Optical Sensing Scheme for Carbon Dioxide Using a Solvatochromic Probe
2011; American Chemical Society; Volume: 83; Issue: 8 Linguagem: Inglês
10.1021/ac200298j
ISSN1520-6882
AutoresReham Ali, Thomas Lang�, Sayed M. Saleh, Robert J. Meier, Otto S. Wolfbeis,
Tópico(s)Electrochemical sensors and biosensors
ResumoThe novel sensing scheme, unlike previous ones that are based on the use of pH indicator probes, is making use of solvatochromic probe Nile Red (NR). Dissolved in a matrix of ethyl cellulose, it can report the polarity of its microenvironment that is modulated by an additive (a hydrophobic amidine) that is capable of reversibly binding carbon dioxide. The spectra of NR undergo a strong solvatochromic shift both in color (from brick-red to magenta) and in fluorescence (from orange to red) if the respective sensor layer is exposed to gaseous CO2 (gCO2) or dissolved CO2 (dCO2). Both visual and instrumental readouts are possible. The sensor layer responds to gCO2 in the range from 0 to 100% and to dCO2 in the range from 0 to 1 M solutions of bicarbonate (equivalent to a CO2 partial pressure of up to 255 hPa). The detection limits are around 0.23% for gCO2 and 1.53 hPa for dCO2. The response time is in the order of 10 min in the forward direction and 3 min in the reverse direction for gCO2 but up to 25 min in the case of dCO2. The optical response also was quantified using a digital camera by extracting the spectral information using the blue and green color channels (in reflectometry) and the green and red channels (in fluorescence), respectively, and by generating pseudocolor pictures.
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