Nano-Sized Minerals from Lower Cretaceous Sandstones in Israel Observed by Transmission Electron Microscopy (TEM)

Fine fraction in quartz arenite sandstones from Lower Cretaceous Hatira formation in Israel was observed by Transmission electron microscope (TEM). Samples were collected from Hatira and Ramon craters located in southern part of Israel and from Manara cliff from the northern part of Israel. The additional phases cause yellow, red, dark red and dark violet colors of the layered sandstones. The motivation was to identify the minerals of the fine factions that cause the variations in the colors. The minerals observed were clay minerals, mainly kaolinite (Al4Si4O20(OH)8), some illite (K0.65Al2.0[Al0.65Si3.35O10](OH)2) and smectite. Iron oxides were goethite (FeOOH) and hematite (Fe2O3), Titanium-iron oxides observed was ilmenite (FeTiO3), and Titanium-oxides were rutile (TiO2), and anatase (TiO2). Sulphates observed were jarosite (KFe3(SO4)2(OH)6) and alunite (KAl3(SO4)2(OH)6). Some of the hematite was formed by recrystallization of goethite. Ilmenite disintegrated into small iron oxides mainly hematite. Euhedral to sub-hedral rutile (TiO2) and anatase (TiO2) were preserved in clay-minerals. Crystals of alunite and jarosite were observed in sandstones in both craters. They probably crystallized due to some transgression of the Thetis Sea

High-resolution transmission electron microscopy study of Fe-Mn oxides in the hydrothermal sediments of the Red Sea deeps system

Deepsediments from the Red Sea have been studied extensively and provide a rich resource for understanding mineral transformations under hydrothermal conditions. Interrelationships among various sampling sites, however, are still rather incomplete. The purpose of the present study was to increase understanding of these systems by characterizing and comparing the Fe-Mn oxyhydroxides from the southern Atlantis II, Chain A, Chain B, and Discovery Deeps, using high-resolution transmission electron microscopy. Some of the hydrothermal sediments of Chain A are dominated by Si-associated Fe oxides (ferrihydrite, goethite, lepidocrocite, and short-range ordered, rounded particles) resembling the hydrothermal sediments of the SW basin in the Atlantis II Deep, indicating sub-bottom connections between the Deeps. Although some of the sediments of the Discovery Deep show a similar trend; short-range ordered, rounded particles were not detected in these sediments, implying that crystallization of this short-range ordered phase is sensitive to the Si/Fe ratio in the brine and only at elevated ratios does it crystallize out of the brine. Silicon-associated and Fe-enriched Mn oxyhydroxides such as groutite, manganite, todorokite, and Mn-dominated lathlike layers occasionally contain Ca and Mg impurities. Manganese substitutes for Fe and vice versa, leading to a solid-solution series between goethite and groutite and Mn-enriched ferrihydrite. Hematite is the only Fe oxide in the hydrothermal sediments that is found to be lacking in impurities, which is probably due to its formation by recrystallization from other Fe oxides

Water-Soluble Lead Sulfide Nanoparticles: Direct Synthesis and Ligand Exchange Routes

Colloidal semiconductor nanoparticles (NPs) represent an emergent state of matter with unique properties, bridging bulk materials and molecular structures. Their distinct physical attributes, such as bandgap and photoluminescence, are intricately tied to their size and morphology. Ligand passivation plays a crucial role in shaping NPs and determining their physical properties. Ligand exchange (LE) offers a versatile approach to tailoring NP properties, often guided by Pearson’s Hard–Soft Acid–Base theory. Lead sulfide (PbS), a semiconductor of considerable interest, exhibits size-dependent tunable bandgaps from the infrared to the visible range. Here, we present two methods for synthesizing water-soluble, polyvinylpyrrolidone (PVP)-coated PbS NPs. The first involves direct synthesis in an aqueous solution while utilizing PVP as the surfactant for the formation of nano-cubes with a crystal coherence length of ~30 nm, while the second involves LE from octadecylamine-coated PbS truncated nano-cubes to PVP-coated PbS NPs with a crystal coherence length of ~15 nm. Multiple characterization techniques, including X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy, and thermal gravimetric analysis, confirmed the results of the synthesis and allowed us to monitor the ligand exchange process. Our findings demonstrate efficient and environmentally friendly approaches for synthesizing PVP-coated PbS NPs

Twinning and Phase Control in Template-Directed ZnS and (Cd,Zn)­S Nanocrystals

We report on the nucleation and growth of ZnS and (Cd_<i>x</i>­Zn_1–<i>x</i>)­S nanocrystals on polydiacetylene Langmuir films. It was found that the 3–5 nm nanocrystals form ordered linear arrays aligned at a constant 27° angle with respect to the conjugated direction of the polydiacetylene film, as derived from the optimal alignment between the two phases. ZnS nanocrystals were found to nucleate specifically from the zinc blende (001) face. Because of closely matched interfacial relations, twinning defects were induced on the {111} planes. These nanometer-sized twin crystals exhibit extra {111} electron diffraction reflections due to elongation of reciprocal space spots, despite their off axis orientation. The composition of solid solution (Cd,Zn)­S nanocrystals depends on the Zn²⁺\Cd²⁺ ratio in the aqueous subphase. Their structure is affected by the template mismatch both by twinning, as is the case for ZnS, for which continuous compositional shift is observed, and by phase shift to hexagonal wurtzite, with a pure CdS composition. The nanocrystals exhibited a continuous energy-gap shift, reflecting the Zn/Cd ratio in the solid solution. We demonstrate control over the nanocrystals’ crystal structure, defect structure, orientation, and composition, providing a potentially effective tool for band-gap engineering in organic–inorganic hybrid assemblies

New Nanocrystalline Materials: A Previously Unknown Simple Cubic Phase in the SnS Binary System

We report a new phase in the binary SnS system, obtained as highly symmetric nanotetrahedra. Due to the nanoscale size and minute amounts of these particles in the synthesis yield, the structure was exclusively solved using electron diffraction methods. The atomic model of the new phase (<i>a</i> = 11.7 Å, <i>P</i>2₁3<i>)</i> was deduced and found to be associated with the rocksalt-type structure. Kramers–Kronig analysis predicted different optical and electronic properties for the new phase, as compared to α-SnS

Synthesis of Ti1-xWx Solid Solution MAX Phases and Derived MXenes for Sodium-Ion Battery Anodes

One of the distinguishing features of MAX phases and their MXene derivatives is their remarkable chemical diversity. This diversity, coupled with the two-dimensional nature of MXenes, positions them as outstanding candidates for a wide range of electrochemical applications. In this study, we report the synthesis of M site T1-xWx solid solution MAX phases, specifically (Ti1-xWx)2AlC and (Ti1-xWx)3AlC2. The 211-type phase exhibited a disordered solid solution, whereas the 312-type phase displayed a more ordered structure, resembling an o-MAX arrangement, with W atoms preferentially occupying the outer planes. This specific ordering in the 312-type MAX phase is attributed to the unique electronic structure and atomic radius of W, indicating that these characteristics are crucial for the preferential occupation of the outer planes. Moreover, corresponding solid-solution MXenes, Ti2.4W0.6C2Tz and Ti1.6W0.4CTz, were synthesized via selective etching of MAX powder precursors containing 20% W. These MXenes were evaluated as sodium-ion battery anodes, with Ti1.6W0.4CTz showing exceptional capacity, outperforming existing multilayer MXene chemistries. This work not only demonstrates the successful integration of W in meaningful quantities into a double transition metal solid solution MAX phase, but also paves the way for the development of cost-effective MXenes containing W. Such advancements significantly widen their application spectrum by fine-tuning their physical, electronic, mechanical, electrochemical, and catalytic properties

Oriented Attachment: A Path to Columnar Morphology in Chemical Bath Deposited PbSe Thin Films

We have studied columnar PbSe thin films obtained using chemical bath deposition. The columnar microstructure resulted from an oriented attachment growth mechanism, in which nuclei precipitating from solution attached along preferred crystallographic facets to form highly oriented, size-quantized columnar grains. This is shown to be an intermediate growth mechanism between the ion-by-ion and cluster growth mechanisms. A structural zone model depicting the active growth mechanisms is presented for the first time for semiconductor thin films deposited from solution. The columnar films showed well-defined twinning relations between neighboring columns, which exhibited 2D quantum confinement, as established by photoluminescence spectroscopy. In addition, anisotropic nanoscale electrical properties were investigated using current sensing AFM, which indicated vertical conductivity, while maintaining quantum confinement