ZnO nanoparticles have been synthesized by using biodegradable natural biopolymer viz. Gum Tragacanth. This single step approach is very cost effective and reproducible. The reaction time and concentration of precursor zinc acetate play a major role in the nature and growth of ZnO nanoparticles. ZnO nanoparticles were characterized by X-ray diffraction, SEM, FTIR, EDAX, UV-visible spectroscopy and TEM. ZnO nanoparticles with 20-30 nm in diameter and hexagonal morphology were found; dispersed uniformly. Raman spectrum shows the mode E₂ high at 437 cm⁻¹ that is related to the vibration of wurtzite Zn-O bond in crystal structure of ZnO. The space between adjacent lattice fringes is ∼ sharp 2.42 Å. UV-visible absorption spectrum shows the sharp absorption band at 308 nm assigned to the intrinsic transition from valance band to conduction band. The ZnO nanoparticles display superior catalytic activity of conversion of aldehyde to acid as compared to bulk-ZnO material, because of high surface area of ZnO nanoparticles. A trace amount of ZnO nanoparticles catalyst required for organic conversion. The ZnO nanoparticles as catalyst are highly stable, recyclable and efficient in its activity.

A Polyindole-ZnO nanocomposite particle was synthesized by using a chemical oxidative polymerization method. Synthesized nanocomposite was characterized by UV-Visible, FTIR, SEM, XRD, EDAX and electrical conductivity measurements. The band at ∼3400 cm⁻¹ and 735 cm⁻¹ in FTIR spectra confirmed the polyindole formation. XRD spectral studies exhibits major diffraction in between 30–40° (2θ) indicates the partial crystalline nature of the polyindole-ZnO nanocomposite. SEM image reveals agglomerated granular particulate nature with ZnO embedded in the polyindole matrix. The application of Polyindole-ZnO nanocomposite as a polymer-supported catalyst was studied for the synthesis of one pot multicomponent Biginelli condensation.

Herein, we have developed a novel heterogeneous catalytic system for synthesis of bis(indol-3-yl)methanes using one dimensional (1D) CdS nanorods. CdS nanorods were synthesized by a solvothermal reaction technique at 200 °C over 12 h in the presence of ethylenediamine as a solvent. The prepared 1D CdS was characterized using various spectroscopic methods. X-ray diffraction (XRD) revealed the formation of highly crystalline CdS having a wurtzite structure. FESEM analysis confirms the formation of a rod like morphology with length around 150 to 200 nm and diameter ∼15 nm. TEM also validates the formation of uniform size one dimensional (1D) CdS nanostructures. The catalytic activity of 1D CdS as a Lewis acid was investigated for the synthesis of bis(indol-3-yl)methanes (BIMs) with various substituted aldehydes and indoles within shorter reaction time affording the corresponding product in excellent yield.