Plasmonic Gold Nanoparticles Stain Hydrogels for the Portable and High-Throughput Monitoring of Mercury Ions

Abstract

The hybrid of l-cysteine and agarose can reduce HAuCl4 and support the rapid growth of plasmonic gold nanoparticles (Au NPs) in the hydrogel phase. The l-cysteine-doped agarose hydrogel (C-AGH) not only offers the substrate the capacity to reduce Au­(III) ions but also stabilizes and precisely modulates the in situ grown Au NPs with high repeatability, easy operation, and anti-interference performance. Herein, before the incubation of HAuCl4, the improved hydrogel is preincubated in the aqueous solution containing mercury ions, and the cysteine can specifically conjugate with mercury via the thiol groups. Subsequently, the responsive allochroic bands from dark blue to red can be identified in the solid hydrogel after the incubation of HAuCl4, which is attributed to the formation of regulated Au–Hg nanoamalgams. As a proof-of-concept, toxic Hg2+ ions are exploited as targets for constructing novel sensing assays based on the improved C-AGH protocol. Based on naked-eye recognition, Hg2+ could be rapidly and simply measured. Additionally, the high-throughput and trace analysis with a low limit of detection (3.7 nM) is performed using a microplate reader. On the basis of the filtering technique and remodeling of hydrogels, C-AGH working as the filtering membrane can even achieve the integration of enrichment and measurement with enhanced sensitivity. Significantly, the strategy of using an allochroic hydrogel with the staining of Au NPs can promote the rapid and primary assessment of water quality in environmental analysis.

Hydrogels allow the precise growth tracking of plasmonic gold nanoparticles for mercury analysis

“…Thus, the practical applications of hydrogel-based sensing techniques are promoted. In addition, compared to our previous report, 33 this work exhibits improved dispersion and stabilities in signal readout via the removal of HAuCl 4 diffusion treatments. Importantly, the nanostaining protocol not only works in the hydrogel phase but also has high potential in expanded sensing substrates.…”

“…Therefore, the sensing mechanism of nanostaining hydrogels, showing the responsive LSPR influenced by the amalgamation, could be proposed. 33 Due to the amalgamation, the aggregative growth of gold nanoparticles to larger nanospheres was prevented. 33 Therefore, the blueshift of LSPR absorption in the presence of Hg 2+ could be used for quantitative analysis.…”

“…33 Due to the amalgamation, the aggregative growth of gold nanoparticles to larger nanospheres was prevented. 33 Therefore, the blueshift of LSPR absorption in the presence of Hg 2+ could be used for quantitative analysis. The Fourier transform infrared (FTIR) spectra of diverse samples of agarose hydrogels indicated that the composition of agarose before and after the staining of gold NPs remained consistent (Fig.…”

“…29,30 In addition, the agarose hydrogel was also used as the alternative of the aqueous solution, aiming at improving the practical sensing performance based on nanoanalysis method. 33 Considering the chemical inertness of agarose, comparable reductants are suggested to be modified in agarose hydrogels for the synthesis of plasmonic nanoprobes. l -Cysteine is the only amino acid with sulfhydryl (–SH) reductive group among more than 20 kinds of natural amino acids and is used as a green reducing reagent.…”

Virtual Simulation Guiding High-Risk Undergraduate Experiments about Chemical Synthesis of MoS2 Monolayers via a Schlenk Line

“…Additionally, the dangerous step-by-step processes could be highlighted for preventing an emergency from occurring. This design attracted high attention for the students, inspiring them to pursue the corresponding knowledge and academic novelty from the chemical experiments. − Of importance, the safety of undergraduate students could be guaranteed. The learning merits of this stimulation chemical courses referring to their time, places, resource-independent characteristics are available and also preferable during the COVID-19 pandemic.…”