Hydrogel-Based Plasmonic Sensor Substrate for the Detection of Ethanol

Abstract

The in-line monitoring of ethanol concentration in liquids is a crucial part of process monitoring in breweries and distilleries. Current methods are based on infrared spectroscopy, which is time-consuming and costly, making these methods unaffordable for small and middle-sized companies. To overcome these problems, we presented a small, compact, and cost-effective sensing method for the ethanol content, based on a nanostructured, plasmonically active sensor substrate. The sensor substrate is coated with an ethanol-sensitive hydrogel, based on polyacrylamide and bisacrylamide, which induces a change in the refractive index of the substrate surface. The swelling and shrinking of such hydrogels offer a means to measure the ethanol content in liquids, which can be determined in a simple transmittance setup. In our study, we demonstrated the capability of the sensor principle for the detection of ethanol content ranging from 0 to 30 vol% ethanol. Furthermore, we determined the response time of the sensor substrate to be 5.2 min, which shows an improvement by a factor of four compared to other hydrogel-based sensing methods. Finally, initial results for the sensor’s lifetime are presented.

Enzyme-Functionalized Piezoresistive Hydrogel Biosensors for the Detection of Urea

“…In addition to the long-term stability of these enzyme-functionalized hydrogels, another effect was also observed: Hydrogels were often conditioned before usage in sensing applications [20,43,44]. The polymer network finds their optimal arrangement and too short polymer chains break due to the conditioning process.…”

Soft Plasmonics: Design, Fabrication, Characterization, and Applications

“…The mechanoplasmonic properties of soft plasmonic structures can also be controlled using chemicals including organic solvents, [ 21,28,111 ] ionic salts, [ 18,112 ] and acids. [ 29 ] The underlying mechanisms differ for each chemical.…”

“…The most common systems are hydrogel‐based plasmonic systems. [ 18,21,29,111 ] The addition of chemicals may cause shrinkage or swelling of the hydrogel, which then results in enhanced/weakened plasmonic coupling. In a typical example, Au dimers have been embedded into a chitosan hydrogel film.…”

Critical-Angle Differential Refractometry of Lossy Media: A Theoretical Study and Practical Design Issues

“…Refractive index sensors are intensely investigated for numerous biomedical [1][2][3], chemical [4,5] and industrial [6,7] applications. An indicative yet far from exhaustive list of sensing mechanisms relies on plasmonic [8][9][10][11], photonic crystal [12][13][14][15], micro-cavity [16][17][18][19], optical fiber [20][21][22][23] and wave-guide [24][25][26][27] configurations. Associated with Fresnel reflectance properties at planar interfaces, differential refractometry offers an alternative path to sensing refractive index changes, by exploitation of interference [28], deflection [29] or (more relevant to the present work) critical-angle [30][31][32][33][34][35] effects.…”