Commercial Reagents-based Six-Mode Sensor: One-Step Detection of Iodide Ions without Enzymes or Nanomaterials

Multi-signal sensors possess immense potential for point-of-care testing, yet their widespread adoption is hindered by reliance on complex nanomaterial synthesis or fragile enzymatic systems. Herein, we propose a “six-in-one” multi-mode sensor for rapid iodide ion (I - ) detection, leveraging only three commercially available reagents: chloroplatinic acid (H 2 PtCl 6 ), hexadecyl trimethylammonium bromide (CTAB), and 3,3’,5,5’-tetramethylbenzidine (TMB). The core innovation lies in a dynamic “on-off-on” oxidation triggered by target I - ions as follows: H 2 PtCl 6 with strong oxidative capacity directly oxidizes TMB to its two-electron product (TMB 2+ ) (“On” State). CTAB coordinates with H 2 PtCl 6 thereby blocking its surface and completely inhibiting TMB oxidation (“Off” State). I - selectively displaces CTAB via competitive coordination, partially restoring H 2 PtCl 6 ’s oxidation activity to generate the one-electron product (TMBox) (“Reactivation” State). Remarkably, the resulting TMBox exhibits six distinct signal outputs including visual and fluorescent color, absorbance, fluorescence, temperature, and electrical current. Compared to conventional single- or dual-mode methods, our six-mode approach improves reliability of detection results. This “magic cube” signals enables dual-mode qualitative analysis and four-mode quantitative detection, achieving a nanomolar-level detection limit for I - detection. Critically, multi-mode sensor operates via one-step mixing without requiring nanomaterials, enzymes, or specialized equipment. We further demonstrate its utility in detecting I - in biological (urine, serum), food (iodized salt) and environmental (Yellow River water, tap water) samples with recovery rates of 96.3% - 110.0%. Statistical analysis demonstrated excellent reproducibility with relative standard deviations <3.1% across repeated measurements. This work redefines the paradigm of multi-mode sensing, offering a cost-effective, field-deployable solution for environmental monitoring and clinical diagnostics.