Preparation and properties of copper-oil-based nanofluids

In this study, the lipophilic Cu nanoparticles were synthesized by surface modification method to improve their dispersion stability in hydrophobic organic media. The oil-based nanofluids were prepared with the lipophilic Cu nanoparticles. The transport properties, viscosity, and thermal conductivity of the nanofluids have been measured. The viscosities and thermal conductivities of the nanofluids with the surface-modified nanoparticles have higher values than the base fluids do. The composition has more significant effects on the thermal conductivity than on the viscosity. It is valuable to prepare an appropriate oil-based nanofluid for enhancing the heat-transfer capacity of a hydrophobic system. The effects of adding Cu nanoparticles on the thermal oxidation stability of the fluids were investigated by measuring the hydroperoxide concentration in the Cu/kerosene nanofluids. The hydroperoxide concentrations are observed to be clearly lower in the Cu nanofluids than in their base fluids. Appropriate amounts of metal nanoparticles added in a hydrocarbon fuel can enhance the thermal oxidation stability

Formation of PbSe/CdSe Core/Shell Nanocrystals for Stable Near-Infrared High Photoluminescence Emission

PbSe/CdSe core/shell nanocrystals with quantum yield of 70% were obtained by the “successive ion layer adsorption and reaction” technology in solution. The thickness of the CdSe shell was exactly controlled. A series of spectral red shifts with the CdSe shell growth were observed, which was attributed to the combined effect of the surface polarization and the expansion of carriers’ wavefunctions. The stability of PbSe nanocrystals was tremendously improved with CdSe shells

Functionalized Mesoporous SBA-15 with CeF3: Eu3+ Nanoparticle by Three Different Methods: Synthesis, Characterization, and Photoluminescence

Luminescence functionalization of the ordered mesoporous SBA-15 silica is realized by depositing a CeF3: Eu3+ phosphor layer on its surface (denoted as CeF3: Eu3+/SBA-15/IS, CeF3: Eu3+/SBA-15/SI and CeF3: Eu3+/SBA-15/SS) using three different methods, which are reaction in situ (I-S), solution impregnation (S-I) and solid phase grinding synthesis (S-S), respectively. The structure, morphology, porosity, and optical properties of the materials are well characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, N2 adsorption, and photoluminescence spectra. These materials all have high surface area, uniformity in the mesostructure and crystallinity. As expected, the pore volume, surface area, and pore size of SBA-15 decrease in sequence after deposition of the CeF3: Eu3+ nanophosphors. Furthermore, the efficient energy transfer in mesoporous material mainly occurs between the Ce3+ and the central Eu3+ ion. They show the characteristic emission of Ce3+ 5d → 4f (200–320 nm) and Eu3+5D0 → 7FJ(J = 1–4, with 5D0 → 7F1 orange emission at 588 nm as the strongest one) transitions, respectively. In addition, for comparison, the mesoporous material CeF3: Eu3+/SBA-15/SS exhibits the characteristic emission of Eu3+ ion under UV irradiation with higher luminescence intensity than the other materials

White-light emitting hydrogen-bonded supramolecular copolymers based on π-conjugated oligomers

Three different pi-conjugated oligomers (a blue-emitting oligofluorene, a green-emitting oligo(phenylene vinylene), and a red-emitting perylene bisimide) have been functionalized with self-complementary quadruple hydrogen bonding ureidopyrimidinone (UPy) units at both ends. The molecules self-assemble in solution and in the bulk, forming supramolecular polymers. When mixed together in solution, random noncovalent copolymers are formed that contain all three types of chromophores, resulting in energy transfer upon excitation of the oligofluorene energy donor. At a certain mixing ratio, a white emissive supramolecular polymer can be created in solution. In contrast to their unfunctionalized counterparts, bis-UPy-chromophores can easily be deposited as smooth thin films on surfaces by spin coating. No phase separation is observed in these films, and energy transfer is much more efficient than in solution, giving rise to white fluorescence at much lower ratios of energy acceptor to donor. Light emitting diodes based on these supramolecular polymers have been prepared from all three types of pure materials, yielding blue, green, and red devices, respectively. At appropriate mixing ratios of these three compounds, white electroluminescence is observed. This approach yields a toolbox of molecules that can be easily used to construct pi-conjugated supramolecular polymers with a variety of compositions, high solution viscosities, and tuneable emission colors

High sensitization efficiency and energy transfer routes for population inversion at low pump intensity in Er organic complexes for IR amplification

J.X.H., H.Y., H.L. and Y.P.Z. were financially supported by the China Scholarship Council and Queen Mary University of London (QMUL). S.K. was supported by a Proof of Concept grant funded by QMUL and the EPSRC through the Silicon Photonics for Future Systems grant EP/L00044X. J.G. was financially supported by QMUL. I.H. acknowledges financial support from the EU FP7 (Marie Curie-CIG-Grant 303535). Y.Z. acknowledges financial support from the Major State Basic Research Development Program (2013CB922101) and NSFC (21371093). W.P.G. acknowledges financial support from EPSRC (EP/L020114/1 and EP/P007767/1) and from NSFC (61574095