Systems and methods for determining nanoparticle dimensions
Inventors
Assignees
University of South Florida • University of South Florida St Petersburg
Publication Number
US-8854621-B1
Publication Date
2014-10-07
Expiration Date
2033-08-27
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Abstract
In one embodiment, the dimensions of nanoparticles are determined by focusing light on a sample of nanoparticles suspended in a solution, collecting light scattered by the nanoparticles, measuring translational and rotational decay rates of the collected light, calculating a ratio of the rotational decay rate to translational decay rate, and estimating a first dimension of the nanoparticles based upon the decay rate ratio.
Core Innovation
The invention provides a system and method for determining the dimensions of nanoparticles by measuring both translational and rotational decay rates of scattered light. This process includes focusing polarized light on a sample of nanoparticles suspended in a solution, collecting the light scattered by the nanoparticles, and then using a custom-designed depolarized dynamic light scattering (DDLS) system with time-tagged time-resolved (TTTR) photon counting. The collected data allows direct measurement of decay rates related to nanoparticle diffusion, and these measurements are used to predict nanoparticle dimensions such as length and aspect ratio.
The problem addressed is the lack of reliable, in-situ characterization methods for nanoparticle dimensions, especially for nanorods, where conventional optical absorption methods do not provide a direct or unambiguous measure of their physical properties due to the complex relationship between surface plasmon resonance peaks and particle shape. Standard techniques like electron microscopy cannot be performed in solution and do not yield dynamic information such as growth kinetics or surfactant adsorption status. Thus, there is a need for an alternative, solution-based, and robust approach to accurately determine nanoparticle dimensions and distributions.
The core innovation lies in combining measurements of both translational and rotational decay rates to calculate their ratio, which is highly sensitive to one dimension—typically the length for nanorods—while being largely insensitive to other dimensions like diameter. This ratio, along with theoretical diffusion models, allows for accurate estimation of physical lengths of nanoparticles, with subsequent estimation of aspect ratios or widths as secondary parameters. The system also includes methods to preprocess raw photon count data to remove artifacts such as photon bursts, improving reliability of the resulting dimension estimations.
Claims Coverage
There are two main independent claims in the patent: one covering a method for determining dimensions of nanoparticles and one covering a system for performing this determination. The inventive features relate to the optical measurement methodology, data analysis, and implementation in hardware and software.
Method for determining nanoparticle dimensions based on decay rate ratio
A method comprising: 1. Focusing light on a sample of nanoparticles suspended in a solution. 2. Collecting light scattered by the nanoparticles. 3. Measuring translational and rotational decay rates of the collected light. 4. Calculating a ratio of the rotational decay rate to translational decay rate. 5. Estimating a first dimension of the nanoparticles based upon the decay rate ratio. The method further covers: - Measuring the decay rates by identifying bright spots and their decay in the scattered light. - Dividing the rotational decay rate by the translational decay rate to obtain Γrot/Γtr. - Calculating the average length of the nanoparticles using the relation: L = q−1√{square root over (54(Γrot/Γtr)−1H(AR))}{square root over (54(Γrot/Γtr)−1H(AR))}, where q is the scattering vector and H(AR) is a function of aspect ratio. - Estimating a second dimension (e.g., aspect ratio) based upon the first dimension.
System for determining nanoparticle dimensions using decay rate analysis
A system comprising: - A computing device (with processing device and memory) including a nanoparticle dimension determination system configured to: - Receive scattered light data collected by focusing light on nanoparticles in solution. - Measure translational and rotational decay rates of the scattered light data. - Calculate a ratio of rotational to translational decay rate. - Estimate a first dimension (e.g., length) based on this ratio. The system may further include: - Logic for estimating second dimension based on first. - Components such as a light source, polarization devices for increasing polarization purity and selecting scattered light polarization, a sample chamber, photon detector, and related optical elements. - Implementation as a non-transitory computer-readable medium storing logic for all the above analysis.
In summary, the inventive features cover both a method and a system for determining dimensions of nanoparticles in solution by analyzing translational and rotational decay rate ratios of scattered light, with specific formulas and processing steps for accurate dimensional estimation.
Stated Advantages
Enables direct and robust estimation of nanoparticle length from solution-phase measurements without reliance on complicated absorption spectra interpretation.
Allows characterization of nanoparticles in their natural solution environment, providing information unavailable from electron microscopy such as in-situ dimensions and potential dynamic changes.
Reduces artifacts in data analysis by preprocessing photon count history to remove events like photon bursts from aggregates or air bubbles, improving measurement reliability.
Provides a more straightforward linkage between measured decay rate ratios and particle length, reducing the impact of model-specific uncertainties in estimating aspect ratios compared to traditional analytical methods.
Documented Applications
Evaluation of gold nanorod dimensions for use in developing novel surface coatings, electrical and magnetic nanowires, and optical metamaterials for long-distance imaging with near-field resolution.
Characterization of nanorods for biomedical applications, including situations where near-infrared absorption and enhanced cellular uptake of anisotropic nanoparticles are of interest.
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