Search Results (43)

Rare-earth oxide (REO) nanoparticles (NPs)—such as cerium (CeO₂), samarium (Sm₂O₃), neodymium (Nd₂O₃), terbium (Tb₄O₇), and praseodymium (Pr₂O₃)—have demonstrated strong antimicrobial activity against multidrug-resistant bacteria. Their effectiveness is attributed to unique physicochemical properties, including oxygen vacancies and redox cycling, which facilitate the generation of reactive oxygen species (ROS) that damage microbial membranes and biomolecules. Additionally, electrostatic interactions with microbial surfaces and sustained ion release contribute to membrane disruption and long-term antimicrobial effects. REOs also inhibit bacterial enzymes, DNA, and protein synthesis, providing broad-spectrum activity against Gram-positive, Gram-negative, and fungal pathogens. However, dose-dependent cytotoxicity to mammalian cells—primarily due to excessive ROS generation—and nanoparticle aggregation in biological media remain challenges. Surface functionalization with polymers, peptides, or metal dopants (e.g., Ag, Zn, and Cu) can mitigate cytotoxicity and enhance selectivity. Scalable and sustainable synthesis remains a challenge due to high synthesis costs and scalability issues in industrial production. Green and biogenic routes using plant or microbial extracts can produce REOs at lower cost and with improved safety. Advanced continuous flow and microwave-assisted synthesis offer improved particle uniformity and production yields. Biomedical applications include antimicrobial coatings, wound dressings, and hybrid nanozyme systems for oxidative disinfection. However, comprehensive and intensive toxicological evaluations, along with regulatory frameworks, are required before clinical deployment. Full article

DFT calculations have been employed to investigate the impact of Sm dopant(s) on the structure and stability of periodic CeO₂(111) slab and Ce₁₄₀O₂₈₀ nanoparticle systems. We found that substituting Ce ion(s) with Sm ion(s) in the surface layer yields the most favorable doped configurations in both systems. Further, we evaluated how Sm ion(s) modify the reducibility of the systems—a key process in the catalytic applications of ceria. It has been found that a substantial reduction in oxygen vacancy formation energy occurs due to the presence of Sm ion(s), with values of 1.24 and 0.29 eV for mono- and bi-doped CeO₂(111), respectively, which are considerably lower than 2.43 eV obtained for the pristine ceria slab. As the system changes from slab to nanoparticle, mono-doping reduces this energy to 0.25 eV—about four times lower than that calculated for the pristine Ce₁₄₀O₂₈₀ nanoparticle. The presence of a second Sm ion within the nanoparticle leads to a dramatic decrease in E_vac, making the reduction process exothermic. In either slab or nanoparticle models, the Sm³⁺ ions prefer to be in close proximity to each other, and the formation of oxygen vacancies is most energetically favorable in the vicinity of Sm³⁺ ions. Full article

The activity of Co- and Ni-containing ceria-based catalysts for water–gas shift (WGS) reaction were examined in this work. The catalysts were prepared by the urea co-precipitation method. Sm and Pr dopant (5 wt.%) was used as a structural stabilizer of CeO₂, while Co or Ni was used in a small amount (1 wt.%). H₂-TPR experiments indicate that both Sm and Pr addition increased the reducibility of CeO₂. Among the studies’ catalysts, 1%Ni/Ce5%SmO exhibited the highest WGS activity. In addition, WGS rate was measured in the temperature range of 200–400 °C for Ni supported on CeO₂, Ce5%SmO, and Ce5%PrO. The activation energy of the reaction over 1%Ni/Ce5%SmO was 57 kJ/mol, while it was 61 and 66 kJ/mol, respectively, over 1%Ni/Ce5%PrO and 1%Ni/CeO₂ catalysts. A WGS reaction mechanism, CO adsorbed on the metal cluster is oxidized by oxygen supplied from the CeO₂ support at the metal–ceria interface. This oxygen is then re-oxidized by H₂O, which caps the oxygen vacancy on the ceria surface, and thereby oxygen vacancies serve as active sites for the WGS reaction. Raman experiments indicate that the presence of Sm in 1%Ni/Ce5%SmO catalyst promoted the formation of oxygen vacancies, leading to enhanced WGS performance. Full article

This study investigates the temperature-driven transmission switching behavior of our proposed smart glass, which utilizes a biphasic liquid crystal system under continuous application of a distinctive homeotropic (H) state voltage (V_H). By ascertaining V_H at temperatures near the phase transition point, the minimum voltage required to sustain the H state in the smectic A* (SmA*) phase is identified. Interestingly, this minimum V_H is unable to induce the H state in the chiral nematic (N*) phase, thereby maintaining a low-transmission scattering state; i.e., the focal conic (FC) state. This empowers passive, bidirectional optical switching between the transparent H state (in the SmA* phase) and the scattering FC state (in the N* phase) in an unaligned liquid crystal cell. This work employs two dissimilar chiral dopants, R811/S811 and CB7CB/R5011, both capable of inducing the SmA* phase. Neither resulting cell system underwent surface orientation treatment, and a black dye was incorporated to enhance the contrast ratio. The results indicate that the more efficacious CB7CB/R5011 system achieves a contrast ratio of 17 between the transparent and scattering states, with a corresponding haze level of 78%. To further reduce energy consumption, the experimental framework was transitioned from a continuous-voltage to a variable-voltage mode, giving rise to an increased haze level of 88%. The proposed switching scheme holds promise for diverse applications, notably in smart windows and light shutters. Full article

In this study, we report the fabrication and multi-technique characterization of pure and rare-earth (RE)-doped ZnO thin films using nanostructured microclusters synthesized via electrospinning followed by calcination. Lanthanum (La), erbium (Er), and samarium (Sm) were each incorporated at five concentrations (0.1–5 at.%) into ZnO, and the resulting powders were drop-cast as thin films on glass substrates. This approach enables the transfer of pre-engineered nanoscale morphologies into the final thin-film architecture. The morphological analysis by scanning electron microscopy (SEM) revealed a predominance of spherical nanoparticles and nanorods, with distinct variations in size and aspect ratio depending on dopant type and concentration. X-ray diffraction (XRD) and Rietveld analysis confirmed the wurtzite ZnO structure with increasing evidence of secondary phase formation at high dopant levels (e.g., Er₂O₃, Sm₂O₃, and La(OH)₃). Raman spectroscopy showed peak shifts, broadening, and defect-related vibrational modes induced by RE incorporation, in agreement with the lattice strain and crystallinity variations observed in XRD. Elemental mapping (EDX) confirmed uniform dopant distribution. Optical transmittance exceeded 70% for all films, with Tauc analysis revealing slight bandgap narrowing (Eg = 2.93–2.97 eV) compared to pure ZnO. This study demonstrates that rare-earth doping via electrospun nanocluster precursors is a viable route to engineer ZnO thin films with tunable structural and optical properties. Despite current limitations in film-substrate adhesion, the method offers a promising pathway for future transparent optoelectronic, sensing, or UV detection applications, where further interface engineering could unlock their full potential. Full article

Dielectric capacitors have become a key component for energy storage systems, owing to their exceptional power density and swift charge–discharge performance. In a series of lead-free ferroelectric ceramic materials, BaSn_xTi_1-xO₃ (BTS) received widespread attention due to its unique properties. However, BTS ceramics with high Sn content have high efficiency (η) but low recovery energy storage density (W_rec). We incorporated the Sm element into BTS ceramics and aimed to optimize both efficiency and recoverable energy density at moderate Sn content. With the synergistic effect between Sm and Sn, the optimal composition was found at 5% Sn content with 1% low-level Sm dopants, where the energy storage density reached 0.2310 J/cm³ at 40 kV/cm. Furthermore, the thermal stability of the ceramic was investigated using temperature-dependent dielectric spectroscopy, in situ XRD, and temperature-dependent hysteresis loops. With Sm doping, the fluctuation of W_rec decreased from 18.48% to 12.01%. In general, this work not only enhances the understanding of samarium dopants but also proposes strategies for developing lead-free ferroelectric ceramics with superior energy storage properties. Full article

On the basis of a microscopic model and employing Green’s function technique, the effects of temperature, size, and ion doping on the magnetization and phonon energy of the A_1g mode in double perovskites Ba₂FeReO₆ and Sr₂CrReO₆—both in bulk and nanoscale samples—are investigated for the first time. The Curie temperature T_C and magnetization M decrease as nanoparticle size is reduced. Doping with rare-earth ions such as Sm, Nd, or La at the Ba or Sr sites further reduces M. This behavior originates from the compressive strain induced by the smaller ionic radii of the dopant ions compared to the host ions. As a result, the antiferromagnetic superexchange interaction between Fe or Cr and Re ions is enhanced, along with an increase in the magnetic moment of the Re ion. The dependence of the band gap energy of Sr₂CrReO₆ on temperature, size, and doping is also studied. Near the magnetic-phase-transition temperature T_C, anomalies in phonon energy and damping indicate strong spin–phonon coupling. The theoretical calculations show good qualitative agreement with experimental data. Full article

The La-doped ternary Zintl phase Ca_10.43(3)La_0.57Sb_9.69(1) was successfully synthesized by arc melting, and the title compound adopted the Ho₁₁Ge₁₀-type structure with a tetragonal I4/mmm space group (Z = 4, Pearson code tI84). The complex crystal structure is composed of (1) the four different kinds of cationic Ca or Ca/La mixed sites surrounded by seven or nine Sb atoms and (2) the 3-dimensional cage-shaped anionic frameworks built by the other two types of Sb atoms. In particular, the La dopants preferred to occupy the Ca4 and Ca1 sites, and this specific cationic-site preference can be rationalized by both electronic and size-factor criteria. Moreover, the ca. 16% occupational deficiency observed at the Sb3 site was attributed to the energetically unfavorable antibonding character of the Sb3–Sb3 bond in the [Sb3]₄ tetramers, according to a series of DFT calculations. A crystal Hamilton overlap population curve analysis also proved that the title compound Ca_10.43(3)La_0.57Sb_9.69(1) tried to keep the valence electron count below 71.02 to remain energetically stable in the Ho₁₁Ge₁₀-type phase. Measurements of temperature-dependent electrical transport properties revealed that the La doping indeed enhanced the electrical conductivity of Ca_10.43(3)La_0.57Sb_9.69(1) compared to the un-doped Ca₁₁Sb₁₀. However, unlike other rare earth metal (RE)-doped compounds in the Ca_11−xRE_xSb₁₀ (RE = Nd and Sm) system that display semiconducting behavior, the La-doped title compound showed poor metallic electrical properties. The positive values of Seebeck coefficients indicated the p-type character of the title compound despite the successful n-type La doping, and this should be attributed to Sb deficiency. Full article

In this study, the mechanochemical preparation of nanocrystalline CaF₂:Sm³⁺ by ball milling calcium acetate hydrate, samarium (III) acetate hydrate, and ammonium fluoride is reported. The photoluminescence of the as-prepared CaF₂:Sm³⁺ shows predominantly Sm^3+ 4G_5/2 → ⁶H_J(J = 5/2, 7/2, 9/2, and 11/2) f-f luminescence, but intense electric dipole allowed 4f⁵5d (T_1u) → 4f^6 7F₁ (T_1g) luminescence by Sm²⁺ was generated upon X-irradiation. In comparison with the co-precipitated CaF₂:Sm³⁺, the conversion of Sm³⁺$\to$ Sm²⁺ in the ball-milled sample upon X-irradiation is significantly lower. Importantly, the present results indicate that the crystallite size and X-ray storage phosphor properties of the lanthanide-doped nanocrystalline CaF₂ can be modified by adjusting the ball milling time, dopant concentration and post-annealing treatment, yielding crystallite sizes as low as 6 nm under specific experimental conditions. Full article

The formation and evolution of SmCo₅/Sm₂Co₁₇ (1:5_H/2:17_R/H) cellular structures play an essential role in understanding the coercivity of Sm-Co magnets. Herein, the pristine and different elemental-doped 1:5/2:17_R and 1:5/2:17_H interfaces are investigated to evaluate the elemental site preferences, interface configurations, and magnetic properties in Sm₂Co₁₇-type magnets with general alloy elements M (M = Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Al, Si, and Ga). Comparing the calculated results of 1:5/2:17_H with those of the 1:5/2:17_R interface, we found that Cu and Mn always segregate at the 1:5 phase, and Ga elements first appear at the 1:5 phase in 1:5/2:17_H and then change to the 2:17 phase in 1:5/2:17_R. While Ti, V, Fe, Zn, Al, and Si elements always tend to segregate at the 2:17 phase, Ni first segregates at the 2:17 phase in 1:5/2:17_H and then occupies the 1:5 phase of 1:5/2:17_R. The 1:5/2:17_H interface along the c-axis expands about 1.98~3.28%, while the 1:5/2:17_R interface slightly shrinks about 0.04~0.87% after element doping. This suggests that different interface stress behaviors exist for high-temperature and room-temperature phase Sm₂Co₁₇-type magnets. Furthermore, Mn, Fe, and Ga doping improved the saturation magnetization strength. Our results provide new insights into understanding the effect of elemental doping at the interfaces of 1:5_H/2:17_R cellular structures. Full article

Mg₃Sb₂-based materials, part of the Zintl compound family, are known for their low thermal conductivity but face challenges in thermoelectric applications due to their low energy conversion efficiency. This study addressed these limitations through first-principles calculations using the CASTEP module in Materials Studio 8.0, aiming to enhance the thermoelectric performance of Mg₃Sb₂ via strategic doping. Density functional theory (DFT) calculations were performed to analyze electronic properties, including band structure and density of states (D.O.S.), providing insights into the influence of various dopants. The semiclassical Boltzmann transport theory, implemented in BoltzTrap (version 1.2.5), was used to evaluate key thermoelectric properties such as the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and electronic figure of merit (eZT). The results indicate that doping significantly improved the thermoelectric properties of Mg₃Sb₂, facilitating a transition from p-type to n-type behavior. Bi doping reduced the band gap from 0.401 eV to 0.144 eV, increasing carrier concentration and mobility, resulting in an electrical conductivity of 1.66 × 10⁶ S/m and an eZT of 0.757. Ge doping increased the Seebeck coefficient to −392.1 μV/K at 300 K and reduced the band gap to 0.09 eV, achieving an electronic ZT of 0.859 with low thermal conductivity (11 W/mK). Si doping enhanced stability and achieved an electrical conductivity of 1.627 × 10⁶ S/m with an electronic thermal conductivity of 11.3 W/mK, improving thermoelectric performance. These findings established the potential of doped Mg₃Sb₂ as a highly efficient thermoelectric material, paving the way for future research and applications in sustainable energy solutions. Full article

A series of orange-red emitting Li₆Y(BO₃)₃: Sm³⁺ (LYBO: Sm³⁺) phosphors were produced via the high temperature solid-state method. The structure, morphology, element distribution and photoluminescent behavior of these phosphors were thoroughly examined. XRD analysis confirmed that all samples exhibited a pure phase. Under 404 nm excitation, the emission spectra included four distinct transitions of Sm³⁺, attributed to ⁴G_5/2→⁶H_5/2 (565 nm), ⁴G_5/2→⁶H_7/2 (613 nm), ⁴G_5/2→⁶H_9/2 (647 nm) and ⁴G_5/2→⁶H_11/2 (708 nm). The ideal doping level for LYBO: xSm³⁺ is x = 0.05, and the concentration quenching primarily stems from electric dipole–dipole interactions among the ions. As the amount of Sm³⁺ dopant was increased, the fluorescence lifetime decreased. The CIE indicates that LYBO: 0.05Sm³⁺ is located in the orange-red region, exhibiting a high color purity (99%) and low color temperature (1711 K). The phosphor demonstrated excellent thermal stability and its activation energy was 0.3238 eV. In summary, LYBO: Sm³⁺ is a potential orange-red phosphor that can be coated onto near-ultraviolet chips suitable for W-LEDs. Full article

This investigation focuses on the impact of Sm³⁺ dopants on BaBi₂Nb₂O₉ (BBN) ceramics. These ceramics were obtained using the traditional solid state reaction approach. Techniques like scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were employed to explore the structure and morphology of the ceramics. The results showed that the chemical composition of the ceramic samples matched well with the initial ceramic powder stoichiometry. Increasing the amount of samarium resulted in a slight reduction in the average ceramic grain size. The ceramics exhibited a tetragonal structure categorized under the space group I4/mmm. The electrical properties were analyzed using complex impedance spectroscopy (SI) across various temperatures and frequencies, revealing that both grains and intergranular boundaries are significant in the material’s conductivity. Full article

Using a microscopic model and the Green’s function theory, the size and co-doping effects on the multiferroic and optical (band gap) properties of BiFeO₃ (BFO) nanoparticles are investigated. The magnetization increases, whereas the band gap energy decreases with decreasing nanoparticle size. The substitution with Co/Mn, Nd/Sm, Ce/Ni, and Cd/Ni is discussed and explained on a microscopic level. By the ion co-doping appear different strains due to the difference between the doping and host ionic radii, which leads to changes in the exchange interaction constants for tuning all properties. It is observed that by co-doping with Nd/Sm at the Bi site or with Co/Mn at the Fe site, the multiferroic properties are larger than those by doping with one ion. Moreover, by doping with Ni, the multiferroic properties are reduced. But by adding another ion (for example Ce or Cd), an increase in these properties is obtained. This shows the advantages of the co-doping, its flexibility, and its greater possibility of tuning the multiferroic properties compared to single ion substitution. The band gap energy decreases for all co-dopants. The polarization increases with increasing magnetic field. This is evidence of magnetoelectric coupling, which is enhanced by co-doping with Co/Mn. The observed theoretical results are in good qualitative agreement with the existing experimental data. Full article

The role of dopants (Sm, Tb and Pr) on the water–gas shift performance of CeO₂-based materials was studied. Modification of CeO₂ with Sm significantly improved the water–gas shift performance. The catalytic activities of doped CeO₂ were increased when compared with the catalytic activities of pure ceria (65% conversion at 600 °C for Ce5%SmO and 50% conversion at 600 °C for CeO₂). The key factors driving the water–gas shift performance were reduction behavior and oxygen vacancy concentration. In the redox mechanism of the WGS reaction, CeO₂ plays a crucial role in transferring oxygen to CO through changes in the oxidation state. Therefore, Sm is effective in catalyzing the water–gas shift activity because the addition of Sm into CeO₂ decreases the surface reduction temperature and alters the oxygen transportation ability through the redox mechanism. XRD results suggested that Mⁿ⁺ (M = Sm, Tb and Pr) incorporate into ceria lattice to form a solid solution resulting in unit cell enlargement. The defect structure inside the CeO₂ lattice generates a strain on the oxide lattice and facilitates the generation of oxygen vacancies. XANES analysis revealed that Sm reduced CeO₂ easily by transporting its electron into the d-orbitals of Ce, thus giving rise to more Ce³⁺ at the CeO₂ surface. The presence of Ce³⁺ is a result of oxygen vacancy. Therefore, the high content of Ce³⁺ provides more oxygen vacancies. The oxygen vacancy formation results in easy oxygen exchange. Thus, reactive oxygen species can be generated and easily reduced by CO reactant, which enhances the WGS activity. Full article