Nanophotonics and Nanochemistry: Controlling the Excitation Dynamics for Frequency Up- and Down-Conversion in Lanthanide-Doped Nanoparticles

Nanophotonics is an emerging science dealing with the interaction of light and matter on a nanometer scale and holds promise to produce new generation nanophosphors with highly efficient frequency conversion of infrared (IR) light. Scientists can control the excitation dynamics by using nanochemistry to produce hierarchically built nanostructures and tailor their interfaces. These nanophosphors can either perform frequency up-conversion from IR to visible or ultraviolet (UV) or down-conversion, which results in the IR light being further red shifted. Nanophotonics and nanochemistry open up numerous opportunities for these photon converters, including in high contrast bioimaging, photodynamic therapy, drug release and gene delivery, nanothermometry, and solar cells. Applications of these nanophosphors in these directions derive from three main stimuli. Light excitation and emission within the near-infrared (NIR) “optical transparency window” of tissues is ideal for high contrast <i>in vitro</i> and <i>in vivo</i> imaging. This is due to low natural florescence, reduced scattering background, and deep penetration in tissues. Secondly, the naked eye is highly sensitive in the visible range, but it has no response to IR light. Therefore, many scientists have interest in the frequency up-conversion of IR wavelengths for security and display applications. Lastly, frequency up-conversion can convert IR photons to higher energy photons, which can then readily be absorbed by solar materials. Current solar devices do not use abundant IR light that comprises almost half of solar energy.In this Account, we present our recent work on nanophotonic control of frequency up- and down-conversion in fluoride nanophosphors, and their biophotonic and nanophotonic applications. Through nanoscopic control of phonon dynamics, electronic energy transfer, local crystal field, and surface-induced non-radiative processes, we were able to produce new generation nanophosphors with highly efficient frequency conversion of IR light. We show that nanochemistry plays a vital role in the design and interface engineering of nanophosphors, providing pathways to expand their range of applications. High contrast <i>in vitro</i> and <i>in vivo</i> NIR-to-NIR up- and down-conversion bioimaging were successfully demonstrated by our group, evoking wide interests along this line. We introduced trivalent gadolinium ions into the lattice of the nanophosphors or into the shell layer of nanophosphors in a core/shell configuration to produce novel nanophosphors for multimodal (MRI and optical) imaging. We also demonstrate the security and display applications using photopatternable NIR-to-NIR and NIR-to-visible frequency up-conversion nanophosphors with appropriately engineered surface chemistry. In addition, we present preliminary results on dye-sensitized solar cells using up-conversion in fluoride lattice-based nanophosphors for IR photon harvesting

Graphene Helicoid: Distinct Properties Promote Application of Graphene Related Materials in Thermal Management

The extremely high thermal conductivity of graphene has received great attention both in experiments and calculations. Obviously, new features in thermal properties are of primary importance for application of graphene-based materials in thermal management in nanoscale. Here, we studied the thermal conductivity of graphene helicoid, a newly reported graphene-related nanostructure, using molecular dynamics simulation. Interestingly, in contrast to the converged cross-plane thermal conductivity in multilayer graphene, axial thermal conductivity of graphene helicoid keeps increasing with thickness with a power law scaling relationship, which is a consequence of the divergent in-plane thermal conductivity of two-dimensional graphene. Moreover, the large overlap between adjacent layers in graphene helicoid also promotes higher thermal conductivity than multilayer graphene. Furthermore, in the small strain regime (<10%), compressive strain can effectively increase the thermal conductivity of graphene helicoid, while in the ultra large strain regime (∼100% to 500%), tensile strain does not decrease the heat current, unlike that in generic solid-state materials. Our results reveal that the divergence in thermal conductivity, associated with the anomalous strain dependence and the unique structural flexibility, makes graphene helicoid a new platform for studying fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene-related materials

Synthesis of a fumed silica-supported poly-3-(2-aminoethylamino)propylsiloxane platinum complex and its catalytic behavior in the hydrosilylation of olefins with triethoxysilane

<p>A novel fumed silica-supported bidentate nitrogen platinum complex was conveniently prepared from N-(2-aminoethyl)-3-aminopropyltriethoxysilane via immobilization on fumed silica followed by a reaction with hexachloroplatinic acid. The title complex was systematically characterized and analyzed by Fourier Transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and specific surface area analysis (BET). The resulting title complex was found to be efficient and stable in catalyzing the hydrosilylation reaction of olefins with triethoxysilane. Furthermore, the polymeric platinum complex could be separated by simple filtration and reused four times without any appreciable loss of catalytic activity.</p

Activities of factor V and VIII after mpHHP treatment (200/250 Mpa, 5 cycles of 1min) at near 0°C temperature, n = 3.

<p>Activities of factor V and VIII after mpHHP treatment (200/250 Mpa, 5 cycles of 1min) at near 0°C temperature, n = 3.</p

Inactivation of <i>E</i>.<i>coli</i> under mpHHP (5 cycles of 1 min) and spHHP (1 cycle of 5 min) application modes with escalated pressure, n = 3.

<p>Inactivation of <i>E</i>.<i>coli</i> under mpHHP (5 cycles of 1 min) and spHHP (1 cycle of 5 min) application modes with escalated pressure, n = 3.</p

Kinetics of bacterium inactivation by optimized HHP treatment (200/250 Mpa, 5 cycles of 1min, at near 0°C temperature), n = 3.

<p>Kinetics of bacterium inactivation by optimized HHP treatment (200/250 Mpa, 5 cycles of 1min, at near 0°C temperature), n = 3.</p

Inactivation of <i>E</i>.<i>coli</i> under two mpHHP modes (200/250 Mpa, 5 cycles of 1min) at low temperature (near 0°C) and room temperature, n = 3.

<p>Inactivation of <i>E</i>.<i>coli</i> under two mpHHP modes (200/250 Mpa, 5 cycles of 1min) at low temperature (near 0°C) and room temperature, n = 3.</p

The content of plasma proteins after HHP treatment (200/250 Mpa, 5 cycles of 1min, at near 0°C temperature), n = 3, mean±SD.

<p>The content of plasma proteins after HHP treatment (200/250 Mpa, 5 cycles of 1min, at near 0°C temperature), n = 3, mean±SD.</p

Change of activities of coagulation factor V and VIII under mpHHP treatments (5 cycles of 1 min) with escalated pressure (≥ 300MPa), n = 3.

<p>Change of activities of coagulation factor V and VIII under mpHHP treatments (5 cycles of 1 min) with escalated pressure (≥ 300MPa), n = 3.</p

Activities of coagulation factors after optimized HHP treatment (200/250 Mpa, 5 cycles of 1min, at near 0°C temperature), n = 3.

<p>Activities of coagulation factors after optimized HHP treatment (200/250 Mpa, 5 cycles of 1min, at near 0°C temperature), n = 3.</p