Graphene Oxide–Phosphor Hybrid Nanoscrolls with High Luminescent Quantum Yield: Synthesis, Structural, and X-ray Absorption Studies

Abstract

Highly luminescent graphene oxide (GO)-phosphor hybrid thin films with a maximum quantum yield of 9.6% were synthesized via a simple chemical method. An intense luminescence emission peak at 537 nm and a broad emission peak at 400 nm were observed from the GO-phosphor hybrid films. The maximum quantum yield of the emissions from the hybrid films was found to be 9.6%, which is 48 times higher than that of pristine GO films. The GO-phosphor hybrids were prepared via spin-coating and subsequent postannealing of the films, resulting in scrolling of the GO sheets. The resulting GO nanoscrolls exhibited a length of ∼2 μm with nanoscale interior cavities. Transmission electron microscopy and selected-area electron diffraction analyses revealed that the lattice structure of the tubular scrolls is similar to that of carbon nanotubes. While pristine GO films are p-type, in the GO-phosphor hybrids, the Fermi level shifted upward and fell between the HOMO-LUMO gap due to phosphor attachment via C-N bonding. The highly luminescent GO-phosphor hybrids will find important applications in graphene-based optoelectronic devices.

Graphene Oxide Inserted Poly(N‐Vinylcarbazole)/Vanadium Oxide Hole Transport Heterojunctions for High‐Efficiency Quantum‐Dot Light‐Emitting Diodes

“…First, the intensity ratio of D and G bands ( I D / I G ) was increased from 0.85 to 1.0 when (ii) non‐ANN‐GO was annealed to be (iii) ANN‐GO . Second, the Raman shift of G band of (ii) non‐ANN‐GO at 1597 cm −1 was redshifted to 1586 cm −1 by forming (iii) ANN‐GO, while a negligible shift was observed in D‐band (Figure S10, Supporting Information) . These Raman spectroscopic results imply that the reduction of GO was occurred while the VOC was formed by the annealing process.…”

“…The Φ of (iii) ANN‐GO on V 2 O 5– x /ITO (= 4.97 eV) was measured to be smaller than that of (ii) non‐ANN‐GO on ITO (= 5.3 eV) (Figure a); from the UPS onsets in Figure b, the VBM of (ii) non‐ANN‐GO and (iii) ANN‐GO was measured to be −1.10 and −0.65 eV, respectively . More importantly, the bandgap of GO was found to be reduced from 1.94 to 1.40 eV from ultraviolet–visible absorption spectroscopic analysis (see Figure S12, Supporting Information), suggesting that (iii) ANN‐GO is a partially reduced GO . This result also corroborates the reduction of GO in the ANN‐GO/V 2 O 5– x heterojunction during the annealing process, similar to other literatures.…”

Reduced graphene oxide enwrapped phosphors for long-term thermally stable phosphor converted white light emitting diodes

“…These rod structures are nothing but rGO sheets that are transformed in to nanoscrolls. This scrolling is a result of the interaction of heavy phosphor particles with rGO sheet during annealing which results in an extremely unfavorable condition for rGO to maintain its planar structure1718. During the annealing of the GO-phosphor composite at high temperatures, along with the removal of functional groups, the phosphor particles are also attached to the rGO sheets.…”

“…This is because, the interaction between phosphor particles and rGO renders the planar structure of the rGO sheets extremely unfavorable19. The bending of the rGO sheets is followed by rolling to form scrolls because of Van der Waals attraction and the π-π stacking effect between rGO layers1718. The formation of the nanoscrolls occurs in two steps.…”

Raman Spectra of Luminescent Graphene Oxide (GO)-Phosphor Hybrid Nanoscrolls

“…We report highly luminescent GO-phosphor nanoscrolls which have the advantage of both GO and a luminescent phosphor material [13]. The structural and optical characteristics of the hybrids are analyzed in detail.…”