Influence of an external magnetic field on the formation of self-assembled monolayers of dodecanethiol on polycrystalline gold electrode

Zhang

et al. 2011

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In this article we studied the permeable characteristics of thiol-modified double-stranded DNA (ds-DNA) self-assembled monolayers (SAMs) on a gold substrate assembled under different NaCl concentrations by electrochemical methods. It was based on the inspection of five important parameters including interfacial capacitance (C), phase angle (Φ(1 Hz)), ions transfer resistance (R(it)*), current density difference (Δj) and electron transfer rate (k(et)) through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Three sections were included: (1) Investigation of the relationships of C, Φ(1 Hz), R(it)*, Δj and k(et) with NaCl concentrations and comparison with the reports from literature. Experimental results showed that ds-DNA-SAMs were permeable films. (2) Construction of a simple model for exploring the permeable characteristics of ds-DNA-SAMs on gold. (3) Confirmation of the simple model by chronocoulometry (CC) and application of the model to explain the permeable mechanism. This study was significant for exploring the mechanism of electron transfer through the interior of ds-DNA duplex helix.

Section: Electrochemical Characterizationmentioning

confidence: 99%

Electrochemical studies on the permeable characteristics of thiol-modified double-stranded DNA self-assembled monolayers on gold

Zhang

et al. 2011

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“…Interfacial capacitance (C) was measured from CV experiments performed from À200 to +200 mV in PBS solution at different scan rate v (0.1, 0.5, 1, 5, 20, 50 V s À1 ) based on C ¼ i/2vA where i was the summed current (mA) from the positive and negative scan directions at 0 mV, v was the scan rate (V s À1 ) and A was the real area of gold electrodes (cm 2 ). [20][21][22][23][24][25][26] The absolute value of phase angle at 1 Hz (F 1 Hz ) and R it * were used for evaluating ion penetration in SAMs. [27][28][29][30] F 1 Hz and R it * were obtained by EIS experiments at 0 mV in PBS solution with frequency range from 0.1 Hz to 10 5 Hz and 5 mV amplitude.…”

Section: Electrochemical Characterizationmentioning

confidence: 99%

“…Dj was the difference of current density at À0.2 V and +0.5 V (Dj ¼ |j -0.2 V À j +0.5 V |). 20,21,[24][25][26] Charge transfer resistance (R ct ) was measured by EIS in 2 mM Fe(CN) 6 3À/4À…”

Section: Electrochemical Characterizationmentioning

confidence: 99%

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Effect of monovalent cations (Li+, Na+, K+, Cs+) on self-assembly of thiol-modified double-stranded and single-stranded DNA on gold electrode

Zhang

et al. 2012

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In this article we investigate the effect of monovalent cations (Li(+), Na(+), K(+), Cs(+)) on self-assembly of thiol-modified double-stranded DNA (ds-DNA) and single-stranded DNA (ss-DNA) on gold electrodes. Electrochemical characteristics (surface coverage, ion penetration and charge transfer) of ds-DNA and ss-DNA self-assembled monolayers (SAMs) formed with different monovalent cations are inspected based on six important interfacial parameters including surface coverage (Γ(m)), interfacial capacitance (C), phase angle (Φ(1 Hz)), ion transfer resistance (R(it)*), current density difference (Δj) and charge transfer resistance (R(ct)) from chronocoulometry (CC), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Three sections are included: (1) Investigation of the relationships of parameters (Γ(m), C, Φ(1 Hz), R(it)*, Δj and R(ct)) for ds-DNA-SAMs and ss-DNA-SAMs with cation types and concentrations; (2) confirmation and explanation of our experimental results combined with our recently proposed simple DNA model and literature reports; (3) exploration of the mechanism for the orders of monovalent cations (Li(+), Na(+), K(+), Cs(+)) on availing the adsorption of ds-DNA and ss-DNA molecules on gold based on their physicochemical parameters (ion size, solvation free energy and enthalpy, ion-water bond length and water exchange rate) and possible binding modes with DNA molecules. This work might provide a useful reference for understanding interactional mechanism of cations with DNA molecules.

“…5,7,11,12,18,21,38,40,43,61 The ability of fabricating high-quality self-assembled layers depends on the Au electrode pretreatment before assembly. 7 Au electrode pretreatment methods mainly include five methods: aqua regia pretreatment, [64][65][66][67][68][69][70][71][72][73] reductive annealed pretreatment, 9,16,42,[74][75][76][77][78] UV/O 3 pretreatment, 34,[79][80][81][82][83] piranha reagents pretreatment 7,8,[84][85][86][87][88][89][90][91][92] and simple polishing pretreatment. 6,76,[93][94]…”

Section: Introductionmentioning

confidence: 99%

Studies on the effect of electrode pretreatment on the coverage of self-assembled monolayers of dodecanethiol on gold by electrochemical reductive desorption determination

Feng

You

et al. 2011

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This paper examines the effect of five major pretreatments on the surface coverage Γ(m) of dodecanethiol self-assembled monolayer on polycrystalline gold electrode (C(12)SH-SAMs-Au). It is based on the electrochemical reductive desorption in the alkaline solution by cyclic voltammetry (CV). The five different pretreatment methods include: aqua regia pretreatment, reductive annealed pretreatment, UV/O(3) pretreatment, piranha reagents pretreatment and simple polishing pretreatment, and then all above pretreatments following the same procedure of electrochemistry cleaning. The experimental results show that the surface coverage Γ(m) for C(12)SH-SAMs-Au by the five pretreatment methods are: aqua regia pretreatment (8.0 × 10(-10) mol cm(-2)) ~ reductive annealed pretreatment (7.8 × 10(-10) mol cm(-2)) > UV/O(3) pretreatment (5.0 × 10(-10) mol cm(-2)) ~ piranha reagents pretreatment (4.1 × 10(-10) mol cm(-2)) ~ simple polishing pretreatment (4.0 × 10(-10) mol cm(-2)). This indicates that Au surfaces pretreated by aqua regia and reductive annealing can achieve the best results, and the Γ(m) values obtained are consistent with the theoretical coverage values (Γ(m) ≈ 8.0 × 10(-10) mol cm(-2)); however, the Γ(m) values for other three pretreatment methods (UV/O(3), piranha reagents and simple polishing) are not satisfactory, obtaining only almost half of the theoretical Γ(m) value. Thus, we recommend aqua regia and reductive annealed pretreatments as the best methods for self-assembling the alkyl thiol monolayer (C(n)SH-SAMs-Au), whereas UV/O(3), piranha reagents and simple polishing pretreatments are not recommended.