Optical Orientation Research Articles

Gysinite-(Ce), PbCe(CO3)2(OH)(H2O), a New Member of the Ancylite Group

Abstract The new mineral gysinite-(Ce), PbCe(CO3)2(OH)(H2O) (IMA2023-035), was found at the Abendröthe Mine, St. Andreasberg, Braunlage, Goslar district, Lower Saxony, Germany, where it occurs in a single vug in association with albite, calcite, and mimetite. It is a secondary oxidation-zone mineral presumably crystallized from hydrothermal solutions. Gysinite-(Ce) occurs in intergrowths of equant pseudo-octahedral crystals, up to about 0.7 mm in maximum dimension. The color is brownish yellow, the streak is pale yellow, and the luster is vitreous to subadamantine. The mineral is brittle with curved, irregular fracture and no cleavage. The Mohs hardness is about 3½. The calculated density is 5.136 g/cm3. The mineral is biaxial (−) with α = 1.750(5), β = 1.825(5), γ = 1.860(5). The 2V is 65.1(4)° with no observable dispersion. The optical orientation is X = c; Y = a; Z = b by analogy with gysinite-(Nd) and there is no pleochroism. Electron probe microanalyses provided the empirical formula (Pb0.930Ce0.434La0.349Nd0.196Pr0.048Gd0.037Sm0.007)Σ2.000(CO3)2(OH)1.074(H2O)0.926. Gysinite-(Ce) is orthorhombic, Pmcn, a = 5.0780(4), b = 8.6689(6), c = 7.3255(6) Å, V = 322.47(4) Å3, and Z = 2. Gysinite-(Ce) is isostructural with gysinite-(La), gysinite-(Nd), and other members of the ancylite group. The crystal structure (R1 = 0.0268 for 396 I > 2σI) is a framework consisting of edge-sharing (PbCe)O8(OH)(H2O) polyhedra and CO3 triangles.

Error analysis based on a tunable wave plate polarization interferometric imaging spectrometer

Interference imaging spectroscopy combines modern imaging technology with spectral technology, holding significant importance for object imaging and spectral detection. This article introduces the principle of an adjustable wave plate polarization interferometric imaging spectrometer. The example design specifications are set for an observation wavelength range of 450–780 nm and a maximum resolution of 2 nm at 450 nm, with a 0.5 in detector as the base for calculating the specific dimensions of the Soleil–Babinet compensator. An investigation was conducted on the issues of nonuniform sampling, as well as three types of mechanical errors: flatness, wedge angle tolerance, and optical axis orientation accuracy. Emphasis was placed on discussing the impact of these errors on the instrument’s optical path difference and spectral reconstruction accuracy. This research provides theoretical guidance for the design and engineering of this miniaturized imaging spectrometer.

Encryption-decryption scheme in a single-pixel system based on polarization and Laguerre-Gaussian mode modulation

Optical cryptosystems are crucial for ensuring the security of optical information transmission and storage. The indirect measurement mechanism of single-pixel imaging (SPI) offers a feasible implementation channel for optical cryptosystems. Illumination patterns are encryption keys projected onto the plaintext object, while the intensity collected by the single-pixel detector forms the ciphertext. However, the variations in the object's angular position during SPI measurement generally introduce certain inaccuracies in image reconstruction. And due to SPI's input-output linear mapping relationship, the plaintext is vulnerable to exposure. This proposes an encryption-decryption scheme in a single-pixel system based on polarization and Laguerre-Gaussian (LG) mode modulation. The inherent circular symmetry of LG mode makes the angular position of the object information that can be encrypted, while the intrinsic properties of the object can be represented by polarization. Our system characterizes various polarization parameters of samples serving as reliable plaintext with an error of less than 4.2%, including depolarization, diattenuation, and retardance. For encryption demonstration, LG modes are randomly divided into 5 groups, corresponding to an object at different rotational states. This, combined with 16 polarization modulations, constructs pattern-angle-polarization joint keys, enabling high-security encryption as well as high-fidelity decryption of the mask image, optical axis orientation, and retardance of the test sample. Experimental results demonstrate the effectiveness of our scheme in enhancing the security and information complexity of optical cryptography, offering valuable insights for optical communication and quantum information security.

Three-dimensional fiber orientation mapping of the human brain at micrometer resolution.

The accurate measurement of three-dimensional (3D) fiber orientation in the brain is crucial for reconstructing fiber pathways and studying their involvement in neurological diseases. Comprehensive reconstruction of axonal tracts and small fascicles requires high-resolution technology beyond the ability of current in vivo imaging (e.g. diffusion magnetic resonance imaging). Optical imaging methods such as polarization-sensitive optical coherence tomography (PS-OCT) and polarization microscopy can quantify fiber orientation at micrometer resolution but have been limited to two-dimensional in-plane orientation or thin slices, preventing the comprehensive study of connectivity in 3D. In this work we present a novel method to quantify volumetric 3D orientation in full angular space with PS-OCT. We measure the polarization contrasts of the brain sample from two illumination angles of 0 and 15 degrees and apply a computational method that yields the 3D optic axis orientation and true birefringence. We further present 3D fiber orientation maps of entire coronal cerebrum sections and brainstem with 10 μm in-plane resolution, revealing unprecedented details of fiber configurations. We envision that our method will open a promising avenue towards large-scale 3D fiber axis mapping in the human brain as well as other complex fibrous tissues at microscopic level.

Imaging of developing human brains with ex vivo PSOCT and dMRI.

The human brain undergoes substantial developmental changes in the first five years of life. Particularly in the white matter, myelination of axons occurs near birth and continues at a rapid pace during the first 2 to 3 years. Diffusion MRI (dMRI) has revolutionized our understanding of developmental trajectories in white matter. However, the mm-resolution of in vivo techniques bears significant limitation in revealing the microstructure of the developing brain. Polarization sensitive optical coherence tomography (PSOCT) is a three-dimensional (3D) optical imaging technique that uses polarized light interferometry to target myelinated fiber tracts with micrometer resolution. Previous studies have shown that PSOCT contributes significantly to the elucidation of myelin content and quantification of fiber orientation in adult human brains. In this study, we utilized the PSOCT technique to study developing brains during the first 5 years of life in combination with ex vivo dMRI. The results showed that the optical properties of PSOCT quantitatively reveal the myelination process in young children. The imaging contrast of the optic axis orientation is a sensitive measure of fiber orientations in largely unmyelinated brains as young as 3-months-old. The micrometer resolution of PSOCT provides substantially enriched information about complex fiber networks and complements submillimeter dMRI. This new optical tool offers great potential to reveal the white matter structures in normal neurodevelopment and developmental disorders in unprecedented detail.

Fast, Efficient Tailoring Growth of Nanocrystalline Diamond Films by Fine-Tuning of Gas-Phase Composition Using Microwave Plasma Chemical Vapor Deposition.

Nanocrystalline diamond (NCD) films are attractive for many applications due to their smooth surfaces while holding the properties of diamond. However, their growth rate is generally low using common Ar/CH4 with or without H2 chemistry and strongly dependent on the overall growth conditions using microwave plasma chemical vapor deposition (MPCVD). In this work, incorporating a small amount of N2 and O2 additives into CH4/H2 chemistry offered a much higher growth rate of NCD films, which is promising for some applications. Several novel series of experiments were designed and conducted to tailor the growth features of NCD films by fine-tuning of the gas-phase compositions with different amounts of nitrogen and oxygen addition into CH4/H2 gas mixtures. The influence of growth parameters, such as the absolute amount and their relative ratios of O2 and N2 additives; substrate temperature, which was adjusted by two ways and inferred by simulation; and microwave power on NCD formation, was investigated. Short and long deposition runs were carried out to study surface structural evolution with time under identical growth conditions. The morphology, crystalline and optical quality, orientation, and texture of the NCD samples were characterized and analyzed. A variety of NCD films of high average growth rates ranging from 2.1 μm/h up to 6.7 μm/h were successfully achieved by slightly adjusting the O2/CH4 amounts from 6.25% to 18.75%, while that of N2 was kept constant. The results clearly show that the beneficial use of fine-tuning of gas-phase compositions offers a simple and effective way to tailor the growth characteristics and physical properties of NCD films for optimizing the growth conditions to envisage some specific applications.

Highly-Polarized Emission Provided by Giant Optical Orientation of Exciton Spins in Lead Halide Perovskite Crystals.

Quantum technologic and spintronic applications require reliable material platforms that enable significant and long-living spin polarization of excitations, the ability to manipulate it optically in external fields, and the possibility to implement quantum correlations between spins, i.e., entanglement. Here it is demonstrated that these conditions are met in bulk crystals of lead halide perovskites. A giant optical orientation of 85% of excitons, approaching the ultimate limit of unity, in FA0.9Cs0.1PbI2.8Br0.2 crystals is reported. The exciton spin orientation is maintained during the exciton lifetime of 55ps resulting in high circular polarization of the exciton emission. The optical orientation is robust to detuning of the excitation energy up to 0.3eV above the exciton resonance and remains larger than 20% up to detunings of 0.9eV. It evidences pure chiral selection rules and suppressed spin relaxation of electrons and holes, even with large kinetic energies. The exciton and electron-hole recombinations are distinguished by means of the spin dynamics detected via coherent spin quantum beats in magnetic field. Further, electron-hole spin correlations are demonstrated through linear polarization beats after circularly polarized excitation. These findings are supported by atomistic calculations. All-in-all, the results establish lead halide perovskite semiconductors as suitable platform for quantumtechnologies.

Visualization enhancement by PCA-based image fusion for skin burns assessment in polarization-sensitive OCT.

Polarization-sensitive optical coherence tomography (PS-OCT) is a functional imaging tool for measuring tissue birefringence characteristics. It has been proposed as a potentially non-invasive technique for evaluating skin burns. However, the PS-OCT modality usually suffers from high system complexity and relatively low tissue-specific contrast, which makes assessing the extent of burns in skin tissue difficult. In this study, we employ an all-fiber-based PS-OCT system with single-state input, which is simple and efficient for skin burn assessment. Multiple parameters, such as phase retardation (PR), degree of polarization uniformity (DOPU), and optical axis orientation, are obtained to extract birefringent features, which are sensitive to subtle changes in structural arrangement and tissue composition. Experiments on ex vivo porcine skins burned at different temperatures were conducted for skin burn investigation. The burned depths estimated by PR and DOPU increase linearly with the burn temperature to a certain extent, which is helpful in classifying skin burn degrees. We also propose an algorithm of image fusion based on principal component analysis (PCA) to enhance tissue contrast for the multi-parameter data of PS-OCT imaging. The results show that the enhanced images generated by the PCA-based image fusion method have higher tissue contrast, compared to the en-face polarization images by traditional mean value projection. The proposed approaches in this study make it possible to assess skin burn severity and distinguish between burned and normal tissues.

New Minerals from the Redmond Mine, North Carolina, USA: VII. Zincochenite, the Zn Analogue of Chenite

Abstract The new mineral zincochenite, Pb4Zn(OH)6(SO4)2 (IMA2022-025), was found in the Redmond mine, Haywood County, North Carolina, USA, where it occurs in a highly unusual secondary assemblage that comprises a variety of rare Pb-Zn-Cu sulfates, thiosulfates, and carbonates. Zincochenite was found in vugs in massive galena-sphalerite-chalcopyrite-quartz in close association with bechererite, chenite, cherokeeite, elyite, lanarkite, and steverustite. Zincochenite crystals vary in habit including tablets, blades, and prisms, up to about 0.5 mm in maximum dimension. Crystals always occur in tightly intergrown subparallel clusters. The color is most commonly light blue, the streak is white, and the luster is vitreous to resinous. The mineral is brittle with curved and irregular fracture and one fair cleavage, probably on . The Mohs hardness is about 3½. The calculated density is 5.939 g/cm3. The mineral is biaxial (−) with α = 1.875(5), β = 1.900(5), γ = 1.915(5). The 2V is 78.4(5)° with strong r > v dispersion. The partially determined optical orientation is Y ≈ and there is no pleochroism. Electron microprobe analyses provided the empirical formula Pb4.00(Zn0.94Cu2+0.06)Σ1.00(SO4)1.81(S2O3)0.19(OH)6. Zincochenite is triclinic, P, a = 5.883(4), b = 7.938(5), c = 7.948(5) Å, α = 110.511(12), β = 98.497(10), γ = 100.152(8)°, V = 333.2(3) Å3, and Z = 1. Zincochenite is isostructural with chenite. In the crystal structure (R1 = 0.0874 for 936 I > 2σI), short bonds between the Pb atoms and OH groups define a chain along [011] and these chains are bridged by ZnO2(OH)4 octahedra to form sheets parallel to . SO4 tetrahedra decorate both sides of the sheets. The sheets are linked together in the direction via long Pb–O bonds and hydrogen bonds.

Negative reflection and total internal reflection at the internal surface of lithium niobate crystal

In this paper we analytically find out the expression for the wave vector and Poynting vector in the reflection domain for negative uniaxial material. We investigate the impact of the optical axis rotation and incident angle on the wave vector and Poynting vector reflected from the internal surface of lithium niobate crystal when the light is propagating from the denser anisotropic medium to the rarer isotropic medium. We derive the Brewster angle condition and discuss the walk-off between TE and TM polarized light. We explore where the wave vector and Poynting vector are parallel after reflection. In further analysis, we look into the phase differences between ordinary and extraordinary reflected light after total internal reflection from the internal surface of lithium niobate crystal. The necessary conditions for linear polarization and circular polarization have been established. The impact of optical axis orientation is also taken into consideration. The refractive index for the isotropic material for the desired polarization response has been found as 2.18, 2.1, and 2.03 at 632 nm, 1550 nm, and 3500 nm, respectively.

Sperlingite, (H2O)K(Mn2+Fe3+)(Al2Ti)(PO4)4[O(OH)][(H2O)9(OH)]⋅4H2O, a new paulkerrite-group mineral, from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany

Abstract Sperlingite, (H2O)K(Mn2+Fe3+)(Al2Ti)(PO4)4[O(OH)][(H2O)9(OH)]⋅4H2O, is a new monoclinic member of the paulkerrite group, from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany. It was found in corrosion pits of altered zwieselite, in association with columbite, hopeite, leucophosphite, mitridatite, scholzite, orange–brown zincoberaunite sprays and tiny green crystals of zincolibethenite. Sperlingite forms colourless prisms with pyramidal terminations, which are predominantly only 5 to 20 μm in size, rarely to 60 μm and frequently are multiply intergrown and are overgrown with smaller crystals. The crystals are flattened on {010} and slightly elongated along [100] with forms {010}, {001} and {111}. Twinning occurs by rotation about c. The calculated density is 2.40 g⋅cm–3. Optically, sperlingite crystals are biaxial (+), α = 1.600(est), β = 1.615(5), γ = 1.635(5) (white light) and 2V (calc.) = 82.7°. The optical orientation is X = b, Y = c and Z = a. Neither dispersion nor pleochroism were observed. The empirical formula from electron microprobe analyses and structure refinement is A 1[(H2O)0.96K0.04]Σ1.00 A 2(K0.52□0.48)Σ1.00 M 1(Mn2+0.60Mg0.33Zn0.29Fe3+0.77)Σ1.99 M 2+M3(Al1.05Ti4+1.33Fe3+0.62)Σ3.00(PO4)4 X [F0.19(OH)0.94O0.87]Σ2.00[(H2O)9.23(OH)0.77]Σ10.00⋅3.96H2O. Sperlingite has monoclinic symmetry with space group P21/c and unit-cell parameters a = 10.428(2) Å, b = 20.281(4) Å, c = 12.223(2) Å, β = 90.10(3)°, V = 2585.0(8) Å3 and Z = 4. The crystal structure was refined using synchrotron single-crystal data to wRobs = 0.058 for 5608 reflections with I > 3σ(I). Sperlingite is the first paulkerrite-group mineral to have co-dominant divalent and trivalent cations at the M1 sites; All other reported members have Mn2+ or Mg dominant at M1. Local charge balance for Fe3+ at M1 is achieved by H2O → OH– at H2O coordinated to M1.

Casimir interaction driven by hyperbolic polaritons

Abstract Casimir interaction is an intriguing phenomenon that is induced by electromagnetic quantum fluctuations, which dominates the interaction between microstructures at small separations and is essential for micro- and nano-electromechanical systems (MEMS and NEMS). However, Casimir interaction driven by hyperbolic polaritons remains an unexplored frontier. In this work, we investigate the Casimir interaction between natural hyperbolic material hexagonal boron nitride from the perspective of force distribution with different optical axis orientations for the first time. The attractive Casimir force is remarkably enhanced due to the excitation of volume-confined hyperbolic polaritons (HPs). Furthermore, distinct repulsive contributions to the force are observed due to surface-confined HPs that only exist when the optical axis is in-plane. The HPs are associated with a striking thickness dependence of spectral force properties, suggesting that the discrete volume-confined HPs lead to the attractive-repulsive transition of Casimir force. This work sheds light on the relation between HPs and the vacuum fluctuation-induced force, which could offer new opportunities for the development of the MEMS and NEMS.

Magnetic resonance frequency shifts in quantum magnetometers based on the phenomenon of the optical orientation of atoms

Subject of study. Magnetic resonance frequency shifts caused by spin exchange collisions involving optically oriented alkali atoms in the ground state are studied. Aim of study. Spin-exchange collisions involving optically oriented pairs of alkali atoms of different types are theoretically studied to determine the shifts in the magnetic resonance line frequencies as a function of temperature for various pairs of alkali atoms under various optical orientation conditions in order to determine optimum constraints for the construction of quantum magnetometers with optical pumping using mixtures of alkali atoms. Method. Collisions between optically oriented alkali atoms are analyzed within the framework of quantum scattering theory, and data on the interaction potentials of alkali-atom dimers are used to calculate the scattering phases for collisions involving these potentials and the imaginary parts of the complex spin-exchange cross-section. The resulting cross sections as a function of energy were used to determine the magnetic resonance frequency shifts as a function of temperature. Main results. The magnetic resonance line frequency shifts for the following pairs of alkali atoms were obtained as a function of temperature: 39K−133Cs, 39K−85Rb, and 133Cs−85Rb. The shift in the magnetic resonance line involving the F=1 hyperfine state for a 39K−85Rb alkali-atom pair was found to pass through zero near temperature 480 K. Practical significance. The results obtained in this paper can be used to develop zero-spin-exchange-shift quantum electronic devices based on the optical orientation of atoms. In particular, it is possible to develop co-magnetometers based on the optical orientation of alkali atoms.

Spatial shifts of reflected rotating elliptical Gaussian beams from surface phonon polaritons in hyperbolic materials

The effect of surface phonon polaritons (SPhPs) on Goos-Hänchen (GH) and Imbert-Fedorov (IF) shifts of reflected rotating elliptical Gaussian beams (REGBs) is investigated in the Otto configuration with a naturally hyperbolic material (NHM) substrate. The spatial shifts are enhanced significantly and adjusted by tuning the REGBs and the optical axis orientation of NHM. The magnitude of GH and IF shifts is easily evaluated by timing the elliptical parameter b02 on the basis of the spatial shift at b0=1.0 when η(=a0/b0)≥2.0. The attenuation total reflection (ATR) spectra are simulated for a hexagonal boron nitride (hBN) substrate. To better understand the impact of SPhPs on the GH and IF shifts, the dispersion curves of SPhPs are calculated. The features of GH and IF shifts around SPhPs can be observed through the frequency scanning along the dispersion curves at a fixed incident angle. The comparison between the ATR spectra and the dispersion curves demonstrates that the enhancement of GH and IF shifts with higher reflection always occurs in the reststrahlen bands (RBs) of NHM once SPhPs are excited. In RB-I, the magnitudes of GH and IF shifts attributable to the SPhPs are located between the peak and dip of a shift curve within a very narrow frequency region. However, in RB-II, the positive maximum values of GH and IF shifts just coincide with the SPhPs. As a result, it is predicted that a relatively large spatial shift will be observed along the frequency scanning line. The large shifts accompanied by the higher reflection may show potential applications in optical or optoelectronic technologies.

Désorite, Pb2(Fe3+6Zn)O2(PO4)4(OH)8, a New Phosphate Mineral Isotypic with Jamesite

The new mineral désorite, Pb2(Fe3+6Zn)O2(PO4)4(OH)8, is a secondary oxidation-zone mineral discovered on the dumps of the Schöne Aussicht mine, Dernbach, Westerwaldkreis, Rhineland-Palatinate, Germany. The crystals are irregular blades up to about 0.25 mm long, occurring in subparallel and radial aggregates. Désorite is brownish red. It has an orange streak, adamantine luster, brittle tenacity, splintery and curved fracture and two cleavages: {021¯} perfect and {001} good. It has a hardness (Mohs) of about 3 and is nonfluorescent in both long- and short-wave ultraviolet illumination. The calculated density is 4.633 g/cm3. Optically, crystals are biaxial (+) with α = 2.00(1), β = 2.02(calc) and γ = 2.10(calc) (white light). The 2V is 54(2)° and the optical orientation is Y ~⊥{021¯}, X ∧ a ≈ 13°. The mineral is pleochroic: X yellow brown, Y red brown, Z red brown; X < Y ≈ Z. The empirical formula from electron microprobe analysis is Pb1.93(Zn0.50Fe3+6.29☐0.21)Σ7.00(P3.90As0.10)Σ4.00O26H8.28. Désorite is triclinic, space group P1¯; the unit-cell parameters are a = 5.4389(7), b = 9.3242(13), c = 10.0927(12) Å, α = 109.024(8), β = 90.521(6), γ = 97.588(7)°, V = 478.90(11) Å3 and Z = 1. Désorite has a framework structure (R1 = 0.0487 for 937 I > 2σI reflections) assembled from Fe3+O6 octahedra and PO4 tetrahedra, with Pb occupying cavities in the framework. The Fe3+O6 octahedra in the framework occur in edge-sharing chains, edge-sharing trimers and individual octahedra, all sharing corners with each other and with PO4 tetrahedra. Désorite is isostructural with jamesite and lulzacite.

Unsupervised topological analysis of polarized light microscopy: application to quantitative birefringence imaging.

The determination of birefringence (magnitude and axis orientation) of optical materials is of significant interest in various fields. In the case of composite samples, this task becomes complicated and time-consuming; therefore, a partially automated procedure for reconstructing birefringence spatial distribution becomes valuable. Herein, we propose a procedure to reconstruct the spatial distributions of the retardance and optical axis orientation in a geological thin section from sparse quantitative birefringence measurements, using automatic boundary detection on cross-polarized light microscopy images. We examine two particular areas on the selected geological thin section: one that presents a uniaxial crystal with a circular cross-section of its refractive index ellipsoid and the other with grains of varying orientations. The measurement gives the orientation of the grain's optical axis both in and out of the plane of the thin section, which explains the qualitative observations with the cross-polarized light microscope. Future work will connect the measured orientation of the rock thin section with its 3D geological orientation in the field.

Plumbogaidonnayite, PbZrSi3O9⋅2H2O, a new Pb-member of the gaidonnayite group from the Saima alkaline complex, Liaoning Province, China

AbstractPlumbogaidonnayite, ideally PbZrSi3O9⋅2H2O, is a new gaidonnayite-group mineral discovered as a secondary product derived from the alteration of eudialyte from the Saima alkaline complex, China. It occurs as aggregates (up to 1 mm) composed of subhedral to anhedral or platy crystals (individually 5–50 μm), associated closely with microcline, natrolite, aegirine, gaidonnayite, georgechaoite, zircon, bobtraillite and britholite-(Ce) in eudialyte pseudomorphs. The crystals are transparent, colourless or light brown with a vitreous lustre. Plumbogaidonnayite is brittle with conchoidal fracture, and it has a Mohs hardness of ~5 and a calculated density of 3.264 g/cm3. It is optically biaxial (+) with α = 1.61(3), β = 1.63(3) and γ = 1.66(4). The calculated 2V is 80°, with the optical orientations X, Y and Z parallel to the crystallographic a, b and c axes, respectively. The empirical formula is (Pb0.70Ca0.17Ba0.01K0.11Na0.01Y0.01)Σ1.01(Zr1.00Hf0.01Ti0.01)Σ1.02Si3.01O9⋅2H2O calculated on the basis of nine oxygen atoms per formula unit and assuming the occurrence of two H2O groups. Plumbogaidonnayite is orthorhombic, P21nb, a = 11.7690(4) Å, b = 12.9867(3) Å, c = 6.66165(16) Å, V = 1018.17(5) Å3 and Z = 4. The nine strongest lines of its powder XRD pattern [d in Å (I, %) (hkl)] are: 6.489 (36) (020), 5.803 (100) (101), 4.661 (27) (021), 4.336 (29) (121), 3.640 (30) (221), 3.114 (79) (112), 2.947 (27) (400), 2.622 (27) (241) and 2.493 (27) (312). Plumbogaidonnayite has a similar spiral chain framework structure with gaidonnayite and georgechaoite, which is composed of SiO4 tetrahedra and ZrO6 octahedra, but with disordered extra-framework sites (cations and H2O groups) characterised by the substitution of 2Na+ (K+)→Pb2+ (Ca2+) + □ (vacancy). The discovery of plumbogaidonnayite adds a new perspective on the cation ordering and heterovalent substitution mechanism in gaidonnayite-group minerals.

THE WEATHERING PRODUCTS CREATING GOOD VITAL ENVIRONMENT TO BIOTA FOR BETTER DELIVERY SOIL ECOSYSTEM SERVICES

There is little information about the plasmic constituent intimate arrangement of the Phaeozem groundmass. In this respect, a micromorphological investigation of a Vertic Phaeozem (located in Perchiu Hill) was performed.The research results emphasise the presence of many types of striated birefringent fabric (b-fabric) in the groundmass of the pedogenetic horizons, induced by the swell-shrink processes (and representing criteria for the quantification of stress processes in Vertisols and vertic subgroups) as: porostriated and granostriated b-fabric, are rarely and weak developed; and both reticulate and parallel striated b-fabric developed on short distances. Into the pedogenetic horizons, rock fragments also appear in different degrees of weathering and integration into the groundmass, emphasising different evolution steps in the solification process. The linear and cross-linear alteration types of the rock fragments induced optical orientation of the clay domains similar to the different types of the striated b-fabric.It could be concluded, that the b-fabrics, which are generally used as criteria for the quantification of the swell-shrinking processes stress (that disturbed the plant roots development and the soil life environment) also formed in situ from the strong weathered rock fragments. Consequently, the striated b-fabric generated by the weathering process created a friendly environment in soil and underlined a less stress forces (during the swell-shrink processes) in the studied soil.The weathering products enriched the soils in the most precious constituents (the clay and nutrients) responsible for soil fertility, and further creating a good vital environment for biota to better delivery the soil ecosystem services.

Metal to insulator transition for conducting polymers in plasmonic nanogaps

Conjugated polymers are promising material candidates for many future applications in flexible displays, organic circuits, and sensors. Their performance is strongly affected by their structural conformation including both electrical and optical anisotropy. Particularly for thin layers or close to crucial interfaces, there are few methods to track their organization and functional behaviors. Here we present a platform based on plasmonic nanogaps that can assess the chemical structure and orientation of conjugated polymers down to sub-10 nm thickness using light. We focus on a representative conjugated polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), of varying thickness (2-20 nm) while it undergoes redox in situ. This allows dynamic switching of the plasmonic gap spacer through a metal-insulator transition. Both dark-field (DF) and surface-enhanced Raman scattering (SERS) spectra track the optical anisotropy and orientation of polymer chains close to a metallic interface. Moreover, we demonstrate how this influences both optical and redox switching for nanothick PEDOT devices.

Eco-benign synthesis of α-Fe2O3 mediated Trachyspermum ammi: A new insight to photocatalytic and bio-medical applications

Environmental contaminants are a golabl concern, and even at very low quantities, they can be extremely harmful to the aquatic ecosystem. Microbial resistance and photocatalysis are popular strategies for removing hazardous substances from the environment. The present study developed the green synthesis of α-Fe2O3 nanoparticles from Trachyspermum ammi plant leaf extract. The crystalline and structural stability of green synthesized α-Fe2O3 nanoparticles were studied by XRD. The surface morphology was investigated by TEM and FESEM equipped with EDX analysis. Metal, oxygen bond (Fe-O) and their interaction on the surfaces and their valency were explored from FTIR and XPS spectra. Optical orientations and electron movements were revealed from UV-DRS analysis. Visible light photocatalytic methylene blue degradation confirmed the largest surface area, rate of recombination, photo-excited charge carriers, photo-sensitivity range and radical generations of α-Fe2O3 nanoparticles. The green synthesized α-Fe2O3 nanoparticles bacterial susceptibility was examined by the well diffusion method using (10, 20, 50, 100) µg/L concentration of nanoparticles. The antibacterial activity enhanced with the higher concentration of α-Fe2O3 (100 µg/L). The gram-negative bacteria of E.coli has high bacterial susceptibility on α-Fe2O3 nanoparticles. The reactive oxygen species and OH radicals of α-Fe2O3 nanoparticles are demonstrated better resistivity against bacterial strains. The present study, therefore, suggested that the green synthesis would be an appropriate approach to synthesize the nanomaterials and confirming their suitability for use in industrial wastewater treatment and biomedical applications.