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The recent progress in chemical synthetic methodologies has facilitated the fabrication of discrete plasmonic nanoparticles exhibiting chiral characteristics on their surface. In comparison to conventional gold nanorods (NRs), such structures possess strong plasmonic circular dichroism response, making them highly suitable for various applications involving circularly polarized light. Although the intrinsic and extrinsic chirality of chiral nanostructures produced by the assembly with chiral ligands have been explored both experimentally and theoretically, the investigation into the influencing factors of the intrinsic and extrinsic chirality of discrete chiral Au NRs (dc-Au NRs) has been relatively limited. Herein, we conducted a comprehensive investigation using full-wave electromagnetic simulations to explore the influence of various structural parameters (such as helical depth, width, and numbers of the helical pitches) on the intrinsic and extrinsic chirality of dc-Au NRs. Additionally, we examined the chiral surface plasmon resonance coupling and the corresponding chiral near-field by studying the cross-like assembly of dc-Au NR dimers. These findings serve as valuable guidance for future experimental and theoretical research on chiral plasmonic nanostructures and their applications involving circularly polarized light. [ABSTRACT FROM AUTHOR]

The large Zun-Kholba deposit, relating to a numerous group of orogenic-type gold deposits, is in the Eastern Sayan (Russia)—a segment of the Altai-Sayan fold system of the Central Asian Orogenic Belt. The paper discusses the results of mineralogical, geochemical, geochronological, and Pb-isotopic studies of gold mineralization; the purpose was to verify the genetic model of the deposit. Mineralogical and geochemical data obtained for ore bodies located between hypsometric levels from 1290 to 2090 m indicate a complex distribution of mineral associations at the deposit. There is no vertical and horizontal zonation in the distribution of mineral associations, in the chemical composition of the main ore minerals, as well as in the content of impurity elements in them. In dating ore-forming processes at the Zun-Kholba deposit, a comprehensive approach based on the study of K–Ar and Rb–Sr isotope systems of metasomatites was applied. The combination of Rb–Sr and 40Ar–39Ar methods allowed us to determine that the age of gold mineralization is 411 ± 2 Ma, while the age of the superimposed event, which is associated with redistribution of ore, as well as disturbance of the Rb–Sr and K–Ar isotopic systems of metasomatites, is about 380 Ma. Pb–Pb isotopic study of ore mineralization at the deposit and host Precambrian rocks allowed to prove the leading contribution of the latter in ore lead supply to the mineral-forming system. The model of formation of the Zun-Kholba orogenic gold deposit assumes a genetic relationship between ore-forming processes and intraplate alkaline mafic magmatism due to the impact of the plume in the Early Devonian time on the lithosphere of the Tuva-Mongolian terrane. [ABSTRACT FROM AUTHOR]

The Hongtoushan Cu-Zn volcanogenic massive sulfide (VMS) deposit, located in the Hunbei granite–greenstone terrane of the North China Craton, has undergone a complex, multi-stage metallogenic evolution. The deposit comprises three main types of massive ores: Type-1 ores, characterized by a sulfide matrix enclosing granular quartz and dark mineral aggregates; Type-2 ores, distinguished by large pyrite and pyrrhotite porphyroblasts and a small amount of gangue minerals; and Type-3 ores, mainly distributed in the contact zone between the ore body and gneiss, featuring remobilized chalcopyrite and sphalerite filling the cracks of pyrite. The metallogenic process of the Hongtoushan deposit is divided into three main stages: (1) an early mineralization stage forming Type-1 massive ores; (2) a metamorphic recrystallization stage resulting in Type-2 massive ores with distinct textural features; and (3) a late-stage mineralization event producing Type-3 massive ores enriched in Cu, Zn, and other metals. This study integrates sulfur isotope, trace elements, and fluid inclusion data to constrain the sources of ore-forming materials, fluid evolution and metallogenic processes of the deposit. Sulfur isotope analyses of sulfide samples yield δ 34 S values ranging from −0.7 to 4.2 (mean: 1.8 ± 1.5, 1 σ), suggesting a predominant magmatic sulfur source with possible contributions from Archean seawater. Trace element analyses of pyrite grains from different ore types reveal a depletion of rare earth elements, Cu, and Zn in Type-2 massive ores due to metamorphic recrystallization, and a subsequent re-enrichment of these elements in Type-3 massive ores. Fluid inclusion studies allowed for identifying three types of ore-forming fluids: Type-1 (avg. T h : 222.9; salinity: 6.74 wt.% NaCl eqv.), Type-2 (avg. T h : 185.72; salinity: 16.56 wt.% NaCl eqv.), and Type-3 (avg. T h : 184.81; salinity: 16.22 wt.% NaCl eqv.), representing a complex evolution involving cooling, water–rock interaction and fluid mixing. This multi-disciplinary study reveals the interplay of magmatic, hydrothermal and metamorphic processes in the formation of the Hongtoushan VMS deposit, providing new insights into the fluid evolution and metallogenic mechanisms of similar deposits in ancient granite–greenstone terranes. [ABSTRACT FROM AUTHOR]

Light-matter interactions have garnered considerable interest owing to their burgeoning applications in quantum optics and plasmonics. Utilizing first principles calculations, this work explores the hot carrier (HC) generation and distribution within a composite system made up of a plasmonic nanoparticle dimer and linear polycyclic aromatic hydrocarbon (PAH) molecules. We examine the spatial and energetic distributions of HCs by initiating photoexcitation and allowing localized surface plasmon dephasing. By positioning PAH molecules within the plasmonic nanodimer's gap region, our investigation uncovers HC tuning. Notably, depending on the size of the PAH molecules, there are significant alterations in the HC distribution. Hot electrons (HEs) are distributed across both the nanodimer and the PAH molecule, while hot holes (HHs) become entirely localized on the PAH as the PAH grows larger. These findings improve our understanding of plasmon-molecule coupled states and provide guidance on how to customize HC distributions through the creation of hybrid plasmonic materials. [ABSTRACT FROM AUTHOR]

In this contribution, we present the results of mineralogical investigation of the agates in Paleoproterozoic organic carbon-rich sedimentary rocks within the Onega Basin (Fennoscandian shield, Russia) aimed at reconstructing the agate-forming processes. Optical and scanning electron microscopy, EDS microanalysis, thermal analysis, X-ray powder diffraction, Raman spectroscopy, and carbon isotope analysis were used for the study. Three main varieties of agates differing in morphology and texture were identified, including concentrically zoned nodules, fine-banded, and carbon-rich moss agates. Mineralogical evidence indicates the participation of hydrothermal fluids in agate formation. Concentrically zoned nodules could be formed due to the dissolution of carbonate concretions in the organic carbon-rich siltstones and their silicification as a result of late hydrothermal processes. Fine-banded vein agates occur in stockworks crosscutting organic carbon-rich rocks and are widely accompanied by sulfides, selenides, carbonates, sulfates, and iron oxides. Carbonaceous matter in moss agates is present as poorly ordered carbon and is characterized by a low δ13Corg value (−25.64‰), suggesting a biogenic origin. Raman spectroscopy data showed an elevated amount of moganite besides alpha quartz in the concentrically zoned nodules compared to other agate varieties, indicating different ages of the mineralization processes. We suggest that the revealed varieties of agates were formed at different stages of long-term hydrothermal processes occurring in the Onega Basin. [ABSTRACT FROM AUTHOR]

Biohydrogen (H 2) production by green algae has great biotechnological potential. This study aimed to analyze photosynthetic pigment levels, photosynthetic systems activity, total phenolic/flavonoid content, and H 2 generation in Chlorella vulgaris IBCE C-19 and Parachlorella kessleri MDC6524 in response to sulfur (S) and nitrogen (N) deprivation. The results showed that S and N deficiency caused a growth rate decrease in both cultures that was accompanied by a decrease in the photosynthetic pigments levels, PS II activity, and polyphenols synthesis. In addition, S and N deprivation led to an increase in the H 2 generation. Moreover, the H 2 photoproduction by P. kessleri was higher compared to that of C. vulgaris under N- and S-deprived anaerobic conditions. DCMU inhibited the H 2 production by both algae showing the involvement of PS II in this process. The findings contribute to the ongoing research on the development of strategies to optimize algae cultivation for enhanced H 2 yield. • N and S deprivation leads to a decrease in pigments content and PS II activity. • N and S starvation increases H 2 generation in Parachlorella and Chlorella cultures. • P. kessleri produce more H 2 than C. vulgaris under N- and S-deprived conditions. • DCMU inhibited H 2 production by green algae under N- and S-deprived conditions. [ABSTRACT FROM AUTHOR]

Big Syncline is one of the few unexploited deposits of the Aggeneys-Gamsberg Ore District of the Northern Cape Province of South Africa and comprises Zn > Pb > Cu mineralisation. Future exploitation of this deposit requires a good understanding of the mineralisation textures and mineralogy for beneficiation purposes. Two of the most commonly occurring mineralisation types at Big Syncline, the mineralised pelitic schist (PEL) and garnet-magnetiteassociated mineralisation (GM), are investigated with regards to sphalerite petrography and mineralogy and their potential impact on Zn flotation recovery and grade. Detailed optical petrographic analyses revealed three colour variations in the sphalerite: the opaque (i.e., black) and ruby-red varieties prevalent in the PEL; and the honey-yellow variety more common in the GM. Scanning electron microscopy with energy dispersive X-ray spectroscopy (EDS) analyses indicated increasing Fe content from the honeyyellow to ruby-red to opaque sphalerite varieties. The latter two varieties were also observed to have elevated Mn contents. Laboratory-scale differential flotation tests were applied on the two mineralisation types to determine their processing behaviour. Despite poor selectivity, the GM produced a bulk Zn concentrate of superior quality to the PEL. However, the latter showed better selectivity with the bulk of the Zn reporting to the Zn concentrate. The reduced overall quality of the PEL concentrate is attributed to the increased dilution. This is due to the high abundance of gangue sulphides in the flotation feeds as well as higher Fe and Mn contents in sphalerite. The higher Mn content in the PEL sphalerites also leads to higher Mn recovery and grade in the Zn concentrates. Although the GM overall has higher Mn contents, it is hosted in silicates leading to substantial Mn rejection to the tailings. [ABSTRACT FROM AUTHOR]

Early clinical diagnosis, effective intraoperative guidance, and an accurate prognosis can lead to timely and effective medical treatment. The current conventional clinical methods have several limitations. Therefore, there is a need to develop faster and more reliable clinical detection, treatment, and monitoring methods to enhance their clinical applications. Raman spectroscopy is noninvasive and provides highly specific information about the molecular structure and biochemical composition of analytes in a rapid and accurate manner. It has a wide range of applications in biomedicine, materials, and clinical settings. This review primarily focuses on the application of Raman spectroscopy in clinical medicine. The advantages and limitations of Raman spectroscopy over traditional clinical methods are discussed. In addition, the advantages of combining Raman spectroscopy with machine learning, nanoparticles, and probes are demonstrated, thereby extending its applicability to different clinical phases. Examples of the clinical applications of Raman spectroscopy over the last 3 years are also integrated. Finally, various prospective approaches based on Raman spectroscopy in clinical studies are surveyed, and current challenges are discussed. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are semi-conducting nanoparticles that have been developed for a range of biological and non-biological functions. They can be tuned to multiple different emission wavelengths and can have significant benefits over other fluorescent systems. Many studies have utilised QDs with a cadmium-based core; however, these QDs have since been shown to have poor biological compatibility. Therefore, other QDs, such as indium phosphide QDs, have been developed. These QDs retain excellent fluorescent intensity and tunability but are thought to have elevated biological compatibility. Herein we discuss the applicability of a range of QDs to the cardiovascular system. Key disease states such as myocardial infarction and stroke are associated with cardiovascular disease (CVD), and there is an opportunity to improve clinical imaging to aide clinical outcomes for these disease states. QDs offer potential clinical benefits given their ability to perform multiple functions, such as carry an imaging agent, a therapy, and a targeting motif. Two key cell types associated with CVD are platelets and immune cells. Both cell types play key roles in establishing an inflammatory environment within CVD, and as such aid the formation of pathological thrombi. However, it is unclear at present how and with which cell types QDs interact, and if they potentially drive unwanted changes or activation of these cell types. Therefore, although QDs show great promise for boosting imaging capability, further work needs to be completed to fully understand their biological compatibility. [ABSTRACT FROM AUTHOR]

Chiral artificial nanosystems constructed from inorganic nanoparticles brought about a paradigm shift in chiral sensing, enantioselective catalysis, chiral polarization engineering, and chiral emission due to their strong light–matter interaction and their precisely engineered properties. Especially bottom‐up approaches hold great potential for the inexpensive, scalable production of plasmonic, excitonic, and upconversion chiral materials. This perspective first reviews the state‐of‐the‐art fabrication schemes: chiral molecule‐induced chirality, chiral nanoparticle growth, and assembly of chiral superstructures from achiral building blocks. Next, the emerging field of dynamically tunable chiroptical materials, promising for adaptive thin‐film optics, display technologies, and information encoding, is explored. Here, the strength of chiral assemblies based on their rich tuning mechanisms and their ability for geometrical reconfiguration is highlighted. Finally, promising future directions and opportunities in the field of active chiroptical materials are discussed. [ABSTRACT FROM AUTHOR]

There is a wide variety of ore deposits in Albania, where 20% of the Cu resources belong to a deposit type of unknown genesis (sulphide-bearing quartz veins in gabbroic rocks). The focus of this paper is on two mineralisations of this type (Kçira and Thirra) in the Mirdita Zone, an ophiolite zone representing the Mesozoic Neotethys Ocean in the Dinarides. Our aim is to understand the ore-forming processes and the genesis of these deposits, which can be used in future exploration projects. According to the petrographical analysis, the host rock suffered propylitic alteration or subgreenschist facies metamorphism. Mineral chemistry of pyrite and epidote suggests a VMS related origin, more precisely, the deeper part of its stockwork feeder zone. The bulk rock geochemical analyses confirms that the mineralisations are classified as mafic-, Cyprus-type VMS deposits. Differences in the geochemical compositions and the corresponding mineralogical observations are attributed to the distinct original geotectonic positions: higher amount of compatible elements (Cr, Ni, V and Cu) occur in Kçira, which formed in a mid-oceanic ridge environment, while incompatible elements (Ag, As, Co and Zn) are more abundant in the Thirra deposit, which formed in a supra-subduction zone setting. [ABSTRACT FROM AUTHOR]

The results of investigations into enrichment of precious metals in sphalerite and pyrite from the Maluntou epithermal gold deposit, China, are reported. The obtained data suggest intimate associations of Au- and Ag-bearing nanoparticles with chalcopyrite inclusions in sphalerite and pyrite. The origins of chalcopyrite inclusions involved different hydrothermal processes, including recrystallization-driven phase separation from parent chalcopyrite-sphalerite solid solutions and replacement of pre-existing pyrite in the presence of Cu-bearing fluids. The chalcopyrite blebs/lamellae follow sphalerite {111} planes, which define a shared sulfur layer for both chalcopyrite and sphalerite. This study indicates that mixing and boiling during the evolution of ore-forming fluids for the Maluntou deposit are key processes for the abnormal enrichment of precious metals in sphalerite and pyrite. The chalcopyrite micro/nano inclusions enhanced enrichment of precious metals in sphalerite provides new insights into the controls on the enrichment of precious metals in sulfides. [ABSTRACT FROM AUTHOR]

Anisotropic plasmonic metasurfaces have attracted broad research interest since they possess novel optical properties superior to natural materials and their tremendous design flexibility. However, the realization of multi-wavelength selective plasmonic metasurfaces that have emerged as promising candidates to uncover multichannel optical devices remains a challenge associated with weak modulation depths and narrow operation bandwidth. Herein, we propose and numerically demonstrate near-infrared multi-wavelength selective passive plasmonic switching (PPS) that encompasses high ON/OFF ratios and strong modulation depths via multiple Fano resonances (FRs) in anisotropic plasmonic metasurfaces. Specifically, the double FRs can be fulfilled and dedicated to establishing tailorable near-infrared dual-wavelength PPS. The multiple FRs mediated by in-plane mirror asymmetries cause the emergence of triple-wavelength PPS, whereas the multiple FRs governed by in-plane rotational asymmetries avail the implementation of the quasi-bound states in the continuum-endowed multi-wavelength PPS with the ability to unfold a tunable broad bandwidth. In addition, the strong polarization effects with in-plane anisotropic properties further validate the existence of the polarization-resolved multi-wavelength PPS. Our results provide an alternative approach to foster the achievement of multifunctional meta-devices in optical communication and information processing. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPS) are known for their ruby-red colour related to their localized plasmon resonance and could be used for creating a new type of colour pigment. Moreover, the colour varies if the nanoparticle suspension is observed in transmission or diffuse reflectance spectra. We have systematically studied this two-colour effect, called the bichromatic effect, for twelve samples of nanoparticles in water with increasing diameters from 16 to 108 nm. The transmission and diffuse reflectance spectra were recorded and compared to an analytical model based on the scattering cross sections calculated using the Mie theory. We have also calculated and represented the colours within the CIE colour diagram. This approach provides a very efficient way for predicting the colouring power of plasmonic pigments when AuNPs are embedded in a material. It stresses that spherical gold nanoparticles may exhibit a good bichromatic effect when their diameter is between 70 and 90 nm. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) of CaGa2S4:Pr3+ chalcogenide semiconductor compound is studied. The PL spectrum consists of a set of intense sharp lines at 494, 631, 654, and 741 nm, formed by intra-4f transitions of Pr3+ ions. The energy level diagram of CaGa2S4:Pr3+ is proposed. A broad structural band in the PL excitation spectra in the range of 270–360 nm is assumed with superposition of host related and 4f2 → 4f15d1 direct excitation transition bands whereas a sharp line at 456 nm—with 3H4 → 3P2 direct excitation. The PL decays at intensive emission lines at room temperature were found to obey nonexponential law with time constant in the range of 1.1–2.1 μs for fast decay component and of 4.5–6.3 ms for slow one. Thermal quenching by only 50% and 75% of the PL intensity of CaGa2S4:Pr3+ with 7 and 3 at. % Pr3+ ions concentration, respectively, was obtained in the range of 10–300 K. Extreme stability of PL spectra and efficiency of CaGa2S4:Pr3+ compound up to 105 W/cm2 of excitation power density was achieved. [ABSTRACT FROM AUTHOR]

We demonstrate the possibility of using a two-dimensional array of spheroidal metallic nanoparticles embedded in a one-dimensional photonic crystal to obtain a narrow-bandpass, polarization-sensitive dichroic filter operating in the near-UV and visible domains. The optical anisotropy of the array of identically oriented nanoparticles results in two spectrally distinct plasmon resonances independently excited for two mutually orthogonal linear polarization states of light, which ensures polarization and spectral selectivity of the composite structure. The narrow transmission bands of the filter are defect modes due to a layer located at the center of the structure and hosting the nanoparticle array. In order to suppress these transmission windows, it is essential that the defect modes closely coincide with the plasmon resonances excited in the array. We show that the use of deterministic aperiodic distributed reflectors surrounding the defect layer makes it possible to adjust the spectral positions of two defect modes in two separate bandgaps in order to achieve such a coincidence. Among the various parameters governing the precise position of transmittivity windows of the filter, we establish the strong influence of the thickness of the defect layer. We also show that a strong localization of the optical field in the plane of the nanoparticle array is essential to enhance the efficiency of plasmonic excitation and obtain the desired control of the defect modes. Our study opens up possibilities for the further development of polarization-controlled nanophotonic devices. [ABSTRACT FROM AUTHOR]

This study reported the first-time preparation of reduced graphene oxide (rGO) and zinc oxide (ZnO) composite (rGO-ZnO) thin films through successive ionic layer adsorption and reaction (SILAR) method. The effects of rGO and heat treatment on the structural, morphological, chemical, optical, vibrational and photocatalytic properties of composite films were investigated. The structural results showed that ZnO and rGO-ZnO thin films could be obtained without heat treatment. The rGO-ZnO composite showed improved crystallinity and homogeneity compared to ZnO, with formation of flower-like structures. The presence of graphene derivatives in the composite films was validated using Raman spectroscopy. Chemical composition analysis showed an increase in the carbon content in rGO-ZnO composite. Optical transmittance in the visible range was reduced from 90% for ZnO to 51% for rGO-ZnO. Moreover, the bandgap energy of ZnO decreased from 3.33 to 3.04 eV with the presence of rGO and heat treatment. The rGO-ZnO composite thin films exhibit enhanced visible-light photocatalytic discoloration of Orange G dye, which is attributed to bandgap narrowing with improved visible light response and charge separation. The approach described here provides a simple and efficient way to synthesise rGO-ZnO composite thin films with potential applications for a wide range of environmental issues. [ABSTRACT FROM AUTHOR]

Chirality, either of light or matter, has proved to be very practical in biosensing and nanophotonics. However, the fundamental understanding of its temporal dynamics still needs to be discovered. A realistic setup for this are the so-called metastructures, since they are optically active and are built massively, hence rendering an immediate potential candidate. Here, we propose and study the electromagnetic-optical mechanism leading to chiral optical imprinting on metastructures. Induced photothermal responses create anisotropic permittivity modulations, different for left or right circularly polarized light, leading to temporal-dependent chiral imprinting of hot-spots, namely, "imprinting of chirality." The above effect has not been observed yet, but it is within reach of modern experimental approaches. The proposed nonlinear chiroptical effect is general and should appear in any anisotropic material; however, we need to design a particular geometry for this effect to be strong. These new chiral time-dependent metastructures may lead to a plethora of applications. [ABSTRACT FROM AUTHOR]

Random lasing was achieved in CdS and Zn0.65Cd0.35Se micropowders at optical pump levels of 0.1–2 MW/cm2 with N2-laser radiation at wavelength 337 nm. The random generation thresholds were 820 kW/cm2 for CdS and 740 kW/cm2 for Zn0.65Cd0.35Se micropowders. Introduction of Ca(Al0.1Ga0.9)2S4:Eu2+ and Ca4Ga2S7:Eu2+ chalcogenides into the mixture of micropowders of CdS and Zn0.65Cd0.35Se solid solutions led in both cases to a drop in the random generation threshold to 520 and 550 kW/cm2, respectively, and to the appearance of laser-radiation line structures and their increased intensities. This may have been caused by an increase in the number of feedback loops because of the introduction of additional scatterers. [ABSTRACT FROM AUTHOR]

In metal–dielectric nanostructures with metal inhomogeneities of about 10–100 nm in size strong local concentration of electromagnetic radiation at the frequencies of the incident (primary) and emitted (secondary) radiation occurs simultaneously with a considerable increase of the rate of nonradiative transitions (fluorescence quenching). The general principles of the use of metal–dielectric nanostructures to enhance the fluorescence and the experimental use of these principles for organic molecules, including biomolecules with fluorescent labels, are examined. [ABSTRACT FROM AUTHOR]

This study investigates innovation as a cause of highly skilled migration. Drawing on a totally new database that includes all the Greek PhD holders, combined with panel data from the Global Innovation Index covering 57 countries over the 2009–2020 period, we find that innovation constitutes a strong determinant for highly skilled migration. That is, a rise in innovative performance is positively associated with an increase in the number of highly skilled Greek migrants. We further find a two‐way causality between innovation and highly skilled migration. Namely an increase in the number of highly skilled Greek migrants positively affects innovative performance. While most of the recent studies have comprehensively addressed the positive effects of skilled migration on innovation, they have not looked at innovation as a determinant of highly skilled migration. We further discuss the potential implications of our findings on countries displaying low innovative performance coupled with brain drain. [ABSTRACT FROM AUTHOR]

Plasma-enhanced atomic layer deposition was employed to grow aluminum nitride (AlN) thin films on Si (100), Si (111), and c-plane sapphire substrates at 250 °C. Trimethylaluminum and Ar/N2/H2 plasma were utilized as Al and N precursors, respectively. The properties of AlN thin films grown on various substrates were comparatively analyzed. The investigation revealed that the as-grown AlN thin films exhibit a hexagonal wurtzite structure with preferred c-axis orientation and were polycrystalline, regardless of the substrates. The sharp AlN/substrate interfaces of the as-grown AlN are indicated by the clearly resolved Kiessig fringes measured through X-ray reflectivity. The surface morphology analysis indicated that the AlN grown on sapphire displays the largest crystal grain size and surface roughness value. Additionally, AlN/Si (100) shows the highest refractive index at a wavelength of 532 nm. Compared to AlN/sapphire, AlN/Si has a lower wavelength with an extinction coefficient of zero, indicating that AlN/Si has higher transmittance in the visible range. Overall, the study offers valuable insights into the properties of AlN thin films and their potential applications in optoelectronic devices, and provides a new technical idea for realizing high-quality AlN thin films with sharp AlN/substrate interfaces and smooth surfaces. [ABSTRACT FROM AUTHOR]

At the Trans‐Atlantic Geotraverse hydrothermal field, metalliferous sediments cover extinct hydrothermal mounds and the surrounding seafloor. Here, we report the morphological, mineralogical and geochemical processes that deposit these sediments, remobilize their metals, and affect their preservation. We found that the initial sediment metal tenor is controlled by physical transport of hydrothermal material from its source, followed by diagenetic redistribution and potentially diffuse fluid flow after high‐temperature hydrothermal activity has ceased. We distinguished three different environments: (a) proximal metalliferous sediments on top of extinct mounds are mainly derived from oxidative weathering of primary sulfide structures and are predominantly composed of Fe oxyhydroxides with low contents of Cu, Co, and Zn; metal enrichments in specific layers are likely related to upward flow of low‐temperature hydrothermal fluids; (b) medial distant metalliferous sediments found at the base of the mounds, deposited by mass transport, contain cm‐thick layers of unsorted sulfide sands with high base metal contents (e.g., up to 28% Cu); these buried sulfides continue to undergo dissolution, resulting in metal release into porewaters; (c) distal metalliferous sediments, found in depositional basins a few hundreds of meters from the extinct mounds, include fining‐upwards sequences of thin sulfide sand layers with Fe oxyhydroxides and were deposited by recurrent turbiditic flows. Dissolved metals (e.g., Cu2+ and Mn2+) diffuse upwards under reducing conditions and precipitate within the sediment. Hence, when using hydrothermal sediments to construct reliable geochronological records of hydrothermal activity, distance from source, local seafloor morphology, mass‐transport and depositional, and diagenetic modification should all be considered. Plain Language Summary: The seafloor massive sulfide mounds at the TAG hydrothermal field (Mid‐Atlantic Ridge) are surrounded by metalliferous sediments. These sediments can be used to understand the history of the hydrothermal activity; however, the evolution of these sediments can be complex. The aim of this study is to understand the processes that lead to the accumulation and alteration of these sediments. For this, we identified the mineralogical, geochemical and physical processes that affect the sediments. Our results show that sediments found on mound tops are mainly composed of iron and manganese oxides and hydroxides, and are low in other metal contents compared to other environments. Medial distant sediments at the base of the mounds have thick beds of sulfide‐rich sediments that contain the highest concentrations of metals and are currently undergoing dissolution. In depositional channels, several hundreds of meters distal from the mounds, metalliferous sediment have accumulated in several meters thick layers that contain high concentrations of dissolved metals. This study reveals that the metal content of hydrothermal sediments is strongly controlled by their physicochemical environment and processes after deposition, and we suggest these processes should be considered when using metalliferous sediments as records of the evolution and activity of hydrothermal systems. Key Points: TAG hydrothermal field sediments have high metal contents that vary distinctly between different seafloor depositional environmentsLowest metal contents are found in sediments on top and highest in those at the base of extinct hydrothermal moundsDeposition, remobilization, and preservation of metals in hydrothermal sediments lead to distinctively different sediment characteristics [ABSTRACT FROM AUTHOR]

In dictating the optical processes in metal nanoparticles, for instance, quantum nature of free electrons is significantly dominant and plays very crucial roles at the level of nanoscale dimensions of materials. As consequences of the quantum-confinement effects on the conduction electrons, surface-plasmon resonance induced optical absorption and light emission properties of metal nanoparticles are found to be strongly dependent on physical dimensions of the nanomaterials. In addition, surface-confined acoustic vibration (phonon) modes have been experimentally observed to depend on the sizes of the metal nanoparticles. Also, interestingly, tuning of the surface-plasmon resonance condition is found to enhance the intensity of the acoustic Raman modes in metal nanoparticles. The study highlights the role of plasmon-phonon coupling in Co metal nanoparticles embedded in a silica-glass. In the research field of nanosciences and nanotechnologies, extraordinary behaviour and properties of nanoscale matters are investigated. In this context, interesting studies have been discussed in this review article to elaborate optical, chemical and photoluminescence properties of nanoscale Ag metal particles. Subtle detection of optical phenomena associated with the excited many-body electronic processes in the metal nanoparticles, for example, are very interesting but definitely challenging. Here we make an attempt to find out how the thermal growth of Ag metal nanoparticles in a glass matrix snuffs out the light emission from the samples? Quantum mechanical interpretations of the underlying processes about the quenching of photoluminescence phenomena with the growth of the metal nanoparticles will help to fine tune the optical properties of plasmonic systems as well as to harness potential applications of the nanomaterials., (© 2024 Wiley-VCH GmbH.)

Large-scale layered intrusions of a peridotite–pyroxenite–gabbronorite complex, to which Cr, Ni, Cu, and PGE deposits and ore occurrences are confined, were emplaced into the Baltic paleocontinent 2.50–2.45 Ga. Layered intrusions in the Monchegorsk Ore District, including the Monchepluton and Imandra–Umbarechka Complex, as well as the gabbro-anorthosite complex of the Main Ridge, were analyzed earlier geochemically and isotopically. In the present paper, the authors analyze layered intrusions in the Kola region (Mount Generalskaya) and Karelia (Kivakka, Kovdozero, and the Burakovsky Pluton). The primary composition of mantle magmas for the layered intrusions is assumed to be identical to that of the komatiitic basalts making up the volcanogenic units of the Vetreny Belt and the Imandra–Varzuga zone. A general model for the formation of layered intrusions includes superplume uplift in the early Paleoproterozoic, the generation of mantle magmas and their injection into the lower portion of the earth crust, the formation of deep-seated and intermediate magma chambers, and the intense contamination of the granulite–metamorphic complex followed by the generation of magma chambers provoked by single or multiple injections. [ABSTRACT FROM AUTHOR]

A brief review of surface enhanced Raman scattering (SERS) with metal–dielectric nanostructures and results of its application for cultural heritage studies with paintings as the representative example are presented. Twenty microcrystalline inorganic pigments were successfully detected with 10–100-fold sensitivity enhancement using 1-μg samples. [ABSTRACT FROM AUTHOR]

This article discusses the impacts of overprinting of tectonic and plutonic events on the mineralization of the Duna Pb-Ba ore deposit, according to geologic settings and fluid inclusion studies. The Duna carbonate-hosted deposit contains a significant amount of Ag (18.9-264.3 ppm), Cu (77-41600 ppm), Sb (32.7-11000 ppm), Sr (63.5-15100 ppm), and Fluid inclusions with 7.34-23.65 wt.% NaCl equivalent. The homogenization temperature of about 110-285°C, as well as the paragenesis of the minerals shows a difference compared with other Pb-Zn deposits such as the Irish-type and MVT. The ore mineralization in the Duna mine occurred as stratabound, open space-filling, and along the brecciated fault zones. The concordant (stratabound) type of mineralization, with salinity and homogenization temperature of 18.54 to 23.65 wt.% NaCl equivalent, and 113°C to 165°C respectively, is usually typical of MVT-ore deposits, which in this area evolved during the Early Cimmerian orogeny and was later interrupted by mineralization along younger brecciated fault zones with salinity and homogenization temperature of 7.34 to 23.65 wt.% NaCl equivalent, and 113°C to 285°C respectively. This discordant mineralization, which occurred along the faults, formed by the end of the Late Cretaceous and during the Cenozoic as a result of the intrusion of a plutonic mass, and is comparable to the Irish-type ore deposits. [ABSTRACT FROM AUTHOR]

This work reports on the plasmonic properties of a symmetry-breaking system consisting of rhodium dual broken nanorings, in the ultraviolet–visible regime. In the structure, two rhodium broken rings are located with a separation on the scale of nanometers. As the separation, the light polarization, and the relative orientation of the broken angles are, respectively, varied, the plasmonic scattering efficiency of the system is investigated, using the finite difference time domain method. Multiple plasmonic resonances are revealed, and the associated asymmetry-induced Fano-like lineshapes are fitted to a model that employs multiple Fano lineshape functions. The resonance wavelengths, the spectral widths, and the characteristic q values are determined from the best fit parameters, and the plasmonic characteristics of the system are quantitatively probed. The results in this work may be beneficial in designs of plasmonic devices that operate at ultraviolet–visible wavelengths. [ABSTRACT FROM AUTHOR]

Fluorescence can be enhanced or quenched depending on the distance between the surface of a metal nanoparticle and the fluorophore molecule. Fluorescence enhancement by nearby metal particles is called metal-enhanced fluorescence (MEF). MEF shows promising potential in the field of fluorescence-based biological sensing. MEF-based biosensor systems generally fall into two platform categories: (1) a two/three-dimensional scaffold, or (2) a colloidal suspension. This review briefly summarizes the application studies using wavelength-dependent carbon dots (UV-VIS), noble metals (VIS), and upconversion nanoparticles (NIR to VIS), representative nanomaterials that contribute to the enhancement of fluorescence through the resonance energy transfer modulation and then presents a perspective on this topic. [ABSTRACT FROM AUTHOR]

Plasmonic metal nanoparticles and semiconductor quantum dots (QDs) are two of the most widely applied nanomaterials for optical biosensing and bioimaging. While their combination for fluorescence quenching via nanosurface energy transfer (NSET) or Förster resonance energy transfer (FRET) offers powerful ways of tuning and amplifying optical signals and is relatively common, metal–QD nanohybrids for plasmon-enhanced fluorescence (PEF) have been much less prevalent. A major reason is the competition between fluorescence quenching and enhancement, which poses important challenges for optimizing distances, orientations, and spectral overlap toward maximum PEF. In this feature article, we discuss the interplay of the different quenching and enhancement mechanisms (a mixed distance dependence of quenching and enhancement – "quenchancement") to better understand the obstacles that must be overcome for the development of metal–QD nanohybrid-based PEF biosensors. The different nanomaterials, their combination within various surface and solution based design concepts, and their structural and photophysical characterization are reviewed and applications toward advanced optical biosensing and bioimaging are presented along with guidelines and future perspectives for sensitive, selective, and versatile bioanalytical research and biomolecular diagnostics with metal–QD nanohybrids. [ABSTRACT FROM AUTHOR]

Single photon sources based on semiconductor quantum dots are one of the most prospective elements for optical quantum computing and cryptography. Such systems are often based on Bragg resonators, which provide several ways to control the emission of quantum dots. However, the fabrication of periodic structures with many thin layers is difficult. On the other hand, the coupling of single-photon sources with resonant nanoclusters made of high-index dielectric materials is known as a promising way for emission control. Our experiments and calculations show that the excitation of magnetic Mie-type resonance by linearly polarized light in a GaAs nanopillar oligomer with embedded InAs quantum dots leads to quantum emitters absorption efficiency enhancement. Moreover, the nanoresonator at the wavelength of magnetic dipole resonance also acts as a nanoantenna for a generated signal, allowing control over its radiation spatial profile. We experimentally demonstrated an order of magnitude emission enhancement and numerically reached forty times gain in comparison with unstructured film. These findings highlight the potential of quantum dots coupling with Mie-resonant oligomers collective modes for nanoscale single-photon sources development. [ABSTRACT FROM AUTHOR]

The effect of plasmonic nanostructures (NSs) on the Raman spectra and underlying structural changes in thin chalcogenide films is investigated. Several tens of nanometers thick As2S3 and Se films were deposited by thermal sputtering on glass and surface-enhanced Raman spectroscopy (SERS) substrates based on gold nanostructures for comparison. The films on glass were practically not detectable by the Raman spectroscopy. Using gold NSs as the substrates enabled reliable registration of the Raman spectra of both the As2S3 and Se films. The registered Raman spectra contained all the features usually present in the films with the thicknesses ~1 μm or more. Based on our analysis of the spectra obtained at different excitation wavelengths, we may conclude that the SERS chemical mechanism makes the main contribution to the enhancement of the Raman signal from chalcogenide films. Adjustment of the parameters of SERS substrates to tune their plasmon band position in resonance with the excitation laser radiation enables increasing the plasmonic enhancement contribution. Besides the effect of enhancement, localized plasmon resonance in the gold NSs causes local heating of the chalcogenide film around them leading to local structural transformations, which can be controlled using the Raman spectra. [ABSTRACT FROM AUTHOR]

Solar‐driven water splitting to produce clean and renewable hydrogen offers a green strategy to address the energy crisis and environmental pollution. Heterostructure catalysts are receiving increasing attention for photocatalytic hydrogen generation. ZnO/ZnS/CdS and ZnO/CdS heterostructures have been successfully designed and prepared according to two different strategies. By introducing a heterointerface layer of ZnS between ZnO and CdS, a Z scheme charge‐transfer channel was promoted and achieved superior photocatalytic performance. A highest hydrogen generation rate of 156.7 μmol g−1 h−1 was achieved by precise control of the thickness of the heterointerface layer and of the CdS shell. These findings demonstrated that heterostructures are promising catalysts for solar‐driven water splitting, and that heterointerface engineering is an effective way to improve the photocatalytic properties of heterostructures. [ABSTRACT FROM AUTHOR]

The optimization of the fluorescence enhancement factor of the IgG-FITC conjugate as an immunofluorescent marker, depending on the optical and topographic parameters of the colloidal silver film on the surface of a polystyrene plate for immunoassay, was carried out for the first time, and the factors effecting the enhancement were identified. By means of time-resolved spectroscopy as well as by detection the relative concentrations of IgG-FITC adsorbed on the solid phase with enzyme-linked immunoassay, it was shown that fluorescence enhancement in the presence of silver nanoparticles is a resonance process associated with plasmon effects. The most important parameters correlating with the fluorescence enhancement factor are the optical density value at the wavelength of excitation and emission of the fluorophore. The maximum enhancement factor of 10.2 times was obtained for Ag films with the highest optical density. [ABSTRACT FROM AUTHOR]

Fano resonances that feature strong field enhancement in the narrowband range have motivated extensive studies of light–matter interactions in plasmonic nanomaterials. Optical metasurfaces that are subject to different mirror symmetries have been dedicated to achieving nanoscale light manipulation via plasmonic Fano resonances, thus enabling advantages for high-sensitivity optical sensing and optical switches. Here, we investigate the plasmonic sensing and switches enriched by tailorable multiple Fano resonances that undergo in-plane mirror symmetry or asymmetry in a hybrid rotational misalignment metasurface, which consists of periodic metallic arrays with concentric C-shaped- and circular-ring-aperture unit cells. We found that the plasmonic double Fano resonances can be realized by undergoing mirror symmetry along the X-axis. The plasmonic multiple Fano resonances can be tailored by adjusting the level of the mirror asymmetry along the Z-axis. Moreover, the Fano-resonance-based plasmonic sensing that suffer from mirror symmetry or asymmetry can be implemented by changing the related structural parameters of the unit cells. The passive dual-wavelength plasmonic switches of specific polarization can be achieved within mirror symmetry and asymmetry. These results could entail benefits for metasurface-based devices, which are also used in sensing, beam-splitter, and optical communication systems. [ABSTRACT FROM AUTHOR]

In this study we synthesize organic–inorganic hybrid perovskite quantum dots (PeQDs) having a high photoluminescence quantum yield (PLQY = 98%) for light-emitting applications. The luminescence peak of the FAPbBr3 (FA+: formamidinium) PeQDs in solution is located at 527 nm; its CIE 1931 color coordinates are (0.169, 0.760), very close to the BT.2020 standard (0.170, 0.797). After mixing the PeQDs with polydimethylsiloxane, the mixture behaves as a color-conversion layer (CCL) for quantum-dot light emitting diodes (LEDs), achieving a high power efficiency (129.4 lm W−1). Because PeQDs readily decompose in most polar solvents, we blend ours with polyvinylcinnamate (PVCN), which is readily soluble in toluene, to formulate photopatternable thin films. The resulting photopatternable perovskite quantum dot–polymer nanocomposites (PQD–PNCs) can be patterned using UV light to achieve feature sizes as small as 3.86 μm. The highest PLQY of the PQD–PNC film (47%) is greater than that of the neat QD film (40%), while the stability of the PQD–PNC is also better than that of the neat film, presumably because of the hydrophobic nature of PVCN. These results suggest the high potential of PQD–PNCs as effective CCLs for future micro-LEDs. [ABSTRACT FROM AUTHOR]

Surface lattice plasmon resonances (SLPR) in periodic arrays of metal nanostructures can feature a narrow spectral linewidth in case of the spectral overlap between the localized plasmons and Rayleigh anomalies. However, because of strong angular dispersion in experimental realizations, the excitation of SLPR requires collimated light, which has high spatial coherence. Here, excellent quality (Q)‐factor preservation in 1D all‐metallic nanograting metasurfaces due to the unique angular dispersion is reported. A high Q‐factor around 400 is obtained even when poor collimation, a numerical aperture (NA) objective with NA = 0.4, is employed for focusing the excitation light. With the advantages of highly focused excitation and high Q‐factor of the SLPR, a strong enhancement of second harmonic generation is realized from the proposed metasurface integrated with a few‐layers of GaSe flake. The results demonstrate that a 1D all‐metallic nanograting metasurface can overcome the demand for collimated light for the SLP resonances and manipulate focused light beams. The avenue of research proposed in this paper can open the door for the use of plasmonic metamaterials with SLPRs in many practical applications involving poorly coherent light sources, like the optoelectronic devices utilizing solar and daylight illuminations. [ABSTRACT FROM AUTHOR]

Aluminum nanoparticles attract scientific interest as a promising low-cost material with strong plasmon resonance in the ultraviolet region, which can be used in various fields of photonics. In this paper, for the first time, ultraviolet luminescence of zinc oxide nanoparticles in colloid solutions and nanostructure films in the presence of plasmonic aluminum nanoparticles 60 nm in size with a metal core and an aluminum oxide shell were studied. Mixture colloids of ZnO and Al nanoparticles in isopropyl alcohol solution with concentrations from 0.022 to 0.44 g/L and 0.057 to 0.00285 g/L, correspondingly, were investigated. The enhancement of up to 300% of ZnO emission at 377 nm in colloids mixtures with metal nanoparticles due to formation of Al-ZnO complex agglomerates was achieved. Plasmon nanostructures with different configurations of layers, such as Al on the surface of ZnO, ZnO on Al, sandwich-like structure and samples prepared from a colloidal mixture of ZnO and Al nanoparticles, were fabricated by microplotter printing. We demonstrated that photoluminescence can be boosted 2.4-fold in nanostructures prepared from a colloidal mixture of ZnO and Al nanoparticles, whereas the sandwich-like structure gave only 1.1 times the amplification of luminescence. Calculated theoretical models of photoluminescence enhancement of ideal and weak emitters near aluminum nanoparticles of different sizes showed comparable results with the obtained experimental data. [ABSTRACT FROM AUTHOR]

Plentiful research of InP semiconductor quantum dots (QDs) has been launched over the past few decades for their excellent photoluminescence properties and environmentally friendly characteristics in various applications. However, InP QDs show inferior photostability because they are extremely sensitive to the ambient environment. In this study, we propose a novel method to enhance the photostability of InP/ZnSe/ZnS QDs by doping zirconium into the ZnS layer. We certify that Zr can be oxidized to Zr oxides, which can prevent the QDs from suffering oxidation during light irradiation. The InP/ZnSe/ZnS:Zr QDs maintained 78% of the original photoluminescence quantum yields without significant photodegradation under the irradiation of LED light (450 nm, 3.0 W power intensity) for 14 h, while conventional InP/ZnSe/ZnS QDs dramatically decreased to 29%. [ABSTRACT FROM AUTHOR]

Highly efficient broadband photodetectors based on 2D metal chalcogenides have enchanted immeasurable research curiosity due to their tunable bandgap and unique electrical properties suitable for applications in optoelectronic nanodevices. In the present study, we fabricated photodetectors based on heterojunctions composed of 2D nanoflakes of indium sulfide (In2S3) and ZnO with the aim to enhance the photodetection spectral range. The fabricated 2D–3D heterostructure exhibited superior photodetection performance in terms of a high responsivity (Rλ), specific detectivity, and external quantum efficiency with a broader spectral response extending from the UV to visible region. It displayed a high responsivity value of 440 mA W−1, specific detectivity of 10 × 1010 Jones, and external quantum efficiency of 330%. The experimentally measured optical absorption edge, work function, and valence band offset confirmed the formation of a type-II band alignment at the β-In2S3–ZnO interface, which promoted the charge-carrier separation. The present study presents a novel way of enhancing the photodetector properties by combining a well-known oxide semiconductor with a 2D material having tunable optical properties. [ABSTRACT FROM AUTHOR]

Pure and Molybdenum (Mo)-doped zinc oxide (ZnO) nanoparticles were prepared by a cost-effective combustion synthesis route. XRD results revealed the decrement in crystallite size of ZnO with an increase in Mo-doping concentration. Optical bandgap (Eg) values were determined using optical reflectance spectra of these films measured in the range of 190–800 nm. The Eg values decreased with increasing the Mo-doping concentration. The dielectric properties of these samples were studied to determine the dielectric constant values. Raman spectra of these samples were recorded to know the structure. These sample absorption spectra were recorded for electrocatalytic applications. All the prepared samples were subjected to electrocatalytic degradation of Rhodamine B. The 0.01 wt% Mo doped ZnO showed 100% in 7 min electrocatalytic degradation. [ABSTRACT FROM AUTHOR]