Determination of Surface pKa of SAM Using an Electrochemical Titration Method

Zhao, Jianwei; Luo, Liqiang; Yang, Xiurong; Wang, Erkang; Dong, Shaojun

doi:10.1002/(sici)1521-4109(199911)11:15<1108::aid-elan1108>3.0.co;2-z

Cited by 141 publications

(52 citation statements)

References 21 publications

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“…The curve is very similar to that reported for the electrochemical titration of the pyS SAM on gold 44 and it indicates that the h ET reaction of the [Fe(CN) 6 ] 4-probe is strongly sensible to the protonation equilibrium on the nitrogen atom of the pyridine ring.…”

Section: Inorganic Complexes As Probe Moleculessupporting

confidence: 82%

“…[42][43][44] Considering the results presented in Figure 5 and those reported in the literature, [42][43][44] a model based on the resonance structures of the Hpyt molecules on gold is suggested in Scheme 1 to explain the changes in the voltammograms of the [Fe(CN) 6 ] 4-probe molecule. At pH > 4.0, two resonance forms, I and II, can be proposed, with the real structure between them.…”

Section: Inorganic Complexes As Probe Moleculesmentioning

confidence: 84%

See 1 more Smart Citation

5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol on gold: SAM Formation and electroactivity

Paulo

Silva

Pinheiro

et al. 2008

J. Braz. Chem. Soc.

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O composto 5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol (Hpyt) adsorve espontaneamente sobre ouro formando SAMs ("Self-Assembled Monolayers") que, de acordo com os resultados eletroquímicos e de STM ("Scanning Tunneling Microscopy"), contêm poros através dos quais as moléculas dos complexos [Fe(CN) 6 ] 4-, a dependência da corrente faradáica com o pH da solução eletrolítica permitiu o cálculo do pKa da molécula de Hpyt adsorvida sobre ouro (4,2). Os parâmetros termodinâmicos, H ads and G ads , para o processo de adsorção desta molécula foram estimados em -20,01 e -39,39 kJ mol -1 , respectivamente, utilizando-se o modelo de Langmuir. O processo redox da metaloproteína citocromo c foi estudado utilizando-se a SAM de Hpyt. A constante de velocidade heterogênea de transferência de elétrons foi calculada em 2,29 10 -3 cm s -1 .5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol (Hpyt) spontaneously adsorbs on gold forming SAMs (self-assembled monolayers) that, based on STM (Scanning Tunneling Microscopy) and electrochemical data, contain pinholes through which [Fe(CN) 6 ] 4-and [Ru(NH 3 ) 6 ] 3+ probe molecules access the underlying gold electrode. For the former molecule, the dependence of the faradaic current on the electrolyte solution pH value allowed the evaluation of the surface pKa as 4.2. The thermodynamic parameters H ads and G ads for the Hpyt adsorption process could be described by the Langmuir model and were calculated as -20.01 and -39.39 kJ mol -1 , respectively. Electrodic redox reaction of cytochrome c metalloprotein was accessed by using the Hpyt SAM with a heterogeneous electron transfer rate constant of 2.29 10 -3 cm s -1 .

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Section: Inorganic Complexes As Probe Moleculessupporting

confidence: 82%

Section: Inorganic Complexes As Probe Moleculesmentioning

confidence: 84%

5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol on gold: SAM Formation and electroactivity

Paulo

Silva

Pinheiro

et al. 2008

J. Braz. Chem. Soc.

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“…All these results indicate that SAMs of suitable sulphur compounds give ionic charge selectivity to NEEs, furnishing to the nanoelectrodes the same permselectivity demonstrated previously for the case of individual m-sized electrodes [20][21][22][23]. A MES layer allows only cationic or neutral probes to access the nanoelectrode surface to undergo successful electron transfer.…”

Section: Redox Probes At Sam Modified Neessupporting

confidence: 78%

“…Pioneering studies developed on flat gold surfaces and microelectrodes [20][21][22][23] showed the possibility to modify electrode surfaces and to tune their ionic selectivity by using self-assembled monolayers (SAM) of thiols with carboxylate functionalities; indeed, by changing the solution pH it is possible to change the ionic charge of the monolayer. In the present research, we demonstrate the possibility to use SAMs of thiols and disulfides to furnish ionic permselectivity even to the surface of gold nanoelectrodes with diameter as small as 30 nm.…”

Section: Introductionmentioning

confidence: 99%

Modification of nanoelectrode ensembles by thiols and disulfides to prevent non specific adsorption of proteins

Silvestrini

Schiavuta²,

Scopece³

et al. 2011

Electrochimica Acta

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a b s t r a c tThe possibility to functionalize selectively with thiols or disulfides the surface of the gold nanoelectrodes of polycarbonate templated nanoelectrode ensembles (NEEs) is studied. It is shown that the Au nanoelectrodes can be coated by a self assembled monolayer (SAM) of thioctic acid (TA) or 2-mercaptoethanesulfonic (MES) acid. The study of the electrochemical behavior of SAM-modified NEEs by cyclic voltammetry (CV) at different solution pH, using ferrocenecarboxylate as an anionic redox probe (FcCOO − ) and (ferrocenylmethyl)trimethylammonium (FA + ) as a cationic redox probe, demonstrate that the SAM-modified nanoelectrodes are permselective, in that only cationic or neutral probes can access the SAM-coated nanoelectrode surface. CV, AFM and FTIR-ATR data indicate that proteins such as casein or bovine serum albumin, which are polyanionic at pH 7, adsorb on the surface of NEEs untreated with thiols, tending to block the electron transfer of the ferrocenyl redox probes. On the contrary, the pretreatment of the NEE with an anionic SAM protects the nanoelectrodes from protein fouling, allowing the detection of well shaped voltammetric patterns for the redox probe. Experimental results indicate that, in the case of MES treated NEEs, the protein is bound only onto the polycarbonate surface which surrounds the nanoelectrodes, while the tips of the gold nanoelectrodes remain protein free.

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“…At the buffer (pH 7.2), the electrode carries negative charges due to partially deprotonation of the carboxyl acid groups [30]. Because PAA-Fc carries positive charges and L-proDH carries negative charges under present experimental conditions, the multilayer film could be formed by an electrostatic force between oppositely charged polyelectrolyte and enzyme (as shown in Fig.…”

Section: Formation Of Paa-fc/l-prodh Multilayer Film On Au Electrode mentioning

confidence: 92%

_L-Proline sensor based on layer-by-layer immobilization of thermostable dye-linked L-proline dehydrogenase and polymerized mediator

Zheng

Hirose

Kimura

et al. 2006

Science and Technology of Advanced Materials

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L-Proline sensor has been fabricated through multilayer assembly of recombinant dye-linked L-proline dehydrogenase (L-proDH) originally from hyperthermophilic archaeon (Therococcus profundus) and polymerized mediator, poly(allylamine) ferrocene (PAA-Fc), on a gold electrode by electrostatic layer-by-layer alternate adsorption method. The characteristic redox peaks of ferrocene groups were obvious exhibited in cyclic voltammograms, and both anodic and cathodic peaks increased with PAA-Fc/L-proDH bilayer number which confirmed the formation of a multilayer structure. Further experiments showed that an electrode fabricated in this way catalyzed the oxidation of L-proline. It suggested that polymerized mediator could transfer electrons between electrode surface and immobilized L-proDH. Ampeormetric experiments showed that the current response to L-proline increased with PAA-Fc/L-proDH bilayer number. The stability of the sensor was measured, and it kept a 40% relative response after 30 days storage in buffer under 4 8C. q

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Determination of Surface pKa of SAM Using an Electrochemical Titration Method

Cited by 141 publications

References 21 publications

5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol on gold: SAM Formation and electroactivity

5-(4-pyridinyl)-1,3,4-oxadiazole-2-thiol on gold: SAM Formation and electroactivity

Modification of nanoelectrode ensembles by thiols and disulfides to prevent non specific adsorption of proteins

_L-Proline sensor based on layer-by-layer immobilization of thermostable dye-linked L-proline dehydrogenase and polymerized mediator

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