Nitrogen-terminated silicon nanoparticles obtained via chemical etching and passivation are specific fluorescent probes for creatinine.

A method is described here to prepare water-dispersible nitrogen-functionalized silicon nanoparticles (N-SiNPs). It consists of two steps, viz. etching of the oxidized shell of SiNPs and nitrogen-passivation of the exposed silicon. The resulting N-SiNPs have an average diameter of 2.6±0.7 nm and show blue fluorescence (with excitation/emission peaks at 340/420 nm). The fluorescence quantum yield is 23% and the decay time is in the nanosecond regime. Compared to etching methods using a plasma or hydrofluoric acid, the process described here (etching and passivation) is mild, continuous, fast, and air-compatible. The N-SiNPs modified with chlorotetracycline are shown to be a viable fluorescent probe for creatinine. Fluorescence drops in the 0 to 20 μM creatinine concentration range, and the limit of detection is 0.14 μM.