Use of Surface-Enhanced Raman Spectroscopy in Inorganic Syntheses for an Upper-Level Exploratory Lab

Abstract

The guided synthesis and partial characterization of Ag and Au nanoparticles using UV–vis and surface-enhanced Raman spectroscopies (SERS) is described in this article. The experiment asks students to search literature for a synthetic preparation for Au and Ag nanoparticles, for organic molecules to adsorb to the nanoparticles, and for routes to characterize their nanoparticles and nanoparticles conjugates. After successful synthesis as determined by UV–vis absorption peaks has been achieved, students bind organic molecules (ones in which literature has proven to bind to Au and Ag nanoparticles) to the nanoparticles in solution. Once binding has been determined via a slight shift in the original nanoparticles' UV–vis absorption peak, students determine SERS activity through use of a modular Raman system that uses a 514.5-nm Ar+ laser. The experiment may be modified depending on instructor preference to focus on one of three areas: inorganic syntheses (Au and Ag nanoparticles), investigating the site through which functional groups of organic molecules bind, or investigating enhancement factors of different metallic nanoparticles by SERS. These studies can be achieved within five to six, three-hour laboratory periods.

Surface-Enhanced Raman Scattering on Chemically Etched Copper Surface: An Upper-Level Spectroscopic Measurement and Analysis

“…Thorough and elaborate chemical and physical processing methods are followed to make these nanostructures. Often these processes are complicated, expensive, and time-consuming. − …”

Achieving Very Low Levels of Detection: An Improved Surface-Enhanced Raman Scattering Experiment for the Physical Chemistry Teaching Laboratory

“…There are several reported synthetic methods for preparing SERS active colloidal Ag nanoparticles, , but not all of them are all accessible or practical for teaching laboratory experiments. Some have been applied to SERS experiments, − but the emphasis of this experiment is different . Unlike these previously reported experiments, this one focuses on combining a simple, rapid, room-temperature synthesis (based on that developed by Leopold and Lendl) with UV–visible and SERS spectroscopy to guide the students toward investigating the minimum level of detection of MB.…”

“…Some have been applied to SERS experiments, 18−20 but the emphasis of this experiment is different. 21 Unlike these previously reported experiments, this one focuses on combining a simple, rapid, room-temperature synthesis (based on that developed by Leopold and Lendl) 22 with UV−visible and SERS spectroscopy to guide the students toward investigating the minimum level of detection of MB. By reducing the time and complexity of the synthesis step, the students can focus on characterizing and using their colloid.…”

Take-Home Nanochemistry: Fabrication of a Gold- or Silver-Containing Window Cling

“…Research in materials at the nanoscale (1–100 nm) size regime continues to abound. At the same time, the field of chemistry education has also incorporated nanoscale structures and concepts (see, for example, the May 2011 issue of this Journal ). − The optical properties of gold and silver are popular illustrations of how the properties of nanoscale substances can be different from molecular or bulk substances. For example, nanoscale gold metal particles often have reddish colors due to their absorption of light by their plasmons (collective free-electron oscillations within the particles) .…”

“…For example, nanoscale gold metal particles often have reddish colors due to their absorption of light by their plasmons (collective free-electron oscillations within the particles) . The reddish colors associated with small gold particles have been known for centuries, for example, in aqueous suspensions used for medicinal purposes and in glass objects where the particles were used for pigmentation. ,− Silver metal nanoparticles often have yellowish colors and have also been used to add color to glass. , Many educational activities involving metal nanoparticles (and their optical properties) produce them in a liquid suspension by reduction of the appropriate metal species, and then these resulting particles are sometimes incorporated into other structures. − In this laboratory experiment, students can grow and characterize gold or silver nanoparticles embedded within solid silicone matrices and then can take the tinted polymer samples home as decorative window clings, as these objects will adhere to glass by intermolecular forces without the need for glue or tape.…”