(KEY WORDS: Optical sensors, biosensors, fiber optics, dyes, fluorescence, probes, environmental analysis, process control)

From the successful combination of chemical and technological advances in molecular engineering, photochemistry, analytical spectroscopy, material science, optoelectronics and information technology, the current fiberoptic chemical and biochemical sensors have been born. Such tools are versatile devices capable of real time, comtinuous, in-situ monitoring of concentration level of chemical parameters of interest to the environmental, process control and biomedical areas.


Fiberoptic luminescent sensor manufactured at Universidad Complutense

The optoelectronics instrumentation that uses a fiber-optic chemical sensor consists of a light source, the radiation of which (usually selected in wavelength) is launched into the core of an optical fiber. The waveguide carries the light to the sensitive tip, -the true ‘heart’ of the device-, that contains a specific indicator molecule (reagent material) immobilized onto a polymer support. Upon (selective) interaction with the target analyte species, an optical property (absorption, reflectance, fluorescence, refraction index,…) of the reagent material undergoes a measurable change. In this way, the modified light leaves the sensitive tip and is guided back through the optical fiber to a photonic transducer, the electrical signal from which is conveniently amplified and digitally recorded. An appropriate calibration using standard samples allows to carry out, in situ and continuously, the measurement of the target chemical species, provided the sensor-analyte interaction is reversible. In the case of a fiberoptic biosensor, the opto-chemical transducer located at the sensitive end is covered with an additional layer containing a biomolecule (enzime, antibody) or even a whole cell that is able to specifically recognize the target chemical species. As a consequence of the biomolecule-analyte interaction, a chemical reaction occurs with the result of production/consumption of the species that the opto-chemical transducer is designed to monitor.


Basic components of a fiberoptic chemical sensor (F: wavelength selectors; D: photonic detector). An oxygen-sensitive fluorescent indicator material is depicted in the microphotography. A scheme depicting how dissolved oxygen is measured using fluorescence quenching of the (immobilised) indicator molecule is included on the left of the figure

Only by preparing luminescent or colorimetric dyes, molecularly engineered in our laboratory to tailor the specific application sought by the customer, and using the most advanced opto-electronics, developed by a partner company, it is possible to fabricate fiber optic chemical sensors adapted to the particular features of the monitoring requirement. Moreover, our labs are equipped to carry out a thorough analytical characterization and calibration of the novel devices, including state-of-the-art laser and spectroscopic techniques. Some advantages of fiber-optic sensing of chemical species vs. conventional devices include unnecessary additional reference devices, lack of electrical/magnetic interferences or risks, easy miniaturization, feasibility of transporting a higher information density, competitive cost and toughness, as well as the possibility of monitoring chemical species for which there are currently no other sensors available. No doubt such features are bound to produce a quantitative shift of the present technology in fields as disparate as environmental quality monitoring (water, air, soils), industrial process control, food and storage industry, aerospace, biotechnology and clinical chemistry among other fields where in situ real-time quantification of chemical species is a must.

 Several UCM’s fiberoptic oxygen sensors installed in a water treatment plant, a pilot composting unit and a laboratory fermentor

The Spanish UCM Laboratory of Applied Photochemistry and Optical Sensors Groups, together with industrial partners, offer more than 15-year know-how in the molecular engineering of luminescent and optical probes and their tailoring to fibre-optic chemical (bio)sensor development. The small size, toughness, safety and specificity of such devices make them ideal for in situ real-time control of the water or air quality, as well as on-line monitoring of key chemical species in industrial processes. Our research group is able to offer the following products/services:

  • Development of specific sensors or biosensors for in situ, continuous monitoring of chemical parameters based on optical fiber technology.
  • Design, synthesis and photochemical characterization of optical indicator dyes for measuring chemical parameters of enviornmental, industrial of biotechnological interest.
  • Tailored fluorescent labels for quality control, tracers and molecular biology (nucleic acids, proteins, intact cells).
  • Development and testing of spectroscopic and photochemical methods for chemical, biochemical or biological analysis.
  • Turn-key application of fiberoptic chemical and biochemical sensors for monitoring water/air quality para meters or process control .


 The instrument has been developed jointly by Aqualogy, Cetaqua and the UCM Optical Chemical Sensors / Laboratory of Applied Photochemistry group


Prof. Guillermo Orellana / Prof. María C. Moreno-Bondi Organic Chemistry Department / Analytical Chemistry Department Faculty of Chemistry
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