In this work, we firstly prepared new sealed graphene capsules (GCs) that were about 300 nm in size and had different morphologies using a simple reduction method. The quality of the graphene oxide (GO) sheets and the concentration of hydrazine hydrate are proposed to be influencing factors for the formation of sealed graphene capsules. GCs are covalently functionalized with 5,10,15,20-tetra-(4-aminophenyl)porphyrin, forming dispersible GC–aminoporphyrins in aqueous solution. The observed fluorescence quenching of the GCs by the aminoporphyrin indicated that the GCs are electron donors and electron transfer occurs from the GCs to the aminoporphyrin. This Förster Resonance Energy Transfer (FRET) between the GCs and aminoporphyrins is probably the reason for the enhancement of 1O2 generation of the GC–aminoporphyrins. More importantly, the as-prepared GC–aminoporphyrin nanohybrids as novel photosensitizers (PSs) with a short excitation wavelength can be used as PDT reagents for the treatment of malignant melanoma A375 with high efficiency. We expect that GC–aminoporphyrins will be promising PSs in future cancer therapy.

•Translucent TiO2 nanotubes were used as substrate for QDSSCs.•CdSxSe1-x/Mn-CdS QDs were sensitized onto TiO2 nanotubes by a two-stage strategy.•The photoresponse of CdSxSe1-x/Mn-CdS/TiO2 nanotubes could be tuned with S/Se.•Extra CdSe layers can improve the power conversion efficiency to 3.26%.•Electrochemical measurements well evidenced the improved photovoltaic performance.Translucent TiO2 nanotube (NT) array film has been used as supporter materials for the fabrication of CdSxSe1-x/Mn-CdS quantum dot sensitized solar cell (QDSSC). The TiO2 NT array electrodes are sensitized with Mn-CdS and CdSxSe1-x QDs by employing a two-stage sensitization strategy combining successive ionic layer adsorption and reaction (SILAR) techniques and hydrothermal process. The photoresponse region of CdSxSe1-x/Mn-CdS/TiO2 NT electrodes could be controlled by the ratio of S and Se. By systematical investigation the optimal composition of CdSxSe1-x, a high power conversion efficiency of 2.41% is obtained with CdS0.47Se0.53/Mn-CdS/TiO2 NT QDSSC prepared with feed molar ratio of S:Se = 0:4. After being coated with 3 SILAR cycles of CdSe on the CdS0.47Se0.53/Mn-CdS/TiO2 NT electrode, the power conversion efficiency could be further improved to the highest value of 3.26%. The enhancement of power conversion efficiency is mainly attributed to the significant increase of short-circuit current density (Jsc) which resulted from the improved light harvesting ability caused by expanded light absorption range and efficient electrons collection caused by mid-gap states created by Mn-CdS. These results are well evidenced with the photovoltaic performance studies (J-V behaviors), incident photon to charge carrier generation efficiency (IPCE), and electrochemical impedance spectroscopy (EIS).

In this paper, we report on the successful preparation of high-quality graphene sheets with a large-size in N,N-dimethylformamide (DMF) solvent by sonication-free liquid-phase exfoliation (LPE) of graphite assisted with urea as the precursor of the intercalating agent melamine. Through the characterizations of the graphene sheets obtained with transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy and XPS, these graphene sheets were found to be high-quality, defect-free, single or-few-layer with areas in the range of 100–1000 μm2. The influences of reflux time and the mass ratio of urea to graphite on the graphene concentration (CG) in the resulting dispersions were investigated. The graphene dispersions were fabricated into flexible films that show comparable conductivity. The exfoliation mechanism of graphite in our new sonication-free LPE method is also discussed.

C dots (CDs) are among the most promising emerging fluorescent labels for biological imaging and sensing. A facile new synthesis method was developed using common organic solvents for fabricating CDs from candle soot. The common organic solvents were used as extractants and the obtained CDs have a narrow size distribution with average diameters of about 3.4 nm for ethylene glycol, 3.5 nm for ethanol, and 3.4 nm for n-butanol. This approach is simpler, easier, and more effective than other methods currently used for CD fabrication. The obtained CDs had a high quantum yield (38 %), tunable emission and are water-soluble. The mechanism for the luminescence of the CDs was investigated and the results indicate that the ability of the solvent to disperse the CDs plays a very important role in the photoluminescence of these CDs. The type of organic solvent and the surface groups on the CDs also influenced the optical properties of the CDs. Different emissive traps are shown to play the major role in the luminescence of the carbon materials. An in vitro hemolysis assay was performed and showed that the CDs are biocompatible.

In this paper, we firstly report the preparation of 3D graphene networks (GNs) by sonication-free liquid-phase exfoliation (LPE) and C dot grafted graphene (CD–G) hybrids. The 3D GNs and CD–G hybrids were incorporated into TiO2 photoanodes for improving the photovoltaic performance of CdS/CdSe quantum dot sensitized solar cells (QDSSCs) due to their unique structures and excellent conductivities. When the amounts of incorporation are 1.6 wt% for GNs and 2.0 wt% for CD–G, η (photoelectric conversion efficiency) exhibited improvements from 4.04% to 4.37% and 4.69%, respectively. The remarkable improvements in η are predominantly ascribed to the fact that the electron transport from TiO2 to graphene decreased the probability of recombination of charge carriers and ultimately improved the photoelectric conversion efficiency. For CD–G/TiO2, the electron transport from C dots to graphene may strengthen the effect. This work demonstrates a possibility of fabricating superior photoanodes for enhancing the performances of QDSSCs by designing graphene nanoarchitectures with unique structures and morphologies as the dopants.