Prepared Platinum Nanoparticles Research Articles

Edge engineering of platinum nanoparticles via porphyrin-based ultrathin 2D metal–organic frameworks for enhanced photocatalytic hydrogen generation

Edge-doping engineering in metal nanoparticles (MNPs) is always hard to achieve due to the high surface energy of the hybrid MNPs, while porphyrin-based ultrathin two-dimensional (2D) metal–organic framework (MOF) is demonstrated the positive role in stabilize this structure. Herein, a bottom-up method was developed to prepare platinum nanoparticles (PtNPs)-decorated 2D MOF nanosheets, where a porphyrin ligand of Pd-metalized tetrakis(4-carboxyphenyl)porphyrin (PdTCPP) was applied to synthesize ultrathin MOF nanosheets as Zr-TCPP(Pd) in high yield. Attributing to the high superficial area of ultrathin Zr-TCPP(Pd) nanosheets, Pt NPs can well anchor uniformly with small nanoparticle size to obtain 2% Pt/Zr-TCPP(Pd) hybrid nanosheets, which showed a higher photocatalytic hydrogen production rate of 3348 μmol g-1h−1. This is attributed to the coordination between Zr4+ and C = O of PVP, which promotes the contact between PtNPs and Zr-TCPP(Pd) nanosheets. As a result, the long-life electrons of PdTCPP photosensitizers are rapidly transferred to the electron capture center PtNPs, and the photoelectron-hole recombination is effectively inhibited. The apparent quantum efficiency of 2% Pt/Zr-TCPP(Pd) reaches up to 1.56% at 420 nm. The density functional theory (DFT) calculations revealed the Pd-doped position in Pt79 nanoparticle is important that the Pt78Pdsurf. model (Pd atom was doped on the surface of Pt nanoparticle) showed the highest activity with abundant exposed active region.

Spherical polyelectrolyte brushes as bio‐platforms to integrate platinum nanozyme and glucose oxidase for colorimetric detection of glucose

AbstractThe integration of nanozyme and natural enzyme for cascade reactions has attracted great attention due to their huge potential applications in detection, biomedicine, and catalysis. Here the novel cascade bio‐platforms were fabricated by using spherical poly[(2‐methacryloyloxyethyl)trimethyl ammonium chloride] (PMOTA) brushes (SPB) as nanoreactors to prepare platinum nanoparticles in situ and as nanocarriers to immobilize glucose oxidase (GOX). The generated Pt nanoparticles possess high stability and peroxidase‐like properties, which can catalyze the oxidation of 3,3′,5,5′‐tetramethylbenzidine (TMB) in the presence of H2O2 to generate blue colored oxidized TMB (oxTMB). And the absorbed GOX can specifically catalyze the oxidation of glucose into gluconic acid and H2O2, while the produced H2O2 is subsequently catalyzed by the Pt nanozymes. Thus, the co‐immobilized Pt nanozymes and GOX within SPB (SPB@Pt@GOX) acted as effective biosensors for colorimetric detection of glucose showing high selectivity and great feasibility. This work demonstrates a facile and general strategy to use SPB as bio‐platforms to integrate nanozymes and natural enzymes for cascade reactions.

The Synthesis of Pt-CNTs Nanocatalyst Promoted by Visible Light and Catalytic Reduction of <i>4</i>-Nitrophenol

Photochemistry to prepare platinum nanoparticles (Pt NPs) is an essential way to control Pt NPs catalyst size distribution. This article reports a series of morphologically controlled syntheses of Pt NPs loaded on modified carbon nanotube (Pt-CNTs). In the synthesis, Polyethylene glycol (PEG) participates in reactions both as a reducing agent and a stabilizer. Visible light irradiation was adopted as a kinetic controlling approach. Typical 4-nitrophenol (4-NP) reduction was adopted to probe the catalytic performances. Characterizations prove that visible light irradiation is an effective way to control the reaction process. In the optimized reaction conditions, i.e., when the ratio PEG:H2O is 1:9, and the pH is 10, the as-prepared Pt NPs are consequently in a very narrow sized distribution with an average diameter of 1.29 nm. The Pt-CNTs present a high reaction rate constant of 0.624 min-1 in the catalytic reduction of 4-NP. All the research results are beneficial for exploring more green chemistry and facile photochemical approaches in the controlled preparation of Pt nanocatalysts.

Biosynthesis and characterization of platinum nanoparticles using Iraqi Zahidi dates and evaluation of their biological applications

Platinum nanoparticles (Pt NPs) were synthesized by utilizing the Zahidi dates extract by green synthesis technique. Platinum salts were successfully reduced to their corresponding Pt NPs in the presence of aqueous dates extract which considers a rich source of phytochemicals that led to the reduction of Pt+4 to Pt° atoms by providing electrons for these ions. Many techniques characterized the nanoparticles. TEM analysis showed that the Pt NPs were exhibited in diameters ranging from (30−45) nm. FE-SEM images display nanoparticles in spherical shapes. AFM screening shows that Platinum nanoparticles had small size distribution. XRD diffraction examination showed that the formation of Platinum nanoparticles exhibits a face centred cubic crystalline structure by spectrum comparative to the standard confirmed spectrum of Platinum particles produced in the experiments were in the shape of nanocrystals. The fourier transform infrared spectroscopy spectrum showed various peaks ranging from (400–4000) cm−1 used to identify the functional groups responsible for reducing and capping of Pt NPs. Cancer cells including the ovarian cancer SKO-3 cell line and Oesophageal cancer SK-GT-4 cell line were exposed to a series of prepared Platinum nanoparticle concentrations (0.00125, 0.0025, 0.005, 0.01) M, and the inhibition rate of growth in cells was measured for 72 h. The cytotoxicity screening showed that there was a highly toxic effect on the cancer cells. Gram-negative bacterial strain Pseudomonas aeruginosa and Gram-positive bacterial strain Streptococcus pyogenes were exposed to a series of concentrations from prepared Platinum nanoparticles (0.00125, 0.0025, 0.005, 0.01) M. The results exhibited significant inhibitory activity and the rate of bacterial growth inhibition increased with increasing concentration.

Sustainable route of synthesis platinum nanoparticles using orange peel extract

ABSTRACTPlatinum is the best catalyst to promote electrochemical reactions in fuel cell. Despite the high cost of platinum, finding a cheaper, sustainable, and environmentally to produce catalyst is needed. Green synthesis has been used to produce metal nanoparticles using reducing agents drawn from natural sources. In this study, the green synthesis of platinum nanoparticles is using orange peel extract as a bio-reducing agent. The reaction to produce platinum nanoparticles is undertaken in both acidic and alkaline media and has been employed at different selected pH values. The catalyst was physically and electrochemically characterized by X-ray diffraction (XRD), energy-dispersive X-ray (EDX), transmission electron microscope (TEM), and cyclic voltammetry. The prepared platinum nanoparticles have different distributions at different pH, while the particle size of the platinum remains in the range of 1.6–4.0 nm. The platinum nanoparticles are supported on carbon black for methanol oxidation reaction. The electrochemical analysis reveals that the methanol oxidation peak of the prepared platinum supported on carbon black is at 0.9 V (vs. RHE). The synthesized platinum nanoparticles have strong potential to be used in the methanol oxidation reaction in a DMFC, as they are well distributed, but the nanoparticles need further improvement to be applied in carbon support and alloying to reduce the amount of platinum.

Synthesis of Platinum Nanoparticles by Gamma Co-60 Ray Irradiation Method Using Chitosan as Stabilizer

Platinum nanoparticles were synthesized using the gamma-ray irradiation as a reducing factor and chitosan as a stabilizer. The prepared platinum nanoparticles were characterized using ultraviolet-visible spectroscopy (UV-Vis), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The saturated conversion dose to reduce the Pt4+ to Pt0 was found to be about 14 kGy for initial Pt4+ concentration of 1 mM. The size of the platinum nanoparticles (1.4–1.6 nm) did almost not change with the increase of chitosan concentration from 0.5 to 2.0%. Thus, gamma Co-60 ray irradiation method is favorable for synthesizing PtNPs with the small sizes.

Fabrication of Uniformly Sized Gold Nanoparticles on Glassy Carbon by Simple Electrochemical Method

Gold nanoparticles (AuNPs) can be fabricated on glassy carbon (GC) cathode by a galvanostatic electrolysis that employs an Au wire as anode. This electrolysis is essentially similar to a simple method that has been used to prepare platinum nanoparticles (Electrochim. Acta, 129, 152 (2014)): it is performed under the conditions that the electrolysis of water occurs in strong acid solutions such as H2SO4 and HNO3. The Au anode, where oxygen evolution occurs, dissolves to form Au ions and the GC cathode, where hydrogen evolution occurs, reduces them. Although the method is simple in principle, the prepared AuNPs are uniform in size and well dispersed on the GC surface. The size and number density of AuNPs depend on the electrolysis conditions such as the applied current and electrolysis time. The characteristics also depend on the kind of electrolyte solution: the size and density are larger when the solution is 0.5 M H2SO4 than when it is 0.5 M HNO3. This is because the dissolution rate of Au anode (i.e., the formation rate of Au ions) in H2SO4 solution is faster than that in HNO3 solution, which has been confirmed by quartz crystal microbalance.

Improved Pt/C electrocatalysts for methanol oxidation prepared by different reducing agents and surfactants and DFT studies on it

In this work, PtCl4 as precursor; sodium borohydride (Cat I), hydrazinium hydroxide (Cat II), and formaldehyde (Cat III) as reducing agents; and 1-heptanamine (a), N-methyl-1-heptanamine (b), and N,N-dimethyl-1-heptanamine (c) as surfactants were used to prepare platinum nanoparticles which were then dispersed on carbon XC-72 for use as catalysts in the methanol oxidation reaction. XRD and TEM results indicate that the platinum has a face-centered cubic structure and is found as small and agglomerated particles in different shapes, sizes, and densities. Cat I comprises small (~ 5 nm) cubic and formless agglomerated (~ 20–~ 300 nm) particles, Cat II is composed of small (~ 5 nm) and a significant number of quite dense spherical agglomerated (~ 20–~ 150 nm) particles, and Cat III contains large number of small (~ 5 nm) and a small number of spherical, less dense, and agglomerated (~ 20–~ 200 nm) particles. XPS data shows that the platinum exists in two different oxidation states Pt(0) (~ 64.5–~ 69.6%) and Pt(IV) (~ 35.5–~ 30.4%), and platinum surface also contains OH, H2O, C–O, C=O, and carbon. DFT and FTIR show that the surfactants decompose to form partially crystalline carbon. Electrochemical studies reveal that performance order of the catalysts towards the methanol oxidation reaction is Cat II < Cat I < Cat III, and that Cat IIIc has the highest performance, which is 2.23 times larger than E-TEK catalysts. It was found that the performance of the catalysts depends on the kind of surfactant, reducing agent, electrochemical surface area, percent platinum utility, roughness factor, and If/Ir ratio.

Bio-fabrication of catalytic platinum nanoparticles and their in vitro efficacy against lungs cancer cells line (A549)

Platinum based drugs are considered as effective agents against various types of carcinoma; however, the severe toxicity associated with the chemically prepared platinum complexes limit their practical applications. Similarly, water pollution caused by various organic moieties is another serious health problem worldwide. Hence, an intense need exists to develop new, effective and biocompatible materials with catalytic and biomedical applications. In the present contribution, we prepared platinum nanoparticles (PtNPs) by a green route using phytochemicals as a source of reducing and stabilizing agents. Well dispersed and crystalline PtNPs of spherical shapes were prepared and characterized. The bio-fabricated PtNPs were used as catalyst and anticancer agents. Catalytic performance of the PtNPs showed that 84% of the methylene blue can be reduced in 32min under visible light irradiation (K=0.078min−1). Similarly the catalytic conversion of 4-nitrophenol to 4-aminophenol was achieved in <20min (K=0.124min−1). The in vitro anticancer study revealed that biogenic PtNPs are the efficient nano-agents possessing strong anticancer activity against the lungs cancer cells line (A549). Interestingly, the as prepared PtNPs were well tolerated by normal human cells, and therefore, could be effective and biocompatible agents in the treatment of different cancer cells.

Preparations of Platinum Nanoparticles and Their Catalytic Performances.

This work investigates the effect of reducing agents and stabilizing agent on the preparation of platinum nanoparticles. We used H2PtCl6 as a precursor and hydrogen and sodium borohydride as reducing agents to prepare colloidal platinum nanoparticles. Polyvinylpyrrolidones (PVPs) is used as a stabilizing agent. Hydrogen and sodium borohydride are used as reducing agents. The prepared platinum nanoparticles are characterized by transmission electron microscopy (TEM) and X-ray diffractometer (XRD). The concentrations of the precursor and the stabilizing agent influence the size of platinum nanoparticles, while the reducing agents influence the morphologies and structures of platinum nanoparticles. Supported platinum catalysts (CPt-NaBH4, CPt-H2) are prepared from colloidal platinum nanoparticles and γ-Al2O3. For comparison, another supported platinum catalyst (IPt) is prepared by the conventional impregnation method with an aqueous H2PtCL6 solution and γ-AL2O3. The catalytic activities of CPts are superior to that of IPt on the basis of benzene conversion.

A one-step, clean, capping-agent-free electrochemical approach to prepare Pt nanoparticles with preferential (100) orientation and their high electrocatalytic activities

Abstract A clean and simple electrodeposition method without the use of any organic additives has been reported to prepare platinum nanoparticles with preferential (100) orientation directly on the conductive substrate. The formation of platinum nanoparticles exposing (100) facets was confirmed by electrochemical methods and high-resolution transmission electron microscopy. The fraction of Pt (100) sites increases as the electrodeposition current density increases from 0.2 to 10 mA cm − 2 . Furthermore, as the Pt (100) fraction increases, the specific activity of the Pt particles for ammonia oxidation increases obviously.

Influence of Organic Amino and Thiol Ligands on the Geometric and Electronic Surface Properties of Colloidally Prepared Platinum Nanoparticles

The influence of organic ligands on the geometric and electronic surface properties of colloidally prepared Pt nanoparticles (Pt NPs) was investigated by means of diffuse reflectance infrared spectroscopy (DRIFTS) and using CO as probe molecule. Dodecylamine (DDA) and dodecylthiol (DDT) were used as surface functionalizing ligands that exhibit the same hydrocarbon tail but different functional groups. While for DDA an electronic donor effect as well as a geometric effect was found, the effect of DDT was mainly geometric in nature. For high DDA and DDT coverages, on-top sites were blocked for CO adsorption to a higher extent than bridge and threefold hollow sites. Whereas DDA is only weakly adsorbed and displaced by strongly binding adsorbates (e.g., CO), DDT is strongly attached to the particle surface forming an evenly distributed capping layer. With decreasing thiol coverage, blocking of bridge and threefold hollow sites became more pronounced than on-top site blocking. The influence of both ligands on the selectivity of the hydrogenation of crotonaldehyde catalyzed by Pt NPs was investigated. For amino-functionalized NPs the catalytic properties did not differ from that of “unprotected” Pt NPs. In contrast, an increased selectivity can be found for thiol-functionalized particles, which, according to the IR-spectroscopic investigations, was attributed to a geometric modification of the surface by the ligand.

Colloidally prepared platinum nanoparticles deposited on iron oxide studied by XAFS

Colloidal chemistry is an attractive method for the preparation of metal nanoparticles with well-defined shape and size rendering. This preparation technique is particularly interesting for the fabrication of heterogeneous catalysts, where size and shape play a key role for the catalytic properties. Nevertheless, the metal nanoparticles synthesized by colloidal approaches are often surrounded by a shell of organic ligands stabilizing the particles during the growth process. The influence of the ligands on the interaction with the support and the catalytic reaction was studied by x-ray absorption spectroscopy (XAS). It was found that the activity of the metallic Pt nanoparticles previously protected by organic ligands is higher in CO reaction than for unprotected nanoparticles deposited on iron oxide.

A miniaturized catalytic gas sensor for hydrogen detection based on stabilized nanoparticles as catalytic layer

Micro-technologically based catalytic gas sensors offer great advantages regarding sensitivity, power consumption and response time, especially in connection with a porous catalyst layer, which however often provides no sufficient long-term stability. This paper presents a miniaturized catalytic gas sensor for hydrogen detection based on colloidally prepared platinum nanoparticles as a catalytic layer. Compared to conventional sensors, the sensitivity of the catalytic layer is increased while the amount of catalytic material is decreased, due to the high surface of nanoparticles and the direct contact to the sensor. Because of the susceptibility of the nanoparticles to thermally induced sintering, an approach is adopted where the nanoparticles are embedded in an organic network, consisting of stabilizing surfactants adsorbed on the nanoparticle's surface. Agglomeration is reduced and the adhesion to the substrate is improved so that a highly improved stability compared to sensors fabricated with nanoparticles without surfactants is observed. Additionally, the sensor design allows a precise control of the temperature of the catalyst, which also contributes to the stability by keeping the temperature constant. Thermal loading effects are avoided. A sensitivity of up to 2.5mV/100ppm was observed.

Pyrolysis of chloroplatinic acid to directly immobilize platinum nanoparticles onto multi-walled carbon nanotubes

Platinum nanoparticles supported on multi-walled carbon nanotubes (Pt/MWCNTs) were first prepared by simple pyrolysis of H2PtCl6 solution. The structure of Pt/MWCNTs was characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), and the results showed that the diameter of the obtained platinum nanoparticles immobilized on MWCNTs was below 50 nm, although the obtained platinum nanoparticles were not well uniformly dispersed on the surface of MWCNTs. The electrocatalytic performance of Pt/MWCNTs electrode for methanol oxidation reaction (MOR) was also investigated by linear sweep voltammetry (LSV), indicating that it was possible to employ the obtained platinum nanoparticles as anode material in fuel cell. Developing a novel and simple method to prepare platinum nanoparticles onto MWCNTs is the main contribution of this letter.

Pre-prepared platinum nanoparticles supported on SBA-15 – preparation, pretreatment conditions and catalytic properties

The primary objective of this paper is the complete characterization of Pt/SBA-15 catalysts prepared by sonication aided impregnation. During the experiments (i) the influence of sonication applied for introducing the already prepared platinum nanoparticles into the pores of the silica support, (ii) the pressure used for preparing the tablets and/or wafers for catalytic test, (iii) the temperature of heat treatment on the structural changes of catalyst samples, (iv) the effect of platinum particle concentration, and (v) the removal of rest organic matter from the catalysts by different procedures were systematically studied. The samples were characterized by nitrogen adsorption/desorption measurements (BET), TEM, SAXS, XRD and IR. The catalytic activity of the samples was also investigated in the reaction of cyclohexene hydrogenation.

Electrochemical deposition of platinum nanoparticles on carbon: a study by standard and anomalous X-ray diffraction.

This paper is devoted to an alternative method to characterize platinum nanoparticles: X-ray powder diffraction with synchrotron radiation in classical and anomalous dispersion modes. We could straightforwardly determine the mean diameter and the surface concentration of carbon-supported platinum nanoparticles, even down to diameters of 2-3 nm and catalyst amounts of 0.03 mgcm(-2). We could study early stages of the formation of electrochemically prepared platinum nanoparticles from [PtCl4(2-) species preadsorbed on carbon inside a carbon-Nafion layer, to obtain a fuel-cell electrode. Our X-ray diffraction (XRD) results demonstrate that, provided the superficial concentration is not too high, new and smaller particles appear for each current pulse, since there is not any strong nucleation limitation for the high overvoltages obtained. Hydrogen evolution becomes the main electrochemical phenomenon on particles of sufficient size and it explains the noteworthy size limitation. Better yields of Pt metal are obtained for smaller current densities and longer times: the rate-determining step is then not electrochemical, but chemical or related to superficial diffusion.