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Wireless chemical sensors are increasingly finding use as analytical devices in healthcare diagnostics, wearable sensing (sweat analysis) and in the rapidly emerging area of the Sensor Internet of Things (SIoT). In such wireless scenarios, the application of fluorescence-based sensors is lagging behind other types of transduction mechanisms. In this work a new low-cost and highly portable wireless fluorimeter for optical chemical fluorescence intensity measurements is presented (bill-of-materials approximately €20). The fluorimeter is programmed and communicates wirelessly with mobile devices or personal computers by radio-frequency identification (RFID) or near-field communication (NFC). This novel mobile analytical system is highly adaptable for use with different fluorescent sensor chemistries and analytes. The fluorimeter has been evaluated in the laboratory in two sets of proof-of-concept experiments: firstly fluorimetry in solution, where the fluorescence intensities of fluorescein were recorded, and secondly chloride sensing via a paper-immobilised quinine sulphate fluorescent indicator. The latter represents the first demonstration of wireless (radio-frequency) fluorescence-based chloride sensing. Satisfactory analytical performance was achieved in the entire range of sweat chloride concentrations. The wireless fluorimeter system presented here could make a significant contribution to several emerging areas of mobile chemical sensor research, including wearable sensors for healthcare and sport, mobile point-of-sample diagnostics as well as more generally for the Sensor Internet of Things.

Ecological viticulture represent an upward trend in many countries. Unlike conventional viticulture, it avoids the use of chemical fertilizers and other additives, minimizing the impact of chemicals on the environment and human health. The aim of this study was to investigate the influence of nanofiltration (NF) process on volatiles and chemical composition of conventional and ecological Cabernet Sauvignon red wine. The NF process was conducted on laboratory Alfa Laval LabUnit M20 (De Danske Sukkerfabrikker, Nakskov, Denmark) equipped with six NF M20 membranes in a plate module, at two temperature regimes, with and without cooling and four pressures (2.5, 3.5, 4.5 and 5.5 MPa). Different processing parameters significantly influenced the permeate flux which increased when higher pressure was applied. In initial wines and obtained retentates, volatile compounds, chemical composition and elements concentration were determined. The results showed that the higher pressure and retentate cooling was more favourable for total volatiles retention than lower pressure and higher temperature. Individual compound retention depended on its chemical properties, applied processing parameters and wine composition. Nanofiltration process resulted in lower concentrations of ethanol, acetic acid (&gt, 50%), 4-ethylphenol and 4-ethylguaiacol (&gt, 90%). Different composition of initial feed (conventional and ecological wine) had an important impact on retention of elements.

The exploitation of silver nanoparticles (AgNPs) in biomedicine represents more than one third of their overall application. Despite their wide use and significant amount of scientific data on their effects on biological systems, detailed insight into their in vivo fate is still lacking. This study aimed to elucidate the biotransformation patterns of AgNPs following oral administration. Colloidal stability, biochemical transformation, dissolution, and degradation behaviour of different types of AgNPs were evaluated in systems modelled to represent biological environments relevant for oral administration, as well as in cell culture media and tissue compartments obtained from animal models. A multimethod approach was employed by implementing light scattering (dynamic and electrophoretic) techniques, spectroscopy (UV–vis, atomic absorption, nuclear magnetic resonance) and transmission electron microscopy. The obtained results demonstrated that AgNPs may transform very quickly during their journey through different biological conditions. They are able to degrade to an ionic form and again reconstruct to a nanoparticulate form, depending on the biological environment determined by specific body compartments. As suggested for other inorganic nanoparticles by other research groups, AgNPs fail to preserve their specific integrity in in vivo settings., This study was based upon a collaborative work from COST Action CA 17140 "Cancer Nanomedicine from the Bench to the Bedside" supported by COST (European Cooperation in Science and Technology). It was financially supported by the Croatian Science Foundation (grant number HRZZ-IP-2016-06-2436), the Ministerio de Ciencia e Innovacion and Fondo Social Europeo/Agencia Estatal de Investigación (Spain, grant BIO2017-84246-C2-1-R and Ramón y Cajal subprogram, grant RYC-2015-17640), Fondo Social de la DGA (grupos DGA).

The increased utilization of one-dimensional (1D) TiO2 and titanate nanowires (TNWs) in various applications was the motivation behind studying their stability in this work, given that stability greatly influences both the success of the application and the environmental impact. Due to their high abundance in aqueous environments and their rich technological applicability, surfactants are among the most interesting compounds used for tailoring the stability.The aim of this paper is to determine the influence of surfactant molecular structure on TNW stability/aggregation behavior in water and aqueous NaBr solution by dynamic and electrophoretic light scattering. To accomplish this, two structurally different quaternary ammonium surfactants (monomeric DTAB and the corresponding dimeric 12-2-12) at monomer and micellar concentrations were used to investigate TNW stability in water and NaBr. It was shown that TNWs are relatively stable in Milli-Q water. However, the addition of NaBr induces aggregation, especially as the TNW mass concentration increases. DTAB and 12-2-12 adsorb on TNW surfaces as a result of the superposition of favorable electrostatic and hydrophobic interactions. As expected, the interaction of TNWs with 12-2-12 was stronger than with DTAB, due to the presence of two positively charged head groups and two hydrophobic tails. As a consequence of the higher adsorption of 12-2-12, TNWs remained stable in both media, while DTAB showed an opposite behavior.In order to gain more insight into changes in the surface properties after surfactant adsorption on the TNW surface, a surface complexation model was employed. With this first attempt to quantify the contribution of the surfactant structure on the adsorption equilibrium according to the observed differences in the intrinsic log K values, it was shown that 12-2-12 interacts more strongly with TNWs than DTAB. The modelling results enable a better understanding of the interaction between TNWs and surfactants as well as the prediction of the conditions that can promote stabilization or aggregation.

In this paper, we emphasized the dual application of Cu-modified vertically aligned TiO2 nanotube arrays as photocatalyst and a relative humidity sensor. The TiO2 nanotube arrays were obtained by anodization of the titanium layer prepared using radio frequency magnetron sputtering (RFMS) and modified with different copper concentrations (0.5, 1, 1.5, and 2 M) by a wet-impregnation method. The sample modified with 2 M Cu(NO3)2 solution showed the highest efficiency for the NH3 photocatalytic degradation and the most pronounced humidity response in comparison to the other studied samples. In order to investigate the structure and impact of Cu modification, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) were used. The photocatalytic activity and the kinetic study of ammonia oxidation were studied in a mini-photocatalytic wind tunnel reactor (MWPT), while relative humidity sensing was examined by impedance spectroscopy (IS). Higher NH3 oxidation was a direct consequence of the increased generation of •OH radicals obtained by a more efficient photogenerated charge separation, which is correlated with the increase in the DC conductivity.

CaCO3 precipitation is physical-chemical basis of biomineral formation of hard tissue (shells, skeletons) in marine calcifying organisms (=biomineralization). Processes controlling biomineralization are still not fully clarified, so the study of influence of pH on basic processes of CaCO3 precipitation should contribute to better understanding of biomineralization under climate change. This paper reports on the effect of initial pH (pH0) and type of stirring (mechanical and magnetical) on spontaneous precipitation and phase composition, size and morphology of spontaneously precipitated CaCO3 formed at the identical initial supersaturation, ionic strength and a(Ca2+)/a(CO32−) ratio. The initial pH varied in a range 8.50 ≤ pH0 ≤ 10.50 and included values relevant for mimicking the conditions related to biomineralization in marine organisms. In all systems two CaCO3 polymorphs were found: calcite and/or vaterite. The increase of pH0 favoured the formation of rhombohedral calcite no matter the type of stirring. This was exclusively influenced by the systems’ pH0 (other relevant initial parameters were identical). Furthermore, increase of pH0 caused change of vaterite morphology from cauliflower-like spheroids to regular spherulites. The mechanically stirred systems produced larger calcite and vaterite particles and higher content of calcite.

U radu je dan pregled pojmova i jednadžbi vezanih uz određivanje zabranjene zone metodom difuzne refleksijske spektroskopije i uporabu Taucova grafičkog prikaza. Kako bi se demonstrirao postupak i vrednovala sama metoda, primjenom metode određena je zabranjena zona komercijalnih uzoraka anatasa, rutila, cinkita i hematita. Na temelju eksperimentalno dobivenih vrijednosti širine zabranjene zone komentirana je točnost metode te osjetljivost pri razlikovanju poluvodiča s direktnim i indirektnim prijelazima. Pokazano je da Taucova metoda nije besprijekorna niti u pogledu točnosti niti razlikovanja indirektnih i direktnih elektronskih prijelaza u poluvodičkim materijalima, ali je vrlo praktičan način određivanja širine zabranjene zone poluvodiča budući da ne zahtijeva pretjerano skupu instrumentaciju a obrada eksperimentalnih podataka relativno je jednostavna. For the application of semiconductors, an important factor is the band gap, i.e., the minimum energy required for the transfer of electrons from the valence to the conduction band. One of the possible methods for band gap determination is diffuse reflectance spectroscopy and Tauc plot. In this paper, an overview of the terms and equations related to the said method is given, as well as its utilization in the determination of band gaps of commercial samples of various metal oxides. Thus, the procedure is demonstrated and evaluated through the determination of indirect and direct band gap values of anatase (TiO2), rutile (TiO2), zincite (ZnO), and hematite (Fe2O3). All samples were beforehand analysed and identified by X-ray powder diffraction on Shimadzu XRD 6000 diffractometer with CuKα radiation working in a step scan mode with steps of 0.02° and counting time of 0.6 s. It was determined that all samples are well crystallized with relatively large crystallite sizes. UV-Vis spectra of the samples, as well as barite, which was used as a reference, were obtained on the UV-Vis spectrometer with an integrating sphere in total reflectance mode. The UV-Vis DRS spectra were transformed to Kubelka-Munk function, after which Tauc plot was used for the determination of the indirect and direct band gap values of all samples. The obtained values for anatase were 3.20 eV for indirect transition and 3.41 eV for direct transition, and for rutile 3.00 eV for indirect transition and 3.11 eV for direct transition. The zincite sample showed an indirect band gap of 3.19 eV and direct band gap of 3.25 eV, while the obtained indirect band gap value for hematite was 1.96 eV and direct band gap value 2.15 eV. As may be seen, the method is not particularly useful when distinguishing direct from indirect semiconductors, since, for all samples, the curves in Tauc plot for both indirect and direct electron transitions possess a linear dependence region from which the band gap value is estimated. However, the obtained band gap values for all the studied semiconductors are in relatively good concordance with literature references. The method is perhaps most useful in monitoring the variation of band gap depending on the dopant content. Namely, the studied metal oxides are used in photocatalysis where the addition of dopants is expected to reduce the band gap to visible light area, and thus improve the photocatalytic activity of the semiconductor. It can be concluded that the Tauc method is not perfect in terms of accuracy and differentiation between indirect and direct electron transitions in semiconductors. Nevertheless, it is a very practical way of band gap assessment for semiconducting materials, because it requires no excessively expensive instrumentation, and the processing of experimental data is rather simple.

Amorphous calcium carbonate (ACC) and calcium phosphate (ACP) increasingly attract attention as initial solid phases in vertebrate and invertebrate hard tissue formation, as well as in materials science as a possible new synthetic route for advanced materials preparation. Although much is known about these two amorphous phases and similarities in the mechanisms of their formation are recognized, no attempt has been made to investigate their formation under defined and comparable initial experimental conditions viz supersaturation, constituent ions ratio, ionic strength and presence of relevant inorganic additives. In this paper, the formation of ACC and ACP in three model precipitation systems of increased chemical complexity were investigated: (a) systems containing constituent ions, (b) systems containing additional co-ions, and (c) systems with higher ionic strength and addition of Mg2+. The results have shown that ACP is more stable and was formed at lower relative supersaturations in comparison to ACC. The precipitation domain of both phases expanded with increasing complexity of precipitation systems, with the ACP precipitation domains always being larger than that of ACC. In addition to stability, the presence of inorganic ions, especially Mg2+, influences the composition of both amorphous phases. The obtained results indicate that general similarity between ACC and ACP exists, but it could also be concluded that similar chemical environment in which they form not necessary lead to similar structural properties.

Polimeri i polimerni materijali već su dugi niz godina prisutni u farmaceutskoj industriji, gdje se primjenjuju kao pomoćne tvari za oblikovanje konvencionalnih lijekova ili za izradu ambalaže za lijekove. Međutim sve je veća primjena polimera u naprednim terapijskim sustavima, gdje je oslobađanje djelatne tvari kroz dulje razdoblje kontrolirano najvećim dijelom brzinom degradacije polimera. Poželjno je da polimeri koji se unose u tijelo čovjeka budu biorazgradljivi, a to znači da s vremenom potpuno degradiraju na netoksične produkte koji se mogu prirodnim putem izlučiti iz organizma. Također, moraju biti i biokompatibilni, pri čemu u dodiru s organizmom ne izazivaju neželjene nuspojave iako se u tkivu mogu zadržati dulje vrijeme. Tako dizajnirani kompleksni terapijski sustavi u kojima su polimeri funkcionalne djelatne tvari imaju brojne prednosti kao što je jednostavnost i lokaliziranost primjene, produljeno i kontrolirano vrijeme djelovanja lijeka, što znatno smanjuje učestalost primjene. Na taj način smanjena je mogućnost javljanja neželjenih nuspojava, s ciljem poboljšanja kvalitete života pacijenata. Postoje različito dizajnirani sustavi za dostavu lijeka, a njihov pregled te mehanizam djelovanja bit će opisani u sklopu ovog rada zajedno s istaknutom ulogom polimera za svaki pojedini sustav. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna., Polymers and polymeric materials have been used in the pharmaceutical industry for many years and play an indispensable role as excipients in the development of the conventional dosage forms or for manufacturing various drug packaging materials. In recent years, their important application resides in the development of sophisticated drug delivery systems where the release of the drug over a longer time period is mainly controlled by degradation kinetics of the applied polymer. It is preferable that polymers introduced into the human body be biodegradable, meaning that they should eventually completely decompose to nontoxic products that can be naturally excreted from the body. In addition, they should be biocompatible, and in contact with the living organism, should not cause undesirable side effects, although their retention in the tissue could be for a longer time. Such designed complex drug delivery systems where polymers are used as functional excipients have numerous advantages, such as simplicity of administration and targeted drug delivery to the desired site, extended and controlled release, which reduces frequency of drug administration. This can consequently lead to reducing adverse side effects of administered drugs and improvement of patient compliance. There is a range of differently designed drug delivery systems and their description and mechanism of action will be presented in this paper together with the prominent role of the polymers for each particular system. This work is licensed under a Creative Commons Attribution 4.0 International License.

U ovom radu istraživan je učinak dodatka višestjenih ugljikovih nanocjevčica (MWCNT) te MWCNT-a modificiranog skupinama COOH (MWCNT-COOH) u rasponu masenih udjela od 0 do 4 % na svojstva poliuretana. Uzorci nanokompozita pripravljani su dispergiranjem nanopunila u otopini poliuretana u acetonu te polaganim isparavanjem otapala pri sobnoj temperaturi. Utjecaj punila na mehanička svojstva kompozita ispitan je testom jednoosnog istezanja, a električna provodnost uzoraka određivana je metodom četiri kontakta. Toplinska postojanost istražena je termogravimetrijskom analizom (TGA). Obje vrste punila MWCNT povećavaju modul, ali snižavaju prekidnu čvrstoću i prekidno istezanje kompozita. Rezultati ispitivanja električne provodnosti pokazali su da se, u odnosu na čisti PU koji ima provodnost reda veličine 10–13 S cm–1, provodnost nanokompozita s masenim udjelom punila MWCNT 0,2 % znatno povećava na vrijednost reda veličine 10–6 S cm–1. Daljnjim povećanjem do masenog udjela obje vrste MWCNT-a 4 %, provodnost se dalje povećava do vrijednosti većih od 10–2 S cm–1. Taj učinak povećanja provodnosti neznatno je jače izražen u sustavima s MWCNT-COOH-om. Rezultati termogravimetrijske analize upućuju na to da se dodatkom obje vrste MWCNT-a znatno poboljšava toplinsku postojanost u istraživanom rasponu udjela nanopunila, pri čemu je ovaj učinak nešto izraženiji za sustave s punilom MWCNT. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna., In this paper, the influence of multiwalled carbon nanotubes (MWCNT) and carbon nanotubes modified with COOH groups (MWCNT-COOH) on the mechanical and electrical properties as well as on thermal stability of polyurethane (PU) were investigated. The samples of nanocomposite were prepared by dispersion of the nanofiller in a solution of polyurethane in acetone, followed by slow evaporation of the solvent at room temperature. The effect of the fillers on the mechanical properties of PU nanocomposites was examined by the uniaxial deformation test, and electrical properties of the samples were determined by the four probe method. Thermal stability was investigated by thermogravimetric analysis (TGA). The addition of both types of MWCNTs fillers increases modulus (Fig. 1), due to higher modulus of the nanofillers. Due to the better distribution in PU matrix and stronger interactions between COOH groups and carbonyl group in PU matrix, nanocomposites with MWCNT-COOH have higher modulus than nanocomposites with MWCNT filler. Most of the composites have lower strength and elongation at break than PU (Figs. 2 and 3). Smaller MWCNT-COOH aggregates and stronger interactions between this filler and the PU matrix cause less pronounced decreasing of strength at break. Compared to the pure PU, with conductivity of the order of 10–13 S cm–1, the conductivity of the nanocomposite with mass fraction of MWCNT nanofiller 0.2 % substantially increases up to the value of the order 10–6 S cm–1 (Fig. 4). A further increase up to 4 % for both types of MWCNTs, resulted in a further increase in conductivity up to values exceeding 10–2 S cm–1. Due to the better distribution in PU matrix and stronger interactions between COOH groups and carbonyl groups in PU matrix, the conductivity increase effect in systems with MWCNTs-COOH is slightly more pronounced. All investigated nanocomposites have potential applications as electric discharge materials and for electrostatic painting. The results of the thermogravimetric analysis indicate that the addition of both types of MWCNTs significantly improves the thermal stability (Figs. 6 and 7). The maximal degradation rate temperature of polyurethane increased by about 45 °C, thereby this effect is slightly more pronounced for systems with MWCNTs (Fig. 7). This work is licensed under a Creative Commons Attribution 4.0 International License.