Controlled assembly of mesoscopic structures can bring interesting phenomena because of their interfaces. Here, carbon nanotubes (CNTs) are cross-coupled via a C–C bonding through Suzuki reaction resulting in three-dimensional (3D) CNT sponges, and these 3D CNTs are studied for their efficacy toward the electrocatalytic hydrogen evolution reaction (HER) in acidic mediumone of the promising methods for the production of a renewable energy source, hydrogen. Both single and multiwall CNTs (SWCNTs and MWCNTs) are studied for the development of 3DSWCNTs and 3DMWCNTs, and these 3D CNTs are found to be HER active with small reaction onset potentials and low charge-transfer resistances unlike their uncoupled counterparts. First-principle density functional calculations show that the combination of electron acceptor and donor bonded to the CNT network can provide a unique band structure modulation in the system facilitating the HER reaction. This study can provide possibilities for band engineering of CNTs via functionalization and cross-coupling reactions.

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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.

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.

Molecularly imprinted polymer (MIP) for sulfanilamide (SN) sensing is prepared through in‐situ electropolymerization of pyrrole (Py) on pencil graphite electrode (PGE). Computational study using density functional theory with B3LYP level is performed to analyze and evaluate the template‐monomer geometry. Among the various functional monomers studied pyrrole is found to have the highest binding interaction energy with SN and it is chosen as a functional monomer. Electropolymerization of pyrrole in the presence of SN on PGE is carried out using cyclic voltammetry. Structural morphology of the imprinted polymer is characterized by field emission scanning electron microscopy (FESEM) studies. Quantitative measurements of MIP based SN detection are performed by using cyclic voltammetry and differential pulse voltammetry studies. Several important kinetic parameters influencing the performance of SN sensor such as limit of detection, linear concentration range and sensitivity etc. are determined and analyzed. Under the optimized conditions, MIP based SN sensor proposed in this work has a very low detection limit of 2.0×10−8 M (S/N=3) and possesses two linear ranges from 5.0×10−8 to 1.1×10−6 M and 1.1×10−6 to 48×10−6 M with a sensitivity value of 1.158 and 0.012 µA/µM respectively. This particular sensor shows a good selectivity towards SN in presence of potential other structural analogue interferences namely sulfamethaxazole, sulfathiazole and sulfadiazine. Furthermore, the fabricated sensor is successfully applied to quantitatively determine and analyze SN present in spiked human serum and ground water samples.

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A novel route for the development of luminescent quantum dots of layered crystals is demonstrated.

Molecularly imprinted polymer (MIP) for uric acid (UA) was synthesized by thermal polymerization using acrylic acid (AA) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross linker and 2,2′‐azobis(2‐isobutyro) nitrile (AIBN) as initiator. The noncovalent interactions involved in four possible conformations of pre‐polymer complex were computationally studied by density functional theory. The hydrogen bond formation between UA and AA was confirmed by Fourier transform infrared (FTIR) spectrum of the MIP before extraction of UA. After extraction of the template, the molecularly imprinted polymer based carbon paste electrode (MIPCPE) was fabricated under optimized conditions. A significant enhancement in the electrocatalytic oxidation of UA was found at MIPCPE. The electrochemical behavior of sensor was investigated by cyclic voltammetry (CV) and differential pulse adsorptive stripping voltammetry (DPAdSV). The electrochemical impedance spectroscopy (EIS) studies revealed less charge transfer resistance (Rct) at MIPCPE than NIPCPE. Under optimized conditions, calibration curve was obtained with a linearity range of 0.5 µM to 100 µM and the limit of detection was 0.1 µM. The sensor showed good selectivity towards UA in the presence of interferents and was successfully applied for the determination of UA in spiked serum samples.