Xiaoguang Liu

Graphene quantum dots modified ZnO + Cu heterostructure photocatalysts with enhanced photocatalytic performance

ZnO represents a typical class of semiconductor oxide with unique photocatalytic activity. However, its photocatalytic activity under continuous ultraviolet (UV) light irradiation is greatly limited by fast carrier recombination and photocorrosion behavior. Two of the most effective methods to solve the challenges are blending with electron acceptor materials and surface modification. Here, a novel heterostructure photocatalyst of a graphene quantum dot (GQD) surface modified ZnO + Cu composite was prepared via a simple spin-coating and annealing process. This photocatalyst exhibits significant improvements in UV-light irradiated photodegradation of rhodamine B (RhB) compared to ZnO. The improved photocatalytic ability could be attributed to the synergistic effects of Cu nanoparticles (NPs) and GQDs, which play an important role in light absorption, charge separation and transfer, and photocorrosion. Meanwhile, the enhanced degree is related to the amount of surface modified GQDs.

3D nano-arrays of silver nanoparticles and graphene quantum dots with excellent surface-enhanced Raman scattering

ABSTRACT Active surface-enhanced Raman scattering (SERS) substrates, 3D nano-arrays of Ag nanoparticles (NPs) and graphene quantum dots (GQDs), were prepared using a photochemical approach and an electrophoresis deposition technique with the formation mechanism addressed. The GQDs (ca. 6u2009nm average) fit into the inter-particle gaps between Ag NPs, as verified by their scanning electron microscopy and high-resolution transmission electron microscopy. This deliberately designed 3D assembly of Ag NPs and GQDs could promote the synergistic effects of both components to further enhance the SERS performances according to both electromagnetic mechanism and chemical mechanism. Preliminary experiments show that the 3D substrates exhibited strong SERS signals comparing with bare Si substrates. This work provides a promising way for 3D SERS substrates.

Shear-thickening behavior of Fe-ZSM5 zeolite slurry and its removal with alumina/boehmites

A cryogenic scanning electron microscopy (cryo-SEM) technique was used to explore the shear-thickening behavior of Fe-ZSM5 zeolite pastes and to discover its underlying mechanism. Bare Fe-ZSM5 zeolite samples were found to contain agglomerations, which may break the flow of the pastes and cause shear-thickening behaviors. However, the shear-thickening behaviors can be eliminated by the addition of halloysite and various boehmites because of improved particle packing. Furthermore, compared with pure Fe-ZSM5 zeolite samples and its composite samples with halloysite, the samples with boehmite (Pural SB or Disperal) additions exhibited network structures in their cryo-SEM images; these structures could facilitate the storage and release of flow water, smooth paste flow, and avoid shear-thickening. By contrast, another boehmite (Versal 250) formed agglomerations rather than network structures after being added to the Fe-ZSM5 zeolite paste and resulted in shear-thickening behavior. Consequently, the results suggest that these network structures play key roles in eliminating the shear-thickening behavior.