Nevşehir Hacı Bektaş Veli University (Turkish: Nevşehir Hacı Bektaş Üniversitesi), commonly referred to as Nevşehir University, is a public institute of higher education established in 2007 located in Nevşehir, Turkey.
The biogenic synthesis of silver nanoparticles (AgNPs) using microalgae provides a sustainable alternative to conventional physicochemical methods. In this study, AgNPs were synthesized from the cell-free supernatant of the freshwater microalga Mychonastes sp. B1 and characterized by ultraviolet–visible spectroscopy (UV–Vis), transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), and field-emission scanning electron microscopy with energy-dispersive X-ray spectroscopy (FE-SEM/EDS). The nanoparticles were predominantly spherical (15–55 nm), highly stable (ζ = − 42.8 mV), and appeared to be capped by extracellular polymeric substances. The biogenic AgNPs (GS-AgNPs) exhibited potent antibacterial activity, with minimum inhibitory concentrations (MICs) of 2.0 µg/mL against Staphylococcus aureus and 2.5 µg/mL against Pseudomonas aeruginosa, and significantly (p < 0.05) inhibited biofilm formation. Fibroblast viability remained at or above 80
Reversible hydrogen storage on single-site platforms requires interactions strong enough to offset the gas-to-adsorbate entropy penalty, yet weak enough to avoid H2 activation. Here we investigate a scandium metalloporphyrin (Sc-MP) as a model single-site adsorbent for multi-H2 loading (n = 1-20) using dispersion-corrected DFT (omega B97X-D/def2-TZVP) combined with a van't Hoff thermodynamic analysis. Across all coverages, the optimized geometries show strictly molecular adsorption: H-H bond lengths remain near the gas-phase value (0.74-0.76 & Aring;), the proximal Sc & sdot;& sdot;& sdot;H2 contact is essentially load-invariant (2.33-2.50 & Aring;), and a distal shell with Sc & sdot;& sdot;& sdot;H2 >= 5 & Aring; emerges beyond n = 9, evidencing a compact first shell plus a weakly coupled second shell. The average adsorption energy per H2 decreases from-0.157 eV (n = 1) to-0.012 eV (n = 20), while the adsorption enthalpy |Delta H| weakens from 17.6 to 2.2 kJ mol-1 and Delta G(298 K, 1 bar) remains positive. Entropies extracted from Delta H/Delta G (-95 to-76 J mol-1 K-1) feed a van't Hoff treatment that yields a quantitative T-p map: at 77 K and 1-10 bar, moderate reversible loadings (upper-bound n = 4-6) are thermodynamically favored, whereas at 150 K only n = 1 is stable. Electronic-structure signatures, an essentially constant HOMO-LUMO gap (3.95-3.97 eV), modest charge redistribution on Sc (+1.16 -> +0.40 |e|), and PDOS with weak H-s intensity and no sigma*(H2) band, corroborate a polarization-dominated, weak-Kubas regime. Sc-MP thus provides a cluster-resistant single-site scaffold that supports reversible cryogenic storage (up to 10.24 wt% H2-only) and suggests concrete design levers: modest field tuning to strengthen early adsorption toward the 15-20 kJ mol-1 window and reticulation into porphyrinic frameworks to increase site density while preserving single-site character.
Designing molecular motifs that can bind hydrogen strongly enough for uptake yet weakly enough for deliverable release remains a central challenge for adsorptive storage. Here, we use dispersion-corrected density functional theory to map the complete hydrogen-loading pathway of an iron porphyrin (Fe-MP, Fe metalloporphyrin) scaffold from n = 1 to 20 H2, connecting optimized configurations to adsorption energetics, thermodynamics and electronic-structure fingerprints. A clear hierarchy of adsorption environments emerges: the first H2 binds at the Fe center with a short Fe⋯H2 contact and an elongated H-H bond (1.65 Å and 0.80 Å, respectively), while subsequent H2 molecules populate progressively weaker sites surrounding the macrocycle. This transition is reflected in thermodynamics, with the mean adsorption energy collapsing from -0.47 eV per H2 at n = 1 to -0.03 eV per H2 at n = 20, accompanied by a marked reduction in desorption temperature from 599 K to 42 K. Despite the increase in gravimetric capacity to an upper bound of 9.97 wt% at full loading, the high-coverage reservoir is therefore intrinsically weakly bound and most relevant under pressure-assisted and/or cryogenic conditions. Charge analysis and projected density of states reveal progressive polarization without disruptive changes to the host electronic backbone, with an essentially invariant frontier gap (5.88-5.93 eV) across loading. Real-space interaction fingerprints from RDG-sign(λ2)ρ maps confirm a shift from localized attractive contributions at low coverage to dispersive confinement and steric crowding at high coverage. Together, these results separate capacity from usability in a chemically transparent adsorbent and provide a transferable design rule for computational materials discovery: high uptake must be accompanied by the multiplication of intermediate-strength binding motifs to move the storage manifold beyond a purely dispersion-dominated outer shell.
In this study, seven alkali-activated mortar mixtures were produced using waste andesite dust (WAD), fly ash (FA), and calcium aluminate cement (CAC). All mortar specimens were stored under ambient conditions of 20 ± 2 °C and 50 ± 10% relative humidity until testing. Flexural and compressive strengths were evaluated at curing ages of 7, 28, and 56 days. A comprehensive microstructural characterization of selected mortars was performed through phase analysis (XRD), morphological and chemical investigations (SEM/EDX/mapping), and examination of the three-dimensional pore structure (micro-CT). Additionally, a Life Cycle Assessment (LCA) was conducted for all mortar scenarios using 1 m3 of mortar as the functional unit. The mixture containing 66.6% WAD and 33.3% CAC exhibited the highest compressive strength among all formulations, reaching 35.5 MPa after 56 days of ambient curing. Micro-CT analyses revealed that this mixture also possessed the lowest porosity. The incorporation of CAC led to the formation of additional crystalline phases, such as sodium anorthite. Due to its low Ca content, WAD primarily produced an N-A-S-H gel-dominated matrix, whereas hybrid mixtures also developed C-A-S-H gel. Furthermore, FESEM and EDX mapping confirmed that the addition of CAC resulted in a denser and more compact microstructure, attributable to the increased concentration of Ca ions, which directly contributed to enhanced mechanical performance. Although CAC-containing mixtures showed improved strength and microstructural density under ambient curing, their environmental impacts were higher; in contrast, the WAD-based mixture exhibited the lowest environmental footprint.
