Herein, the efficient serotonin (5-HT) sensing studies have been conducted using the (ZnO NRs)1−x(CNs)x nanocomposites (NCs) having appropriate structural and electrochemical properties. Initially, the different compositions of ZnO nanorods (NRs), with varying content of carbon nanostructures (CNs=MWCNTs and RGO), are prepared using simple in-situ wet chemical method and thereafter these NCs have been characterized for physico-chemical properties in correlation to the 5-HT sensing activity. XRD Rietveld refinement studies reveal the hexagonal Wurtzite ZnO NRs oriented in (101) direction with space group ‘P63mc’ and both orientation as well as phase of ZnO NRs are also retained in the NCs due to the small content of CNs. The interconnectivity between the ZnO NRs with CNs through different functional moieties is also studied using FTIR analysis; while phases of the constituents are confirmed through Raman analysis. FESEM images of the bare/NCs show hexagonal shaped rods with higher aspect ratio (4.87) to that of others. BET analysis and EIS measurements reveal the higher surface area (97.895 m2/g), lower charge transfer resistance (16.2 kΩ) for the ZCNT 0.1 NCs to that of other NCs or bare material. Thereafter, the prepared NCs are deposited on the screen printed carbon electrode (SPCE) using chitosan as cross-linked agent for 5-HT sensing studies; conducted through cyclic voltammetry (CV) and square wave voltammetry (SWV) measurements. Among the various composites, ZCNT0.1 NCs based electrodes exhibit higher sensing activity towards 5-HT in accordance to its higher surface area, lower particle size and lower charge transfer resistance. SWV measurements provide a wide linear response range (7.5–300 μM); lower limit of detection (0.66 μM), excellent limit of quantification (2.19 μM) and good reproducibility to ZCNT 0.1 NCs as compared to others for 5-HT sensing studies.
We have synthesized amino functionalized reduced graphene oxide (NH 2 -rGO) composite. Bucherer reaction was used for the in situ modification of graphene oxide into the (NH 2 -rGO). A simple hydrothermal method was utilized for proposed synthesis. Electrochemical sensor was fabricated by drop coating NH 2 -rGO nanocomposite onto the glassy carbon electrode (GCE) for individual and the simultaneous detection of dopamine (DA) and uric acid (UA). The NH 2 -rGO materials formation was confirmed by X-ray diffraction, IR, UV and FE-SEM. The electrochemical sensing of DA and UA was examined by cyclic voltammetry and differential pulse voltammetry. For individual detection of DA, the linear responses of current concentration plot was found in the concentration range of 2.04 × 10 −4 -2.04 × 10 −3 M with detection limit 1.4 × 10 −4 M (S/N = 3) and for UA, 1.8 × 10 −3 -1.8 × 10 −4 M with detection limit 1.67 × 10 −4 M (S/N = 3). The NH 2 -rGO/GCE electrochemical sensor further tested for the simultaneous detection of binary mixtures of DA and UA and found to be high sensitive compared to individual detection of DA and UA at pH 3. Sensor selectivity is demonstrated in the presence of 2 × 10 −4 M concentrations of potentially active interfering compounds including dopamine, uric acid and glucose isomers.
Nickel (Ni2+) ion doped zinc oxide-multi-wall carbon nanotubes (NZC) with different composition ratios of MWCNTs (from 0.01 to 0.1 wt%) are synthesized through an in situ sol–gel method.
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