title: Determination of nanomolar uric and ascorbic acids using enlarged gold nanoparticles modified electrode.
abstract: Individual and simultaneous determination of 50nM uric acid (UA) and ascorbic acid (AA) using enlarged, citrate-stabilized gold nanoparticles (AuNPs) self-assembled to 2,5-dimercapto-1,3,4-thiadiazole (DMT) monolayer modified Au (Au/DMT) electrode by an amperometric method is described for the first time. Self-assembly of AuNPs on the electrode surface was confirmed by atomic force microscopy (AFM), attenuated total reflectance FT-IR and diffuse reflectance spectral measurements. The electron transfer reaction (ETR) of [Fe(CN)(6)](3-/4-) was blocked at Au/DMT electrode, whereas it was restored with a peak separation of 200mV after the attachment of AuNPs on the Au/DMT (Au/DMT/AuNPs) electrode, which was confirmed from the ETR of the [Fe(CN)(6)](3-/4-) redox couple. When the self-assembled AuNPs were enlarged by hydroxylamine seeding, the ETR of [Fe(CN)(6)](3-/4-) was improved significantly with a peak separation of 100mV. Tapping mode AFM showed that the average size of the enlarged-AuNPs (E-AuNPs) was 50-70nm. The E-AuNPs modified electrode catalyzes the oxidation of AA and UA, separates their voltammetric signals by 200mV, and has excellent sensitivity towards AA and UA with a detection limit of 50nM. The practical application of the modified electrode was demonstrated by measuring the concentration of UA in blood serum and urine.
authors.affiliation: Department of Chemistry, Gandhigram Rural University, Dindigul, India.
authors.forename: P
authors.initials: P
authors.lastname: Kannan
authors.forename: S Abraham
authors.initials: SA
authors.lastname: John
mesh_terms: D001205:Ascorbic Acid / Q000032:analysis*; D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods; D004566:Electrodes; D006046:Gold; D053768:Metal Nanoparticles; D008722:Methods; D036103:Nanotechnology / Q000379:methods; D010084:Oxidation-Reduction; D012107:Research Design; D014527:Uric Acid / Q000032:analysis* / Q000097:blood / Q000652:urine
chemical_list: D014527:Uric Acid; D006046:Gold; D001205:Ascorbic Acid