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This manuscript presents the preparation of polymer layers based on polythiophene (PTh) and its 3-substituted derivatives (substituents 4-(CH3O)C6H4 and 4-(CF3)C6H4 marked as PThOCH3 and PThCF3, respectively) on platinum electrodes by cyclic voltammetry (CV). The polymerization process and the morphology of resulting layers were discussed analysing of CV-voltammograms and scanning electron microscopy (SEM), respectively. Subsequently, the prepared polymers were tested as active/sensitive media of two types of sensors: (i) electrochemical sensor detecting ammonia in aqueous environment, whose response was evaluated by electrochemical impedance spectroscopy (EIS); (ii) chemiresistor detecting NH3 in atmosphere, whose response was evaluated by measurement of resistance. It was found that both the physical (morphology, homogeneity, relative thickness) and receptor properties of the polymer layer deposited on electrode surface are significantly affected by the nature of substituent attached to the thiophene ring. The mutual context of ammonia detection in both environments is discussed. [ABSTRACT FROM AUTHOR]

This paper investigates the enhancement of fly ash-based geopolymer with chitosan biopolymer. Unconfined compression and split tensile tests were carried out to investigate the effect of addition of small amount of N-carboxymethyl chitosan (0.05, 0.1, 0.15, and 0.2 wt% of fly ash) on the mechanical performance of fly ash-based geopolymer. Scanning electron microscopy (SEM) imaging was also conducted to study the microstructure of the chitosan enhanced fly ash-based geopolymer. The results indicated that the inclusion of N-carboxymethyl chitosan led to slight increase of the unconfined compressive strength and substantial increase of the tensile strength, the displacement at the peak tensile load and the pre-peak toughness, with the maximum increases at 0.1 wt% chitosan content. The SEM imaging indicated that the added N-carboxymethyl chitosan biopolymer coated and bridged the (geopolymerized) fly ash particles and led to the formation of a more condensed geopolymer network structure, thus enhancing the mechanical behavior of the geopolymer-biopolymer composite. However, when too much N-carboxymethyl chitosan was used, the excessive coating and encapsulation of un-reacted and partially hydrolyzed fly ash particles hindered their geopolymerization and adversely affected the mechanical behavior of the geopolymer-biopolymer composite. [ABSTRACT FROM AUTHOR]