Contents lists available at ScienceDirect Journal of Luminescence journal homepage: www.elsevier.com/locate/jlumin 2-hydroxy-5-methylisophthalaldehyde based fluorescent-colorimetric chemosensor for dual detection of Zn 2+ and Cu 2+ with high sensitivity and application in live cell imaging Jayanta Mandal a , Pravat Ghorai a , Kunal Pal b , Parimal Karmakar b , Amrita Saha a, ⁎ a Department of Chemistry, Jadavpur University, Kolkata 700032, India b Department of Life Science and Biotechnology, Jadavpur University, Kolkata 700032, India ARTICLE INFO Keywords: Schiff base Zn 2+ and Cu 2+ sensor Spectroscopic analysis Cell imaging DFT calculations ABSTRACT A 2-hydroxy-5-methylisophthalaldehyde (HMP) based Schiff-base ligand (HL) was successfully developed as a fluorescent and colorimetric chemosensor for dual detection of Zn 2+ and Cu 2+ ions in HEPES buffer medium (H 2 O:Methanol = 9:1 (v/v), pH= 7.4). Interestingly, in presence of Zn 2+ around 16 times increment in fluor- escence intensity and in presence of Cu 2+ ~ 174 times decrease in fluorescence intensity has been observed. The 1:2 binding modes for both HL-Zn 2+ /Cu 2+ complexes are proved by fluorescence measurements, ESI-MS ana- lysis and DFT-Calculations. The reversibility and regeneration process of HL are also established using Na 2 EDTA. It has been observed that Chemosensor HL exhibits a rapid change in fluorescence intensity within pH range 6–8 against Zn 2+ and Cu 2+ ions. Low detection limit was found to be 1.059 × 10 -9 (M) and 3.53 × 10 -9 (M) for Zn 2+ and Cu 2+ ions respectively. These values also suggest that the chemosensor HL has great potential to detect Zn 2+ and Cu 2+ ions in environmental and biological studies. 1. Introduction Chemosensors that can selectively detect the presence of both en- vironmentally and biologically important metal ions through the naked eye and optical responses has received significant attention [1]. En- vironmentally and biologically significant metal ions could be detected using different traditional analytical techniques such as voltammetric methods, inductively coupled plasma mass spectrometry (ICP-MS), ion selective electrodes and atomic absorption/emission spectrometry. In comparison to above techniques colorimetric and fluorescent methods are more advantageous due to their ease of measurement, excellent selectivity, high sensitivity, simplicity and rapid response time [2–7]. Fluorescent-sensing mechanisms that have been extensively in- vestigated are photo induced electron transfer (PET), the rigidity effect, fluorescence resonance energy transfer (FRET), excimer/exciplex for- mation/ extinction, photo-induced charge transfer (PCT), and less fre- quently, excited-state proton transfer (ESPT). Colorimetric method is extensively used mainly naked-eye detection of the element without any use of a spectroscopic instrument [8–11]. Among various cations commonly present in our human body, Zn 2+ and Cu 2+ are the second and third most abundant transition element found after iron(III). Both metal ions play critical roles in biology, and they most often present as cofactors in diverse enzymes; however, improper regulation of their storage is also connected to serious disorders. The average zinc and copper ion concentrations required for human growth and development are in the order of 15 mg/L and 0.1 mg/L, respectively. Excess copper is toxic and environmental pollutant. However, its deficiency or over-load is associated with a series of disorders such as anemia, liver damage in infants, Wilson disease, Parkinson's disease, Alzheimer's disease, Menkes syndrome etc [12–14]. Similarly, zinc(II) deficiency is asso- ciated with growth retardation, neurological disorder, such as Par- kinson and Alzheimer's diseases, eye lesion, skin problems and different immunological defense related decrease [15,16]. Therefore, the mon- itoring and imaging of these elements are important for biological re- search as well as clinical diagnosis. Regarding detection of Zn 2+ ion the greatest challenge is to discriminate Zn 2+ from Cd 2+ [17]. Both are present in the same group of the periodic table with similar photo- physical properties. A large number of Zn 2+ and Cu 2+ detecting che- mosensors are reported in literature, still there is a great need to de- velop simple and effective chemosensors for their dual detection. The HMP framework has been an ideal candidate for the construc- tion of different type fluorescent chemosensors (chart S1). A careful literature survey of chemosensors based on isophthalaldehyde and its derivatives reveal that most of the chemosensors selectively detect only https://doi.org/10.1016/j.jlumin.2018.08.080 Received 2 February 2018; Received in revised form 19 June 2018; Accepted 26 August 2018 ⁎ Corresponding author. E-mail address: amritasahachemju@gmail.com (A. Saha). Journal of Luminescence 205 (2019) 14–22 Available online 28 August 2018 0022-2313/ © 2018 Elsevier B.V. All rights reserved. T