Yingge Dong

Simultaneous synthesis of luminescent carbon nanoparticles and carbon nanocages by laser ablation of carbon black suspension and their optical limiting properties

Both luminescent carbon nanoparticles (CNPs) and carbon nanocages (CNCs) were simultaneously synthesized using laser ablation of carbon black suspension in poly(ethylene glycol). The formation of luminescent CNPs and CNCs depends on the size of carbon black and the laser power density. The optical limiting (OL) measurements of luminescent CNPs, CNCs and their mixture were performed using the open Z-scan technique at the laser wavelength of 532 nm. The mixture of luminescent CNPs and CNCs shows much stronger OL response than carbon black, luminescent CNPs and CNCs in the PEG500N solution. The luminescent CNPs can help to enhance the OL effects of CNC suspensions.

Carbon-Dot-Loaded Alginate Gels as Recoverable Probes: Fabrication and Mechanism of Fluorescent Detection

We prepare a solid and green film of carbon-dot-loaded alginate gels with a pore structure. Compared to carbon dot suspension, the film exhibits stronger blue light emission. The porous structure of the film enables ion diffusion and contact with the CDs incorporated in the gel network, and thus the photoluminescence (PL) behavior of the film can be influenced by ions. The PL of the film shows a sensitive and selective quenching effect to Cu(2+), and it can be repeatedly used as a fluorescent probe to recognize Cu(2+) with a detection limit of 5 ppm. A band bending mechanism is proposed to understand the effects of surface/interface states and metal ions on the PL behavior of carbon-dot-loaded alginate gels, and it has been supported by our further experimental results. This band bending mechanism provides a clear physical insight into ion detection by PL behavior.

Understanding the effects of the structures on the energy gaps in carbon nanoparticles from laser synthesis

The effects of the structures on the energy gaps in luminescent carbon nanoparticles (CNPs) were investigated. On the one hand, we fabricated CNPs with the different structures and a uniform size and then analyzed their photoluminescence (PL) behaviors. On the other hand, we calculated the dependence of the structures on the energy gaps in CNPs by a simple quantitative model. Both the experimental and calculated results show that the luminescent CNPs contain a mixture of sp2 and sp3 bonding and hence their PL behaviors and energy gaps are determined by the fraction of sp2-hybridized carbon atoms.

One-Step Synthesis of Graphitic Nanoplatelets that are Decorated with Luminescent Carbon Nanoparticles as New Optical-Limiting Materials

Graphitic nanoplatelets (GNPs) and luminescent carbon nanoparticles (CNPs) are simultaneously synthesized by controlling the laser parameters and the size of the graphite flakes. Because luminescent CNPs are attached onto GNPs, a new carbon nanostructure is obtained. Compared with carbon black, GNPs, and luminescent CNPs alone, this nanostructure shows better optical-limiting (OL) effects. The OL mechanism of GNPs that are decorated with luminescent CNPs can mainly be attributed to nonlinear scattering. The role of luminescent CNPs is to promote the formation and growth of nonlinear scattering bubbles, thereby enhancing their optical-limiting effects.

Thermodynamics of face-centered-cubic silicon nucleation at the nanoscale from laser ablation

The thermodynamic nucleation and the phase transition of the face-centered-cubic structure of Si (fcc-Si) on the nanoscale are performed by taking the effect of nanosize-induced additional pressure on the fcc-Si formation under the conditions generated by laser ablation in liquid into account. The thermodynamic analyses showed that the formation of fcc-Si nanocrystals with sizes of 2-6 nm would take place prior to that of large fcc-Si nanocrystals, and the phase transition probability from diamond-like structure Si (d-Si) to fcc-Si is rather high, up to 10(-3)-10(-2), under the conditions created by laser ablation of an Si target in water. These theoretical results suggest that laser ablation in liquid would be an effective industrial route to prepare ultrasmall fcc-Si nanocrystals.

Preparation and optical properties of phthalocyanine–carbon dot blends

To develop better light-capturing nanostructures, we plan to connect an excellent light-harvesting molecule with rich redox chemistry (phthalocyanine, Pc) to a fascinating luminescent material (carbon dots, CDs). Firstly, CDs with diameters of 3.0–5.5 nm were synthesized using a chemical oxidation, and were then blended with Pc phosphoric acid solution under ultrasonication. UV-vis and infrared spectroscopy were used to determine the interactions between CDs and phthalocyanine. The photoluminescent behavior of the blends depends on the proportion of CDs and phthalocyanine used. This can be attributed to the formation of two different structures; sandwich and plum pudding. The Pc–carbon dot blends exhibit broader UV-vis absorption and better visible light emission. Therefore, these findings pave the way for the development of new antenna systems that can capture solar light.

Formation and nonlinear optical properties of carbon nanospindles from laser ablation

Carbon nanospindles are synthesized by laser ablation of carbon black suspension. Their formation could be originated from the coalescence of small carbon nanocrystals because enough time and energy are provided at a long pulse width. At the same level of linear transmittance, carbon nanospindle suspension exhibits better nonlinear optical effects with a 532-nm laser beam than carbon black suspension. The possible mechanism for optical limiting is attributed to the nonlinear scattering from the micro-bubbles.

Drying Behaviour of Gelcast Green Alumina Parts Utilizing PEG Solution

In this work, gelcast alumina green parts were dried by utilizing polyethylene glycol (PEG) solution as the liquid desiccant medium. The parts lost about 30–40 wt% of internal water in a reasonable period of time, i.e. 2–3 h and accomplished most of the shrinkage uniformly, then the part could continue drying in air at the room conditions. Finally, a defect-free porous part could be obtained after the process of the binder burnout at 900oC. The results show that the green part loses more weight at a higher rate while drying in the PEG6000 solution than in the other PEG solutions with different PEG molecular weight. The solid loading of the alumina slurry and the concentration of PEG solution also affect the drying process significantly.