Measurement of Scattering and Absorption Cross Sections of Dyed Microspheres.

IF 1.5 4区 工程技术
Adolfas K Gaigalas, Steven Choquette, Yu-Zhong Zhang
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引用次数: 9

Abstract

Measurements of absorbance and fluorescence emission were carried out on aqueous suspensions of polystyrene (PS) microspheres with a diameter of 2.5 µm using a spectrophotometer with an integrating sphere detector. The apparatus and the principles of measurements were described in our earlier publications. Microspheres with and without green BODIPY(@) dye were measured. Placing the suspension inside an integrating sphere (IS) detector of the spectrophotometer yielded (after a correction for fluorescence emission) the absorbance (called A in the text) due to absorption by BODIPY(@) dye inside the microsphere. An estimate of the absorbance due to scattering alone was obtained by subtracting the corrected BODIPY(@) dye absorbance (A) from the measured absorbance of a suspension placed outside the IS detector (called A1 in the text). The absorption of the BODIPY(@) dye inside the microsphere was analyzed using an imaginary index of refraction parameterized with three Gaussian-Lorentz functions. The Kramer-Kronig relation was used to estimate the contribution of the BODIPY(@) dye to the real part of the microsphere index of refraction. The complex index of refraction, obtained from the analysis of A, was used to analyze the absorbance due to scattering ((A1 - A) in the text). In practice, the analysis of the scattering absorbance, A1-A, and the absorbance, A, was carried out in an iterative manner. It was assumed that A depended primarily on the imaginary part of the microsphere index of refraction with the other parameters playing a secondary role. Therefore A was first analyzed using values of the other parameters obtained from a fit to the absorbance due to scattering, A1-A, with the imaginary part neglected. The imaginary part obtained from the analysis of A was then used to reanalyze A1-A, and obtain better estimates of the other parameters. After a few iterations, consistent estimates were obtained of the scattering and absorption cross sections in the wavelength region 300 nm to 800 nm.

Abstract Image

Abstract Image

Abstract Image

染色微球散射和吸收截面的测量。
采用带积分球检测器的分光光度计对直径为2.5µm的聚苯乙烯(PS)微球水溶液悬浮液的吸光度和荧光发射进行了测量。仪器和测量原理在我们以前的出版物中有描述。测定了微球加入和不加入绿色BODIPY(@)染料的情况。将悬浮液置于分光光度计的积分球(IS)检测器中(经过荧光发射校正后),由于微球内BODIPY(@)染料的吸收,产生了吸光度(在文中称为a)。通过从放置在IS检测器外的悬浮液(文中称为A1)的测量吸光度中减去校正的BODIPY(@)染料吸光度(A),可以获得单独散射引起的吸光度估计值。利用用三个高斯-洛伦兹函数参数化的虚折射率分析了微球内BODIPY(@)染料的吸收。利用Kramer-Kronig关系估计了BODIPY(@)染料对微球折射率实部的贡献。用分析A得到的复折射率来分析散射引起的吸光度(文中为(A1 - A))。在实际应用中,对散射吸光度A1-A和吸光度A进行了迭代分析。假设A主要取决于微球折射率的虚部,其他参数起次要作用。因此,首先使用与散射吸光度拟合得到的其他参数值A1-A来分析A,忽略虚数部分。然后用分析A得到的虚部重新分析A1-A,得到其他参数的更好估计。经过几次迭代,得到了300 ~ 800 nm波长范围内的散射和吸收截面的一致估计。
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来源期刊
自引率
33.30%
发文量
10
期刊介绍: The Journal of Research of the National Institute of Standards and Technology is the flagship publication of the National Institute of Standards and Technology. It has been published under various titles and forms since 1904, with its roots as Scientific Papers issued as the Bulletin of the Bureau of Standards. In 1928, the Scientific Papers were combined with Technologic Papers, which reported results of investigations of material and methods of testing. This new publication was titled the Bureau of Standards Journal of Research. The Journal of Research of NIST reports NIST research and development in metrology and related fields of physical science, engineering, applied mathematics, statistics, biotechnology, information technology.
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