The preparation of urea (bonded) cross-linked multilayer thin films by sequential deposition of bifunctional and tetrafunctional molecular building blocks is demonstrated. Multilayer growth as a function of deposition cycles was inspected using UV-vis absorption spectroscopy. From infrared results, three characteristic infrared bands of amide I, amide II, and asymmetric νa(N-C-N) stretching confirmed the formation of polyurea networks by alternate dipping into solutions of amine and isocyanate functionality monomers. The deconvoluted component of the C 1s and N 1s spectra obtained by X-ray photoelectron spectroscopy shows clear evidence of stable polyurea networks. The enhancement of structural periodicity with film growth was demonstrated by grazing-incidence small-angle X-ray scattering measurements. The thin film near the substrate surface seems to have an amorphous structure. However, molecular ordering improves in the surface normal direction of the substrate with a certain number of deposited layers. Constant mass density was not observed with deposition cycles. The mass density increased up to 16% within deposited layers from proximate layers to those extending away from the substrate surface. This difference in the packing density might derive from the different degrees of cross-linking among layers proximate to the substrate surface and extending away from the substrate surface.

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Carbon nanomaterial coupled with inorganic semiconductor based metal oxide is a facile route to develop effective electrochemical sensors. Herein, an electrochemical investigation was carried out for selective and sensitive detection of hydrogen peroxide (H2O2) using 5% mesoporous carbon doped ZnO (Meso-C/ZnO) nanocomposite modified glassy carbon electrode (GCE). The ZnO nanomaterial was synthesized by a F127 structural template agent in a modified sol-gel procedure. Then, a simple ultra-sonication technique was employed to synthesize Meso-C/ZnO nanocomposite. XRD, TEM, FTIR, Raman, and XPS techniques were successfully applied to characterize the as-fabricated nanocomposite. CV and EIS measurements were used to evaluate the electrocatalytic activity of the modified electrode compared to pure ZnO modified GCE and unmodified GCE. The sensing efficiency of the active modified electrode was examined with square wave voltammetry (SWV) technique and the sensor exhibits excellent performance towards the detection of H2O2 in a wide linear concentration range (from 50 μM to 981 μM), with high sensitivity (0.04648 μMμA−1 cm−2), and low limit of detection (6.25 μM). Additionally, the selectivity test using several common interfering species demonstrated excellent anti-interfering ability. Furthermore, the fabricated electrode showed excellent reproducibility and operational stability as well as suitability for the real sample analysis. Thus, this new sensor is considered as very auspicious candidate in several fields of science and industry.

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