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Istituto sull'inquinamento atmosferico

Torna all'elenco Contributi in atti di convegno anno 2016

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Tipo: Poster

Titolo: SELF ASSEMBLED MONOLAYERS AND ELECTROCHEMICALLY DEPOSED MULTILAYERS OF THIOLS ON GOLD SURFACE COMPARED BY EIS AND AFM

Anno di pubblicazione: 2016

Formato: Elettronico

Autori: Jessica Castagna, Francesca Malvano, Donatella Albanese, Roberto Pilloton

Affiliazioni autori: CNR-IIA, Università di Salerno

Autori CNR:

  • ROBERTO PILLOTON

Lingua: inglese

Abstract: Self-Assembling is based on a spontaneous process in which organic molecules (alkanethiols, silanes) are adsorbed by a substrate (gold, glass, silicon). In particular, the "head group" (-SH, Si-OH) of a molecule is subject to chemisorptions onto a substrate, on the other hand, the "tails", previously disordered, arrange themselves in an ordered domains. Self Assembled Monolayers (SAMs) of thiols on gold are key elements for building many systems and devices with applications in the wide field of nanotechnology. Despite the progress made in the knowledge of these fascinating two-dimensional molecular systems, there are still several "hot topics" that deserve special attention in order to understand and to control their physical and chemical properties at the molecular level. Proprieties of this phenomena, ruled by intermolecular and molecular-solvent interaction, are useful to build up some sensors or biosensors designed to detect specific analytes (i.e., Hg(0), ochartoxin A, E.coli). The greatest advantage of this approach is a two dimensional assemblies characterized by a good flexibility. Although the implementation is extremely easy, it shows a big disadvantage in timing, because the procedure requires to leave the solution on the substrate under stirring overnight. In addition, other defects can arise from external factors, such as the cleanliness of the substrate, method of preparation and the purity of the adsorbates. It is therefore suitable perform several precautions in order to reduce these drawbacks, such as the cleaning of the substrate (three electrode system of gold) by using several cyclic voltammetry (CV) scans between -1,5V e +1,5V in H2SO4, 0.5M. Scan Rate=1V/s Estep=5mV. (Fig.1, insert). An alternative method of molecular deposition is the Electrochemically Deposed Multilayers (EDMs) commonly used in our laboratory for further immobilisation of biological molecules in order to obtain specific biosensors for several analytes. It consists in applying a constant potential on gold working electrode (1.2V vs Reference Electrode, RE) for driving molecules in proximity of the electrode and allow them to react on the surface, and form a layer similar to SAMs. In addition this approach allows to address molecules onto a specific electrode in an array, too. During deposition, the current intensity is recorded by chronoamperometry (Fig.1) till the end of the electrochemical treatment. Cysteamyne (CYS) or 4-mercaptobenzoic acid (MBA) were used in this work for obtaining SAMs or EDMs on gold electrodes for further immobilisation of gold nanoparticles (AuNP), oligonucleotides, proteinA and pAb against OTA and a mAb against E.coli. Both the layers were tested with Electrochemical Impedance Spectroscopy (EIS, Fig.2) and Atomic force Microscopy (AFM, Fig.3). SAM obtained overnight shows gold electrodes poorly covered with a thin film and several holes (not homogenous thickness) where the surface of the bare gold electrode emerges, reducing the performances of electrochemical further obtained sensors and biosensors based on both amperometric or EIS measurements. The substrate covered with EDM shows a higher and a more homogeneous deposition than SAM, and the deposition time is extremely reduced from several hours to a few of seconds (50 s). However, analyzing both substrates with Atomic Force Microscopy (AFM), we observed that the EDMs layers (Fig.2b) seem to be disordered and thicker than the single layer of SAM which is also more flexible (Fig2a). Kinetics of several molecules sequentially deposed on gold electrode (Au ? CYS ? GLU ? mAb(E.coli) ? Et-NH2 as a blocking agent ? fragments of E.coli membrane, 0.2ng L-1 and Au ? Cys ? GLU ? CYS ? AuNP), have been also measured by EIS (data not shown). Advantages and disadvantages of both the depositions (SAMs and EDMs) will be discussed in the poster presentation.

Lingua abstract: inglese medio (1100-1500)

Referee: Sì: Nazionale

Stato della pubblicazione: Published version

Parole chiave:

  • Biosensors. Gold thiolated surface

Congresso nome: 3° Convegno Nazionale Sensori, 23-25 Febbraio 2016, Roma

Congresso luogo: Roma

Congresso data: 23-25/02/2016

Congresso rilevanza: Nazionale

Congresso relazione: Contributo

Strutture CNR:

Allegati: SELF ASSEMBLED MONOLAYERS AND ELECTROCHEMICALLY DEPOSED MULTILAYERS OF THIOLS ON GOLD SURFACE COMPARED BY EIS AND AFM (application/pdf)

 
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