Scientists made a tiny chip that can spot unbelievably tiny amounts of copper ions in water by coating it with the GHK peptide. The chip changes its electric signal when copper binds to the GHK, letting it detect copper down to a quadrillionth of a mole. They showed it works in tap water and can be reset with EDTA.

Artificial solid-state nanochannels have garnered considerable attention as promising nanofluidic tools for ion/molecular detection, DNA sequencing, and biomimicry. Recently, nanofluidic devices have emerged as cost-effective detection tools for heavy metal ions by modifying stimuli-responsive materials. In this work, high-purity glycyl-l-histidyl-l-lysine (GHK) peptide is synthesized by using 7-diphenylphosphonooxycoumarin-4-methanol (DPCM) as a protecting group and auxiliary carrier by homogeneous synthesis of photocleavable groups. Subsequently, we developed a GHK-modified asymmetric nanochannel nanofluidic diode by covalently attaching the GHK peptide to the inner surface of the nanochannels. This modification facilitated specific recognition and ultra-trace level detection of Cu²⁺ ions, achieving a detection limit of 10^-15 M. Due to the robust complexing ability between Cu²⁺ and GHK peptide, the GHK-modified asymmetric nanochannels can form GHK-Cu complexes on the inner surface of nanochannels when Cu²⁺ passes through the nanochannels. This results in changes of current-potential (<i>I</i>-<i>V</i>) properties, which facilitated Cu²⁺ detection. Theoretical calculations confirmed the high affinity of the GHK peptide for Cu²⁺, thereby ensuring excellent Cu²⁺ selectivity. To evaluate the applicability of our system for detecting Cu²⁺ in real-world scenarios, we analyzed the concentration of Cu²⁺ in tap water. The GHK-Cu complexes could be dissociated by adding EDTA to the solution, enabling the regeneration and reuse of this ultrasensitive and label-free Cu²⁺ detection system using GHK-modified asymmetric multi-nanochannels. We anticipate that the GHK-modified asymmetric nanochannels will find future applications in the label-free detection of Cu²⁺ in domestic water.