• Using nanodiamonds as sensors just got e

    From ScienceDaily@1:317/3 to All on Wed Jan 26 21:30:44 2022
    Using nanodiamonds as sensors just got easier

    Date:
    January 26, 2022
    Source:
    University of Rochester
    Summary:
    Researchers adapt excited state lifetime thermometry to extract
    temperatures of nanoscale materials from light emitted by nitrogen
    vacancy centers in individual nanodiamonds. The approach is less
    complicated, more accurate and safer for sensitive materials or
    biological tissues than OMDR.



    FULL STORY ==========================================================================
    For centuries people have placed the highest value on diamonds that are
    not only large but flawless.


    ========================================================================== Scientists, however, have discovered exciting new applications for
    diamonds that are not only incredibly small but have a unique defect.

    In a recent paper in Applied Physics Letters, researchers at the
    University of Rochester describe a new way to measure temperature with
    these defects, called nitrogen vacancy centers, using the light they
    emit. The technique, adapted for single nanodiamonds by Andrea Pickel, assistant professor of mechanical engineering, and Dinesh Bommidi,
    a PhD student in her lab, allowed them to precisely measure, for the
    first time, the duration of these light emissions, or "excited state lifetimes," at a broad range of temperatures.

    The discovery earned the paper recognition as an American Institute of
    Physics "Scilight," a showcase of what AIP considers the most interesting research across the physical sciences.

    The Rochester method gives researchers a less complicated, more accurate
    tool for using nitrogen vacancy centers to measure the temperature
    of nanoscale- sized materials. The approach is also safe for imaging
    sensitive nanoscale materials or biological tissues and could have
    applications in quantum information processing.

    For example, Pickel says, the technique could help define and measure the precise optimal temperatures needed to switch the resistivity of materials
    in nanoscale-sized phase change memory devices as part of the ongoing
    quest to store ever larger amounts of data in ever smaller devices.



    ========================================================================== "These excited state lifetime measurements are really helpful for
    measuring temperature changes that take place not only over small length scales, but also on fast time scales," Pickel says. "It turns out these lifetimes are quite fast -- only about 25 to 30 nanoseconds at room temperature, and even faster at higher temperatures." New technique
    offers multiple advantages over standard approach Nitrogen vacancy
    centers are often created by bombarding commercial diamonds with ions,
    then milling them down into the nanoscale diamond particles used by researchers. In a nitrogen vacancy center, one of the carbon atoms
    is replaced with a nitrogen atom, and the adjoining nitrogen atom is
    missing. "It turns out, these nitrogen vacancy centers are fluorescent,
    so if you send light in - - from a laser, for example -- you can also
    get light out of them," Pickel says.

    To date, most research groups have used a technique called optically
    detected magnetic resonance (ODMR) to measure temperature using
    nitrogen vacancy centers. However, the method has several drawbacks,
    Pickel says. OMDR requires placing a microwave antenna near the sample
    to do the measurements. That can be a complicated setup. The antenna
    can also cause heating that could harm sensitive materials or biological samples. Moreover, the microwave signal can be lost altogether at higher temperatures.

    Instead, Pickel and Bommidi adapted an existing technique called excited
    state lifetime thermometry and applied it to nitrogen vacancy centers
    in single nanodiamonds for the first time.



    ==========================================================================
    The nanodiamonds, scattered on the surface of a material to be tested,
    are located using atomic force microscopy. The researchers developed a
    way to use the microscope probe tip to then move individual nanodiamonds
    to desired locations.

    "If you know there's a really critical location where you want to measure
    the temperature on a device or sample, this gives us a way to move the nanodiamond sensor to exactly that spot -- almost like using a putter
    in a little nanodiamond golf game," Pickel says.

    The researchers then excite the nitrogen vacancy centers with green
    laser pulses. This sends electrons into a higher energy state. When the
    laser shuts off and the electrons return to a normal state, photons
    are emitted. The duration of this emission is a precise indicator of temperature.

    Because the nanodiamonds are the same temperature as the material they
    are placed on, the readings are accurate for the material as well,
    Pickel says.

    "We are excited about this because it is all optical; we don't
    need to have a microwave antenna," Pickel says. "And even when
    we increase the temperature, we retain access to our measurement
    signal, so we can make temperature measurements at pretty fast
    time scales. That's important at the nanoscale, because when you
    have really small samples, they can change temperatures really fast." ========================================================================== Story Source: Materials provided by University_of_Rochester. Original
    written by Bob Marcotte. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Dinesh K. Bommidi, Andrea D. Pickel. Temperature-dependent
    excited state
    lifetimes of nitrogen vacancy centers in individual
    nanodiamonds. Applied Physics Letters, 2021; 119 (25): 254103 DOI:
    10.1063/5.0072357 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/01/220126144211.htm

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