PtO2 Nanoparticles Research Articles

Innovative nano-shielding for minimizing stray radiation dose in external radiation therapy: A promising approach to enhance patient safety

This study investigates the effectiveness of novel nanocomposite shielding materials in reducing out-of-field radiation doses during radiation therapy, employing Geant4 Monte Carlo (MC) simulations alongside an anthropomorphic female phantom. The research focuses on two radiation modalities: 6 MV beams with and without flattening filters. Utilizing the Geant4 MC code, detailed simulations of a Varian Clinac 2100C/D linear accelerator and an ICRP-145 mesh-type human phantom were conducted to estimate the doses to out-of-field organs from unintended secondary radiation. This involved simulating a comprehensive linac model, including all relevant beam-line components, and assessing the shielding effects of three different nanocomposites doped with metal nanoparticles at various thicknesses. The nanocomposites, comprising Polytetrafluoroethylene (PTFE), with PtO2, IrO2, and Bi2O3 nanoparticles, were evaluated for their potential to reduce patient organ doses from stray photon doses. The results showed that these materials could significantly lower radiation exposure to non-target tissues.

Highly sensitive and selective nanoengineered PtO2-BNNT heterostructures for ppb level ammonia gas sensing

Ammonia is a frequently used gas in many industrial sectors which is both poisonous and highly corrosive to our human environment. In this study, boron nitride nanotubes (BNNTs) decorated PtO2 nanoparticles (NPs) were used to form a heterojunction for enhancing the room temperature (RT, 28 °C) gas sensing towards dry NH3 gas varying from 0.05 to 10 ppm. The BNNT was synthesized by boron oxide-assisted chemical vapor deposition (BOCVD). The fabrication of PtO2-BNNT heterostructures was done by RF sputtering of Pt NPs and subsequent deposition of BNNTs using slurry casting and annealing. The existence of BNNT-PtO2 heterostructure was confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and energy spectroscopy (EDS) compositional analysis. The integration of PtO2 NPs onto BNNTs provides a synergistic effect, enabling enhanced NH3 sensing capabilities. According to the results, the response time of the PtO2-BNNT sensor to -decorated BNNT sensor to 1 ppm NH3 is 19 s with a low detection limit of 5 ppb NH3 as compared to the pristine PtO2 sensor. Extended modulation of conduction channels by BNNTs functionalized with PtO2 facilitated the large sensor response and selectivity of PtO2–BNNTs sensor with high repeatability, excellent resistance against humidity, and long-term stability.

Platinum(IV) Carbonato Complexes: Formation via the Addition of CO2 to the [Pt(OH)6]2- Anion and Generation of Platinum(IV) Oxide Nanoparticles for the Preparation of Catalysts.

A combination of multinuclear nuclear magnetic resonance spectroscopy and theoretical calculation based on density functional theory was used for a speciation study of Pt in solutions prepared either by the interaction of [Pt(OH)6]2- with gaseous CO2 in an alkaline solution of platinum(IV) hydroxide ([Pt(OH)4(H2O)2]) or by the dissolution of [Pt(OH)4(H2O)2] in an aqueous KHCO3 solution. The formed solutions contained coexisting Pt(IV) carbonato complexes with κ1- and κ2-coordination modes. The gradual condensation of mononuclear Pt species in such bicarbonate solutions resulted in the formation of PtO2 nanoparticles aggregating into a solid precipitate on prolonged aging. The deposition of PtO2 particles from bicarbonate solutions was adapted for the preparation of Pt-containing heterogeneous catalysts: bimetallic Pt-Ni catalysts were prepared using various supporting materials (CeO2, SiO2, and g-C3N4) and tested for the activity in hydrazine-hydrate decomposition. All prepared materials showed high selectivity with respect to H2 production from the hydrazine-hydrate with PtNi/CeO2 showing the highest rate of H2 evolution. In the long-range evaluation, the PtNi/CeO2 catalyst operating at 50 °C showed an exceptional turnover number value of 4600 producing hydrogen at a 97% selectivity level and with a mean turnover frequency value of about 470 h-1. In the case of the PtNi/g-C3N4 catalyst, for the first time, the photodriven decomposition of hydrazine-hydrate was shown to enhance the productivity of the catalyst by 40%.

Photocatalytic H2 generation from ethanol and glucose aqueous solutions by PtOx/TiO2 composites

A new straightforward protocol for the deposition of the platinum oxide (PtO–PtO2) particles onto the TiO2 semiconductor via controllable hydrolysis of the sulfuric acid solution of Pt(IV) hydroxide was developed. The developed approach represents a simple and “green” way to prepare the supported Adams-type catalysts. In the constructed composites (PtO2·xH2O/TiO2) the Pt ionic species (hydrated PtO and PtO2 nanoparticles) weakly interact with the titania surface, but under heating the Pt–O–Ti bonds are established, resulting in the stabilization of the Pt(II) ionic state. This state dominates in the obtained catalysts PtOx/TiO2 with a low platinum loading, while at a higher Pt content the metallic Pt particles also appear. The prepared PtOx/TiO2 photocatalysts have been successfully tested in the production of hydrogen under UV light from aqueous solutions of ethanol and glucose, the products of starch biomass processing. Appreciable activity in the production of hydrogen from water/ethanol mixtures was achieved, even at a Pt content of up to 0.05%. PtOx/TiO2 photocatalysts with Pt content of 0.2–0.4 wt% have been successfully used to produce hydrogen from aqueous glucose solutions, and PtOx(0.29)/TiO2 photocatalyst has demonstrated an exceptionally high rate of H2 production per gram of platinum introduced and the quantum efficiency comparable to the highest published values.

Synthesis, Characterization, and Application of Pt/PtO2-TiO2/SiO2 Materials on a Continuous Flow Packed Bed Microreactor for Enhanced Photocatalytic Activity under Sunlight

The present work aimed at the development of Pt-TiO2/SiO2 materials applied to the degradation of a pharmaceutical pollutant in a fixed-bed microreactor in continuous mode. First, a wide investigation of the optimal platinum content in TiO2/SiO2 was carried out based on extensive characterization through XRD, DRS, SEM, TEM, and XPS techniques. For the content range studied, no significant changes were observed in the crystallinity of the material, with peaks related to the anatase phase and PtO2 in the diffractograms. SEM images combined with EDS spectra indicated the presence of platinum and a large heterogeneity in the particles. MET analyses showed PtO2 nanoparticles in close contact with TiO2, allowing the formation of a type II heterojunction. XPS showed platinum in the 0 and +4 oxidation states, suggesting that platinum metal and PtO2 are both present. Regarding the degradation experiments, the optimal catalyst achieved 81% degradation of acetaminophen for a residence time of 1 h, while the catalyst without platinum reached only 27% degradation. The catalyst activity dropped from 81 to 57% in 2 h and remained stable for six reuse cycles. Increasing the inlet flow rate and concentration reduced the pollutant degradation although there was an increase in the reaction rate. Finally, a photocatalytic mechanism was proposed in which a type II heterojunction was developed, with generation of hydroxyl radicals by the positive holes in the VB of TiO2 as well as superoxide radicals by the electrons in the CB of PtO2.

PtO2-decorated MoS2 ultrathin nanostructures for enhanced NH3 gas sensing properties

Recently, transition metal dichalcogenides (TMDs) have attracted much attention due to their high surface-to-volume ratio, various active edge sites, and adjustable bandgaps. However, in general, TMDs still exhibit low gas response and incomplete recovery. Surface modification is an effective way to facilitate the adsorption and desorption processes, thus enhancing the TMD gas sensor's sensing performance. In this study, a PtO2-decorated MoS2 nanostructure gas sensor was fabricated using a chemical reduction process. The result showed that the as-obtained nanostructures consist of accumulated ultrathin MoS2 nanosheets decorated with spherical PtO2 nanoparticles. The gas response of the as-obtained PtO2-decorated MoS2 gas sensor toward NH3 is remarkably high, with 450% upon 500 ppm NH3, which is almost 20 times higher than that of the pristine MoS2 nanostructure gas sensor in their optimal working conditions. The enhancement in gas sensing properties was attributed to the catalytic spillover effect of PtO2 nanoparticles as well as the formation of p-p heterojunction on the MoS2 surface.

In situ time-resolved XAS study on metal-support-interaction-induced morphology change of PtO2 nanoparticles supported on γ-Al2O3 under H2 reduction

Through in situ time-resolved X-ray absorption spectroscopy (XAS), we observed the dynamic behavior of the formation of two-dimensional low-coordinated Pt particles through reduction of PtOx particles by H2, which were under metal-support interaction (MSI) with the γ-Al2O3 support. The relatively stabilized PtOx species were reduced below 373 K, and the interfacial PtOx species on γ-Al2O3 surface were reduced above 373 K. The time-resolved Pt L3-edge XAS revealed that the morphology changed from three-dimensional PtOx particles to two-dimensional low-coordinated Pt particles during the in situ reduction of PtOx/Al2O3 at 473 K, whereas at 373 K, the interfacial PtOx species remained after its reduction. This study demonstrated that in situ time-resolved XAS is one of the most definitive techniques to unveil the MSI effect during the reductive formation process of Pt nanoparticle catalysts loaded on γ-Al2O3.

The intrinsic enzyme mimetic activity of platinum oxide for biosensing of glucose

Given the enzymatic properties and the oxidized surface of Pt nanomaterials, we demonstrated the intrinsic oxidase-like and peroxidase-like activities of platinum oxide (PtO2). The surface clean PtO2 nanoparticles with high water dispersibility were synthesized by a simple and green method. X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) results demonstrated that the prepared PtO2 nanoparticles mainly consisted of Pt (Ⅳ) state without Pt(0) chemical state. The enzymatic activity of PtO2 nanoparticles was verified by catalytic oxidation of several chromogenic substrates. Catalytic mechanism analysis suggested that PtO2 nanopartiles acted as peroxidase and oxidase enzyme mimics by promoting the generation of the reactive oxygen species (ROS). By combining glucose oxidase, a colorimetric assay for glucose detection was developed with the limit of detection of 10.8 μM. The successful application of the proposed detection assay in human serum samples demonstrated the promising practical application in clinical diagnosis, pharmacy and food.

Synergistic effect of mesoporous metal oxides and PtO2 nanoparticles in aerobic oxidation of ethanol and ionic liquid induced acetaldehyde selectivity

We report on the catalytic performance of mesoporous metal oxides (MMOs) as catalysts and as potential supports for platinum (Pt) nanoparticles in aerobic oxidation of ethanol. Synthesis of MMOs was achieved through the hard-template method and the resulting MMOs resembled the 3-D structure of the templating KIT-6. The Pt nanoparticles were templated and stabilized using poly(amidoamide), PAMAM, dendrimer to achieve dendrimer-encapsulated Pt nanoparticles (Pt-DENs) with an average size of 3.5 ± 0.4 nm. All the components of the catalysts (Pt-DENs and MMOs) were first characterized separately and thereafter, followed the preparation of MMO-immobilized Pt nanoparticles. Upon characterization of the MMO-immobilized Pt nanoparticles, the Pt nanoparticle size increased as determined from hydrogen-chemisorption and organothiol-adsorption technique. Furthermore, X-ray photoelectron spectroscopy (XPS) revealed that Pt has an oxidation state of 4+ after removal of the dendrimer at 550 °C signifying an oxide state (PtO2). The hydrogen temperature-programmed reduction (H2-TPR) revealed a change in electronic structure of MMOs as reduction peaks shifted to lower temperatures upon immobilization of PtO2 nanoparticles. This change in electronic structure of the mesoporous metal oxides upon immobilization of PtO2 nanoparticles is found to be one of the reasons for enhanced catalytic activity. Improved selectivity towards acetaldehyde was induced by introduction of an ionic liquid layer in a solid catalyst with ionic liquid layer, SCILL concept. Furthermore, the amount of ionic liquid coating plays a pivotal role in impacting selectivity and has an impact in the reaction turnover frequency.

Study of active surface centers of Pt/CeO2 catalysts prepared using radio-frequency plasma sputtering technique

RF-plasma deposition of Pt on a nanosized ceria powder support has been performed directly in photoelectron spectrometer chambers to prepare model catalysts. The plasma deposition in an oxidizing environment results in the formation of highly dispersed oxide nanoparticles up to 2 nm large, which contain platinum solely as Pt4+ ions revealed by Eb(Pf4f7/2) = 74.6 eV. Thus prepared model catalyst samples arranged as (sub-monolayer) films of PtO2 nanoparticles on the surface of CeO2 are characterized by an increased thermal stability compared with PtO2 nanoparticles deposited on more inert supports. These PtO2/CeO2 model catalysts show a high activity in the CO oxidation even at room temperature. A detailed analysis of the O1s spectra obtained during the titration by CO of PtO2/CeO2 films strongly suggests that the reactive oxygen species are manifested with Eb(O1s) = 530.8 eV and 532.9 eV. The latter core level energies are attributed to oxygen in the platinum dioxide and to peroxide-like oxygen, presumably located at the interface between PtO2 and CeO2 particles. Results of our density-functional calculations indicate that the peroxide-like species can be energetically stabilized at the PtOx–CeO2 interfaces.

Roles of catalytic PtO2 nanoparticles on nitric oxide sensing mechanisms of flame-made SnO2 nanoparticles

In this work, PtO2-loaded SnO2 nanoparticles containing 0–2 wt% Pt produced in a single step by flame spray pyrolysis (FSP) technique were systematically evaluated for nitric oxide (NO) detection. Characterizations by various X-ray/electron microscopic and spectroscopic analyses confirmed the formation of PtO2 nanoparticles dispersed on SnO2 surfaces. The sensing films were fabricated by spin-coating and the gas sensing performances were studied towards NO at the operating temperatures ranging from 25 to 350 °C in dry air. It was found that the optimal Pt concentration of 0.2 wt% led to the highest sensor response of 2640 toward 5 ppm NO at the optimal operating temperature of 150 °C, which was about five times higher than that of unloaded one. In addition, the response rate analysis revealed the highest catalytic activity of PtO2 towards NO at 0.2 wt% Pt. Moreover, the PtO2-loaded SnO2 sensor offered improved NO selectivity against NO2, NH3, H2S, C2H5OH and H2. Therefore, the incorporation of PtO2 to SnO2 nanoparticles by FSP is a promising mean to achieve responsive and selective detection of NO and can be useful for various environmental and biomedical applications.

Photoinduced in Situ Deposition of Uniform and Well-Dispersed PtO2 Nanoparticles on ZnO Nanorods for Efficient Catalytic Reduction of 4-Nitrophenol.

Based on the photochemical property of semiconductors, a light irradiation-assisted strategy has been designed using one-dimensional ZnO nanorods as carriers to synthesize the rod-type PtO2/ZnO catalyst with a well-defined structure. The high crystallinity and uniform crystal structure of the ZnO matrix conduct the in situ deposition of PtO2 nanoparticles with 1.1-2.1 nm, which are evenly and densely anchored on the surface. Those small-sized and well-dispersed PtO2 nanoparticles endow the PtO2/ZnO catalyst a superior catalytic performance for the reduction of 4-nitrophenol to 4-aminophenol, which can convert all the substrates within 6.25 min. It is demonstrated that the catalytic activity of the PtO2/ZnO catalyst is 2.3 times as high as that of the sample obtained by traditional wet-oxidation method under the same reaction conditions. Moreover, the light-irradiation time has been found to greatly affect the structure and activity of PtO2/ZnO catalysts, and the product with 30 min exhibits the best catalytic performance in this work, as well as the good stability for ten runs. In terms of the photoexcited process of ZnO and reactive species-trapped experiments, the formation mechanism of PtO2/ZnO catalysts has been explored in detail, which will probably stimulate the design and study of other metal-supported catalysts.

Sources and Typomorphism of Platinum in Carbonaceous Rocks in Far East Russia

Results of the study of carbonaceous metasedimentary rocks in the northern part of the Khanka and eastern part of the Bureya massifs (Primorye and Khabarovsk territories, JAR) and associated platinum mineralization are presented. It is shown that platinum minerals are represented by microparticle dispersion in shales of the greenschist-facies metamorphism (Sutyr and Kimkan sequences, Mitrofanovo Formation) and by Pt and PtO2 nanoparticles associated closely with graphite in shales of the amphibolite facies (Turgenev and Soyuznoe graphite deposits). The studied carbonaceous sequences were likely formed in the hemipelagic setting in a suprasubduction trench during the intense input of terrigenous material into basin. Carbon was derived from the marine biogenic material and superimposed graphitization related to a lower crustal material. Iron ores in the carbonaceous shales are hydrothermal formations. Platinum mineralization was likely related to two sources: (i) sedimentary-chemogenic source that made up the protolith of graphite–sericite–quartz shales of the Sutyr and Kimkan sequences (Mitrofanovo Formation); (ii) graphitizing fluid generated in deep magma chambers. Mineralization produced from these sources is transformed during the hydrothermal activity (coarsening of microparticles) and/or regional metamorphism (disintegration of microparticles and remobilization of Pt into graphite).

PtO2-nanoparticles functionalized CuO polyhedrons for n-butanol gas sensor application

The CuO polyhedrons functionalized with different amounts of PtO2 nanoparticles were synthesized by simple two-step method. The gas sensing properties of the sensors prepared by PtO2 functionalized CuO polyhedron were studied and compared with pure CuO sensors. The electrical sensitivity values show that the response of S2-CuO (3.5%wt PtO2-CuO) polyhedron is higher than that of pure CuO polyhedron in n-butanol/air atmosphere. The sensor showed excellent reproducibility and good selectivity to n-butanol gas, and its working temperature was relatively low (180 °C), and the reaction time quickly reached 2.4 s. The enhanced properties are attributed to the structure of the CuO polyhedron and the synergistic effect of CuO and PtO2.

Platinum dioxide activated porous SnO2 microspheres for the detection of trace formaldehyde at low operating temperature

Great efforts have been devoted on the detection of the volatile organic compounds indoor for human health. The detection of formaldehyde is one of the most important and popular issues for the wide usage of formaldehyde and its toxic. However, it is a challenge to monitor trace gaseous formaldehyde at lower working temperature. Herein, we present a sensor with a significantly improved sensing response and dramatically decreased operating temperature based on porous PtO2/SnO2 microspheres. And the PtO2/SnO2-5 mol% composite shows the most outstanding sensing performance among all products. What’s more, the above sensor can detect gaseous formaldehyde in the ppb level (100ppb) at low operating temperature (100°C). The excellent sensing performance should be attributed to the high catalytic activity of PtO2 nanoparticles decorated on the surface of SnO2 microspheres and the porosity of the composite.

Highly Oxidized Platinum Nanoparticles Prepared through Radio‐Frequency Sputtering: Thermal Stability and Reaction Probability towards CO

Platinum-oxide nanoparticles were prepared through the radio-frequency (RF) discharge sputtering of a Pt electrode in an oxygen atmosphere. The structure, particles size, electronic properties, and surface composition of the RF-sputtered particles were studied by using transmission electron microscopy and X-ray photoelectron spectroscopy. The application of the RF discharge method resulted in the formation of highly oxidized Pt(4+) species that were stable under ultrahigh vacuum conditions up to 100 °C, indicating the capability of Pt(4+) -O species to play an important role in the oxidation catalysis under real conditions. The thermal stability and reaction probability of Pt(4+) oxide species were analyzed and compared with those of Pt(2+) species. The reaction probability of PtO2 nanoparticles at 90 °C was found to be about ten times higher than that of PtO-like structures.