An investigation on the tuning effect of glucose-capping on the size and bandgap of CuO nanoparticles

• Glucose capped CuO nanoparticles were synthesized via the versatile sol–gel route.
• The crystallite and particle sizes decline with increasing glucose concentration.
• The absorption edge blue shifts with decrease in size of the nanoparticles.
• Effective bandgap tuning was achieved with controlled capping of CuO nanoparticles.

We report herein the synthesis of CuO nanoparticles with varying concentrations of the organic modifier glucose as capping agent by the facile and versatile sol–gel route. The microstructure, surface morphology with composition, optical and transport properties of the nanoparticles thus produced were analyzed using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Electron Diffraction X-ray Analysis (EDAX), Fourier Transform Infrared Spectroscopy (FTIR), UV–Visible Spectroscopy (UV–Vis) and photoconductivity techniques. XRD analysis showed that the crystallite size of the nanoparticles as calculated by the Scherrer’s formula tends to decrease with increase in the molar concentration of capping agent. SEM results revealed that with increase in the molar concentration of the capping agent CuO nanopowder tends to become more homogeneous and thus well prevented the agglomeration of the nanoparticles. Also the particle size was observed to decline with increasing capping agent concentration. Band gap calculations made employing the Tauc’s plot method indicate a consistent increase in the band gap with increase in concentration of capping agent corresponding to the reduction in particle size. The impact of the capping agent on the vibration pattern of CuO nanoparticles is evident from the FTIR spectra. The photoconductivity of the CuO nanoparticles showed a decrease in the dark and photo current values with the increase in molar concentration of the capping agent which could be attributed to the increase in the optical band gap. Thus the particle size and hence the band gap of nanoparticles could be tuned effectively by altering the concentration of the capping agent.

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