Amorphous Research Articles

Interface and Electronic Structure Regulation of RuO2 through Ru/RuO2 Heterointerface Construction and Zn Atom‐Doping for High‐Performance Overall Water Splitting in Both Alkaline and Acidic Media

AbstractRational design and fabrication of efficient catalysts for overall water splitting in an integrated electrolyzer are essential for energy storage and conversion. Herein, an ultra‐small substitutional Zn‐doped Ru/RuO2 heterostructure (5.6 nm) is synthesized through a facile pyrolyzing strategy as an efficient bi‐functional electrocatalyst for water splitting in both acidic and alkaline media. Experiments demonstrate that introducing appropriate alien atoms into RuO2 with an amorphous state can effectively optimize the electron structure and expose abundant defects, and thus increasing the number of active sites and improving the intrinsic activity of RuO2 for the oxygen evolution reaction (OER). In addition, the high hydrogen adsorption capability of metallic Ru makes Ru‐RuO2 heterointerface suitable for water splitting. Notably, the Ru/ZnRuO2 displays low overpotentials at 10 mA cm−2 with only 184 mV for OER in 0.5 m H2SO4 and 35 mV for HER in 1.0 m KOH. Besides, the as‐synthesized Ru/ZnRuO2 displays cell voltages of 1.540 and 1.567 V (at 10 mA cm−2) for water splitting with remarkable durability for more than 220 and 100 h, respectively, in acidic and alkaline media. This work provides a facile strategy for designing pH‐universal electrocatalysts toward overall water splitting.

Nonlinear rheological behavior of glass-forming colloidal suspensions under oscillatory shear: Experiment and relation to mode coupling theory predictions

Glass-forming colloids consisting of soft core-shell particles were investigated experimentally under medium and large amplitude oscillatory shear (MAOS and LAOS) using Fourier transform rheology to decompose the stress signal into a series of higher harmonics. The anharmonicity of the stress response under MAOS and LAOS is quantified by the intensity of the third harmonic normalized to the fundamental (I3/1=I3/I1) and within the intrinsic nonlinearity framework of the Q-parameter (Q0=limγ0→0⁡(I3/1/γ02)). Furthermore, the results of the strain amplitude dependence were compared to the literature showing the mechanical anharmonic behavior of the core-shell system being close to the behavior of ultrasoft systems. In the glassy state, I3/1 shows an unusual scaling of I3/1∝γ04 at low frequencies, similar to amorphous polymeric materials when they undergo plastic deformation. For investigating the frequency dependence of the anharmonicity in a specially designed binary mixture to test for critical behavior close to the glass transition as predicted by mode coupling theory (MCT) and extend the measurements to the glassy state, we used the frequency sweep MAOS methodology. Using this time-efficient method, the frequency dependence of a wide range of volume fractions and frequencies was investigated, finding the anharmonicity parameter Q0 to be maximal in the region of the α-relaxation for colloidal liquids. The colloidal glasses do not exhibit a maximum in Q0, but an increase in Q0 with decreasing frequency over the investigated region, as the α-relaxation slows down significantly in colloidal glasses. Predictions from MCT from the literature show agreement with the experimentally determined scaling laws.

Overlapping plastic events as a mechanism for irreversible dynamics in amorphous solids under oscillatory shear

The origin of the transition from asymptotically reversible to asymptotically irreversible response in amorphous solids subject to oscillatory shear is still unknown. It is known that the plastic events that result from shearing always involve localized particle rearrangements, but it is unclear why some are reversible while others are not. Here, we show, using simulations and models, that overlaps between particle rearrangements caused by straining the solid in alternating directions can cause the response to become irreversible when they occur frequently. As the forcing amplitude increases, plastic events become more frequent, the number of such overlaps increases, and the probability of the system returning to previous states diminishes. Published by the American Physical Society 2024

Vibrational lifetimes and viscoelastic properties of ultrastable glasses

Amorphous solids are viscoelastic. They dissipate energy when deformed at finite rate and finite temperature. We here use analytic theory and molecular simulations to demonstrate that linear viscoelastic dissipation can be directly related to the static and dynamic properties of the fundamental vibrational excitations of an amorphous system. We study ultrastable glasses that do not age, i.e., that remain in stable minima of the potential energy surface at finite temperature. Our simulations show four types of vibrational modes, which differ in spatial localization, similarity to plane waves and vibrational lifetimes. At frequencies below the Boson peak, the viscoelastic response can be split into contributions from plane-wave and quasilocalized modes. We derive a parameter-free expression for the viscoelastic storage and loss moduli for both of these modes. Our results show that the dynamics of microscopic dissipation, in particular the lifetimes of the modes, determine the viscoelastic response only at high frequency. Quasilocalized modes dominate the linear viscoelastic response at intermediate frequencies below the Boson peak. Published by the American Physical Society 2024

Tailoring of Novel Amorphous RuS2/ZrS2/MWCNT Nanocomposite Platform as a Dual Sensor for the Detection for Water Pollutant Indigo Carmine

Abstract The present study focuses on synthesizing amorphous nanocomposites of RuS2/ZrS2/MWCNT and exploring their potential for modifying electrodes and detecting indigo carmine dyestuff. Amorphous materials have recently garnered significant attention due to their ability to control material properties through their distinct nature. Transition metal dichalcogenides, or TMDs, are being extensively used in various applications such as catalysis, dye degradation, and so on. Amorphous transition metal sulphides, due to their heightened active sites, exhibit higher performance. This study presents the first-ever successful production of two amorphous metal sulphides that are doped with multi-walled carbon nanotubes. The resulting novel material was used to detect indigo carmine with high efficiency. The detection range was wide, spanning from 0.1 µM to 300.0 µM, and the limit of detection was 0.08 μM. These results demonstrate that the material outperforms most previously reported studies in this field. The technique employed was both simple and innovative, and it was used on both Glassy Carbon Electrode (GCE) and Screen-Printed Electrode (SPE) systems. It was effectively evaluated for the detection of the dye in water samples as well as food and pharmaceutical sample

Intermittent cluster dynamics and temporal fractional diffusion in a bulk metallic glass

Glassy solids evolve towards lower-energy structural states by physical aging. This can be characterized by structural relaxation times, the assessment of which is essential for understanding the glass’ time-dependent property changes. Conducted over short times, a continuous increase of relaxation times with time is seen, suggesting a time-dependent dissipative transport mechanism. By focusing on micro-structural rearrangements at the atomic-scale, we demonstrate the emergence of sub-diffusive anomalous transport and therefore temporal fractional diffusion in a metallic glass, which we track via coherent x-ray scattering conducted over more than 300,000 s. At the longest probed decorrelation times, a transition from classical stretched exponential to a power-law behavior occurs, which in concert with atomistic simulations reveals collective and intermittent atomic motion. Our observations give a physical basis for classical stretched exponential relaxation behavior, uncover a new power-law governed collective transport regime for metallic glasses at long and practically relevant time-scales, and demonstrate a rich and highly non-monotonous aging response in a glassy solid, thereby challenging the common framework of homogeneous aging and atomic scale diffusion.

Effect of TiC grain size on corrosion behaviors of Ti-Si-C nanocomposite coatings fabricated by heterogeneous targets high-power impulse magnetron sputtering

Ti-Si-C coatings with different carbon contents were prepared on SS316L substrates by heterogeneous targets high-power impulse magnetron sputtering with a repetitive C and TiSi deposition. Various tests were employed to analyze the microstructure, anti-corrosion properties in a simulated proton exchange membrane fuel cells (PEMFC) environment and interfacial conductivity of the coatings. Results indicated that the Ti-Si-C coating possessed a typical nanocomposite structure of TiC nanocrystals embedded in amorphous carbon matrix. With the increase of the carbon content, the grain size of TiC nanocrystals was reduced gradually. Electrochemical measurements revealed that a proper decrease of TiC grain size led to an enhanced corrosion resistance of the as-deposited coating. The smallest interfacial contact resistance and corrosion rate of the Ti-Si-C coating in the simulated PEMFC solution reached 5.07 mΩ cm2 and 5.93E-07 A/cm2, respectively. This improvement could be attributed to the formation of a dense and continuous passivation layer composed of Ti2O3 and SiO2 on the top surface of the coating.

Supersolubilization and Amorphization of a Weakly Acidic Drug, Flurbiprofen, by applying Acid-Base supersolubilization (ABS) principle

Improvement in drug solubility is a major challenge for developing pharmaceutical products. It was demonstrated earlier that aqueous solubilities of weakly basic drugs could be increased greatly by interaction with weak acids that would not form salts with the drugs, and the highly concentrated solutions thus produced converted to amorphous solids upon drying. The technique was called acid-base supersolubilization (ABS). The current investigation explored whether the ABS principle could also be applied to weakly acidic drugs. By taking flurbiprofen (pKa 4.09; free acid solubility 0.011 mg/mL) as the model weakly acidic drug and tromethamine, lysine, meglumine, and NaOH as bases, it was studied which of the bases would result in ABS. While in the presence of NaOH and tromethamine, flurbiprofen converted to salts having aqueous solubility of 11–19 mg/mL, the solubility increased to > 399 mg/mL with lysine and > 358 mg/mL with meglumine, producing supersolubilization. However, crystallization of lysine salt was observed with time, followed by some decrease in solubility after reaching maximum solubility with lysine. In contrast, the supersolubilization was maintained with meglumine, and no crystallization of meglumine salt was observed. Upon drying, flurbiprofen-meglumine solutions produced amorphous materials that dissolved rapidly and produced high drug concentrations in aqueous media. Thus, the ABS principle also applies to acidic drugs depending on the weak base used.

Novel self-assembled micelles of dual-modified dextrin with pH responsiveness via grafted octenyl succinic anhydride and cysteamine for curcumin delivery

In this study, a novel dextrin-based micelle (OSAD-SH), dual-modified with octenyl succinic anhydride (OSA) and cysteamine, has been developed to address the acid instability issues of micelles modified only by OSA and designed for curcumin delivery. The chemical structure of OSAD-SH was characterized and the physical properties of the micelles were evaluated. Results displayed that OSAD-SH micelles exhibit strong self-assembly properties, appearing as spheres with diameters ranging from 92.41 to 194.20 nm. Blank micelles with good dilution resistance, acid, thermal, and ionic strength stability. The curcumin encapsulated by the micelles is in an amorphous state. In vitro release experiments demonstrated that curcumin released from OSAD-SH micelles exhibits intestinal targeting. The Ritger-Peppas model effectively predicted the release behavior of curcumin, indicating that the release mechanism follows super case-II transport. The OSAD-SH micelle could be a promising nanocarrier for improving the physicochemical properties of curcumin in food fields.

Influences of polymorphism of packed particles on bulk characterizations in fluidization realm

The characterization of a particle ensemble (rather than a single particle) is of paramount significance to various particle technologies and has long been a fundamental subject in the fluidization realm. However, many of such bulk characterizations as loosely-packed density (ρbl), minimum fluidization velocity (Umf), sphericity (φ), discharge rate through orifice (q), angle of repose (β), and segregation index (S), were found to be poorly reproducible, making the reported results seldom comparable. Since these bulk characterizations started from the packed state of particles, such poor reproducibility was ascribed to the polymorphism of packed particles in this work. We observed that in the fluidized bed, the settled/packed state of particles varied monotonously with the settling rate (α) from complete fluidization to zero. This phenomenon confirmed the polymorphic characteristic of packed particles and further enabled us to systematically disclose/clarify its influences on the aforementioned bulk characterizations. Such influences could be comprehensively and intuitively reflected by the impacts induced by α. With the decrease of α, ρbl, φ, and q first increased, then decreased, and finally levelled off while Umf and β showed an opposite trend. On the other hand, S first increased and then remained invariant. As per these findings and definitions of these bulk characterizations, benchmarks were indicated to unify the selection of settled state among future scholars and further make their outcomes become fairly comparable. Additionally, most packed states of the particle ensemble were proved to be metastable with their formation and behavior being identical to those of the amorphous state.

Cu-doped 70S bioactive glass fibrous membranes produced using solution blow spinning (SBS)

3D fibrous membranes of undoped and Cu-doped 70S glass were developed, by solution blow spinning. The concentration of copper ions ranged from 1 to 4 % in mol. As-spun fibers were calcined/stabilized at 700 °C. The produced membranes' morphological and biological properties and the release of Ca and Cu ions were evaluated. Amorphous materials were obtained in pure and doped with 1 % Cu2+ 70S glass, while metallic copper was observed in 4 % Cu2+ doped glass. All samples have fibers with average diameter at the submicron scale, ranging from 700 to 850 nm. The amount of Cu ions influenced the degradation of the samples and the release of Cu and Ca ions in the Tris solution, the greater the amount of copper the more these ions were degraded and released in the solution. In vitro biological results, showed that adding copper favored the biomineralization process. No toxicity was observed in the MMT test for all samples. Alamar Blue method showed cell viability for fibroblasts greater than 90 % for all samples and for osteoblasts greater than 70 % for the BG-70S.2Cu sample. The developed fibrous membranes presented antimicrobial characteristics against Staphylococcus aureus and Candida albicans.

An Advanced Twin-Screw Granulation Technology: The use of Non-Volatile Solvents with High Solubilizing Capacity

PurposeTwin-screw wet granulation (TSWG) is a manufacturing process that offers several advantages for the processing of water-insoluble active pharmaceutical ingredients (APIs) and has been used for increasing the solubility and dissolution rates. Here we introduce a novel TSWG approach with reduced downstream processing steps by using non-volatile solvents as granulating binders.MethodsHerein, TSWG was carried out using Transcutol a non-volatile protic solvent as a granulating binder and dissolution enhancer of ibuprofen (IBU) blends with cellulose polymer grades (Pharmacoat® 603, Affinisol™, and AQOAT®).ResultsThe physicochemical characterisation of the produced granules showed excellent powder flow and the complete transformation of IBU into the amorphous state. Dissolution studies presented immediate release rates for all IBU formulations due to the high drug-polymer miscibility and the Transcutol solubilising capacity.ConclusionsOverall, the study demonstrated an innovative approach for the development of extruded granules by processing water-insoluble APIs with non-volatile solvents for enhanced dissolution rates at high drug loadings.Graphical

Effect of Ultraviolet Radiation on Properties of Ge2Sb2Te5 Phase Change Films.

With the expanding utilization of space technology, the stability of electronic components' performance in radiation environments has garnered significant attention. In this study, we prepared Ge2Sb2Te5 phase change films and memory units on silicon substrates to explore the influence of ultraviolet (UV) radiation on their characteristics. The experimental findings revealed that UV irradiation at a power density of 450 mW/cm2 decreased the amorphous resistance and thermal stability of Ge2Sb2Te5 films, impeding their multistage storage performance. Nevertheless, the amorphous state could still undergo effective transformation into a crystalline state. Furthermore, UV irradiation triggered the photoelectric effect, narrowing the band gap and causing a redshift of the Raman peak in amorphous films. Remarkably, the surface properties of Ge2Sb2Te5 films remained unchanged under irradiation. The phase change memory device based on Ge2Sb2Te5 film retained its SET-RESET conversion capability at a pulse width of 100 ns post-UV irradiation, demonstrating resilience against UV radiation. This study offers the practical insights for the application of phase change memory in space radiation environments.

Low-Frequency Raman Spectroscopy on Amorphous Poly(Ether Ether Ketone) (PEEK)

Low-frequency peaks in the Raman spectra of amorphous poly(ether ether ketone) (PEEK) were investigated. An amorphous sample with zero crystallinity, as confirmed by wide-angle X-ray diffraction, was used in this study. In a previous study, two peaks were observed in the low-frequency Raman spectra of the crystallized samples. Among these, the peaks at 135 cm−1 disappeared for the amorphous sample. Meanwhile, for the first time, the peak at 50 cm−1 was observed in the crystallized sample. Similar to the peak at 135 cm−1, the peak at 50 cm−1 disappeared in the amorphous state, and its intensity increased with increasing crystallinity. The origins of the two peaks were associated with the Ph-CO-Ph-type intermolecular vibrational modes in the simulation. This suggests that the Ph-CO-Ph vibrational mode observed in the low-frequency region of PEEK was strongly influenced by the intermolecular order.

Ultrasensitive Self-Powered Flexible Crystalline β-Ga2O3-Based Photodetector Obtained through Lattice Symmetry and Band Alignment Engineering.

Due to its portable and self-powered characteristics, the construction of Ga2O3-based semiconductor flexible devices that can improve the adaptability in various complex environments have drawn great attention in recent decades. However, conventional Ga2O3-based flexible heterojunctions are based on either amorphous or poor crystalline Ga2O3 materials, which severely limit the performance of the corresponding devices. Here, through lattice-symmetry and energy-band alignment engineering, we construct a high-quality crystalline flexible NiO/β-Ga2O3 p-n self-powered photodetector. Owing to its suitable energy-band alignment structure, the device shows a high photo-to-dark current ratio (1.71 × 105) and a large detection sensitivity (6.36 × 1014 Jones) under zero bias, which is superior than most Ga2O3 self-powered photodetectors even for those based on rigid substrates. Moreover, the fabricated photodetectors further show excellent mechanical stability and robustness in bending conditions, demonstrating their potential practical applications in flexible optoelectronic devices. These findings provide insights into the manipulation of crystal lattice and energy band engineering in flexible self-powered photodetectors and also offer guideline for designing other Ga2O3-based flexible electronic devices.

Magnetocaloric Properties of Melt-Extracted Medium Entropy Gd33Co33Al34 Microfibers

In this paper, a new medium entropy alloy with nominal composition of Gd33Co33Al34 was designed and fabricated into microfibers by a melt-extraction method. The microstructure, thermophysical parameters, and magnetocaloric properties of the obtained fibers were systematically analyzed. The results showed that the as-cast fibers show an amorphous matrix with embedded in situ nano crystals. The fibers show a good magnetocaloric effect with the maximum magnetic entropy change of ~6 J/kg·K for a field change of 5 T. Notably, the fibers show excellent cooling efficiencies with an RCP and RC of ~611.72 and ~487.38 J/kg, respectively. Though the as-cast fibers possess an amorphous/nanocrystal bi-phase structure, they still exhibit a second-order transition near a Curie temperature of ~96 K. Our findings provide a promising pathway towards developing new magnetocaloric materials with good magnetocaloric performances.

Paracetamol Inclusion in Mechanically Interlocked Nanocages.

The solid-state synthesis and fast crystallization under kinetic control of poly-[n]-catenanes self-assembled of mechanically interlocked metal organic cages (MOCs) is virtually unexplored. This is in part, due to the lack of suitable crystals for single crystal X-ray diffraction (SC-XRD) analysis which limits their progress as advanced functional materials. Here we report the unprecedented inclusion of paracetamol in the cavities of amorphous materials constituted of M12L8, interlocked MOCs synthesized by mechanochemistry under kinetic control. Full structure determination of a low-crystallinity and low-resolution powders of the M12L8 poly-[n]-catenane including paracetamol has been carried out combining XRD data and Density Functional Theory (DFT) calculations using a multi-step approach. Each M12L8 cage contains six paracetamol guests which is confirmed by thermal analysis and NMR spectroscopy. The paracetamol loading has been also carried out by the instant synthesis method using a saturated paracetamol solution in which TPB and ZnI2 self-assemble immediately (i. e., 1-5 seconds) encapsulating ~7 paracetamol molecules in the M12L8 nanocages under kinetic control also giving a good selectivity. Benzaldehyde has been included in the M12L8 cages using amorphous M12L8 polycatenanes showing that the icosahedral cages can serve as potential nanoreactors for instance to study Henry reactions in the solid-state.

Organic Mechanochromic Luminescent Materials with Self-Recovering Characters.

Recently, applied research on stimuli-responsive materials with luminescence-switching characteristics has been conducted in various fields. A representative phenomenon of stimuli-responsive luminescent materials is mechanochromic luminescence (MCL), which exhibits luminescent color change induced by mechanical stimuli such as grinding. These materials are among the most prominent candidates for security and sensing applications. Interestingly, some mechanochromic luminescent materials have shown self-recovery character, in which their original luminescent color can be recovered by just standing under ambient conditions after grinding. Although there are more and more reports of such materials in recent years, the fundamental principles of molecular design still remain elusive. In this concept, we summarize distinctive advances in mechanochromic luminescent materials with self-recovery according to the core structures of luminescent molecules. Controlling amorphous state by introducing substituents such as alkyl or polar groups is effective method to provide self-recovering properties.

Near-infrared Sb2S3 metasurface with giant and tunable circular dichroism

Tunable circular dichroism (CD) is crucial for the development of chiral imaging, biosensing, and optical communication etc Herein, by employing the ultralow loss reversible phase-change materials Sb2S3, we achieved the giant and tunable CD signal in a chiral double-L array. Numerical results show that CD strength of the Sb2S3 metasurface can be over 0.9 in both amorphous and crystalline states. Strikingly, the resonant wavelength shift induced by the phase change of Sb2S3 reaches 93 nm, proving that the proposed metasurface possesses excellent tunability. In addition, the physical mechanism of the giant CD response is explained via multipole analysis. The proposed Sb2S3 metasurface capable of giant and tunable CD effect will facilitate the design of tunable dichroic devices.

Amorphous bimetallic-organic framework enable accelerated redox kinetics and polysulfide trapping for lithium-sulfur batteries

Severe polysulfide dissolution and shuttling during charging and discharging are the main challenges hindering the practical application of lithium-sulfur (Li-S) batteries. Constructing functional separators is considered as an economical and convenient way to suppress the shuttle effect and improve the kinetics of Li-S chemistry. In this work, partially ligand-deficient amorphous bimetallic MOF material (aFeNi-MOF) is designed via a ligand competition strategy and employed as a separator modifier. The aFeNi-MOF not only promotes the rapid transportation of ions, but also enhances the chemisorption and catalytic capability on sulfur species, enabling accelerated redox kinetics and polysulfide trapping in Li-S batteries. Consequently, the assembled coin cell using aFeNi-MOF-modified separator delivered a high reversible capacity of 931.1 mAh/g at 1C, a long cycle life of more than 500 cycles and a low capacity decay of 0.084 % per cycle. Meanwhile, the areal capacity of 3.70 mAh cm−2 can be achieved under a high sulfur loading of 4.5 mg cm−2 and low electrolyte usage, meeting the requirement of areal capacity for commercial applications of Li-S batteries.