Yanmei Yang

Fluorescent N-Doped Carbon Dots as in Vitro and in Vivo Nanothermometer

The fluorescent N-doped carbon dots (N-CDs) obtained from C3N4 emit strong blue fluorescence, which is stable with different ionic strengths and time. The fluorescence intensity of N-CDs decreases with the temperature increasing, while it can recover to the initial one with the temperature decreasing. It is an accurate linear response of fluorescence intensity to temperature, which may be attributed to the synergistic effect of abundant oxygen-containing functional groups and hydrogen bonds. Further experiments also demonstrate that N-CDs can serve as effective in vitro and in vivo fluorescence-based nanothermometer.

A nickel nanoparticle/carbon quantum dot hybrid as an efficient electrocatalyst for hydrogen evolution under alkaline conditions

The exploration of an efficient electrocatalyst for hydrogen evolution reaction (HER) from water is a key to relieve the energy crisis, which is a great challenge. Herein, a nickel nanoparticle/carbon quantum dot (Ni/CQD) hybrid is synthesized and evaluated as an electrocatalyst for HER under a strongly alkaline medium (1 M KOH solution). The obtained Ni/CQD hybrid shows good catalytic ability for HER with an onset potential comparable to that of Pt wire and a low Tafel slope of 98 mV dec−1, which may be attributed to the Ni–O–C interface between Ni NPs and CQDs. The Ni/CQDs also exhibit high stability after 1000 CV cycles with negligible current loss (around 1 mA cm−2). Moreover, the catalytic ability of Ni/CQDs can be further improved under visible light illumination, suggested by a lower Tafel slope of 77 mV dec−1.

Silver modified carbon quantum dots for solvent-free selective oxidation of cyclohexane

Despite tremendous efforts devoted to the study of new nanocatalysts, obtaining effective nanocatalysts for the oxidation of cyclohexane under mild conditions is still a great challenge. The silver modified carbon quantum dots were synthesized by a simple chemistry method and demonstrated to exhibit excellent catalytic ability for cyclohexane oxidation (conversion based on cyclohexane reached about 58.9% and selectivity to cyclohexanone reached about 84.6%) under visible light, which can be attributed to the synergistic catalysis of Ag nanoparticles and carbon quantum dots. Besides, the carbon quantum dots can stabilize Ag nanoparticles for the prevention of aggregation. Moreover, the silver modified carbon quantum dots showed good reusability, being reused after ten consecutive runs. Based on a series of experiments, it can be concluded that the silver modified carbon quantum dots are green and efficient nanocatalysts for the oxidation of cyclohexane.

Visible-Light-Induced Effects of Au Nanoparticle on Laccase Catalytic Activity.

A deep understanding of the interaction between the nanoparticle and enzyme is important for biocatalyst design. Here, we report the in situ synthesis of laccase-Au NP (laccase-Au) hybrids and its catalytic activity modulation by visible light. In the present hybrid system, the activity of laccase was significantly improved (increased by 91.2% vs free laccase) by Au NPs. With a short time visible light illumination (λ > 420 nm, within 3 min), the activity of laccase-Au hybrids decreased by 8.1% (vs laccase-Au hybrid without light), which can be restored to its initial one when the illumination is removed. However, after a long time illumination (λ > 420 nm, over 10 min), the catalytic activity of laccase-Au hybrids consecutively decreases and is not reversible even after removing the illumination. Our experiments also suggested that the local surface plasma resonance effect of Au NPs causes the structure change of laccase and local high temperature near the Au NPs. Those changes eventually affect the transportation of electrons in laccase, which further results in the declined activity of laccase.

Copper nanoparticle/carbon quantum dots hybrid as green photocatalyst for high-efficiency oxidation of cyclohexane

To develop green catalysts for cyclohexane oxidation with high efficiency and high selectivity is a trend in nanotechnology and nanocatalysis. In this work, we demonstrate that copper nanoparticles/carbon quantum dots (Cu/CQDs) hybrid as photocatalyst exhibits excellent catalytic activity in the oxidation of cyclohexane (conversion based on cyclohexane of 50.2% and selectivity to cyclohexanone of about 78.3%) under a low temperature with tert-butyl hydroperoxide as oxidant. It is worth mentioning that the Cu/CQDs hybrid photocatalyst can be implemented in efficient catalytic oxidation of cyclohexane under a mild condition (60 °C), which may provide a cogent pathway for the development of high-performance catalysts for C–H oxidation.

Semi-carbonized nanostructures of carbohydrate for highly efficient photocatalysts

We demonstrate that the semi-carbonized nanostructures of carbohydrate (cellulose and glucose as precursors) show high performance as photocatalysts directly for selective oxidation of cis-cyclooctene with air as an oxidant. Three dimensionally macroporous carbon spheres (3DMPCS) prepared from cellulose carbonized at 500 °C yielded the highest conversion of cis-cyclooctene (32.6%) and a high selectivity of 2-hydroxycyclooctanone (90.4%) after 24 h reaction, while cellulose carbonized at lower heat treatment temperatures (HTTs) (0–400 °C) or higher (600–900 °C) gave lower cis-cyclooctene conversion. The 3DMPCS synthesized from glucose carbonized at 600 °C shows higher performance in selective oxidation of cis-cyclooctene (12.2% conversion of cis-cyclooctene and 75.4% selectivity of 2-hydroxycyclooctanone) than glucose carbonized at other HTTs (200–500 °C and 700–900 °C) as catalysts. The results indicate that the semi-carbonized nanostructures of carbohydrates are highly efficient photocatalysts.