Contents lists available at ScienceDirect Sensors and Actuators B: Chemical journal homepage: www.elsevier.com/locate/snb Fabrication of PdAg nanoparticle infused metal-organic framework for electrochemical and solution-chemical reduction and detection of toxic 4- nitrophenol Shamim Ahmed Hira, Muthuchamy Nallal, Kang Hyun Park ⁎ Department of Chemistry, Pusan National University, Busan, 46241, South Korea ARTICLE INFO Keywords: Metal organic framework 4-Nitrophenol Sensor Electrochemical detection Reduction ABSTRACT In this study, we utilized functionalized metal organic frameworks (MOFs) as a host matrix to embed silver and palladium (AgPd) bimetallic nanoparticles. The physicochemical properties of the as-synthesized materials were characterized Via UV, FT-IR, XRD, SEM, TEM, XPS, BET and TGA analysis. The as-synthesized materials pre- sented excellent activities toward the electrochemical detection of 4-nitrophenol and its reduction by NaBH 4 under ambient conditions. The constructed sensor displayed selective and sensitive determination of 4-NP in the linear concentration range 100–370 μM with a limit of detection of Σ32 nM. Moreover, because of its high specific surface area, high conductivity, and fast charge transfer ability, the sensor displayed good electro- catalytic activity. Moreover, it exhibited excellent selectivity toward 4-NP in the presence of common interfering species. The synthesized catalyst exhibited good catalytic activity for the reduction of 4-NP. It was reusable for five consecutive cycles without a significant loss in its catalytic activity. The applicability of the constructed sensor was explored via the detection of 4-NP in tap water samples at a recovery of ∼100.97%. 1. Introduction Day-by-day water pollution is increasing because of hazardous waste and toxic organic contaminants. The amount of waste released into water is a critical problem in the modern era [1]. Nitroaromatic compounds are steady organic pollutants commonly found in different industrial effluents and are released from pesticides, plasticizers, dyes, and the pharmaceutical industries [2]. Among the various nitroaro- matic compounds, nitrophenols are listed as one of the top 114 organic pollutants by the Unites States Environmental Protection Agency (USEPA). 4-Nitrophenol (4-NP) is one of the obnoxious phenolic pol- lutants found in chemical industrial wastewaters [3]. Because of its high polarity, it is easily soluble in water and also displays high bioa- vailability. Therefore, the sensitive determination of 4-NP and its re- duction into non-toxic molecules has become a current research hotspot [4,5]. Traditionally, the quantitative determination of 4-NP has been achieved by different analytical techniques such as gas chromato- graphy-mass spectrometry [6], high-performance liquid chromato- graphy [7,8], capillary zone electrophoresis [9], fluorescence detection [10] and Ultraviolet-visible (UV–vis) spectrophotometry [11]. How- ever, these techniques have limitations including sample pre-treatment, expensive instrumentation, high cost, and limited selectivity. Mean- while, the electrochemical method has been gaining significant interest because of its quick response, low cost, high sensitivity, and good se- lectivity. Additionally, several other techniques, including adsorption, microwave-assisted catalytic oxidation, electrochemical oxidation, and membrane separation, are also available for the removal of 4-NP and its forms [12–15]. Nevertheless, conventional treatment approaches major shortcomings such as high costs and long reaction times. In a broad sense, the conventional clean up method can be classified in two ways: (i) permanent dismissal of the expected pollutants and (ii) conversion of the target pollutants into less or non-toxic forms. Contrary to 4-NP, 4–aminophenol (4-AP) is less toxic and is an important intermediate that can be applied in many industrial fields [16]. Hence, the sensitive detection and reduction of 4-NP is an important and urgent environ- mental issue. Numerous nanostructured materials have been utilized as electro- catalysts to construct electrodes for the electrochemical determination of 4-NP and other analytes including novel metal (Ag, Au, and Pd) nanoparticles [17–19], carbon-based materials (carbon nanotubes, or- dered mesoporous carbon, and graphene) [20–22], metal oxides (ZnO 2 , Fe 2 O 3 , and MnO 2 ), [23–25] and conducting polymers (polyaniline, polypyrrole, and conjugated polymers) [26–28]. Due to the high cost of https://doi.org/10.1016/j.snb.2019.126861 Received 5 April 2019; Received in revised form 21 July 2019; Accepted 22 July 2019 ⁎ Corresponding author. E-mail address: chemistry@pusan.ac.kr (K.H. Park). Sensors & Actuators: B. Chemical 298 (2019) 126861 Available online 23 July 2019 0925-4005/ © 2019 Elsevier B.V. All rights reserved. T