4,218 publications from this institution
Rotational energy is abundant and widely available in our living environment. Harvesting ambient rotational energy has attracted great attention. In this work, we report a single-electrode-based rotating triboelectric nanogenerator (SR-TENG) for converting rotational energy into electric energy. The unique advantage of introducing the single-electrode TENG is to overcome the difficulty in making the connection in harvesting rotational energy such as from a moving and rotating tire/wheel. The fabricated device consists of a rotary acrylic disc with polytetrafluoroethylene (PTFE) blades and an Al electrode fixed on the base. The systematical experiments and theoretical simulations indicate that the asymmetric SR-TENGs exhibit much better output performances than those of the symmetric TENGs at the same rotation rates. The asymmetric SR-TENG with seven PTFE units at the rotation rate of 800 r/min can deliver a maximal output voltage of 55 V and a corresponding output power of 30 μW on a load of 100 MΩ, which can directly light up tens of red light-emitting diodes. The SR-TENG has been utilized to harvest mechanical energy from rotational motion of a bicycle wheel. Furthermore, we demonstrated that the SR-TENG can be applied to scavenge wind energy and as a self-powered wind speed sensor with a sensitivity of about 0.83 V/(m/s). This study further expands the operation principle of a single-electrode-based TENG and many potential applications of TENGs for scavenging ambient rotational energy and as a self-powered environment monitoring sensor.
We present the first piezoelectrically modulated resistive switching device based on piezotronic ZnO nanowire (NW), through which the write/read access of the memory cell is programmed via electromechanical modulation. Adjusted by the strain-induced polarization charges created at the semiconductor/metal interface under externally applied deformation by the piezoelectric effect, the resistive switching characteristics of the cell can be modulated in a controlled manner, and the logic levels of the strain stored in the cell can be recorded and read out, which has the potential for integrating with NEMS technology to achieve micro/nanosystems capable for intelligent and self-sufficient multidimensional operations.
Effective doses were calculated from the delivery of , , and conventional and intensity‐modulated radiation therapy (IMRT) prostate treatment plans. ICRP‐60 tissue weighting factors were used for the calculations. Photon doses were measured in phantom for all beam energies. Neutron spectra were measured for and and ICRP‐74 quality conversion factors used to calculate ambient dose equivalents. The ambient dose equivalents were corrected for each tissue using neutron depth dose data from the literature. The depth corrected neutron doses were then used as a measure of the neutron component of the ICRP protection quantity, organ equivalent dose. IMRT resulted in an increased photon dose to many organs. However, the IMRT treatments resulted in an overall decrease in effective dose compared to conventional radiotherapy. This decrease correlates to the ability of an intensity‐modulated field to minimize dose to critical normal structures in close proximity to the treatment volume. In a comparison of the three beam energies used for the IMRT treatments, resulted in the lowest effective dose, while resulted in the highest effective dose. This is attributed to the large neutron contribution for compared to no neutron contribution for .
Piezoelectricity, a phenomenon known for centuries, is an effect that is about the production of electrical potential in a substance as the pressure on it changes. Wurtzite structures such as ZnO, GaN, InN and ZnS, due to the polarization of ions in a crystal that has non-central symmetry, a piezoelectric potential (piezopotential) is created in the crystal by applying a stress. The effect of piezopotential to the transport behavior of charge carriers is significant due to their multiple functionalities of piezoelectricity, semiconductor and photon excitation. By utilizing the advantages offered by these properties, a few new fields have been created. Electronics fabricated by using inner-crystal piezopotential as a “gate” voltage to tune/control the charge transport behavior is named piezotronics, with applications in strain/force/pressure triggered/controlled electronic devices, sensors and logic units. Piezo-phototronic effect is a result of three-way coupling among piezoelectricity, photonic excitation and semiconductor transport, which allows tuning and controlling of electro-optical processes by strain induced piezopotential. The objective of this talk is to introduce the fundamentals of piezotronics and piezo-phototronics and to give an updated progress about their applications in energy science (LED, solar) and sensors (photon detector and human-CMOS interfacing).
Variations on thermal stabilities were studied when the ligands of coordination compounds of manganese (II) acetylacetonate (Mn(acac)2) and iron (III) acetylacetonate (Fe(acac)3) were substituted with benzoylacetonate (bzac). By replacing the acetylacetonate ligand with the benzoylacetonate ligand, the difference of onset thermal decomposition temperatures can be brought within 15° between Fe(bzac)3 and Mn(bzac)2, which shows the feasibility of tuning thermal stability to produce more suitable molecular precursors for the materials syntheses. The closeness in the decomposition temperatures of these two compounds enables the synthesis of high-quality manganese ferrite, MnFe2O4, nanocrystals with tunable sizes from 3 to 12 nm through a combination of a non-hydrolytic reaction and a seed-mediated growth process. Studies on magnetic properties clearly indicate that superparamagnetic properties such as blocking temperature (TB) and coercivity (HC) are strongly dependent on the size of these MnFe2O4 nanocrystals, which is consistent with the Stoner−Wohlfarth single domain theory.
A fundamental challenge in the development of nanotechnology is the assembly of nanoscale building blocks into functional nanostructured materials. A symposium entitled “Assembly at the Nanoscale – Toward Functional Nanostructured Materials” was organized by Cengiz S. Ozkan (University of California, Riverside), Federico Rosei (University of Quebec, Canada), Gregory P. Lopinski (National Research Council, Canada), and Zhong L. Wang (Georgia Institute of Technology), and took place at the 2005 Materials Research Society (MRS) Fall Meeting in Boston, USA. The aim of the symposium was to bring together researchers from chemistry, physics, biology, surface science, and materials science to advance the progress being seen in the engineering of nanoscale assemblies. The scope of the symposium ranged from discussing the properties and characterization of novel nanostructured materials to developing functional multidimensional nanostructures, the applicability of which might range from the life sciences to device engineering. Topics of interest for the symposium were: Surface science studies of 1D and 2D supramolecular assemblies; Properties and applications of self-assembled 3D structures and nanostructures: photonic-bandgap materials, sensors, and nanocomposites; Novel fabrication methodologies: self-assembly strategies, biomimetics, and predictive approaches; Fundamental problems in quantum dots: growth (by self-assembly), physics, top-down fabrication (e.g., lithography, as well as other less conventional approaches); Unconventional approaches to patterning: soft lithography, embossing, dip-pen nanolithography, scanning probe lithography, and template-directed patterning; Organic/inorganic interfaces for molecular and nanoelectronic applications (see Figure 11 ); Nanoscale building blocks (see Figure 22 ) synthesized with colloidal particles, nanowires, nanotubes, quantum dots, block copolymers, and DNA. Electrical characterization data from a resonant tunneling diode based on conjugates of SWNT–ssDNA–SWNT (SWNT=single-walled carbon nanotube). The graph shows the measurement of negative differential resistance. The sketched model of the conjugate shows 9 bases of ssDNA between two conductive SWNTs used in the transfer function calculation. (Image provided by C S. Ozkan.) Novel nanostructures of ZnO synthesized by a solid–vapor-phase process. (Image provided by Z. L. Wang and R. S. Yang.) Overall, we received over 250 contributions for this symposium, and in addition, over a dozen invited talks were delivered by experts from around the world. This special section in this issue of Small includes papers authored by some of the invited speakers and the symposium organizers. The section includes work that is being carried out at the forefront of many of the fields that are listed above. We anticipate that this special issue, together with the proceedings published by the MRS, will provide a comprehensive coverage of current research in nanoscale assembly.
