Refractive Index versus Coupling Effects for Naked and Surfactant-coated Au NP Films:Implications for Selective Detection of Vapor−Liquid Analytes

M. CELESTE DALFOVO; CHRISTIAN D´AMBROSIO; DAVID MUÑETÓN ARBOLEDA; LUSINA SCARBOL; FIONA M. BRITTO; MARCELO LESTER; DIANA SKIGIN; FRANCISCO J. IBAÑEZ

ACS Applied NanoMaterials

American Chemical Society

Año: 2021

2050-7534

From a single dispersion of surfactant-coated Au nanoparticles (NPs), we can assemble colorimetric films of different thickness, organic content, and structure. In this work, we demonstrate how these variables play a fundamental role in determining what sensing mechanism predominates when thesefilms are subjected to liquid-phase ethanol (EtOH), acetone (Ace), and toluene (Tol) analytes. Theoretical calculations, performed with the Korringa−Kohn−Rostoker (KKR) model, agree very well with the experiments if we consider that thinner films with lesser organic/inorganic content (or no organic at all) offer more vacancies for the solvents to partition, leading to effective changes in the permittivity. Instead, thicker films with a more compacted structure suffer minimal changes in the effective permittivity (lesser vacancies), causing color changes dominated by changes in the distance between the Au NPs. These films may be incorporated into a sensor array for improving selectivity toward the detection of vapor/liquid-phase analytes.