A semiconductor nanowire is coated with a chemical coating layer that comprises a functional material which modulates the quantity of free charge carriers within the semiconductor nanowire. The outer surface of the chemical coating layer includes a chemical group that facilitates bonding with molecules to be detected through electrostatic forces. The bonding between the chemical coating layer and the molecules alters the electrical charge distribution in the chemical coating layer, which alters the amount of the free charge carriers and the conductivity in the semiconductor nanowire. The coated semiconductor nanowire may be employed as a chemical sensor for the type of chemicals that bonds with the functional material in the chemical coating layer. Detection of such chemicals may indicate pH of a solution, a vapor pressure of a reactive material in gas phase, and/or a concentration of a molecule in a solution.