Yaodong Liu

In situ synthesis of NIR-light emitting carbon dots derived from spinach for bio-imaging applications

Near infrared (NIR)-light emitting fluorescent probes have attracted extensive research attention in the bioimaging field due to their deep tissue penetration, minimal auto-fluorescence and lower emission light damage to bio-tissues. Herein, we designed and prepared NIR-light emitting CDs (R-CDs) from spinach by a one-step solvothermal method. The R-CDs exhibited good water solubility, a maximum fluorescence emission peak at 680 nm, a high quantum yield of 15.34%, remarkable photo-stability and resistance to metal ions in a body-simulating environment, excellent compatibility, negligible toxicity, and superior labelling capability in vitro and in vivo. These findings significantly highlight the design of NIR-light emitting CDs and exploit their bio-imaging applications.

Novel wearable polyacrylonitrile/phase-change material sheath/core nano-fibers fabricated by coaxial electro-spinning

This study focused on the preparation of wearable polyacrylonitrile (PAN)/phase-change material (PCM) sheath/core nano-fibers by coaxial electro-spinning technology. PAN was used as the sheath material to make fibers comfortable to human skin, and isopropyl palmitate and paraffin oil were used as sample PCMs. The electro-spinning conditions are critical for encapsulating a PCM by a PAN shell and forming a uniform sheath–core structure. Our experiments show that these PCMs could be well encapsulated in PAN hollow fibers and function to stabilize environmental temperature in a narrow range. This study provides a versatile and feasible way to fabricate PAN/PCM sheath/core homo-thermal nano-fibers with various temperature stabilization windows. Using these homo-thermal nano-fibers as clothing materials will be able to abate people’s discomfort during a sudden environmental temperature change.

A high-yield and versatile method for the synthesis of carbon dots for bioimaging applications

A facile and versatile molten-salt method was developed to prepare hydrosoluble carbon dots (CDs) from various precursors, in high yields and on a large scale. Citric acid-based CDs (CA-CDs) were obtained in a maximum yield of 39.6% and exhibited a high fluorescence quantum yield of 20.8% without any passivation. The CA-CDs showed little cytotoxicity even at a concentration as high as 800 μg mL-1. In addition, CA-CDs could be used as multicolour fluorescence imaging agents in vitro with blue, green, and red fluorescence emissions at excitation wavelengths of 405, 488, and 543 nm, respectively. Moreover, the CA-CDs could be chelated with gadolinium ions (Gd3+) to construct Gd-CA-CDs for dual-mode magnetic resonance and fluorescence imaging. The Gd-CA-CDs showed good water dispersibility, excellent biocompatibility, a strong fluorescence quantum yield of 13.1%, and a high magnetic resonance relaxivity of 22.45 mM-1 s-1. The molten-salt method was demonstrated to be applicable to other precursors, such as sodium lignosulphonate, sucrose, glucose, and p-phenylenediamine, and the maximum yield of the four as-prepared CDs was as high as 66.7%, which is much higher than the value reported in previous studies. This study proves that the molten-salt synthesis is a versatile method to obtain CDs in high yields, which will promote the application of CDs in the field of bioimaging.

A sulfur host based on cobalt–graphitic carbon nanocages for high performance lithium–sulfur batteries

Owing to the high theoretical specific capacity of sulfur (1675 mA h g−1), lithium–sulfur batteries display fascinating potential for high-capacity energy storage. However, their practical applications are still hindered by the fast capacity decay and poor cycling stability. In this work, a sulfur host based on MOF-derived cobalt–graphitic carbon nanocages is prepared by annealing the MOF (ZIF-67) in a H2/Ar atmosphere. This unique structure can provide both the physical encapsulation of polysulfides by the graphitic carbon shell and chemical entrapment of polysulfides by the Co nanoparticles embedded in the carbon shell. In addition, the nanocages with inner void space not only allow a relatively higher loading content of sulfur but also alleviate the volume expansion of sulfur upon lithiation. As a result, the GC–Co electrodes with a high sulfur loading content of 77 wt% display a high specific capacity at different current densities and long-term cycling performance of 500 cycles at 1C with an ultra-low capacity decay of 0.015% per cycle.

Dynamic Self-Stiffening and Structural Evolutions of Polyacrylonitrile/Carbon Nanotube Nanocomposites

The self-stiffening under external dynamic strain has been observed for some artificial materials, especially for nanocomposites. However, few systematic studies have been carried out on their structural evolutions, and the effect of the types of nanofillers was unclear. In this study, we used a semicrystalline polymer, polyacrylonitrile (PAN), and various types of carbon nanomaterials including C60, carbon nanotube (CNT), and graphene oxide (GO). An external uniaxial dynamic strain at small amplitude of 0.2% was applied on the prepared nanocomposite films. It was observed that PAN/CNT exhibited significant self-stiffening behavior, whereas PAN/GO showed no response. Systematic characterizations were performed to determine the structural evolutions of PAN/CNT film during dynamic strain testing, and it was found that the external dynamic strain not only induced the crystallization of PAN chains but also aligned CNT along the strain direction.

Rheological transitions and in-situ IR characterizations of cellulose/LiCl·DMAc solution as a function of temperature

Abstract Cellulose was dissolved in LiCl/DMAc solvent system at various concentrations. Using rheological measurements, we observed that the cellulose solution becomes gelled upon heating and jelly-like during cooling. Interestingly, while phase separation occurs during heating (from room temperature to higher) along with a sol–gel transition, and this transition is irreversible, the cooling (from room temperature to lower) induced solution property transition from more viscous to more elastic is completely reversible. The structural changes of cellulose solution during heating and cooling cycles are in situ monitored by infrared spectroscopy, and we found that the temperature of the solution affects the interactions among DMAc, lithium cations, chloride anions, and the hydroxyl groups in cellulose chains. While heating induces phase separation and gelation of cellulose solutions, cooling simply turns the solution into a reversible jelly status. Also, when cellulose concentration increases, the gelation temperature caused by heating becomes significantly lower. Possible mechanisms of the rheological transitions of cellulose/LiCl·DMAc solutions during either heating or cooling are proposed in this study.Graphical abstract