Full length articleRapid colorimetric detection of arsenic (III) by glutathione functionalized gold nanoparticles based on RGB extracting system
Introduction
Among various inorganic species, arsenic is considered as one of the potent toxic metal, which is related to many adverse health effects, such as heart disease, skin cancer, kidney and brain damage, etc. [1], [2]. Arsenic can occur in the environment in several oxidation states (−3, 0, +3 and +5), but in natural waters it is mostly found in inorganic forms as oxyanions of trivalent arsenite (AsIII) or pentavalent arsenate (AsV) [3]. Arsenite is the most stable soluble form of arsenic in reducing environments, and is generally more acutely toxic than arsenate [4]. It is reported that around 140 million people around the world may have been exposed to contaminated water with the levels of arsenic higher than the World Health Organization (WHO) guideline of 10 ppb [5]. Thus, it’s urgent to develop effective methods to detect and monitor the levels of arsenic ions in water.
Recently, the colorimetric method provides a promising sensing platform for heavy metal ions due to its simplicity, visualization and low-cost [6], [7], [8]. Plenty of colorimetric probes based on functionalized gold nanoparticles (AuNPs) have been applied to detect different metallic ions, such as Pb2+ [9], Cd2+ [10], Hg2+ [11], [12], Cu2+ [13], [14], Ca2+ [15], Fe3+ [16], Cr3+ [17], [18], etc. Particularly, many attentions have been paid to the detection of arsenic ions. Park et al. reported a synergistic molecular assembly of aptamer on AuNPs for the detection of trace level arsenic ions using CTAB as a binder, and the limit of detection (LOD) was 16.9 ppb [1]. Shrivas et al. adopted the lauryl sulphate modified AuNPs to detect arsenic ions, and the detection limit was about 2 ppb [19]. Biswas et al. developed the polyethylene glycol functionalized AuNPs for arsenic ions detection, and the LOD was about 5 ppb [20]. Likewise, Biswas et al. also used the glucose functionalized AuNPs for the selective detection of arsenic ions, with the LOD about 0.53 ppb [21]. However, most of these methods depend on manual analysis of the color changing, which makes the results susceptible to the interference of noise and affects the detection accuracy. Furthermore, these methods are associated with the defects of professional and costly instruments, which impose a barrier for practical applications.
In this work, we have developed glutathione (GSH) functionalized AuNPs (GSH-AuNPs) solution for rapid, sensitive and selective colorimetric detection of arsenic (AsIII) ions. Fig. 1 illustrated the mechanism of colorimetric detection of arsenic ions using GSH-AuNPs solution. The formation of As-O bonds between arsenic ions and functionalized ligands induced dramatic aggregation of AuNPs, resulting in a rapid color change [22]. More importantly, we developed a windows-based automatic RGB extracting system to correlate the color change of GSH-AuNPs solution with the concentrations of arsenic ions. With the help of RGB extracting system, we could open up analytical platform for on-site and real-time fast detection of low level arsenic ions.
Section snippets
Materials and chemicals
Chloroauric acid and sodium citrate were purchased from Sinopharm Chemical Reagent Co. Ltd. Glutathione and arsenic (standard solution) were purchased from Sigma-Aldrich. The chloride salts of Fe3+, Co2+, Ni2+, K+, Na+, Mg2+, Ca2+, Cu2+, Hg2+, and Pb2+ were purchased from Aladdin. All the reagents were analytical pure grade.
Synthesis of gold nanoparticles
AuNPs were synthesized via chemical reduction method [4]. Briefly, 0.5 mL of 20 mM chloroauric acid was added to 50 mL distilled water in a flask. The mixture solution was
Results and discussion
The influence of GSH ligand on morphology and absorption property of AuNPs was investigated by the TEM image (Fig. 2a and 2c) and absorption spectrum (Fig. 2d). The sizes of AuNPs ranged from 20 nm to 50 nm (Fig. 2b), with the most falling in the range of 30–40 nm. The color of as-prepared GSH-AuNPs solution was pink, indicating AuNPs were well dispersed in the solution. The maximum absorption peak of AuNPs and GSH-AuNPs were both located at 525 nm, illustrating that GSH ligand had little
Conclusions
In summary, a rapid, sensitive and selective method for the colorimetric detection of arsenic has been demonstrated using GSH-AuNPs solution. With the implementation of a home-developed RGB extracting system, excellent linear correlation has been established between the arsenic concentrations and the calculated RGB colorvalues (R2 = 0.99488). The limit of detection of arsenic ions is as low as 0.12 ppb, and the detection accuracy is within 2%. Compared with other arsenic ion sensing approaches,
CRediT authorship contribution statement
Biao Zheng: Conceptualization, Investigation, Writing - original draft, Funding acquisition. Jing Li: Investigation. Zhongkai Zheng: Software. Cheng Zhang: Writing - review & editing. Chunlei Huang: Data curation. Jinquan Hong: Formal analysis. Yuliang Li: Project administration. Jun Wang: Supervision, Funding acquisition.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors are grateful for many fruitful discussions with Dr. Weiqi Li. This work was supported by the National Natural Science Foundation of China (Nos. 11674185 and 11947016), the Natural Science Foundation of Fujian (Nos. 2019J01764 and 2019J05110), the Natural Science Foundation of Ningbo (2018A610007) and the Open Project Program of Fujian Key Laboratory of Novel Functional Fibers and Materials (FKLTFM1812).
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