Full Length Article Aggregation induced emission enhancement (AIEE) of fluorenyl appended Schiff base : A turn on fluorescent probe for Al 3 þ , and its photovoltaic effect Uttam Panda a , Suman Roy a , Debashis Mallick a,1 , Animesh Layek b , Partha Pratim Ray b , Chittaranjan Sinha a,n a Department of Chemistry, Jadavpur University, Kolkata 700032, India b Department of Physics, Jadavpur University, Kolkata 700032, India article info Article history: Received 1 January 2016 Received in revised form 1 July 2016 Accepted 2 July 2016 Available online 7 July 2016 Keywords: Fluorenyl Schiff base Al 3 þ -selective fluorophore AIEE DSSC fabrication DFT computation abstract Fluorenyl-diformyl phenol Schiff (HL) base is spectroscopically characterized and demonstrates aggre- gation induced emission enhancement (AIEE) upon addition of water to THF solution. Maximum intensity is observed at 90% of water addition at 570 nm. Al 3 þ induced turn-on fluorescence enhance- ment is observed at 600 nm and the limit of optical detection (LOD) is 6.22x10 9 M. Isolation of Al(III)- complex and mass spectral measurement shows the formation of phenoxo-bridged dinuclear complex. Applicability for DSSC device fabrication of probe shows photovoltaic efficiency 0.021%. DFT computation of optimized geometry of HL has been used to explain the spectral and photovoltaic activity. & 2016 Published by Elsevier B.V. 1. Introduction Fluorophores are described according to their absorption and fluorescence properties, including the spectral profiles, wave- lengths of maximum absorbance and emission, and the fluores- cence intensity of the emitted light. One of the parameters to monitor the intensity of emission is the concentration of the fluorophore. With increasing concentration from very dilute solution the emission intensity commonly increases, but the emission of polyaromatic hydrocarbon (PAH), in general, shows dramatic decrease in intensity after a limiting concentration which is commonly known as aggregation-caused quenching (ACQ) due to the strong intermolecular stacking interactions [1,2]. However, Tang [3] and Park [4] in 2001 and 2002, respectively, showed some anti-ACQ materials and were termed aggregation-induced emis- sion (AIE) and aggregation-induced emission enhancement (AIEE) materials. Since then, AIE and AIEE materials have attracted con- siderable attention [5]. PAHs are π-delocalized planar rigid motifs to demonstrate π—π aggregation and have been suitable for per- forming aggregation induced emission [6–8]. Fluorenyl attached π-conjugated molecules show several advantageous properties such as light-emitting diodes (LEDs), organic lasers, organic thin- film transistors (OTFTs), nonlinear optical (NLO) materials, optoe- lectronic devices etc [9,10]. Fluorene and its derivatives are good contenders to perform aggregation induced emission enhance- ment and are effective probe for ion induced turn-on fluorescence enhancing agent. π-Delocalized molecules show good electro- chemical activity, high quantum yields in emission spectral studies [11,12] and have wide applications in organic light emitting devices (OLEDs) [13]. In this work, we have synthesized fluorenyl appended diformylphenol Schiff base (HL) and has been char- acterized by spectroscopic data. The probe, HL, shows AIEE at the near red region in presence of water and exhibits very high fluorescence sensor activity to Al 3 þ in the presence of large number of other cations such as K þ , Mg 2 þ , Ba 2 þ , Zn 2 þ , Cd 2 þ , Co 2 þ , Pb 2 þ , Ni 2 þ , Fe 2 þ while Hg 2 þ and Cu 2 þ show minor sen- sitivity in THF–MeOH (1:1, v/v) mixture. Aluminum is neurotoxic, water pollutant and causes Alzhei- mer’s [14] and Parkinson’s [15] diseases, and hampers protein transportation, softening of bone, anemia in living beings. It is the third most abundant metal in the earth’s crust (8% of its mass); resists corrosion and is a useful structural component of electronic and electrical gadgets, building materials, packaging stuff etc. So, designing of high sensitive multi-signaling chemosensor for Al 3 þ Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jlumin Journal of Luminescence http://dx.doi.org/10.1016/j.jlumin.2016.07.008 0022-2313/& 2016 Published by Elsevier B.V. n Corresponding author. E-mail address: c_r_sinha@yahoo.com (C. Sinha). 1 Present address: Mrinalini Datta Mahavidyalaya, Birati, Kolkata 700051. Journal of Luminescence 181 (2017) 56–62