The present paper describes the use of a microfluidic system to synthesize carbon dots (Cdots) and their use as optical pH sensors. The synthesis is based on the thermal decomposition of ascorbic ...acid in dimethyl sulfoxide. The proposed microsystem is composed of a fluidic and a thermal platform, which enable proper control of synthesis variables. Uniform and monodispersed 3.3 nm-sized Cdots have been synthesized, the optical characterization of which showed their down/upconversion luminescence and colorimetric properties. The obtained Cdots have been used for pH detection with down and upconverison fluorescent properties as excitation sources. The naked eye or a photographic digital camera has also been implemented as detection systems with the hue parameter showing a linear pH range from 3.5 to 10.2. On the other hand, experiments on the cytotoxicity and permeability of the Cdots on human embryonic kidney cells revealed their adsorption on cells without causing any impact on the cellular morphology.
The paper describes the use of a microfluidic system to synthesize carbon dots and their use as optical pH sensors.
•Novel Na-hybrid electrolytes based on porous NASICON and commercial ionic liquids, has been prepared.•These new hybrid electrolytes present an enhanced conductivity (around 1 mS cm-1 at 30°C) of one ...order of magnitude respect to pore-free sintered NASICON samples•Thinner films of this porous NASICON would permit the manufacture of functional macroporous inorganic separators acting as a Na+ reservoirs.
Lithium-ion batteries are currently the alternative of choice to overcome the increasing demand of energy. However, besides the scarcity of lithium and limited geolocation, it is believed that such batteries have already reached their maximum maturity. Sodium batteries emerge as an alternative to produce the new, so called, post-lithium batteries. In this study, we explore (i) the effect of sodium content and sintering temperature in solid electrolytes based in NASICON-type compounds and (ii) the use of two methodologies to obtain porous NASICON samples: application of natural substances and organic materials as pore-formers and freeze casting. The main purpose is the attainment of hybrid quasi-solid state electrolytes, with enhanced room temperature conductivity, based on porous ceramic electrolyte layers infiltrated with ionic liquids. Using this approach, porous samples with different microstructure and porous morphology and distribution were achieved, providing an enhancement in conductivity (ranging from 0.45 to 0.96 mS cm−1 at 30 °C) of one order of magnitude for infiltrated samples respect to pore-free samples. According to these results the porous NASICON might be considered as a functional macroporous inorganic separator that can act as a Na+ reservoir.
Polysulfone acidic ionomers have been extensively used as Fuel Cell membranes, mainly because of their mechanical, thermal, chemical and electrochemical stability as well as their excellent ...film-forming capability. This contribution deals with the development of blends based on polysulfone-sodium sulfonate and macromolecular/molecular solvents, consisting of poly(oxyethylene), POE, and propylene carbonate, PC, respectively. The objectives were to take advantage of both the thermomechanical performances and the macromolecular polyanions provided by the polysulfone ionomer. Combining POE/PC solvents, didn’t allow obtaining sufficient blend’s conductivities. Nevertheless, the addition of very low amounts of sodium perchlorate led to appreciable conductivities.
This work studies calcium-conducting, solvent-free polymer electrolytes in the framework of today’s post-lithium battery strategies. The samples consist of three calcium salts: (i) Ca(CF3SO3)2; (ii) ...Ca(TFSI)2; and (iii) CaI2 hosted by commercial poly (oxyethylene) (POE). The data collected from X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) indicate that the polymer electrolytes consist of stable macromolecular solutions of these calcium salts. The polymer electrolytes yield conductivities exceeding 0.1 mS cm−1; POE-Ca(CF3SO3)2 reaching, at the moderate concentration O/Ca = 30, a conductivity of 0.47 mS cm−1. This preliminary and fundamental study, which demonstrates the stability of Ca-conducting polymer electrolytes, paves the way to the development of improved polymer electrolytes based on oxyethylene repeat units and new calcium salts.
Sodium-conducting solvent-free polymer electrolytes based on commercially available and inexpensive materials poly(oxyethylene), POE, and three different sodium salts (NaI, NaCF3SO3 and NaClO4) were ...prepared and exhaustively characterized. In order to minimize the environmental impact related to conventional film processing based on casting, a combination of lyophilization and hot-pressing was successfully applied. Contrary to film-casting, this new approach led to very homogeneous and pore-free films. This study suggests the obtained polymer electrolyte films as a promising route to enhance not only ionic conductivity but also mechanical properties. Furthermore, a preliminary work on salt blends hosted by POE shows that they strongly decrease melting point and crystallinity of the polymer electrolytes and paves the way for enhanced sodium-conducting materials.
► Designing plastic antibodies by surface imprinting on silica spheres. ► Plastic antibodies as potentiometric ionophores for antibiotic drugs. ► LTCC Microfluidics coupled to organic-compound ...selective electrodes. ► Simultaneous microfluidic analysis of sulfamethoxazole and trimethoprim.
Monitoring organic environmental contaminants is of crucial importance to ensure public health. This requires simple, portable and robust devices to carry out on-site analysis. For this purpose, a low-temperature co-fired ceramics (LTCC) microfluidic potentiometric device (LTCC/μPOT) was developed for the first time for an organic compound: sulfamethoxazole (SMX).
Sensory materials relied on newly designed plastic antibodies. Sol–gel, self-assembling monolayer and molecular-imprinting techniques were merged for this purpose. Silica beads were amine-modified and linked to SMX via glutaraldehyde modification. Condensation polymerization was conducted around SMX to fill the vacant spaces. SMX was removed after, leaving behind imprinted sites of complementary shape. The obtained particles were used as ionophores in plasticized PVC membranes. The most suitable membrane composition was selected in steady-state assays. Its suitability to flow analysis was verified in flow-injection studies with regular tubular electrodes.
The LTCC/μPOT device integrated a bidimensional mixer, an embedded reference electrode based on Ag/AgCl and an Ag-based contact screen-printed under a micromachined cavity of 600
μm depth. The sensing membranes were deposited over this contact and acted as indicating electrodes. Under optimum conditions, the SMX sensor displayed slopes of about −58.7
mV/decade in a range from 12.7 to 250
μg/mL, providing a detection limit of 3.85
μg/mL and a sampling throughput of 36
samples/h with a reagent consumption of 3.3
mL per sample.
The system was adjusted later to multiple analyte detection by including a second potentiometric cell on the LTCC/μPOT device. No additional reference electrode was required. This concept was applied to Trimethoprim (TMP), always administered concomitantly with sulphonamide drugs, and tested in fish-farming waters. The biparametric microanalyzer displayed Nernstian behaviour, with average slopes −54.7 (SMX) and +57.8
(TMP)
mV/decade. To demonstrate the microanalyzer capabilities for real applications, it was successfully applied to single and simultaneous determination of SMX and TMP in aquaculture waters.
The Upper Carboniferous Sandstone at São Gonçalo do Gurgueia, Northeastern of the Brazil, is notable for its large number of preserved root-like structures. Among these structures it is found ...rhizoliths, fossils of a root system, containing the original cellular material and mineral impregnation and/or mineral replacement. Furthermore, the fossil can present characteristics of preserved anatomical features of the root. The present study shows the physico-chemical characterization results of the mineralized rhizolith (PIC 073.15) from Piauí Formation. This fossil was investigated through X-ray diffraction, X-ray fluorescence, Fourier transform infrared and Raman spectroscopy. The analysis showed that the SiO2 is the main component found in the sample, as demonstrated by the presence of quartz and clay minerals. However, there is also the presence of iron oxides (goethite and hematite) whose content increases from the inner to the outer part. The iron accumulation in PIC 073.15 suggests alternated oxidizing and reduction cycles, indicating humidity's variation of the Piauí Formation environment. The measurements suggest that the first mineralization of the rhizolith occurred through silification process followed by ferruginous precipitations (pos diagenetic process).
The COVID-19 pandemic has been a public health issue around the world in the last few years. Currently, there is no specific antiviral treatment to fight the disease. Thus, it is essential to ...highlight possible prognostic predictors that could identify patients with a high risk of developing complications. Within this framework, miRNA biomolecules play a vital role in the genetic regulation of various genes, principally, those related to the pathophysiology of the disease. Here, we review the interaction of host and viral microRNAs with molecular and cellular elements that could potentiate the main pulmonary, cardiac, renal, circulatory, and neuronal complications in COVID-19 patients. miR-26a, miR-29b, miR-21, miR-372, and miR-2392, among others, have been associated with exacerbation of the inflammatory process, increasing the risk of a cytokine storm. In addition, increased expression of miR-15b, -199a, and -491 are related to the prognosis of the disease, and miR-192 and miR-323a were identified as clinical predictors of mortality in patients admitted to the intensive care unit. Finally, we address miR-29, miR-122, miR-155, and miR-200, among others, as possible therapeutic targets. However, more studies are required to confirm these findings.
The spatial distribution of tiny holes in sheet materials generated by means of electrical discharges is investigated using spatial statistics techniques. It is shown that whereas the holes appear to ...be randomly distributed according to a Poisson point pattern, there is in fact a small region around each hole in which the generation of a new one is statistically inhibited as a consequence of the lower impedance path offered by the already made hole. The resulting pattern is known in spatial statistics as a point process with a soft-core inhibition potential, which can be characterized using the pair correlation function.
► Analysis of electroperforated sheet materials using spatial statistics. ► Deviation from Complete Spatial Randomness (CSR) is detected. ► The inhibition potential is characterized using functional summary estimators.
PDF
