A　new　impedimetric　sensing　strategy　based　on　enzyme-triggered　formation　of　enzyme-tyramine　concatamers　on　the　nanogold-functionalized　poly(amidoamine)　(PAMAM)　dendrimer　was　designed　for　sensitive　detection　of　mercury(II)　(Hg2+)　ion,　coupling　with　enzymatic　biocatalytic　precipitation　towards　4-choloro-1-naphthol　(4-CN)　on　thymine　(T)-rich　single-stranded　DNA1-modified　electrode.　Initially,　nanogold–decorated　PAMAM　dendrimer　(AuNP–PAMAM)　was　synthesized　by　the　in-situ　reduction　method,　and　then　functionalized　with　horseradish　peroxidase　(HRP)　and　another　T-rich　oligomer　(DNA2).　Upon　target　Hg2+　introduction,　probe　DNA2　on　the　AuNP–PAMAM　bound　to　the　DNA1　on　the　electrode　owing　to　the　T–Hg2+–T　coordination　chemistry　between　the　two　DNA　strands.　Accompanying　the　AuNP–PAMAM,　the　carried　HRP　could　trigger　the　formation　of　HRP–tyramine　concatamer　via　the　classical　tyramine　signal　amplification　strategy　in　the　presence　of　HRP–tyramine　conjugates　and　hydrogen　peroxide.　The　concatenated　HRP　molecules　in　the　concatamer　catalyzed　the　4-CN　oxidation　to　produce　an　insoluble　precipitation　on　the　electrode,　thereby　resulting　in　the　local　alteration　in　the　conductivity.　Under　optimal　conditions,　two　signal-generation　tags　including　HRP–AuNP–DNA2　and　HRP–AuNP–PAMAM–DNA2　with　or　without　tyramine　signal　amplification　strategy　(i.e.,　four　schemes)　were　used　for　impedimetric　detection　of　target　Hg2+　on　the　basis　of　the　same　assay　format.　A　low　detection　limit　(LOD)　of　0.4 pM　and　a　wide　dynamic　working　range　of　0.001–100 nM　Hg2+　by　using　HRP–AuNP–PAMAM–DNA2　with　tyramine　signal　amplification　strategy　were　obtained　in　comparison　with　those　of　other　strategies.　The　assay　had　a　good　repeatability　and　showed　an　intermediate　precision　of　down　to　9.6%.　In　addition,　the　methodology　also　exhibited　high　specificity　and　selectivity　towards　target　Hg2+　against　other　metal　ions,　and　was　applicable　for　monitoring　Hg2+　in　the　spiked　drinking　water　samples.　©　2015　Elsevier　B.V.