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This paper reports on the synthesis and use of graphene oxide/ZnO nanocomposite as a heterogeneous catalyst for the synthesis of various tetrazoles. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and UV-vis spectroscopy. This method has the advantages of high yields, elimination of homogeneous catalysts or corrosive acids, simple methodology and easy work up. Another important factor is the stability and recyclability of the catalyst under the reaction conditions used. This heterogeneous catalyst shows no significant loss of activity in the recycling experiments.

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Determination of the spectral profile of light signals is an effective way to characterize the structure and dynamics of materials, and also light sources. In this work, we introduce a simple, fast, and cost effective line fitting technique, in which Fresnel diffraction from a phase step is used to determine the central wavelength and linewidth of the spectra of light sources. In principle, a single diffraction pattern suffice to determine the line profile. As proof-of-principle examples, two light emitting diode sources have been investigated using phase steps with different heights. Reproducible results are obtained with relative uncertainties in the order of 10−2 for both the central wavelength and linewidth. Comparison with conventional spectroscopy measurements are also provided.

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