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    Exploiting stokes and anti-stokes type emission profiles of aptamer-functionalized luminescent nanoprobes for multiplex sensing applications
    (Wiley-VCH Verlag Gmbh, 2018) Yüce, Meral; Kurt, Hasan; Hussain, Babar; Ow-Yang, Cleva W.; Budak, Hikmet
    Multiplex biosensing of four types of bacterial food pathogens in one pot is described. Stokes and anti-Stokes type photoluminescence (PL) of two quantum dots (QD) and two upconverting nanoparticles (UCNP) were utilised for realisation of the multiplex detection. The biosensing system was composed of aptamer-functionalized QD and UCNP nanoprobes that were conjugated with partially complementary DNA-modified magnetic beads for separation. PL signals of the conjugates were collected before and after incubation with target pathogens in one pot through the sequential excitations at 335nm for QD probes and 980nm for UCNP probes. The limit of detection values achieved were 28, 15, 12 and 25 cfu center dot mL(-1) for Listeria monocytogenes, Staphylococcus aureus, Salmonella typhimurium and Pseudomonas aeruginosa, respectively. Efforts for extending the multiplex detection up to five pathogens were also presented even though the PL signal cross-talk of a third QD nanoprobe hindered the detection. This work empowers co-deployment of QDs and UCNPs and paves the way for future studies in multiplex sensing, labelling, and bioimaging fields.
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    Oxide glass formers extending persistent luminescence in Eu and Dy co-doped strontium aluminates
    (Elsevier B.V., 2023) Coşgun Ergene, Arzu; Khabbaz Abkenar, Sirous; Şenol Güngör, Ayça; Günay, Ece; Kurt, Hasan; Topçu, Gökhan; Ow-Yang, Cleva W.
    Recent work has shown that the incorporation of electrically charged, non-bridging oxygen (NBO) species into Eu and Dy co-doped Sr4Al14O25 (S4A7ED) crystal structure, in the form of BØ2O?, induces the clustering of divalent Eu and trivalent Dy, which is manifested as persistent luminescence (PersiL). Because other ceramic compounds exhibiting persistent luminescence also contain Si, P, and Zr, we evaluated other oxide glass forming cations—Si, P, Zr and V—for extending PersiL in S4A7ED. To understand the structural changes that these cations imparted to the atomic arrangements inside the S4A7ED crystal structure, we applied FTIR and micro-Raman spectroscopy to analyze the impact of charged NBOs. Raman shifts were revealed in Si-doped S4A7ED exhibiting PersiL at 1077 cm?1, corresponding to vibrations involving SiO4 tetrahedra with 2 bridging oxygens (BOs) and 2 NBOs and at 1107 cm?1, corresponding to vibrations involving SiO4 tetrahedra with 3 BOs and 1 NBOs. Raman shifts were also observed in P-doped S4A7ED exhibiting PersiL at 1070 cm?1, corresponding to PO4 tetrahedra with 1 BO and 3 NBOs, and at 700 cm?1, corresponding to PO4 tetrahedra with 2 BOs and 2 NBOs. These results suggest that PersiL extension in S4A7ED compounds, Pechini-processed with oxides of Si, P, Zr, and V, is correlated to structural changes from the incorporation of polyanions with NBOs, although the presence of a BO in the cation polyhedra is also essential.