Optical sensors have revolutionized the field of chemical analysis by providing a powerful and efficient method for detecting and quantifying a wide range of analytes by measuring the light absorption, reflection, or emission from the various types of samples and providing highly accurate and precise results. This article will explore the benefits of using optical sensors in chemical analysis, its applications, and recent developments.
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Optical Chemical Sensors
Optical sensors are a crucially significant group of analytical instruments that give chemical information regarding various topics, including molecular structure, microscopic imaging, and analyte concentration. Optical sensors use several signal transduction methods based on photonic attributes, including reflectivity, polarization, refractive index, fluorescence intensity, transmission, and absorbance.
Basic Components and Working
Optical chemical sensors are part of analytical systems that use optical transmission to accomplish chemical measurement by interacting with a chemical system and then converting the resultant optical signal into an electrical signal.
An optical chemical sensor has three basic components: a molecular recognition element, optoelectronic instrumentation, and optical fiber.
Molecular recognition elements that provide a response when the analyte is present are connected with optoelectronic instrumentation components using optical fibers as the integrating medium. These devices transmit information about chemical reactions by encoding it in an optical signal that moves across optical fibers.
Advantages of Optical Sensors in Chemical Analysis
Optical sensors can measure various analytes, including organic and inorganic compounds, and detect and quantify various chemical compounds, including drugs, biomolecules, explosives, and heavy metals. Optical sensors can also detect changes in the sample's physical and chemical characteristics, such as pH, temperature, and pressure, making them very flexible and suitable for various applications.
Fast and Real-time Analysis as Compared to Traditional Analytical Methods
Optical sensors allow fast and real-time analysis by providing results within seconds or minutes, significantly faster than traditional analytical methods like chromatography and spectroscopy, which is essential for many industrial and scientific applications. In addition, optical sensors can be used in situ, which means they can be deployed directly in the field, providing immediate analysis without sample preparation or transportation.
Non-Invasive and Non-Destructive Analysis
Compared to other analytical techniques, optical sensors are non-invasive and non-destructive, which means they can be used to analyze chemicals without damaging and measure them in situ without sampling or extraction. This makes optical sensors ideal for monitoring and analyzing live samples, such as cells, tissues, and organisms, without affecting their viability or function.
Moreover, optical sensors are compact portable, and scalable and can be used to analyze multiple samples simultaneously, providing cost-effective, fast, and efficient analysis, making them ideal for field and remote applications.
Recent Developments
Refractive Index (RI) Sensors
During the last two decades, refractive index (RI) sensors, including devices like resonant microcavities, photonic crystals, optical fibers, diffraction gratings, interferometers, and surface plasmon resonance instruments, have emerged as promising technologies within the larger category of optical sensors.
Based on the change in refractive index brought on by analyte attachment, the remarkable array of instruments used in optical sensors enables label-free molecular detection without the additional complication of fluorescent or enzyme tags.
Detecting Copper(II) in Drinking Water
Researchers created and tested an optical chemical sensor for detecting Copper(II) in drinking water in a study published in 2019. The researchers found that this novel sensor could detect Cu (II) at a broad concentration range after testing it with various concentrations of copper in NaCl 0.1 M solutions at different pH values. This optical, chemical sensor is ideal for low-cost, in situ, and fast detection of Cu(II) in drinking water, which would help reduce water-related health concerns.
Applications of Optical Sensors in Chemical Analysis
Optical sensors have a wide range of applications in chemical analysis, including environmental monitoring, food safety, healthcare, and more.
Environmental Monitoring and Food Safety
Optical sensors are often used in environmental monitoring to identify pollutants, contaminants, and dangerous compounds and track soil contamination, water quality, and air quality in real time. Similarly, optical sensors provide quick, non-invasive chemical analysis of food samples to ensure they adhere to regulatory requirements and are suitable for consumption.
Detecting Biomarkers and Disease-specific Molecules
Chemical analysis via optical sensors allows the detection of biomarkers and disease-specific molecules in blood, urine, and other bodily fluids, providing early and accurate diagnosis of diseases as well as helping monitor drug efficacy and toxicity, providing real-time and personalized treatment options for patients. Optical sensors are also used in medical imaging techniques, such as optical coherence tomography (OCT) and fluorescence microscopy, to provide high-resolution and non-invasive imaging of tissues and organs.
Future Prospects
Optical sensors have been used increasingly in chemical analysis in recent years, and this trend is projected to continue. Furthermore, as optical sensors may be used to monitor and control light at the nanoscale, they are predicted to be crucial in developing next-generation technologies like quantum computing and nanophotonics, in addition to their uses in chemical analysis.
Overall, the prospects for utilizing optical sensors in chemical analysis are positive, and in the years to come, they are anticipated to have a substantial influence on various industries and fields, such as pharmaceutical, food, and environmental monitoring.
References and Further Reading
Berhanu, A. L., Mohiuddin, I., Malik, A. K., Aulakh, J. S., Kumar, V., & Kim, K. H. (2019). A review of the applications of Schiff bases as optical chemical sensors. TrAC Trends in Analytical Chemistry. doi.org/10.1016/j.trac.2019.04.025
Luchansky, M. S., & Bailey, R. C. (2012). High-Q optical sensors for chemical and biological analysis. Analytical chemistry. doi.org/10.1021%2Fac2029024
Pesavento, M., Profumo, A., Merli, D., Cucca, L., Zeni, L., & Cennamo, N. (2019). An optical fiber chemical sensor for the detection of copper (II) in drinking water. Sensors. doi.org/10.3390/s19235246
Sevilla III, F., & Narayanaswamy, R. (2003). Optical chemical sensors and biosensors. Comprehensive Analytical Chemistry, 39, pp. 413-435. https://www.sciencedirect.com/science/article/abs/pii/S0166526X03801149
Wang, X. D., & Wolfbeis, O. S. (2019). Fiber-optic chemical sensors and biosensors (2015–2019). Analytical chemistry. Available at: http://www.wangslab.com/uploadfiles/2020/05/202005201112261226.pdf
You, L., Zha, D., & Anslyn, E. V. (2015). Recent advances in supramolecular analytical chemistry using optical sensing. Chemical reviews. doi.org/10.1021/cr5005524
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