Optical Sensing Scheme for Carbon Dioxide Using a Solvatochromic Probe

Abstract

The 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 CO(2) (gCO(2)) or dissolved CO(2) (dCO(2)). Both visual and instrumental readouts are possible. The sensor layer responds to gCO(2) in the range from 0 to 100% and to dCO(2) in the range from 0 to 1 M solutions of bicarbonate (equivalent to a CO(2) partial pressure of up to 255 hPa). The detection limits are around 0.23% for gCO(2) and 1.53 hPa for dCO(2). The response time is in the order of 10 min in the forward direction and 3 min in the reverse direction for gCO(2) but up to 25 min in the case of dCO(2). 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.

Potential of volatile organic compounds as markers of entrapped humans for use in urban search-and-rescue operations

“…(a) 1015 (5) [117] (b) 854 (17) [118] (c) 589 (48) [119] (d) 775 (20) [33] (e) 480 (30) [48] (a) 0.5 ng×cm -2 ×min -1 (30) hand [33] • • (a) Bacterial metabolism of proteins in gut [42] (b) Bacterial metabolism of proteins in oral cavity [43,120] 90 (b) 408 ppm (Dallas) [140] (c) 390 ppm (Phenix) [141] (d) 469 ppm (Wrocław) [142] (e) 403-408 ppm (Portland) [143] Vehicle emissions, (a) 0.25% optical sensor [92] (b) 0.23% Solvatochromic probe [144] A NO 10102-43-9 7.7 (a) 24.5 ppb (Hong Kong) [145] (b) 11.7 ppb (A Coruna) [146] (c) 127/35 ppb (Seul) [147] vehicle exhaust (a) 6 ppb chemiresistor (PEDOT:PSS/TiO2) [148] (b) 5 ppb electrochemical (WO3/Pt) [149] (c) 18 ppb chemiresistor (WO3/Cr2O3) [150] (d) 3.6 ppb ICOS [151] (e) 0.03 ppb lase QCL [152] (f) 4 ppb electrochemical sensor [153] C CO 630-08-0…”

Luminescent films for chemo- and biosensing

“…[10][11][12] Actually, the majority of analytes especially metal ions and biological samples 2,3 usually exist in aqueous systems. [26][27][28] In the past several decades, it is preferable to develop luminescent films consisting of various kinds of luminophores and functional materials to overcome the drawbacks of luminescent probes in solution for chemo-/bio-sensing. In addition, the water-soluble probes in solution also exhibit some inborn shortcomings, impeding their extensive applications: (1) the solution-based luminescent platform is inconvenient to store and transport; 18,19 (2) the water-soluble probes cannot be recycled and used because they are not easily separated from the analytes in solution; [20][21][22] (3) the random disposal of these one-off probes leads to the reagent consumption and environmental pollution; 23,24 (4) for the biological samples (e.g., cells and tissue), the water-soluble probes might induce unexpected chemicals released from biological samples; 25 and (5) the water-soluble probes are difficult to be used for vapor/gas detection.…”

Sensitive colorimetric sensors for visual detection of carbon dioxide and sulfur dioxide

“…Newer types of CO2 sensors utilize secondary amines, amidines, guanidines, or in situ generated carbenes as liquid phase CO2 absorbent, in combination with a colorimetric or fluorescent indicator. [18][19][20][21][22][23][24][25][26] The mode of detection is dependent on the physical changes in the sensor media upon dissolution of CO2, such as viscosity, 18,19 pH or polarity 24,25 .…”