Nguyen Thanh Huong

Independent control of coercivity (H_C) and exchange bias (H_EB) in ferromagnetic/antiferromagnetic (FM/AFM) heterostructures is essential for optimizing perpendicular spintronic devices, including magnetic random-access memory (MRAM) and nanoscale magnetic sensors, yet remains challenging due to their shared interfacial origin. In this work, we demonstrate a systematic approach to decouple these properties in [Co/Pd] multilayers (MLs) exchange-coupled to FeMn by engineering the stacking sequence and antiferromagnetic layer thickness (t_FeMn). Two configurations—top-pinned [Co/Pd]/FeMn and bottom-pinned FeMn/[Co/Pd]—were fabricated using magnetron sputtering. Despite exhibiting similar fcc(111) texture, the two structures display markedly different magnetic responses. The bottom-pinned configuration promotes rotatable uncompensated spins, resulting in a significant enhancement of HC (up to 1440 Oe) with negligible HEB. In contrast, the top-pinned configuration stabilizes pinned uncompensated spins, leading to a pronounced perpendicular exchange bias (up to 188 Oe) with minimal impact on H_C. By varying t_FeMn, H_C and H_EB can be tuned independently over wide ranges. These results demonstrate that stacking-sequence-dependent interfacial spin configurations govern magnetic behavior rather than bulk structural differences, providing a practical and scalable strategy for designing high-stability reference layers and low-switching-energy free layers in advanced spintronic devices.

The increasing global industrial demands have led to water source contamination by hazardous wastes such as organic compounds, dyes, heavy metals, and oils. Consequently, wastewater treatment has become a paramount environmental challenge, requiring efficient, low-cost treatment materials with large-scale manufacturing capabilities. This paper presents a research on synthesizing expanded graphite (EG) materials from graphite intercalation compounds (GIC) using the induction heating method. The properties of the synthesized material have been evaluated through scanning electron microscopy (SEM), specific surface area measurements using the Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Additionally, experiments were conducted to evaluate its efficacy in removing dyes such as Methylene Blue (MB) and oils (Diesel Oil - DO) from wastewater. The study results indicate that the synthesized material can adsorb dyes almost completely (> 99 %) and that more than 50 g of diesel oil can be retained by just 1 g of the material. However, there is a difference in the adsorption of hydrophilic and hydrophobic compounds depending on the structure of the EG material. Furthermore, the utilization of the thermal shock synthesis method using an induction furnace demonstrates its capability to produce a large quantity of material at a low cost.

Tb3+-doped GdPO4·H2O phosphors were synthesized with wire-, rod-, and particle-like morphologies using a solvothermal method. This was achieved by varying the reaction solvent between diethylene glycol (DEG) and polyethylene glycol (PEG) of different molecular weights. The crystal structure, morphology, and photoluminescence (PL) properties were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and PL spectroscopy. The emission spectra showed the characteristic green luminescence of Tb³⁺ ions, with transition from the 5D4 → 7Fj (J = 6, 5, 4, 3) at 489, 543, 586, and 620 nm, respectively. Systematic analysis revealed a strong correlation between material morphology, crystal structure, and luminescence efficiency. The sample with a nanoparticle morphology, synthesized at 100 °C in a PEG 8000 medium, exhibited the highest PL intensity. It displayed a dominant green emission at 543 nm (5D4 → 7F5) and sharp, well-defined emission bands. These findings confirm that a solvent-mediated morphology control strategy is effective for optimizing the luminescence performance of GdPO4-based phosphors.

Plasmon-enhanced Gd ₂ O ₃ :Eu ³⁺ nanostructures demonstrate strong luminescence and synergistic antibacterial performance.

We present the synthesis of Er³⁺/ Yb³⁺ co-doped Gd₂O₃ nanospheres using the wet-chemical method followed by a synergistic step-by-step calcination process, a novel approach in the field. The nanospheres exhibited red color upconversion luminescence (UCL) after multi-step annealing at temperatures ranging from 650 °C to 1150 °C, achieving a fully spherical morphology. The diameter and surface morphology of the nanospheres were significantly altered by the annealing process, decreasing from 382.77 ± 1.72 nm with a smooth surface to 245.7 ± 1.31 nm with a rougher surface. The UCL intensity increased with the annealing temperature. The influence of Er³⁺/ Yb³⁺ co-doped Gd₂O₃ nanospheres, excited by a 975 nm laser, was investigated, and the decay time for UCL samples was analyzed. The luminescence peak at 1026 nm was attributed to the ⁴I_11/2 (Er³⁺) + ²F_7/2 (Yb³⁺) → ⁴I_15/2 (Er³⁺) + ²F_5/2 (Yb³⁺) transition/ or ²F_5/2 → ²F_7/2 of the Yb³⁺ ions within the Gd₂O₃ matrix. Furthermore, the UCL properties of Er³⁺/ Yb³⁺ co-doped Gd₂O₃ nanophosphors were explored to detect the NTERA-2 cancer cells. These findings suggest that the rare earth co-doped Gd₂O₃ nanospheres might hold significant potential for biomedicine and imaging diagnostics applications, sparking new interest and possibilities in these fields.

In this work, nano-selenium (NSe) with different shapes (wires, rods, and spherical particles) was synthesized by a wet chemical method. These synthesized products were characterized by x-ray powder diffraction (XRD) analysis, a field emission scanning electron microscope (FE-SEM) with an energy dispersive x-ray analyzer, and Raman spectroscopy. FE-SEM images revealed that nanowires with an average diameter of 30–50 nm and length of 3–5 µm, nanorods with lengths of 400–800 nm and diameters of about 20–50 nm, and spherical-shaped nanoparticles (NPs) with diameters ranging from 40 to 60 nm were successfully synthesized. The XRD and Raman analysis confirmed that all the produced NSe samples exhibited hexagonal single-phase crystalline structure with no impurity phase. All three NSe products (SeNWs, SeNRs, and SeNPs) with a concentration range of 25–150 mg/l were used to investigate the impact of shape and concentration on seed germination and seedling vigor of four different crop species, namely, green bean, okra, wheat, and radish. The results revealed that NSe at low concentrations (≤50 mg/l for SeNWs and ≤100 mg/l for SeNRs and SeNPs) can promote seed germination, plant growth, and development of all the studied crop species. However, NSe can adversely affect the growth of plants at higher concentrations (≥75 mg/l for SeNWs).

Rare earth photonic nanomaterials are increasingly prominently applied in various fields of biomedicine. Currently, there is greater focus on the investigation to control the size and shape of nanomaterials, including the nanospherical form, which allows for precise labeling by only one nanoparticle. This paper demonstrates, for the first time, the construction of a biological nanospherical probe (BNSP) Gd2O3: Yb3+, Er3+/Silica/NH/mAb^CD133 for diagnostic labeling of cancer stem cells (CSCs) NTERA-2. The BNSP was constructed using highly monodisperse spheres with around 200nm uniform size of Gd2O3: 7.6% Yb3+, 1.6% Er3+. They were functionalized by an amine group-contained shell coating and conjugated with CD133 monoclonal antibody. The functionalized nanosphere Gd2O3: Yb, Er/silica/NH2 showed strong upconversion luminescence in red color upon laser excitation in the near-infrared region at 975 nm. The Gd2O3: Yb3+, Er3+/silica/NH2 was carefully implemented to conjugate mAb^CD133 via a linker, glutaraldehyde, to obtain the predictable probe Gd2O3: Yb3+, Er3+/Silica/NH/mAb^CD133. Then, this BNSP was tested in vitro for its capacity to label NTERA-2 cancer stem cells. The efficient labeling based on the fluorescent immunoassay method was detected by incorporating a nanophotometer, Field Energy Scan Electron Microscopy (FESEM), and precisely determined by fluorescent microscopy. The study shows that the BNSP is highly efficient with targeting capacity and specificity in the labeling of cancer stem cells. These advanced results open up promising avenues for the development of precise imaging diagnostics in cancer cellular biomedicine, and beyond.

In this paper, the luminescent complex Eu(3-thenoyltrifluoroacetonate)₃ was integrated with Fe₃O₄ and gold (Au) nanoparticles to form a multifunctional nanocomposite, Fe₃O₄/Au/Eu(TTA)₃ (FOASET NC), for dual magnetic-photothermal therapy and biomedical imaging. Upon functionalization with amine-NH₂, the FOASET NC exhibits a small size of 60–70 nm and strong, sharp emission at λ_max = 614 nm, enhanced by surface plasmon resonance (SPR) of Au nanoparticles that provided an effective label for HT29 colorectal cancer cells by fluorescence microscopy imaging. In addition, a hyperthermia temperature (42–46 °C) was completely achieved by using these FOASET NCs in an aqueous solution with three heating modes for (i) Magnetic therapy (MT), (ii) Photothermal therapy (PT), and (iii) Dual magnetic-photothermal therapy (MPT). The heating efficiency was improved in the dual magnetic-photothermal heating mode.