PEDOT:Nafion for Highly Efficient Supercapacitors.

Supercapacitors offer notable properties as energy storage devices, providing high power density and fast charging and discharging while maintaining a long cycling lifetime. Although poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS) has become a gold standard among organic electronics materials, researchers are still investigating ways to further improve its capacitive characteristics. In this work, we introduced Nafion as an alternative polymeric counterion to PSS to form highly capacitive PEDOT/Nafion; its advantageous supercapacitive properties were further improved by treatment with either dimethyl sulfoxide or ethylene glycol. Accordingly, electrochemical characterization of PEDOT/Nafion films revealed their high areal capacitance (22 mF cm-2 at 10 mV/s) and low charge transfer resistance (∼380 Ω), together with excellent volumetric capacitance (74 F cm-3), Coulombic efficiency (99%), and an energy density of 23.1 ± 1.5 mWh cm-3 at a power density of 0.5 W cm-3, resulting from a more effective ion diffusion inside the conductive film, as confirmed by the results of spectroscopic studies. A proof-of-concept symmetric supercapacitor based on PEDOT/Nafion was characterized with a specific capacitance of approximately 15.7 F g-1 and impressive long-term stability (Coulombic efficiency ∼99% and capacitance ∼98.7% after 1000 charging/discharging cycles), overperforming the device based on PEDOT/PSS.

UV-vis and ECD spectroelectrochemistry of atropisomeric naphthalenediimide derivative.

The UV-vis and ECD spectroelectrochemistry (SEC) of a chiral binaphthalenylamine derivative of the N-butyl naphthalenediimide (NDIB-NH2) enantiomers were applied to measure UV-vis and ECD spectra of NDIB-NH2 radicals and dianion formed in the reduction and oxidation processes observed in cyclic voltammetry (CV). The CV curves and EPR spectroelectrochemistry enabled us to establish conditions at which a radical-anion [NDIB-NH2]̇.-, a dianion [NDIB-NH2]2-, and a radical-cation [NDIB-NH2]̇.+ are formed. The DFT restricted open-shell CAM-B3LYP-D3/def2TZVP/PCM calculations demonstrated that in the radical-anion [NDIB-NH2]̇.-, spin is spread over the NDI system while in the radical-cation [NDIB-NH2]̇+ it is spread over the aminonaphthalene moiety. The UV-vis spectra of radical-anion and dianion show the most significant changes in the 400-800 nm range. In that range, the ECD spectra varied with the change of electrode potential more than the UV-vis did and enabled the identification of a new ECD band of [NDIB-NH2]̇.- at ca. 400 nm hidden in the background in the UV spectra at -1000 mV. A broad structured ECD pattern with a maximum at ca. 530 nm was observed for [NDIB-NH2]̇.- (-1000 mV), while a single smooth ECD band of [NDIB-NH2]2- was located at 520 nm (-1750 mV). For the first time, an isosbestic point (455 nm) was found in ECD spectroelectrochemical measurements for the radical-cation [NDIB-NH2]̇.+ in equilibrium with the NDIB-NH2 neutral form. The TD-DFT CAM-B3LYP-D3/6-31G** calculations combined with the hybrid (explicit combined with implicit) solvation model fairly well reproduced the UV-vis and ECD SEC of neutral and redox forms of NDIB-NH2 but the ECD spectrum of [NDIB-NH2]̇.+ above 390 nm.

The Role of Intermolecular Interaction on Aggregation-Induced Emission Phenomenon and OLED Performance.

In this work, the role of intermolecular interaction on the aggregation-induced emission (AIE) phenomenon and organic light-emitting diodes' (OLEDs) performance was investigated. During the research, a group of compounds consisting of the (-CH=C(CN)(COOR)) moiety with identical energy parameters was designed using the DFT approach and successfully synthesized. The optical, electrochemical, and aggregation-induced emission properties were studied. The aggregation-induced emission of compounds has been studied in the mixture of MeCN (as a good solvent) and water (as a poor solvent) with different water fractions ranging from 0% to 99%. Moreover, the time dependence on the AIE feature was also evaluated. Thanks to their molecular structures, almost identical behavior of these substances in dilute solutions was observed. For molecules that exhibit the strong AIE phenomenon, emission efficiency increases rapidly during aggregation. What is also very interesting is it has been shown that by introducing an appropriate substituent, one can control the degree of intermolecular interactions and "control" the length of the emitted wave. Finally, OLEDs were fabricated by the spin-coating/evaporation hybrid method. Devices showed green-blueish electroluminescence (CIE coordinates: 0.107, 0.165) with maximum luminance reaching 25 cd m-2 and EQE reaching 2%.

Solvent-Impregnated Sorbents for Tantalum from Niobium Separation Using a Fixed-Bed Column.

Reactor-grade niobium steel is used as a construction material for nuclear reactors. In this case, the presence of tantalum, which is characterized by a 20 times higher active cross section for capturing thermal neutrons than the cross section of niobium (181Ta: 21.3 barn), cannot exceed 100 ppm. Analytical methods for quality and new separation method development control need very pure niobium matrices-niobium compounds with a low tantalum content, which are crucial for preparing matrix reference solutions or certified reference materials (CRMs). Therefore, in this paper, a new, efficient method for separating trace amounts of Ta(V) from Nb(V) using extraction chromatography with the use of sorbents impregnated with methyl isobutyl ketone MIBK solvent is proposed. Various types of MIBK-impregnated sorbents were used (AG® 1-X8 Anion Exchange Resin, AMBERLITE™ IRC120 Na Ion Exchange Resin, SERVACEL® Cellulose Anion Exchangers DEAE 52, active carbons of various grain size, carbonized blackcurrant pomace, carbonized chokeberry pomace, bentonite, and polyurethane foam in lumps). The highest tantalum removal efficiency was determined using active coal-based materials (>97%). The separation effectivity of tantalum from niobium was also determined in dynamic studies using a fixed-bed column with MIBK-impregnated active carbon. Solutions of various Nb:Ta weight ratios (1:1, 100:1, 1000:1) were used. The most impressive result was obtaining 70 mL of high purity niobium solution of tantalum content 0.027 ppm (in relation to Nb) with 88.4% yield of niobium from a solution of Nb:Ta, weight ratio 1000:1 (purge factor equaled 35,000). It proves the presented system to be applicable for preparation of pure niobium compounds with very low contents of tantalum.

ECD spectroelectrochemistry: A review.

The electronic circular dichroism (ECD) spectroscopy is probably the most important chiraloptical method, and the role of chirality in contemporary chemistry, pharmacy, and material science constantly increases. On the other hand, the electrochemical methods are also very sensitive tools for studying multivarious redox processes. Nevertheless, the first ECD spectroelectrochemical (SEC) study was only published by Daub, Salbeck and Aurbach in 1988, and since then, the ECD SEC method has been mentioned in only thirty papers. By the summer of 2020, the ECD SEC studies were mainly focused around molecular systems for organic, and marginally, inorganic chiroptical switching studies of biochemical redox reactions. The review provides more details about the ECD SEC studies carried out so far. At the end, we suggest some future applications for the ECD spectroelectrochemistry.

Enantioselective sensing of (S)-Thalidomide in blood plasma with a chiral naphthalene diimide derivative.

Fast, simple in use and highly effective voltammetric enantiosensor dedicated for determination of thalidomide (TD) enantiomers (especially towards the toxic (S)-enantiomer) in blood plasma is still desirable. Here we have proven that newly synthesized chiral naphthalene diimide (NDI) derivatives are excellent electroactive materials for TD enantiosensors. The recognition process relies on the specific interaction between the chiral NDI receptor and the thalidomide enantiomer of the opposite configuration. This unique specific interaction between (S)-thalidomide and (R)-NDI derivative counterparts, evident in the DPV voltammograms, was confirmed by molecular modeling. The demonstrated voltammetric enantiosensors are characterized by the low detection limit at the level of µg·L-1, wide analytical range from 5·10-4 - 10 mg·L-1, high selectivity and long lifetime. The results of the recovery rates showed a very good degree of accuracy towards the determination of (S)-thalidomide in the blood samples, so it can be successfully used in the analysis of clinical samples.

Hybrid Pectin-Based Sorbents for Cesium Ion Removal.

In this paper, beads-shaped hybrid sorbents composed of pectin and Prussian blue were prepared. Various ratios of pectin and Prussian blue in hybrid sorbents were tested. Obtained sorbents had high and roughly constant sorption capacity in a broad pH range (4-10), in which also the swelling index and stability of sorbents were satisfactory. The preliminary sorption studies proved that almost 100% of cesium removal efficiency may be achieved by using the proper sorbent dose. The sorption capacity of the hybrid sorbent with a 1:1 ratio of pectin to Prussian blue equaled q = 36.5 ± 0.8 mg/g (dose 3 g/L, pH = 6, temp. = 22 ± 1 °C, t = 24 h). The obtained results showed that the prepared hybrid pectin-based sorbents are promising for cesium ions removal.

Long Term and Large-Scale Continuous Studies on Zinc(II) Sorption and Desorption on Hybrid Pectin-Guar Gum Biosorbent.

Pectin-guar gum biosorbent was tested for zinc(II) ions removal in column process. Sorption⁻desorption experiments were performed in laboratory and at larger scale. The breakthrough and elution curves were obtained for various conditions. The Bed Depth Service Time model was tested for utility in data estimation. Possibility of sorbent reuse and its lifetime was examined in 20 repeated sorption⁻desorption cycles. Finally, tests were repeated for real wastewater from galvanizing plant, giving satisfactory results. The effectiveness of Zn(II) sorption happened to be dependent on process parameters; tests have proved that it increased with increasing bed height and with decreasing flow rate or grain size. For an initial zinc concentration of 30 mg/L, even 2096 mL of zinc solution could be purified in small scale experiment (2 g of fine grain sorbent and flow rate 60 mL/h) or 5900 L in large-scale (16 kg of large grain sorbent and flow rate 45 L/h). This allowed for 40-fold or 49-fold zinc increases in concentration in one sorption⁻desorption cycle. The most successful results are meant that at least 20 sorption⁻desorption cycles could be performed on one portion of biosorbent without loss of its effectiveness, large-scale tests for real wastewater from galvanizing plant gave satisfactory results, and that the form and mechanical stability of our sorbent is suitable for column usage with flow rates applicable in industry.

Raman and IR Spectroelectrochemical Methods as Tools to Analyze Conjugated Organic Compounds.

In the presented work, two spectroelectrochemical techniques are discussed as tools for the analysis of the structural changes occurring in the molecule on the vibrational level of energy. Raman and IR spectroelectrochemistry can be used for advanced characterization of the structural changes in the organic electroactive compounds. Here, the step-by-step analysis by means of Raman and IR spectroelectrochemistry is shown. Raman and IR spectroelectrochemical techniques provide complementary information about structural changes occurring during an electrochemical process, i.e. allows for the investigation of redox processes and their products. The examples of IR and Raman spectroelectrochemical analysis are presented, in which the products of the redox reactions, both in solution and solid state, are identified.

Hybrid pectin-based biosorbents for zinc ions removal.

In this paper, a set of the hybrid biosorbents, made of pectin and polysaccharide additives (arabic, tragacanth, guar, karaya, xanthan, gellan, carob gums, agar-agar) or lecithin (phospholipid), was investigated and tested for zinc ions removal. The immobilization of the polysaccharides into the pectin matrix was proved by the IR spectroscopy. The structure of the working biosorbents was observed in SEM micrographs. The influence of the additive type and pH on the sorption properties and swelling index was investigated. The maximum sorption capacities were achieved in pH above 4 and ranged from 17.7 to 25.4mg/g for lecithin and xanthan gum as additives, respectively. The results show that the hybrid pectin-based beads are promising biosorbents for zinc removal from aqueous solutions.

New, hybrid pectin-based biosorbents.

In this work hybrid pectin-based biosorbents with secondary polysaccharide additives (gellan, carob and xanthan gum, ratio to pectin 1:1, 1:1 and 1:3, respectively) were obtained at two temperatures. The presence of these additives in prepared beads was confirmed by Raman spectra. The SEM micrographs show better homogeneity of blends and grater differences between structures of beads with various additives obtained at higher temperature. The sorption capacity of our hybrid biosorbents as well as sole pectin sorbent is rather the same, and equals 0.85 and 0.70 mmol/g for lead and cadmium, respectively, in pH 4-6.

Electrochemically Induced Synthesis of Poly(2,6-carbazole).

The formation of a poly(2,6-carbazole) derivative during an electrochemical polymerization process is shown. Comparison of 3,5-bis(9-octyl-9H-carbazol-2-yl)pyridine and 3,5-bis(9-octyl-9H-carbazol-3-yl)pyridine by electrochemical and UV-Vis-NIR spectroelectrochemical measurements and DFT (density functional theory) calculation prove the formation of a poly(2,6-carbazole) derivative. Both of the compounds form stable and electroactive conjugated polymers.