On-Line Spectroscopic Characterization of Sodium Cyanide with Nanostructured Gold Surface-Enhanced Raman Spectroscopy Substrates

Abstract

To implement surface-enhanced Raman spectroscopy as a practical detection method, highly enhancing, stable, and reproducible substrates need to be fabricated in an efficient manner, and their performance in different solution environments should be well characterized. In this work structured porous gold films have been fabricated using colloidal crystals to template gold nanoparticles. These films were integrated into an on-line flow chamber and used to study the effects of pH and other additives on the detection of sodium cyanide. The gold films proved to be highly enhancing and were used to detect cyanide over a wide range of pH values in the concentration range of ∼2 to 200 ppb. The Raman signal intensity could be increased by lowering the pH after the adsorption of cyanide, which was likely due to both a change in the ionization state and a conformational change of the bound molecules. The peak intensity could also be enhanced multifold by treating the substrate with silver nitrate. Cyanide could be removed from the substrates using hydrochloric acid, although this also passivated the structures, and the activity could only be restored partially with tannic acid. These results provide a rational method to optimize the online detection of cyanide in water.

Controlled assembly of SERS substrates templated by colloidal crystal films

“…42 Furthermore, the substrates performed well over a broad range of concentrations and pH values. 16 The most intense SERS signals were reproducibly obtained on films with ordered polycrystalline micropores similar to the ones shown in Fig. 2.…”

“…All experimental measurements were performed using a point sampling protocol in a microfluidic flow cell. 16,19 Such online flow cells could be directly used as a basis for SERS sensors for continuous monitoring of water or gas fluxes. Post-deposition treatment of the nanoparticle layers with dimethyldichlorosilane vapor hydrophobized the glass substrates, enhancing the adhesion of the gold films, and improving their stability to the extent that they can be subjected to prolonged exposure to shear flows in the experimental cells.…”

“…Post-deposition treatment of the nanoparticle layers with dimethyldichlorosilane vapor hydrophobized the glass substrates, enhancing the adhesion of the gold films, and improving their stability to the extent that they can be subjected to prolonged exposure to shear flows in the experimental cells. 16 A matrix of experiments was designed to isolate individual contributions to the Raman enhancement arising from the nano-and microstructure. 19 We collected multiple data points from randomly chosen spots on each SERS substrate inside the microfluidic chamber filled with liquid.…”

Inhibition of Rhodamine B-Ferricyanide Chemiluminescence by Gold Nanoparticles and Sensitive Determination of Hazardous Cyanide

“…[26][27][28] Cyanide has a strong propensity to form Au(CN)4 -complex with gold atoms, which leads to the dissolution and destruction of AuNPs. [26][27][28] TEM images in Fig. 3 show the morphology of the AuNPs before and after addition of CN -ions.…”

“…Several simple and sensitive colorimetric and luminescence methods based on the interaction process between gold nanostructures and cyanide was established for its determination. 8,[23][24][25][26][27][28][29][30] For example, selective gold-NPs-based chemiluminescence method was developed for the detection of CN -by Amjadi et al 8 Cyanide can efficiently quench the chemiluminescence emission of KMnO4-RohB-AuNPs reaction, due to its interaction with AuNPs. A gold-nanocluster-based fluorescent sensor for cyanide in aqueous solution, which is based on the cyanide etching-induced fluorescence quenching of gold nanoclusters, has been reported.…”