ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Development of an advanced flow injection method using curcumin nanoparticle fluorescence for sensitive detection of cobalt (II) and nitrite ions

Wafaa Waleed Al-Qaysi and Nagham Shakir Turkey

Department of Chemistry, College of Science, University of Baghdad, Baghdad, Iraq

E-mail: wafa.w@sc.uobaghdad.edu.iq

Received: 22 May 2025  Accepted: 7 October 2025

Abstract:

A simple chemical method based on pH-induced precipitation was used to prepare the fluorescent nanosensor (CURNPs), and it was thoroughly characterized. The nanosensor showed high sensitivity and selectivity toward the detection of Co (II) and NO₂⁻ ions in aqueous media. The fluorescence of CURNPs was excited with a 450 nm laser from an in-house-made fluorometer, and it exhibited detection limits in the nanogram range (1.842 ng/0.1 mL) within the calibration range of 0.1–18 μM (which represents a broad linear fit from 0.25 to 14 μM for native curcumin). The fluorescence ‘off–on’ mechanism was caused by quenching due to Co (II) ions and the subsequent recovery of fluorescence by NO₂⁻ ions via the formation of a yellow precipitate. This method enables the detection of NO₂⁻ in the range of 0.5–20 μM at the nanomolar level. For Co (II), the linear range of fluorescence quenching was 0.5–10 μM, and good linearity was obtained (R² = 99.84%, 95% confidence level). The LOD (S/N = 3) was 4.712 ng/mL, significantly much better than previously reported detection limits of conventional methods (58.933 ng/0.1 mL). The method showed high precision (RSD < 0.6%, n = 6) and high throughput (40 samples/hour), requiring only 125 μL per sample. Surface characterization via atomic force microscopy (AFM), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) confirmed successful nanoparticle formation, highlighting uniform particle size, defined morphology, and active functional groups. No significant interference from competing ions was observed, confirming high specificity. These findings establish CURNPs as a robust and efficient tool for environmental monitoring of Co (II) and NO₂⁻ ions. Statistical validation using a paired t test and the standard addition method showed no significant deviation (α = 0.05), confirming the nanosensor as a robust alternative for environmental and industrial analyses.

Keywords: Curcumin nanoparticles; Flow injection; Laser source; Co (II) ion determination; Quenching of fluorescence

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04434-5

Chemical Papers 80 (1) 853–872 (2026)