Alagumuthu Geetha, Gubendiran Bhuvaneshwari, Govindharajan Manikandan, Noorjahan Sheik Eusuff
Department of Chemistry, Guru Nanak College (Autonomous), Affiliated to University of Madras, Velachery, Chennai, Tamil Nadu, India.
Chemosphere. 2025 Oct;387:144683. doi: 10.1016/j.chemosphere.2025.144683. Epub 2025 Sep 12.
In this study, the purple onion skin extract (POSE), Allium Cepa L., was employed as a colorimetric biosensor for the distinctive detection of Fe and Fe ions in aqueous solution. The POSE changed its pink colour to green with Fe and brown with Fe in solution, which was also observed on POSE-loaded paper strips. POSE's colorimetric sensing of Fe and Fe ions was observed with the naked eye and analyzed by UV-Vis spectrophotometer. The resulting anthocyanin- Fe/Fe complexes were characterized by FT-IR, SEM-EDAX and XPS techniques. The anthocyanin content of POSE was analyzed using HPLC. The FT-IR has proved the formation of a stable complex between anthocyanin and Fe and Fe ions, the granular nature of the complex and its iron composition was ascertained by SEM-EDAX and Fe and Feoxidation states were confirmed by XPS analysis. The selective and sensitive complexation of POSE with Fe and Feions has reached a LOD of 0.1 ppm for both the ions. POSE's visible colour alteration is paired with smartphone RGB values for real-time Fe and Fe sensing with a LOD was valued down to 0.07 and 0.09 mg L respectively. The real-time analysis was done by spiking tap water with Fe and Fe ions with a LOD of 0.1 ppm with slight shift in λ. POSE exhibited a 68.65 % corrosion inhibition rate (I), confirming its corrosion inhibition potential. Hence, this rapid, green, and sustainable method adds value to onion peel (food industry waste) and supports SDG-6, Clean water and sanitation.
在本研究中，紫洋葱皮提取物（POSE），即葱属植物，被用作比色生物传感器，用于独特检测水溶液中的Fe²⁺和Fe³⁺离子。POSE在溶液中与Fe²⁺反应时粉色变为绿色，与Fe³⁺反应时变为棕色，在负载POSE的纸条上也观察到了这种现象。POSE对Fe²⁺和Fe³⁺离子的比色传感可通过肉眼观察，并通过紫外可见分光光度计进行分析。所得的花青素 - Fe²⁺/Fe³⁺络合物通过傅里叶变换红外光谱（FT - IR）、扫描电子显微镜 - 能谱分析（SEM - EDAX）和X射线光电子能谱（XPS）技术进行表征。使用高效液相色谱（HPLC）分析POSE中的花青素含量。FT - IR证明了花青素与Fe²⁺和Fe³⁺离子之间形成了稳定的络合物，通过SEM - EDAX确定了络合物的颗粒性质及其铁组成，通过XPS分析确认了Fe²⁺和Fe³⁺的氧化态。POSE与Fe²⁺和Fe³⁺离子的选择性和灵敏络合对两种离子的检测限均达到0.1 ppm。POSE的可见颜色变化与智能手机的RGB值相结合，用于实时检测Fe²⁺和Fe³⁺，检测限分别低至0.07和0.09 mg L⁻¹。通过向自来水中加入Fe²⁺和Fe³⁺进行实时分析，检测限为0.1 ppm，λ有轻微偏移。POSE表现出68.65%的缓蚀率（I），证实了其缓蚀潜力。因此，这种快速、绿色且可持续的方法为洋葱皮（食品工业废料）增添了价值，并支持可持续发展目标6，即清洁水和卫生设施。
