Yazar "Torres, Jorge H." seçeneğine göre listele

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    Öğe
    BPEI-Based N-Doped Carbon Dots with Sensitive and Selective Cu2+ Ion-Sensing Ability
    (Mdpi, 2025) Demirci, Sahin; Torres, Jorge H.; Sahiner, Nurettin
    In this research, we examined the potential sensor characteristics of branched polyethyleneimine (BPEI)-derived carbon dots (CDs) synthesized using BPEI as a nitrogen source and citric acid (CA) as a carbon source, specifically for the recognition of various metal ions. Among the BPEI CDs produced with different amounts of BPEI to CA BPEI:CA ratios of 0.5:1, 1:1, and 2:1 w/w, named as BPEI0.5 CD, BPEI1 CD, and BPEI2 CD, respectively. The BPEI0.5 CD, which contains the least BPEI, exhibited the highest fluorescence intensity: 50,300 a.u. in a 0.6 mg/mL solution were recorded as lambda(em): 420 nm at lambda(ex): 360 nm and 600 V PMT voltage with 5 nm of slit width for both excitation and emission. We investigated the fluorescence variations in BPEI CD-based CDs in 2 mL solutions containing Cd2+, Co2+, Cu2+, Ni2+, and Pb2+ metal ions at various concentrations. Amongst these metal ions, the most pronounced sensitivity was noted for Cu2+ ions with a limit of detection (LOD) value of 0.39 ppm. For BPEI CDs created with BPEI:CA ratios of 0.5:1, 1:1, and 2:1 w/w, the sensitivity to Cu2+ ions increased with a higher BPEI ratio, with a LOD value of 0.30 ppm recorded for BPEI2 CDs. Moreover, Cu2+ ion solutions were prepared from various salts, including chloride, acetate, nitrate, and sulfate; aside from some fluorescence variation observed for BPEI0.5 CDs, no significant difference in BPEI CD fluorescence change was observed with the use of the various salt solutions of Cu2+ ion. In quenching experiments conducted on mixtures of Cd2+, Co2+, Cu2+, Ni2+, and Pb2+ metal ions with Cu2+, it was noted that BPEI CDs displayed selectivity for Cu2+ ions. Furthermore, the structures of BPEI CDs have been effectively utilized in real water samples, such as tap water and seawater, demonstrating a quenching capability of over 65% in the presence of 50 ppm Cu2+ ions.
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    Öğe
    Polyethyleneimine-Modified Piezoelectric Barium Titanate of Various Sizes Reveals Improved Antibacterial Properties
    (Wiley, 2026) Sahiner, Nurettin; Demirci, Sahin; Lako, Alba; Torres, Jorge H.; Suner, Selin S.; Sahiner, Mehtap
    The piezoelectric materials, barium titanates (BaTiO3) in various sizes 50, 200, and 500 nm, were modified with polyethyleneimine (PEI) as PEI@BaTiO3 to improve antibacterial activities. The realization of PEI modification was confirmed with the peaks appeared on the Fourier transform infrared (FTIR) spectrum of BaTiO3 nanoparticles similar to 1650 cm-1, which are assigned to N-H stretching vibrations. The isoelectric points of BaTiO3 nanoparticles increased to about pH 10 after PEI modification, which were pH 3-4 range for pristine BaTiO3 nanoparticles. BaTiO3 nanoparticles below 200 nm showed antibacterial activity against gram-negative bacteria with 25 mg/mL minimum inhibition concentration (MIC) value but determined not effectively against gram-positive pathogens. However, positively charged PEI@BaTiO3 particles render high antibacterial potency on wide range of bacteria with almost four-fold lower MIC values than pristine BaTiO3 nanoparticles. Safe concentration of BaTiO3 nanoparticles on L929 fibroblast cells was found at 100 mu g/mL with more than 90% cell viability. Cytotoxicity was slightly decreased for PEI@BaTiO3 particles, and 50 mu g/mL concentration of PEI@BaTiO3 particles could be used in vivo applications without any significant toxicity. The piezoelectric effect of pristine BaTiO3 generated a higher voltage for 50 nm particles compared to the larger particles. Also, PEI@BaTiO3 generated voltages, somewhat attenuated and rapidly decayed in time, showed high consistency.