Synthesis and optical behaviors of novel triazole fluorescent probes involving solvatochromic behavior, metal ions detection and their antibacterial activity
Clean drinking water and effective antibiotics are two pillars of public health that are under increasing pressure from industrial pollution and drug‑resistant microbes. This study introduces two newly designed glowing dye molecules—called fluorescent probes—that can both help detect harmful metal ions in water at very low levels and strongly slow the growth of dangerous bacteria. By combining simple color changes with light emission, these tiny chemical tools offer a glimpse of future materials that could monitor contamination and fight infections at the same time.
Designing new glow-in-the-dark helpers
The researchers built two related molecules, referred to as probe 1 and probe 2, by linking a vivid “azo” dye unit (responsible for strong color) with a triazole ring known to latch onto metal ions. Each probe also carries an extra group—one based on quinoline and the other on hydroxybenzoic acid—that tunes how the molecule absorbs and emits light. The team confirmed the exact structures using standard techniques that read out bond vibrations, nuclear environments, and fragment masses. Together, these tests showed that the intended architectures were obtained and that the probes were stable enough to be studied in detail.
Colors that shift with their surroundings Figure 1.
When the probes were dissolved in liquids ranging from oily to highly polar, their colors and glow shifted noticeably. In some solvents, the main light-absorbing band moved to longer wavelengths (a red shift), while in others it moved to shorter ones (a blue shift). These “solvatochromic” effects reveal how the electrical charge within each probe redistributes when it is excited by light. Careful analysis showed that, in the excited state, the molecules become more polarized: charge is pushed from one end of the structure to the other through the azo bridge. This behavior is important because it makes the probes highly sensitive to changes in their environment, a key requirement for good chemical sensors and for potential use in advanced optical materials.
Spotting metals in water by light and color
The central aim was to see whether these glowing dyes could flag specific metal ions in water-like conditions. The team mixed each probe with common ions such as sodium, magnesium, iron, copper, zinc, cadmium, mercury, barium, and cobalt, then monitored how the color and fluorescence changed. Many ions altered the light signals, but cobalt ions stood out sharply. Both probes formed strong complexes with cobalt, which led to large and characteristic shifts in absorption and emission. Mathematical fits of the data showed especially high binding strengths for cobalt compared with the other metals. From how the glow intensity changed with cobalt concentration, the authors calculated detection limits of about 0.58 micromolar for probe 1 and an even lower 0.06 micromolar for probe 2—well below safety thresholds for drinking water set by international agencies.
Fighting stubborn bacteria with the same molecules Figure 2.
Beyond sensing metals, the probes were tested against three clinically important bacteria, including multidrug‑resistant strains of Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Using standard plate tests, the researchers placed small amounts of each probe into wells on bacteria‑covered agar and measured the clear zones where growth was halted. Both probes produced larger inhibition zones than the widely used antibiotic ciprofloxacin under the test conditions, with probe 2 giving the strongest effect, especially against Klebsiella. While these experiments are preliminary and do not yet reveal how the molecules act inside cells or how safe they would be for human use, they suggest that the same structural features that grab metals and redistribute charge may also disturb vital processes in bacteria.
Where this research could lead
In essence, this work shows that carefully engineered fluorescent dyes can serve double duty: as highly sensitive, cobalt‑selective water‑quality indicators and as promising starting points for new antibacterial agents. The probes change color and brightness in a way that is easily monitored, and they detect cobalt at concentrations far below regulatory limits, making them attractive for environmental monitoring. At the same time, their strong action against hard‑to‑treat bacteria hints at possible therapeutic applications, provided future studies clarify their safety, stability, and detailed mode of action. These glowing molecules thus highlight how smart chemical design can bridge environmental sensing and biomedical defense in a single class of materials.
Citation: Elkholy, H.M., Hamada, W.M. & El-Nahass, M.N. Synthesis and optical behaviors of novel triazole fluorescent probes involving solvatochromic behavior, metal ions detection and their antibacterial activity.
Sci Rep16, 11663 (2026). https://doi.org/10.1038/s41598-026-41364-y
Keywords: fluorescent probes, cobalt detection, solvatochromism, water quality, antibacterial materials
