Ultra-sensitive direct detection of silver ions via Kelvin probe force microscopy

• We sensitively detected the silver ions as one of the most hazardous metal pollutants.
• We used DNA–metal interaction (Cytosine–Ag+–Cytosine) to capture the silver ion.
• Kelvin probe force microscope shows high performance for silver ion detection.
• The sensor shows the potential for detection of nanotoxic material in real sample.

Nanotoxicity is receiving great importance due to its potential impact on human health and environment and due to rapid development in the field of nanoscale research and industry. Herein, we report the Kelvin probe force microscope (KPPM)-based nanotoxicity material detection using surface potential difference. In general, it is difficult to measure the size of ion (Ag+) using a conventional atomic force microscope (AFM) because of the limited resolution. In this study, we have demonstrated that KPFM is capable of ultra-sensitive detection of silver ion with silver specific DNA by a single droplet. Furthermore, the measured surface potentials for Ag+ and DNA binding enable the detection performance for a practical sample that is general drinking water. Remarkably, the KPFM based silver ion detection enables an insight into the coordination chemistry, which plays an important role in early detection of toxicity. This implies that KPFM based detection system opens a new avenue for water testing sensor.