An unusual red-to-brown colorimetric sensing method for ultrasensitive silver(i) ion detection based on a non-aggregation of hyperbranched polyethylenimine derivative stabilized gold nanoparticles

Abstract

Here we have developed a facile and rapid colorimetric method for the sensitive and selective detection of Ag(+) based on the non-aggregation of gold nanoparticles (Au NPs) capped with hyperbranched polyethylenimine derivatives. In the detection process, an unusual colour change from red to brown was observed due to the formation of Au-Ag core-shell nanoparticles, which was more sensitive than that of the usual colorimetric assays (red to blue) based on the aggregation of Au NPs. After the colour changed, the non-aggregation-based Au-Ag core-shell nanomaterials did not aggregate further and could remain stable for a long time, which was convenient to record, detect and observe. The sensing probe exhibited a drastically long observing time for detecting Ag(+) owing to the stability of the Au-Ag core-shell non-aggregates, high sensitivity with a low detection limit of 8.76 nM by the naked eye and 1.09 nM by using a UV-vis spectrophotometer and a good linear relationship within the range from 1.09 to 109 nM. The colour change of the system is very fast, occurring within 1 to 2 minutes. Moreover, the proposed method also showed a remarkably high selectivity toward Ag(+) and was successfully used in tap water and drinking water samples. Therefore, this unusual colorimetric assay based on the non-aggregation of Au NPs has a great potential as a simple, rapid, sensitive and selective detection method for the detection of Ag(+).

Non‐Aggregation‐Induced Colorimetric Detection of Ag+ by Tetrazine‐Capped Gold Nanoparticles Based on the Formation of Au‐Ag Core‐Shell Nanoparticles

“…34‐35 However, the use of AA could sometimes lead to precipitation of Ag(0) if the concentration of AA is not controlled. Moreover, for most of the previously reported colorimetric assays, the extensive synthesis of a hyperbranched polymer is necessary to stabilize Au and Au‐Ag core‐shell NPs and to observe distinct color change …”

“…An easy and rapid synthesis of TzAuNPs inspired us to explore if elimination of external reducing agent could be achieved for the detection of Ag + ion to make the detection system cheap and uncluttered. Previously reported non‐aggregation‐based colorimetric assay for Ag + detection is based on the formation of Au‐Ag core‐shell nanoparticle, generating an unusual brown colour . For those reported assays reduction of Ag(I) to Ag(0) has been facilitated by an external reducing agent (mostly ascorbic acid).…”

“…Unfortunately, these methods suffer from short observing time due to unstable aggregation‐induced emission. Recently, few non‐aggregation based colorimetric assay for detection of Ag(I) using AuNPs through the formation of Au−Ag core‐shell nanoparticles have been reported …”

Highly selective, colorimetric detection of Hg2+ based on three color changes of AuNPs solution from red through sandy beige to celandine green

“…Reported colorimetric detection of Ag + based on AuNPs stabilized by hyperbranched polyethylenimine derivative also showed similar color change (red to brown). [20] Let's imagine if one colorimetric probe for Hg 2+ testing occur successively three color changes during the detecting process. The specificity and selectivity of this colorimetric sensor should be greatly improved owing to the extremely low possibility of false positive results.…”

Highly Sensitive Detection of Silver Ions Enabled by RecJf Exonuclease Cleavage and Reductant‐Mediated Electrochemical Amplification

“…[5,6] Nevertheless, these techniques always require sophisticated instruments, well-trained operators, and excessive testing costs,w hich have stimulated intensive research into the development of novel sensors for Ag + analysis. [7] As eries of colorimetrics ensing strategies have been proposed for simple, rapid, andl ow-cost sensing; [8][9][10] electrochemical techniques with the advantages of high sensitivity and selectivity have been appliedf or Ag + measurements; [11][12][13] and fluorescent detection methods with enhanced signals based on Ln 3 + -doped metal-organic frameworks (MOFs) or aggregation-induced emissionnanoclusters have also been fabricated. [14,15] Herein, we presentan ovel electrochemical approachf or Ag + detection based on RecJ f exonuclease cleavage and reductant-mediated electrochemical amplification.…”