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Mercury (Hg) is a toxic element which impacts on biological systems and ecosystems. Because the toxicity of Hg species is highly dependent on their concentration levels and chemical forms, the sensitive identification of the chemical forms of Hg—i.e., Hg speciation—is of major significance in providing meaningful information about the sources of Hg exposure. In this study, a microfluidic-based device made of high-clarity poly(methyl methacrylate) (PMMA) was fabricated. Then, titanium dioxide nanoparticles (nano-TiO2s) were attached to the treated channel’s interior with the aid of poly(diallyldimethylammonium chloride) (PDADMAC). After coupling the nano-TiO2-coated microfluidic-based photocatalyst-assisted reduction device (the nano-TiO2-coated microfluidic-based PCARD) with high-performance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICP-MS), a selective and sensitive, hyphenated system for Hg speciation was established. Validation procedures demonstrated that the method could be satisfactorily applied to the determination of mercury ions (Hg2+) and methylmercury ions (CH3Hg+) in both human urine and water samples. Remarkably, the zeta potential measured clearly indicated that the PDADMAC-capped nano-TiO2s with a predominance of positive charges indeed provided a steady force for firm attachment to the negatively charged device channel. The cause of the durability of the nano-TiO2-coated microfluidic-based PCARD was clarified thus.

Flexible electrochemical supercapacitors (FESCs) are emerging as innovative energy storage systems, characterized by their stable performance, long cycle life, and portability/foldability. Crucial components of FESCs, such as electrodes and efficient electrolytes, have become the focus of extensive research. Herein, we examine deep eutectic solvent (DES)–based polymer gel systems for their cost-effective accessibility, simple synthesis, excellent biocompatibility, and exceptional thermal and electrochemical stability. We used a mixture a DES, LiClO4–2-Oxazolidinone as the electroactive species, and a polymer, either polyvinyl alcohol (PVA) or polyacrylamide (PAAM) as a redox additive/plasticizer. This combination facilitates a unique ion-transport process, enhancing the overall electrochemical performance of the polymer gel electrolyte. We manufactured and used LiClO4–2-Oxazolidinone (LO), polyvinyl alcohol–LiClO4–2-Oxazolidinone (PVA–LO), and polyacrylamide–LiClO4–2-Oxazolidinone (PAAM–LO) electrolytes to synthesize an MnO2 symmetric FESC. To evaluate their performance, we analyzed the MnO2 symmetric FESC using various electrolytes with cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The FESC featuring the PVA–LO electrolyte demonstrated superior electrochemical and mechanical performances. This solid-state MnO2 symmetric FESC exhibited a specific capacitance of 121.6 F/g within a potential window of 2.4 V. Due to the excellent ionic conductivity and the wide electrochemical operating voltage range of the PVA–LO electrolyte, a high energy density of 97.3 Wh/kg at 1200 W/kg, and a long-lasting energy storage system (89.7% capacitance retention after 5000 cycles of GCD at 2 A/g) are feasibly achieved. For practical applications, we employed the MnO2 symmetric FESCs with the PVA–LO electrolyte to power a digital watch and a light-emitting diode, further demonstrating their real-world utility.

Herein, the nanostructured polypyrrole-coated MnO2 nanofibers growth on carbon cloth (PPy-MnO2-CC) to serve as the electrodes used in conjunction with a quasi-ionic liquid-based polymer gel electrolyte (urea-LiClO4-PVA) for solid-state symmetric supercapacitors (SSCs). The resultant PPy-MnO2-CC solid-state SSCs exhibited a high specific capacitance of 270 F/g at 1.0 A/g in a stable and wide potential window of 2.1 V with a high energy/power density (165.3 Wh/kg at 1.0 kW/kg and 21.0 kW/kg at 86.4 Wh/kg) along with great cycling stability (capacitance retention of 92.1% retention after 3000 cycles) and rate capability (141 F/g at 20 A/g), exceeding most of the previously reported SSCs. The outstanding performance of the studied 2.1 V PPy-MnO2-CC flexible SSCs could be attributed to the nanostructured PPy-coated MnO2 composite electrode and the urea-LiClO4-PVA polymer gel electrolyte design. In addition, the PPy-MnO2-CC solid-state SSCs could effectively retain their electrochemical performance at various bending angles, demonstrating their huge potential as power sources for flexible and lightweight electronic devices. This work offers an easy way to design and achieve light weight and high-performance SSCs with enhanced energy/power density.

The specific energy of an aqueous carbon supercapacitor is generally small, resulting mainly from a narrow potential window of aqueous electrolytes. Here, we introduced agarose, an ecologically compatible polymer, as a novel binder to fabricate an activated carbon supercapacitor, enabling a wider potential window attributed to a high overpotential of the hydrogen-evolution reaction (HER) of agarose-bound activated carbons in sulfuric acid. Assembled symmetric aqueous cells can be galvanostatically cycled up to 1.8 V, attaining an enhanced energy density of 13.5 W h/kg (9.5 µW h/cm2) at 450 W/kg (315 µW/cm2). Furthermore, a great cycling behavior was obtained, with a 94.2% retention of capacitance after 10,000 cycles at 2 A/g. This work might guide the design of an alternative material for high-energy aqueous supercapacitors.

Apigenin (Apig) is used as a model drug due to its many beneficial bio-activities and therapeutic potentials. Nevertheless, its poor water solubility and low storage stability have limited its application feasibility on the pharmaceutical field. To address this issue, this study developed nanoemulsions (NEs) using an anti-oxidative polymeric amphiphile, d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), hydrogenated soy lecithin (HL), black soldier fly larvae (BSFL) oil, and avocado (AV) oil through pre-homogenization and ultrasonication method. Addition of TPGS (weight ratios 100 and 50% as compared to HL) into NEs effectively reduced particle size and phase transition region area of NEs with pure HL. Incorporation of Apig into NEs made particle size increase and provided a disorder effect on intraparticle molecular packing. Nevertheless, the encapsulation efficiency of NEs for Apig approached to about 99%. The chemical stability of Apig was significantly improved and its antioxidant ability was elevated by incorporation with BSFL oil and AV oil NEs, especially for NEs with single TPGS. NEs with single TPGS also exhibited the best Apig skin deposition. For future application of topical Apig delivery, NEs-gel was formed by the addition of hyaluronic acid (HA) into NEs. Their rheological characteristics were dominated by the surfactant ratios of HL to TPGS.

In this work, we successfully fabricated 3D network vanadium oxide (VOx) and manganese oxide (MnOx) nanofibers on conductive paper (PVA-acetamide-LiClO4-graphite/paper, PGP) as electrodes linked with an eco-friendly PVA-acetamide-LiClO4 (PAL) deep eutectic solvent-based gel electrolyte for high-voltage wearable asymmetric supercapacitors (HVWASCs). An ecologically compatible deep eutectic solvent-based electrolyte with self-supporting electroactive species has been generally accepted as a unique type of cost-effective and green electrolyte that possibly involves a bulk concentration of the electroactive species and a large working potential window, thereby achieving a high performance. The HVWASCs are able to work with a large operating voltage of 4.2 V, and supply outstanding energy and power densities (245 W hkg-1 at 0.18 W kg-1 and 95.3 kW kg-1 at 98 W h kg-1). The HVWASCs demonstrate remarkable cycling stability and durability after 6000 cycles, including bending and twisting (capacitance retention of 91.5%). The HVWASCs are a superior prospective candidate for wearable/flexible electronic devices and Internet of Things (IoT) applications. [ABSTRACT FROM AUTHOR]

We employed a polymeric material, poly(methyl methacrylate) (PMMA), for fabricating a microdevice and then implanted the chlorine (Cl)-containing solid-phase extraction (SPE) functionality into the PMMA chip to develop an innovative on-chip dipole-assisted SPE technique. Instead of the ion-ion interactions utilized in on-chip SPE techniques, the dipole-ion interactions between the highly electronegative C - C l moieties in the channel interior and the positively charged metal ions were employed to facilitate the on-chip SPE procedures. Furthermore, to avoid labor-intensive manual manipulation, a programmable valve manifold was designed as an interface combining the dipole-assisted SPE microchip and inductively coupled plasma-mass spectrometry (ICP-MS) to achieve the fully automated operation. Under the optimized operation conditions for the established system, the detection limits for each analyte ion were obtained based on three times the standard deviation of seven measurements of the blank eluent solution. The limits ranged from 3.48 to 20.68 ng L-1, suggesting that this technique appears uniquely suited for determining the levels of heavy metal ions in natural water. Indeed, a series of validation procedures demonstrated that the developed method could be satisfactorily applied to the determination of trace heavy metals in natural water. Remarkably, the developed device was durable enough to be reused more than 160 times without any loss in its analytical performance. To the best of our knowledge, this is the first study reporting on the combination of a dipole-assisted SPE microchip and elemental analysis instrument for the online determination of trace heavy metal ions. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of anodically deposited Mn oxide was studied in three ionic liquids (ILs): 2-methylpyridine–trifluoroacetic acid (P–TFA), 1-ethyl-3-methylimidazolium–dicyanamide (EMI–DCA), and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI–BF4). In the aprotic and low-viscosity EMI–DCA IL, ideal pseudocapacitive behavior of the oxide electrode was observed; the specific capacitance, measured using cyclic voltammetry at a sweep rate of 5 mV/s, was 72 F/g. The operation potential window was as wide as 2 V, which is double that found in traditional aqueous electrolytes. Moreover, electrochemical stability of the Mn oxide electrode in EMI–DCA IL was excellent; after 600 redox cycles, the capacitance barely decayed. The charge storage mechanism of Mn oxide in the IL was examined using X-ray photoelectron spectroscopic (XPS) analyses. The results reveal that DCA−, instead of EMI+, is the primary working ion that penetrates into the oxide and compensates the Mn valent state variation. This is the first study that provides a detailed explanation of the pseudocapacitive properties of Mn oxide in IL. [ABSTRACT FROM AUTHOR]

The electrochemistry of manganese was studied at a polycrystalline platinum disk electrode in the hydrophilic ionic liquid N-butyl-N-methylpyrrolidinium dicyanamide (BMP-DCA). The density and absolute viscosity of BMP-DCA were determined over a temperature range from 299.0 to 343.0 K. A polynomial equation describing the temperature dependence of the density is provided. The viscosity obeys the Arrhenius temperature dependence. The dicyanamide anion exhibits a good complexing ability toward transition metal ions, and, therefore, Mn(II) species can be introduced into the ionic liquid either by anodic dissolution of a manganese electrode or by dissolution of manganese (II) chloride. Cyclic voltammograms indicated that the electrodeposition of Mn from Mn(II) was preceded by an overpotential-driven nucleation process. When the potential scan was reversed, the anodic stripping wave was fairly smaller than the cathodic wave, indicating that the oxidation of the Mn electrodeposits was kinetically hindered. However, this behavior was less noticeable for massive Mn electrodeposits. Manganese coatings were prepared at copper substrates by controlled-potential electrodeposition and characterized by scanning electron microscope, energy-dispersive spectrometer (EDS), and powder X-ray diffraction spectrometer (XRD). EDS analysis indicated that the purity of the Mn electrodeposits was good, although no crystal signal of Mn was observed in the XRD patterns. [ABSTRACT FROM AUTHOR]

The potential utility of the air- and water-stable ionic liquid 1-ethyl-3-methylimidazolium dicyanamide (EMI-DCA) for electrochemical application was evaluated with copper(I) chloride. The temperature dependency of the density and absolute viscosity of EMI-DCA were measured over a temperature range from 297 to 343 K, and equations describing the dependencies are presented. Due to the ligand property of the DCA anion, both CuCl and CuCl2 are soluble in EMI-DCA. Cyclic voltammograms of Cu(I) in EMI-DCA and other two ionic liquids were compared. Cu(l) can be oxidized to Cu(II) or reduced to Cu metal in these solutions. The electrodeposition of Cu on glassy carbon and nickel electrodes involves a three-dimensional progressive nucleation and growth process. Scanning electron microscopy and X-ray diffraction results indicate that the morphology of the copper electrode-posits is dependent on the deposition potential, and compact coatings containing nanocrystalline copper could be obtained by potentiostatic electrolysis at low overpotentials. The low viscosity of EMI-DCA and the high solubility of metal chlorides in it would facilitate the electrodeposition of metals using this ionic liquid. [ABSTRACT FROM AUTHOR]

A metallic aluminum (Al) layer was successfully electrodeposited onto a magnesium (Mg) alloy in a Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl3-EMIC) ionic liquid under a galvanostatic condition at room temperature. Effects of deposition current density on material characteristics of the deposited layers were explored by means of a scanning electron microscope and an X-ray diffractometer. In addition, the improvement in corrosion resistance of the Mg alloy due to the Al coating was evaluated by electrochemical measurements and a salt spray test. The electrochemical impedance spectroscopic data indicated that a bare Mg alloy had a polarization resistance of only 470 Ω cm² in 3.5 wt % NaCl solution, whereas the Al-coated Mg sample showed its resistance as high as 8700 Ω cm² in the same environment. Moreover, it was also found that the Al layer deposited at a lower current density was more compact and uniform when compared to that deposited at a higher current density; consequently, this coating revealed a superior protection capability for the Mg substrate against corrosion. [ABSTRACT FROM AUTHOR]