Strong coupling effect at the interface of cobalt phosphate-carbon dots boost photocatalytic water splitting.

Hydrogen and oxygen produced by water splitting under solar energy are ideal future energy sources. At present, obtaining the efficient, stable and inexpensive photocatalyst for photocatalytic overall water splitting is still a huge challenge. Cobalt phosphate (Co3PO4, CoPi) possesses proper band positions for water splitting. However, the fast recombination of photogenerated electron and hole pairs for CoPi restricts its application. Herein, strongly coupling Co3PO4-carbon dots (CoPi-CDs) composite was constructed as an effective strategy to depress the fast recombination behavior of photogenerated electron and hole pairs. CoPi-CDs show superior photocatalytic water splitting activity than that of single CoPi. When the concentration of CDs in the composite is 0.002 gCDs/gcatalyst, the hydrogen production rate was obtained for approximately 0.592 µmol h-1, as well as the oxygen evolution rate about 0.258 µmol h-1 (with 2:1 stoichiometry), which are both nearly 33 times than that of pristine CoPi. This enhanced photocatalytic activity of CoPi-CDs should ascribe to the efficient coupling effect between CoPi and CDs, which allows fast electron transfer at the interface of CoPi and CDs and thus effectively boosts the photocatalytic water splitting. The strongly coupling nanocomposites should be inspiring for further nanocomposite building for photocatalytic overall water splitting.

Study on highly enhanced photocatalytic tetracycline degradation of type â ¡ AgI/CuBi2O4 and Z-scheme AgBr/CuBi2O4 heterojunction photocatalysts.

Removal of antibiotics from aqueous solutions by photocatalysis is an advanced technology for environmental remediation. Herein, we have fabricated a series of AgX (X = I, Br)/CuBi2O4 composites through an in-situ precipitation method. The photocatalytic activity of the obtained photocatalysts was measured by the degradation of tetracycline (TC) under visible light irradiation (λ > 420 nm). All the AgX (X = I, Br)/CuBi2O4 composites exhibit much higher photocatalytic activity than that of pure CuBi2O4. The enhanced photocatalytic activity is mainly attributed to the efficient interfacial charge separation and migration in the AgX (X = I, Br)/CuBi2O4 heterojunctions. Meanwhile, AgX (X = I, Br)/CuBi2O4 heterojunctions display excellent photocatalytic stability, and the photocatalytic degradation rates were not obvious decreased even after five successive cycles. Based on the energy band structure, the radicals trapping and electronic spin resonance (ESR) experiments, the Z-scheme mechanism of AgBr/CuBi2O4 and type II mechanism of AgI/CuBi2O4 heterojunction photocatalysts were tentatively discussed, respectively.

High-bright fluorescent carbon dot as versatile sensing platform.

The surface functionalization will introduce additional functional groups on carbon dots (CDs) surface and then enrich the properties of CDs. Here, we show the various surface functionalized CDs (-COOH, -OH, -SH, -NH2, etc, named as NS-CDs) were synthesized with fascinating features, including high quantum efficiency (38.9%), long-term stability and good biocompatibility. Notably, it can serve as multifunction fluorescent probe in sensing system, including label-free detections in hydrogen peroxide (H2O2) with a wide linear range (1.20 × 10-3 - 8.80 × 10-12M) and a low limit of detection (LOD, 1.00 × 10-12M); and glutathione, covering a concentration range of 2.00 × 10-3 - 1.00 × 10-7M and LOD of 1.00 × 10-7M. In addition, the NS-CDs as fluorescent probe could selectively detect metal ions (such as, Hg2+, 1.00 × 10-8 - 1.50 × 10-3M, 1.00 × 10-7M), antibiotics (tetracycline, 1.00 ×10-10 - 2.50 × 10-5M, 1.00 ×10-10M) and toxic pollutant (nitrobenzene, 5.00 × 10-7 to 1.00 × 10-3gL-1, 5.00 × 10-7gL-1) with wide linear range and satisfactory detection limits.

A Pt-Co3O4-CD electrocatalyst with enhanced electrocatalytic performance and resistance to CO poisoning achieved by carbon dots and Co3O4 for direct methanol fuel cells.

Highly efficient electrocatalysts remain huge challenges in direct methanol fuel cells (DMFCs). Here, a Pt-Co3O4-CDs/C composite was fabricated as an anode electrocatalyst with low Pt content (12 wt%) by using carbon dots (CDs) and Co3O4 nanoparticles as building blocks. The Pt-Co3O4-CDs/C composite catalyst shows a significantly enhanced electrocatalytic activity (1393.3 mA mg-1 Pt), durability (over 4000 s) and CO-poisoning tolerance. The superior catalytic activity should be attributed to the synergistic effect of CDs, Pt and Co3O4. Furthermore, the Pt-Co3O4-CDs/C catalyst was integrated into a single cell, which exhibits a maximum power density of 45.6 mW cm-2, 1.7 times the cell based on the commercial 20 wt% Pt/C catalyst.

Pyridine derivative-induced fluorescence in multifunctional modified carbon dots and their application in thermometers.

We present a simple hydrothermal method to fabricate multifunctional modified carbon dots (with -COOH, -OH, -SH, and -NH2 groups, named NS-Cdots) using citric acid and l-cysteine as raw materials. The functional NS-Cdots exhibit high fluorescent quantum yield (38.9%), low cytotoxicity and good biocompatibility. A reasonable photoluminescence mechanism of the NS-Cdots was proposed in which the pyridine derivatives serve as conjugating units and dominate the main emission behavior. The NS-Cdots can also be used as excellent fluorescent probes for cell imaging in vitro and as effective thermometers with a wide temperature detection range from 20 °C to 95 °C.

N,S co-doped carbon dots as a stable bio-imaging probe for detection of intracellular temperature and tetracycline.

Stable bioimaging with nanomaterials in living cells has been a great challenge and of great importance for understanding intracellular events and elucidating various biological phenomena. Herein, we demonstrate that N,S co-doped carbon dots (N,S-CDs) produced by one-pot reflux treatment of C3N3S3 with ethane diamine at a relatively low temperature (80 °C) exhibit a high fluorescence quantum yield of about 30.4%, favorable biocompatibility, low-toxicity, strong resistance to photobleaching and good stability. The N,S-CDs as an effective temperature indicator exhibit good temperature-dependent fluorescence with a sensational linear response from 20 to 80 °C. In addition, the obtained N,S-CDs facilitate high selectivity detection of tetracycline (TC) with a detection limit as low as 3 × 10-10 M and a wide linear range from 1.39 × 10-5 to 1.39 × 10-9 M. More importantly, the N,S-CDs display an unambiguous bioimaging ability in the detection of intracellular temperature and TC with satisfactory results.

Concentrations dominated membrane permeability variation by fullerol nanoparticles on a single living HeLa cell.

The effects in HeLa cell membrane permeability caused by the fullerenols C60(OH)n with different concentrations were studied by scanning electrochemical microscopy (SECM). We demonstrate that C60(OH)n has very low cytotoxicity, although it can still have strong effects on the cell membrane permeability. In the presence of 1 × 10-3 mg mL-1 (1 ppm) C60(OH)n, the cell membrane permeability increases by 26% after 76 min, which is reversible. When C60(OH)n concentration is over 25 × 10-3 mg mL-1 (25 ppm), the change in membrane permeability (increased 19%) is irreversible.

Carbon quantum dot/CuSx nanocomposites towards highly efficient lubrication and metal wear repair.

Mechanical wear accounts for one third of present global energy consumption. However, it still lacks an efficient lubricant to simultaneously achieve a highly efficient lubrication and metal wear repair. Herein, we report that carbon quantum dots (CQDs)/CuSx nanocomposites show enhanced lubrication and metal wear surface repair abilities when used as additives. The highly efficient lubrication and metal wear repair properties should be attributed to the combination of the multi-layer graphite structure of CQDs and the high chemical activity of CuSx nanoparticles.