Application of a microfluidic electronic tongue based on impedance spectroscopy for coconut water analysis.

The food industry has grown with the demands for new products and their authentication, which has not been accompanied by the area of analysis and quality control, thus requiring novel process analytical technologies for food processes. An electronic tongue (e-tongue) is a multisensor system that can characterize complex liquids in a fast and simple way. Here, we tested the efficacy of an impedimetric microfluidic e-tongue setup - comprised by four interdigitated electrodes (IDE) on a printed circuit board (PCB), with four pairs of digits each, being one bare sensor and three coated with different ultrathin nanostructured films with different electrical properties - in the analysis of fresh and industrialized coconut water. Principal Component Analysis (PCA) was applied to observe sample differences, and Partial Least Squares Regression (PLSR) was used to predict sample physicochemical parameters. Linear Discriminant Analysis (LDA) and Partial Least Square - Discriminant Analysis (PLS-DA) were compared to classify samples based on data from the e-tongue device. Results indicate the potential application of the microfluidic e-tongue in the identification of coconut water composition and determination of physicochemical attributes, allowing for classification of samples according to soluble solid content (SSC) and total titratable acidity (TTA) with over 90% accuracy. It was also demonstrated that the microfluidic setup has potential application in the food industry for quality assessment of complex liquid samples.

Influence of solvents on the morphology of Langmuir and Langmuir-Schaefer films of PCBM and PCBM-based oligomers and polymers.

Fullerene-based polymers and oligomers combined with non-fullerene acceptors show extremely high efficiencies in organic photovoltaic devices. Furthermore, fullerene-based materials are of interest for use in anti-cancer and anti-viral treatments, where their presence can enhance the efficacy of medication considerably. Therefore, it remains important to understand their morphology and electronic properties to improve devices and technological applications. The main goal of this study is to prepare and characterize Langmuir and Langmuir-Schaefer films of PCBM-based materials to investigate the influence of different solvents such as chloroform, toluene, and xylene, and co-components on their morphology. PCBM-based materials were thus studied either alone or in mixtures with a polythiophene derivative (poly(3-hexythiophene), P3HT) commonly used in organic photovoltaic devices. The formation of Langmuir films was studied using surface pressure isotherms and Brewster's angle microscopy (BAM), where the homogeneity, phase behavior, and morphology of the films were investigated. In addition, Langmuir-Schaefer films were characterized by UV-visible absorption spectroscopy, atomic force microscopy (AFM), and Raman spectroscopy, providing information on the morphology of the solid films. This study has shown that it is possible to successfully fabricate Langmuir and Langmuir-Schaefer films of PCBM and PCBM-based oligomers and polymers, both pure and in mixtures with P3HT, to compare their organization, roughness, and optical properties. With the Langmuir films, it was possible to estimate the area of the molecules and visualize their aggregation through BAM images, establishing a relationship between the area occupied by these materials and the solvent used. All characterization techniques corroborate that the use of chloroform significantly reduced the roughness of the LS films mixed with P3HT and also presented a higher ordering compared to films prepared with xylene solutions.

Supramolecular architecture and electrical conductivity in organic semiconducting thin films.

Organic thin films are an essential component of the structure of optical and electronic devices. However, the optical and electrical properties of these films depend on their supramolecular architecture, which may vary according to the techniques used to manufacture them. Here, the correlation between conductivity and supramolecular architecture was investigated. The supramolecular architecture was analyzed in terms of the molecular organization and J- or H-aggregation established during the fabrication of perylene tetracarboxylic diimide (PTCD) nanometric films. Three deposition techniques, Langmuir-Schaefer (LS), Langmuir-Blodgett (LB), and Physical Vapor Deposition (PVD), were evaluated. The UV-vis absorption spectra indicated that LS, LB, and PVD films grow homogeneously. Also, the presence of J and H aggregates was observed for all films, the H aggregates prevailing for the LB film. The FTIR measurements suggested that the molecular organization is similar for LS and LB films, with a tendency to form head-on organization onto a solid substrate. For the PVD film, the perylene macrocycles are inclined approximately 45° relative to the substrate. AFM measurements indicated a homogenous surface for all films. In terms of electrical conductivity, the highest conductivity was found for LS, followed by LB and PVD. The conductivity values were interpreted in terms of molecular organization and J- or H-aggregate formation.

Regioregularity and deposition effect on the physical/chemical properties of polythiophene derivatives films.

Polythiophene thin films are widely studied for applications in organic electronics. However, some comparisons are still missing, regarding distinct deposition techniques and regioregularity. Here regioregular and regiorandom alkyl-substituted polythiophene derivatives (P3ATs) were deposited on solid substrates using both Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) techniques. The main goal was to verify the possible influence of the regioregularity as well the deposition technique on their optical, electrical and electrochemical properties. LB and LS films of regioregular and regiorandom poly(3-butylthiophene) (P3BT) and poly(3-octylthiophene) (P3OT) were deposited onto glass/Indium-Tin-Oxide) substrates and characterized by UV-visible optical spectroscopy, atomic force microscopy, cyclic voltammetry, and conductivity measurements. The results demonstrated the influence of the deposition technique on the electrical outcome, moreover, the regioregularity affected all the performed characterizations. In addition, this paper may be useful to understand how the amphiphilic molecule addition affected the film properties of regioregular and regiorandom P3ATs, particularly the energy diagram provided by the electrochemical and absorption features.