Low Symmetry Research Articles

Are lower limb symmetry and self-reported symptoms associated with functional and neuromuscular outcomes in Brazilian adults with anterior cruciate ligament reconstruction? A cross-sectional study

IntroductionAfter anterior cruciate ligament (ACL) reconstruction, determining readiness to return to participation is challenging. The understanding of which neuromuscular performance parameters are associated with limb symmetry and self-reported symptoms may be useful to improve monitoring the rehabilitation towards adequate decision-making to return. ObjectivesTo compare the ACL-operated and injury-free lower limbs regarding functional performance; and to investigate whether lower limb strength and functional performance are associated with self-reported symptoms and functional lower limb symmetry. MethodThirty-four participants were included. Functional performance was assessed by using the Y-Balance test, Single-leg Hop, and Functional Movement Screen. An isokinetic dynamometer was used to evaluate the strength levels in open and closed kinetic chains. The functional lower limb symmetry was calculated considering the single-leg hop test results for each lower limb. ResultsThere were no differences in dynamic balance (Y-Balance) between the operated and injury-free limbs. The operated limb presented a worst performance in the single-leg hop. Self-reported symptoms prevalence and lower limb symmetry were associated with knee extension strength and functional performance (Y-Balance). ConclusionIndividuals submitted to ACL-reconstruction presented worse functional performance in the operated limb compared to the injury-free limb. Both knee strength and dynamic balance were associated with limb symmetry and self-reported symptoms.

Correlation between Copper(II)-Lactate Complexes in Aqueous Alkaline Solutions and Copper(I) Oxide (Cu2O) Electrodeposited

Cuprous oxide (Cu2O) is a p-type semiconductor well-investigated as materials for photovoltaics and photoelectrodes due to its low cost. There is a number of reports on the Cu2O electrodeposition from aqueous alkaline electrolytes containing copper(II) salt and lactate ions as complex formers. Cu2O electrodeposition behaviors and several properties of resulting Cu2O are known to depend on the electrolyte pH, but mention of the reasons for this is limited. Recently, we have succeeded in identifying two different copper(II)-lactate complexes (1 and 2 in Table I) formed in the alkaline region depending on pH [1], and their formation constants determined made it possible to discuss the electrodeposition in terms of cathodic overpotential, or driving force, for the deposition. In addition, we found that the complexing took at least 1 day to reach equilibrium [2], suggesting that aging is mandatory after the preparation of electrolytes for reproducible electrodeposition. In this study, we prepared a set of thermodynamically well stabilized copper(II)-lactate electrolytes containing 0.4 M Cu(CH3COO)2·H2O and 3.0 M lactic acid, and compared the Cu2O electrodeposition at several different pH but unified overpotential from the CuII/Cu2O redox equilibrium at each pH. The effects of the pH-dependent complexes on the crystallographic orientation and electrical properties of Cu2O were rigorously investigated.Table I summarizes the relationship between the two complexes, deposition current density, and the properties of resulting Cu2O layers. In concert with the change of the complex, distinct differences in the properties were found bordering about pH 9.5. Since Cu2O shows p-type properties with intrinsic Cu+ defects, the conductivity of Cu2O depends on the amount of introduced Cu+ defects, the origin of p-type carriers. If the reduction of the complexes occur exactly according to the stoichiometry:2Cu(H–1L)L– (1) + H2O + 2e = Cu2O + 4L– 2Cu(H–1L)2 2– (2) + 3H2O + 2e = Cu2O + 4L– + 2OH– then, there should be no Cu+ defects. In practice, however, the defects often occur in Cu2O, because O2– ions can be incorporated into the lattice through an acid-base reaction like OH– = O2– + H+, independently of the reduction reactions. The amount of Cu+ defects is thus influenced by how readily the reduction of the complexes occur. The lower carrier density of Cu2O deposited at lower pH can be due to the ease in reduction of lower symmetric complex 1 dominant in the electrolytes, because complex with lower symmetry is generally more favorable to be reduced than that with higher one (2 in this case). The formation of Cu+ defects can also indebted to OH– activity near the cathode. At lower pH, the independent incorporation of O2– is restricted due to lower OH– activities, while high pH electrolytes with higher OH– activities provide an environment conducive to Cu+ defects. As a result, Cu2O layers with few Cu+ defects, low carrier density, and high resistivity is deposited from the electrolytes with complex 1. Owing to the low carrier density, the deposition becomes limited by carrier diffusion showing a low deposition current density.Although the deposited Cu2O crystals were randomly oriented at the early stage of electrodeposition irrespective of the pH, the deposits from lower and higher pH electrolytes became to have 〈100〉 and 〈111〉 orientations, respectively, as the electrodeposition proceed. Regarding the cubic Cu2O crystal, {100} planes have a higher surface energy than {111} planes. Therefore, under low current density (at lower pH), that is slow crystal growth with thermodynamic equilibrium control, Cu2O crystals with stable {111} facets are advantageous to appear. In contrast, at high current densities (at higher pH), the conditions favoring the appearance of {111} facets weaken and crystals with {100} facets appear. In such a growth mode, crystals whose preferential growth direction are not perpendicular to the planar substrate (cathode) were eliminated as the growth proceeds, because the directions interfere each other. As a result, the surface of thick Cu2O layers obtained from lower pH electrolytes is composed of square pyramidal grains with the vertex pointing perpendicular to the substrate; here, the faces of the pyramids correspond to four {111} facets. In contrast, the surface those obtained at higher pH is composed of triangular pyramidal grains with {100} facets.Consequently, it is considered that the two different complexes directly affect the difference in carrier density and conductivity of electrodeposited Cu2O, and the deposition current density changes depending on these electrical properties. Then, the current density determines the crystallographic orientation of resulting Cu2O.[1] T. Chen, et al., J. Electrochem. Soc., 166, D761 (2019); [2] T. Chen, et al., J. Electrochem. Soc., 165, D444 (2018). Figure 1

Effect of Electrolyte Anions on the Activity of Iridium Oxide Catalysts for Water Electrolysis

Developing environmentally friendly and renewable energy sources is essential due to the environmental and energy security issues caused by traditional combustion of fossil fuel-based energy sources. Therefore, as a clean and sustainable energy carrier, hydrogen has attracted great attention in recent years. In this regard, water electrolysis utilizing renewable energy sources to produce hydrogen is considered one of the most promising technologies. It is believed elucidation of the reaction mechanism of highly active iridium oxides is promising for the further development of cost-efficient PEM water electrolysis catalysts. The properties of the MEA could be affected by many parameters such as the catalysts, operating temperature, and pressure1,2. Another important factor is the cation impurities that can be found in the circulating water, which could severely degrade the MEA performance during the operation of a PEM water electrolyze. However, there are less reports on anion impurities such as SO4 2- and PO4 3-. Therefore, in this study, the relationship between electrolyte anions and OER activity was investigated for IrOx catalysts with different crystal structure. By using operando X-ray absorption spectroscopy (XAS), we investigated the electronic state of Ir and O under operation potential.IrOx with different degree of crystallinity (SA3.5 and SA58) were provided by Tanaka Kikinzoku Kogyo K.K., Chemical & Refining Company and named after their BET surface areas. These two samples were then tested for electrochemical properties in different concentrations of phosphoric acid and perchloric acid, respectively. The electrochemical measurements were performed using a standard three-electrode cell connected to an MPG-205-NUC system (Bio-Logic). The cyclic voltammograms (CV) were scanned from 0.1 V to 1.2 V vs. RHE at 50 mV s-1. The electrochemical activities of the catalysts were subsequently investigated using linear sweep voltammetry (LSV) in the range of 1.1 to 1.7 V vs RHE at 10 mV s−1. operando XAS were collected using a home-made flow-type cell, where Pt wire and RHE worked as counter and reference electrodes, respectively. The catalyst ink was coated onto an Nafion membrane to prepare both the X-ray window and working electrode. The electrolyte was circulated at the flow rate of 100 mL min-1.The catalytic performance of IrOx was investigated at different types and content of electrolyte under H3PO4 and HClO4. Figure 1 shows the CVs of SA3.5 and SA58 under different types and content of electrolyte. In the presence of phosphate anions, SA3.5 showed a tendency to decrease Ir redox between 0.6 and 1.1 V with increasing electrolyte concentration. On the other hand, there were no obvious changes in SA58. It was found that IrOx catalysts have an great effect of specific adsorption of anions and low symmetry of monoclinic phase catalysts (SA 3.5) are more susceptible to anion poisoning. Figure 2 shows the result of examining the poisoning mechanism using soft X-ray XAS. O K-edge results present the formation of µ2-O (O-O) bond at around 528.7 eV, which was previously observed by Nong, H. N. et. al. through operando O-K edge measurements during OER process3. The peak intensity at 528.7 eV of the amorphous samples was in the same order as the OER activities. According to potential dependence change of the pre-edge peak, under the presence of phosphate anions, the hole formation to Ir-O hybrid orbitals was suppressed in SA3.5. This result indicates that the anion adsorbs to the active site, poisoning the catalyst surface and inhibiting the reaction. Acknowledgements This work is based on results obtained from a project (JPNP14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan. References Zhang, Y.; Zhu, X.; Zhang, G.; Shi, P.; Wang, A.-L.; et al. J. Mater. Chem. A: 2021, 9, 5890-5914.Chen, Z.; Duan, X.; Wei, W.; Wang, S.; Ni, B.-J.; et al. Nano Energy: 2020, 78, 105270.Nong, H. N.; Falling, L. J.; Bergmann, A.; et al. Nature 2020, 587 (7834), 408-413. Figure 1

Investigating the Reaction Mechanism of Iridium Oxides for PEM Water Electrolysis by Operando Soft X-Ray Absorption Spectroscopy

With the increase in fossil energy consumption and the attendant pronounced climate changes, the call for sustainable energy forms has become urgent and has attracted more and more attention.1 Hydrogen (H2), generated by the electricity-derived water electrolysis, is now considered the promising energy carrier for conversion between electricity and chemical energy.2 The most developed water electrolysis technology up to date is the proton-exchange membrane (PEM) water electrolysis, where commercial Pt/C works as the cathodic catalyst for hydrogen evolution reaction (HER) and noble metal-based materials serve as the anodic catalyst for oxygen evolution reaction (OER).3 Considering the sluggish four-electron reaction kinetics of OER and the harsh acidic environment of PEM water electrolysis, the selectivity of high-efficient OER catalysts is narrowed down to Ir-based catalysts because of their superior activity, long-term stability and corrosion resistance against acidic environment.4 However, the scarcity of Ir on earth has impeded the wide application of PEM water electrolysis and has driven the research of cost-efficient OER catalysts. In this study, we thoroughly investigated several amorphous IrOx catalysts with different degree of crystallinity (SA103, SA58, SA14.6 and SA58) and revealed the relation between their structures and OER activities. Besides, BET surface areas, X-ray diffraction (XRD), Transmission electron microscopy (TEM), scanning TEM (STEM), PDF, and XAS were measured to thoroughly understand the catalytic properties.XRD patterns in Figure 1(a) showed that compared with the well-crystallized IrO2, SA58 sample showed slightly broad peak, while the diffraction peaks were much broad of other samples, indicating their amorphous structures. The amorphous structure of IrOx was characterized through atomic pair distribution function (PDF) analyses as shown in Figure 1(b). Different from the typical tetragonal symmetry of crystal IrO2, the combination of orthorhombic symmetry and monoclinic symmetry was found in the amorphous IrOx. Further, OER activities of all samples were investigated in 0.1 M HClO4 and the current density was calculated against the BET surface areas to examine the intrinsic catalytic activity (Figure 1(c)). The crystallized SA58 sample showed the lowest activity, while SA3.5 sample outperformed all other amorphous oxides. From PDF, it was found that the highest OER active SA3.5 sample exhibited the highest monoclinic phase ratio content. The catalytic structure properties were further evidenced by the XAS results. EXAFS results showed different electronic environment of monoclinic phase samples and further fitting results were in good agreement with the PDF analyses. Moreover, O K-edge results showed the formation of µ2-O (O-O) bond at around 528.7 eV, which was previously observed by Nong, H. N. et. al. through operando O-K edge measurements during OER process.5 It was concluded that that the low symmetry of monoclinic phase in amorphous samples resulted in the structure defection, and thus lead to large amount of active electrophilic OI - species, which boosting the OER activity. This finding provided fundamental understanding of the amorphous iridium oxides and could promisingly shed light on the future OER catalyst design. Acknowledgements This work is based on results obtained from a project (JPNP14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan. References Götz, M.; Lefebvre, J.; Mörs, F.; McDaniel Koch, A.; Graf, F.; Bajohr, S.; Reimert, R.; Kolb, T., Renewable Power-to-Gas: A technological and economic review. Renew. Energy 2016, 85, 1371-1390.Dincer, I.; Acar, C., Review and evaluation of hydrogen production methods for better sustainability. Int. J. Hydrogen Energy 2015, 40 (34), 11094-11111.Carmo, M.; Fritz, D. L.; Merge, J.; Stolten, D., A comprehensive review on PEM water electrolysis. Int. J. Hydrogen Energy 2013, 38 (12), 4901-4934.An, L.; Wei, C.; Lu, M.; Liu, H.; Chen, Y.; Scherer, G. G.; Fisher, A. C.; Xi, P.; Xu, Z. J.; Yan, C.-H., Recent Development of Oxygen Evolution Electrocatalysts in Acidic Environment. Adv. Mater. 2021, 33 (20), 2006328.Nong, H. N.; Falling, L. J.; Bergmann, A.; Klingenhof, M.; Tran, H. P.; Spöri, C.; Mom, R.; Timoshenko, J.; Zichittella, G.; Knop-Gericke, A.; Piccinin, S.; Pérez-Ramírez, J.; Cuenya, B. R.; Schlögl, R.; Strasser, P.; Teschner, D.; Jones, T. E., Key role of chemistry versus bias in electrocatalytic oxygen evolution. Nature 2020, 587 (7834), 408-413. Figure 1

Influence of Increasing Deposition Temperature during Atomic Layer Deposition on Electrical Properties and Reliability in Al2O3 - Doped ZrO2 Based Two-Dimensional and Three-Dimensional Metal-Insulator-Metal Decoupling Capacitors

The influence of deposition temperature (TD) on thin film layers of high-k dielectrics used as insulators in embedded Metal-Insulator-Metal (MIM) decoupling capacitors is critical to their future behavior in terms of electrical properties and reliability. These layers are deposited via atomic layer deposition (ALD), which is known for its high uniformity in any type of structural topology. High-k dielectrics, such as Zr, inside high aspect ratio three-dimensional (3-D) structures are a challenging task even in the case of ALD processing. Al2O3 doping is often used within the high-k layer stack during ALD to optimize electrical performance of MIM structures with respect to leakage currents and reliability. In this context, appropriate atomic layer deposition temperature (TD) of the Al2O3-doped ZrO2 high-dielectric stack must be established to enable optimum electrical properties. Electrical data of decoupling capacitors must fulfill the industrial requirements, which demand that, for example, the leakage current density (J) must not exceed a certain level (<1µA/cm²) and that long-term lifetimes under different operating temperatures of a minimum of 10 years at accumulated fail rate of 10 ppm must be achieved.In this work, we report on a study of the influence of ALD TD on Al2O3-doped ZrO2 thin films fabricated on 300mm wafers. We evaluate the impact of TD on high aspect ratio substrates based on electrical properties and reliability parameters. To achieve this, we use 3 different deposition temperatures (293°C, 313°C, and 333°C) and two physical topologies (planar and 3-D capacitors with cavities-trenches) without compromising the chemical stability of the ALD precursors. For metal precursors, TEMAZ (Tetrakis-ethylmethylamino-zirconium) and TMA (Tri-methyl-aluminum) are used for Zr and Al, respectively. Ozone is used as reactant agent and argon as carrier/purge gas. The ZrO2 cycle consists of pulsing with TEMAZ, purging with Ar gas, oxidizing with O3, and purging with Ar gas. In a similar way, the dopant (TMA) is added, followed by purging steps with Ar, O3 and Ar again. After a few ZrO2 cycles, an Al2O3 cycle is followed, so that nano-laminate films of Al2O3 are formed on top of ZrO2 films. By repeating the ZrO2 and the Al2O3 cycles several times, the desired film thickness is achieved. For the MIM stacks, TiN is used as an electrode material on both sides. There was no post deposition anneal to maintain the amorphous state of the insulator with low defect density and high structural uniformity.The planar capacitors show minimal changes in terms of capacitance density with increasing TD. On the other hand, the 3-D samples show a 17% increase in capacitance density with a TD increase of 20°C from 293°C to 313°C. This increase becomes much smaller (2.3%) for a further TD increase of 20°C at 333°C. However, with increasing TD, the E-field linearity of 3-D samples, expressed by the quadratic E-field capacitor coefficient α, increases by 2% and 17% for TD=313°C and TD=333°C, respectively. The significant improvement in field linearity indicates the highest TD provides the best and most stable capacitance behavior. The J(E)-curves of planar and 3-D devices exhibit different behavior with respect to current density and dielectric breakdown. Specifically, planar devices show greater variation in J(E)-curves over temperature, with decreasing breakdown field (EBD) as TD increases. On the other hand, 3-D samples show little variation in EBD with temperature. Furthermore, planar devices show lower symmetry in their J(E)-curves over the field polarity compared to 3-D capacitors, which could be attributed to differences in conduction mechanisms. Despite having a lower EBD, planar devices reveal improved lifetime and reliability with increasing TD, possibly due to reduced carbon impurities during the insulator deposition. For instance, increasing TD from 293°C to 313°C leads to a 47% improvement in extrapolated lifetime, while a further increase in TD, improves lifetime by an additional 14%. A 10-year lifetime goal can only be achieved at 1MV/cm with TD=333°C and for samples exposed to any temperature conditions (25-150°C). In contrast, 3-D capacitors exhibit a better degradation slope at lower deposition temperatures but require the highest TD to achieve an 18% improvement in lifetime. However, due to their lower EBD, they cannot reach the 10-year lifetime goal at 1MV/cm, except at low applied temperatures (25°C-50°C).In conclusion, the highest TD of 333°C without any chemical decomposition of the metal precursor (TEMAZ) is the optimal deposition temperature for both planar and 3-D Al2O3-doped ZrO2 based MIM decoupling capacitors, providing auspicious results in terms of all relevant parameters. Figure 1

BenPt (n = 6–8) cluster adsorb water molecule splitting to produce H2 based on density functional theory

The study of catalysts for hydrogen production from water splitting is of great significance for solving the global energy crisis. The lowest energy structures of BenPt (n = 6–8) clusters, the lowest energy structures of BenPt@H2O (n = 6–8) complexes and water molecule splitting to produce H2 of BenPt + H2O (n = 6–8) are investigated based on the density functional theory. According to the computed results, BenPt (n = 6–8) clusters have low point group symmetry in their lowest energy structures. The density of states (DOS) map shows strong interactions between water molecules and clusters in BenPt@H2O (n = 6–8) complexes. The predicted mechanism of the BenPt + H2O (n = 6–8) water molecule splitting to produce H2 shows the maximum Be7Pt + H2O reaction energy (-3.565 eV). Interaction region indication (IRI) plots of the reaction product BenPtO@H2 (n = 6–8) show easy desorption of the H2 molecule from Be7PtO@H2.

Lower extremity joint contact force symmetry during walking and running, 2-7 years post-ACL reconstruction.

Premature osteoarthritis after anterior cruciate ligament reconstruction (ACLR) is common among athletes. Reduced knee contact forces after ACLR likely contribute to the multifactorial etiology of the disease. Whether this reduction is accompanied by compensatory increases in joint contact forces (JCF) at adjacent or contralateral joints is unclear. It is also unclear if compensatory effects depend on the task demands. Thus, we compared hip, knee, and ankle JCF symmetry between individuals with reconstruction and a matched control group during walking and running. Thirty participants (19 females), 2-7 years post-unilateral ACLR (mean = 47.8 months), and 30 controls matched on sex, mass, and activity level were recruited. Limb symmetry indices of peak contact forces and force impulses were calculated for each joint during walking and running, and analyzed using two-factor (group, activity) analysis of variances. Lower ACLR group peak knee JCF (p = 0.009) and knee JCF impulse (p = 0.034) during walking and running were observed. An interaction of group and activity was observed for peak hip JCF, with ACLR participants demonstrating greater involved limb peak hip JCF during running (p = 0.012). Ankle JCF and ground reaction force symmetry indices were not different between groups or across tasks. Decreased knee and increased ipsilateral peak hip JCF during running suggests that proximal adaptations exist at 2-7 years after ACLR, particularly during activities with increased task demand. Clinical significance: Knee and hip JCF asymmetry at 2-7 years after ACLR may underscore a need for clinical strategies and follow-up assessments to identify and target such outcomes.

Highly Bright and Stable Lead-Free Double Perovskite White Light-Emitting Diodes.

Lead-free double perovskites (DPs) are emerging highly stable emitters with efficient broadband self-trapped exciton (STE) photoluminescence (PL), but their low electroluminescent (EL) efficiency is a critical shortcoming. This work promotes the external quantum efficiency (EQE) and luminance of DP-based white light-emitting diode (wLED) with a normal device structure to 0.76% and 2793cd m-2 via two modifications: This work prevents the formation of adverse metallic silver, spatially confined STE, and lowers local site symmetry in Cs2 Na0.4 Ag0.6 In0.97 Bi0.03 Cl6 DP by terbium doping; and this work develops a guest-host strategy to improve film morphology, reduce defect density, and increase carrier mobility. These alterations cause substantial increase in STE radiative recombination and charge injection efficiency of perovskite layer. Finally, pure white EL with ideal color coordinates of (0.328, 0.329) and a record-breaking optoelectronic performance is achieved by introducing additional green carbon dots in LED to fill the deficient green component.

Transition between distinct hybrid skyrmion textures through their hexagonal-to-square crystal transformation in a polar magnet

Magnetic skyrmions, topological vortex-like spin textures, garner significant interest due to their unique properties and potential applications in nanotechnology. While they typically form a hexagonal crystal with distinct internal magnetisation textures known as Bloch- or Néel-type, recent theories suggest the possibility for direct transitions between skyrmion crystals of different lattice structures and internal textures. To date however, experimental evidence for these potentially useful phenomena have remained scarce. Here, we discover the polar tetragonal magnet EuNiGe3 to host two hybrid skyrmion phases, each with distinct internal textures characterised by anisotropic combinations of Bloch- and Néel-type windings. Variation of the magnetic field drives a direct transition between the two phases, with the modification of the hybrid texture concomitant with a hexagonal-to-square skyrmion crystal transformation. We explain these observations with a theory that includes the key ingredients of momentum-resolved Ruderman–Kittel–Kasuya–Yosida and Dzyaloshinskii-Moriya interactions that compete at the observed low symmetry magnetic skyrmion crystal wavevectors. Our findings underscore the potential of polar magnets with rich interaction schemes as promising for discovering new topological magnetic phases.

Solid Oxide Membrane-assisted Controllable Electrolytic Fabrication of Ti5Si3/TiC Composites in Molten Salt

Background: The titanium silicide Ti5Si3 possesses many desirable properties, such as a high melting point, excellent high-temperature oxidation resistance, low density, and relatively high hardness, and it is considered a promising structural intermetallic compound. However, like most ceramic materials, originating from low symmetry (D88) in its crystal structure, Ti5Si3 has poor fracture toughness and limited flexibility at room temperature, and at high temperatures, its creep resistance also drops sharply, which hinders its application. To overcome these shortcomings, it is suggested that TiC is a practical addition to Ti5Si3 to overcome the brittleness. Compared with monolithic Ti5Si3, Ti5Si3/TiC composites have a higher fracture toughness. Ti5Si3/TiC composites can be prepared by many ways, which commonly require high energy cost, complex processes and provide low efficiency. Therefore, the search for environmentally friendly strategies for the production of Ti5Si3/TiC is still ongoing. Objective: This article proves that we can successfully prepare Ti5Si3/TiC composites from CaTiO3/SiO2/C precursor by using SOM technology and explores the reaction mechanism of electrochemical process. Methods: In the process of electroreduction of CaTiO3/SiO2/C particles into Ti5Si3/TiC composites, we mainly used SOM technology at 1273 K and 4.0 V in molten CaCl2 and under an argon atmosphere. Results: The results show that the Ti5Si3/TiC composites can also be successfully electrosynthesized from CaTiO3/SiO2/C precursors by using SOM-based anode systems at 1273 K and 4.0 V in molten CaCl2. Conclusion: This work demonstrates that Ti5Si3/TiC composites have been successfully electrosynthesized from CaTiO3/SiO2/C precursors using SOM-based anode systems at 1273 K and 4.0 V in molten CaCl2. The Ti5Si3/TiC has a smooth surface and micro/nano-porous structure. The formation routes for Ti5Si3 and TiC are independent. In summary, the SOM-assisted controllable electroreduction process has the potential to provide a novel one-step route from CaTiO3/ SiO2/C precursors to Ti5Si3/TiC composites in molten salts.

Ordinary light induced polarization zones in Tutton salt crystal

Ordinary light wave passing through a low symmetry crystal along an off optic -axis direction gets split into ordinary and extra-ordinary waves. If the beam size is large, the two polarized waves could overlap covering a large volume within the medium. It is realized that overlapping ordinary and extra-ordinary waves, result in creation of alternate polarization regions with different fluctuating crystalline fields inside a low - symmetry hydrated crystal. If suitable ions are doped in an experimental crystal, their optical absorption spectra could reflect the effect of alternate polarization fields and creation of ordinary light induced periodic polarization (OLIPP) effect inside a low symmetry hydrated crystal.

Dimorphism of [Bi2O2(OH)](NO3) - the ordered Pna21 structure at 100 K.

The re-investigation of [Bi2O2(OH)](NO3), dioxidodibismuth(III) hydroxide nitrate, on the basis of single-crystal X-ray diffraction data revealed an apparent structural phase transition of a crystal structure determined previously (space group Cmc21 at 173 K) to a crystal structure with lower symmetry (space group Pna21 at 100 K). The Cmc21 → Pna21 group-subgroup relationship between the two crystal structures is klassengleiche with index 2. In contrast to the crystal structure in Cmc21 with orientational disorder of the nitrate anion, disorder does not occur in the Pna21 structure. Apart from the disorder of the nitrate anion, the general structural set-up in the two crystal structures is very similar: [Bi2O2]2+ layers extend parallel to (001) and alternate with layers of (OH)- anions above and (NO3)- anions below the cationic layer. Whereas the (OH)- anion shows strong bonds to the BiIII cations, the (NO3)- anion weakly binds to the BiIII cations of the cationic layer. A rather weak O-H⋯O hydrogen-bonding inter-action between the (OH)- anion and the (NO3)- anion links adjacent sheets along [001].

Raman Investigation, Second Harmonic Generation, and Ultrasensitive Photoresponse of Low Symmetry Transition Metal Halide PdBr2

Raman Investigation, Second Harmonic Generation, and Ultrasensitive Photoresponse of Low Symmetry Transition Metal Halide PdBr₂

The Crystal Chemistry of Voltaite-Group Minerals from Post-Volcanic and Anthropogenic Occurrences

Five samples of voltaite-group minerals from post-volcanic occurrences (geothermal fields and solfatara at pyroclastic flow) and from pseudofumaroles born by coal fires are characterized by single-crystal X-ray diffraction, scanning electron microscopy and electron microprobe analysis. The studied minerals include ammoniomagnesiovoltaite, ammoniovoltaite, voltaite and magnesiovoltaite. The quadrilateral of chemical compositions is determined by monovalent cations such as (NH4)+ and K+ and divalent cations such as Fe2+ and Mg2+. Minor Al can occur in the Fe3+ site. Minor amounts of P, V can occur in the S site. Ammonium members are described from geothermal fields, expanding the mineral potential of this type of geological environment. All minerals are cubic, space group Fd-3c, a = 27.18–27.29 Å, V = 20079–20331 Å3, Z = 16. No clear evidence of symmetry lowering (suggested for synthetic voltaites) is observed despite the chemical variation in the studied samples. Ammonium species tend to have a larger a lattice parameter than potassium ones due to longer &lt;A–O&gt; distances (A = N or K). The systematically shorter &lt;Me2+–ϕ&gt;obs (Me2+ = Fe, Mg; ϕ = O, H2O) in comparison to &lt;Me2+–ϕ&gt;calc bond lengths can be explained as a consequence of mean bond length variation due to significant bond length distortion in Me2+ϕ6 octahedra Me2–O2—2.039–2.055 Å; Me2–O4—2.085–2.115 Å; and Me2–Ow5—2.046–2.061 Å, with bond length distortion estimated as from 0.008 to 0.014 for different samples.

Th4+ Co‐doped YF3 : Yb3+, Er3+ Nanostructures for Enhanced Visible and NIR‐II Emissions and Potential Application as Cryogenic Thermometer

AbstractRemarkable enhancement in green and red upconversion (UC) emissions by 124 and 88 %, respectively was achieved whereas down‐conversion (DC) luminescence in NIR‐II region (~1540 nm) was improved by 20 % in Th4+ co‐doped YF3 : Yb3+,Er3+ nanocrystalline particles. The same is ascribed to lowering of symmetry via formation of asymmetric Er−F bonds and less symmetric Y3+ sites due to distortions on Th4+ co‐doping. Benefiting from the distinct temperature response of stark sublevels of the 4S3/2 and 4F9/2 states, we have proposed a strategy for luminescence intensity ratios (LIR) based thermometry involving thermally coupled (TCL) stark sub‐levels. This can be promising in more accurate temperature read‐out at cryogenic temperatures (~ −193 °C). Using the same, high Sa and Sr values of 0.0139 K−1 (80 K) and 0.682 % K−1(80 K) were obtained for 4S3/2 (1)/4S3/2 (2)→4I15/2 transitions. Higher Sa and Sr values of 0.226 K−1 (80 K) and 2.627 %K−1(80 K) were obtained for 4F9/2 (1)/4F9/2 (2)→4I15/2 transitions. The high sensitivity values were obtained than that reported for the YF3 host. We believe this work with improved UC luminescence on Th4+ addition will be boon to cryogenic temperature‐sensing.

The efficacy of Bi0.46Y0.04K0.5ZrO3 doped three-step sintering to accomplish high piezoelectric and ferroelectric properties in new lead-free NaNbO3-based materials

The novel (1-x) NaNbO3-xBi0.46Y0·04K0·5ZrO3(x = 0.06, 0.09, 0.12 & 0.15), a polycrystalline lead-free ceramic composite made by the traditional solid-state technique, has been extensively studied for its multi-application in the three-step sintering process. The Rietveld refinement of the diffraction pattern shows a perovskite structure with a Pmc21 space group between 0.06 and 0.15. Scherrer's formula and Williamson-Hall plots are used to calculate crystallite size and strain. The Raman spectra have absorbed many vibrational spectral lines and moved to a lower frequency between 100 and 800 cm−1. FE-SEM and TEM images indicate well-defined and diverse grout morphology. The diffused absorbance spectra determine the band structure values of the prepared samples, which are found to be 3.16 eV–3.36 eV in the UV–Vis spectrum. Photoluminescence spectra exhibit the emission bands in the green (522 nm), yellow (575 nm), and red (693 nm) wavelength ranges. Dielectric data have lower symmetry at temperatures ranging from 103 to 106 Hz. Increasing the doping concentration of the material not only strengthens the ferroelectric and piezoelectric coefficient properties, but also enhances the voltage constant g33(49–88Vm/N) and the transduction coefficient d33× g33(22135 ×10−15Jm3). These improvements make the material suitable for applications requiring efficient energy conversion and sensing capabilities.

Organic hybrid tetranuclear clusteroluminogens: Blue-light-excitable LED with ultrahigh luminous efficacy

The development of highly emissive luminescent materials is vital for future light-emitting diodes, display, and scintillation applications. A series of novel organic hybrid metal halide clusters are presented here, that is, non-emission (C4H12N2)3(NH4)4Cd4Cl18 (namely, 1), pink-emission (C4H12N2)3(NH4)4Mn4Cl18 (namely, 2) and 1–2 alloy (namely, Mn-1). The crystal structure of alloy compound provides a clear insight into the Mn(II) effect. Mn(II) alloying in the host lattice successfully induces large octahedral distortion, hybrid of d/p orbitals and lower local symmetry resulting in a breaking d-d forbidden transition. The intense blue light absorption and high PLQY (92.6 %) inspire us to assemble Mn-1 as a blue-light-excited white light-emitting diode (WLED). The WLED has a minimized trade-off among luminous efficacy (182 lm/W), color-rendering index (82) and CCT (4536 K), which is achieved by the trichromatic combination (blue light chip, green (Ba, Sr)2SiO4:Eu2+, red Mn-1) and the red emission edge below 700 nm. The luminous efficacy of 182 lm/W is the highest among the previous WLEDs based on the lead-free metal halides, comparable to the market standard (185 lm/W) in 2020 set by The United States Department of Energy. In addition, the water-soluble Mn-1 further gives potential applications in X-ray scintillators, luminescent ceramics, flexible films and luminescent imaging agents. The discovery of tetranuclear metal halide clusters establishes a new strategy for constructing promising emissive materials.

Emergent symmetry in a low-dimensional superconductor on the edge of Mottness.

Upon cooling, condensed-matter systems typically transition into states of lower symmetry. The converse-i.e., the emergence of higher symmetry at lower temperatures-is extremely rare. In this work, we show how an unusually isotropic magnetoresistance in the highly anisotropic, one-dimensional conductor Li0.9Mo6O17 and its temperature dependence can be interpreted as a renormalization group (RG) flow toward a so-called separatrix. This approach is equivalent to an emergent symmetry in the system. The existence of two distinct ground states, Mott insulator and superconductor, can then be traced back to two opposing RG trajectories. By establishing a direct link between quantum field theory and an experimentally measurable quantity, we uncover a path through which emergent symmetry might be identified in other candidate materials.

Chemical Site-Differentiation of Calix[4]arenes through Enforced Conformations by Confinement in a Cage.

Desymmetrization of a symmetric skeleton enables late-stage functionalization of molecules. However, reagent-controlled desymmetrization by site-selective reactions of symmetric molecules remains a difficult synthetic strategy. Here, we found that complete confinement of a symmetric molecule within a coordination cage can desymmetrize the guest conformation, making it possible to site-selectively activate or protect the otherwise equivalent reaction sites of calix[4]arene derivatives. Multistep, one-cage reactions also demonstrated the transformation of an AAAA-type calix[4]arene into a lower symmetry ABAC-type one.

Polarization-tuneable excitonic spectral features in the optoelectronic response of atomically thin ReS2

The low crystal symmetry of rhenium disulphide (ReS2) leads to the emergence of dichroic optical and optoelectronic response, absent in other layered transition metal dichalcogenides, which could be exploited for device applications requiring polarization resolution. To date, spectroscopy studies on the optical response of ReS2 have relied almost exclusively in characterization techniques involving optical detection, such as photoluminescence, absorbance, or reflectance spectroscopy. However, to realize the full potential of this material, it is necessary to develop knowledge on its optoelectronic response with spectral resolution. In this work, we study the polarization-dependent photocurrent spectra of few-layer ReS2 photodetectors, both in room conditions and at cryogenic temperature. Our spectral measurements reveal two main exciton lines at energies matching those reported for optical spectroscopy measurements, as well as their excited states. Moreover, we also observe an additional exciton-like spectral feature with a photoresponse intensity comparable to the two main exciton lines. We attribute this feature, not observed in earlier photoluminescence measurements, to a non-radiative exciton transition. The intensities of the three main exciton features, as well as their excited states, modulate with linear polarization of light, each one acquiring maximal strength at a different polarization angle. We have performed first-principles exciton calculations employing the Bethe-Salpeter formalism, which corroborate our experimental findings. Our results bring new perspectives for the development of ReS2-based nanodevices.