Revolutionizing scandium detection in real samples: Unleashing the power of sol-gel-based optical sensor

The development of a highly selective and ultra-sensitive optical sensor for detecting scandium (Sc³⁺) ions involves incorporating the reagent 2,3-dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline (DCHNAQ) into a silica sol-gel thin film on a glass substrate. This innovative approach utilizes tetraethoxy-silane (TEOS) as the precursor, maintaining a sol-gel pH level of 4.5, a water-to-alkoxide ratio of 5:1, and a DCHNAQ concentration of 5.0 × 10^-4 M. A detailed exploration of the impact of sol-gel parameters on the sensing capabilities of the developed sensor has been meticulously undertaken. This innovative sensor demonstrates remarkable selectivity in evaluating Sc³⁺ ions over a dynamic range of 7.5-170 ng/mL, with limits of quantification and detection recorded at 7.3 and 2.20 ng/mL, respectively. Consistent results are achieved with a minimal RSD of 1.47 and 0.94% for Sc³⁺ ions at 50 and 100 ng/mL, respectively, coupled with a swift response time of three min. Assessments of interference demonstrate a noteworthy preference for Sc³⁺ions, accomplished by enclosing DCHNAQ within the sol-gel framework and making optimal structural modifications to the doped sol-gel. The sensor offers straightforward regeneration using a 0.25 M EDTA solution, exhibiting complete reversibility. Comparative analysis with other methodologies underscores the efficacy in determining Sc³⁺ions in various reference materials, including plant leaves, fish, water, alloys, ores, and monazite samples.