1278 ISSN 1061-9348, Journal of Analytical Chemistry, 2020, Vol. 75, No. 10, pp. 1278–1284. © Pleiades Publishing, Ltd., 2020. Naphthoquinone-Functionalized Nanoporous Silica: Synthesis, Characterization and Application for Fluorescent Sensing of Dicromate Fatemeh Silakhori a , Alireza Badiei a, b, *, and Ghodsi Mohammadi Ziarani c a School of Chemistry, College of Science, University of Tehran, Tehran, Iran b Nanobiomedicine Center of Excellence, Nanoscience and Nanotechnology Research Center, University of Tehran, Tehran, Iran c Department of Chemistry, Faculty of Science, Alzahra University, Tehran, Iran *e-mail: abadiei@khayam.ut.ac.ir Received January 27, 2018; revised October 14, 2018; accepted March 17, 2020 Abstract—A naphthoquinone-functionalized hybrid organic-inorganic silica-based fluorescent sensor was designed, synthesized and characterized by X-ray diffraction, N 2 adsorption-desorption, thermogravimetric and infrared spectroscopy analysis. Fluorescence properties of the prepared sensor were investigated in the presence of different anions under excitation at 305 nm. The fluorescence emission of the sensor was remark- ably quenched after addition of Cr 2 . Selectivity of the sensor was studied in the presence of common com- peting metal ions. The obtained results revealed that the sensor had high selectivity toward Cr 2 anion. The linear relationship between the concentration of target anion and the fluorescence intensity was proved by performing a titration experiment. Finally, the detection limit was calculated as 6 × 10 –6 M, which demon- strates high sensitivity of the sensor toward Cr 2 . Keywords: fluorescent sensor, organic-inorganic silica, nanoporous, Cr 2 DOI: 10.1134/S1061934820100135 Chromium is one of the most prevalent elements in the nature. It is widely used in many industries such as mineral processing, pigments, leather tanning and electroplating. Chromium commonly exists as Cr(III) and Cr(VI) which demonstrate remarkably different physiological effects. Although Cr(III) is an essential trace element in human body contributing to main- taining the normal glucose tolerance as well as metab- olism of lipids, proteins and fats [1, 2], Cr(IV) acts as a hazardous element which can easily penetrate human cells, severely damage different organs such as liver and kidney, oxidize biological molecules such as DNA and show a toxic carcinogenic effect [3]. There- fore, detection of Cr(VI) is extremely important. Until now, a variety of methods have been sug- gested for chromium ions detection including ion chromatography [4], electrochemical methods [5], atomic absorption [6] and spectrophotometry [7] which are generally cost and time-consuming, requir- ing sophisticated equipment and complicated sample pretreatment, lacking sensitivity and selectivity to be used in real samples. In contrast, fluorescent sensors have attracted tremendous attentions due to simplic- ity, fast response times, low costs, high selectivity and sensitivity [8–13]. There are a few reports for prepara- tion of a fluorescent sensor in dichromate detection. For this purpose, a europium coordination polymer with composition of [EuL(CH 3 COO)Cl] n was con- structed by Chen et al. [10] using the 4'-(4-carboxy- phenyl)-2,2':6',2″-terpyridine ligand (HL) that con- currently detected Cr , Cr 2 anions and Fe 3+ cat- ion with the detection limit for Cr 2 of 85.4 μM. In addition, another sensor is a one dimensional coordi- nation polymer [Cd(bipy)][HL] n that represents a rare example of a dual functional fluorescent sensor which can detect nitrobenzene and Cr 2 simultaneously [14]. Mohandoss et al. [15] reported an ON-OFF-ON fluorescent sensor based on 1,5-dihydroxyanthraqui- none and β-cyclodextrin that has been used for the colorimetric recognition behavior of Cu 2+ and Cr 2 . Ordered nanoporous silica (ONS) materials, in particular SBA-15, have proven to be of great interest to the scientists in surface chemistry, due to their 2 7 O - 2 7 O - 2 7 O - 2 7 O - 2 4 O - 2 7 O - 2 7 O - 2 7 O - 2 7 O - ARTICLES