Fluorescence quenching based detection of p-nitrophenol using luminescent silicon nanocrystals and insights into the quenching mechanism

We demonstrate a simple, rapid, selective and sensitive method for the detection of p-nitrophenol (pNP) using luminescent colloidal silicon nanocrystals (Si NCs). Aqueous suspension of green luminescent Si NCs was prepared at room temperature by simultaneous hydrolysis and redox reaction of (3-aminopropyl)triethoxysilane (APTES) in a remarkably simple one-step method. Trace addition of pNP significantly quenched the luminescence of the Si NCs and the quenching was found to be linearly dependent on the pNP concentration in the range of 0–20 μM of pNP in solution. Beyond 20 μM pNP concentration the quenching varied exponentially. Analysis of steady state absorption and emission, along with photoluminescence decay dynamics revealed that formation of ground state complexes (static quenching) and primary inner filter effect played a combined role in affecting quenching at relatively lower concentration range (0–20 μM); whereas both static and dynamic quenching came into effect at concentrations above 20 μM. Finally, we demonstrate a simple, pH-paper-type sensor based on Si NC coated filter paper and aluminium tape, for detection of aqueous as well as airborne pNP.