Abstract: In a first aspect, the present invention is directed to a microelectrode array for detecting heavy metals in an aqueous solution. The microelectrode array can comprise a layer of a doped carbon film and a patterning layer arranged on the doped carbon film for defining multiple microelectrodes in the doped carbon film to form the microelectrode array. The size, and shape, and arrangement of each of the multiple microelectrodes can be defined by the size, and shape, and arrangement of each of the openings in the patterning layer which expose the underlying doped carbon film. Furthermore, the ratio of the maximal width of a microelectrode relative to the shortest distance between the neighboring microelectrodes (center to center) in the microelectrode array is between about 1:1.2 and about 1:6. The present invention is also directed to an apparatus using the microelectrode array and methods of manufacturing the same.