In a study published in the journal ACS Applied Nano Materials, a straightforward, quick, and easy approach was used to create hydrogel-based optical fiber sensors for ethanol detection.
Study: Nanostructured Photonic Hydrogels for Real-Time Alcohol Detection. Image Credit: Firn/Shutterstock.com
The proposed sensing devices might be used for distant and real-time ethanol detection in forensics, healthcare, the production of food items and beverages, and other sectors.
Fiber Optic Sensors Paired with Hydrogels
Fiber optic sensors provide a number of unique advantages, including distant detection, EM immunity, and simplicity of use. For real-time and continual bioindicator surveillance, fiber optics paired with functional hydrogels may enable distant detection and quick response.
Hydrogels are 3D polymeric chains linked together by cross-linking physically or chemically. Since they are cyto-compatible and soft, they may be used in activities like as delivery of drugs and tissue development. Another significant benefit of hydrogel-based detectors is their high molecular permeability. This means that stimulus-sensitive substances may be used to functionalize them.
These stimulus-sensitive hydrogel substances may alter their volume under the influence of extrinsic stimuli, including electric field, heat, glucose, humidity, acidity, and alcohol. This distinguishing feature of stimulus-sensitive hydrogels makes them an attractive choice for a wide range of sensory purposes.
Sensors for Ethanol Detection
The demand for quick, responsive, and dependable ethanol detectors is critical in various sectors, such as forensics, healthcare, and the food and drinks production industry. Detecting ethanol is crucial among various other alcohols since it is among the most widely utilized in foodstuffs, drinks, and medication.
Electrochemical detectors are a typical kind of sensing device employed for this very reason. Enzymes including alcohol oxidase and alcohol dehydrogenase are fundamental components of such sensing systems. Ethanol detectors based on hydrogels have also been described in the literature.
In one research study, for example, a polyacrylamide hydrogel-based detector with high sensitivity for ethanol was developed. When exposed to varying ethanol levels, the hydrogel expanded, exerting pressure on the pressure detector and causing its voltage output to alter.
The hydrogel-based sensor demonstrated good responsiveness and a low detection limit (LOD). Its reaction time, though, was quite prolonged (90 minutes), and the sensor's response was not reproducible. Other investigations have also shown that electrochemical enzymatic detectors and optical sensing devices provide greater LODs and long-term durability.
Advantages of Using Aztec Microstructures
Aztec microscale structures were chosen to serve as optical actuators in this study due to two main reasons.
The Aztec structures demonstrated a large ratio of surface to volume, which helped to increase the active region of the detector and diffusion rate of the analyte, and ultimately the response speed.
Moreover, the diameters of the Aztec microstructures may be as much as hundreds of nanometers, rendering Aztec microstructures responsive to even tiny volume variations which may happen in the hydrogel, ultimately enhancing LOD and responsiveness.
The ethanol-responsive hydrogel was etched with Aztec structures and chemically bonded to a conventional SiO2 fiber optic. The fiber optic detector was examined in transmitting and reflecting modes for detecting ethanol, dimethyl sulfoxide (DMSO), methanol, and isopropanol. The created fiber optic sensors outperformed others with respect to responsiveness, reaction speed, LOD, and recyclability.
Key Findings of the Study
In this research, fiber optic sensors for alcohol were developed with extremely low detection limits. The sensing devices were created in a quick and straightforward manner, using a basic reading mechanism. An independent detector on a glass slide and a fiber optic detector with the fiber tip etched with hydrogel were produced.
The Aztec structures worked as optical actuators as light diffracting components, and readings for zero-order and first-order scattering areas were obtained in transmitting and reflecting arrangements.
The brightness of the first-order patches caused a rise in the scattering strength of the zero-order patch with alcohol and DMSO concentrations. In the concentration region of 0–50 percent volume, DMSO and three distinct alcohols, namely ethanol, methanol, and isopropanol were examined.
Irrespective of the alcohol consumed, a quick reaction time of 20 seconds was noted. All readings were entirely reproducible, and the fiber optic detectors performed consistently over a long period of time.
At small concentrations (0.5 percent volume) of DMSO and 1 percent volume of all other examined alcohols, fiber optic sensors, as well as stand-alone sensors, demonstrated good responsiveness. The optical fiber detectors produced showed good promise for distant, quick, real-time, and continuous detection of alcohol.
Reference
Ahmed, I., Elsherif, M., Park, S., Yetisen, A. K., & Butt, H. (2022). Nanostructured Photonic Hydrogels for Real-Time Alcohol Detection. ACS Applied Nano Materials. Available at: https://pubs.acs.org/doi/10.1021/acsanm.2c00576
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