Nofrijon Sofyan

Mg-doped ZnFe₂O₄ spinel ferrite nanoparticles (MgxZn1-xFe2O4, x = 0.1–0.3) were synthesized via a sago-starch-assisted sol–gel autocombustion method and evaluated for solar-driven photocatalytic degradation of ciprofloxacin and tetracycline antibiotics. Comprehensive characterization using XRD, FTIR, Raman spectroscopy, TGA, SEM-EDS, TEM, VSM, UV–Vis DRS, and BET confirmed the formation of single-phase spinel structures with tunable physicochemical properties. The materials exhibited superparamagnetic behavior with saturation magnetization values of 11.9–19.6 emu g⁻¹, enabling facile magnetic recovery. Optical analysis revealed visible-light absorption with band gap energies in the range of 1.45–1.67 eV. Morphological observations by SEM and TEM revealed relatively uniform nanoparticles ranging from 15 to 45 nm in size. Among the compositions, MgxZn1-xFe2O4 (x = 0.25) demonstrated superior photocatalytic performance, achieving about 85% degradation of ciprofloxacin and 70% degradation of tetracycline within 120 min under solar irradiation. The enhanced activity is attributed to the synergistic effects of reduced crystallite size, increased surface area, and improved charge separation, which facilitate the generation of reactive oxygen species. The integration of Mg substitution with a sago-starch-mediated green synthesis route offers an environmentally benign approach to producing efficient, magnetically recoverable photocatalysts. These findings highlight the potential of Mg-modified ZnFe2O4 for sustainable treatment of antibiotic-contaminated wastewater.

The synthesis of high-purity lepidocrocite-type titanate nanotubes from natural ilmenite minerals remains challenging due to the presence of iron impurities and the limited understanding of their structural stability during thermal treatment. This study presents a controlled purification and hydrothermal synthesis route for producing high-purity lepidocrocite-type titanate nanotubes from ilmenite-derived titanium dioxide (TiO₂) nanoparticles. Titanium oxosulfate (TiOSO₄) leachate obtained from the sulfate process was prepared via ethylenediaminetetraacetic acid (EDTA)-assisted purification, yielding TiO₂ nanoparticles with a purity of 99%, which were subsequently converted into titanate nanotubes by hydrothermal treatment. Structural characterization confirmed that the nanotubes retained their multilayered lepidocrocite-type titanate (H₂Ti₃O₇) structure after calcination up to 300°C while exhibiting improved crystallinity and a well-defined tubular morphology. The optimized sample (PF300) exhibited the highest specific surface area (256.9 m²g⁻¹) and pore volume (0.54 cm³g⁻¹), together with a direct band gap of 3.29 eV. Photocatalytic performance was evaluated through the degradation of methylene blue (MB), achieving removal efficiencies of 98% and 96% under ultraviolet and visible light irradiation, respectively. The outstanding performance originated from the synergistic effect of adsorption and photocatalysis, with preserved tubular morphology, a layered lepidocrocite structure, a high specific surface area, favorable optical properties, and efficient charge separation. These findings demonstrate that EDTA-assisted purification combined with controlled thermal treatment provides an effective strategy for producing high-performance lepidocrocite-type titanate nanotubes from natural ilmenite, with promising potential for solar energy-harvesting applications.

The Fe‐Mn‐Si‐Cr‐Ni alloy is a shape memory alloy with potential for civil infrastructure applications, which can be used for building reinforcement and seismic dampers due to its shape memory effect (SME) and pseudoelasticity (PE) capabilities. The Fe‐Mn‐Si properties could be optimized by the addition of precipitate‐formers such as carbon combined with several series of training. This work was conducted using a hot rolling process at a temperature of 1273 K to obtain a 60% reduction, followed by a solution treatment process at a temperature of 1373 K for 1 h and aging at 973 K for 30 min. A temperature of 573 K and 6% deformation were used in training, with repetitive loading and heating until five cycles were completed. The research results showed that training with 6% pre‐strain and heating at 573 K has been proven to boost the SME value of FeMnSiCrNi alloy. However, the most effective training cycle on the alloy happened in the third cycle, resulting in excellent SME. The strain recovery capabilities of Alloy‐3 improved by 12% in the third training cycle compared to Alloy‐3 in the first training cycle and by 32% compared to Alloy‐1 in the same training level. Despite the positive impact, training cycles of up to five times reduce the alloy's strain recovery properties and increase strain hardening. Alloy‐3 exhibits severe strain recovery deterioration due to saturation of non‐reversible martensite formation generated by significant deformation strain.

This work aims to examine the properties of titanium dioxide nanoparticles (TiO₂ NPs) synthesized through a sustainable, chelating-assisted green process using mangosteen (Garcinia mangostana L.) pericarp extracts for use as a semiconductor layer in dye-sensitized solar cells (DSSCs). X-ray diffraction (XRD) characterization revealed that the TiO₂ NPs have a tetragonal crystalline structure and are pure anatase. The optical characteristics examined using ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS) showed a reduced bandgap energy, from 3.22 to 3.20 eV, with the use of mangosteen pericarp extract. The same trend is observed with the use of chelating agent concentration, decreasing from 3.20 to 3.10 eV at 30%, then increasing slightly to 3.14 eV at 50%. The TiO₂ NPs were further used as a semiconductor layer in a DSSC device sensitized with the commercial dye N719 and a natural dye derived from Malabar spinach (Basella rubra L.) fruit extract. The highest efficiency of 2.34% was achieved with a DSSC device fabricated from green-synthesized TiO₂ NPs using mangosteen pericarp extracted with 50% acetylacetone (AcAc) and sensitized with N719, slightly lower than that of commercial TiO₂ P25 (2.65%). The efficiencies of the same materials sensitized with natural dyes from Malabar spinach fruit extract are 0.69% and 1.01%, respectively. These results demonstrate the potential of using mangosteen pericarp waste and natural dyes for the sustainable, cost-effective fabrication of DSSCs.