Structural and Electrical Studies of Bi2Se3 Nanomaterials by Solvothermal Method for Thermo-electric Applications

The Bi2Se3 nanoparticles were synthesized by the solvothermal method. The structural and morphological characterization has been done using XRD, HRSEM and Raman while electrical studies at room temperature were analyzed using impedance spectroscopy and cyclic voltmetry. The phase formation was confirmed through XRD measurement and average grain size was found to be 25 nm for as-prepared sample and 37 nm for 650 ºC for 12 hours annealed sample. Raman spectrum appears in the higher frequency range, this is due to stronger bonding forces, i.e the peak at 524 cm− 1 or may arise due to the overtones of A11g and E2g modes. The redox behavior was due to Bi3+ converted into Bi2+ and Bi metallic state. This redox peak was confined the formation of Bi2Se3 nanoparticles. The high temperature electrical conductivity studies were performed as-prepared and annealed sample using impedance spectroscopy.

A prototype device of microliter volume voltammetric pH sensor based on carbazole–quinone redox-probe tethered MWCNT modified three-in-one screen-printed electrode

As an alternate for the conventional glass-based pH sensor which is associated with problems like fragile nature, alkaline error, and potential drift, the development of a new redox-sensitive pH probe-modified electrode that could show potential, current-drift and surface-fouling free voltammetric pH sensing is a demanding research interest, recently. Herein, we report a substituted carbazole-quinone (Car-HQ) based new redox-active pH-sensitive probe that contains benzyl and bromo-substituents, immobilized multiwalled carbon nanotube modified glassy carbon (GCE/MWCNT@Car-HQ) and screen-printed three-in-one (SPE/MWCNT@Car-HQ) electrodes for selective, surface-fouling free pH sensor application. This new system showed a well-defined surface-confined redox peak at an apparent standard electrode potential, Eo′ = − 0.160 V versus Ag/AgCl with surface-excess value, Γ = 47 n mol cm−2 in pH 7 phosphate buffer solution. When tested with various electroactive chemicals and biochemicals such as cysteine, hydrazine, NADH, uric acid, and ascorbic acid, MWCNT@Car-HQ showed an unaltered redox-peak potential and current values without mediated oxidation/reduction behavior unlike the conventional hydroquinone, anthraquinone and other redox mediators based voltammetry sensors with serious electrocatalytic effects and in turn potential and current drifts. A strong π–π interaction, nitrogen-atom assisted surface orientation and C–C bond formation on the graphitic structure of MWCNT are the plausible reasons for stable and selective voltammetric pH sensing application of MWCNT@Car-HQ system. Using a programed/in-built three-in-one screen printed compatible potentiostat system, voltammetric pH sensing of 3 μL sample of urine, saliva, and orange juice samples with pH values comparable to that of milliliter volume-based pH-glass electrode measurements has been demonstrated.

Synchronous Use of Hindakia Sp. For Electricity Generation and Dairy Wastewater Treatment

This paper illustrates the potential of microalgae in electricity production in concurrence with wastewater treatment. In order to explore the potential biogenic algal strains, our study focused on the isolation of microalgal strains from various aquatic sources. Cyclic voltammetry was performed to detect the electrogenic activity and out of 18 algal isolates, six algal strains were screened. The cyclic voltammograms of Hindakia sp from the culture collection revealed the well-defined redox peak in contrast to the other algal strains. The electrogenic Hindakia sp. was also analyzed for their potential to remove nutrients in wastewater treatment. A fifteen days trial under lab scale race way pond was conducted to evaluate the performance of electrogenic algae. A significant decrease in N, P, BOD, COD, and TOC was observed. The removal efficiency of NH4-N, NO3-N, P, BOD, COD and TOC were 90.38, 90.24, 66.75, 67.15, 69.44, and 83.51 respectively. Hindakia sp was able to produce 13.79 mg/ml of EPS which paves way to a hydrated biofilm matrix that aids in better electrogenicity. To the best of our knowledge, EPS production, electrogenic activity and their utility in waste water treatment are reported for the first time in Hindakia sp. The results of our study demonstrated the combined beneficial traits of microalgae towards electricity production and waste water treatment.

Interaction of Midazolam with Glassy Carbon Supported Lipid Membrane in the Presence and Absence of Marker Ions

A biomimetic membrane was formed on the surface of electrochemically activated glassy carbon electrode in NaCl bath solutions. The variation of electrochemical properties of solid supported bilayer lipid membrane (s-BLM) with NaCl concentration in the bath solutions in the presence and absence of ferri/ferrocyanide marker ions was discussed using electrochemical impedance spectroscopy. The extent of pore formation on the s-BLM surface was discussed using bode phase diagram. The electrochemical impedance studies show that the partition of midazolam into the s-BLM strongly depends on Cl– ion concentration in the bath solutions. The variation of membrane capacitance with drug dose shows the ionized form of midazolam interaction with the surface of s-BLM while the neutral and ion pair forms get partitioned into the membrane. In the presence of marker ions, the membrane resistance increases with decrease in NaCl concentration in the bath solution. The cyclic voltammetric responses of marker ions for bare and drug doped s-BLMs in NaCl bath solutions were recorded and variation of redox peak currents with drug dose was discussed.

Recent Advantages and Applications of Various Biosynthesized Greener Silver Nanoparticles

Green synthesis is an effective method for the synthesis of metal and metal oxide nanoparticles. The strong affinity nature of phytochemicals has been effectively utilized as a source of non-toxic nanoparticle production. The optimized pH, concentration, temperature, reaction time needed for non-aggregated and stable biosynthesis silver nanoparticles. The surface modifications of silver nanoparticles over the functionalization of natural compounds are generated unbelievable new thoughts on its properties. Biomolecules in plant extract redirect different safe and size on designed material, which cater as key instruments for harvesting the UV-region. The bio-interaction of structural integrity silver nanomaterial’s are promoted the reactive oxygen species in the wound, redox peak potential on cyclic voltammetry, spectral alteration at surface plasmon resonance (SPR) effect and redox reaction on the degradation of organic dyes. In this review, the utilization of different biological compounds and their role of mechanism in the evergreen latest application of colorimetric sensing, electrochemical analysis, wound healing and catalyst areas is discussed.

Key activity descriptors of nickel-iron oxygen evolution electrocatalysts in the presence of alkali metal cations

Efficient oxygen evolution reaction (OER) electrocatalysts are pivotal for sustainable fuel production, where the Ni-Fe oxyhydroxide (OOH) is among the most active catalysts for alkaline OER. Electrolyte alkali metal cations have been shown to modify the activity and reaction intermediates, however, the exact mechanism is at question due to unexplained deviations from the cation size trend. Our X-ray absorption spectroelectrochemical results show that bigger cations shift the Ni2+/(3+δ)+ redox peak and OER activity to lower potentials (however, with typical discrepancies), following the order CsOH > NaOH ≈ KOH > RbOH > LiOH. Here, we find that the OER activity follows the variations in electrolyte pH rather than a specific cation, which accounts for differences both in basicity of the alkali hydroxides and other contributing anomalies. Our density functional theory-derived reactivity descriptors confirm that cations impose negligible effect on the Lewis acidity of Ni, Fe, and O lattice sites, thus strengthening the conclusions of an indirect pH effect.

Electrochemical Response of Clay/Polyelectrolyte Composite Barrier Coatings

Composite materials made of polymer and clay are effective at blocking mass transport. In this study, the blocking efficacy of layer-by-layer (LbL) coatings of exfoliated montmorillonite (MMT) and polyethylenimine (PEI) was studied using cyclic voltammetry and a redox couple, indigo carmine (IC). The pH of the MMT solution was varied from 4 to 10 to prepare LbL coatings of different surface roughness on metal substrates. It was found that the coated electrode had a lower redox peak current value than without the coating, demonstrating the reduction of the mass transport of IC to the metal surface. The peak values decreased with decreasing the coating’s roughness and increasing the number of layers, indicating that the blocking capability can be controlled by changing the deposition conditions. Smooth LbL coatings deposited with MMT at pH 4 showed the highest blocking efficacy up to 97.5%. The IC adsorbed at the interface between the coating and the metal substrate was found to cause the peak current measured for the coated electrode. It was also confirmed that the same coating on the copper substrate reduced the corrosion of the copper during the electrochemical potential cycling.

Effect of the pyrolysis temperature after hydrothermal reaction on the structure of electrode material LiFexCo1􀀀xPO4 (0.1 x 0.5) and electrochemical evaluation of this material in Li-ion half-cell

High voltage cathode LiCoPO4 has been taken great interest for high power Li-ion batteries (LIBs). Though Co enhance the cyclability, capacity of materials, Co concentration should be reduced in electrode materials due to its high cost and toxic. In this work, the solvo-thermal reaction following by pyrolysis in inert Ar was investigated to synthesize the electrode materials LiFexCo1-xPO4 (0.1 <= x <= 0.5) for LIBs. The structure of the materials after calcinated at 600 oC, 700 oC and 800 oC was analyzed by X-ray diffraction (XRD). The results indicated that the olivine structure was obtained for all Fe contents, except for x = 0.5. At the content of 0.1 and 0.5, the intensity of impurity peaks in the samples increased with the pyrolysis temperature. Meanwhile, other samples did not display the obvious change of olivine structure. Electrochemical properties of the materials were evaluated via cyclic voltammetry (CV) and Galvanostatic charging-discharging. CV curves of the samples with Fe content of 0.2x0.4 all displayed high intensity and reversible redox peak of Co3+/Co2+ locating at 4.8 V and another peak of Fe3+/Fe2+ locating at 3.5 V. As the Fe content increased, the former peaks decreased while the latter increased due to the change of active species concentrations. Unfortunately, the specific capacities obtained for Fe-substituted materials were lower than the pristine material (70 mAh/g versus 120 mAh/g) and gradually declined during cycling. The results could be due to the electrolyte decomposition in the first charging. However, the sample with x = 0.1 exhibited the best performance with discharge capacity of 70 mAh/g and 73% capacity retention obtained after 25 cycles, which was better than the sample with x = 0.2 and unsubstituted sample.

Noninvasive wearable electroactive pharmaceutical monitoring for personalized therapeutics

To achieve the mission of personalized medicine, centering on delivering the right drug to the right patient at the right dose, therapeutic drug monitoring solutions are necessary. In that regard, wearable biosensing technologies, capable of tracking drug pharmacokinetics in noninvasively retrievable biofluids (e.g., sweat), play a critical role, because they can be deployed at a large scale to monitor the individuals’ drug transcourse profiles (semi)continuously and longitudinally. To this end, voltammetry-based sensing modalities are suitable, as in principle they can detect and quantify electroactive drugs on the basis of the target’s redox signature. However, the target’s redox signature in complex biofluid matrices can be confounded by the immediate biofouling effects and distorted/buried by the interfering voltammetric responses of endogenous electroactive species. Here, we devise a wearable voltammetric sensor development strategy—centering on engineering the molecule–surface interactions—to simultaneously mitigate biofouling and create an “undistorted potential window” within which the target drug’s voltammetric response is dominant and interference is eliminated. To inform its clinical utility, our strategy was adopted to track the temporal profile of circulating acetaminophen (a widely used analgesic and antipyretic) in saliva and sweat, using a surface-modified boron-doped diamond sensing interface (cross-validated with laboratory-based assays,R2∼ 0.94). Through integration of the engineered sensing interface within a custom-developed smartwatch, and augmentation with a dedicated analytical framework (for redox peak extraction), we realized a wearable solution to seamlessly render drug readouts with minute-level temporal resolution. Leveraging this solution, we demonstrated the pharmacokinetic correlation and significance of sweat readings.

The Effect of Al2O3 Doped and Carbon Coated Li4Ti5O12 on Structures, Morphology and Electrochemical Performance

In this research, Li4Ti5O12 anode with doping Al2O3 and carbon coating was made to determine the effect of doping Al2O3 and carbon coating on crystal structure, morphology and electrochemical performance. Li4Ti5O12 anode material consisting of LiOH.H2O and TiO2 was made with various samples of LTO without doping, LTO doped carbon, LTO doping Al2O3 and carbon using the solid state reaction method. All raw materials are mixed and milled using a Planetary Ball Miller for 2 hours then crushed to become a precursor to Li4Ti5O12. The Li4Ti5O12 precursor was sintered at 850°C for 4 hours. The final product was characterized using X-Ray Diffraction (XRD) to determine the formation of Li4Ti5O12 phases, Scanning Electron Microscopy (SEM) to analyze the morphology formed, and Cyclic Voltammetry to determine electrochemical performance. The results of XRD characterization were formed in the Lithium Titanium Oxide (Li4Ti5O12), Dilithium Titanate (Li2TiO3), and Rutile (TiO2) phases. The SEM characterization results on LTO doping carbon, LTO doping Al2O3 and carbon showed a coarser texture compared to the LTO without doping which had a fine texture. The electrochemical performance produced in LTO coating carbon has a slender redox peak in the first cycle, this shows that LTO coating carbon has good electrochemical performance compared to the Al2O3 and carbon doping LTO samples.