Al2O3 is considered. The samples were prepared by diffusional co-impregnation of the γ-Al2O3 support by using organometallic Pd(acac)2 and Sn(acac)2Cl2 precursors. To achieve the formation of Pd and bimetallic Pd-Sn nanoparticles on the support surface, the synthesized samples were then subjected to thermal decomposition under Ar (to decompose the organometallic bound to the surface while keeping the formed nanoparticles small) followed by an oxidation in O2 (to eliminate the organic compounds remaining on the surface) and a reduction in H2 (to reduce the nanoparticles oxidized during the previous step). A combination of methods (ICP-OES, TPR-H2, XPS, TEM/EDX) was used to compare the physical-chemical properties of the synthesized Pd and bimetallic Pd-Sn nanoparticles supported on the γ-Al2O3. The three samples exhibit narrow size distribution with a majority on nanoparticles between 3 and 5 nm. Local EDX measurements clearly showed that the nanoparticles are bimetallic with the expected chemical composition and the measured global composition by ICP-OES. The surface composition and electronic properties of Pd and Sn on the γ-Al2O3 support were investigated by XPS, in particular the chemical state of palladium and tin after each step of thermal decomposition treatments (oxidation, reduction) by the XPS method has been carried out. The reducibility of the prepared bimetallic nanoparticles was measured by hydrogen temperature programmed reduction (TPR-H2). The temperature programmed reduction TPR-H2 experiments have confirmed the existence of strong surface interactions between Pd and Sn, as evidenced by hydrogen spillover of Pd to Sn (Pd-assisted reduction of oxygen precovered Sn). These results lead us to propose a mechanism for the formation of the bimetallic nanoparticles.

Formation and stabilization of nanosized Pd particles in catalytic systems: Ionic nitrogen compounds as catalytic promoters and stabilizers of nanoparticles

• Pd catalytic systems usually contain nanoparticles regardless of the type of pre-catalyst and require special stabilizers. • Ionic nitrogen compounds stabilize Pd nanoparticles and open up new fields of application in organic synthesis. • The structure of the ionic compound affects the stabilization mechanism and the efficiency of the catalysts. • The catalytic action of the ionic nitrogen compound can outweigh the action of the ligands. • The overall effect of stabilization can be highly dependent on the nature of catalysis and reaction conditions. Actual palladium catalysts in synthetic transformations in reaction mixtures are usually represented by dynamic catalytic systems that contain various interconvertible forms of metal particles, including molecular complexes, metal clusters, and nanoparticles. The low thermodynamic stability of Pd nanoparticles can lead to their aggregation and, as a consequence, to the deactivation of the catalytic systems. Therefore, stabilization of nanosized Pd particles is of key importance to ensure efficient catalysis. This review discusses the main pathways for the formation of Pd nanoparticles and clusters from various precatalysts in catalytic systems, as well as current views on the mechanisms of stabilization of these nanosized Pd particles using various types of ionic nitrogen compounds, such as ammonium, amidinium, azolium, and pyridinium salts. The use of ionic nitrogen compounds as specially added or in situ formed stabilizers, ligands, catalytic promoters, heterogenized catalysts (supported ionic liquid phase, SILP) and reaction media (ionic liquids) is exemplified by several important catalytic reactions. The main effects of ionic nitrogen compounds on catalytic processes are also discussed, including possible involvement in catalytic cycles and unwanted side reactions.

Palladium Nanocatalysts for Cascade C−N Cross‐Coupling/Heck Reaction

AbstractHighly stable nanocatalysts have been synthesized in aqueous medium at room temperature by the in situ formation of Pd nanoparticles (PdNPs) embedded in an enzyme net. Different parameters in the synthesis were evaluated such as T, ratio enzyme/Pd salt, using Candida antarctica B lipase (CALB) as enzyme. In all different CALB/PdNPs hybrids synthesized, crystalline Pd(0) as a unique metallic species was confirmed by XRD. Spherical nanoparticles were obtained with diameter size from 2 to 11 nm, depending on the synthetic conditions. These CALB/PdNPs hybrids were employed as catalyst in the C−N/Heck reaction cross‐coupling cascade for the synthesis of substituted azaindoles using various amino‐o‐bromopyridines as starting material in moderate conditions. The best conversion with high selectivity of the formation of C2‐substituted azaindoles was obtained at 90 °C using dioxane containing 5% water as the best reaction solvent from the different solvents tested, using potassium carbonate as milder base. The catalysis with these CALB/PdNPs hybrids at these conditions was also successful in the production of several isomers of azaindoles, especially relevant for the formation of the 7‐ azaindole, where 65% conversion was obtained, a very good improvement when compared to the reported protocol using a Pd2(dba)3/XPhos/t‐BuONa catalytic system.

The in-situ XAS study on the formation of Pd nanoparticles via thermal decomposition of palladium (II) acetate in hydroxyl functionalized ionic liquids

The formation of palladium nanoparticles (NPs) via thermal decomposition of palladium (II) acetate in hydroxyl functionalized ionic liquid (IL) [C2OHmim]+[NTf2]− was studied using in-situ energy dispersive x-ray absorption fine structure spectroscopy (DXAFS) and complementary methods such as transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry. Detailed XAFS spectra analysis unraveled that the palladium acetate trimer precursor underwent dissociation after being dispersed in ILs, which accelerated the thermal decomposition compared with other organic solvents. Based on the reaction kinetics, extened x-ray absorption fine structure spectroscopy fitting and TEM characterization results, the thermal decomposition process can be divided three successive stages namely the explosive nucleation, autocatalytic surface growth and NP attachment growth.

Biological activity of PdNPs derived from hemicellulose via microwave assisted green synthesis

In recent era, synthesis of nanoparticles through green method has gained more attention as it is an environmentally friendly approach. Bio-synthesis of palladium nanoparticles (PdNPs) through single step and environmental benign microwave irradiation technique, using hemicellulose as reducing agent is reported. As synthesized PdNPs were characterized by various techniques such as FTIR, UV–Visible spectroscopy, XRD, SEM and TEM to confirm the formation of PdNPs for studying its biological activity. From UV–Visible spectra, it is observed that a SPR (Surface Plasmon Resonance) band at 280–300 ​nm clearly shows the formation of Pd nanoparticles. This was supported by FTIR as the wavenumbers observed at 473,524 and 616 ​cm−1corresponds to the metal stretching and bending frequencies. The phase formation and crystallinity of the PdNPs was studied using XRD. The observed (hkl) values (100), (111), (200) and (220) planes corresponds to the face centered cubic (fcc) structure of Pd (JCPDS No: 05–0681). Also, a well-defined and sharp reflections shows that, PdNPs are crystalline nature. The morphology of the PdNPs was studied through FESEM indicatesthe obtained particles are spherical in shape and seems to be agglomerated. The particle size of the PdNPs was measured through HRTEM and the average size was found to 10 ​nm. Further, PdNPs are used in the biological activity, it shows good antibacterial activity against both Gram-positive and Gram-negative bacteria's E. coli, Salmonella typhi, S. aureusand B. Subtilis B. shows maximum inhibition 21.40 ​mm. In addition, cytotoxic effects on MDA- MB 231, HepG2 and HeLa cells (survivability of cells is found MDA-MB 231 ​= ​30%, HepG2 ​= ​50% and HeLa ​= ​60%) were examined by series of assay. Overall, the present studies reveals that PdNPs are showing effective antibacterial activity and low cytotoxic.

Suzuki-Miyaura Cross-Coupling of Bromotryptophan Derivatives at Ambient Temperature.

Mild reaction conditions are highly desirable for bio‐orthogonal side chain derivatizations of amino acids, peptides or proteins due to the sensitivity of these substrates. Transition metal catalysed cross‐couplings such as Suzuki–Miyaura reactions are highly versatile, but usually require unfavourable reaction conditions, in particular, when applied with aryl bromides. Ligand‐free solvent‐stabilised Pd‐nanoparticles represent an efficient and sustainable alternative to conventional phosphine‐based catalysts, because the cross‐coupling can be performed at considerably lower temperature. We report on the application of such a highly reactive heterogeneous catalyst for the Suzuki–Miyaura cross‐coupling of brominated tryptophan derivatives. The solvent‐stabilised Pd‐nanoparticles are even more efficient than the literature‐known ADHP‐Pd precatalyst. Interestingly, the latter also leads to the formation of quasi‐homogeneous Pd‐nanoparticles as the catalytic species. One advantage of our approach is the compatibility with aqueous and aerobic conditions at near‐ambient temperatures and short reaction times of only 2 h. The influence of different N α‐protecting groups, boronic acids as well as the impact of different amino acid side chains in bromotryptophan‐containing peptides has been studied. Notably, a surprising acceleration of the catalysis was observed when palladium‐coordinating side chains were present in proximal positions.

Zirconium promoter effect on catalytic activity of Pd based catalysts for heterogeneous hydrogenation of nitrile butadiene rubber

Three PdZr bi-component catalysts supported on modified silica have been successfully synthesized via different Zr introduction methods and utilized for the hydrogenation of nitrile butadiene rubber (NBR) to produce high value-added hydrogenated NBR. It is demonstrated that the introduction of Zr can lead to the formation of small-sized and electron-rich Pd nanoparticles and the order of adding Zr can significantly affect the catalytic activity. In particular, the PdZr bi-component catalyst obtained by introducing Zr followed by adding Pd is found to be more stable on the silica support, which exhibits a high hydrogenation degree of 90.9% with 100% selectivity to CC bond, close to the single Pd catalyst with double Pd contents. The electronic structure and reaction mechanism analysis from density functional theory calculations further reveal that the addition of Zr component leads to negatively charged Pd species with lower energy barrier for the hydrogenation of CC bond. Our findings provide a useful guidance for the design of efficient and low-cost bi-component catalysts for the selective hydrogenation of unsaturated polymers.

Structural Effect of Pincer Pd(II)–ONO Complexes Modified with Acylthiourea on Sizes of the In Situ Generated Pd Nanoparticles During Heck Coupling Reaction

The Pd nanoparticles generated in situ from Pd–pincer complexes catalyzed Heck coupling reaction. For this purpose, new Pd(II)–ONO pincer complexes (1–4) containing acylthiourea ancillary ligand were obtained by treating [Pd(ONO)(CH3CN)] with the respective N-substituted carbamothioyl benzamide ligand (L1–L4). Formation of these complexes was confirmed by UV–Visible, FT-IR, NMR and mass spectroscopic techniques. The sizes of in situ formed Pd nanoparticles were greatly affected by the substituent in ancillary ligand, which in turn influenced their catalytic activity towards Heck coupling reaction. The in situ formed Pd nanoparticles during Heck reaction were removed from the reaction medium and analyzed using HR-TEM to estimate the sizes of the Pd nanoparticles. Complex [Pd(ONO)((N-benzylcarbamothioyl)benzamide)] (1) which does not possess any substituent on the benzyl moiety of acylthiourea produced the smallest Pd nanoparticles with the average particle size of 3.7 nm. Hence, complex 1 showed the utmost catalytic activity. With complex 1, 51–99% of conversion was observed during Heck coupling reaction of styrene with various aryl halides. XPS results confirmed that the recovered black particles were Pd(0). A reasonable recyclability results were achieved by these in situ generated Pd nanoparticles.

Ultrasonically driven green synthesis of palladium nanoparticles by Coleus amboinicus for catalytic reduction and Suzuki-Miyaura reaction

A novel ultrasonically driven bio-reduction method was adopted to reduce the palladium chloride into palladium nanoparticles (PdNPs@CA) using coleus amboinicus extract as a green synthetic protocol. XRD confirms the formation of phase pure cubic Pd nanoparticles with the crystallite size range of 40−50 nm. The UV–vis spectrum reveals the formation of Pd nanoparticles by the disappeared peak at 480 nm of PdCl2 solution. The size distribution and surface morphology of prepared Pd nanoparticles showed spherical shaped nanoparticles with less agglomeration. The catalytic reduction behaviour of the Pd suspension is studied by 4-nitro phenol reduction process in 8 min further confirms its high catalytic performance. Synthesized PdNPs@CA were explored in ultrasound promoted Suzuki-Miyaura coupling reaction to determine the catalytic behaviour with ultrasonic frequency of 40 kHz and power of 150 W (Power sonic 410 bath sonicator) and its recycling ability is determined. It was found that aryl halides reacted with aryl boronic acids to obtain biaryl compound with excellent reaction yields in the presence of PdNPs@CA only in 30 min using PEG-400 as a green solvent. PdNPs@CA can be recovered efficiently and reused for 7 cycles without loss of its catalytic property.

Melamine Foams Decorated with In-Situ Synthesized Gold and Palladium Nanoparticles.

A versatile and straightforward route to produce polymer foams with functional surface through their decoration with gold and palladium nanoparticles is proposed. Melamine foams, used as polymeric porous substrates, are first covered with a uniform coating of polydimethylsiloxane, thin enough to assure the preservation of their original porous structure. The polydimethylsiloxane layer allows the facile in-situ formation of metallic Au and Pd nanoparticles with sizes of tens of nanometers directly on the surface of the struts of the foam by the direct immersion of the foams into gold or palladium precursor solutions. The effect of the gold and palladium precursor concentration, as well as the reaction time with the foams, to the amount and sizes of the nanoparticles synthesized on the foams, was studied and the ideal conditions for an optimized functionalization were defined. Gold and palladium contents of about 1 wt.% were achieved, while the nanoparticles were proven to be stably adhered to the foam, avoiding potential risks related to their accidental release.

Single-atom Pd dispersed on nanoscale anatase TiO2 for the selective hydrogenation of phenylacetylene

Combining the advantages of both heterogeneous and homogeneous catalysts, single-atom catalysts (SACs) with unique electronic properties have shown excellent catalytic properties. Herein, we report single-atom Pd dispersed on nanoscale TiO2 prepared by self-assembly method as efficient and selective catalysts for the hydrogenation of phenylacetylene to styrene. The catalysts were characterized by N2 adsorption/desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and X-ray absorption spectroscopy (XAS). 0.2Pd-TiO2(150°C) possessing dominant single-atom Pd species, exhibited a turnover frequency (TOF) of over 8000 h−1 with 91% selectivity towards styrene at room temperature. Further increasing Pd loading from 0.2% to 0.5% and 1.5% resulted in the decrease of activity probably due to the formation of Pd nanoparticles. Besides, the 0.2Pd-TiO2 prepared by self-assembly strategy showed better catalytic performance than commercial 10%Pd/C and 0.2Pd-TiO2 synthesized by using impregnation method.

Synthesis of Pd−Rh Bimetallic Nanoparticles with Different Morphologies in Reverse Micelles and Characterization of Their Catalytic Properties

Synthesis of bimetallic nanoparticles (NPs) of the transition metals Rh and Pd in H2O/AOT/isooctane (where AOT is dioctyl sodium sulfosuccinate) reverse-micelle solutions (RMSs) in the presence of molecular oxygen and quercetin, a flavonoid, is described. The methods for NP synthesis used here enable us to prepare alloyed-type Rh−Pd NPs and core/shell Pd/Rh and Rh/Pd NPs with the metal molar ratio of 1 : 1. With both Rh3+ and Pd2+ ions present in an RMS simultaneously, palladium ions are reduced first, and the formed Pd NPs have an inhibitive effect on reduction of rhodium ions. The stability of a mixture of Rh and Pd NPs in RMSs is investigated, and the mixture of NPs with a mean diameter of ~2.7 nm is found to be stable for at least 25 days. Pd and Rh NP-based catalysts are prepared by absorption of the synthesized NPs on γ-Al2O3, and their catalytic activity is tested in the monomolecular hydrogen isotope exchange reaction. A synergetic effect, manifested as an enhanced catalytic activity, is observed for the catalyst prepared by adsorption of the mixture of Rh and Pd NPs on γ-Al2O3.

Facile Synthesis of a Carbon-Encapsulated Pd Catalyst for Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells

The key to popularizing proton exchange fuel cells is developing highly active, stable, and cost-effective catalysts for oxygen reduction reaction. Pd is considered as an alternative to Pt due to its high tolerance to poisoning and electronic similarity with Pt, which is a robust but expensive catalyst. However, its vulnerability to dissolving in acidic media prevents the use of Pd as an oxygen reduction reaction catalyst. In this study, a facile synthesis method was developed to prepare a carbon-encapsulated Pd catalyst using aniline. The oxidative polymerization of aniline with a Pd precursor formed Pd nanoparticles embedded in a rod-shaped polyaniline matrix. The polyaniline matrix was carbonized using heat treatment, which then acted as a source of N-containing carbon layer that protects Pd nanoparticles from dissolution and improves oxygen reduction reaction activity. The stability and oxygen reduction reaction activity of the synthesized Pd catalyst were strongly dependent on the heat treatment temperature. The Pd catalysts heat-treated at 300 °C and 500 °C exhibited improved activity and stability as compared to commercial Pd/C. We envision that this method is suitable for mass production of active and stable oxygen reduction reaction catalysts in proton exchange fuel cells.

Functionalized cellulose-preyssler heteropolyacid bio-composite: An engineered and green matrix for selective, fast and in–situ preparation of Pd nanostructures: synthesis, characterization and application

A new and green engineered biocomposite was synthesized by sol–gel method, using different loadings of the Preyssler heterpolyacid (8, 15, 25, 40 and 50 wt%) on the functionalized microcrystaline cellulose surface. For the first time, this two-component polymeric biocomposite used for in-situ catalytic synthesis of Pd nanoparticles with the aim of producing tricomponent nanobiocomposites. Preyssler loading on the functionalized surface, controled the size and shape of Pd nanoparticles, time, and pH of their formation. All biocomposites and nanobiocomposites were characterised by FTIR, XRD, BET, TGA, SEM, EDS and TEM. The SEM analysis for two component polymeric biocomposites confirmed the presence of the Preyssler on the surface of functionalized cellulose. The formation of Pd nanoparticles on the surface, was observed by color changing (yellow to deep brown) and confirmed by UV–visible spectroscopy. The Pd nanoparticles formation was fast (2–4 min) for 8 wt% in pH = 2–3 at 80 °C. TEM analysis illustrated the spherical Pd nanoparticles with a size of 5–20 nm, at the lowest loading of Preyssler, and rod shapes with a size of 30–40 nm at the highest loading. The obtained nanobiocomposite exhibited high catalytic activity for the decolourisation of tartrazine, as a model of dyes pollutant in the industry with high degradation efficiency. The catalytic reactions were extended with other azo dyes including methyl orange and rodamine B.