Gas Sensor Materials Based on Semiconductor Nanocrystal / Polymer Composite Films
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Gas Sensor Materials Based on Semiconductor Nanocrystal / Polymer Composite Films Andrew M. Leach and Radislav A. Potyrailo Chemical and Biological Sensing Laboratory, Materials Analysis and Chemical Sciences, General Electric Company, Global Research Center, Niskayuna, NY 12309, USA * Corresponding author: [email protected] ABSTRACT High-throughput screening experimentation and multivariate spectral data analysis has been applied to evaluate the gas sensitivity of multi-size CdSe nanocrystals embedded in multiple polymer matrices. We have found that when CdSe nanocrystals of different size (2.8 and 5.6 nm diameter) were incorporated into polymer films, the photoluminescence (PL) response patterns upon laser excitation at 407-nm and exposure to polar and non-polar solvents were unexpectedly different. Additionally, these response patterns were dependent on the nature of polymer. We analyzed the spectral PL response from both sizes of CdSe nanocrystals using multivariate analysis tools. Results of this multivariate analysis demonstrate that a single film with different size CdSe nanocrystals serves as a selective sensor. INTRODUCTION In sensing applications, nanomaterials bring previously unavailable capabilities [1-3] and unexpected results that are at times difficult to predict using existing knowledge [4-7]. We have found that when CdSe nanocrystals of different size (2.8 and 5.6 nm diameter) were incorporated into a polymer film, each size of CdSe nanocrystals unexpectedly demonstrated its own PL response pattern under a 407-nm laser excitation upon exposure to polar and nonpolar vapors [8]. In this study, we provide the details of multivariate analysis of the spectral PL response from both sizes of CdSe nanocrystals and demonstrate that a single film with different size CdSe nanocrystals serves as a selective sensor. In order to efficiently test the effects of different polymer matrices on the sensor performance of the CdSe nanocrystals, we applied spectroscopic high-throughput analysis tools that we have developed for screening of polymerization catalysts [9], automotive coatings [10,11], performance additives [12,13], and colorimetric sensor materials [14]. Our new sensor materials based on polymer-embedded semiconductor nanocrystal reagents of different size promise to overcome limitations of traditional organic reagent-based sensor materials (rapid photobleaching and short shelf-life). EXPERIMENTAL DETAILS Film preparation. CdSe nanocrystal solutions in toluene were prepared by a conventional process and were obtained from Evident Technologies (Troy, NY). Concentrations of 2.8 and 5.6-nm CdSe nanocrystals were 2.5 mg/mL. Sensor films were spin-cast from 5% vol. solutions of nanocrystals in polymer/toluene. Film thickness was measured using an interference microscope. Setup for high-throughput screening of photoluminescence. Multiple films with different polymers were arranged as a one-dimensional array. Automatic measurements of PL
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spectra of the sensor films array were p
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