Materials Advances最新文献

The use of luminescent tracers in plastic recycling presents a novel application opportunity for classical phosphor materials, such as co-doped YPO₄. In this study, we report the optimization of the photoluminescence quantum yield (PLQY) of YPO₄:Yb³⁺/Er³⁺ phosphors via a flux-assisted solid-state synthesis approach. Upon excitation of Yb³⁺ ions at 940 or 980 nm, efficient energy transfer to Er³⁺ ions enables strong emission at 1540 nm, with a maximum PLQY of 78% achieved under optimized synthesis conditions. This performance was obtained by annealing the phosphor at 1100 °C for 12 h in the presence of LiCl flux. Notably, a reduced synthesis temperature of 1000 °C and a much shorter annealing time of 3 h still yielded a high PLQY (72%) when the flux was present. To demonstrate practical applicability, the phosphors were integrated into two model systems: (1) dispersion of 300 ppm phosphor in transparent silicone (emulating a bulk polymer), and (2) surface printing on polyethylene foil with a loading of 10 µg cm⁻² (emulating a label). In both cases, the measured brightness was significantly lower than that of a commercial Y₂O₂S:Yb³⁺/Er³⁺ phosphor, despite its much lower PLQY of only 7%. This discrepancy was attributed to the non-optimal particle size distribution of the YPO₄ phosphor, which induced non-optimal scattering, absorption, and emission losses in both demonstrator matrices. After optimizing particle size via dry milling, the luminescence performance of the YPO₄-based phosphor surpassed that of the commercial reference in both configurations, confirming its suitability for use in luminescent tagging of plastics.

Silicon (Si) is a high-capacity anode material for lithium-ion batteries; however, its large volume change during cycling causes severe mechanical degradation. We show that optimizing the delithiation cut-off voltage effectively suppresses interfacial delamination in Si thin-film anodes. By limiting delithiation at 0.6 V, partial Li retention reduces interfacial stress and prevents structural collapse, achieving 92% capacity retention (2200 mAh g⁻¹) after 100 cycles. Cross-sectional analyses confirmed suppressed shrinkage and strong adhesion to the substrate. This simple voltage-control strategy provides a universal and practical route to enhance the durability of Si-based and other alloy-type anodes.

The confluence of metal–organic frameworks (MOFs) and conductive materials has revolutionized gas sensing technology. This study presents a synergistic composite of MIL-101(Cr) and reduced graphene oxide (rGO) for enhanced ammonia gas sensing. rGO–MIL-101(Cr) composites with varying weight percentages of MIL-101(Cr) were synthesized and further characterised using various techniques. By harnessing the exceptional surface area and tailored pore structure of MIL-101(Cr) in tandem with the superior conductivity of rGO, the composite exhibits remarkable sensitivity and fast response times. Among the prepared compositions, rGO–20 wt% MIL-101 (Cr) has demonstrated exceptional sensitivity towards ammonia detection, with a sensitivity of −18.87 for 60 000 ppm and −5.24% for 2000 ppm of ammonia gas and a discernible response at concentrations as low as 1 ppm. Notably, the composite's response remained remarkably consistent and stable, even after one year. This outstanding durability and stability underscore the composite's potential for reliable and long-term ammonia sensing applications. At this percentage, the highest sensitivity is due to the perfect coordination bonding between ammonia molecules and the chromium nodes in MIL-101(Cr), modulating its electrical properties. The formation of a perfect interface between MIL-101 (Cr) and rGO facilitates efficient charge transport, thereby enabling precise detection of ammonia gas. The FE-SEM and TEM analyses clearly show the presence of such an interface. Notwithstanding the comparable or superior sensing capabilities of existing ammonia sensors under optimal conditions, their practical utility is frequently compromised by the susceptibility of the constituent materials to humidity. In contrast, our rGO–MIL-101(Cr) composite exhibits a unique synergy of outstanding sensing performance and notable stability under moist conditions due to its remarkably high surface area and durable architecture. This exclusive combination of properties enables our material to surpass the performance of existing sensors in real-world settings, where moisture is a common factor, and thus offers a significant advantage over existing sensors. This research highlights the potential of MOF-based composites for advanced gas sensing applications, paving the way for further exploration and development of novel sensing platforms.

The rising demand for clean and green energy sources has sparked global interest in sustainable hydrogen production technologies. To address this problem, photocatalytic water splitting has emerged as a promising solution for the sustainable production of green hydrogen and oxygen. We investigate the hydrogen adsorption Gibbs free energy for hydrogen evaluation reaction (HER) and rate-limiting Gibbs free energy for oxygen evolution reaction (OER) to analyse the catalytic activity of the transition metal (TM) intercalated PtXY/ζ-phosphorene (X ≠ Y; X, Y = S, Se, Te) van der Waals heterostructures (vdWHs). Our workflow involves generating a large dataset, followed by performing high-throughput first-principles density functional theory (DFT) calculations on a small fraction of the dataset to obtain the training dataset for a machine learning (ML) framework. Incorporating the ML with the DFT workflow, we obtained 13 potential catalysts for HER and 6 potential catalysts for OER. The interlayer distance of the heterostructures and the bond length between the Pt and X atom emerged as the most influential features for HER, whereas the choice of adsorption site is one of the major OER descriptors. Overall, ML approach integrated with high-throughput first principles calculations is promising for the prediction of potential TM-intercalated vdWHs photocatalysts for water splitting.

Metal-functionalized carbon nanotubes (CNTs) have emerged as versatile nanostructures with tunable properties for energy conversion, storage, and environmental remediation. In this study, we integrate experimental investigations with theoretical modeling to explore the structure–property relationships and multifunctional performance of CNTs decorated with transition metal nanoparticles (Ni, Cu, Ag) and their synergistic combinations (Ni–Cu–Ag). A scalable and facile synthesis route was employed to fabricate these nanocomposites, which were thoroughly characterized to evaluate their structural, morphological, optical, and surface chemical features. The metal-functionalized CNTs demonstrated significant enhancements in oxygen evolution reaction (OER) activity, capacitive energy storage, and photocatalytic degradation of organic pollutants. Notably, the ternary CNT–Ni–Cu–Ag nanocomposite exhibited outstanding OER performance with an overpotential of 382 mV at 50 mA cm⁻² and a Tafel slope of 73 mV dec⁻¹, along with a high specific capacitance of 1451 F g⁻¹ and excellent stability (98% retention after 5000 cycles). Furthermore, the material achieved remarkable photocatalytic degradation efficiencies of ciprofloxacin (98.5%) and diclofenac sodium salt (86%) within 120 minutes under visible light. Complementary density functional theory (DFT) simulations revealed the preferential adsorption of metal nanoparticles on the CNT surface and their role in modulating the electronic band structure, thereby rationalizing the enhanced catalytic and optoelectronic behaviour. These results highlight the promise of metal-functionalized CNTs as multifunctional platforms for next-generation energy conversion, storage, and environmental remediation technologies.

The synthesis and characterization of perylene diimide (PDI) derivatives functionalized by electron donating groups at their bay and imide positions have been reported. Five different PDI derivatives were synthesized and their linear optical and third-order non-linear optical (NLO) properties were studied. The NLO measurements of the synthesized PDI derivatives were conducted under nanosecond (ns) and femtosecond (fs) laser excitation conditions, using the Z-scan technique employing 4 ns, 1064/532 nm and 70 fs, 800/400 nm laser pulses. A noticeable tuning of the NLO character between the synthesized PDI derivatives was observed, revealing the importance of the functionalization of the PDI core by the anchored electron donating units. The largest NLO value was achieved by the incorporation of p-aminoazobenzene at the PDI bay position. The experimental NLO findings and trends were further corroborated with theoretical computations of UV-Vis spectra and NLO response, performed using density functional theory (DFT). It was found that both experiments and simulations satisfactorily convey changes in the NLO response between the studied PDI derivatives. The mechanism that could lead to an efficient tuning of the PDIs' NLO response, is associated with the modification of their electronic character resulting by the proper PDI core functionalization.

When a liquid drop makes first contact with any surface, the unbalanced surface tension force drives the contact line, causing spreading. For Newtonian or weakly elastic, non-Newtonian liquids, either liquid inertia or viscosity, or a combination of the two, resists spreading. In this work, we investigate how drop elasticity influences spreading dynamics. We conduct dynamical experiments with polyacrylamide drops of varying polymer concentrations to impart varying degrees of elasticity. Using high-speed imaging, we focus on the very first moments of spreading on glass substrates. For moderate and high Young's modulus values, we observe that the early-time spreading dynamics obey a viscous-capillary regime characterized by a power-law evolution of the spreading radius. However, the process transitions to a different regime on a timescale comparable to the characteristic viscoelastic relaxation timescale. We interpret this latter regime using a theoretical model invoking the standard linear model of viscoelasticity. For viscoelastic inks with moderate print speeds, the dynamical behavior investigated in this study can provide valuable insights into how to efficiently control such moving contact lines with non-trivial elasticity.

Stimuli-responsive organic materials with dynamically configurable luminescence represent a transformative class of materials with far-reaching implications for next-generation sensing, secure data encryption, and high-performance display technologies. The scope of optical tuning and the ability to precisely modulate emission properties in response to external stimuli offer opportunities for the development of cutting-edge materials that enable breakthroughs in real-time detection, adaptation, and intelligent photonic devices. Focusing on the rational design of luminescent solids, we report three Schiff bases obtained by condensation of hydroxy naphthaldehyde with para-arsenate aniline [1, λ_max 558 nm], ortho-arsenate aniline [2, λ_max 525 nm], and ortho-sulfonate aniline [3, λ_max 535 nm], differing in the position and nature of arsenate and sulfonate functional groups. Anticipated variation of optical properties in the new solid forms is triggered by variation in intra- and intermolecular factors. Structural studies reveal that solid-state emission arises due to the absence of any significant face-to-face π-stacking interactions, while emission tuning is realised through molecular electronic effects generated by functional groups. Multi-stimuli responsive studies carried out for 1–3 indicate the occurrence of crystallization-induced enhanced emission (CIEE) as the emission intensities decline in amorphous grounded forms, the observation further supported by thin film studies. Molecular solids 1 and 3 also exhibit reversible thermofluorochromism, arising due to breathing of lattice water in 3 and phase changes in non-solvated crystals of 1. A non-emissive methanolic solution of 2 exhibits highly selective sensing for Zn(II) ions with an LOD value of 4.9 × 10⁻⁶ M.

This research explores the structural, dielectric, and electrical transport characteristics of polycrystalline La_2−xSr_xFeMnO₆ compounds with varying strontium concentrations (x = 0.0, 0.1, 0.2, 0.5, 1.0, 1.5, and 2.0). These compounds were prepared through the solid-state reaction technique at high temperatures. Rietveld refinement of their XRD data confirms a re-entrant structural phase transition (cubic–rhombohedral–cubic) induced by Sr doping. The vibrational study of (Fe/Mn)O₆ octahedra was carried out by Raman and FTIR spectroscopies. X-ray photoelectron spectroscopy (XPS) results demonstrated the presence of mixed valence oxidation states (+3 and +4) of Fe and Mn cations in the measured samples. The temperature-dependent resistivity data of these compounds have been explained by the long-range electron hopping and short-range polaron hopping conduction mechanisms at high- and low-temperature regions, respectively. Their dielectric constant (ε′) exhibits dispersion behavior, which is attributed to the Maxwell–Wagner interfacial polarization and hopping mechanism of charge carriers. The leakage current density has been explained on the basis of Ohmic conduction mechanism and space-charge-limited conduction (SCLC) mechanism. All these studied properties are strongly influenced by structural distortion-induced strain, oxygen vacancies, Schottky defects, and possible charge ordering. The low leakage current density of these materials with a high dielectric constant make them promising for application in electronic devices.

Metallic thin-films are found in a wide range of applications, from energy storage to high-power semiconductors used for green energy technologies. Engineering the growth and treatment of metallic thin-films influences their microstructures and residual stress states, which in turn affect their performance and properties. Here, we uncover the influence of tramp elements on the microstructural equilibration in electroplated Cu thin-films during annealing and evaluate the residual stress states in those Cu thin-films. The residual stress gradients within grains of two Cu thin-films, deposited from different electrolytes, are analysed utilising machine learning (ML) based high-resolution electron backscatter diffraction (HR-EBSD). In order to obtain quantitatively comparable stress mappings for both thin-films, simulated stress-free Kikuchi patterns are chosen as common references for HR-EBSD. Despite vastly different grain sizes after identical annealing treatment, similar stress gradients are present within the grains on both thin-film surfaces. The elemental composition at grain boundaries is analysed with atom probe tomography, revealing that S, Cl and O agglomerate in similar concentrations in the ppm-range at grain boundaries of both thin-films. The methodology corroborates that tramp element drag on grain boundaries during annealing may hinder grain growth from the as-deposited nanocrystalline structure, limiting effective stress relaxation and ultimately triggering failure modes.