Polyethyleneimine protected silver nanoclusters luminescence probe for sensitive detection of cobalt (II) in living cells.

A simple luminescence sensor, based on polyethyleneimine protected silver nanoclusters (AgNCs@PEI) is successfully fabricated via one-pot reduction method. The obtained AgNCs@PEI are characterized by high-resolution transmission electron microscopy (HR-TEM), Dynamic light scattering (DLS), transient and steady-state fluorescence, and UV-vis spectroscopy. The NCs show large Stocks-shift (∼130nm), high tolerability to extreme pH and high ionic strengths, and excellent photo-stability under UV irradiation, laying the basement for the practical applications. In addition, the sensor is used to detect the Co basing on the luminescence quenching, which is interfered by pH conditions (from pH4.0 to pH7.4). As a luminescence probe for Co ions, the detection limit of AgNCs@PEI is as low as 0.25nM, which is much lower than that of many other reports. Additionally, the AgNCs@PEI possess the advantages of good selectivity, fast response and abroad linear detection. A linear response range in 0.5nM-50μM is achieved for Co when using 20μM AgNCs@PEI in BR buffer solution (neutral condition pH7.4). Incubation time of AgNCs@PEI toward Co is only 2min and it can distinguish Co from other 13 metal ions. Furthermore, the probe (AgNCs@PEI) is applied to sensing and imaging of HeLa cells, showing low cytotoxicity and good sensitivity.