A nanoparticle comprising a SERS-active reporter molecule of the formula: A-Y wherein: A is selected from the group consisting of: wherein X 1 is CR 4 or N; Y is selected from the group consisting of: and wherein: r, s, and t are each independently an integer of 1; each X 2 and X 3 is independently selected from the group consisting of C, S, and N, under the proviso that (i) when X 2 is C or S, R 5 is Z, or when X 3 is C or S, R 6 is Z, as Z is defined herein below; (ii) if both X 2 and X 3 are N at the same time, at least one of R 5 and R 6 is absent; and (iii) when X 2 is N, R 5 when present is Z', or when X 3 is N, R 6 when present is Z', wherein Z' is selected from the group consisting of: -(CH 2) n -X 4; -NR 8 -(CH 2) p -X 5; -(CH 2) q X 6 C(=O)-R 9, wherein: n, p, q, u, and v are each independently an integer from 1 to 8; X 4 and X 5 are each independently selected from the group consisting of hydroxyl, amino, and thiol; X 6 is O or NR 11; wherein: each R 1, R 2, R 3, R 4, R 5, R 6, R 8, R 10, R 11, and Z is independently selected from the group consisting of H, alkyl, substituted alkyl, heteroalkyl, substituted heteroalkyl, cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, aryl, substituted aryl, aralkyl, hydroxyl, alkoxyl, hydroxyalkyl, hydroxycycloalkyl, alkoxycycloalkyl, aminoalkyl, acyloxyl, alkylaminoalkyl, and alkoxycarbonyl; R 7 is Z'; R 9 is -(CH 2) m -X, or -(CH 2) m -B, wherein m is an integer from 1 to 8; X 7 is halogen; and B is a binding member having a binding affinity for a ligand or analyte to be detected. A is selected from the group consisting of: wherein X 1 is CR 4 or N; Y is selected from the group consisting of: and r, s, and t are each independently an integer of 1; each X 2 and X 3 is independently selected from the group consisting of C, S, and N, under the proviso that (i) when X 2 is C or S, R 5 is Z, or when X 3 is C or S, R 6 is Z, as Z is defined herein below; (ii) if both X 2 and X 3 are N at the same time, at least one of R 5 and R 6 is absent; and (iii) when X 2 is N, R 5 when present is Z', or when X 3 is N, R 6 when present is Z', wherein Z' is selected from the group consisting of: -(CH 2) n -X 4; -NR 8 -(CH 2) p -X 5; -(CH 2) q X 6 C(=O)-R 9, wherein: n, p, q, u, and v are each independently an integer from 1 to 8; X 4 and X 5 are each independently selected from the group consisting of hydroxyl, amino, and thiol; X 6 is O or NR 11; wherein: each R 1, R 2, R 3, R 4, R 5, R 6, R 8, R 10, R 11, and Z is independently selected from the group consisting of H, alkyl, substituted alkyl, heteroalkyl, substituted heteroalkyl, cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, aryl, substituted aryl, aralkyl, hydroxyl, alkoxyl, hydroxyalkyl, hydroxycycloalkyl, alkoxycycloalkyl, aminoalkyl, acyloxyl, alkylaminoalkyl, and alkoxycarbonyl; each R 1, R 2, R 3, R 4, R 5, R 6, R 8, R 10, R 11, and Z is independently selected from the group consisting of H, alkyl, substituted alkyl, heteroalkyl, substituted heteroalkyl, cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, aryl, substituted aryl, aralkyl, hydroxyl, alkoxyl, hydroxyalkyl, hydroxycycloalkyl, alkoxycycloalkyl, aminoalkyl, acyloxyl, alkylaminoalkyl, and alkoxycarbonyl; R 7 is Z'; R 9 is -(CH 2) m -X, or -(CH 2) m -B, wherein m is an integer from 1 to 8; X 7 is halogen; and B is a binding member having a binding affinity for a ligand or analyte to be detected.