{"id":171703,"date":"2025-11-28T18:00:17","date_gmt":"2025-11-29T00:00:17","guid":{"rendered":"https:\/\/tecscience.tec.mx\/en\/?post_type=sciencecommunication&p=171703"},"modified":"2025-12-02T18:30:48","modified_gmt":"2025-12-03T00:30:48","slug":"chemical-indicators","status":"publish","type":"sciencecommunication","link":"https:\/\/tecscience.tec.mx\/en\/science-communication\/chemical-indicators\/","title":{"rendered":"Chemical Stoplights: How Molecular Sensors Detect Invisible Threats"},"content":{"rendered":"\n

By<\/em> Iv\u00e1n J. Bazany-Rodriguez, Jessica M. Muro-Hidalgo, Axel Macias-Garc\u00eda, J. Guadalupe Hern\u00e1ndez-Hern\u00e1ndez, Carlos Alberto Huerta-Aguilar<\/a> y Pandiyan Thangarasu<\/em><\/p>\n\n\n\n

How can we tell whether the water we drink contains invisible contaminants\u2014or whether a medical sample carries biomolecules linked to disease?<\/p>\n\n\n\n

In chemical sciences, several techniques can detect these substances, including one known as photoluminescence spectrophotometry.<\/strong><\/p>\n\n\n\n

These instruments rely on molecular sensors\u2014called chemosensors and chemodosimeters\u2014which are synthetic compounds that react when they encounter another chemical, such as a contaminant or a biomolecule. When that reaction occurs, the sensor undergoes a change in its physicochemical properties.<\/p>\n\n\n\n

If that change involves an optical property, such as light emission, the molecular sensor is considered photoluminescent.<\/p>\n\n\n\n

Scientific literature has documented a variety of photoluminescent sensors containing metal ions\u2014such as zinc, copper, aluminum, palladium, platinum, iridium, and ruthenium\u2014that react with specific target compounds.<\/p>\n\n\n\n

In our research on detecting amino acids<\/a>, ions<\/a>, and pesticides<\/a>, we work with photoluminescent sensors derived from ruthenium ions (Ru\u00b2\u207a, Ru\u00b3\u207a). These sensors can detect trace amounts of compounds that are essential to the food industry, environmental monitoring, and disease diagnostics.<\/p>\n\n\n\n

Ruthenium Sensors: How They Work<\/strong><\/h2>\n\n\n\n

Photoluminescent sensors based on Ru\u00b2\u207a and Ru\u00b3\u207a exhibit strong absorption and visible-light emission bands. They\u2019re also highly stable in water and under light exposure, making them strong candidates for detecting substances in aqueous environments.<\/p>\n\n\n\n

For example, we\u2019ve found that Chemosensor I<\/strong>\u2014a Ru\u00b3\u207a compound that dissolves in water at neutral pH\u2014normally emits blue light (photoluminescence). However, when it detects the insecticide parathion<\/a>, that blue emission almost completely switches off.<\/p>\n\n\n\n

Detecting this contaminant is critical because it is extremely toxic to humans, fish, and amphibians\u2014even at very low concentrations. So if there\u2019s reason to suspect that a water sample contains this pesticide, adding the ruthenium sensor will cause it to dim instead of glowing bright blue, signaling the contaminant\u2019s presence.<\/p>\n\n\n\n

We\u2019ve also found that Chemosensor II<\/strong>, which contains a Ru\u00b2\u207a ion and emits blue light, can detect bisulfate and acetate<\/a>\u2014ions whose presence and concentration are important in biochemical and industrial processes. This detection occurs through a photoluminescent Off\u2013On mechanism, meaning the sensor\u2019s light intensity increases when it encounters these substances.<\/p>\n\n\n\n

Finally, we have also found that Chemodosimeter I<\/strong> can detect selenocysteine, an amino acid linked to diseases such as cancer and diabetes, making its monitoring useful for diagnosing metabolic disorders.<\/p>\n\n\n\n

This sensor, which combines a Ru\u00b2\u207a ion with a photoluminescent dye that emits green light, reacts by producing a brighter green glow when it detects the amino acid<\/a>.<\/p>\n\n\n\n

\r\n \r\n \"\"\r\n <\/picture>
Proposed detection mechanisms for several photoluminescent chemosensors and chemodosimeters derived from ruthenium (II\/III) ions, as reported in the scientific literature:
A) Chemosensor I:<\/strong> An On\u2013Off sensor designed to detect parathion, a highly toxic insecticide.
B) Chemosensor II:<\/strong> An Off\u2013On sensor capable of sequentially detecting bisulfate and acetate\u2014anions relevant to biochemistry, the pharmaceutical industry, and the food industry.
C) Chemodosimeter I:<\/strong> An Off\u2013On sensor used to detect selenocysteine, an important biological marker for diagnosing diseases such as cancer and diabetes.<\/em><\/figcaption><\/figure>\n\n\n\n

.<\/p>\n\n\n\n

The Future of Molecular Sensors<\/strong><\/h2>\n\n\n\n

These molecular detection tools are essential to modern life, making it increasingly important to develop new sensors capable of identifying substances that threaten human health and the environment.<\/p>\n\n\n\n

In the years ahead, this technology will also be used to track emerging contaminants in air and water supplies\u2014including residues from new pharmaceuticals, pesticides, and agrochemicals\u2014and even to detect biological markers linked to emerging diseases.<\/p>\n\n\n\n

\r\n \r\n \"\"\r\n <\/picture>
There are two types of molecular sensors: chemosensors and chemodosimeters. The difference between them lies in how they interact with a target substance. Chemosensors bind to it reversibly, while chemodosimeters form an irreversible bond. Both generate a light-emission signal when they react with a specific substance. In some cases, that light emission becomes more intense\u2014an effect known as an \u201cOff\u2013On\u201d response. Conversely, in an \u201cOn\u2013Off\u201d system, the light signal dims or even disappears entirely. Some sensors can also signal the presence of a substance by shifting the color of the emitted light.<\/em><\/figcaption><\/figure>\n\n\n\n

.<\/p>\n\n\n\n

Authors<\/strong><\/p>\n\n\n\n

Iv\u00e1n J. Bazany-Rodr\u00edguez.<\/strong> Postdoctoral researcher at UNAM\u2019s Faculty of Chemistry and lecturer at UNAM\u2019s Faculty of Sciences. He holds a PhD in Chemical Sciences and specializes in designing and fabricating artificial optical receptors for photoluminescent chemodetection of organic contaminants, toxic ions, and biological markers relevant to diseases such as cancer and diabetes.<\/p>\n\n\n\n

Jessica M. Muro-Hidalgo.<\/strong> Chemical Engineer with a Master\u2019s in Environmental Engineering from UNAM. She has developed photoluminescent nanosensors for the chemodetection of toxic metal ions and biogenic amines like histamine, using carbon quantum dots derived from waste materials such as PET. She is currently pursuing a PhD in Environmental Engineering (UNAM), focusing on metal-oxide composite nanomaterials and carbon quantum dots for the detection and adsorption of carbon dioxide.<\/p>\n\n\n\n

Axel Macias-Garc\u00eda.<\/strong> Environmental Engineer trained at the National Technological Institute of Mexico with a Master\u2019s in Environmental Engineering from UNAM. His work includes electrocoagulation projects for arsenic removal at the Mexican Institute of Water Technology, phenol removal through Fenton processes at CIDETEQ, and electrochemical detection of pesticides using nanostructured electrodes at UNAM\u2019s Faculty of Chemistry. He is now pursuing a PhD in Environmental Engineering, focused on developing nanomaterials for the electrochemical detection of environmentally and medically relevant molecules.<\/p>\n\n\n\n

J. Guadalupe Hern\u00e1ndez-Hern\u00e1ndez.<\/strong> Academic technician and lecturer at UNAM\u2019s Arag\u00f3n School of Higher Studies. He holds a PhD in Chemical Engineering, with research lines in inorganic chemistry, computational chemistry, photocatalysis, and electrochemistry.<\/p>\n\n\n\n

Carlos Alberto Huerta-Aguilar.<\/strong> Professor at Tecnol\u00f3gico de Monterrey. He holds a PhD in Environmental Engineering and specializes in solar-driven catalysis, waste valorization, and circular chemistry. He completed postdoctoral work at Stanford and Texas A&M and co-leads international projects on hydrogen, biogas, and agrivoltaics. He has also contributed to TecScience as a science communicator<\/a>.<\/p>\n\n\n\n

Pandiyan Thangarasu.<\/strong> Senior researcher and professor at UNAM\u2019s Faculty of Chemistry. He holds a PhD in Chemistry. His research focuses on coordination chemistry, catalytic systems, and green remediation strategies. He is recognized for his work on metal\u2013organic complexes and advanced oxidation technologies, with collaborations across Latin America and Asia. He is also a contributor of science outreach articles for TecScience<\/a>.

<\/p>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

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