Institute of Nanostructures, Nanomodelling and Nanofabrication

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Publications

Comparison of antimony selenide thin films obtained by electrochemical deposition and selenization of a metal precursor

Publication . Shongalova, Aigul; Aitzhanov, Madi; Zhantuarov, Sultan; Urazov, Kazhmukhan; Fernandes, Paulo; Tokmoldin, Nurlan; Correia, Maria Rosário

In this work, we present a study comparing two methods of Sb2Se3 deposition, namely electrochemical deposition and selenization of a thin-film metallic Sb – precursor deposited by magnetron sputtering. The Sb selenization process was carried out in the range of temperatures from 270 ºC to 350 ºC in an argon atmosphere enriched with elemental Se vapor. Electrochemical deposition of Sb2Se3 was performed in a three-electrode cell at constant potential. Following electrochemical deposition, the samples were annealed in argon at temperatures ranging from 270 ºC to 350 ºC. Characterization of the obtained thin films was performed using X-ray diffraction, Raman spectroscopy and optical transmission. Both deposition methods demonstrate successful emergence of the selenide phase, albeit with the presence of varying levels of antimony oxide. The possibility of preferential growth was observed, which is suggested as dependent on growth method and annealing temperature.

2020Conference object

Restricted access

Paper-based (bio)sensor for label-free detection of 3-nitrotyrosine in human urine samples using molecular imprinted polymer

Publication . Martins, Gabriela V.; Marques, Ana C.; Fortunato, Elvira; Sales, Maria Goreti Ferreira

Over the last years, paper technology has been widely spread as a more affordable, sustainable and reliable support material to be incorporated in the design of point-of-care (POC) diagnostic devices. However, the single work employing a paper-based device for 3-nitrotyrosine (3-NT), a relevant biomarker for oxidative stress (OS) that is a major origin for many diseases, is incapable of reading successfully complex samples because every species that oxidizes before ~0.75 V will also contribute to the final response. Thus, the introduction of a selective element was made into this set-up by including a molecularly-imprinted polymer (MIP) tailored in-situ. Herein, a novel MIP for 3-NT was assembled directly on a paper platform, made conductive with carbon ink and suitable for an electrochemical transduction. The biomimetic material was produced by electropolymerization of phenol after optimizing several experimental parameters, such a scan-rate, number of cycles, range of potential applied, monomer and template concentrations. Under optimal conditions, the label-free sensor was able to respond to 3-NT from 500 nM to 1 mM, yielding a limit of detection of 22.3 nM. Finally, the applicability of the (bio)sensor was tested by performing calibration assays in human urine samples and a good performance was obtained in terms of sensitivity, selectivity and reproducibility. Overall, the attributes of the herein described sensing approach can be compared to a very limited number of other electrochemical devices, that are still using a conventional three electrode system, making this paper-sustained device the first electrochemical (bio)sensor with potential to become a portable and low-cost diagnostic tool for 3-NT. In general, the incorporation of molecular imprinting technology coupled to electrochemical transduction enabled the fabrication of suitable smart sensors for wide screening approaches.

2020Journal article

Open access

Paper-Based Platform with an In Situ Molecularly Imprinted Polymer for β-Amyloid

Publication . Pereira, Marta V.; Marques, Ana C.; Oliveira, Daniela; Martins, Rodrigo; Moreira, Felismina; Sales, Maria Goreti Ferreira; Fortunato, Elvira

Alzheimer’s disease (AD) is one of the most common forms of dementia affecting millions of people worldwide. Currently, an easy and effective form of diagnosis is missing, which significantly hinders a possible improvement of the patient’s quality of life. In this context, biosensors emerge as a future solution, opening the doors for preventive medicine and allowing the premature diagnosis of numerous pathologies. This work presents a pioneering biosensor that combines a bottom-up design approach using paper as a platform for the electrochemical recognition of peptide amyloid β-42 (Aβ-42), a biomarker for AD present in blood, associated with visible differences in the brain tissue and responsible for the formation of senile plaques. The sensor layer relies on a molecularly imprinted polymer as a biorecognition element, created on the carbon ink electrode’s surface by electropolymerizing a mixture of the target analyte (Aβ-42) and a monomer (O-phenylenediamine) at neutral pH 7.2. Next, the template molecule was removed from the polymeric network by enzymatic and acidic treatments. The vacant sites so obtained preserved the shape of the imprinted protein and were able to rebind the target analyte. Morphological and chemical analyses were performed in order to control the surface modification of the materials. The analytical performance of the biosensor was evaluated by an electroanalytical technique, namely, square wave voltammetry. For this purpose, the analytical response of the biosensor was tested with standard solutions ranging from 0.1 ng/mL to 1 μg/mL of Aβ-42. The linear response of the biosensor went down to 0.1 ng/mL. Overall, the developed biosensor offered numerous benefits, such as simplicity, low cost, reproducibility, fast response, and repeatability less than 10%. All together, these features may have a strong impact in the early detection of AD.

2020-05Journal article

Open access