Search Results (65)

A novel catalyst, Tm₂FeSbO₇, was synthesized by employing the solid-phase high-temperature sintering method, and, for the first time, it was utilized to create a Z-type heterojunction with BiYO₃. A direct Z-scheme Tm₂FeSbO₇/BiYO₃ heterojunction photocatalyst (TBHP) was successfully produced by employing the ball-milling technique. X-ray diffraction analysis results indicated that Tm₂FeSbO₇ crystallized in a cubic pyrochlorestructure which owned the Fd-3m space group, with a unit cell parameter of 10.1769 Å, whereas BiYO₃ displayed a fluorite structure in the Fm-3m space group, with a unit cell parameter of 5.4222 Å. The Mossbauer spectrum of Tm₂FeSbO₇ showed that Fe³⁺ ions might locate at octahedral sites. The measured bandgap widths for the TBHP, Tm₂FeSbO_7, and BiYO₃ were 2.14 eV, 2.21 eV, and 2.30 eV, respectively. Multiple experimental results demonstrated that the TBHP exhibited a higher valence band ionization potential, a narrower band gap width, and a higher removal efficiency of the sulfamethoxazole (SMX) compared with the Dy₂TmSbO₇/BiHoO₃ heterojunction photocatalyst. Under visible-light irradiation (VISLI) of 115 min, the TBHP showcased exceptional photocatalytic elimination performance; therefore, the elimination rate of the SMX and the total organic carbon (TOC) mineralization rate reached 99.51% and 98.10%, respectively. In contrast to single-component Tm₂FeSbO₇, BiYO_3, or conventional nitrogen-doped titanium dioxide (N-TiO₂) catalyst, the TBHP exhibited removal efficiency enhancement for degrading the SMX by 1.17 times, 1.31 times, or 4.06 times. Simultaneously, the matching mineralization rate for removing the TOC density by employing the TBHP was 1.20 times, 1.34 times, or 4.73 times higher than that by employing Tm₂FeSbO₇, BiYO₃, or conventional N-TiO₂. Above experimental results indicated that the mineralization efficiency for removing TOC density by employing the TBHP was higher than that by employing Tm₂FeSbO₇, BiYO₃, or N-TiO₂. Radicals trapping experiments and the electron paramagnetic resonance spectroscopy results revealed that hydroxyl radicals, superoxide anions, and photoinduced holes were the primary active species during the catalytic elimination course of the SMX by employing the TBHP under VISLI. The results demonstrated that the direct Z-scheme TBHP, which was developed in this study, exhibited the maximal removal efficiency for degrading the SMX in contrast to Tm₂FeSbO₇, BiYO₃, or N-TiO₂. Additionally, the possible elimination routes and elimination mechanisms of the SMX were proposed. Therefore, an important scientific foundation for developing high-performance heterojunction catalysts was established. Full article

In this work, we synthesized blue-fluorescent nitrogen-doped carbon quantum dots (N-CQDs) via a facile, economical, and environmentally friendly one-pot synthesis, using citric acid as the carbon source and polyethyleneimine (PEI) as the nitrogen dopant. The as-prepared N-CQDs exhibited uniform size distribution, with an average diameter of approximately 3 nm and a quantum yield of up to 23.6%. Based on the mechanism of HClO-triggered static fluorescence quenching and oxidation of surface amine groups on the N-CQDs, we established a quantitative detection platform for hypochlorous acid (HClO). The proposed method demonstrated a linear response over the concentration range of 0–40 μmol/L, with a detection limit as low as 0.17 μmol/L. It also featured a rapid response time (within 2 min), high selectivity, and strong anti-interference capability against various common species, including Cl⁻, H₂O₂, NO₂⁻, NO₃⁻, TBHP, TBO•, Br⁻, I⁻, S²⁻, F⁻, O²⁻ and HO•. Furthermore, the probe was successfully applied to detect HClO in real-world samples such as river water and beer. Owing to its outstanding photostability and low toxicity, it proved highly effective for monitoring intracellular HClO in living cells. Full article

A novel Z-scheme Dy₂TmSbO₇/BiHoO₃ heterostructure photocatalyst was synthesized with the ultrasound-assisted solvothermal method. The Dy₂TmSbO₇/BiHoO₃ heterojunction photocatalyst (DBHP) reflected wonderful separation efficiency of photogenerated electrons and photogenerated holes owing to the efficient direct Z-scheme heterojunction structure characteristic. The lattice parameter and the bandgap energy of the Dy₂TmSbO₇ were 10.52419 Å and 2.58 eV, simultaneously, the lattice parameter and the bandgap energy of the BiHoO₃ were 5.42365 Å and 2.25 eV, additionally, the bandgap energy of the DBHP was 2.32 eV. Above results indicated that DBHP, Dy₂TmSbO₇ or BiHoO₃ possessed an excellent ability for absorbing visible light energy, therefore, DBHP, Dy₂TmSbO₇ or BiHoO₃ owned superior photocatalytic activity for degrading the sulphamethoxypyridazine (SMP) under visible light irradiation. The removal rate of the SMP after visible light irradiation of 135 min with the DBHP was 99.47% for degrading the SMP during the photocatalytic degradation (PADA) process, correspondingly, the removal rate of the total organic carbon (TOC) concentration after visible light irradiation of 135 min with the DBHP was 98.02% for degrading the SMP during the PADA process. The removal rate of the SMP after visible light irradiation of 135 min with the DBHP was 1.15 times, 1.29 times or 2.60 times that with Dy₂TmSbO₇, BiHoO₃ or nitrogen-doped TiO₂ (N-T). Therefore, the DBHP displayed higher photocatalytic activity for degrading the SMP under visible light irradiation compared with Dy₂TmSbO₇, BiHoO₃ or N-T. Specifically, the mineralization rate for removing the TOC concentration during the PADA process of the SMP with the DBHP was 1.18 times, 1.32 times or 2.79 times that with Dy₂TmSbO₇, BiHoO₃ or N-T. In addition, the stability and reusability of the DBHP were systematically evaluated, confirming that the DBHP owned potential applicability for degrading the antibiotic pollutant, which derived from the practical industrial wastewater. Trapping radicals experiments and the electron paramagnetic resonance measurement experiments were conducted for identifying the reactive radicals, such as the hydroxyl radicals (•OH), the superoxide anions (•O₂⁻) and the photogenerated holes (h⁺), which were generated with the DBHP for degrading the SMP during the PADA process under visible light irradiation, as a result, the •O₂⁻ possessed the maximal oxidative capability compared with the •OH or the h⁺. Above results indicated the degradation mechanism and the degradation pathways which were related to the SMP. In conclusion, this study makes a significant contribution for the development of the efficient Z-scheme heterostructure photocatalysts and provides a key opinion to the development of the sustainable remediation method with the view of mitigating the antibiotic pollution. Full article

This study explores the sol–gel synthesis, structural characterization, and photocatalytic performance of Ho³⁺-doped TiO₂ nanopowders at two dopant levels (0.5 and 2 mol%). Transparent, homogeneous gels were prepared using titanium (IV) butoxide and holmium (III) nitrate pentahydrate in ethanol, followed by drying and optional annealing at 500 °C. X-ray diffraction confirmed anatase TiO₂ as the dominant crystalline phase, with Ho incorporation suppressing crystal growth and yielding smaller crystallite sizes than undoped TiO₂. FT-IR and UV-Vis spectroscopy verified complete hydrolysis–condensation during gel formation, while diffuse reflectance spectra revealed a red-shifted absorption edge, indicating reduced band gaps. SEM analysis showed nanoscale particles with agglomeration, which intensified after annealing. Photocatalytic activity was tested under UV irradiation using Crystal Violet (anionic dye) and Carmoisine (cationic dye). Annealed Ho-doped powders exhibited markedly higher degradation rates, with the 2 mol% sample achieving the greatest efficiency, particularly against Crystal Violet. These findings demonstrate that Ho³⁺ doping enhances TiO₂’s UV-driven photocatalytic activity by tailoring its structural and optical properties. Full article

To address the issues of hydrophobicity, easy fouling, and limited application of polyvinylidene fluoride (PVDF) membranes in water treatment processes, this study prepared Cu-MnO₂/GO/PVDF catalytic membranes via the immersion precipitation phase inversion method. Graphene oxide (GO) was incorporated to facilitate the construction of good water channels, while copper-doped manganese dioxide (Cu-MnO₂) was added to enhance catalytic activity. The structure, morphology, and performance of the membranes were characterized comprehensively. Results showed that Cu-MnO₂ was well interspersed between GO sheets, thereby increasing membrane surface roughness, effective filtration area, and hydrophilicity. The best catalytic membrane CM-5 exhibited the highest pure water flux (1391.20 L·m⁻²·h⁻¹) and methyl blue (MBE) rejection rate (98.06%), and it also displayed excellent reusability and stability. EPR tests confirmed the generation of HO· and HOO· in the Fenton-like system, which mediated dye degradation. The Cu-MnO₂/GO/PVDF catalytic membrane demonstrated excellent hydrophilicity, antifouling properties, and catalytic efficiency, thus providing a viable solution for dye wastewater treatment. Full article

We establish a general, device-oriented procedure to extract absolute pump-band metrics from room-temperature UV–Vis (ultraviolet–visible) absorbance—including the absorption coefficient α(λ), per-active-ion cross-section ${\sigma }_{\mathrm{e}\mathrm{f}\mathrm{f}}\left(\lambda \right)$, the effective per-active-ion absorption cross section ${\sigma }_{\mathrm{e}\mathrm{f}\mathrm{f}}\left(\lambda \right)$ and derivative-based line-shape descriptors. As a representative case study, the procedure is applied to nanocrystalline Er³⁺/Ho³⁺:Y₃Ga₅O₁₂ over the 350–700 nm spectral range. After baseline correction and line-shape inspection assisted by the numerical second derivative of the absorbance, we extract conservative peak positions and the full width at half maximum across the visible 4f–4f manifolds. At the technologically relevant pump wavelengths near 406 nm (Er-addressing) and 473 nm (Ho-addressing) bands, resulting absorption coefficients are α = 0.313 ± 0.047 cm⁻¹ and α = 0.472 ± 0.071 cm⁻¹, respectively. The corresponding per-active-ion ${\sigma }_{\mathrm{e}\mathrm{f}\mathrm{f}}$ of (3.62 ± 0.54) × 10⁻²² cm² and (5.46 ± 0.82) × 10⁻²² cm², referenced to the measured optical path length L = 0.22 ± 0.03 mm (approximately 15% propagated relative uncertainty; explicit 1/L rescaling). Cross sections are reported per total active-ion density (Er³⁺ + Ho³⁺). The spectra exhibit Stark-type substructure only partially resolved at room temperature; the second derivative highlights hidden components, and we report quantitative descriptors (component count, mean spacing, curvature-weighted prominence, and pump detuning) that link line-shape structure to absolute pump response. These device-grade metrics enable rate-equation modelling (pump thresholds, detuning tolerance), optical design choices (path length, single/multi-pass or cavity coupling), and host-to-host benchmarking at 295 K. The procedure is general and applies to any rare-earth-doped material given an absorbance spectrum and path length. Full article

In the present study three composite materials based on iron in combination with bismuth, copper or lithium carbonates FeNO₃@Li₂CO₃ (SFL), FeNO₃@CuCO₃ (SFC), and FeNO₃@(BiO)₂CO₃ (SFB) were synthesized by coprecipitation. The purpose was to obtain materials that possess targeted adsorbent properties for the recovery of silver ions from aqueous solutions. After synthesis, to emphasize the adsorptive qualities of materials for the recovery of silver ions, the synthesized composite materials, as well as those doped with silver ions following the adsorption process (SFL-Ag, SFC-Ag, and SFB-Ag), were characterized and several adsorption-specific parameters were examined, including temperature, contact time, pH, adsorbent dose, and the initial concentration of silver ions in solution. Subsequently, the ideal adsorption conditions were determined to be as follows: pH > 4, contact time 60 min, temperature 298 K, and solid–liquid ratio (S–L) of 0.1 g of adsorbent to 25 mL of Ag (I) solution for all three materials. The Langmuir model properly fits the experimental equilibrium data of the adsorption process; however, the Ho–McKay model closely represents the adsorption kinetics. The maximum adsorption capacities of the materials, 19.7 mg Ag(I)/g for SFC, 19.3 mg Ag(I)/g for SFB, and 19.9 mg Ag(I)/g for SFL, are comparable. The adsorption mechanism is physical in nature, as evidenced by the activation energies of 1.6 kJ/mol for SFC, 4.15 kJ/mol for SFB, and 1.32 kJ/mol for SFL. The highest Ag(I) concentration used for doping all three materials in the study was 150 mg Ag(I)/L. The process is endothermic, spontaneous, and takes place at the interface between the adsorbent and the adsorbate, according to thermodynamic theory. Subsequently, the antimicrobial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans microorganisms was evaluated by rate of inhibition assessment. The SFC-Ag material showed a percentage of 100% inhibition with respect to the positive control for each microorganism. All synthetized materials have better efficiency as antifungal agents. Full article

The development of dielectric capacitors with high energy-storage density and ultrafast discharge capability is essential for next-generation pulsed power systems. In this work, (Pb, La, Ho, Zr, Ti)O₃ (PLZTH) ceramics were fabricated via medium-temperature sintering (950–1100 °C) combined with Ho³⁺ doping to systematically tailor their energy-storage properties. This processing strategy not only mitigates Pb volatilization but also enhances compatibility with base-metal electrodes such as Ni and Cu. In addition, Ho³⁺ ions exhibit amphoteric doping behavior, which contributes to the enhancement of relaxor characteristics and grain refinement. H4 ceramic delivers an outstanding recoverable energy-storage density (W_rec) of 0.91 J/cm³ and a high energy efficiency (η) of 87% under 216 kV/cm, along with a power density (P_D) of 28.8 MW/cm³ and an ultrafast discharge time (t_0.9) of only 4.97 ns at 180 kV/cm. This study not only proposes a viable route toward high-performance medium-temperature-sintered PLZT ceramics but also elucidates the effective mechanism of Ho³⁺ amphoteric doping in modulating the relaxor state and properties of perovskite-based ceramics. Full article

A pyrochlore-type crystal structure photocatalytic nanomaterial, Ho₂FeSbO₇, was successfully synthesized using a hydrothermal method. Additionally, a fluorite-structured Bi_0.5Yb_0.5O_1.5 was prepared via rare earth Yb doping. Finally, a novel Ho₂FeSbO₇/Bi_0.5Yb_0.5O_1.5 heterojunction photocatalyst (HBHP) was fabricated using a solvothermal method. The crystal structure, surface morphology, and physicochemical properties of the samples were characterized using XRD, a micro-Raman spectrometer, FT-IR, XPS, ultraviolet photoelectron spectroscopy (UPS), TEM, and SEM. The results showed that Ho₂FeSbO₇ possessed a pyrochlore-type cubic crystal structure (space group Fd-3m, No. 227), while Bi_0.5Yb_0.5O_1.5 featured a fluorite-type cubic structure (space group Fm-3m, No. 225). The results of the degradation experiment indicated that when HBHP, Ho₂FeSbO₇, or Bi_0.5Yb_0.5O_1.5 was employed as a photocatalytic nanomaterial, following 140 min of visible light irradiation, the removal efficiency of ciprofloxacin (CIP) reached 99.82%, 86.15%, or 73.86%, respectively. This finding strongly evidenced the remarkable superiority of HBHP in terms of photocatalytic performance. Compared to the individual catalyst Ho₂FeSbO₇, Bi_0.5Yb_0.5O_1.5, or N-doped TiO₂, the removal efficiency of CIP by HBHP was 1.16 times, 1.36 times, or 2.52 times higher than that by Ho₂FeSbO₇, Bi_0.5Yb_0.5O_1.5, or N-doped TiO₂, respectively. The radical trapping experiments indicated that in the CIP degradation process, the hydroxyl radical owned the strongest oxidation ability, followed by the superoxide anion and the photoinduced hole. These studies are of great significance for the degradation of antibiotics and environmental protection. Full article

This work examines the possibility of using a PbO₂-based electrode doped with the rare-earth metal holmium in the field of oxygen evolution and the development of an efficient method for the degradation of acetamiprid. Acetamiprid is a widely used insecticide and, as such, it very often reaches waterways, where it can cause many problems for wildlife and the environment. X-ray powder diffraction analysis, Raman spectroscopy, and energy-dispersive X-ray spectroscopy results confirmed the structure of Ti/SnO₂-Sb₂O₃/Ho-PbO₂, while the morphology of its surface was investigated by scanning electron microscopy with energy-dispersive X-ray spectroscopy. Ti/SnO₂-Sb₂O₃/Ho-PbO₂ showed good OER activity in alkaline media with a Tafel slope of 138 mV dec⁻¹. The Ti/SnO₂-Sb₂O₃/Ho-PbO₂ electrode shows very good efficiency in removing acetamiprid. By optimizing the degradation procedure, the following operating conditions were obtained: a current density of 20 mA cm⁻², a pH value of the supporting electrolyte (sodium sulfate) of 2, and a concentration of the supporting electrolyte of 0.035 M. After optimization, the maximum efficiency of removing acetamiprid (10 mg L⁻¹, 4.5 × 10⁻⁵ mol) from water was achieved, 96.8%, after only 90 min of treatment, which represents an efficiency of 1.125 mol cm⁻² of the electrode. Additionally, it was shown that the degradation efficiency is strictly related to the concentration of the treated substance. Full article

Co_0.95R_0.05Fe₂O₄ nanoparticles were synthesized using a sol-gel approach incorporating bio-based agents and were found to be single phases adopting a cubic Fd-3m structure. XPS shows the presence of Gd³⁺ and Ho³⁺ ions. The spin–orbit splitting of about 15.4 eV observed in Co 2p core-level spectra is an indication that Co is predominantly present as Co³⁺ state, while the satellite structures located at about 6 eV higher energies than the main lines confirm the existence of divalent Co in Co_0.95R_0.05Fe₂O₄. The positions of the Co 3s and Fe 3s main peaks obtained by curve fitting and the exchange splitting obtained values for Co 3s and Fe 3s levels point to the high Co³⁺/Co²⁺ and Fe³⁺/Fe²⁺ ratios in both samples. The saturation magnetizations are smaller for the doped samples compared to the pristine ones. For theoretical magnetization calculation, we have considered that the heavy rare earths are in octahedral sites and their magnetic moments are aligned antiparallelly with 3d transition magnetic moments. ZFC-FC curves shows that some nanoparticles remain superparamagnetic, while the rest are ferrimagnetic, ordered at room temperature, and showing interparticle interactions. The M_S/Ms ratio at room temperature is below 0.5, indicating the predominance of magnetostatic interactions. Full article

In this study, we investigate the presence of the Griffiths-like anomaly in the geometrically frustrated antiferromagnet ${\mathrm{HoBaCo}}_4$${\mathrm{O}}_{7+\delta }$ and globally its absence in ${\mathrm{ErBaCo}}_4$${\mathrm{O}}_{7+\delta }$, despite only small differences in the ionic radii, f-electron occupancy, and the corresponding crystal structures of the ${\mathrm{Ho}}^{3+}$ and ${\mathrm{Er}}^{3+}$-members. Previous studies have identified the Griffiths phase in the Dy-analog, ${\mathrm{DyBaCo}}_4$${\mathrm{O}}_{7+\delta }$, suggesting certain inherent features of this class of materials that regularly give rise to such anomalies. To explore the curious disappearance of such an anomalous feature in ${\mathrm{ErBaCo}}_4$${\mathrm{O}}_{7+\delta }$, we prepared a series of compounds with varying compositions ${\mathrm{Ho}}_{1-x}$${\mathrm{Er}}_x$${\mathrm{BaCo}}_4$${\mathrm{O}}_{7+\delta }$ ($0\le x\le 1$) and systematically studied the evolution of various physical properties as a function of Er-doping. Our experimental studies, including X-ray diffraction (XRD), magnetic, X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), heat capacity, and muon spin relaxation spectroscopy ($\mu$SR spectroscopy), revealed that while the Griffiths-like anomaly indeed disappears with doping at the macroscopic level, signatures of inhomogeneity are retained in ${\mathrm{ErBaCo}}_4$${\mathrm{O}}_{7+\delta }$ too, at least at the local level. Overall, our results highlight the significant role of ionic radius and local structural distortions in stabilizing the Griffiths phase in this class of systems. Full article

Co-doping at Ba and Ti sites with double rare-earth elements has proven an effective strategy for enhancing the dielectric properties of BaTiO₃ ceramics. Among intermediate-sized rare-earth ions, Tb and Ho exhibit amphoteric behavior, occupying both Ba and Ti sites. Investigating the site occupation, defect chemistry, and dielectric effects of Tb and Ho in BaTiO₃ is therefore valuable. In this work, Tb/Ho-co-doped BaTiO₃ ceramics with the composition (Ba_1−xTb_x)(Ti_1−xHo_x)O₃ (x = 0.01~0.10) were fabricated at 1400 °C via solid-state reaction, and their solid solubility and crystal structures are confirmed. Microstructure, dielectric properties, photoluminescence, and valence states of samples with a single phase were systematically studied. Both the lattice parameter a and unit cell volume increase with doping level. The ceramic with x = 0.02 meets the X5S dielectric specification. Ho and Tb ions both demonstrate amphoteric site occupancy: Ho exists solely as Ho³⁺ at both Ba and Ti sites, while Tb exhibits mixed valence states as Ba-site Tb³⁺ and Ti-site Tb⁴⁺. As the doping content increases, the concentration of Tb⁴⁺ at Ti sites decreases, and the quantity of Ba-site Ho³⁺ ions initially increases to a maximum before decreasing. Defect compensation mechanisms within the samples are also discussed. Full article

This study evaluated the relationship between the microstructure, photoluminescence, and photocatalytic properties of newly synthesized nanostructured phosphor materials. The combustion method was used to create samples of down-converting SrGd₂O₄ doped with Dy³⁺ ions (1, and 7 at%) and up-converting SrGd₂O₄ co-doped with varying quantities of Yb³⁺ ions (2, and 6 at%) and a constant quantity of Ho³⁺ ions (1 at%). Transmission electron microscopy (TEM) revealed the existence of porous agglomerated round-shaped particles, with the size around 150 nm, arranged in network-like structures. Energy dispersive X-ray spectroscopy (EDS) confirmed the presence of all structural elements and their homogeneous distribution throughout the particles. The presence of specific emission peaks associated with Dy³⁺ or Ho³⁺ dopant ions was demonstrated by luminescent measurement. The degradation processes of specific organic dyes (methylene blue for up-converters and rhodamine B for down-converters) under simulated sun irradiation were used to investigate photocatalytic activity. A reduction in dye concentration in aqueous solutions was measured using UV/Vis absorption spectroscopy. The results showed a successful dye breakdown rate after 4 h, and aliquots of the working solutions were obtained at precise intervals. Additionally, the results indicated that samples with the highest luminescence intensity exhibited superior photocatalytic activity, suggesting a significant promise for usage as multifunctional materials. Full article

This study employs the first-principles calculation method based on density functional theory to investigate and analyze the effects of doping various rare earthions on the optical properties of bismuth silicate (Bi₄Si₃O₁₂, BSO) crystals. The results indicate that the electronic structure variations of rare earth ions significantly influence the electronic structure and transition characteristics of BSO crystals, thereby altering their optical properties. Specifically, Tm³⁺ doping notably enhances the polarization capability and infrared responsiveness of BSO crystals, Ho³⁺ doping improves their absorption and scattering abilities in the visible light range, while Eu³⁺ doping enhances their ultraviolet absorption. Overall, Tm³⁺ doping and Ho³⁺ doping exhibit the most prominent effects on the optical performance of BSO crystals, providing theoretical guidance for designing and optimizing BSO crystals with specific optical properties. Full article