Absorption measurements by laser calorimetry

AbstractLaser heating of gold nanospheres (GNS) is increasingly prevalent in biomedical applications due to tunable optical properties that determine heating efficiency. Although many geometric parameters (i.e. size, morphology) can affect optical properties of individual GNS and their heating, no specific studies of how GNS aggregation affects heating have been carried out. We posit here that aggregation, which can occur within some biological systems, will significantly impact the optical and therefore heating properties of GNS. To address this, we employed discrete dipole approximation (DDA) simulations, Ultraviolet–Visible spectroscopy (UV–Vis) and laser calorimetry on GNS primary particles with diameters (5, 16, 30 nm) and their aggregates that contain 2 to 30 GNS particles. DDA shows that aggregation can reduce the extinction cross-section on a per particle basis by 17–28%. Experimental measurement by UV–Vis and laser calorimetry on aggregates also show up to a 25% reduction in extinction coefficient and significantly lower heating (~ 10%) compared to dispersed GNS. In addition, comparison of select aggregates shows even larger extinction cross section drops in sparse vs. dense aggregates. This work shows that GNS aggregation can change optical properties and reduce heating and provides a new framework for exploring this effect during laser heating of nanomaterial solutions.

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Assessment of critical warming and cooling rates of low concentration cryoprotectants via ultra-rapid laser calorimetry and liquid nitrogen quenching

Cryobiology ◽

10.1016/j.cryobiol.2020.10.076 ◽

2020 ◽

Vol 97 ◽

pp. 267-268

Author(s):

Joseph Kangas ◽

Li Zhan ◽

Yilin Liu ◽

Kanav Khosla ◽

John Bischof

Keyword(s):

Liquid Nitrogen ◽

Cooling Rates ◽

Low Concentration ◽

Laser Calorimetry

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Solid Parahydrogen Thickness Revisited

Applied Spectroscopy ◽

10.1177/0003702819861581 ◽

2019 ◽

Vol 73 (12) ◽

pp. 1403-1408 ◽

Cited By ~ 6

Author(s):

Mario E. Fajardo

Keyword(s):

Systematic Error ◽

Absorption Spectroscopy ◽

Ir Absorption ◽

Spectroscopy Data ◽

Previous Approach ◽

Polarization Effects ◽

Peak Intensity ◽

Absorption Measurements

We report updated infrared (IR) absorption measurements on vapor-deposited cryogenic parahydrogen (pH2) solids that indicate a ≈10% systematic error in our previous approach for determining a pH2 solid's thickness (S. Tam and M.E. Fajardo. Appl. Spectrosc. 2001. 55(12): 1634-1644). We provide corrected values for the integrated absorption intensities of the Q1(0)+S0(0) and S1(0)+S0(0) bands calculated over the 4495–4520 cm−1 and 4825–4855 cm−1 regions, respectively. New polarized IR absorption spectroscopy data demonstrate the insensitivity to polarization effects of the peak intensity of the QR(0) phonon sideband near 4228 cm−1. This feature provides an even quicker way for determining the thickness of a pH2 solid than via the integrated absorptions.

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