Yongqiang Dong

Carbon-Based Dots Co-doped with Nitrogen and Sulfur for High Quantum Yield and Excitation-Independent Emission†

Helpful elements: A facile bottom-up method using citric acid and L-cysteine as a precursor has been developed to prepare graphene quantum dots (GQDs) co-doped with nitrogen and sulfur. A new type and high density of surface state of GQDs arises, leading to high yields (more than 70 %) and excitation-independent emission. FLQY = fluorescence quantum yield.

One-step and high yield simultaneous preparation of single- and multi-layer graphene quantum dots from CX-72 carbon black

A facile, low cost and high yield method has been developed to prepare single- and multi-layer graphene quantum dots (GQDs) from XC-72 carbon black by chemical oxidation. The single-layer GQDs are demonstrated to be excellent probes for cellular imaging, while the multi-layer GQDs may offer great potential applications in optoelectronic devices.

Graphene quantum dots/L-cysteine coreactant electrochemiluminescence system and its application in sensing lead(II) ions.

A new coreactant electrochemiluminescence (ECL) system including single-layer graphene quantum dots (GQDs) and L-cysteine (L-Cys) was found to be able to produce strong cathodic ECL signal. The ECL signal of GQD/L-Cys coreactant system was revealed to be mainly dependent on some key factors, including the oxidation of L-Cys, the presence of dissolved oxygen and the reduction of GQDs. Then, a possible ECL mechanism was proposed for the coreactant ECL system. Furthermore, the ECL signal of the GQD/L-Cys system was observed to be quenched by lead(II) ions (Pb(2+)). After optimization of some important experimental conditions, including concentrations of GQDs and L-Cys, potential scan rate, response time, and pH value, an ECL sensor was developed for the detection of Pb(2+). The new methodology can offer a rapid, reliable, and selective detection of Pb(2+) with a detection limit of 70 nM and a dynamic range from 100 nM to 10 μM.

Cesium Carbonate Functionalized Graphene Quantum Dots as Stable Electron-Selective Layer for Improvement of Inverted Polymer Solar Cells

Solution processable inverted bulk heterojunction (BHJ) polymer solar cells (PSCs) are promising alternatives to conventional silicon solar cells because of their low cost roll-to-roll production and flexible device applications. In this work, we demonstrated that Cs2CO3 functionalized graphene quantum dots (GQDs-Cs2CO3) could be used as efficient electron-selective layers in inverted PSCs. Compared with Cs2CO3 buffered devices, the GQDs-Cs2CO3 buffered devices show 56% improvement in power conversion efficiency, as well as 200% enhancement in stability, due to the better electron-extraction, suppression of leakage current, and inhibition of Cs(+) ion diffusion at the buffer/polymer interface by GQDs-Cs2CO3. This work provides a thermal-annealing-free, solution-processable method for fabricating electron-selective layer in inverted PSCs, which should be beneficial for the future development of high performance all-solution-processed or roll-to-roll processed PSCs.

2D single- or double-layered vanadium oxide nanosheet assembled 3D microflowers: controlled synthesis, growth mechanism, and applications

A facile one-pot solvent-thermal method was developed to synthesize a unique 3D microflower structure assembled from single- or double-layered 2D nanosheets of V4O9 (F-VO). Simply by controlling the precursor concentration, yolk-shelled V4O9 (YS-VO) or bulk V4O9 (B-VO) can be produced instead. The precursor-concentration dependent growth mechanism is proposed. The exceptional catalytic/electrochemical properties and large specific surface area of F-VO promise a wide range of applications. As a proof-of-concept demonstration, we investigate its use in high-performance supercapacitors (~392 F g(-1)), and for sensitive detection of H2O2 (with a low detection limit of ~0.1 μM) and methanol (with a low detection limit of ~60 μM). Furthermore, we show that F-VO greatly outperforms its counterparts (YS-VO and B-VO) presumably owing to its unique structure and crystal plane orientation.

Nitrogen-doped carbon-based dots prepared by dehydrating EDTA with hot sulfuric acid and their electrocatalysis for oxygen reduction reaction

Nitrogen-doped carbon-based dots (N-CDs) with good electrocatalytic activity for oxygen reduction reaction have been prepared by dehydrating ethylenediaminetetraacetic acid with hot and concentrated sulfuric acid. The as-prepared N-CDs are graphite-based nanosheets with an average lateral size of ∼7 nm and a mean thickness of ∼1.7 nm. The N-CDs possess abundant oxygen-containing groups and emit blue fluorescence under 365 nm UV light. Furthermore, the as-prepared N-CDs can be well deposited on graphene through a hydrothermal treatment, and show outstanding electrocatalytic activity for the oxygen reduction reaction.