Unique Organic-Inorganic Hybrid Copper(I) Phosphate with Ultralow Ractopamine Detection Limit and In Situ Sensing Ability

Abstract

We successfully synthesized and characterized the first-ever organic-inorganic hybrid metal phosphate, NTOU-10, featuring lower-valence copper nodes under hydrothermal conditions. The crystalline structure, confirmed through single-crystal X-ray diffraction, thermogravimetric analysis, solid-state NMR spectroscopy, X-ray photoelectron spectroscopy, and bond valence-sum calculations, revealed its chemical composition, and unique coordination bonding models between organic linkers, metal nodes, and phosphate groups. These building blocks intricately bonded through metal-oxygen and metal-nitrogen linkages to form a highly complex crystalline structure. Taking innovation a step further, we polymerized NTOU-10 with pyrrole to develop the hybrid NTOU-10@polypyrrole (PPy) electrode, setting a groundbreaking record with an ultrasensitive limit of detection (LOD) of 3.31 x 10-19 M for ractopamine (RAC) sensing, surpassing existing crystalline materials by more than 9 orders of magnitude. The real-world effectiveness of this biosensor was demonstrated by detecting RAC in spiked pork samples. Additionally, we integrated the NTOU-10@PPy electrode into a flow injection analysis (FIA) system, offering advantages such as rapid detection, minimal sample requirement, and operational convenience. This work presents a significant leap forward in the design and synthesis of novel materials, along with the development of a high-performance biosensing platform for RAC detection.