A Polyaniline‐Supported, Chromium‐Based Metal‐Organic Framework for Electrochemical Sensing of Cadmium(II)

Abstract

In this work a conducting electrochemical sensing probe, Cr-BDC-NH 2 @PANI composite material (BDC = 1,4-benzenedicarboxylate), was successfully synthesized by polymerization of conducting polyaniline (PANI) around the Cr-BDC-NH 2 material. The synthesized composite material was characterized by various analytical techniques. The Cr-BDC-NH 2 @PANI composite was successfully dropped cast on the surface of an inexpensive pencil graphite electrode (PGE) to detect the cadmium ions at trace level. The selectivity of proposed sensor observed towards cadmium ion is due to chelation mechanism operating between cadmium ions and amine groups. Under optimized condition, the proposed sensor is capable of measuring cadmium ions in aqueous as well as in human blood serum, plasma, and various water samples within the range of 0.50-32.5 μg L À 1 with the limit of detection (LOD) of 0.20 μg L À 1 . The Cr-BDC-NH 2 @PANI composite material modified sensor shows high affinity and no interference with real samples.

Recent advances in the modification of electrodes for trace metal analysis: a review

“…Nandy et al 97 synthesized a block copolymer from poly (methyl methacrylate) and poly(2-acrylamido-2-methylpropane sulfonic acid) and, in combination with Ag-NPs used it to modify a GCE for the determination of Hg 2+ . Different forms of carbon-containing materials (i.e., graphene, GO, rGO, CNTs, and g-C 3 N 4 ), 29,32,38,45,80,87,91,98,99,101,141,142,144,176,183,184,206 NPs and nanoflakes, 23,87,94,[96][97][98][99]101,102,124,176,182,200,218 and MOFs 208,209,213,216 were combined with the polymers and biopolymers to obtain the modified electrodes. Chelating agents, such as 2,2′,2″,2′′′-(ethane-1,2-diyldinitrilo)tetraacetic acid (EDTA) and L-cysteine, have also been included in these polymer-containing nanocomposites.…”

“…Table S4 in the ESI † summarizes the main findings of the research studies published in the last five years regarding the use of different metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) as modifiers for various types of electrodes employed in the determination of trace heavy metals. Several MOFs 42,53,116,[150][151][152][153][154]164,177,201,208,209,212,216,236,237,[279][280][281][282][283][284][285][286][287][288][289][290][291][292][293][294][295][296][297] and COFs 198,[298][299][300][301][302] have been employed as modifiers for different types of electrodes in combination with other materials. MOFs are 1D, 2D, or 3D network like structures, highly ordered crystalline materials formed by self-assembly of metal ions or clusters and organic ligands through coordination bonds.…”

“…To increase the charge transfer (i.e., to facilitate the electron transfer through the electrode surface to or from the electroactive species in solution) and to improve their mechanical strength, MOFs have been combined with carbon-containing materials, such as graphene (mainly rGO), 42,53,285 MWCNTs, 150,[152][153][154] mesoporous carbon, 282 carbon black, 236 and expanded graphite. 286 The addition of conducting polymers (mainly PANI and PPy) 208,209,212,213,216 to MOFs has resulted in higher conductivity and stability in water. The development of core-shell structures has been reported to not only increase the stability, but also improve the LOD of the modified electrodes used for the determination of Pb 2+ , Cd 2+ , and Cu 2+ ions.…”

“…Although GCEs are by far the most commonly used substrates for the application of different types of MOFs and COFs, 53,116,150,[152][153][154]177,198,201,216,236,237,[279][280][281][282][283][284][285][286][287][288][289][290]298,299 several other types of electrodes have also been modified, including CPEs, 291,292,301 SPCEs, 42,209 gold electrodes, 212,293 as well as PGEs, SPEs, and carbon cloth electrodes (CCEs). 208,294,295,298 In addition, Yang et al 296 and Han et al 300 reported on the attachment of a mercaptan functionalized Zr-based MOF as well as a 1,4-benzenedithiol-2,5-diaminohydrochloride and 1,3,5-triformylbenzene condensed COF to a 3D-structure kenaf stem derived carbon. These combined electrodes have been employed in either the simultaneous determination of Cd 2+ , Pb 2+ , Cu 2+ , and Hg 2+ or for the determination of Hg 2+ individually.…”

“…The authors reported that the integrated electrode has better analytical performance compared with the GCE modified electrode. 296 In addition to different real water samples, modified electrodes have also been successfully employed in the determination of heavy metals in food, 42,53,116,151,236,293 spices, 198,302 and body fluid 208,209 samples.…”