Combination of Microporous Hollow Carbon Spheres and Nafion for the Individual Metal-free Stripping Detection of Pb2+ and Cd2+

Abstract

IntroductionWith the increasingly severe water, soil, agriculture, and food pollutions resulting from heavy metals and their harmfulness to living organisms, the sensing of these heavy metals with reliable results and convenient operations turns out to be of great significance.1-4 Among all well-established methods for trace metal determination, including inductively coupled plasmaatomic emission spectrometry (ICP-AES), atomic absorption spectroscopy (AAS), and inductively coupled plasma-mass spectrometry (ICP-MS), electrochemical stripping analysis is always recognized as an efficient detection tool. 5 Especially, the superiorities of miniaturized equipment, low cost, and test rapidity endow this approach with wide applications in in-field/ on-site monitoring. Early stripping measurements of heavy metals are performed with mercury-based electrodes. [6][7][8] Considering its hypertoxicity, replacing mercury with other "green" metals, such as gold, 9,10 bismuth, [11][12][13][14][15] antimony, [16][17][18] tin, 19 and copper, 20 has been recommended for heavy metal sensing. In stripping analysis with metal electrodes as the sensing platform, high-concentration metal precursors (up to mg/L) are usually utilized for the in-situ preconcentration, and a posttreatment is also required to clear off the metal residues. During these processes, secondary pollution from these metals possibly occurs. In this context, developing metal-free electrodes, instead of metal-based electrodes, seems to be more attractive, from the perspective of "green analysis", for the anodic stripping determination of trace heavy metal ions.Carbon-based materials, especially porous carbon, are extensively used in the adsorption, separation and purification, catalysis, and energy-storage fields. [21][22][23] They can provide large specific surface area, excellent chemical and mechanical stabilities, and versatile structures with low production cost. With these properties, nanoscale carbon-based materials are also adopted as an active component for heavy metal sensing. 24 Up to date, multi-wall carbon nanotubes, [25][26][27] have been reported for the stripping detection of heavy metal ions. In the present work, we introduced a new carbon-based material, microporous hollow carbon spheres (MHCS), to the stripping analysis application. Nafion, a perfluorinated ion exchange polymer or ionomer, is commonly used as a binder to immobilize active materials onto electrode substrates. With the easy film-formation and its hydrophobic fluorocarbon network, the Nafion film is highly stable in aqueous solution both thermodynamically and chemically. In addition to the inert binder role, Nafion can act as an active material as well. Here, the combination of Nafion with microporous hollow carbon spheres (MHCS) is first proposed to fabricate a disposable metal-free electrode for heavy metal stripping sensing. The MHCS-Nafion composite film electrode is prepared by drop-casting a mixture of MHCS and Nafion onto the lab-made screen-printed carbon electrode (SPCE*).Re...

Disposable Sensors for Heavy Metals Detection: A Review of Carbon and Non‐Noble Metal‐Based Receptors

“…The linearity of the sensor was observed between 2-200 μg/L with a low LOD of 1.37 μg/L for Cd 2 + and 1.63 μg/L for Pb 2 + ions. [44] The microband screen printed electrodes (SPE) without any modifications were also investigated for voltammetric detection of Pb 2 + in the leachate of ceramic glazed plates by Honeychurch et al The objective of the study is to make a mercury-free analysis of metal ions. The effect of applied potential, accumulation time, and analyte concentration was investigated and optimized for better electrochemical performance.…”

“…Also; the presence of MHCS provides active nucleation sites for the reduction of metals on the surface of the electrode. The linearity of the sensor was observed between 2—200 μg/L with a low LOD of 1.37 μg/L for Cd 2+ and 1.63 μg/L for Pb 2+ ions [44] . The microband screen printed electrodes (SPE) without any modifications were also investigated for voltammetric detection of Pb 2+ in the leachate of ceramic glazed plates by Honeychurch et al.…”

Sensitive and Label‐Free Electrochemical Immunosensor for Alpha Fetoprotein Based on N‐Doped Hollow Nanocarbon Spheres Decorated with Gold Nanoparticles

“…Recently, hollow nanocarbon spheres (HNS) has become a hotspot, showing great promising applications in various areas owing to its fascinating superiorities such as cheap, large surface area and strong conductivity [32–37] . However, there are only a bit of work based on HNS developed in the field of electroanalysis.…”

“…Recently, hollow nanocarbon spheres (HNS) has become a hotspot, showing great promising applications in various areas owing to its fascinating superiorities such as cheap, large surface area and strong conductivity. [32][33][34][35][36][37] However, there are only a bit of work based on HNS developed in the field of electroanalysis. For example, Zhang et al [38] constructed a HNS/ polyaniline-based electrochemical biosensor for sensing sensitively malathion, whereas Shahrokhian's group [39] used HNS to construct a sensitive and selective sensing assay for isoprenaline.…”

Sandwich-type electrochemical immunosensing of Hypopharyngeal carcinoma biomarker carcinoembryonic antigen based on N-doped hollow mesoporous nanocarbon spheres/gold hybrids as sensing platform and gold/ferrocene as signal amplifier

“…In recent years, hollow mesoporous nanocarbon spheres (HMN) have became a hot spot and they have important promising applications in many areas (e.g., catalysis, lithium-ion batteries, oxygen-reduction, supercapacitors) resulted from their fascinating properties such as hollow nanostructure, high surface area and electric conductivity. [17][18][19][20][21][22][23] However, only a few works based on HMN were applied in field of the electrochemical analysis. For instance, Zhang and He et al 24 developed a sensitive electrochemical sensor for detecting malathion based on HMN and polyanilin.…”