206 research outputs found
XPS characterization of polydopamine layers for improving surface biomolecule immobilization.
No full textPolydopamine (PDA) films have attracted a rapidly increasing research attention during the
last years due to its simple and rapid deposition under alkaline conditions in substrate
independent manner providing a universal coating for materials with different chemical and
physical properties [1]. Furthermore, this polymerized layer is enriched with functional
groups that enable immobilization of primary amine or thiol-based biomolecules via a simple
dipping process [2]. Although these fascinating aspects justify PDA wide and successful
application as a versatile coating for biomolecule immobilization, several aspects have not
been deeply investigated leaving some key details unclear and thus limiting PDA practical
applications. A number of approaches are commonly used for the growth of PDA [3], but the
effect of deposition conditions on film properties which in turn influence biomolecule
immobilization has not been systematically investigated yet.
In the present work, a detailed investigation by X-Ray Photoelectron Spectroscopy (XPS) of
PDA coatings deposited by different synthetic schemes (namely by autoxidation in air, under
a pure oxygen environment, in the presence of a strong oxidizing agent for different time
intervals (1, 3, 5, 8, 18, and 24 hours), and by electrochemical oxidation) is performed aimed
at investigating film thickness and chemical composition as a function of polymerization
conditions. Comparative spectroscopic analysis of PDA films revealed significant differences
in terms of deposition kinetics and abundance of chemical components and allowed
selection of synthesis conditions making PDA chemical structure richer in functionalities
mainly involved in conjugation of biomolecules. The high suitability of the selected PDA film
for bioconjugation was verified using a biomolecule conjugated to Horseradish Peroxidase or
to fluorophore, obtaining also an estimation of immobilization time-stability within 4 weeks
and a quantitative evaluation of immobilization extent. Moreover, further insight on
biomolecule anchoring was provided by the comparison of XPS data on PDA samples before
and after interaction with biomolecule [4].
[1] H. Lee, S.M. Dellatore, W.M. Miller, P.B. Messersmith, Science 318 (2007) 426–430.
[2] Y. Liu, K. Ai, L. Lu, Chem. Rev. 114 (2014) 5057–5115.
[3] H.W. Kim, B.D. McCloskey, T.H. Choi, C. Lee, M.J. Kim, B.D. Freeman, H.B. Park, ACS Appl.
Mater. Interfaces. 5 (2013) 233–238
[4] S. Rella, E. Mazzotta, A. Caroli, M. De Luca, C. Bucci, C. Malitesta, Appl. Surf. Sci. 447
(2018) 31–39
Spectroscopic characterisation of TiO2 nanoparticles
No full textTiO2 nanoparticles (TiO2 NPs), synthetised by the hydrolysis at room temperature of titanyl oxalate, have been characterised by UV-vis spectroscopy and photoluminescence analysis. The influence of precursor concentration on Ti02 NPs growth and their optical properties have been studied. By the interpretation of absorbance spectra a rapid formation of titania clusters has been suggested and a constant energy onset at 3.59 eV has been found, according to a direct transition calculated for titanum dioxide. No size quantization effects can be addressed for stabilised colloids. Two photoluminescence (PL) peaks have been assigned to direct and indirect transitions, respectively. A third peak has been related to surface oxygen vacancies. Copyright © 2008 American Scientific Publishers All rights reserved
ELECTROSYNTHESIS AND ANALYTICAL CHARACTERIZATION OF FILMS OBTAINED BY OXIDATION OF 2,6-DIAMINOPYRIDINE
No full textThe oxidation of 2,6-diaminopyridine in acetonitrile-LiClO4 at a platinum electrode leads to the formation of two different films (I and II), depending on the deposition potential. Electroanalytical investigations revealed an ECE mechanism operating for film I formation and provided evidence for nucleation and growth in film II deposition. UV and ESCA spectroscopic characterization revealed the different natures of the films
XPS in the investigation of electrode surfaces: Analytical characterization of the CuO cathode in the Li/CuO cell.
No full textEnzyme-Mimics Molecularly Imprinted Polymers Based on Metal Complexes: Electropolymerization and Electrocatalytic Application
No full textThe development of an electrosynthesized molecularly imprinted polymer (MIP) based on a metal complex is here reported as an effective strategy for combining advantages coming from metal-ion coordination and catalytic capabilities of metallic centers with ones deriving from electropolymerization. Metal ion coordination combines the flexibility of noncovalent imprinting approaches with the strength and specificity of covalent ones representing an attractive binding mechanism in MIP design for the recognition of a vast array of analytes. In addition, such a MIP possesses catalytic properties other than recognition capability, which is not so common in MIP field. On the other hand, electropolymerization represents a highly successful way of easily anchoring MIP-based sensing layers to the transducer surface. Procedures for MIP electrosynthesis as well as for its analytical application in electrocatalytic sensing are described
Pristine and overoxidized polypyrrole by XPS
No full textAn x-ray photoelectron spectroscopy (XPS) analysis was performed of polypyrroles (PPy) electrosynthesized on Pt in aqueous solution. Spectra were recorded both for the as-synthesized (pristine) polymer (specimen 1) and for the so-called “overoxidized” PPy (specimen 2). Electrosynthesis was accomplished potentiostatically at +0.7 V vs SCE in KCl 10 mM containing pyrrole 0.4 M. Overoxidized PPy was obtained by keeping the pristine polymer at the electrosynthesis potential for 5 h, in phosphate buffer solution (pH 7). C, N, O (1s), and Cl 2p (pristine) spectra are included. Some minor elements, P (in the overoxidized polymer), Na (in some overoxidized samples), and Si (in other samples of both types of PPy, but not in those here reported), were also detected
Ti AND Fe SPECIATION BY X-RAY PHOTOELECTRON SPECTROSCOPY (XPS) AND MÖSSBAUER SPECTROSCOPY FOR A FULL CRYSTAL CHEMICAL CHARACTERISATION OF Ti-GARNETS FROM COLLI ALBANI (ITALY)
No full textOn the correlation between permselectivity and chemical structure of overoxidized polypyrrole membranes used in electroproduced enzyme biosensors
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