Sensing humidity using phage-nanoparticle assembly
C. Mao, A. Liu, G. Abbineni
University of Oklahoma, US
Keywords: phage, gold nanoparticles, layer-by-layer assembly, humidity sensing
Abstract:The height of a filamentous phage particle lying on a substrate has been found to be sensitive to humidity in the environment. When the environmental humidity is reduced, the phage particle will tend to be flattened. The UV-Visible spectra of gold nanoparticles are sensitive to the inter-particle spacing due to the localized surface plasmon resonance (SPR) effect. When the nanoparticle spacing is reduced, the SPR absorption band will be red-shifted. In this work, we exploited these two phenomena to develop a phage-based humidity sensor. Toward this end, we prepared a phage-nanoparticle film through the layer-by-layer assembly of cationic filamentous M13 phage particles (displaying a positively charged peptide on the major coat) and anionic spherical gold nanoparticles. We found that the UV-Visible spectra of the phage-nanoparticle nanocomposite films were sensitive to the environmental humidity. In air, both λmax and peak absorbance of the UV-Visible spectra of the nanocomposite films are linearly dependent on the environmental humidity. We also found that the humidity sensing is rapid and reversible. The humidity-tunable absorption band shift indicates that the nanocomposite films layer-by-layer-assembled from phage and gold nanoparticles can be used as a humidity sensor.