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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.

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Mesoporous gold−silica nanocomposites have been synthesized through simple one-step sol−gel reactions of tetraethyl orthosilicate (TEOS) with a gold sol in the presence of dibenzoyl tartaric acid (DBTA) as a nonsurfactant template. The gold nanoparticles were incorporated into the three-dimensional silica network through the sol−gel process to afford monolithic crack-free DBTA-containing gold−silica gels. After removal of DBTA by calcination at 550 °C, annealed mesoporous gold−silica nanocomposites were obtained. The pore structure parameters were investigated by means of nitrogen sorption isotherm, X-ray diffraction, and transmission electron microscopy (TEM). The results indicate that the mesoporous structure of the gold−silica nanocomposites has high surface areas up to 630 m2/g, large pore volume of ∼0.5 cm3/g, and pore diameters of 3−4 nm with relatively narrow pore size distributions. With use of energy-dispersive X-ray (EDX) elemental analysis, the compositions of the gold−silica composite materials were quantitatively measured. The effects of gold content on the pore parameters have been addressed. The TEM and X-ray mapping images show that gold particles in the range of 2−8 nm are homogeneously distributed throughout the silica matrixes for all the samples. The surface plasmon resonance of gold nanoparticles was also investigated.

Mesoporosity combined with organic polymer functionality and hydrophobicity could give rise to promising new materials with applications in host–guest chemistry and biosensor devices. The synthesis of polymer–silica hybrid mesoporous materials with pore sizes of 3–6 nm is described, in which materials with large specific surface areas (∼800 m2 g–1) and pore volumes (∼0.7 cm3 g–1) as well as relatively narrow pore size distributions are produced by a sol‐gel reaction in the presence of a non‐surfactant template or pore‐forming agent, which is subsequently removed by solvent extraction.

We interpret the UV absorption and fluorescence of cysteine and cystine from ab initio calculations of the ground states and lowest excited singlet states of the two molecules. We derive the optimized energies and geometry parameters from HF/6-31G computations on the ground state and CIS/6-31G computations of the excited state. We present vibrational frequencies of the ground and excited states and quantitative predictions for UV absorption and fluorescence. We also show experimental measurements of cystine fluorescence. Cystine is shown to fluoresce at 700 nm.

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