Browsing by Subject "nanostructures"

Now showing 1 - 3 of 3
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    Molecular Dynamics Simulation of Electrical Resistivity in Sintering Process of Nanoparticle Silver Inks
    (Elsevier, 2016-12) Zhang, Yi; Wu, Linmin; Guo, Xingye; Jung, Yeon-Gil; Zhang, Jing; Department of Mechanical Engineering, School of Engineering and Technology
    A molecular dynamics (MD) model is developed to simulate low temperature sintering of silver nanoparticles and resultant resistivity. Due to the high surface to volume ratio, nanoparticle silver inks can sinter at low thermal curing temperatures, which are used in intense pulsed light (IPL) sintering process. In this study, the configurational change of nanoparticle silver during sintering is studied using the MD model. Then the resultant electric resistivity is calculated using the Reimann-Weber formula. The simulation results show that the resistivity decreases rapidly in the initial sintering stage, due to the fast neck formation and growth. Additionally, the predicted temperature-dependent resistivity evolutions are in good agreement with both experimental measurements and analytical sintering model, indicating that the resistivity decreases with increasing sintering temperature. The model provides a design tool for optimizing IPL process.
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    Ultrathin Plasmonic Tungsten Oxide Quantum Wells with Controllable Free Carrier Densities
    (ACS, 2020-03) Prusty, Gyanaranjan; Lee, Jacob T.; Seifert, Soenke; Muhoberac, Barry B.; Sardar, Rajesh; Chemistry and Chemical Biology, School of Science
    Localized surface plasmon resonances (LSPR) of nanostructures can be tuned by controlling their morphology, local dielectric environment, and free carrier concentration. We report the colloidal synthesis of an ∼3 tungsten–oxygen (W-O) layer thick (∼1 nm), two-dimensional (2D) WO3-x nanoplatelets (NPLs) (x ≈ 0.55–1.03), which display tunable near-infrared LSPR properties and additionally high free electron density (Ne) that arises predominantly from the large shape factor of 2D NPLs. Importantly, the W to O composition ratios inferred from their LSPR measurements show much higher percentage of oxygen vacancies than those determined by X-ray diffraction analysis, suggesting that the aspect ratio of ultrathin WO3-x NPLs is the key to producing an unprecedentedly large Ne, although synthesis temperature is also an independent factor. We find that NPL formation is kinetically controlled, whereas thermodynamic parameter manipulation leads to Ne values as high as 4.13 × 1022 cm–3, which is close to that of plasmonic noble metals, and thus our oxide-based nanostructures can be considered as quasi-metallic. The unique structural properties of 2D nanomaterials along with the high Ne of WO3-x NPLs provide an attractive alternative to plasmonic noble metal nanostructures for various plasmon-driven energy conversions and design of photochromic nanodevices.
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    Unique Design of CuInSe2 Nanocrystal decorated Gold Nanoprism Hybrid Conjugates for Advanced Photocatalytic Application
    (Office of the Vice Chancellor for Research, 2015-04-17) Lawrence, Katie; Jana, Atanu; Liyanage, Thakshila; Sardar, Rajesh
    We present CuInSe2 nanocrystal decorated gold nanoprism hybrid conjugates with advanced photocatalytic ability in order to offer a unique and environmentally sound solution to the current obstacles faced by photovoltaic device materials currently used. A search for clean and abundant energy sources is a major concern for the environmentally conscious scientist. Photocatalytic reactions can harness this energy and use it for a variety of applications including oxidation of organic contaminants, self-cleaning glass, conversion to water as hydrogen glass, and decomposition of crude oil. However solar absorption in these devices is lacking the efficiency needed to be cost effective. Choice of device material is pivotal in overcoming this large hurdle. Materials such as TiO2, the most commonly used semiconductor photocatalyst, for example only absorbs light in the ultraviolet region which accounts for less than 5% of total solar radiation. Hybrid conjugates, or nanomaterials combining semiconductor and metal materials, are a fast growing alternative to this problem. By incorporating localized surface plasmon resonance (LSPR) properties of the metal nanostructures with controllable band gaps of the semiconductor nanocrystals, the material can shift to the visible and near-infrared spectra thus allowing for greater solar absorbance. However, to the best of our knowledge, no reports are available in which plasmonic coupling occurs between a LSPR active metal nanostructures and the tailoring of the semiconductor nanocrystals’ band gap by a non-toxic, low temperature synthesis. Hybrid conjugates between LSPR active metal nanostructures and semiconductor nanostructures have been reported but suffer from cost effectiveness and often use environmentally unfriendly chemicals. We believe our unique hybrid nanomaterial will allow for further tuning of the LSPR peak position in order to extend light absorption to a more optimal window and further excite electron-hole pairs in order to provide the most photocatalytic activity to date while providing an environmentally friendly and cost-effective approach. This work has major implications in clean energy and more specifically the advancement of photocatalytic applications.