Plasmonic Evolution and Arrested Development for Silver Nanoscale Colloids: A Classroom Demonstration

Abstract

A vivid demonstration visualizing the colloidal behavior of silver nanocrystals is described. An aqueous–ethanol silver ion solution becomes yellow upon initial chemical reduction (using sodium borohydride, NaBH4), which is followed by chromatic evolution to orange, red, violet, and finally blue over the course of approximately 3 min because of the predictable growth and evolution of the nanocrystals. This undergraduate-level classroom demonstration is useful for illustrating the protective effect of a passivating ligand, such as polyvinylpyrrolidone (PVP), by showing the ability of PVP to halt the growth and coalescence of silver colloids at a desired stage, arresting the color transition at a particular hue. This demonstration can also be extended to highlight the bifurcated impact of such passivation on colloid behavior (e.g., improved long-term colloid stability coupled with worsened nanocatalytic performance).

Preparation and Characterization of Japanese Ink-Inspired Aqueous Dispersions of Carbon Materials with the Help of Glue as Colloid Chemistry Teaching Aid

“…In order to obtain more detailed information, the particle size distribution was measured by DLS, which yielded an average particle diameter of 566 ± 5.7 nm. On the basis of the raw material recovery rate, the concentration of the prepared fullerene dispersion liquid was estimated to be 1.12 × 10 –2 M. Even when compared with literature values, − this is considered an extremely high-concentration fullerene dispersion. Subsequently, the fullerene dispersion was centrifuged at a rotation speed of 3500 rpm for 30 min.…”

“…2 Experiments have been developed to demonstrate various phenomena in the field of colloid science, such as Brownian motion, the Tyndall phenomenon, sol−gel transitions, and salting out, or the reduction in solubility of certain molecules in solutions of very high ionic strength, to students of chemistry. 3−13 Materials used in these demonstrations include iron(III) oxide sols, 5,6 sodium bentonite, 7 ZnO-based sunscreen, 8 homemade slime, 10 silver, 9,11 copper, 12 and fluorescent carbon nanoparticles. 13 Recently, Baker reported a classroom demonstration of polyvinylpyrrolidone, which behaves as a protective colloid against colloidal silver nanoparticles.…”

“…13 Recently, Baker reported a classroom demonstration of polyvinylpyrrolidone, which behaves as a protective colloid against colloidal silver nanoparticles. 11 Protective colloids are lyophilic colloids that, in solvents, prevent charge repulsion from inducing precipitation. Such colloids, where hydrophilic colloids surround hydrophobic colloids, are widely used in food products like ice cream and gummy candy.…”

“…Furthermore, colloidal carbon is used in the industrial production of materials, such as tires and inks . Experiments have been developed to demonstrate various phenomena in the field of colloid science, such as Brownian motion, the Tyndall phenomenon, sol–gel transitions, and salting out, or the reduction in solubility of certain molecules in solutions of very high ionic strength, to students of chemistry. − Materials used in these demonstrations include iron­(III) oxide sols, , sodium bentonite, ZnO-based sunscreen, homemade slime, silver, , copper, and fluorescent carbon nanoparticles …”

“…Recently, Baker reported a classroom demonstration of polyvinylpyrrolidone, which behaves as a protective colloid against colloidal silver nanoparticles . Protective colloids are lyophilic colloids that, in solvents, prevent charge repulsion from inducing precipitation.…”