Formation of Efficient Electron Transfer Pathways by Adsorbing Gold Nanoparticles to Self-Assembled Monolayer Modified Electrodes

Shin

et al. 2016

J. Electrochem. Soc.

Harnessing cathodic hydrogen atom generation, metals such as Pt, Pd, Cu, Au and Ni are directly electrodeposited on functionalized dielectric layers of 6 nm thick silicon oxide formed by thermal oxidation of c-Si substrate. Modifying the oxide layer with functional molecules and Au nanoparticles by simple wet chemistry, we can enhance electrodeposition efficiently and thereby electroplate nanoparticles of Pd and Pt to obtain such thin metal films. In particular, Au nanoparticles on amine-modified silicon oxides remarkably enhance electrodeposition of metal nanoparticles to create sturdy metal films on the dielectric layer, n + -Si/SiO 2 -NH 2 . Such enhancement is ascribed to good affinity of Au nanoparticles with electrodeposited metal as well as enhanced current density across the silicon oxide. For an example of potential applications, we show one-step electrodeposition Pd film on dielectric layers to fabricate conductometric hydrogen gas sensor without transferring Pd film. 8 and so on. Electrochemical methods 9,10 allow the solution process under fine and easy control without reducing agents by directly delivering electrons to precursors. Importantly, it can create stabilizer-free NPs or films with pristine surfaces that potentially serve as catalytically active sites for sensors and chemical reactions.11 Therefore, electroplating method has been widely considered as a cost-effective alternative. Especially, electro-synthesis of nanoparticles on conducting surfaces 12,13 has been attracting steady attention as highlighted by shape-control of nanoparticles using the programmed electrochemical methods on glassy carbon electrode. 14 Despite its valuable merits, programmed electro-synthesis can produce nanoparticles on the conducting electrode, while need to be transferred to other substrates, mostly dielectric materials, for practical applications in many cases. Recently reported strategy gives an inspiration of direct electrodeposition on dielectric layer; Pd NPs deposited on n + -Si/thermal SiO 2 . 15 It appears to be counterintuitive to electroplate on insulating substrates but it works owing to electrogenerated hydrogen (H) atoms in the thermal SiO 2 layer. H atom-mediated electro-reduction on thermal SiO 2 layers can be finely controlled by not only the applied bias but also pH in the solution, producing pristine Pd NPs deposited without any stabilizer or additive. H atoms, which are created by reduction of protons migrating across thermal SiO 2 layers, are expected to make precursors reduced at the interface between SiO 2 and solution. Indeed, this suggests a new breakthrough toward direct electroplating technology for thin metal films on dielectric layer.There are a few critical issues to overcome. Low density of current carried by H atoms and poor affinity of metal onto pristine SiO 2 are likely to make the metal grow too slow to be a film. Furthermore, there is a limitation in uniformity of particles in terms of both size and shape. For fine and steady control of electroplating process, it is undesir...

Section: Resultsmentioning

confidence: 99%

Direct Electrodeposition of Thin Metal Films on Functionalized Dielectric Layer and Hydrogen Gas Sensor

Shin

et al. 2016

J. Electrochem. Soc.

“…AuNPs were synthesized by reduction of tetrachloroauric acid by trisodium citrate following the method described by Gooding et al [13]. The final colloidal gold solution was kept in the dark until use.…”

Section: Synthesis and Characterization Of Gold Nanoparticles (Aunps)mentioning

confidence: 99%

“…Preliminary experiments showed that this treatment performed on NEEs does not change their electrochemical performances. Cysteamine is to be preferred to dithiols because it cannot form multilayers or disulfide bridges [13]. Previous studies showed that SH terminal groups bind preferentially to gold surfaces leaving the amino groups available for the subsequent NPs immobilization [13].…”

Section: Fabrication Of Nees and Modification With Aunpsmentioning

confidence: 99%

“…Cysteamine is to be preferred to dithiols because it cannot form multilayers or disulfide bridges [13]. Previous studies showed that SH terminal groups bind preferentially to gold surfaces leaving the amino groups available for the subsequent NPs immobilization [13]. The formation of a 3D structure takes place through the attachment of the nanoparticles to the free amino functionalities present on the monolayers, by weak covalent bonds [19,20].…”

Section: Fabrication Of Nees and Modification With Aunpsmentioning

confidence: 99%

See 1 more Smart Citation

Ensembles of nanoelectrodes modified with gold nanoparticles: characterization and application to DNA-hybridization detection

Silvestrini

Ugo

2012

Anal Bioanal Chem

A new method to increase the active area (A act ) of nanoelectrode ensembles (NEEs) is described. To this aim, gold nanoparticles (AuNPs) are immobilized onto the surface of NEEs using cysteamine as a cross-linker able to bind the AuNPs to the heads of the nanoelectrodes to obtain the so-called AuNPs-NEEs. The analysis of the cyclic voltammograms recorded in pure supporting electrolyte showed that the presence of the nanoparticles reflects in an, approximately, ten-times increase in the electrochemically active area of the ensemble. The measurement of the amount of electroactive polyoxometalates, which can be adsorbed on the gold surface of NEEs vs. AuNPs-NEEs, confirmed a significant increase of active area for the latter. These evidences indicate that there is a good electronic connection between the AuNPs and the underlying nanoelectrodes. The possibility to exploit AuNPs-NEEs for biosensing application was tested for the case of DNAhybridization detection. After immobilization on the gold surface of AuNPs-NEEs of a thiolated singlestranded DNA, the hybridization with complementary sequences labeled with glucose oxidase (GOx) was performed. The detection of the hybridization was achieved by adding to the electrolyte solution the GOx substrate (i.e., glucose) and a suitable redox mediator, namely the (ferrocenylmethyl) trimethylammonium (FA + ) cation; when the hybridization occurs, an electrocatalytic increase of the oxidation current of FA + is recorded.Comparison of electrocatalytic current recorded at DNA modified NEEs and AuNPs-NEEs indicate, for the latter, a significant increase in sensitivity in the detection of the DNA-hybridization event.

Journal of Experimental Nanoscience

“…In recent years, assembling the surface functional NPs onto electrode was commonly used to form modified electrode [17,18]. Generally, in this method, ligands with strong affinity to Au (such as thiol) was adopted to react with weak ligands (such as citrate [19] and phenylphenol [20]) protected Au NPs, forming functional Au NPs, and then the functional NPs were adsorbed onto the electrode surface to form NPs modified electrode. However, the electrochemical sensitivity of as-prepared modified electrode is greatly reduced due to the surface of NPs are tightly wrapped by functionalized organic molecules.…”

Section: Introductionsmentioning

confidence: 99%

A facile method to prepare noble metal nanoparticles modified Self-Assembly (SAM) electrode

Liu

Huang

Duan

et al. 2017

Noble metal nanoparticles (NPs) modified electrodes have shown promising applications in the areas of catalysis, (electro)chemical analysis and biosensing due to their unique characters. In this paper, we introduced a so-called ligand exchange method to prepare self-assembly (SAM) electrode modified with noble metal nanoparticles. The noble metal nanoparticles protected by weakly adsorbed tetraoctylammonium bromide (TOAB) were synthesized firstly, then self-assembly (SAM) dithiol-modified Au electrode (Au-SH SAM ) was immersed into the solutions containing TOAB-protected nanoparticles. Due to the strong interaction between the dithiol groups on the electrode and noble metal nanoparticles, the weakly adsorbed TOAB on the surface of noble metal NPs were replaced by dithiol groups. As a result, the TOAB protected NPs were anchored on the Au-SH SAM template electrode surface by ligand exchange, obtaining noble metal NPs modified electrode with high quality and stability. By adjusting the soaking time, the coverage of nanoparticles on the Au-SH SAM electrode surface could be controlled. The morphology and distribution of noble metal NPs on Au-SH SAM surface was analysis by scanning tunneling microscope (STM), and their electrochemical property was studied by cyclic voltammetry (CV) in H 2 SO 4 solution. The approach is proved as a universal way to prepare noble metal NPs modified SAM electrode.