Cr-doped ZnGa2O4: Simple synthesis of intense red-NIR emitting nanoparticles with enhanced quantum efficiency

Sridhar G., Deepak Hebbar N., Samvit G. Menon, Prinston Melroy Lewis, K. S. Choudhari, Robin E. Kroon, Hendrik C. Swart, Suresh D. Kulkarni

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3 Citations (Scopus)


Red-NIR emitting ZnGa2-xCrxO4 nanoparticles were synthesized using simple co-precipitation, and the effect of annealing was studied (600–1200 °C). Upon annealing, crystallite size increased (12 nm–73 nm), and color tone turned pink beyond 1000 °C, inferring dopant diffusion. Blue, green absorption bands in diffuse-reflectance spectra revealed Cr3+ in octahedral crystal field. Photoluminescence excitation spectra showed characteristic Cr3+ bands (∼400 nm and ∼550 nm), and the asymmetric 400 nm band suggested splitting the 4T1g(F) state due to trigonal distortion. Emission spectra consisted of a zero-phonon line (∼688 nm), along with associated multi-phonon sidebands. ZnGa1.98Cr0.02O4 showed intense red emission with λexc = 420 nm, while the tri-exponential fitting of the excited-state lifetime implied multiple decay processes due to Cr3+ occupying different environments. The internal quantum efficiency of the 1200 °C annealed sample was impressive (48%). Both UV and visible light up to 600 nm could induce persistent-luminescence (λem = 688 nm) for longer durations. The smaller size, intense emission, higher quantum yield, and visible light activation suggest that the nanoparticles are suitable for bioimaging applications.

Original languageEnglish
Article number111919
JournalOptical Materials
Publication statusPublished - 01-2022

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Spectroscopy
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry
  • Electrical and Electronic Engineering


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