Search Results (527)

During the magmatic stage, base and rarer metals segregate from silicate melts to form ore deposits. The usual case is the porphyry (PD) type (Cu, Mo, and W) above subduction zones. The metal grade increases from some ppb or ppm up to percent levels. A new type of trans-porphyry (TPD) deposits (Sn, Ta, Nb, and gems) results from large-scale shear between cratons within continental plates, internal decoupling, and vertical motion. The bulk ore generation process develops along three stages: from magma generation, emplacement, and the formation of an immiscible magmatic phase (MIP), fluids, and melt. However, in TPD, metals segregate from the crust during melting below 800 °C, biotites break down, and the melt remains below the critical point (731 °C). Fluid advection competes with chemical diffusion, yielding the required enrichment. The subcritical MIP splits into a silicate-rich and an aqueous-rich phase, which are both incompatible with each other. Granite, pegmatites, and greisen coexist in the magma chamber. Their respective extraction from a composite mush involves electron exchanges between charges, or orbitals, yielding metal oxides through chemical diffusion. In contrast, in metals (Nb and Ta) observed in pegmatites, and also in gems, electrons rearrange their electronic cloud through their polarizability. Lastly, gems independently grow under the influence of the extremely hard fluids (Li, Be, and B). Magma generation, involving the lower crust (garnet and pyroxene), results in melts that form the two observed pegmatite groups (NYF and LCT), with each being associated with alkaline (A-type) or continental (S-type) granitic melts. Full article

The catalytic hydrogenation of carbon dioxide (CO₂) represents a transformative approach for reducing greenhouse gas emissions while producing sustainable fuels and chemicals, with ethanol being particularly promising due to its compatibility with existing energy infrastructure. Despite significant progress in converting CO₂ to C₁ products (e.g., methane, methanol), selective synthesis of C₂₊ compounds like ethanol remains challenging because of competing reaction pathways and byproduct formation. Recent advances in thermo-catalytic CO₂ hydrogenation have explored diverse catalyst systems including noble metals (Rh, Pd, Au, Ir, Pt) and non-noble metals (Co, Cu, Fe), supported on zeolites, metal oxides, perovskites, silica, metal–organic frameworks, and carbon-based materials. These studies reveal that catalytic performance hinges on the synergistic effects of multimetallic sites, tailored support properties and controlled reaction micro-environments to optimize CO₂ activation, controlled hydrogenation and C−C coupling. Mechanistic insights highlight the critical balance between CO₂ reduction steps and selective C−C bond formation, supported by thermodynamic analysis, advanced characterization techniques and theoretical calculations. However, challenges persist, such as low ethanol yields and undesired byproducts, necessitating innovative catalyst designs and optimized reactor configurations. Future efforts must integrate computational modeling, in situ/operando studies, and renewable hydrogen sources to advance scalable and economically viable processes. This review consolidates key findings, proposes potential reaction mechanisms, and outlines strategies for designing high-efficiency catalysts, ultimately providing reference for industrial application of CO₂-to-ethanol technologies. Full article

The six platinum group elements (PGE) are among the rarest elements in the upper continental crust of the earth. Higher values of PGE have been detected in the upper mantle and in chondrite meteorites. The PGE are siderophile and chalcophile elements and are divided into the following: (1) the Ir subgroup (IPGE) = Os, Ir, and Ru and (2) the Pd subgroup (PPGE) = Rh, Pt, and Pd. The IPGE are more refractory and less chalcophile than the PPGE. High concentrations of PGE led, in rare cases, to the formation of mineral deposits. The PGE are carried in discrete phases, the platinum group minerals (PGM), and are included as trace elements into the structure of base metal sulphides (BM), such as pentlandite, chalcopyrite, pyrite, and pyrrhotite. Similarly to PGE, the PGM are also divided into two main groups, i.e., IPGM composed of Os, Ir, and Ru and PPGM containing Rh, Pt, and Pd. The PGM occur both in mafic and ultramafic rocks and are mainly hosted in stratiform reefs, sulphide-rich lenses, and placer deposits. Presently, there are only 169 valid PGM that represent about 2.7% of all 6176 minerals discovered so far. However, 496 PGM are listed among the valid species that have not yet been officially accepted, while a further 641 are considered as invalid or discredited species. The main reason for the incomplete characterization of PGM resides in their mode of occurrence, i.e., as grains in composite aggregates of a few microns in size, which makes it difficult to determine their crystallography. Among the PGM officially accepted by the IMA, only 13 (8%) were discovered before 1958, the year when the IMA was established. The highest number of PGM was discovered between 1970 and 1979, and 99 PGM have been accepted from 1980 until now. Of the 169 PGM accepted by the IMA, 44% are named in honour of a person, typically a scientist or geologist, and 31% are named after their discovery localities. The nomenclature of 25% of the PGM is based on their chemical composition and/or their physical properties. PGM have been discovered in 25 countries throughout the world, with 64 from Russia, 17 from Canada and South Africa (each), 15 from China, 12 from the USA, 8 from Brazil, 6 from Japan, 5 from Congo, 3 from Finland and Germany (each), 2 from the Dominican Republic, Greenland, Malaysia, and Papua New Guinea each, and only 1 from Argentine, Australia, Bulgaria, Colombia, Czech Republic, England, Ethiopia, Guyana, Mexico, Serbia, and Tanzania each. Most PGM phases contain Pd (82 phases, 48% of all accepted PGM), followed, in decreasing order of abundances, by those of Pt 35 phases (21%), Rh 23 phases (14%), Ir 18 phases (11%), Ru 7 phases (4%), and Os 4 phases (2%). The six PGE forming the PGM are bonded to other elements such as Fe, Ni, Cu, S, As, Te, Bi, Sb, Se, Sn, Hg, Ag, Zn, Si, Pb, Ge, In, Mo, and O. Thirty-two percent of the 169 valid PGM crystallize in the cubic system, 17% are orthorhombic, 16% hexagonal, 14% tetragonal, 11% trigonal, 3% monoclinic, and only 1% triclinic. Some PGM are members of a solid-solution series, which may be complete or contain a miscibility gap, providing information concerning the chemical and physical environment in which the mineral was formed. The refractory IPGM precipitate principally in primitive, high-temperature, mantle-hosted rocks such as podiform and layered chromitites. Being more chalcophile, PPGE are preferentially collected and concentrated in an immiscible sulphide liquid, and, under appropriate conditions, the PPGM can precipitate in a thermal range of about 900–300 °C in the presence of fluids and a progressive increase of oxygen fugacity (fO₂). Thus, a great number of Pt and Pd minerals have been described in Ni-Cu sulphide deposits. Two main genetic models have been proposed for the formation of PGM nuggets: (1) Detrital PGM represent magmatic grains that were mechanically liberated from their primary source by weathering and erosion with or without minor alteration processes, and (2) PGM reprecipitated in the supergene environment through a complex process that comprises solubility, the leaching of PGE from the primary PGM, and variation in Eh-pH and microbial activity. These two models do not exclude each other, and alluvial deposits may contain contributions from both processes. Full article

Post-collisional Cu-Au-Ni-Co-Pt-Pd-Sc porphyry [Duck Creek porphyry system (DCPS)] with overlying Au-Te-Bi-W-HRE epithermal mineralisation [Highway epithermal system (HES)] has been discovered in the core of the Mitakoodi anticline, southwest of Cloncurry. Xenotime and monazite geochronology indicate mineralisation occurred between ~1490 and 1530 Ma. Host rock lithologies show widespread potassic and/or propylitic to phyllic alteration. Paragenesis of porphyry sulphides indicates early crystallisation of pyrite, followed by chalcopyrite, with bornite forming by hydrothermal alteration of chalcopyrite. Cu sulphides also show the effect of supergene oxidation alteration with rims of covellite, digenite and chalcocite. Redox conditions deduced from the V/Sc systematics indicate that the DCPS contains both highly oxidised (typical of porphyries) and reduced lithologies, typical of plume-generated tholeiitic and alkaline suites. Ni/Te and Cu/Te systematics plot within the fields defined by epithermal and porphyry deposits. Duck Creek chalcophile and highly siderophile element (Cu, MgO and Pd) systematics resemble data from porphyry mineral systems, at Cadia, Bingham Canyon, Grasberg, Skouries, Kalmakyr, Elaisite, Assarel and Medet. SAM geophysical inversion models suggest the presence of an extensive porphyry system below the HES. A progressive increase in molar Cu/Au ratios with depth from the HES to the DCPS supports this conclusion. Three metal sources contributed to the linked DCPS-HES viz., tholeiitic ferrogabbro, potassic ultramafic to mafic system and an Fe and Ca-rich alkaline system. The latter two imparted non-crustal superchondritic Nb/Ta ratios that are characteristic of many deposits in the eastern Mount Isa Block. The associated tholeiite and alkaline magmatism reflect mantle plume upwelling through a palaeo-slab window that had accreted below the eastern flank of the North Australian craton following west-verging collision by the Numil Terrane. Discovery of this linked mineral system provides a new paradigm for mineral exploration in the region. Full article

This study investigates 49 gold solidi issued between the 4th and 5th century AD to determine their chemical composition. The coins were first catalogued by recording mass, diameter, and thickness. All specimens underwent non-destructive µ-EDXRF analysis to identify main elements, followed by semi-quantitative fineness evaluation. To validate these results, six coins were randomly micro-sampled: material was dissolved in aqua regia and analysed by ICP-AES for gold quantification and ICP-MS for high precision trace element determination. The non-destructive analyses showed consistently high gold percentages, confirming authenticity and the extensive use of this noble metal during the studied period. Two distinct groups were identified based on the XRF Pt/Pd ratio, suggesting the use of gold from different sources. Comparison of μ-EDXRF and ICP-AES gold contents shows no statistically significant differences; however, this apparent agreement should be interpreted cautiously, as it mainly reflects the limited resolving power of ICP-AES at very high gold concentrations rather than definitive evidence for the absence of surface-related effects. Trace elements analysis detected low concentrations of Cu, Sn, and Pb suggesting the use of alluvial gold for minting. The presence and correlation of terrigenous elements (Al, Ca, Ti, Cr, Mn, Fe, Ni, Zn, Sr) indicate soil as the burial site. Full article

The principal global sources of platinum-group elements (Os, Ir, Ru, Rh, Pt, Pd), collectively referred to as PGEs, are magmatic Ni-Cu sulfide deposits associated with large, layered intrusions, such as the Bushveld Complex. Recent exploration efforts have identified rock types with elevated PGE concentrations, although their potential remains uncertain. This comprehensive review synthesizes the current knowledge regarding potential sources from both natural magmatic and anthropogenic activities, as well as the environmental risks associated with the Pt, Pd, and Rh sub-group, or PPGEs. The order of Pd > Pt > Rh content in emitted particulates has been documented in dust and soil along roadsides, whereas in Fe-Ni laterite, Pt tends to accumulate residually at the top of profiles due to the higher mobility of Pd compared to Pt and Rh. The greater mobility and transfer of Pd are evidenced by higher bioaccumulation factors for Pd in plants and crops, with a higher Pd content observed in roots than in shoots. The effects of chronic occupational exposure to Pt compounds, such as allergic reactions affecting the skin and respiratory system of workers, are well-documented. Although no established permissible limits for Pt, Pd, and Rh in soil, water, or plants exist within major regulatory frameworks, the increasing applications of PPGEs and the use of Pd in catalytic converters (due to its lower cost) underscore the need for further studies on the recycling of spent catalytic converters, health impacts, ecotoxicological assessments, and the application of current technological advances to mitigate exhaust emissions. Full article

Copper (Cu) is an essential element required by all living cells, where it supports critical enzymatic and signaling functions. In cancer, this balance is often disrupted, creating vulnerabilities that can be therapeutically exploited. Changes in Cu availability have been shown to influence key immunoregulatory pathways, including those involved in inflammation, cell death, and immune evasion. Notably, Cu can drive expression of programmed death ligand 1 (PD-L1), contributing to immunosuppression, while also promoting immunogenic cell death, which stimulates adaptive immune responses. These dual effects highlight the complexity and therapeutic potential of Cu-based interventions, particularly in the context of immune modulation and toxicity. This review argues that Cu-based nanomedicines can selectively deliver high concentrations of bioactive Cu to tumor cells, inducing cell death and triggering adaptive immune responses. We summarize current knowledge on Cu’s roles in cancer and immunity, emphasizing recent insights into how these intersect through Cu-mediated modulation of anticancer immune pathways. Finally, we explore the clinical potential of Cu-based nanomedicines to convert immunologically “cold” tumors into “hot” ones, thereby improving responses to immunotherapy. Realizing this potential will depend on the thoughtful integration of Cu delivery approaches with existing immunotherapeutic strategies. Full article

Pt-Fe alloys with abundant inclusions are from the Camumbi River placer deposit, Ecuador. They are derived from unknown Alaskan–Uralian-type intrusion(s) within the Late Cretaceous Naranjal accreted terrane. Compositions of our previously documented chilled silicate glass inclusions are increasingly fractioned from hydrous ferrobasalt to rhyolite in terms of TAS (total alkalis vs. silica). Their liquid lines of descent change from tholeiitic to the calc-alkaline magma series. Here, we document seven rare composite inclusion parageneses of Cu–PGM (platinum-group mineral) sulfides, each coexisting with and exsolved from related fractionated silicate glass (melt). Differentiation is dominated by fractional crystallization in PGM bulk compositions from tholeiitic silicate melts at the highest T (temperature): ~1018 °C. Silicate glass inclusions following the lower T calc-alkaline trend coexist with sulfide PGM parageneses that were likely differentiated, in terms of Pt-Rh-Pd and BMs (base metals), by incongruent melting due to decompression and S-degassing at ~983–830 °C. S-saturated sulfide melts become S-undersaturated below 845 °C. The calculated temperatures are for silicate glass. Pt-rich braggite shows increasing fractionation towards Pd-rich vysotskite within one inclusion paragenesis. A late braggite–vysotskite fractionation trend shows decreasing minor base metals (BMs). Thiospinels are dominated by cuprorhodsite. Minor thiospinels indicate Fe and then strong Ni enrichment at the lowest T. Decompression exsolutions, deflation, and the partial melting of some sulfide inclusion parageneses support rapid ascent to higher crustal levels within a deep-sourced cumulate intrusion. Full article

In this study, CuO nanoparticles were synthesised by chemical precipitation assisted by ultrasonic irradiation (UI), a rapid and environmentally friendly procedure without high temperature that enhances the sustainability of the synthesis process. They were also employed as a catalyst to activate peroxydisulfate (PDS) in the removal of ciprofloxacin (CIP) from a polluted solution. The effects of various factors, such as CIP concentration, catalyst dosage, PDS concentration, and initial pH, on the efficiency of this contaminant treatment were investigated. Under optimal conditions, CIP and TOC removal reached 100% and 49%, respectively, after only 30 min of reaction time and using high initial concentrations of CIP (20 mg/L), PDS (0.5 mM), and CuO (0.5 g/L) in pH (10). For the best set of processing conditions, pseudo-first-order reaction rate kinetics can be assumed and characterised. The possible degradation pathway of CIP is also suggested. Furthermore, by quenching experiment, the presence of O₂⁻*, *OH, and SO₄⁻* were identified, with O₂⁻* being a radical species with great impact on CIP removal. This study demonstrates that, in alkaline environments, ultrasonically synthesised CuO can effectively activate PDS for the degradation of CIP, achieving total removal within 30 min. The results indicate that UI-synthesised CuO is a very promising catalyst for the removal of emerging organic pollutants. Full article

The aim of this work was high-temperature synthesis of PtPdCoNiCu/C nanoparticles with high-entropy alloy (HEA) structure as catalysts for oxygen reduction reaction. The materials were synthesized using a highly dispersed PtPd/C support, which was impregnated with Cu, Ni, and Co precursors followed by their precipitation with an alkali. Subsequently, the material was subjected to thermal treatment in a tube furnace at 600 °C for 1 h in a stream of argon containing 5% hydrogen. In combination with HRTEM, element mapping and line scan, XRD, and XPS data, these results confirm the successful synthesis of five-component PtPdCoNiCu high-entropy alloy nanoparticles on the surface of the carbon support. The obtained materials are characterized by a high electrochemical surface area of up to 63 m²/g(PGM), as determined by hydrogen adsorption/desorption and CO-stripping, and a high specific oxygen reduction reaction (ORR) activity of approximately 269 A/g(PGM) at 0.9 V vs. RHE. The synthesized material demonstrated outstanding stability, as confirmed by an accelerated stress test of 10,000 cycles. After the test, the electrochemical surface area decreased by only 12%, while the catalytic activity for ORR even increased. The proposed synthetic strategy opens a new pathway for obtaining promising highly stable five-component HEA nanoparticles of various compositions for application in catalysts. Full article

Catalytic upgrading of bioethanol via a C–C coupling reaction is a sustainable method of producing 1-butanol, a high-performance biofuel. This reaction was studied using a flow-through microreactor system with Pd/MgO-Al₂O₃ and bimetallic Pd-Cu/MgO-Al₂O₃ mixed oxide-based catalysts in a H₂ carrier gas at a pressure of 21 bar and temperatures ranging from 200 to 350 °C. The effect of the metal promoter(s) on the hydrogen transfer reaction steps in the overall reaction was investigated. The palladium promoter significantly improved the activity and butanol selectivity across the entire temperature range. However, the yield of liquid products decreased significantly at temperatures higher than 250 °C, primarily because the decarbonylation side reaction of the acetaldehyde intermediate accelerated. The promoting effect of Pd was most beneficial below 250 °C because the decarbonylation reaction was inhibited by the reversible poisoning effect of CO on multiple Pd sites responsible for decarbonylation. Diluting the Pd phase with Cu increased liquid yields due to gradually decreasing decarbonylation activity. However, the dehydrogenation–hydrogenation activity decreased as well, as did the promoting effect on the corresponding reaction steps in the coupling reaction. Additionally, the product distribution changed dramatically, decreasing 1-butanol selectivity, because metallic Cu can catalyze the formation of ethyl acetate and ketone products. Full article

The biomarker carcinoembryonic antigen (CEA) plays an important role in the diagnosis and monitoring of cancer, like breast, surveillance, colon, and liver cancer. The highly sensitive surface plasmon resonance (SPR) sensor presented in this work uses two-dimensional (2D) materials: BP/graphene, and the franckeite layer integrated in a Kretschmann configuration. The sensor structure, which includes a copper (Cu) layer and a CaF₂ prism, is intended to detect CEA in aqueous solutions with high accuracy. The proposed sensor’s performance was assessed using the transfer matrix method (TMM), with particular attention paid to important metrics like sensitivity, figure of merit (FoM), detection accuracy (DA), and penetration depth (PD). The proposed sensor achieved a sensitivity of 307.50 deg/RIU and a FoM of 61.62/RIU at a R_min value of 4.20 × 10⁻⁵ a.u. at a 40 nm Cu thickness, operating at a wavelength of 633 nm. The maximum sensitivity of 348.07 deg/RIU was achieved at 47 nm Cu thickness with BP layer, while the graphene layer yielded maximum sensitivity of 314.32 deg/RIU at the same Cu thickness. The results show that adding 2D layered materials to symmetric SPR sensors greatly improves detection performance, providing a promising foundation for the detection of clinical biomarkers in the future. Full article

Atomic effects determining the adsorption of hydrogen and oxygen atoms on (111), (100), (110), and (211) surfaces of Cu and Pd have been studied using quantum chemical simulations. The deformation of the (111) and (100) surfaces during adatom bonding enhances the bond strength at active sites with high coordination numbers. In contrast, the deformation of the (110) and (211) surfaces does not exhibit a strong tendency. The atomic contribution of the nearest-neighbor environment depends on the square magnitude of the interaction matrix element, $V_{ad}^2$. A high $V_{ad}^2$ value increases the proportion of repulsive interactions within the metal adsorption complexes, leading to a decrease in the coordination number of the most stable adsorption site. Full article

A novel metal oxide catalyst, PdO_x/CuO-ST, was prepared by calcining a Pd-embedded CuBTC precursor and compared with a PdO_x/CuO-SG catalyst synthesized via a sol–gel method. Characterization results indicated that in both catalysts, Pd species were incorporated into the CuO lattice, forming synergistic interactions that lowered the reduction temperature of CuO. The PdO_x/CuO-ST catalyst exhibited superior catalytic activity in the oxidative carbonylation of phenol to diphenyl carbonate when calcined at low temperature, which was attributed to well-dispersed Cu atoms and enhanced Pd–Cu integration. However, high-temperature calcination led to catalyst sintering and the formation of surface-adsorbed oxygen species, which reacted with PdO on CuO to generate inactive Pd_xCu_yO phases, thereby reducing the active Pd²⁺ content and degrading catalytic performance. Under optimized reaction conditions (100 °C, 7 h, Pd/phenol molar ratio = 1/425, and 6.6 MPa), the PdO_x/CuO-ST catalyst achieved a maximum phenol conversion of 79.5% and a diphenyl carbonate selectivity of 84.5%. Stability tests revealed that although the catalyst structure remained intact, deactivation occurred due to Pd leaching and the reduction in active PdO to metallic Pd⁰. Full article

Developing highly efficient and stable electrocatalysts from inexpensive and earth-abundant elements represents a significant advancement in overall water splitting (OWS). This study focuses on the synthesis and evaluation of palladium-modified cobalt–phosphorus (PdCoP) and cobalt–iron–phosphorus (PdCoFeP) coatings for use as electrocatalysts in hydrogen evolution (HER), oxygen evolution (OER) and overall water splitting (OWS) in alkaline media. A facile electroless plating method is adopted to deposit the CoP and CoFeP coatings onto a copper surface (Cu sheet), with sodium hypophosphite (NaH₂PO₂) acting as the reducing agent. Pd crystallites were incorporated on CoP and CoFeP coatings using the galvanic displacement method. This study details morphological characterization (using SEM, EDX, and XRD), as well as electrochemical activity testing, for both HER and OER using linear sweep voltammetry (LSV) at different temperatures. The stability of the catalysts for HER was evaluated using chronoamperometry (CA) and chronopotentiometry (CP). The results show that the Pd-modified CoFeP and CoP catalysts exhibited lower overpotentials of 207 and 227 mV, respectively, for HER and 396 mV for OER at a current density of 10 mA cm⁻² compared to the unmodified CoFeP and CoP catalysts. The innovation achieved in this study lies in combining a facile, low-cost deposition method (electroless plating followed by galvanic displacement) with a novel, highly effective ternary composition (PdCoFeP) that exploits synergistic electronic and morphological effects to achieve superior bifunctional performance for alkaline OWS, achieving a low cell voltage of 1.69 V at a current density of 10 mA cm⁻². Overall, this research demonstrates that these synthesized materials are promising candidates for sustainable and economical hydrogen production. Full article