Heterogeneous stacking of nanodot monolayers by dry pick-and-place transfer and its applications in quantum dot light-emitting diodes

Layered assembly structures composed of nanomaterials, such as nanocrystals, have attracted considerable attention as promising candidates for new functional devices whose optical, electromagnetic and electronic behaviours are determined by the spatial arrangement of component elements. However, difficulties in handling each constituent layer in a materialspecific manner limit the 3D integration of disparate nanomaterials into the appropriate heterogeneous electronics. Here we report a pick-and-place transfer method that enables the transfer of large-area nanodot assemblies. This solvent-free transfer utilizes a lifting layer and allows for the reliable transfer of a quantum dot (QD) monolayer, enabling layer-by-layer design. With the controlled multistacking of different bandgap QD layers, we are able to probe the interlayer energy transfer among different QD monolayers. By controlling the emission spectrum through such designed monolayer stacking, we have achieved white emission with stable optoelectronic properties, the closest to pure white among the QD lightemitting diodes reported so far. (c) 2013 Macmillan Publishers Limited. All rights reserved.402

A Clinical Trial to Evaluate the Efficacy and Safety of 3D Printed Bioceramic Implants for the Reconstruction of Zygomatic Bone Defects

The purpose of this study was to evaluate the clinical efficacy and safety of patient-specific additive-manufactured CaOSiO2-P2O5-B2O3 glass-ceramic (BGS-7) implants for reconstructing zygomatic bone defects at a 6-month follow-up. A prospective, single-arm, single-center, clinical trial was performed on patients with obvious zygoma defects who needed and wanted reconstruction. The primary outcome variable was a bone fusion between the implant and the bone evaluated by computed tomography (CT) at 6 months post surgery. Secondary outcomes, including implant immobilization, satisfaction assessment, osteolysis, subsidence of the BGS-7 implant, and safety, were assessed. A total of eight patients were enrolled in the study. Two patients underwent simultaneous reconstruction of the left and right malar defects using a BGS-7 3D printed implant. Cone beam CT analysis showed that bone fusion at 6 months after surgery was 100%. We observed that the average fusion rate was 76.97%. Osteolysis around 3D printed BGS-7 implants was not observed. The mean distance displacement of all 10 implants was 0.4149 mm. Our study showed no adverse event in any of the cases. The visual analog scale score for satisfaction was 9. All patients who enrolled in this trial were aesthetically and functionally satisfied with the surgical results. In conclusion, this study demonstrates the safety and promising value of patient-specific 3D printed BGS-7 implants as a novel facial bone reconstruction method

Erratum: Heterogeneous stacking of nanodot monolayers by dry pick-and-place transfer and its applications in quantum dot light-emitting-diodes (vol 4, 2637, 2013)

Y

Control of Lateral Dimension in Metal-Catalyzed Germanium Nanowire Growth: Usage of Carbon Sheath

We report on the catalytic growth of thin carbon sheathed single crystal germanium nanowires (GeNWs), which can solve the obstacles that have disturbed a wide range of applications of GeNWs. Single crystal Ge NW core and amorphous carbon sheath are simultaneously grown via vapor–liquid–solid (VLS) process. The carbon sheath completely blocks unintentional vapor deposition on NW surface, thus ensuring highly uniform diameter, dopant distribution, and electrical conductivity along the entire NW length. Furthermore, the sheath not only inhibits metal diffusion but also improves the chemical stability of GeNWs at even high temperatures

Metastable Ge_1–<i>x</i>C_<i>x</i> Alloy Nanowires

Carbon-containing alloy materials such as Ge_1–<i>x</i>C_<i>x</i> are attractive candidates for replacing silicon (Si) in the semiconductor industry. The addition of carbon to diamond lattice not only allows control over the lattice dimensions, but also enhances the electrical properties by enabling variations in strain and compositions. However, extremely low carbon solubility in bulk germanium (Ge) and thermodynamically unfavorable Ge–C bond have hampered the production of crystalline Ge_1–<i>x</i>C_<i>x</i> alloy materials in an equilibrium growth system. Here we successfully synthesized high-quality Ge_1–<i>x</i>C_<i>x</i> alloy nanowires (NWs) by a nonequilibrium vapor–liquid–solid (VLS) method. The carbon incorporation was controlled by NW growth conditions and the position of carbon atoms in the Ge matrix (at substitutional or interstitial sites) was determined by the carbon concentration. Furthermore, the shrinking of lattice spacing caused by substitutional carbon offered the promising possibility of band gap engineering for photovoltaic and optoelectronic applications

Porous PVDF As Effective Sonic Wave Driven Nanogenerators

Piezomaterials are known to display enhanced energy conversion efficiency at nanoscale due to geometrical effect and improved mechanical properties. Although piezoelectric nanowires have been the most widely and dominantly researched structure for this application, there only exist a limited number of piezomaterials that can be easily manufactured into nanowires, thus, developing effective and reliable means of preparing nanostructures from a wide variety of piezomaterials is essential for the advancement of self-powered nanotechnology. In this study, we present nanoporous arrays of polyvinylidene fluoride (PVDF), fabricated by a lithography-free, template-assisted preparation method, as an effective alternative to nanowires for robust piezoelectric nanogenerators. We further demonstrate that our porous PVDF nanogenerators produce the rectified power density of 0.17 mW/cm³ with the piezoelectric potential and the piezoelectric current enhanced to be 5.2 times and 6 times those from bulk PVDF film nanogenerators under the same sonic-input

Large Thermoelectric Figure-of-Merits from SiGe Nanowires by Simultaneously Measuring Electrical and Thermal Transport Properties

The strongly correlated thermoelectric properties have been a major hurdle for high-performance thermoelectric energy conversion. One possible approach to avoid such correlation is to suppress phonon transport by scattering at the surface of confined nanowire structures. However, phonon characteristic lengths are broad in crystalline solids, which makes nanowires insufficient to fully suppress heat transport. Here, we employed Si–Ge alloy as well as nanowire structures to maximize the depletion of heat-carrying phonons. This results in a thermal conductivity as low as ∼1.2 W/m-K at 450 K, showing a large thermoelectric figure-of-merit (ZT) of ∼0.46 compared with those of SiGe bulks and even ZT over 2 at 800 K theoretically. All thermoelectric properties were “simultaneously” measured from the same nanowires to facilitate accurate ZT measurements. The surface-boundary scattering is prominent when the nanowire diameter is over ∼100 nm, whereas alloying plays a more important role in suppressing phonon transport for smaller ones