Detection of presence of chemical precursors

A method for estimating presence of a target molecule in a gas, the method comprising:

• providing N carbon nanostructure (“CNS”) sub-arrays, numbered n=1, . . . , N (N≧2) on a substrate, where each CNS sub-array is loaded with a selected sensitizing substance comprising Au nanoparticles;
• estimating a first functional relationship EPV(C1;1) between a concentration C1 of a first target molecule and a first measured electrical parameter value EPV(n=1) in a gas, where the first relationship has a first approximate form EPV(n=1)=a1′+b1′·log(C1) in a first concentration range of C1 and has a second approximate form EPV(n=1)=a1+b1·C1 in a second concentration range of C1, where a1′, b1′, a1 and b1 are selected real numbers;
• estimating a second functional relationship EPV(C2;2) between a concentration C2 of a second target molecule and a second measured electrical parameter value EPV(n=2) in a gas, where the second relationship has a third approximate form EPV(n=2)=a2′+b2′·log(C2) in a first concentration range of C2 and has a fourth approximate form EPV(n=2)=a2+b2·C2 in a second concentration range of C2, where a2′, b2′, a2 and b2 are selected real numbers;
• exposing the CNS sub-array no. n (n=1, . . . , N) to the gas, and measuring the electrical parameter value EPV(n) in a time interval of length no more than about 15 sec;
• estimating a probable value of concentration, C1(opt) and C2(opt), of the first target molecule and the second target molecule, respectively, in the gas, based upon (1) differences between the value EPV(n=1) and the first functional relationship for the first target molecule and upon (2) differences between the value EPV(n=2) and the second functional relationship for the second target molecule
• computing a first error value depending upon differences between the measured values EPV(n) of the CNS sub-array no, n=1 and reference values E(C1(opt);ref;n=1) that corresponds to presence of the first target molecule in a gas with a concentration of C1 (opt);
• computing a second error value depending upon differences between the measured values EPV(n) of the CNS sub-array no, n=2 and reference values E(C2(opt);ref;n=2) that corresponds to presence of a second target molecule in a gas with a concentration of C2(opt);
• when the first error value is less than a selected first error threshold value, interpreting this condition as indicating that the first target molecule is present in the gas with a concentration of about C1(opt);
• when the second error value is less than a selected second error threshold value, interpreting this condition as indicating that the second target molecule is present in the gas with a concentration of about C2(opt);
• when the first error value is at least equal to the first error threshold value, interpreting this condition as indicating that the first target molecule is not present in the gas or is present in the gas with a concentration substantially less than C1(opt);
• and
• when the second error value is at least equal to the second error threshold value, interpreting this condition as indicating that the second target molecule is not present in the gas or is present in the gas with a concentration substantially less than C2(opt).