Platinum Group Research Articles

Sensitive Colorimetric Lateral Flow Assays Enabled by Platinum-Group Metal Nanoparticles with Peroxidase-Like Activities.

The last several decades have witnessed the success and popularity of colorimetric lateral flow assay (CLFA) in point-of-care testing. Driven by increasing demand, great efforts have been directed toward enhancing the detection sensitivity of CLFA. Recently, platinum-group metal nanoparticles (PGM NPs) with peroxidase-like activities have emerged as a type of promising colorimetric labels for enhancing the sensitivity of CLFA. By incorporating a simple and rapid post-treatment process, the PGM NP-based CLFAs are orders of magnitude more sensitive than conventional gold nanoparticle-based CLFAs. In this perspective, the study begins with introducing the design, synthesis, and characterization of PGM NPs with peroxidase-like activities. The current techniques for surface modification of PGM NPs are then discussed, followed by operation and optimization of PGM NP-based CLFAs. Afterward, opinions are provided on the social impact of PGM NP-based CLFAs. Lastly, this perspective is concluded with an outlook of future research directions in this emerging field, where the challenges and opportunities are discussed.

Geochemical evidence for a chondritic impactor in altered impact glass from the Stac Fada Member impactite, NW Scotland

The Stac Fada Member (Stoer Group) is a ∼1.2 Ga melt-rich impact breccia whose source crater and, therefore, proximity remains debated. We present a detailed in situ geochemical dataset for altered impact melt clasts within Stac Fada samples from Bay of Stoer and Second Coast. These altered impact melt clasts are now predominantly composed of clinochlore. Geothermometry of this clinochlore indicates formation temperatures within the ejecta blanket at 188–231°C, in agreement with previous estimates. A positive correlation between platinum group elements Ir, Pt and Rh – apparently independent of Ni – indicates two geochemical sources for platinum group elements enrichment. We propose that these represent an Mg–Ni-rich chondritic impactor and a mafic/ultramafic-layered body within the target lithology. Spatial variation in Ni content suggests that geochemical data, in combination with field observations, may be instrumental in assessing the likely location of the impact crater.

Design and Production of Functionalized Electrospun Fibers for Palladium Recovery.

Adsorption stands out as a leading wastewater treatment method for ion removal or recovery. Polymeric fibers, notably electrospun ones, are gaining prominence due to their high capacity and easy recovery. Electrospinning offers a cost-effective means to produce fibers with a large surface area and high adsorption capacity. These fibers can be further functionalized with chemical substances acting as specific ligands for metal ions, bolstering their adsorption capabilities. In this study, dithioester-functionalized electrospun fibers were synthesized as an alternative to conventional sorbents for palladium recovery from acidic chloride solutions, similar to those used in hydrometallurgical processes for platinum group metal recovery (Pd, Pt, Rh···) from spent catalysts. Fibers with identical chemical composition but varying morphology were examined to assess their impact on palladium adsorption efficiency (i.e., beads-free and beads-on-string morphologies). Experimental investigations involved model solutions with varying palladium concentration, temperature, acidity (adjusted with HCl content), and salinity (adjusted with NaCl), utilizing both pure and dithioester-functionalized fibers. Experimental results demonstrate enhanced adsorption efficiency at lower temperatures and in 0.1 M HCl, with a negligible influence from solution salinity. Moreover, both pure polymeric and dithioester-functionalized electrospun fibers exhibit highly efficient palladium recovery. Furthermore, under optimal conditions, starting from an 80 mg/L palladium solution, a 95% recovery of palladium can be achieved with a sorbent dosage below 4 g/L of functionalized electrospun fibers. The adsorption data are well described by the Langmuir isotherm model for the pure polymeric fibers. At the same time, the contribution of dithioesters has been separately accounted for to describe the behavior of functionalized electrospun fibers. Thermal recovery of palladium from the spent sorbents has also been investigated.

Metamorphic origin of large nuggets of platinum-group metals: evidence from multiphase inclusions in Os-Ir-Ru alloys from the Adamsfield placer, Tasmania

Abstract Platinum-group elements (PGE) are most effectively concentrated via sulfide-silicate melt immiscibility; however, under sulfide-undersaturated conditions, PGE may exhibit highly-siderophile behaviour and occur as native metals and alloys. In this case, they can form μm-size inclusions within Cr-spinel, but also large nuggets (up to several kilograms), found in chromitites and related placer deposits. The exact formation mechanism of such large nuggets and accumulations of PGE unrelated to sulfide melts remains controversial due to mass balance issues. In this study of multiphase inclusions in Os-Ir-Ru nuggets from the Adamsfield placer district (Tasmania, Australia), we constrain their crystallization environment. Multiphase inclusions comprise variable proportions of hornblende, enstatite, quartz, anthophyllite, anorthite, chlorite and native iridium and coexist with single-phase olivine and Cr-spinel inclusions. The heterogeneity in phase and chemical composition of the inclusions indicates a complex origin from an inhomogeneous source media. This is corroborated by grain scale disequilibrium mineral assemblages, where forsterite and quartz are both included within a single osmium grain. Our proposed multi-stage origin of Adamsfield Os-Ir-Ru nuggets involved magmatic olivine-Cr-spinel-Os-Ir-Ru cumulates in peridotite bodies that were subsequently overprinted by various hydrothermal and metamorphic processes, including serpentinization or growth of Os-Ir-Ru from supercritical fluids. The final metamorphic stage resulted in the obliteration of Os-Ir-Ru zonation, culminating in the current assemblage of inclusions.

The Application of Atomic Spectroscopy Techniques in the Recovery of Critical Raw Materials from Industrial Waste Streams, Part II

This month’s column is Part 2 of a contribution from my daughter Glenna, who recently completed her PhD studies in Environmental Science from the University of Copenhagen in Denmark. Her article explores the current landscape of global critical raw materials (CRM) trends in research and the applications of atomic spectroscopy (AS), including inductively coupled plasma–mass spectrometry (ICP-MS), inductively coupled plasma–optical emission spectrometry (ICP-OES), and X-ray analytical techniques in their identification of diverse industrial and environmental media, which have been essential in method validation and quantification of CRMs in complex matrices presenting high risks of interference. Some important examples to be presented include rare earth elements (REEs) in water leaching purification (WLP) residues that co-occur with radioactive materials; REEs and other metals in acid mine drainage (AMD) environments; REEs in coal combustion (fly ash) residues; arsenic (As) from groundwater treatment sediment; and platinum-group elements (PGEs) from sewage sludge. The article also classifies the different techniques in use at each stage of the CRM recovery train, investigates present challenges to each analytical method, and discusses the problem-solving tools used.

Decoupling the effect of hydraulic oil contamination on the flotation performance of UG2 PGE ore and its interaction with alteration minerals

Oil contamination inadvertently arising from underground mechanised South African platinum mines is known to compromise the subsequent flotation performance. Anecdotal observations suggest that this is further exacerbated in the presence of phyllosilicate alteration minerals. Two ores of varying degrees of alteration from the Bushveld Igneous Complex were utilized in this study to investigate the effects of oil on UG2 platinum group element (PGE) ore flotation and investigate the interaction mechanisms between the oil and phyllosilicate alteration minerals. Mineralogical characterization of the ores indicated a higher percentage of the alteration phyllosilicate minerals in the altered ore (9.2 wt%) in comparison to the normal ore (5.6 wt%); with talc predominating in both ores. Baseline batch flotation test work indicated a reduction of grade with hydraulic oil addition in the normal ore (Pt by 4.5 g/t and Pd by 3.6 g/t), whereas valuable metal grades in the altered ore showed no change. In contrast to the grades, the Pt and Pd recovery dropped by 6 % and 12 %, respectively, in the altered ore floats whereas nearly constant recoveries were obtained for the normal ore as oil concentration increased. The dynamic froth stability and slurry viscosity both increased in the presence of oil and were greater in the altered ore compared to the normal ore. The observed flotation performance of the normal ore was attributed to the increasing froth stability which promoted the recovery of gangue minerals and consequent grade decrease. For the altered ore, the greater increase in the slurry pulp viscosity with oil addition was proposed to lead to poor gas dispersion and reduced interaction between bubbles and particles resulting in the reduction of recovery. The addition of sodium metasilicate successfully mitigated these effects causing a decrease in the viscosity, improvement in particle dispersion and better froth drainage. This study highlighted the potentially harmful effects of oil spillages from mechanised mining and its complex interaction with alteration minerals contained within the ore.

Anisotropic Heterobimetallic Nanomaterials with Controlled Composition for Efficient Oxygen Reduction at Ultralow Loading

AbstractHydrogen fuel cells represent a leading technology in developing green energy targeting net‐zero emissions goals by mid‐century. However, the sluggish kinetics of the oxygen reduction reaction (ORR) have hitherto demanded substantial quantities of expensive platinum (Pt) group metals. Advances in catalyst design, including the controllable fabrication of highly branched morphologies to increase the surface area‐to‐volume ratio, intermixing Pt with more affordable transition metals, and controlling composition, offer solutions that can further enhance activity and reduce expense. In this context, Pt/M (M = Fe, Ni, Co) nanopods and nanodendrites with precise composition control using more affordable starting materials are designed and crafted. The method is highly efficient, taking only 30 min and avoiding the need for high‐pressure equipment, making it highly scalable. These catalysts show superior ORR performance at an electrode loading as low as 0.0022 mgPt cm−2. One, nanodendritic Pt/Ni, achieves a mass activity of at 0.9 V versus RHE, making it 87 times more efficient in terms of Pt‐content than a commercial 10 wt% Pt/C nanoparticle standard. These findings provide new opportunities for developing next‐generation, cost‐efficient Pt‐based catalysts, by potentially advancing hydrogen fuel cell technology through performance enhancement and addressing cost challenges through catalyst design.

Efficient CO2 Conversion through a Novel Dual-Fiber Reactor System.

Carbon dioxide (CO2) can be converted to valuable organic chemicals using light irradiation and photocatalysis. Today, light-energy loss, poor conversion efficiency, and low quantum efficiency (QE) hamper the application of photocatalytic CO2 reduction. To overcome these drawbacks, we developed an efficient photocatalytic reactor platform for producing formic acid (HCOOH) by coating an iron-based metal-organic framework (Fe-MOF) onto side-emitting polymeric optical fibers (POFs) and using hollow-fiber membranes (HFMs) to deliver bubble-free CO2. The photocatalyst, Fe-MOF with amine-group (-NH2) decoration, provided exceptional dissolved inorganic carbon (DIC) absorption. The dual-fiber system gave a CO2-to-HCOOH conversion rate of 116 ± 1.2 mM h-1 g-1, which is ≥18-fold higher than the rates in photocatalytic slurry systems. The 12% QE obtained using the POF was 18-fold greater than the QE obtained by a photocatalytic slurry. The conversion efficiency and product selectivity of CO2-to-HCOOH were up to 22 and 99%, respectively. Due to the dual efficiencies of bubble-free CO2 delivery and the high QE achieved using the POF platform, the dual-fiber system had energy consumption of only 0.60 ± 0.05 kWh mol-1, 3000-fold better than photocatalysis using slurry-based systems. This innovative dual-fiber design enables efficient CO2 valorization without the use of platinum group metals or rare earth elements.

A catalyst family of high-entropy alloy atomic layers with square atomic arrangements comprising iron- and platinum-group metals.

We report a catalyst family of high-entropy alloy (HEA) atomic layers having three elements from iron-group metals (IGMs) and two elements from platinum-group metals (PGMs). Ten distinct quinary compositions of IGM-PGM-HEA with precisely controlled square atomic arrangements are used to explore their impact on hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR). The PtRuFeCoNi atomic layers perform enhanced catalytic activity and durability toward HER and HOR when benchmarked against the other IGM-PGM-HEA and commercial Pt/C catalysts. Operando synchrotron x-ray absorption spectroscopy and density functional theory simulations confirm the cocktail effect arising from the multielement composition. This effect optimizes hydrogen-adsorption free energy and contributes to the remarkable catalytic activity observed in PtRuFeCoNi. In situ electron microscopy captures the phase transformation of metastable PtRuFeCoNi during the annealing process. They transform from random atomic mixing (25°C), to ordered L10 (300°C) and L12 (400°C) intermetallic, and finally phase-separated states (500°C).

Chromitites and associated mineralization of the Akkarga ophiolitic massif in the southeastern Urals (Russia)

The Akkarga ultramafic massif exposed in the Trans-Uralian megazone represents the mantle section of an ophiolite assemblage that was emplaced into the upper crust during the Permian collision. Ultramafic rocks include harzburgites and subordinate dunites that have undergone complete serpentinization and host podiform chromitite bodies typical of the ophiolite complexes worldwide. Numerous lens-shaped and podiform occurrences of massive and densely disseminated chromitites are surrounded by envelopes of serpentinized dunites whereas nodular chromitites and lenticular bodies of banded disseminated ores are of subordinate importance. Three ore zones are distinguished on the massif, including the Western, Central and Eastern, but only the sites of the latter two are currently accessible for study. Chromite from chromitites of the Central Ore Zone has higher Cr# (Cr/Cr + Al) (0.81–0.83) than that of chromitites of the Eastern Ore Zone (Cr# = 0.67–0.80) and accessory chromite of peridotites (Cr# = 0.52–0.75). Chromites contain mineral inclusions, which are distributed unevenly. The most abundant are inclusions of high-Mg high-Ni olivine (Fo94–98 and up to 1.5 wt% NiO) and calcic amphibole, while inclusions of pyroxenes and base metal sulfides are less common. Platinum group minerals (PGMs) in chromitites are represented by alloys, sulfides, and sulfoarsenides, which occur in single-mineral and composite inclusions. Ruthenium and Os disulfides typically compose the euhedral single-mineral inclusions in cores of chromite crystals, whereas the composite inclusions, mostly of irregular shapes, are dominated by Ir compounds. PGMs are regularly associated with OH-bearing silicates such as amphibole and, less frequently, chlorite. The setting, morphology and composition of the inclusions seem to support a leading role of subsolidus solid-state exsolution in the formation of primary laurite-erlichmanite mineralization in Akkarga chromitites. Subsequent hydrothermal reworking of podiform chromitites and their ultramafic hosts, which is likely related to the supra-subduction setting, led to the precipitation of more diverse interstitial assemblages, comprising base-metal sulfides, nickeline, sulfoarsenides of the Ir-subgroup platinum group elements (IPGE), REE phosphates, zircon, barite, and baddeleyite. Later granite intrusions likely provided an additional contribution of fluid-mobile incompatible elements to chromitites.

Dual-Intermetallic Heterostructure on Hierarchical Nanoporous Metal for Highly Efficient Alkaline Hydrogen Electrocatalysis.

Constructing well-defined active multisites is an effective strategy to break linear scaling relationships to develop high-efficiency catalysts toward multiple-intermediate reactions. Here, dual-intermetallic heterostructure composed of tungsten-bridged Co3W and WNi4 intermetallic compounds seamlessly integrated on hierarchical nanoporous nickel skeleton is reported as a high-performance nonprecious electrocatalyst for alkaline hydrogen evolution and oxidation reactions. By virtue of interfacial tungsten atoms configuring contiguous multisites with proper adsorptions of hydrogen and hydroxyl intermediates to accelerate water dissociation/combination and column-nanostructured nickel skeleton facilitating electron and ion/molecule transportations, nanoporous nickel-supported Co3W-WNi4 heterostructure exhibits exceptional hydrogen electrocatalysis in alkaline media, with outstanding durability and impressive catalytic activities for hydrogen oxidation reaction (geometric exchange current density of ≈6.62 mA cm-2) and hydrogen evolution reaction (current density of ≈1.45 A cm-2 at overpotential of 200 mV). Such atom-ordered intermetallic heterostructure alternative to platinum group metals shows genuine potential for hydrogen production and utilization in hydroxide-exchange-membrane water electrolyzers and fuel cells.

Finding and identifying platinum group elements in the Eastman layered mafic intrusion

Platinum group elements (PGEs) are commonly hosted by base metal sulfides (BMSs, e.g. chalcopyrite or pentlandite) or platinum group minerals (PGMs). PGE-bearing phases are generally small, ranging from tens of nanometres to a few micrometres. In addition, PGEs can be hosted in PGMs, either intimately associated with BMSs or spatially separated. This poses a difficulty in their detection and analysis, and leads to uncertainty in identification of their mineral hosts. Their erratic occurrence introduces a substantial nugget effect in bulk rock assays, used to evaluate deposit economics on a larger scale. Knowledge of PGE hosts has a direct influence on resource management and extraction efficiency, making the understanding of mineral distribution important for processing. The Eastman Ultramafic Intrusion is a layered mafic–ultramafic intrusive complex in the Eastern Kimberley of Western Australia. Samples from Cu–Co–Ni–PGE exploration drilling at Eastman were bulk-assayed and found to contain up to 2.39 ppm PGEs. The rocks have been strongly altered and no longer represent their primary magmatic mineral assemblage and textures. To better understand the Eastman PGE mineralogy, we applied a multi-method approach of quantitative analytical electron microscopy, 3D scanning and in situ mass spectrometry. We find that Pt is primarily hosted in sperrylite, whereas Pd is mainly associated with kotulskite, pseudomertieite, testibiopalladite, sudburyite and michenerite. Additionally, minor Pt and Pd occur in solid solution within cobaltite, as well as Rh-rich cobaltite (hollingworthite). Spatially, PGMs and cobaltite are mostly clustered on a millimetric scale, and BMSs on a micrometric scale.

Mixing behaviour and sources of Ag, Pd, and other trace elements in the Estuary and Gulf of St. Lawrence under winter conditions

The marine chemistry of platinum group elements is poorly documented despite robust evidence of their widespread emissions and deposition around the globe. Here, we report the concentrations and discuss the geochemical behaviours of Ag, Pd and other trace and ultra-trace elements in the Estuary and Gulf of St. Lawrence (EGSL). We highlight the contrasting mixing behaviours of these elements, i.e., conservative (Cd, Re) vs. non-conservative (Ag, Pd), in samples collected during the winter and under ice-covered conditions. We ascribe the contrasting geochemical behaviour of these elements to their differential affinity for reactive surfaces carried into the estuary from the frozen watersheds. We also report an increase of the concentrations of Ag (up to 40 pmol L−1), Pd (up to 10 pmol L−1) and Pt (up to 0.4 pmol L−1) in the bottom and oxygen-depleted waters of the Gulf of St. Lawrence (GSL). A strong correlation between dissolved Pt concentrations and the stable carbon isotopic composition of the dissolved inorganic carbon (δ13C-DIC) suggests that the increased mobility of Pt may result from the aerobic mineralization of organic carbon or the oxidation of Pt-bearing organic complexes. Molar Pt/Pd ratios in the three water masses that compose the water column in the EGSL highlight a potential influence of anthropogenic sources near urban centers. The signature of continental end-members will be required to confirm the impacts of road traffic on the estuarine geochemistry of these elements.

ZIF-8@Pt Nanozyme Used for Scavenging Reactive Oxygen Species in the Treatment of Rheumatoid Arthritis

To formulate a ZIF-8 nano mimetic enzyme conjugated with platinum metal (ZIF-8@Pt) that can scavenge reactive oxygen species (ROS) and to explore its potential applications in the treatment of rheumatoid arthritis (RA). The ZIF-8@Pt nanozyme was created by in situ reduction. Characterization of the nanozyme was then performed and its ability to mimic enzymes was investigated. Cell experiments were conducted using RAW264.7 cells, which were divided into three groups, including the untreated group (UT), the positive control group receiving lipopolysaccharide (LPS), which was designated as the LPS group, and the ZIF-8@Pt group receiving ZIF-8@Pt and LPS treatment. The cell experiments were conducted to evaluate the anti-inflammatory properties of ZIF-8@Pt through scavenging intracellular ROS. On the other hand, a collagen-induced arthritis (CIA) model was induced in rats. Similar to the group designations in the cell experiments, the rats were assigned to three groups, including a healthy control group (the UT group), a positive control group receiving a local injection of PBS solution in the knee joint, which was referred to as the control group, and a treatment group receiving a local injection of ZIF-8@Pt solution in the knee joint, which was referred to as the ZIF-8@Pt group. General evaluation, imaging observation, assessment of inflammatory factors, and pathological evaluation were performed to assess the therapeutic efficacy of ZIF-8@Pt against RA. The in vitro experiment revealed significant difference in the levels of intracellular ROS and LPS-induced M1-type macrophage polarization between the LPS group and the ZIF-8@Pt group (P<0.05). The in vivo experiment showed that significant difference in the levels of inflammatory factors, including interleukin-1β (IL-1β), C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), and arginase-1 (Arg-1) in the knee joints of the CIA rats between the LPS group and the ZIF-8@Pt group (P<0.05). Comparing the findings for the ZIF-8@Pt group and the control group, pathology assessment revealed that ZIF-8@Pt reduced local hypoxia and suppressed osteoclastic activity, neovascularization, and M1-type macrophage polarization (P<0.05). The ZIF-8@Pt enzyme mimetic inhibits macrophage inflammatory polarization by ROS scavenging, thereby improving inflammation in RA. Furthermore, the ZIF-8@Pt nanozyme improves the hypoxic environment and inhibits angiogenesis and bone destruction, demonstrating promising therapeutic efficacy for RA.

Optimizing TCAD Model and Temperature-Dependent Analysis of Pt/AlN Schottky Barrier Diodes for High-Power and High-Temperature Applications

This research presents a comprehensive investigation and optimization of the Pt/AlN Schottky Barrier diode (SBD) using technology computer-aided design (TCAD) modeling. The study explores the electrical characteristics of AlN SBDs with various metal contacts, including Aluminum (Al), Silver (Ag), Tungsten (W), Gold (Au), Nickel (Ni), and Platinum (Pt). Through the comparative analyses of different metal/AlN Schottky contacts, the Pt/AlN structure emerges as the most promising due to its superior barrier height and lower leakage current. At [Formula: see text]K, the diode demonstrates a barrier height of 2.72[Formula: see text]V, a nearly ideal leakage current of 0.046[Formula: see text]pA, and a breakdown voltage of 363[Formula: see text]V. The research extends to examining the temperature-dependent electrical behavior of Pt/AlN Schottky diodes, particularly for high-power and high-temperature applications. Analysis carried out across temperatures ranging from [Formula: see text]K to [Formula: see text]K reveals a trend of increasing ON resistance and consistently lower leakage current with rising temperature. Importantly, the study indicates that the impact of temperature on the barrier height and breakdown voltage of the diode is negligible, thus rendering it suitable for high-temperature operation. Leveraging the unique properties of AlN as an ultra-wide bandgap material within the III-V compound semiconductor family, this research provides valuable insights into the potential applications of Pt/AlN Schottky contact. The study highlights that the Pt/AlN Schottky contact is effective not only for high-power, high-temperature SBDs but also as superior metal/semiconductor gate contacts for field-effect transistors (FETs). Their suitability is attributed to their ability to handle high voltages, minimize reverse leakage current, and demonstrate improved thermal stability.

Ultrahigh Pt-mass-activity catalyst for alkaline hydrogen evolution synthesized by microwave method in air

Platinum (Pt) metal is widely acknowledged as a highly efficient electrocatalyst for hydrogen evolution reaction (HER) in acidic electrolyte. However, its performance in alkaline environments is significantly lower owing to the sluggish water dissociation step. Herein, we synthesized an ultrahigh Pt-mass-activity alkaline HER catalyst using microwave reduction method in air. Our catalyst, PtRu@CNT, comprises PtRu alloy nanoparticles uniformly loaded on carbon nanotubes, with Pt and Ru contents of 12.3 wt% and 4.5 wt%, respectively. The PtRu alloy nanoparticles have an average diameter of about 3 nm and a face-centered cubic structure, and the introduction of Ru has led to a modified electronic structure in Pt. As a result, an impressively low HER overpotential of 13 mV was achieved, significantly lower than commercial 20 wt% Pt/C (61 mV). PtRu@CNT exhibited a high turnover frequency based on metal mass of 3.06 s−1 at 100 mV, about 6 times higher than commercial Pt/C (0.46 s−1 at 100 mV), highlighting its excellent intrinsic activity. The HER mechanism of PtRu@CNT is a Volmer-Tafel mechanism, where the rate-limiting step changed to the recombination of hydrogen atoms from initial water dissociation, attributed to the presence of Ru. The alkaline HER activity of PtRu@CNT ranks among the best of currently reported Pt-based catalysts.

Impactor identification with spallogenic Cr isotopes: The Wabar impact craters (Saudi Arabia)

AbstractPrecise measurements of Cr isotopic composition of terrestrial impactites have successfully provided evidence for the presence of extraterrestrial material and have, in some cases, allowed the identification of the type of impactor responsible for the formation of the impact structure. The high Cr abundance in most meteorite groups aids in detecting extraterrestrial contamination while their distinct isotopic compositions can help with the identification of the nature of the projectile. However, this common approach of detection and identification of extraterrestrial contamination using mass‐independent 53Cr and 54Cr variations fails when the impactor type is an iron meteorite because of their low Cr abundances (which are in a similar range to terrestrial rocks). The present study demonstrates the viability of a spallogenic Cr contribution in iron meteorites (resulting from their long cosmic ray exposure times), which compensates for their low Cr abundances and facilitates the identification of iron‐meteoritic contamination in terrestrial impactites. Thus, it broadens the scope of impactors (and impactites) that can be investigated using mass‐independent Cr isotopes from solely chondrites and primitive achondrites to include iron meteorites. The Wabar impact craters are an optimal candidate for this study, characterized by low weathering, diverse impactites, partial meteorite survival, substantial impactor material contamination, and a felsic target lithology with low background Cr concentration. The Cr isotopic composition of the Wabar background sand, which represents the target lithology, is indistinguishable from the terrestrial Cr isotopic composition range, whereas the Wabar iron meteorites show coupled spallogenic excesses in ε53Cr and ε54Cr. The Cr isotopic compositions of Wabar impactites show resolved deviations from the terrestrial Cr isotopic composition, thereby indicating the presence of Wabar meteoritic contamination. Moreover, the study demonstrates that even an impactor with a non‐carbonaceous chondritic origin, such as a IIIAB iron meteorite, can have a carbonaceous chondrite‐like signature in ε54Cr anomalies due to spallogenic Cr contamination. The study advocates for a comprehensive investigation combining platinum group elements and Cr (and/or Ni, Ru) isotopes to accurately characterize impactor types.

Photophysical properties of benzo[i]dipyrido[3,2-a:2′,3′-c] phenazine (dppn) – A prospective ligand for light-activated anticancer complexes

Benzo[i]dipyrido[3,2-a:2′,3′c]phenazine (dppn) is a prospective ligand for constructing light-activated anticancer complexes of platinum metals. In spite of practical importance, only scarce information on the dppn photophysics and photochemistry was found in the literature. In this work photophysical properties of dppn in acetonitrile solutions were studied by means of stationary and laser flash photolysis, time-resolved luminescence, time-resolved singlet oxygen detection and ultrafast TA spectroscopy. Quantitative characteristics of luminescence (quantum yield 0.26, lifetime 52 ns in deaerated solutions) were measured. Triplet state of the initial compound 3dppn* is formed with the quantum yield estimated as 0.4 from the singlet oxygen production; the main channels of 3dppn* are quenching by dissolved oxygen and self-quenching by the ground state of dppn. Combining the data of ultrafast TA absorption and time-resolved luminescence, we detected the formation of “dark” (not emissive) excited state of dppn with the decay time ca. 150 ps. Two hypotheses on the nature of the dark state were put forward.

Critical and Strategic Metal Resources of Greece

Greece has a large number of critical and strategic metal resources. The proven and indicated reserves of aluminum amount to 2.5 mt and their gross value €5.075 b. Those of chromium amount to 1.2 mt with gross value €4.320 b, while of cobalt are 129 th. t with gross value €3.348 b. The proven and indicated reserves of copper from Chalkidiki and Kilkis areas are approximately 3.04 mt and their gross value €24.776 b, while those of manganese are 2.25 mt with gross value €5.400 b. Molybdenum has been located in Pigi Kilkis with indicated reserves of about 7.7 th. t and gross value €326 m. Under mining are the vein type magnesite deposits of Gerakini Chalkidiki and North Evia. The total reserves (proven + indicated) of magnesite are 280 mt and their gross value €9.800 b. The most important lateritic Fe-Ni-bearing ores are those of Evia Island, Agios Ioannis Viotia, Lokrida Fthiotida, Mesopotamia and Ieropigi Kastoria. The proven and indicated reserves of nickel are 1.39 mt and their gross value €22.240 b. The Rizana/Lachanas porphyry-epithermal antimony deposit is considered the most important stibnite ore. The proven and indicated reserves of stibnite are at least 100 th. t with an average Sb content of 0.3 wt%. Copper, chromium, and cobalt present good prospects for mining. Platinum group metals (PGMs), with economic interest, are contained in the porphyry Cu deposits of Skouries Chalkidiki. Strymonikos Gulf, together with the neighboring coastal and submarine sands, is the most probable area for locating exploitable rare earth metals (REMs). There are excellent investment opportunities in the exploration and mining of Bi, Te, Ga, Ge, and In metals. The deposits of other critical and strategic metals of Greece should be adequately assessed.

A σ-Poor, π-Rich Pyridonate Pincer Ligand Designed To Enhance C–H Oxidative Addition at Platinum Group Metals: Experimental and Computational Studies

A σ-Poor, π-Rich Pyridonate Pincer Ligand Designed To Enhance C–H Oxidative Addition at Platinum Group Metals: Experimental and Computational Studies