Fluorescent dye adsorption on nanocarbon substrates through electrostatic interactions

Nanodiamonds (NDs) with modified surface functional groups and surface characteristics are an attractive model to understand adsorption mechanisms of molecules on substrates. The research described in this paper illustrates the binding mechanisms of fluorescent dyes to ND surfaces as these interactions are extremely useful in many biomedical ND applications. A thorough study of binding and release mechanisms was completed using an assortment of carbon based nanoparticles, including NDs, onion-like carbon. and single-wall nanohorns. Surface charge interactions were studied in combination with surface areas, configurations, and modifications in order to determine which is responsible for the largest adsorption capacity and strongest binding. Adsorption studies were carried out using UV-Vis measurements followed by maximum binding capacity determination using the Langmuir isotherm and related transform equations. Langmuir and transform calculations further reveal the specific surface area covered by adsorbents for select nanocarbon materials. In addition. cyclic voltammetry measurements confirm that dye adsorbed onto NDs exhibits equal electrochemical properties as in its unbound state. (C) 2009 Elsevier B.V. All rights reserved.