Pt-rich Nanoparticles Research Articles

Transformation by plasma technology of cisplatin found in hospital's wastewaters into platinum-containing nanoparticles

Platinum-containing molecules such as cisplatin figure among oncology's most widely used antineoplastic agents. Cisplatin excreted in the urine usually ends up in municipal wastewater, with a strong toxicological and carcinogenic impact on the environment. Thus, cisplatin should be inactivated before reaching wastewater to attenuate its environmental impact. However, conventional recommended procedures use large quantities of toxic acids, which are not sustainable processes. In this study, a dielectric barrier discharge (DBD) atmospheric pressure plasma reactor is used to degrade cisplatin in wastewater, allowing platinum's recuperation. The article describes the plasma discharge (power, electron temperature, and density) and confirms the most stable operation parameters under Ar and Ar+H2 discharges. Cisplatin is diluted in water or synthetic urine, and plasma treatment is conducted for 30 min. The process degrades cisplatin molecules by conversion into platinum-rich nanoparticles (NPs). These nanoparticles are efficiently recuperated by centrifugation and are characterized by transmission electron microscopy and X-ray photoelectron spectroscopy (XPS). The mass-balance assessment confirms that more than 90% of cisplatin is degraded and recuperated as Pt-rich NPs.

Magmatic platinum nanoparticles in metasomatic silicate glasses and sulfides from Patagonian mantle xenoliths

Platinum-rich nanonuggets (s.l., nanoparticles) are commonly produced in experiments attempting to quantify the solubility or partitioning of noble metals in silicate and sulfide melts. However, it has been thought that these represent artifacts produced during quenching of the experimental runs. Here, we document nanoparticles (~ 20–80 nm) of Pt-rich alloys and arsenides dispersed in high-temperature metasomatic silicate glasses and in base-metal sulfides (BMS) entrained in them, found interstitially between minerals of mantle peridotite xenoliths from southern Patagonia. Pt-rich nanoparticles found in the interstitial silicate glasses are frequently attached to, or in the proximities of, oxides (ilmenite or Cr-spinel) suggesting a close link between the formation of the oxides and the Pt-rich nanoparticles. The interstitial glasses in the studied xenoliths correspond to quenched alkaline basaltic melts that infiltrated the subcontinental lithospheric mantle (SCLM) at > 1000 °C at an oxygen fugacity (fO2) near the fayalite–magnetite–quartz (FMQ) buffer. Experimental works indicate that at these conditions the crystallization of oxides such as ilmenite or Cr-spinel may lower fO2 to promote the precipitation of Pt-rich nanoparticles. The investigation of four Pt-rich nanoparticles hosted in two different pentlandite grains using a combination of focused ion beam and high-resolution transmission electron microscopy (FIB/HRTEM) show that these nanoparticles consists of polycrystalline aggregates < 10 nm that are randomly oriented relative to their sulfide host matrices. These observations suggest that these nanoparticles could be segregated either directly from the infiltrating alkaline basaltic melt prior to sulfur saturation in the silicate melt, or from droplets of immiscible sulfide melt once sulfur saturation was achieved. The formation of Pt-rich nanoparticles in high-temperature melts, either silicate or sulfide, provides new clues on the processes of fractionation, transport and concentration of Pt in the mantle.

Nanostructured Pd[sbnd]Pt nanoparticles: evidences of structure/performance relations in catalytic H2 production reactions

A widespread approach to modulate the performances of heterogeneous catalysts is the use of bimetallic nanoparticles (NPs) as the active phase. However, studying the relationship between the NPs structure and catalytic properties requires well-defined systems, having uniform composition, size and nanostructure, which cannot be achieved by traditional methods (e.g. impregnation). Here, we developed wet-chemistry synthetic routes to prepare PdPt NPs or Pt-core@Pd-shell NPs of small size and well-controlled composition and structure, protected by mercaptoundecanoic acid (MUA) moieties. The pristine NPs were tested for H2 production by NH3BH3 hydrolysis, in order to systematically investigate the effect of composition and of synthetic route on the activity of the systems. Depending on the preparation method, two distinct trends of activity were observed, rationalized in terms of the extent of surface functionalization by MUA. The MUA protective layer was found to effectively stabilize the NPs dispersion while maintaining high activity in certain cases (Pt-rich NPs), and was demonstrated to be essential for catalyst recycling. In order to further study structure-activity relationships of PdPt NPs after ligand removal, nanostructured PdPt@CeO2-based catalysts were prepared by self-assembly route. Regardless of the starting NPs structure (alloy or core-shell), similar water gas shift reaction performances were observed, due to the structural rearrangements occurring upon oxidation and reduction thermal treatments, which led to the formation of Pt-rich core@PdPt-shell under reducing conditions.

Toward High-Performance Pt-Based Nanocatalysts for Oxygen Reduction Reaction through Organic–Inorganic Hybrid Concepts

Pt-based multistructured nanocatalysts such as alloy, core–shell, and surface Pt-rich nanoparticles have been extensively studied for hydrogen fuel cell applications, and their catalytic performances for oxygen reduction reactions have been significantly upgraded for decades. Due to these technical enhancements, Pt-based nanoarchitectures have turned out to be compatible with commercially accessible fuel cell systems. In addition, based on physical and electrochemical backgrounds for the basic catalyst nanoarchitectures, novel catalyst designs with organic–inorganic hybrid concepts have been recently developed to more effectively improve the electrochemical reaction activities and durabilities. In this review, the typical class of Pt-based nanocatalysts are systematically explained according to their compositions and structures, and the emerging class of organic–inorganic hybrid catalyst designs are then thoroughly introduced. It is expected that the most recent improvements of Pt-based nanoarchitectures ...

Preparation of carbon black supported Pd, Pt and Pd–Pt nanoparticles using supercritical CO 2 deposition

The preparation of carbon black (Black Pearl 2000) supported single Pd, Pt and bimetallic Pd–Pt nanoparticles utilizing the supercritical CO 2 deposition method was investigated. Palladium (II) acetylacetonate (Pd(acac) 2) and dimethyl (cyclooctadiene) platinum (II) (Pt(cod)me 2) were utilized as metallic precursors. The adsorption isotherms of Pd(acac) 2 and Pt(cod)me 2 on BP2000 in scCO 2 at 20 MPa and 60 °C were determined. A mass transfer model was found to represent the experimental data on the kinetics of adsorption of Pd(acac) 2 onto BP2000 in scCO 2 fairly well with a fitting error of 5.6%. In order to prepare the supported nanoparticles, chemical reduction with H 2 in scCO 2 was utilized. Increasing reduction temperature and metal loading caused an increase in Pd particle size. The Pd particles were irregularly distributed and the size range of the particles was 3–100 nm, whereas Pt nanoparticles were homogeneously distributed with a size range of 2–6 nm. Binary metal nanoparticles could also be produced by simultaneous adsorption and subsequent reduction of the precursors. It was found that addition of Pt increased the homogeneity and reduced the particle size on the support compared to single Pd nanoparticles. From the X-ray spectrometry data, it was seen that there was a heterogeneous mixture of the bimetallic nanoparticles. Pt-rich nanoparticles had diameters of around 4 nm, whereas Pd-rich nanoparticles were larger with diameters of around 10 nm.

Synthesis and properties of Co–Pt alloy silica core-shell particles

This paper describes a method for fabrication of silica-coated Co–Pt alloy nanoparticles in a liquid phase process. The Co–Pt nanoparticles were prepared from CoCl2 (4.2 × 10−5 M), H2PtCl6 (1.8 × 10−5 M), citric acid (4 × 10−4 M) and NaBH4 (1.2 × 10−2 M) with a Co:Pt mole ratio of 7:3. The silica coating was performed in water/ethanol solution with a silane coupling agent, 3-aminopropyltrimethoxysilane (8 × 10−5 M), and a silica source, tetraethoxyorthosilicate (7.2 × 10−4 M) in the presence of the Co–Pt nanoparticles. Observations with a transmittance electron microscope and a scanning transmission electron microscope revealed that the Co-rich and Pt-rich nanoparticles were coated with silica. According to X-ray diffraction measurements, core particles were crystallized to metallic Co crystallites and fcc Co–Pt alloy crystallites with annealing in air at 300–500 °C. Magnetic properties of the silica-coated particles were strongly dependent on annealing temperature. Maximum values of 11.4 emu/g-sample for saturation magnetization and 365 Oe for coercive field were obtained for the particles annealed at 300 and 500 °C, respectively. Annealing at a temperature as high as 700 °C destroyed the coating structures because of crystallization of silica shell, resulting in reduction in saturation magnetization and coercive field.