scholarly journals Combined extinction and absorption UV–vis spectroscopy reveals shape imperfections of metallic nanoparticles

2020 ◽  
Author(s):  
Johan Grand ◽  
Baptiste Auguié ◽  
Eric Le Ru
Keyword(s):  
Absorption Spectrum ◽  
Plasmon Resonance ◽  
Metallic Nanoparticles ◽  
Extinction Spectrum ◽  
Mie Theory ◽  
Integrating Sphere ◽  
Surface Integral ◽  
Modeling Tools ◽  
Vis Spectroscopy ◽  
Silver Nanospheres

Copyright © 2019 American Chemical Society. Metallic nanoparticle solutions are routinely characterized by measuring their extinction spectrum (with UV-vis spectroscopy). Theoretical predictions such as Mie theory for spheres can then be used to infer important properties, such as particle size and concentration. Here we highlight the benefits of measuring not only the extinction (the sum of absorption and scattering) but also the absorption spectrum (which excludes scattering) for routine characterization of metallic nanoparticles. We use an integrating sphere-based method to measure the combined extinction-absorption spectra of silver nanospheres and nanocubes. Using a suite of electromagnetic modeling tools (Mie theory, T-matrix, surface integral equation methods), we show that the absorption spectrum, in contrast to extinction, is particularly sensitive to shape imperfections such as roughness, faceting, or edge rounding. We study in detail the canonical case of silver nanospheres, where small discrepancies between experimental and calculated extinction spectra are still common and often overlooked. We show that this mismatch between theory and experiment becomes much more important when considering the absorption spectrum and can no longer be dismissed as experimental imperfections. We focus in particular on the quadrupolar localized plasmon resonance of silver nanospheres, which is predicted to be very prominent in the absorption spectrum but is not observed in our experiments. We consider and discuss a number of possible explanations to account for this discrepancy, including changes in the dielectric function of Ag, size polydispersity, and shape imperfections such as elongation, faceting, and roughness. We are able to pinpoint faceting and roughness as the likely causes for the observed discrepancy. A similar analysis is carried out on silver nanocubes to demonstrate the generality of this conclusion. We conclude that the absorption spectrum is in general much more sensitive to the fine details of a nanoparticle geometry, compared to the extinction spectrum. The ratio of extinction to absorption also provides a sensitive indicator of size for many types of nanoparticles, much more reliably than any observed plasmon resonance shifts. Overall, this work demonstrates that combined absorption-extinction measurements provide a much richer characterization tool for metallic nanoparticles.

scholarly journals Combined extinction and absorption UV–vis spectroscopy reveals shape imperfections of metallic nanoparticles

2020 ◽  
Author(s):  
Johan Grand ◽  
Baptiste Auguié ◽  
Eric Le Ru
Keyword(s):  
Absorption Spectrum ◽  
Plasmon Resonance ◽  
Metallic Nanoparticles ◽  
Extinction Spectrum ◽  
Mie Theory ◽  
Integrating Sphere ◽  
Surface Integral ◽  
Modeling Tools ◽  
Vis Spectroscopy ◽  
Silver Nanospheres

Copyright © 2019 American Chemical Society. Metallic nanoparticle solutions are routinely characterized by measuring their extinction spectrum (with UV-vis spectroscopy). Theoretical predictions such as Mie theory for spheres can then be used to infer important properties, such as particle size and concentration. Here we highlight the benefits of measuring not only the extinction (the sum of absorption and scattering) but also the absorption spectrum (which excludes scattering) for routine characterization of metallic nanoparticles. We use an integrating sphere-based method to measure the combined extinction-absorption spectra of silver nanospheres and nanocubes. Using a suite of electromagnetic modeling tools (Mie theory, T-matrix, surface integral equation methods), we show that the absorption spectrum, in contrast to extinction, is particularly sensitive to shape imperfections such as roughness, faceting, or edge rounding. We study in detail the canonical case of silver nanospheres, where small discrepancies between experimental and calculated extinction spectra are still common and often overlooked. We show that this mismatch between theory and experiment becomes much more important when considering the absorption spectrum and can no longer be dismissed as experimental imperfections. We focus in particular on the quadrupolar localized plasmon resonance of silver nanospheres, which is predicted to be very prominent in the absorption spectrum but is not observed in our experiments. We consider and discuss a number of possible explanations to account for this discrepancy, including changes in the dielectric function of Ag, size polydispersity, and shape imperfections such as elongation, faceting, and roughness. We are able to pinpoint faceting and roughness as the likely causes for the observed discrepancy. A similar analysis is carried out on silver nanocubes to demonstrate the generality of this conclusion. We conclude that the absorption spectrum is in general much more sensitive to the fine details of a nanoparticle geometry, compared to the extinction spectrum. The ratio of extinction to absorption also provides a sensitive indicator of size for many types of nanoparticles, much more reliably than any observed plasmon resonance shifts. Overall, this work demonstrates that combined absorption-extinction measurements provide a much richer characterization tool for metallic nanoparticles.

scholarly journals Combined extinction and absorption UV–vis spectroscopy reveals shape imperfections of metallic nanoparticles

2020 ◽  
Author(s):  
Johan Grand ◽  
Baptiste Auguié ◽  
Eric Le Ru
Keyword(s):  
Absorption Spectrum ◽  
Plasmon Resonance ◽  
Metallic Nanoparticles ◽  
Extinction Spectrum ◽  
Mie Theory ◽  
Integrating Sphere ◽  
Surface Integral ◽  
Modeling Tools ◽  
Vis Spectroscopy ◽  
Silver Nanospheres

Copyright © 2019 American Chemical Society. Metallic nanoparticle solutions are routinely characterized by measuring their extinction spectrum (with UV-vis spectroscopy). Theoretical predictions such as Mie theory for spheres can then be used to infer important properties, such as particle size and concentration. Here we highlight the benefits of measuring not only the extinction (the sum of absorption and scattering) but also the absorption spectrum (which excludes scattering) for routine characterization of metallic nanoparticles. We use an integrating sphere-based method to measure the combined extinction-absorption spectra of silver nanospheres and nanocubes. Using a suite of electromagnetic modeling tools (Mie theory, T-matrix, surface integral equation methods), we show that the absorption spectrum, in contrast to extinction, is particularly sensitive to shape imperfections such as roughness, faceting, or edge rounding. We study in detail the canonical case of silver nanospheres, where small discrepancies between experimental and calculated extinction spectra are still common and often overlooked. We show that this mismatch between theory and experiment becomes much more important when considering the absorption spectrum and can no longer be dismissed as experimental imperfections. We focus in particular on the quadrupolar localized plasmon resonance of silver nanospheres, which is predicted to be very prominent in the absorption spectrum but is not observed in our experiments. We consider and discuss a number of possible explanations to account for this discrepancy, including changes in the dielectric function of Ag, size polydispersity, and shape imperfections such as elongation, faceting, and roughness. We are able to pinpoint faceting and roughness as the likely causes for the observed discrepancy. A similar analysis is carried out on silver nanocubes to demonstrate the generality of this conclusion. We conclude that the absorption spectrum is in general much more sensitive to the fine details of a nanoparticle geometry, compared to the extinction spectrum. The ratio of extinction to absorption also provides a sensitive indicator of size for many types of nanoparticles, much more reliably than any observed plasmon resonance shifts. Overall, this work demonstrates that combined absorption-extinction measurements provide a much richer characterization tool for metallic nanoparticles.

scholarly journals Computational Modelling for the Optical Properties of Dye Molecules Adsorbed onto Metallic Nanoparticles

2021 ◽  
Author(s):  
Chhayly Tang
Keyword(s):  
Optical Properties ◽  
Shell Model ◽  
Plasmon Resonance ◽  
Metallic Nanoparticles ◽  
Maxwell's Equations ◽  
Mie Theory ◽  
Effective Medium ◽  
Dye Molecules ◽  
Effective Medium Model ◽  
Medium Model

<p><b>The study of light scattering by particles has become fundamental and applied interests in the fields of chemistry, biology, and most importantly in physics. In this context, this thesis focuses on understanding the optical properties of dye layers adsorbed onto metallic nanoparticles (NP), which is essential for interpreting the results of plasmon-dye coupling experiments. To model such a system, Mie theory is often used to solve for the exact solution to Maxwell’s equations for spherical homogeneous and isotropic coated NP. The effects of the NP’s plasmon resonances on the optical properties of the adsorbed dye layer have been predicted using an effective medium model, where the dye-layer is treated as an isotropic layer with an effective dielectric function accounting for the dye resonance. However, this isotropic shell model is inadequate as it cannot account for the dye surface concentration and the anisotropy of the optical response of the dye layer.</b></p> <p>In this thesis, we introduce anisotropic effects within Mie theory and develop microscopic models to define effective dielectric functions which explicitly include the dye-concentration effect in the shell model. Combining anisotropic Mie theory with a concentration-dependent effective shell model allows us to form new theoretical tools to model the optical properties of adsorbed dye layers on metallic NPs of spherical shape. With this new refined effective medium model, we are then able to study shell models for elongated particles beyond the quasi-static approximation. This is implemented using the finite element method (FEM) to numerically solve Maxwell’s equations. The FEM implementation is then used to investigate how the NP’s plasmon resonance can be affected by the dye’s orientation and location on the NP’s surface. We show that the orientation and location of the dye molecules on the NP determine how strongly the plasmon resonance is shifted.</p> <p>The results of this work will improve our ability to accurately model the optical properties of anisotropic molecules adsorbed on metallic NPs. This is important in a number of applications including the development of localised surface plasmon resonance (LSPR) sensing and the design of plasmonic devices.</p>

THE ABSORPTION PROPERTIES OF GOLD NANO CONJUGATED WITH PROTEINS

2020 ◽  
Vol 65 (10) ◽  
pp. 29-35
Author(s):  
Theu Luong Thi ◽  
Thi Le Anh ◽  
Huy Tran Quang ◽  
Hoc Nguyen Quang ◽  
Hoa Nguyen Minh
Keyword(s):  
Complex System ◽  
Absorption Spectrum ◽  
Metallic Nanoparticles ◽  
Biomedical Applications ◽  
Mie Theory ◽  
Core Shell ◽  
Absorption Properties ◽  
The Core ◽  
Good Agreement ◽  
Nanoparticle Complex

The absorption properties of protein-conjugated metallic nanoparticles are theoretically investigated based on the Mie theory and the core-shell model. Our numerical calculations show that this finding is in good agreement with previous experiments. We provide a better interpretation of the origin of optical peaks in the absorption spectrum of the nanoparticle complex system. Our results can be used in biomedical applications.

scholarly journals Computational Modelling for the Optical Properties of Dye Molecules Adsorbed onto Metallic Nanoparticles

2021 ◽  
Author(s):  
Chhayly Tang
Keyword(s):  
Optical Properties ◽  
Shell Model ◽  
Plasmon Resonance ◽  
Metallic Nanoparticles ◽  
Maxwell's Equations ◽  
Mie Theory ◽  
Effective Medium ◽  
Dye Molecules ◽  
Effective Medium Model ◽  
Medium Model

<p><b>The study of light scattering by particles has become fundamental and applied interests in the fields of chemistry, biology, and most importantly in physics. In this context, this thesis focuses on understanding the optical properties of dye layers adsorbed onto metallic nanoparticles (NP), which is essential for interpreting the results of plasmon-dye coupling experiments. To model such a system, Mie theory is often used to solve for the exact solution to Maxwell’s equations for spherical homogeneous and isotropic coated NP. The effects of the NP’s plasmon resonances on the optical properties of the adsorbed dye layer have been predicted using an effective medium model, where the dye-layer is treated as an isotropic layer with an effective dielectric function accounting for the dye resonance. However, this isotropic shell model is inadequate as it cannot account for the dye surface concentration and the anisotropy of the optical response of the dye layer.</b></p> <p>In this thesis, we introduce anisotropic effects within Mie theory and develop microscopic models to define effective dielectric functions which explicitly include the dye-concentration effect in the shell model. Combining anisotropic Mie theory with a concentration-dependent effective shell model allows us to form new theoretical tools to model the optical properties of adsorbed dye layers on metallic NPs of spherical shape. With this new refined effective medium model, we are then able to study shell models for elongated particles beyond the quasi-static approximation. This is implemented using the finite element method (FEM) to numerically solve Maxwell’s equations. The FEM implementation is then used to investigate how the NP’s plasmon resonance can be affected by the dye’s orientation and location on the NP’s surface. We show that the orientation and location of the dye molecules on the NP determine how strongly the plasmon resonance is shifted.</p> <p>The results of this work will improve our ability to accurately model the optical properties of anisotropic molecules adsorbed on metallic NPs. This is important in a number of applications including the development of localised surface plasmon resonance (LSPR) sensing and the design of plasmonic devices.</p>

Green synthesis of mixed metallic nanoparticles using room temperature self-assembly

2017 ◽  
Vol 13 (2) ◽  
pp. 4671-4677 ◽  
Author(s):  
A. M. Abdelghany ◽  
A.H. Oraby ◽  
Awatif A Hindi ◽  
Doaa M El-Nagar ◽  
Fathia S Alhakami
Keyword(s):  
Self Assembly ◽  
Metallic Nanoparticles ◽  
Room Temperature ◽  
Bimetallic Nanoparticles ◽  
Reduction Process ◽  
Nano Particles ◽  
Nano Structure ◽  
Small Shift ◽  
Molar Ratios ◽  
Vis Spectroscopy

Bimetallic nanoparticles of silver (Ag) and gold (Au) were synthesized at room temperature using Curcumin. Reduction process of silver and gold ions with different molar ratios leads to production of different nanostructures including alloys and core-shells. Produced nanoparticles were characterized simultaneously with FTIR, UV/vis. spectroscopy, transmission electron microscopy (TEM), and Energy-dispersive X-ray (EDAX). UV/vis. optical absorption spectra of as synthesized nanoparticles reveals presence of surface palsmon resonance (SPR) of both silver at (425 nm) and gold at (540 nm) with small shift and broadness of gold band after mixing with resucing and capping agent in natural extract which suggest presence of bimetallic nano structure (Au/Ag). FTIR and EDAX data approve the presence of bimetallic nano structure combined with curcumin extract. TEM micrographs shows that silver and gold can be synthesized separately in the form of nano particles using curcumin extract. Synthesis of gold nano particles in presence of silver effectively enhance and control formation of bi-metallic structure.

Predictive evaluation of multicomponent direct compress model tablets by integrating sphere UV-Vis spectroscopy and chemometrics

2021 ◽  
pp. 1-12
Author(s):  
Yuta Otsuka ◽  
Suvra Pal
Keyword(s):  
Regression Models ◽  
Process Analytical Technology ◽  
Compaction Pressure ◽  
Principal Component ◽  
Magnesium Stearate ◽  
Dicalcium Phosphate ◽  
Integrating Sphere ◽  
Pls Regression ◽  
Standard Normal Variate ◽  
Vis Spectroscopy

BACKGROUND: Control of the pharmaceutical manufacturing process and active pharmaceutical ingredients (API) is essential to product formulation and bioavailability. OBJECTIVE: The aim of this study is to predict tablet surface API concentration by chemometrics using integrating sphere UV-Vis spectroscopy, a non-destructive and contact-free measurement method. METHODS: Riboflavin, pyridoxine hydrochloride, dicalcium phosphate anhydrate, and magnesium stearate were mixed and ground with a mortar and pestle, and 100 mg samples were subjected to direct compression at a compaction pressure of 6 MPa at 7 mm diameter. The flat surface tablets were then analyzed by integrating sphere UV-Vis spectrometry. Standard normal variate (SNV) normalization and principal component analysis were applied to evaluate the measured spectral dataset. The spectral ranges were prepared at 300–800 nm and 500–700 nm with SNV normalization. Partial least squares (PLS) regression models were constructed to predict the API concentrations based on two previous datasets. RESULTS: The regression vector of constructed PLS regression models for each API was evaluated. API concentration prediction depends on riboflavin absorbance at 550 nm and the excipient dicalcium phosphate anhydrate. CONCLUSION: Integrating sphere UV-Vis spectrometry is a useful tool to process analytical technology.

Plasmon Resonance Energy Transfer from Metallic Nanoparticles to Biomolecules

2012 ◽  
pp. 2126-2126
Author(s):  
Patrick M. Winter ◽  
Gregory M. Lanza ◽  
Samuel A. Wickline ◽  
Marc Madou ◽  
Chunlei Wang ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Plasmon Resonance ◽  
Metallic Nanoparticles ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Plasmon Resonance Energy Transfer

Dielectric domain distribution on Au nanoparticles revealed by localized surface plasmon resonance

2018 ◽  
Vol 6 (44) ◽  
pp. 12038-12044 ◽  
Author(s):  
Yi Luo ◽  
Yadong Zhou ◽  
Shengli Zou ◽  
Jing Zhao
Keyword(s):  
Surface Plasmon Resonance ◽  
Surface Plasmon ◽  
Plasmon Resonance ◽  
Localized Surface Plasmon Resonance ◽  
Au Nanoparticles ◽  
Extinction Spectrum ◽  
Localized Surface Plasmon ◽  
Uniform Layer

The LSPR of Au nanospheres shows almost no shift in the extinction spectrum with attachment of a silica domain but considerable shift with a uniform layer of silica, indicating LSPR can be used to differentiate the segregated/uniform dielectric distribution.

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