β-Cyclodextrin protected gold nanoparticle based cotton swabs as an effective candidate for specific sensing of trace levels of cyanide†
In this paper, a rapid colorimetric and easy visual determination of cyanide ions (CN− ions) in water, based on gold nanoparticles (AuNPs) stabilized with β-cyclodextrin (β-CD), is described. Optical detection of CN− ions is carried out using β-CD-AuNPs by tracking the changes in the surface plasmon resonance band and colorimetric nature of the β-CD AuNPs. This colorimetric nanosensor easily and with ultra-sensitivity identifies the CN− ions because of their capacity to etch the surface of the β-CD AuNPs and form a stable water soluble Au–CN complex. Under experimental conditions, the colorimetric assay demonstrated a steady response for CN− ions over a concentration ranges from 4.50 × 10−6 to 99.00 × 10−6 mol dm−3 with R = 0.994. The lowest limit of detection of this inexpensive, visual with the naked eye, approach is 93.00 × 10−9 mol dm−3, which is under the tolerance limit value (1.90 × 10−6 mol dm−3) set by the World Health Organization for drinking water. The specificity of the β-CD-AuNPs based optical platform for the detection of CN− ions is superb when evaluated with various potential interfering anions. Furthermore, the proposed β-CD-AuNPs nanoprobe is effectively applied to quantify the CN− ions in tap and drinking water samples. For convenient use, a very stable cotton swab containing the β-CD-AuNPs has been designed and it revealed good sensitivity against CN− ions in the environment using the naked eye.