ydrogen cyanide (HCN) vapor is extremely dangerous to human beings and animals as it inhibits the consumption of oxygen by body tissues [1], [2] and [3]. For example, exposure levels of 100 ppm HCN will result in death in about 1 h or less in some cases, while exposure levels of 500 ppm HCN will result in death within 15 min [4]. Higher concentration levels will result in faster onset of symptoms or death. Approaches to analyze HCN include spectrophotometric, atomic absorption spectrophotometric and electrochemical methods [5] and [6]. The spectrophotometric analysis of HCN has been widely known, which uses pyridine–pyrazolone, isonicotinic acid–pyrazolone and pyridine–barbituric acid as ligand. Although it is sensitive, the analysis procedure is complicated and time-consuming. The atomic absorption spectrophotometric method is sensitive, stable and easy in operation. However, it uses large apparatuses that are not available for sensing applications. Thus, neither spectrophotometric nor atomic absorption spectrophotometric methods are suited for fast in situ and real time detection. The electrochemical method uses a cyanide ion-selective membrane electrode, and is the most applicable technique among the current three methods for in situ and real time detection of HCN. It is sensitive and easy in operation, and needs little operator attention and calibration [7]. Unfortunately, the electrochemical analysis is frequently interfered by other ions, resulting in low selectivity. Therefore, it is extremely important and highly desired to develop novel HCN sensors with fast response, high selectivity and high sensitivity toward fast in situ and real time detection of HCN, and thus toward monitoring and timely reporting any possible presence or leakage of HCN.