Cobalt molybdate nanoflowers decorated bio-waste derived porous activated carbon nanocomposite: A high performance electrode material for supercapacitors.

In this work, we report a supercapacitor electrode material based on nano-flower like cobalt molybdate decorated on porous activated carbon derived from waste onion peels (ß-CoMoO4-POAC). The obtained POAC exhibits highly porous structure and after the hydrothermal treatment with salts of cobalt and molybdenum, we observed a uniform distribution of ß-cobalt molybdate (ß-CoMoO4) as nano-flowers on the surface of POAC. The chemical composition, morphology and porosity of the materials were thoroughly analyzed using field emission scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, infrared spectroscopy and Brunauer-Emmet-Teller surface area measurement. Due to its flower like and highly porous morphology, ß-CoMoO4@POAC exhibits a high specific capacitance of 1110.72 F/g at a current density of 1 mA/cm2 with superior cyclic retention of 96.03% after 2000 cycles. The best electrochemical performance exhibited by ß-CoMoO4@POAC is mainly due to its high surface area and porous nature of the material which assists in active transport of ions. This study reveals the exceptional electrochemical properties of ß-CoMoO4@POAC which could be considered as a potential material for advanced energy storage devices.

A zinc selective oxytocin based biosensor.

Oxytocin is a peptide hormone with high affinity to both Zn2+ and Cu2+ ions compared to other metal ions. This affinity makes oxytocin an attractive recognition layer for monitoring the levels of these essential ions in biofluids. Native oxytocin cannot differentiate between Cu2+ and Zn2+ ions and hence it is not useful for sensing Zn2+ in the presence of Cu2+. We elucidated the effect of the terminal amine group of oxytocin on the affinity toward Cu2+ using theoretical calculations. We designed a new Zn2+ selective oxytocin-based biosensor that utilizes the terminal amine for surface anchoring, also preventing the response to Cu2+. The biosensor shows exceptional selectivity and very high sensitivity to Zn2+ in impedimetric biosensing. This study shows for the first time an oxytocin derived sensor that can be used directly for sensing Zn2+ in the presence of Cu2+.

Sulfur extraction from liquid fuels using trihexyl(tetradecyl)phosphonium tetrafluoroborate: as promising solvent.

Sulfur extraction from fuel is essential to be done for environmental and industrial point of view. Extractive desulfurization (EDS) is one of the most promising techniques in order to achieve legislative sulfur content requirements. Among numerous extractants and solvents, ionic liquids (ILs) are more capable due to their desirable green solvent properties. This work demonstrated that trihexyl(tetradecyl)phosphonium tetrafluoroborate ([THTDP]BF4) was synthesized, characterized, and employed as extraction solvent for extraction of dibenzothiophene (DBT), thiophene, benzothiophene, and other alkyl-substituted derivatives of sulfur from liquid fuel. Molecular confirmation and purity of synthesized ([THTDP]BF4) were analyzed with FTIR, Raman, NMR, EPR, UV, TG/DSC, and XRD analyses. Also, physical properties of ([THTDP]BF4) were carried out. The effects of extraction time, temperature, sulfur compounds, ultra-sonication, and ([THTDP]BF4) recycling/regeneration on DBT removal from liquid fuel were also examined. DBT removal in n-dodecane was 92.6% using EDS with mass ratio (1:1) in 30 min at 30 °C under the mild reaction conditions. ([THTDP]BF4) could be reused up to ten cycles for sulfur extraction and regenerated for few more cycles with good DBT removal ability. Also, the sulfur extraction from real fuels and multistage extraction performance were tested. The experimental data and results provided in this article discover the remarkable understandings of tetrafluoroborate-based phosphonium ionic liquids as promising solvent for EDS.

Neurotransmitter Dopamine Enhanced Sensing Detection Using Fibre-Like Carbon Nanotubes by Chemical Vapor Deposition Technique.

Carbon nanotubes (CNTs) are still receiving much attention in bio-sensing applications due to their remarkable properties. In this present research work, fibre-like carbon nanotubes (f-CNTs) were successfully fabricated over copper-molybdenum (Cu-Mo) substituted alumina nanoparticles at atmospheric pressure by chemical vapor deposition (CVD) technique and effectively employed as a neurotransmitter dopamine (DA) sensor. The obtained product was purified and structurally characterized by various techniques such as, field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, high resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectroscopy (XPS) analysis. Structural characterization, which reveals the material contains fibre-like multi walled carbon nanotubes with graphene layers having diameter in the range of 10-20 nm and 200-300 nm inner and outer, respectively and has certain crystallinity. The weight percentages of Cu, Mo in Alumina catalyst, reaction temperature, acetylene flow rate and reaction time have been optimised to yield maximum of carbon product. Electrochemical properties of the material towards DA sensing were studied by cyclic voltammetry (CV), and diffuse pulse voltammetry (DPV) techniques. The sensor exhibits linear relationship among the peak current and DA concentration from 8 to 45 µM with detection limit of 5.3 µM (S/N = 3). The presence of structural analogues of DA has no deleterious effect on the DA anodic peak current.

Oxytocin-Monolayer-Based Impedimetric Biosensor for Zinc and Copper Ions.

Zinc and copper are essential metal ions for numerous biological processes. Their levels are tightly maintained in all body organs. Impairment of the Zn2+ to Cu2+ ratio in serum was found to correlate with many disease states, including immunological and inflammatory disorders. Oxytocin (OT) is a neuropeptide, and its activity is modulated by zinc and copper ion binding. Harnessing the intrinsic properties of OT is one of the attractive ways to develop valuable metal ion sensors. Here, we report for the first time an OT-based metal ion sensor prepared by immobilizing the neuropeptide onto a glassy carbon electrode. The developed impedimetric biosensor was ultrasensitive to Zn2+ and Cu2+ ions at physiological pH and not to other biologically relevant ions. Interestingly, the electrochemical impedance signal of two hemicircle systems was recorded after the attachment of OT to the surface. These two semicircles suggest two capacitive regions that result from two different domains in the OT monolayer. Moreover, the change in the charge-transfer resistance of either Zn2+ or Cu2+ was not similar in response to binding. This suggests that the metal-dependent conformational changes of OT can be translated to distinct impedimetric data. Selective masking of Zn2+ and Cu2+ was used to allow for the simultaneous determination of zinc to copper ions ratio by the OT sensor. The OT sensor was able to distinguish between healthy control and multiple sclerosis patients diluted sera samples by determining the Zn/Cu ratio similar to the state-of-the-art techniques. The OT sensor presented herein is likely to have numerous applications in biomedical research and pave the way to other types of neuropeptide-derived sensors.

On the development of multifunctional luminescent supramolecular hydrogel of gold and egg white.

Highly stable, luminescent, and printable/paintable supramolecular egg white hydrogel-based surface enhanced Raman scattering (SERS) matrix is created by an in situ synthesis of gold clusters inside a luminescent egg white hydrogel (Au-Gel). The synthesis of stable luminescent egg-white-based hydrogel, where the hydrogel can act as a three dimensional (3D) matrix, using a simple cross-linking chemistry, has promising application in the biomedical field including in 3D cell culturing. Furthermore, this functional hydrogel is demonstrated for micromolar-level detection of Rhodamine 6G using the SERS technique, where Au-Gel is painted over a flexible cellulose pad.

Fluorographene based Ultrasensitive Ammonia Sensor.

Single molecule detection using graphene can be brought by tuning the interactions via specific dopants. Electrostatic interaction between the most electronegative element fluorine (F) and hydrogen (H) is one of the strong interactions in hydrogen bonding, and here we report the selective binding of ammonia/ammonium with F in fluorographene (FG) resulting to a change in the impedance of the system. Very low limit of detection value of ~0.44 pM with linearity over wide range of concentrations (1 pM-0.1 µM) is achieved using the FG based impedance sensor, andthisscreen printed FG sensor works in both ionized (ammonium) and un-ionized ammonia sensing platforms. The interaction energies of FG and NH3/NH4(+) are evaluated using density functional theory calculations and the interactions are mapped. Here FGs with two different amounts of fluorinecontents -~5 atomic% (C39H16F2) and ~24 atomic% (C39H16F12) - are theoretically and experimentally studied for selective, high sensitive and ultra-low level detection of ammonia. Fast responding, high sensitive, large area patternable FG based sensor platform demonstrated here can open new avenues for the development of point-of-care devices and clinical sensors.

Single step, bulk synthesis of engineered MoS2 quantum dots for multifunctional electrocatalysis.

Bi- or tri- functional catalysts based on atomic layers are receiving tremendous scientific attention due to their importance in various energy technologies. Recent studies on molybdenum disulphide (MoS2) nanosheets revealed that controlling the edge states and doping/modifying with suitable elements are highly important in tuning the catalytic activities of MoS2. Here we report a bulk, single step method to synthesize metal modified MoS2 quantum dots (QDs). Three elements, namely Fe, Mg and Li, are chosen to study the effects of dopants in the catalytic activities of MoS2. Fe and Mg are found to act like dopants in the MoS2 lattice forming respective doped MoS2 QDs, while Li formed an intercalated MoS2 QD. The efficacy and tunability of these luminescent doped QDs towards various electrocatalytic activities (hydrogen evolution reaction, oxygen evolution reaction and oxygen reduction action) are reported here.

Rational synthesis of pindolol imprinted polymer by non-covalent protocol based on computational approach.

Pindolol (PDL) is a potent and specific adrenoreceptor blocking agent. It is widely used in the treatment of hypertension, cardiac arrhythmia and angina pectoris. Molecularly imprinted polymers (MIPs) are synthetic receptors having potential applications in drug delivery systems and devices such as diagnostic sensors. In the present work, ab initio quantum mechanical simulations and computational screening were used to identify functional monomer having best interactions with PDL. A virtual library of 16 functional monomers was built and the possible minimum energy conformation of the monomers and PDL were calculated using Hartree-Fock (HF) method for the synthesis of PDL imprinted polymer. The interaction energy between functional monomer and the template were corrected by means of basis set superposition error (BSSE) in all pre-polymerization complexes. The hydrogen bonding between PDL and functional monomer was evaluated by changes in bond lengths before and after complex formation. The virtual template-monomer complex with highest interaction energy is more stable during the polymerization and leads to high selectivity and specificity toward the template. The interaction energy of PDL was found to be the highest with itaconic acid followed by 4-vinyl pyridine and least with acrylonitrile. Taking a spectroscopic viewpoint, results obtained from analysis of the harmonic infrared spectrum were examined. Red and blue shifts related to the stretching frequencies of either donors or acceptors of protons were identified and compared experimentally. Stoichiometric mole ratio of template to functional monomer was optimized and confirmed by UV visible spectra titrations. The theoretical results were correlated by evaluation of binding parameters of MIPs. The experimental binding results were in good agreement with theoretical computations.