Gd(III)-Doped Boehmite Nanoparticle: An Emergent Material for the Fluorescent Sensing of Cr(VI) in Wastewater and Live Cells Shubham Roy, † Kunal Pal, ‡ Souravi Bardhan, † Shilpa Maity, † Dipak Kr. Chanda, § Saheli Ghosh, † Parimal Karmakar, ‡ and Sukhen Das* ,† † Department of Physics, ‡ Department of Life Science and Biotechnology, and § School of Materials Science and Nano Technology, Jadavpur University, Kolkata 700032, India * S Supporting Information ABSTRACT: This article reports the effect of Gd(III) doping on the structure, microstructure, and optical properties of boehmite nanoparticles. The bright-blue fluorescence along with a long lifetime makes our material an efficient candidate for optical applications. Our material particularly targets and eliminates hexavalent chromium ions (Cr(VI)) from aqueous media, which turns it into a multifunctional fluorescent nanosensor (MFNS). The development of an efficient hexavalent chromium ion (Cr(VI)) sensor to detect and quantify Cr(VI) ions is still a serious issue worldwide. Thus, this work will be very beneficial for various environmental applications. No such work has been reported so far which includes cost-effective and biocompatible boehmite nanoparticles in this field. Detailed synthesis and characterization procedures for the MFNS have been incorporated here. The biocompatibility of the MFNS has also been studied rigorously by performing cell survivability assay (MTT) and cellular morphology assessments. Our extensive research confirmed that the “turn-off” sensing mechanism of this sensor material is based on a collisional quenching model which initiates the photoinduced electron transfer (PET) process. High selectivity and sensitivity (∼1.05 × 10 -5 M) of the MFNS toward hexavalent chromium ions even in real life wastewater samples have been confirmed, which makes this fluorescent probe a potential candidate for new age imaging and sensing technologies. 1. INTRODUCTION The development of new-generation fluorescent sensors is currently of great research interest because they play a crucial role in detecting and quantifying various infections and diseases in biological systems. 1,2 Sometimes, they can locate and entrap an infection on the cellular level. 3 Not only biological systems but also these sensors can provide important information regarding any type of chemical contamination by modulating its fluorescence level. 4,5 Researchers and scientists are working to enhance the limit of detection (LOD) and the fluorescence properties of these sensors. Thus, the fabrication of biocompatible, efficient fluorosensors is an emerging research topic. Recent studies on hazardous ion sensors such as heavy metal ions (Hg(II), Cd(II), Cr(III), etc.) 6-8 and toxic anions (nitrate, dichromate, etc.) 9,10 dominate the studies on all other fluorosensors because of their huge applicability and excessive demand. Moreover, various diseases, such as congestive heart failure, 11 liver infarction, 12 and lung cancer, 13 can occur in the presence of such toxic ions. Some essential metal ions, including Fe 2+ , Cu 2+ , Mn 2+ , and Co 2+ , can also be toxic at higher doses. 14-17 In addition, other heavy metal ions, such as Hg 2+ , Cd 2+ , Pb 2+ , and As 3+ , are extremely toxic to humans and aquatic species even at lower concentrations, and the bioaccumulation of these metal ions can culminate in severe health hazards. 18-21 Hexavalent chromium (Cr(VI)) is a well-known carcino- gen 13 that is rapidly spreading as a result of its wide applications in leather tanning, metallurgy, chromium electro- plating, and pigment production. 22,23 Because of its enor- mously harmful nature to human health and the environment, its detection and segregation from water streams have become immensely challenging. 11-13 Apart from these, the accumu- lation of Cr(VI) in aquatic living varieties can cause biomagnifications. 24 Therefore, developing selective and sensitive methods to detect and remove Cr(VI) ions for environmental monitoring, medical diagnostics, and food safety is of considerable importance. We have synthesized a novel material, Gd(III)-doped boehmite nanoparticles, which has not been reported previously to the best of our knowledge. Thus, proper characterization has been done along with microstructural analysis by using the Rietveld refinement method to under- stand the effect of Gd doping into the boehmite matrix. 25,26 Interestingly, gadolinium incorporation enhances the optical Received: February 13, 2019 Article pubs.acs.org/IC Cite This: Inorg. Chem. XXXX, XXX, XXX-XXX © XXXX American Chemical Society A DOI: 10.1021/acs.inorgchem.9b00425 Inorg. Chem. XXXX, XXX, XXX-XXX Downloaded by UNIV OF SOUTHERN INDIANA at 17:30:23:223 on June 18, 2019 from https://pubs.acs.org/doi/10.1021/acs.inorgchem.9b00425.