An ultra sensitive fluorescent nanosensor for detection of ionic copper Sibel Kacmaz a,b , Kadriye Ertekin c,f,⇑ , Deniz Mercan d , Ozlem Oter c , Engin Cetinkaya d , Erdal Celik e,f a Giresun University, Faculty of Engineering, Department of Food Engineering, 28200 Giresun, Turkey b University of Dokuz Eylul, The Graduate School of Natural and Applied Sciences, Department of Chemistry, 35160 Izmir, Turkey c University of Dokuz Eylul, Faculty of Sciences, Department of Chemistry, 35160 Izmir, Turkey d University of Ege, Faculty of Sciences, Department of Chemistry, 35100 Izmir, Turkey e University of Dokuz Eylul, Faculty of Engineering, Department of Metallurgical and Materials Engineering, 35160 Izmir, Turkey f University of Dokuz Eylul, Center for Fabrication and Application of Electronic Materials (EMUM), 35160 Izmir, Turkey highlights  The immobilized fluoroionophore DMK-7 was used for the first time for sensing of Cu 2+ .  The dye exhibited highly selective and sensitive response to Cu 2+ at picomolar level.  The sensing ability of the DMK-7 was tested both in thin film and nanofiber forms.  The nano-structured sensing agents exhibited lower detection limits with respect to thin films.  The long term stability of the exploited dye was longer than 8 months. graphical abstract article info Article history: Received 7 May 2014 Received in revised form 7 July 2014 Accepted 17 July 2014 Available online 27 July 2014 Keywords: Optical sensors Fluorescent probes Nano-scale sensor Cu (II) Copper Electrospinning abstract A stable and ultra sensitive nano-scale fluorescent chemo-sensor for trace amounts of Cu 2+ was proposed. The Cu 2+ selective fluoroionophore 2-{[(2-aminophenyl)imino]methyl}-4,6-di-tert-butylphenol (DMK-7) was encapsulated in polymeric ethyl cellulose. The sensing membranes were fabricated in form of nanof- ibers and thin films. When embedded in polymers, the exploited DMK-7 dye exhibited enhanced photo- physical characteristics in absorbance, Stoke’s shift, fluorescence quantum yield, and short and long-term photostability with respect to the solution phase. Sensing abilities of the nanofibers and thin films were tested by steady state and time resolved fluorescence spectroscopy. To our knowledge, this is the first attempt using the DMK-7-doped electrospun nanofibrous materials for copper sensing. The offered sen- sor displayed a sensitive response with a detection limit of 3.3  10 13 M for Cu 2+ ions over a wide con- centration range of 5.0  10 12 –5.0  10 5 . Additionally, exhibited high selectivity over convenient cations; Na + ,K + , Ca 2+ , Mg 2+ , NH 4 + and Ag + , Al 3+ , Ba 2+ , Co 2+ , Cr 3+ , Fe 3+ , Fe 2+ , Hg 2+ , Li + , Mn 2+ , Ni 2+ , Pb 2+ , Sn 2+ and Zn 2+ . Ó 2014 Elsevier B.V. All rights reserved. Introduction Selective, sensitive and correct recognition of ionic species has been an attractive working subject for scientists. Among them, Cu 2+ has probably been one of the most monitored species. Moni- toring of trace amounts of Cu 2+ becomes quite important especially for strict purity guidelines like medical industry, pharmaceutical applications, dialysis water, microelectronics and manufacturing of integrated circuit semiconductor chips. Up to now, various instrumental techniques have been exploited for the determina- tion of trace levels of the copper. The majority of the methods http://dx.doi.org/10.1016/j.saa.2014.07.056 1386-1425/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: University of Dokuz Eylul, Faculty of Sciences, Department of Chemistry, 35160 Izmir, Turkey. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 135 (2015) 551–559 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa