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J Am Chem Soc

Title:		Large-scale resonance amplification of optical sensing of volatile compounds with chemoresponsive visible-region diffraction gratings
Author(s):		Bailey RC; Hupp JT;
Address:		"Department of Chemistry, Materials Research Center and Center for Nanofabrication and Molecular Self-Assembly, Northwestern University, Evanston, Illinois 60208, USA"
Journal Title:		J Am Chem Soc
Year:		2002
Volume:		124
Issue:		23
Page Number:		6767 - 6774
DOI:		10.1021/ja0177354
ISSN/ISBN:		0002-7863 (Print) 0002-7863 (Linking)
Abstract:		"Micropatterning of the vapochromic charge-transfer salt, [Pt(CNC6H4C10H21)4][Pd(CN)4], on transparent platforms yields transmissive chemoresponsive diffraction gratings. Exposure of the gratings to volatile organic compounds (VOCs) such as chloroform and methanol leads to VOC uptake by the porous material comprising the grating lattice or framework, and a change in the material's complex refractive index, n. The index change is accompanied by a change in the degree of index contrast between the lattice and the surrounding medium (in this case, air), and a change in the diffraction efficiency of the grating. When a monochromatic light source that is not absorbed by the lattice material is employed as a probe beam, only changes in the real component of n are sensed. Under these conditions, the grating behaves as a nonselective, but moderately sensitive, sensor for those VOCs capable of permeating the porous lattice material. When a probe color is shifted to a wavelength coincident with the vapochromic charge-transfer transition of the lattice material, the sensor response is selectively amplified by up to 3.5 orders of magnitude, resulting in greatly enhanced sensitivity and some degree of chemical specificity. On the basis of studies at four probe wavelengths, the amplification effect is dominated by resonant changes in the imaginary component of the refractive index. The observed wavelength- and analyte-dependent amplification effects are quantitatively well described by a model that combines a Kramers-Kronig analysis with an effective-medium treatment of dielectric effects"
Keywords:
Notes:		"PubMed-not-MEDLINEBailey, Ryan C Hupp, Joseph T eng 2002/06/06 J Am Chem Soc. 2002 Jun 12; 124(23):6767-74. doi: 10.1021/ja0177354"