Seed-mediated Electrochemically Developed Au Nanostructures with Boosted Sensing Properties: An Implication for Non-enzymatic Glucose Detection

Abstract

A new approach has been developed to improve sensing performances of electrochemically grown Au nanostructures (AuNSs) based on the pre-seeding of the electrode. The pre-seeding modification is simply carried out by vacuum thermal deposition of 5 nm thin film of Au on the substrate followed by thermal annealing at 500 °C. The electrochemical growth of AuNSs on the pre-seeded substrates leads to impressive electrochemical responses of the electrode owing to the seeding modification. The dependence of the morphology and the electrochemical properties of the AunSs on various deposition potentials and times have been investigated. for the positive potentials, the pre-seeding leads to the growth of porous and hole-possess networks of AunSs on the surface. for the negative potentials, AunSs with carved stone ball shapes are produced. the superior electrode was achieved from AunSs developed at 0.1 V for 900 s with pre-seeding modification. The sensing properties of the superior electrode toward glucose detection show a high sensitivity of 184.9 µA mM −1 cm −2 , with a remarkable detection limit of 0.32 µM and a wide range of linearity. the excellent selectivity and reproducibility of the sensors propose the current approach as a large-scale production route for non-enzymatic glucose detection. During past decades, electrochemical sensing has attracted many attentions due to their considerable advantages such as high sensitivity, low cost, fast response time, wide linear range and portability and widespread applications 1-9. Up to now various types of nanomaterial such as carbon nanotubes 10 , graphene 11,12 , noble metals 13,14 , metal oxides 15 , hybrid 16 and composite nanostructures 17,18 have been developed for electrochemical sensing. Among different nanomaterials, gold nanostructures (AuNSs) have attracted significant interests because of their remarkable electrical and catalytic properties, easy functionalization and excellent biocompatibility. Since the electron transfer and catalytic activity of AuNSs strongly depend on their morphology and their size, extensive researches have been proposed in literatures to develop optimized AuNSs for sensing applications 19,20. The notable approaches between them are based on the electrodeposition 19 , direct electrostatic self-assembly 21 , self-assembly with polymer 22-24 and seed-mediated growth 25-28. In the cases of self-assembly and seed-mediated strategies, the electron transfer and catalytic activity of AuNSs are hindered due to the existence of surfactant and linker molecules surrounding the nanostructures. The electrodeposition is the most reliable approach for shape and size controlled construction of AuNSs due to the possibility of controlling the nucleation and the growth processes. However, in this method the well control of morphology is provided by using template, surfactant or pre-treatment of the substrate that limit the applicability of the method 20,29,30 .

Stable, reproducible, and binder-free gold/copper core–shell nanostructures for high-sensitive non-enzymatic glucose detection

“…To verify the selective deposition of Cu shell on Au nanocores, the chronoamperometry measurement was utilized since the details of the transient current can be obtained by this method 43 , 46 . Figure S3 illustrates the transient current–time curves during deposition of Cu on the bare and the core supported FTO electrodes.…”

Stable, reproducible, and binder-free gold/copper core-shell nanostructures for high-sensitive non-enzymatic glucose detection

“…For later times, the current decreases due to the FTO surface coverage by Cu nanostructures resulting in appearance of a peak in the current-time curve. For the core supported FTO electrode, the absence of the current peak relating to the nucleation process con rms direct and selective deposition of Cu on Au cores 39 .…”

“…In fact, the epitaxial nucleation of Cu on the Au surface occurs due to epitaxial growth of Au core and Cu shell [35][36][37] . In addition, the higher surface energy of the Au nanocores compared to the FTO defect sites leads to the competitive deposition of Cu on the Au surface 38,39 . Therefore, the proposed method results in the direct and binder free formation of a dense array of Au@Cu structure with the size distribution range of 20-60 nm.…”

“…To produce Au cores, Au thin lm was evaporated on the FTO substrate. The physical vapor deposition parameters were according to a procedure described previously 39 . After that, the Au cores were formed on the FTO substrate by annealing the Au lm at 550 o C for 10 h under the air atmosphere 39 .To study the in uence of Au lm thickness on the charge transfer properties of the fabricated electrode, various thicknesses of 2.5, 5 and 10 nm have been deposited.…”

“…To verify the selective deposition of Cu shell on Au nanocores, the chronoamperometry measurement was utilized since the details of the transient current can be obtained by this method 39,42 . Figure S2 illustrates the transient current-time curves during deposition of Cu on the bare and the core supported FTO electrodes.…”