Green Synthesized Silver Nanoparticles: A Potential Antibacterial Agent, Antioxidant, and Colorimetric Nanoprobe for the Detection of Hg2+ Ions

Abstract

Silver nanoparticles (AgNPs) prepared by green synthesis have a lot of potentials in various fields. Among them, as an antioxidant, antibacterial agent, and nanoprobe for the colorimetric detection of mercury (Hg²⁺) ions is thought to be the most important. The antibacterial, antioxidant, and colorimetric sensing potential of the greenly produced AgNPs utilizing Piper chaba stem extract are all predicted in this investigation. By using the disc diffusion method, the antibacterial activity of greenly produced AgNPs are assessed, and the findings are measured from the zone of inhibition (ZOI). It is revealed that the Staphylococcus aureus, Micrococcus spp., Escherichia coli, and Pseudomonas aeruginosa bacterial strains are significantly resisted by the greenly produced AgNPs. The antioxidant activity test of AgNPs reveals a considerable impact on free radical scavenging having the inhibitory concentration (IC ₅₀) is 1.13 mL (equivalent to 0.45 mg mL^-1). Also, with a low limit of detection of 28 ppm, the resulting AgNPs are used as highly selective and economical colorimetric sensors for Hg²⁺ detection. The study's findings support the hypothesis that Piper chaba stems can serve as a source for the production of AgNPs with high antibacterial and antioxidant activity and usefulness for simple colorimetric readings of Hg²⁺.

Keywords: antibacterial agent; antioxidant; mercury detection; nanoprobe; silver nanoparticles.

Figure 1

Optical images of the reaction mixtures before and after the reaction with the UV–vis spectrum of AgNPs prepared currently and a year earlier from AgNO₃ and Piper chaba stem extract.

Figure 2

TEM image of AgNPs obtained from AgNO₃ and Piper chaba stem extract.

Figure 3

Zone of inhibition of green synthesized AgNPs against various bacterial strains, measured in diameter.

Figure 4

The relationship between scavenging activity (%) and AgNPs volume (mL) for the green synthesized AgNPs in the DPPH scavenging Assay.

Figure 5

Absorption spectra of AgNPs when exposed to various metal ions (illustration: photo images of corresponding samples).

Figure 6

The relative histogram of absorbance ratio (A/A ₀) of green synthesized AgNPs with various metal ions.

Figure 7

The relative histogram of absorbance of green synthesized AgNPs with various interfering metal ions.

Figure 8

Absorption spectra of AgNPs when exposed to the mixture of various metal ions.

Figure 9

UV–vis absorption spectra of the mixtures of AgNPs and Hg²⁺ with varied Hg²⁺ concentrations (7–70 ppm) (inset: picture of color changes of the mixtures as a function of Hg²⁺ concentration).

Figure 10

A plot illustrating the regression coefficient between the change in absorbance and the concentration of Hg²⁺.

Figure 11

Time‐dependent UV–vis spectra of AgNPs dispersion in the presence of Hg²⁺ ions (35 ppm).