Preparing and Testing a Magnetic Antimicrobial Silver Nanocomposite for Water Disinfection To Gain Experience at the Nanochemistry–Microbiology Interface

Abstract

We describe a 2 h introductory laboratory procedure that prepares a novel magnetic antimicrobial activated carbon nanocomposite in which nanoscale sized magnetite and silver particles are incorporated (MACAg). The MACAg nanocomposite has achieved the synergistic properties derived from its components and demonstrated its applicability as an effective and recoverable antimicrobial agent for water disinfection. The principle is successfully illustrated by a significant reduction in the number of microbes in an Escherichia coli (E. coli) solution of 2 × 106 colony forming units following its treatment with MACAg for 10 min. The exercise allows the college students to (1) be introduced to an exciting class of advanced materials, known as nanocomposites, at an early stage, (2) gain working experiences at nanochemistry–microbiology interface, and (3) see the use and experience the fun of chemistry. The experiment uses readily available materials, can be run in a general or introductory chemistry laboratory environment, and is well received and enjoyed by the students. The experiment is also suitable for advanced high school students.

Magnetically Recoverable and Reusable Antimicrobial Nanocomposite Based on Activated Carbon, Magnetite Nanoparticles, and Silver Nanoparticles for Water Disinfection

“…This shows the antimicrobial effect of MACAg decreased with increasing E. coli concentration. Figure 4 illustrates the effectiveness of MACAg (0.04% Ag) against E. coli in a suspension of 2 × 10 5 CFU/mL [29]. The results in Figure 4a demonstrated increased microbial reduction effect in the treated water with increasing treating time.…”

“…The scanning electron microscopy (SEM) images of MNPs and AgNPs show that the MNPs were of sizes ranging from 10 to 20 nm, and AgNPs around 10-12 nm [29]. The plasmon absorbance of the yellow colloidal silver produced a peak at 399 nm with PWHM (peak width at half max) of 50-70 nm in the UV-visible spectrum.…”

“…This peak corresponds to AgNP sizes of 10-12 nm, supporting the SEM result, and remains clearly visible at a trace concentration of 0.10 ppm. The SEM image of MACAg reveals the agglomerates of the MNPs and AgNPs of sizes less than 20 nm embedded onto and covering the AC surface [29]. If all the silver from the added 2-10 mL of 1.0 mM AgNO 3 solution were incorporated into MAC, the theoretical mass content of silver would range from 0.04% to 0.22%.…”

“…Inventions Figure 3a was published in reference [29]. AgNPs = silver nanoparticles; MNPs = magnetite nanoparticles; CFU = colony-forming units.…”

“…At the U.S. Merchant Marine Academy, this procedure is modified and has been successfully implemented in the Chemistry for Marine Engineer course where 165 midshipmen have participated in preparing MACAg and testing its antimicrobial activity [29]. To our knowledge, such a nanocomposite has not been reported by other research groups.…”