Chemistry

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Browsing Chemistry by Subject "aluminum"

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    Aluminum Nanocrystals
    (American Chemical Society, 2015) McClain, Michael J.; Schlather, Andrea E.; Ringe, Emilie; King, Nicholas S.; Liu, Lifei; Manjavacas, Alejandro; Knight, Mark W.; Kumar, Ish; Whitmire, Kenton; Everitt, Henry O.; Nordlander, Peter; Halas, Naomi J.; Laboratory for Nanophotonics
    We demonstrate the facile synthesis of high purity aluminum nanocrystals over a range of controlled sizes from 70 to 220 nm diameter with size control achieved through a simple modification of solvent ratios in the reaction solution. The monodisperse, icosahedral, and trigonal bipyramidal nanocrystals are air-stable for weeks, due to the formation of a 2-4 nm thick passivating oxide layer on their surfaces. We show that the nanocrystals support size-dependent ultraviolet and visible plasmon modes, providing a far more sustainable alternative to gold and silver nanoparticles currently in widespread use.
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    Polydopamine-Stabilized Aluminum Nanocrystals: Aqueous Stability and Benzo[a]pyrene Detection
    (American Chemical Society, 2019) Renard, David; Tian, Shu; Ahmadivand, Arash; DeSantis, Christopher J.; Clark, Benjamin D.; Nordlander, Peter; Halas, Naomi J.; Laboratory for Nanophotonics
    Aluminum nanocrystals have emerged as an earth-abundant material for plasmonics applications. Al nanocrystals readily oxidize in aqueous-based solutions, however, transforming into highly stratified γ-AlOOH nanoparticles with a 700% increase in surface area in a matter of minutes. Here we show that by functionalizing Al nanocrystals with the bioinspired polymer polydopamine, their stability in aqueous media is dramatically increased, maintaining their integrity in aqueous solution for over 2 weeks with no discernible structural changes. Polydopamine functionalization also provides a molecular capture layer that enables the capture of polycyclic aromatic hydrocarbon pollutants in H2O samples and their detection by surface-enhanced Raman spectroscopy, when polydopamine-stabilized Al nanocrystal aggregates are used as substrates. This approach was used to detect a prime carcinogenic H2O pollutant, benzo[a]pyrene with a sensitivity in the sub part-per-billion range.
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    Toward a Nanophotonic Nose: A Compressive Sensing-Enhanced, Optoelectronic Mid-Infrared Spectrometer
    (American Chemical Society, 2019) Cerjan, Benjamin; Halas, Naomi J.; Laboratory for Nanophotonics
    Infrared (IR) spectroscopy has been a central tool for chemical analysis for decades, useful in a wide range of fields for the detection and quantification of molecules based on their unique vibrational resonances. Conventional IR spectroscopy relies on bulky, dispersive optics, however, making portability and miniaturization a substantial challenge. Here we demonstrate a micron-scale IR spectrometer where spectrally selective detection is performed optoelectronically based on the wavelength-dependent mid-IR photocurrent responses of an array of Al grating-based detectors fabricated on a doped Si substrate. Compressive sensing techniques extend our resolution, enabling spectral features to be identified with a remarkably small number of detectors. This work demonstrates a CMOS-compatible, readily scalable approach for the fabrication of compact, room-temperature IR spectrometers capable of use in fieldable applications.