Journal articles: 'Single particle scattering spectroscopy'

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Al-Zubeidi, Alexander, Lauren A. McCarthy, Ali Rafiei-Miandashti, Thomas S. Heiderscheit, and Stephan Link. "Single-particle scattering spectroscopy: fundamentals and applications." Nanophotonics 10, no. 6 (March 8, 2021): 1621–55. http://dx.doi.org/10.1515/nanoph-2020-0639.

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Abstract Metallic nanoparticles supporting a localized surface plasmon resonance have emerged as promising platforms for nanoscopic labels, sensors, and (photo-) catalysts. To use nanoparticles in these capacities, and to gain mechanistic insight into the reactivity of inherently heterogeneous nanoparticles, single-particle characterization approaches are needed. Single-particle scattering spectroscopy has become an important, highly sensitive tool for localizing single plasmonic nanoparticles and studying their optical properties, local environment, and reactivity. In this review, we discuss approaches taken for collecting the scattered light from single particles, their advantages and disadvantages, and present some recent applications. We introduce techniques for the excitation and detection of single-particle scattering such as high-angle dark-field excitation, total internal reflection dark-field excitation, scanning near-field microscopy, and interferometric scattering. We also describe methods to achieve polarization-resolved excitation and detection. We then discuss different approaches for scanning, ratiometric, snapshot, and interferometric hyperspectral imaging techniques used to extract spectral information. Finally, we provide a brief overview of specialized setups for in situ measurements of nanoparticles in liquid systems and setups coupled to scanning tip microscopes.

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Lindqvist, H., O. Jokinen, K. Kandler, D. Scheuvens, and T. Nousiainen. "Single scattering by realistic, inhomogeneous mineral dust particles with stereogrammetric shapes." Atmospheric Chemistry and Physics Discussions 13, no. 7 (July 9, 2013): 18451–88. http://dx.doi.org/10.5194/acpd-13-18451-2013.

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Abstract. Light scattering by single, inhomogeneous mineral dust particles was simulated based on shapes and compositions derived directly from measurements of real dust particles instead of using a mathematical shape model. We demonstrate the use of stereogrammetric shape retrieval method in the context of single-scattering modelling of mineral dust for four different dust types – all of them inhomogeneous – ranging from compact, equidimensional shapes to very elongated and aggregate shapes. The three-dimensional particle shapes were derived from stereo pairs of scanning-electron microscope images, and inhomogeneous composition was determined by mineralogical interpretation of localized elemental information based on energy-dispersive spectroscopy. Scattering computations were performed for particle equal-volume diameters from 0.08 μm up to 2.8 μm at 550 nm wavelength, using the discrete-dipole approximation. Particle-to-particle variation in scattering by mineral dust was found to be quite considerable and was not well reproduced by simplified shapes of homogeneous spheres, spheroids, or Gaussian random spheres. Effective-medium approximation results revealed that particle inhomogeneity should be accounted even for small amounts of absorbing media (here up to 2% of the volume), especially when considering scattering by inhomogeneous particles at size parameters 3

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Lindqvist, H., O. Jokinen, K. Kandler, D. Scheuvens, and T. Nousiainen. "Single scattering by realistic, inhomogeneous mineral dust particles with stereogrammetric shapes." Atmospheric Chemistry and Physics 14, no. 1 (January 6, 2014): 143–57. http://dx.doi.org/10.5194/acp-14-143-2014.

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Abstract. Light scattering by single, inhomogeneous mineral dust particles was simulated based on shapes and compositions derived directly from measurements of real dust particles instead of using a mathematical shape model. We demonstrate the use of the stereogrammetric shape retrieval method in the context of single-scattering modelling of mineral dust for four different dust types – all of them inhomogeneous – ranging from compact, equidimensional shapes to very elongated and aggregate shapes. The three-dimensional particle shapes were derived from stereo pairs of scanning-electron microscope images, and inhomogeneous composition was determined by mineralogical interpretation of localized elemental information based on energy-dispersive spectroscopy. Scattering computations were performed for particles of equal-volume diameters, from 0.08 μm up to 2.8 μm at 550 nm wavelength, using the discrete-dipole approximation. Particle-to-particle variation in scattering by mineral dust was found to be quite considerable and was not well reproduced by simplified shapes of homogeneous spheres, spheroids, or Gaussian random spheres. Effective-medium approximation results revealed that particle inhomogeneity should be accounted for even for small amounts of absorbing media (here up to 2% of the volume), especially when considering scattering by inhomogeneous particles at size parameters 3

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Pothorszky, S., D. Zámbó, D. Szekrényes, Z. Hajnal, and A. Deák. "Detecting patchy nanoparticle assembly at the single-particle level." Nanoscale 9, no. 29 (2017): 10344–49. http://dx.doi.org/10.1039/c7nr02623d.

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Berdahl, P., L. H. Espinoza, D. Littlejohn, D. Lucas, and D. L. Perry. "Near-Infrared Turbidity of β-FeOOH Particle Suspensions." Applied Spectroscopy 54, no. 2 (February 2000): 262–67. http://dx.doi.org/10.1366/0003702001949195.

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Near-infrared transmission spectroscopy can be complicated by the light scattering from heterogeneous materials. For the examination of an evolving system exhibiting such light scattering, transmission spectra near wavenumber v = 104 cm−1 were obtained during the hydrolysis of FeCl3 solutions. At first, the resulting turbid suspension of cigar-shaped β-FeOOH particles exhibits single-particle scattering, including a Rayleigh regime (attenuation ∞ v4). At later times, the scattering increases strongly as the particles aggregate, and becomes proportional to vα, with α ≈ 2, consistent with scattering models that interpret the structure of aggregates in terms of a fractal dimension df roughly equal to 2. In all cases investigated, the attenuation due to scattering is spectrally smooth and increases monotonically with wavenumber. It can be written in the simple form vα with 1 ≤ α ≤ 4. While over limited spectral ranges α may be taken independent of v, over wide ranges it decreases with increasing v. This behavior is consistent with the theoretical limits of α = 4 at v = 0, and α = 0 at v = ∞. Overall, the results suggest that a useful form for simulating scattering backgrounds in near-infrared spectroscopy is Avα, with A and α fitted constants.

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Esen, C., T. Kaiser, and G. Schweiger. "Raman Investigation of Photopolymerization Reactions of Single Optically Levitated Microparticles." Applied Spectroscopy 50, no. 7 (July 1996): 823–28. http://dx.doi.org/10.1366/0003702963905501.

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Raman spectroscopy was used to investigate polymerization reactions in a single micrometer-sized monomer droplet. An Ar+ laser levitated the microparticles and simultaneously excited the Raman scattering. The polymerization reaction was initiated by exposing the monomer droplets to the UV radiation of a mercury arc excitation lamp. The Raman spectrum of the reacting particle was investigated on-line. The results demonstrate that the combination of the technique of optical levitation and Raman spectroscopy allows nondestructive in situ measurements of single particles and is therefore very useful for the study of fundamental processes.

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Wongravee, Kanet, Harnchana Gatemala, Chuchaat Thammacharoen, Sanong Ekgasit, Sanpon Vantasin, Ichiro Tanabe, and Yukihiro Ozaki. "Nanoporous silver microstructure for single particle surface-enhanced Raman scattering spectroscopy." RSC Advances 5, no. 2 (2015): 1391–97. http://dx.doi.org/10.1039/c4ra11890a.

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Maconi, G., A. Penttilä, I. Kassamakov, M. Gritsevich, P. Helander, T. Puranen, A. Salmi, E. Hæggström, and K. Muinonen. "Non-destructive controlled single-particle light scattering measurement." Journal of Quantitative Spectroscopy and Radiative Transfer 204 (January 2018): 159–64. http://dx.doi.org/10.1016/j.jqsrt.2017.09.005.

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Schnepf, Max J., Yannic Brasse, Fabian R. Goßler, Anja Maria Steiner, Julian Obermeier, Markus Lippitz, Andreas Fery, and Tobias A. F. König. "Single Particle Spectroscopy of Radiative Processes in Colloid-to-Film-Coupled Nanoantennas." Zeitschrift für Physikalische Chemie 232, no. 9-11 (August 28, 2018): 1593–606. http://dx.doi.org/10.1515/zpch-2018-1109.

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Abstract We present a fluorescent emitter (rhodamine B) coupled to a dielectric or metallic interface as well as a metallic cavity to study their radiative decay processes. Supported by finite-difference time-domain (FDTD) simulations, we correlate the non-radiative and radiative decay rates with the absorption and scattering cross section efficiencies, respectively. On a single particle level, we use atomic force microscopy (AFM), scanning electron microscopy (SEM), scattering spectroscopy, fluorescence life time imaging (FLIM) and time-correlated single photon counting (TCSPC) to evaluate the enhanced fluorescence decay at the same location. With this study, we show a colloidal gain material, which can be integrated into lattices using existing directed self-assembled methods to study their coherent energy transfer.

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Cotterell, Michael I., Rose E. Willoughby, Bryan R. Bzdek, Andrew J. Orr-Ewing, and Jonathan P. Reid. "A complete parameterisation of the relative humidity and wavelength dependence of the refractive index of hygroscopic inorganic aerosol particles." Atmospheric Chemistry and Physics 17, no. 16 (August 22, 2017): 9837–51. http://dx.doi.org/10.5194/acp-17-9837-2017.

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Abstract. Calculations of aerosol radiative forcing require knowledge of wavelength-dependent aerosol optical properties, such as single-scattering albedo. These aerosol optical properties can be calculated using Mie theory from knowledge of the key microphysical properties of particle size and refractive index, assuming that atmospheric particles are well-approximated to be spherical and homogeneous. We provide refractive index determinations for aqueous aerosol particles containing the key atmospherically relevant inorganic solutes of NaCl, NaNO3, (NH4)2SO4, NH4HSO4 and Na2SO4, reporting the refractive index variation with both wavelength (400–650 nm) and relative humidity (from 100 % to the efflorescence value of the salt). The accurate and precise retrieval of refractive index is performed using single-particle cavity ring-down spectroscopy. This approach involves probing a single aerosol particle confined in a Bessel laser beam optical trap through a combination of extinction measurements using cavity ring-down spectroscopy and elastic light-scattering measurements. Further, we assess the accuracy of these refractive index measurements, comparing our data with previously reported data sets from different measurement techniques but at a single wavelength. Finally, we provide a Cauchy dispersion model that parameterises refractive index measurements in terms of both wavelength and relative humidity. Our parameterisations should provide useful information to researchers requiring an accurate and comprehensive treatment of the wavelength and relative humidity dependence of refractive index for the inorganic component of atmospheric aerosol.

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Ha, Ji Won. "Charactering Scattering Property of Micrometer-long Gold Nanowires with Single Particle Spectroscopy." Bulletin of the Korean Chemical Society 37, no. 6 (May 19, 2016): 974–76. http://dx.doi.org/10.1002/bkcs.10797.

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Moosmüller, H., and C. M. Sorensen. "Small and large particle limits of single scattering albedo for homogeneous, spherical particles." Journal of Quantitative Spectroscopy and Radiative Transfer 204 (January 2018): 250–55. http://dx.doi.org/10.1016/j.jqsrt.2017.09.029.

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Han, Yan, Lei Ding, Yingping Wang, Haiyang Zheng, and Li Fang. "Polarized light illuminated scattering characteristics of single airborne particle." Journal of Quantitative Spectroscopy and Radiative Transfer 266 (May 2021): 107568. http://dx.doi.org/10.1016/j.jqsrt.2021.107568.

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Laucks, Mary L., Feng Zheng, and E. James Davis. "Resonance Raman Scattering from Single Levitated Microparticles." Applied Spectroscopy 56, no. 11 (November 2002): 1436–43. http://dx.doi.org/10.1366/00037020260377733.

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Measurements of resonance Raman scattering from single crystalline (or amorphous) particles suspended in an electrodynamic balance have been made for inorganic and organic microparticles, potassium permanganate (KMnO4) and p-nitrosodimethylaniline ( p-NDMA), respectively. The microparticle dimensions were in the range 10–50 μm. The particles were obtained by evaporating aqueous solution droplets of KMnO4 and p-NDMA (0.01 M concentration) and potassium nitrate or sodium nitrate (1.0 M concentration) added as a nonresonance Raman standard or reference. Resonance Raman spectra were obtained using laser illumination at wavelengths of 514.5 and 488.0 nm. For MnO−4 particles at a laser wavelength of 514.5 nm, the fundamental symmetric stretch mode (ν1) and up to four overtones were observed. In addition, the antisymmetric stretch mode (ν3) and the combination mode (ν1 + ν3) could be seen. In p-NDMA particles, the phenyl-nitroso deformation mode (ν1) and the symmetric benzene ring-stretching mode (ν3) were observed using 488.0 nm laser radiation, but no overtones were distinguishable. As a measure of the morphological variability between particles, the ratio of the intensity of ν1 to the intensity of the largest nitrate ion (Raman) peak (normalized by the concentrations) was determined for each spectrum. This enhancement ratio or reference ratio was of order 100 and varied by 27% for 12 KMnO4 particles with 514.5 nm illumination, by 39% for 10 KMnO4 particles at 488.0 nm, and by 16% for 14 p-NDMA particles at 488.0 nm. Resonance Raman spectra obtained for KMnO4 particles before and after deliquescence indicated that photolysis occurred in the presence of water.

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McMillin, Brian K., Pratim Biswas, and Michael R. Zachariah. "In situ characterization of vapor phase growth of iron oxide-silica nanocomposites: Part I. 2-D planar laser-induced fluorescence and Mie imaging." Journal of Materials Research 11, no. 6 (June 1996): 1552–61. http://dx.doi.org/10.1557/jmr.1996.0194.

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Planar laser-based imaging measurements of fluorescence and particle scattering have been obtained during flame synthesis of iron-oxide/silica superparamagnetic nanocomposites. The theory and application of laser-induced fluorescence, the spectroscopy of FeO(g), and the experimental approach for measurement of gas phase precursors to particle formation are discussed. The results show that the vapor phase FeO concentration rapidly rises at the primary reaction front of the flame and is very sensitive to the amount of precursor added, suggesting nucleation-controlled particle growth. The FeO vapor concentration in the main nucleation zone was found to be insensitive to the amount of silicon precursor injected, indicating that nucleation occurred independently for the iron and silicon components. Light scattering measurements indicate that nanocomposite particles sinter faster than single component silica, in agreement with TEM measurements.

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Gong, Zhiyong, Yong-Le Pan, Gorden Videen, and Chuji Wang. "Online Characterization of Single Airborne Carbon Nanotube Particles Using Optical Trapping Raman Spectroscopy." Applied Spectroscopy 73, no. 8 (April 16, 2019): 910–16. http://dx.doi.org/10.1177/0003702819828809.

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Carbon nanotubes (CNTs) have become recognized as a potential environmental and health hazard as their applications are broadening and manufacturing costs are reducing. Fundamental information of CNTs in air is of significant importance to our understanding of their environmental fate as well as to further applications. Extensive efforts have been made over decades on characterizing CNTs; however, a majority of the studies are of bulk or CNTs dispersed on substrates. In the present study, we characterize single CNT particles in air using optical trapping Raman spectroscopy (OT-RS). Different types of CNT particles, as well as glassy carbon spheres, were optically trapped in air. Their physical properties were viewed by microscopic bright field images and scattering images; their chemical properties and structural information can be inferred from characteristic Raman bands. The system can also spatially resolve the morphology and chemical distribution of optically trapped CNT particles in air. The OT-RS technique combines single-particle morphological and chemical information and offers an online method to characterize the physicochemical properties of single CNT particles at their native states in air.

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Lee, Jaeran, Geun Wan Kim, and Ji Won Ha. "Single-particle spectroscopy and defocused imaging of anisotropic gold nanorods by total internal reflection scattering microscopy." Analyst 145, no. 18 (2020): 6038–44. http://dx.doi.org/10.1039/d0an01071e.

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Carr, Bob, and Duncan Griffiths. "Direct Visualisation, Sizing and Counting of Virus and Phage Particles in Liquids." Microscopy Today 17, no. 1 (January 2009): 34–37. http://dx.doi.org/10.1017/s1551929500054997.

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A laser-based, single nano-particle tracking analysis system was described in the March issue of Microscopy Today. The LM series of analyzers from NanoSight allows nanoscale particles such as viruses to be directly and individually visualised in liquids in real time, from which high-resolution particle size distribution profiles can be obtained, figure 1. The technique is fast, robust, accurate, and low cost representing an attractive alternative or complement to expensive and more complex methods of nano-particle analysis such as dynamic light scattering (photon correlation spectroscopy) or electron microscopy.By simultaneously and directly measuring the diffusion coefficient of each and every particle, the dedicated Nanoparticle Tracking Analysis (NTA) software suite allows the user to automatically count and size the viruses in a sample. Results are displayed as graphs of size against count of individual particles (or size versus relative brightness), thus overcoming the limitations inherent in other particle analysis systems that generate only mean particle size distribution data with resolution.

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Momenimovahed, Ali, Fengshan Liu, Kevin A. Thomson, Gregory J. Smallwood, and Hongsheng Guo. "Effect of fuel composition on properties of particles emitted from a diesel–natural gas dual fuel engine." International Journal of Engine Research 22, no. 1 (April 29, 2019): 77–87. http://dx.doi.org/10.1177/1468087419846018.

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The effective density and mixing state of particles emitted from a natural gas–diesel dual fuel engine are investigated. Measurements were conducted at three different fuel compositions including 100% diesel fuel (0% NG), 75% diesel–25% natural gas (25% NG) and 50% diesel–50% NG (50% NG). The particle effective density was measured using a differential mobility analyzer in series with a centrifugal particle mass analyzer. A catalytic stripper at 350 °C was employed upstream of the centrifugal particle mass analyzer in order to remove the semi-volatile material from the solid particles to measure the effective density of non-volatile particles as well as the particle mixing state. A scanning mobility particle sizer was used to measure the particle size distribution. The particle mass concentration was also measured using several techniques including cavity-attenuated phase-shift particulate matter single-scattering albedo, laser-induced incandescence, thermal-optical analysis, photoacoustic spectroscopy, and integrated particle size distribution. The semi-volatile number and mass fractions are found to be lower than 15%. The effective density functions of particles at 0% and 25% NG are within 6% of each other; however, the effective density values of particles at 50% NG are lower than those of the 0% NG by up to 35%. The mass-mobility exponent varies in the range of 2.42–2.51 and 2.38–2.54 for undenuded and denuded particles, respectively. For the mass concentration measurements, photoacoustic spectroscopy agrees with thermal-optical analysis within 5%, while all the other techniques measure up to 50% deviations relative to thermal-optical analysis.

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Spencer, Elinor, Alexander Kolesnikov, Brian Woodfield, and Nancy Ross. "New Insights about CuO Nanoparticles from Inelastic Neutron Scattering." Nanomaterials 9, no. 3 (February 26, 2019): 312. http://dx.doi.org/10.3390/nano9030312.

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Inelastic Neutron Scattering (INS) spectroscopy has provided a unique insight into the magnetodymanics of nanoscale copper (II) oxide (CuO). We present evidence for the propagation of magnons in the directions of the ordering vectors of both the commensurate and helically modulated incommensurate antiferromagnetic phases of CuO. The temperature dependency of the magnon spin-wave intensity (in the accessible energy-range of the experiment) conforms to the Bose population of states at low temperatures (T ≤ 100 K), as expected for bosons, then intensity significantly increases, with maximum at about 225 K (close to TN), and decreases at higher temperatures. The obtained results can be related to gradual softening of the dispersion curves of magnon spin-waves and decreasing the spin gap with temperature approaching TN on heating, and slow dissipation of the short-range dynamic spin correlations at higher temperatures. However, the intensity of the magnon signal was found to be particle size dependent, and increases with decreasing particle size. This “reverse size effect” is believed to be related to either creation of single-domain particles at the nanoscale, or “superferromagnetism effect” and the formation of collective particle states.

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Bido, Ariadne T., Britta G. Nordberg, Marit A. Engevik, Nathan C. Lindquist, and Alexandre G. Brolo. "High-Speed Fluctuations in Surface-Enhanced Raman Scattering Intensities from Various Nanostructures." Applied Spectroscopy 74, no. 11 (July 17, 2020): 1398–406. http://dx.doi.org/10.1177/0003702820940391.

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The observation of single molecule events using surface-enhanced Raman scattering (SERS) is a well-established phenomenon. These events are characterized by strong fluctuations in SERS intensities. High-speed SERS intensity fluctuations (in the microsecond time scale) have been reported for experiments involving single metallic particles. In this work, the high-speed SERS behavior of six different types of nanostructured metal systems (Ag nanoshells, Ag nanostars, Ag aggregated spheres, Au aggregated spheres, particle-on-mirror, and Ag deposited on microspheres) was investigated. All systems demonstrated high-speed SERS intensity fluctuations. Statistical analysis of the duration of the SERS fluctuations yielded tailed distributions with average event durations around 100 μs. Although the characteristics of the fluctuations seem to be random, the results suggest interesting differences between the system that might be associated with the strength distribution and density of the localized SERS hotspots. For instance, systems with more localized fields, such as nanostars, present faster fluctuation bursts compared to metallic aggregates that support spread-out fields. The results presented here appear to confirm that high-speed SERS intensity fluctuations are a fundamental characteristic of the SERS effect.

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Singh, Sujeeta, Marc N. Fiddler, and Solomon Bililign. "Measurement of size-dependent single scattering albedo of fresh biomass burning aerosols using the extinction-minus-scattering technique with a combination of cavity ring-down spectroscopy and nephelometry." Atmospheric Chemistry and Physics 16, no. 21 (November 1, 2016): 13491–507. http://dx.doi.org/10.5194/acp-16-13491-2016.

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Abstract. Biomass burning (BB) aerosols have a significant effect on regional climate, and represent a significant uncertainty in our understanding of climate change. Using a combination of cavity ring-down spectroscopy and integrating nephelometry, the single scattering albedo (SSA) and Ångstrom absorption exponent (AAE) were measured for several North American biomass fuels. This was done for several particle diameters for the smoldering and flaming stage of white pine, red oak, and cedar combustion. Measurements were done over a wider wavelength range than any previous direct measurement of BB particles. While the offline sampling system used in this work shows promise, some changes in particle size distribution were observed, and a thorough evaluation of this method is required. The uncertainty of SSA was 6 %, with the truncation angle correction of the nephelometer being the largest contributor to error. While scattering and extinction did show wavelength dependence, SSA did not. SSA values ranged from 0.46 to 0.74, and were not uniformly greater for the smoldering stage than the flaming stage. SSA values changed with particle size, and not systematically so, suggesting the proportion of tar balls to fractal black carbon change with fuel type/state and particle size. SSA differences of 0.15–0.4 or greater can be attributed to fuel type or fuel state for fresh soot. AAE values were quite high (1.59–5.57), despite SSA being lower than is typically observed in wildfires. The SSA and AAE values in this work do not fit well with current schemes that relate these factors to the modified combustion efficiency of a burn. Combustion stage, particle size, fuel type, and fuel condition were found to have the most significant effects on the intrinsic optical properties of fresh soot, though additional factors influence aged soot.

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Jiang, Wei, Huatian Hu, Qian Deng, Shunping Zhang, and Hongxing Xu. "Temperature-dependent dark-field scattering of single plasmonic nanocavity." Nanophotonics 9, no. 10 (May 23, 2020): 3347–56. http://dx.doi.org/10.1515/nanoph-2020-0076.

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AbstractPlasmonic materials have long been exploited for enhanced spectroscopy, integrated nanophotonic circuits, sensing, light harvesting, etc. Damping is the key factor that limits their performance and restricts the development of the field. Optical characterization of single nanoparticle at low temperature is ideal for investigating the damping of plasmons but is usually technically impractical due to the sample vibration from the cryostat and the surface adsorption during the cooling process. In this work, we use a vibration-free cryostat to investigate the temperature-dependent dark-field scattering spectroscopy of a single Au nanowire on top of a Au film. This allows us to extract the contribution of electron-phonon scattering to the damping of plasmons without performing statistics over different target nanoparticles. The results show that the full width at half-maximum of the plasmon resonance increases by an amount of 5.8%, over the temperature range of 5−150 K. Electromagnetic calculations reveal that the temperature-insensitive dissipation channels into photons or surface plasmon polaritons on the Au film contribute up to 64% of the total dissipations at the plasmon resonance. This explains why the reduction of plasmon linewidth seems small at the single-particle level. This study provides a more explicit measurement on the damping process of the single plasmonic nanostructure, which serves as basic knowledge in the applications of nanoplasmonic materials.

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Lane, P. A., M. B. Hart, V. Jain, J. E. Tucker, and J. D. Eversole. "Characterization of single particle aerosols by elastic light scattering at multiple wavelengths." Journal of Quantitative Spectroscopy and Radiative Transfer 208 (March 2018): 188–95. http://dx.doi.org/10.1016/j.jqsrt.2017.12.017.

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Kalume, Aimable, Chuji Wang, and Yong-Le Pan. "Optical-Trapping Laser Techniques for Characterizing Airborne Aerosol Particles and Its Application in Chemical Aerosol Study." Micromachines 12, no. 4 (April 20, 2021): 466. http://dx.doi.org/10.3390/mi12040466.

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We present a broad assessment on the studies of optically-trapped single airborne aerosol particles, particularly chemical aerosol particles, using laser technologies. To date, extensive works have been conducted on ensembles of aerosols as well as on their analogous bulk samples, and a decent general description of airborne particles has been drawn and accepted. However, substantial discrepancies between observed and expected aerosols behavior have been reported. To fill this gap, single-particle investigation has proved to be a unique intersection leading to a clear representation of microproperties and size-dependent comportment affecting the overall aerosol behavior, under various environmental conditions. In order to achieve this objective, optical-trapping technologies allow holding and manipulating a single aerosol particle, while offering significant advantages such as contactless handling, free from sample collection and preparation, prevention of contamination, versatility to any type of aerosol, and flexibility to accommodation of various analytical systems. We review spectroscopic methods that are based on the light-particle interaction, including elastic light scattering, light absorption (cavity ring-down and photoacoustic spectroscopies), inelastic light scattering and emission (Raman, laser-induced breakdown, and laser-induced fluorescence spectroscopies), and digital holography. Laser technologies offer several benefits such as high speed, high selectivity, high accuracy, and the ability to perform in real-time, in situ. This review, in particular, discusses each method, highlights the advantages and limitations, early breakthroughs, and recent progresses that have contributed to a better understanding of single particles and particle ensembles in general.

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Szczerba, Wojciech, Rocio Costo, Sabino Veintemillas-Verdaguer, Maria del Puerto Morales, and Andreas F. Thünemann. "SAXS analysis of single- and multi-core iron oxide magnetic nanoparticles." Journal of Applied Crystallography 50, no. 2 (March 14, 2017): 481–88. http://dx.doi.org/10.1107/s1600576717002370.

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This article reports on the characterization of four superparamagnetic iron oxide nanoparticles stabilized with dimercaptosuccinic acid, which are suitable candidates for reference materials for magnetic properties. Particles p1 and p2 are single-core particles, while p3 and p4 are multi-core particles. Small-angle X-ray scattering analysis reveals a lognormal type of size distribution for the iron oxide cores of the particles. Their mean radii are 6.9 nm (p1), 10.6 nm (p2), 5.5 nm (p3) and 4.1 nm (p4), with narrow relative distribution widths of 0.08, 0.13, 0.08 and 0.12. The cores are arranged as a clustered network in the form of dense mass fractals with a fractal dimension of 2.9 in the multi-core particles p3 and p4, but the cores are well separated from each other by a protecting organic shell. The radii of gyration of the mass fractals are 48 and 44 nm, and each network contains 117 and 186 primary particles, respectively. The radius distributions of the primary particle were confirmed with transmission electron microscopy. All particles contain purely maghemite, as shown by X-ray absorption fine structure spectroscopy.

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Zelenay, V., R. Mooser, T. Tritscher, A. Křepelová, M. F. Heringa, R. Chirico, A. S. H. Prévôt, et al. "Aging fingerprints in combustion particles." Atmospheric Chemistry and Physics Discussions 11, no. 5 (May 11, 2011): 14455–93. http://dx.doi.org/10.5194/acpd-11-14455-2011.

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Abstract. Soot particles can significantly influence the Earth's climate by absorbing and scattering solar radiation as well as by acting as cloud condensation nuclei. However, despite their environmental (as well as economic and political) importance, the way these properties are affected by atmospheric processing is still a subject of discussion. In this work, soot particles emitted from two different cars, a EURO 2 transporter, a EURO 3 passenger vehicle, and a wood stove were investigated on a single-particle basis. The emitted exhaust, including the particulate and the gas phase, was processed in a smog chamber with artificial solar radiation. Single particle specimens of both unprocessed and aged soot were characterized using x-ray absorption spectroscopy and scanning electron microscopy. Comparison of the spectra from the unprocessed and aged soot particles revealed changes in the carbon functional group content, such as that of carboxylic carbon, which can be ascribed to both the condensation of secondary organic compounds on the soot particles and oxidation of primary soot particles upon photochemical aging. Changes in the morphology and size of the single soot particles were also observed upon aging. Furthermore, we show that the soot particles take up water in humid environments and that their water uptake capacity increases with photochemical aging.

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Amelink, Arjen, Martin P. L. Bard, Sjaak A. Burgers, and Henricus J. C. M. Sterenborg. "Single-scattering spectroscopy for the endoscopic analysis of particle size in superficial layers of turbid media." Applied Optics 42, no. 19 (July 1, 2003): 4095. http://dx.doi.org/10.1364/ao.42.004095.

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Dworak, Volker, Benjamin Mahns, Jörn Selbeck, Robin Gebbers, and Cornelia Weltzien. "Hyperspectral Imaging Tera Hertz System for Soil Analysis: Initial Results." Sensors 20, no. 19 (October 3, 2020): 5660. http://dx.doi.org/10.3390/s20195660.

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Analyzing soils using conventional methods is often time consuming and costly due to their complexity. These methods require soil sampling (e.g., by augering), pretreatment of samples (e.g., sieving, extraction), and wet chemical analysis in the laboratory. Researchers are seeking alternative sensor-based methods that can provide immediate results with little or no excavation and pretreatment of samples. Currently, visible and infrared spectroscopy, electrical resistivity, gamma ray spectroscopy, and X-ray spectroscopy have been investigated extensively for their potential utility in soil sensing. Little research has been conducted on the application of THz (Tera Hertz) spectroscopy in soil science. The Tera Hertz band covers the frequency range between 100 GHz and 10 THz of the electromagnetic spectrum. One important feature of THz radiation is its correspondence with the particle size of the fine fraction of soil minerals (clay < 2 µm to sand < 2 mm). The particle size distribution is a fundamental soil property that governs soil water and nutrient content, among other characteristics. The interaction of THz radiation with soil particles creates detectable Mie scattering, which is the elastic scattering of electromagnetic waves by particles whose diameter corresponds approximately to the wavelength of the radiation. However, single-spot Mie scattering spectra are difficult to analyze and the understanding of interaction between THz radiation and soil material requires basic research. To improve the interpretation of THz spectra, a hyperspectral imaging system was developed. The addition of the spatial dimension to THz spectra helps to detect relevant features. Additionally, multiple samples can be scanned in parallel and measured under identical conditions, and the high number of data points within an image can improve the statistical accuracy. Technical details of the newly designed hyperspectral imaging THz system working from 250 to 370 GHz are provided. Results from measurements of different soil samples and buried objects in soil demonstrated its performance. The system achieved an optical resolution of about 2 mm. The sensitivity of signal damping to the changes in particle size of 100 µm is about 10 dB. Therefore, particle size variations in the µm range should be detectable. In conclusion, automated hyperspectral imaging reduced experimental effort and time consumption, and provided reliable results because of the measurement of hundreds of sample positions in one run. At this stage, the proposed setup cannot replace the current standard laboratory methods, but the present study represents the initial step to develop a new automated method for soil analysis and imaging.

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Maiz, Jon, Ester Verde-Sesto, Isabel Asenjo-Sanz, Paula Malo de Molina, Bernhard Frick, José A. Pomposo, Arantxa Arbe, and Juan Colmenero. "Dynamic Processes and Mechanisms Involved in Relaxations of Single-Chain Nano-Particle Melts." Polymers 13, no. 14 (July 14, 2021): 2316. http://dx.doi.org/10.3390/polym13142316.

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We present a combined study by quasielastic neutron scattering (QENS), dielectric and mechanical spectroscopy, calorimetry and wide-angle X-ray diffraction on single-chain nano-particles (SCNPs), using the corresponding linear precursor chains as reference, to elucidate the impact of internal bonds involving bulky cross-links on the properties of polymer melts. Internal cross-links do not appreciably alter local properties and fast dynamics. This is the case of the average inter-molecular distances, the β-relaxation and the extent of the atomic displacements at timescales faster than some picoseconds. Contrarily, the α-relaxation is slowed down with respect to the linear precursor, as detected by DSC, dielectric spectroscopy and QENS. QENS has also resolved broader response functions and stronger deviations from Gaussian behavior in the SCNPs melt, hinting at additional heterogeneities. The rheological properties are also clearly affected by internal cross-links. We discuss these results together with those previously reported on the deuterated counterpart samples and on SCNPs obtained through a different synthesis route to discern the effect of the nature of the cross-links on the modification of the diverse properties of the melts.

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Rajeswari, R., and R. Jothilakshmi. "Modeling and Simulation of Plasmonic Nanoparticles Using Finite-Difference Time-Domain Method: A Review." Materials Science Forum 781 (March 2014): 33–44. http://dx.doi.org/10.4028/www.scientific.net/msf.781.33.

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In recent years, plasmonic nanoparticles are widely used in a wide range of applications including, biomedicine, spectroscopy, catalysis and energy harvesting. The properties of these particles are due to the interaction of these particles with electromagnetic irradiation that gives rise to the localized surface plasmons that are collective oscillations of their surface conduction electrons. This interaction influences its light absorption and scattering and thus, the particle color. Simulation of particle plasmons can be done by solving Maxwells equations for metallic nanoparticles embedded in a dielectric environment. One of the approaches to solve Maxwells equation is by Finite Difference Time Domain (FDTD) approach. Since FDTD is a time domain approach, the response for a wide range of frequencies can be obtained with a single simulation. In this paper we propose to review the application of FDTD in the simulation and modeling of various plasmonic nanoparticles.

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Popp, J., M. Lankers, M. Trunk, I. Hartmann, E. Urlaub, and W. Kiefer. "High-Precision Determination of Size, Refractive Index, and Dispersion of Single Microparticles from Morphology-Dependent Resonances in Optical Processes." Applied Spectroscopy 52, no. 2 (February 1998): 284–91. http://dx.doi.org/10.1366/0003702981943365.

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Analyzing morphology-dependent resonances observed in optical processes, like Raman scattering or fluorescence emission from single microparticles, allows an exact determination of size, refractive index, and optical dispersion. The main feature of the method discussed here is an exact Mie calculation combined with an optimization program. The results obtained from a gradient-trapped emulsion particle and those from an optically levitated droplet are discussed to show the advantages of the method. It is further demonstrated that only by a precise analysis of the observed morphology-dependent resonances is it possible to describe the droplet evolution.

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Schavkan, Alexander, Christian Gollwitzer, Raul Garcia-Diez, Michael Krumrey, Caterina Minelli, Dorota Bartczak, Susana Cuello-Nuñez, et al. "Number Concentration of Gold Nanoparticles in Suspension: SAXS and spICPMS as Traceable Methods Compared to Laboratory Methods." Nanomaterials 9, no. 4 (April 1, 2019): 502. http://dx.doi.org/10.3390/nano9040502.

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The industrial exploitation of high value nanoparticles is in need of robust measurement methods to increase the control over product manufacturing and to implement quality assurance. InNanoPart, a European metrology project responded to these needs by developing methods for the measurement of particle size, concentration, agglomeration, surface chemistry and shell thickness. This paper illustrates the advancements this project produced for the traceable measurement of nanoparticle number concentration in liquids through small angle X-ray scattering (SAXS) and single particle inductively coupled plasma mass spectrometry (spICPMS). It also details the validation of a range of laboratory methods, including particle tracking analysis (PTA), dynamic light scattering (DLS), differential centrifugal sedimentation (DCS), ultraviolet visible spectroscopy (UV-vis) and electrospray-differential mobility analysis with a condensation particle counter (ES-DMA-CPC). We used a set of spherical gold nanoparticles with nominal diameters between 10 nm and 100 nm and discuss the results from the various techniques along with the associated uncertainty budgets.

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Aptowicz, Kevin B., Yong-Le Pan, Sean D. Martin, Elena Fernandez, Richard K. Chang, and Ronald G. Pinnick. "Decomposition of atmospheric aerosol phase function by particle size and asphericity from measurements of single particle optical scattering patterns." Journal of Quantitative Spectroscopy and Radiative Transfer 131 (December 2013): 13–23. http://dx.doi.org/10.1016/j.jqsrt.2013.03.020.

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Schön, Roland, Martin Schnaiter, Zbigniew Ulanowski, Carl Schmitt, Stefan Benz, Ottmar Möhler, Steffen Vogt, Robert Wagner, and Ulrich Schurath. "Particle Habit Imaging Using Incoherent Light: A First Step toward a Novel Instrument for Cloud Microphysics." Journal of Atmospheric and Oceanic Technology 28, no. 4 (April 1, 2011): 493–512. http://dx.doi.org/10.1175/2011jtecha1445.1.

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Abstract The imaging unit of the novel cloud particle instrument Particle Habit Imaging and Polar Scattering (PHIPS) probe has been developed to image individual ice particles produced inside a large cloud chamber. The PHIPS produces images of single airborne ice crystals, illuminated with white light of an ultrafast flashlamp, which are captured at a maximum frequency of ∼5 Hz by a charge-coupled device (CCD) camera with microscope optics. The imaging properties of the instrument were characterized by means of crystalline sodium hexafluorosilicate ice analogs, which are stable at room temperature. The optical resolving power of the system is ∼2 μm. By using dedicated algorithms for image processing and analysis, the ice crystal images can be analyzed automatically in terms of size and selected shape parameters. PHIPS has been operated at the cloud simulation chamber facility Aerosol Interaction and Dynamics in the Atmosphere (AIDA) of the Karlsruhe Institute of Technology at different temperatures between −17° and −4°C in order to study the influence of the ambient conditions, that is, temperature and ice saturation ratio, on ice crystal habits. The area-equivalent size distributions deduced from the PHIPS images are compared with the retrieval results from Fourier transform infrared (FTIR) extinction spectroscopy in case of small (<20 μm) and with single particle data from the cloud particle imager in case of larger (>20 μm) ice particles. Good agreement is found for both particle size regimes.

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Sugimoto, Hiroshi, Yoichi Ikuno, and Minoru Fujii. "Absolute Scattering Cross Sections of Titanium Nitride Nanoparticles Determined by Single-Particle Spectroscopy: Implications for Plasmonic Nanoantennas." ACS Applied Nano Materials 2, no. 10 (September 11, 2019): 6769–73. http://dx.doi.org/10.1021/acsanm.9b01725.

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Díaz-Hernández, Azariel, Jorge Gracida, Blanca E. García-Almendárez, Carlos Regalado, Rosario Núñez, and Aldo Amaro-Reyes. "Characterization of Magnetic Nanoparticles Coated with Chitosan: A Potential Approach for Enzyme Immobilization." Journal of Nanomaterials 2018 (July 4, 2018): 1–11. http://dx.doi.org/10.1155/2018/9468574.

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Cross-linking of magnetic nanoparticles with proteins plays a significant role in the preparation of new materials for biotechnological applications. The aim was the maximization of the magnetic mass attracted and protein loading of magnetic iron oxide nanoparticles coated with chitosan, synthesized in a single step by alkaline precipitation. Chitosan-coated magnetite particles (Fe3O4@Chitosan) were cross-linked to a xylanase and a cellulase (Fe3O4@Chitosan@Proteins), showing a 93% of the magnetic saturation of the magnetite. X-ray diffraction pattern in composites corresponds to magnetite. Thermogravimetry and differential scanning calorimetry showed that 162 mg of chitosan was coating one gram of composite and 12 mg of protein was cross-linked to each gram of magnetic support. Cross-linking between enzymes and Fe3O4@Chitosan was confirmed by infrared spectroscopy with Fourier transform, X-ray energy, and X-ray photoelectron spectroscopy dispersion analysis. From dynamic light scattering, transmission and electron microscopy the average particle size distribution was 230 nm and 430 nm for Fe3O4@Chitosan and Fe3O4@Chitosan@Proteins, showing agglomerates of individual spherical particles, with an average diameter of 8.5 nm and 10.8 nm, respectively. The preparation method plays a key role in determining the particle size and shape, size distribution, surface chemistry, and, therefore, the applications of the superparamagnetic nanoparticles.

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Dik, V. P., A. P. Ivanov, and V. A. Loiko. "Features of light scattering by a single-row layer of particles." Journal of Applied Spectroscopy 46, no. 2 (February 1987): 197–202. http://dx.doi.org/10.1007/bf00665564.

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HATEGAN, CORNEL, GERHARD GRAW, and HORIA COMISEL. "THE p-WAVE THRESHOLD EFFECT AND QUASIRESONANT SCATTERING." Modern Physics Letters A 20, no. 03 (January 30, 2005): 187–201. http://dx.doi.org/10.1142/s0217732305016385.

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The p-wave threshold effect is described in terms of the reduced scattering matrix. The relationship of this approach to previous theoretical threshold models is established. We prove that this phenomenon is related to the reaction-mechanism of quasiresonant scattering: a single particle neutron threshold state and direct interaction coupling to open observed channels. Spectroscopic aspects of the threshold effect, both with respect to the magnitude and microstructure, are discussed in terms of the neutron strength function.

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Lee, Wei-Cheng, Wan Kyu Park, Hamood Z. Arham, Laura H. Greene, and Philip Phillips. "Theory of point contact spectroscopy in correlated materials." Proceedings of the National Academy of Sciences 112, no. 3 (January 5, 2015): 651–56. http://dx.doi.org/10.1073/pnas.1422509112.

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We developed a microscopic theory for the point-contact conductance between a metallic electrode and a strongly correlated material using the nonequilibrium Schwinger-Kadanoff-Baym-Keldysh formalism. We explicitly show that, in the classical limit, contact size shorter than the scattering length of the system, the microscopic model can be reduced to an effective model with transfer matrix elements that conserve in-plane momentum. We found that the conductance dI/dV is proportional to the effective density of states, that is, the integrated single-particle spectral function A(ω = eV) over the whole Brillouin zone. From this conclusion, we are able to establish the conditions under which a non-Fermi liquid metal exhibits a zero-bias peak in the conductance. This finding is discussed in the context of recent point-contact spectroscopy on the iron pnictides and chalcogenides, which has exhibited a zero-bias conductance peak.

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Aardahl, Christopher L., and E. James Davis. "Gas/Aerosol Chemical Reactions in the NaOH-SO2-H2O System." Applied Spectroscopy 50, no. 1 (January 1996): 71–77. http://dx.doi.org/10.1366/0003702963906663.

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The hydrolysis of a solid NaOH microparticle in humid nitrogen and the chemical reaction between the resulting NaOH solution microdroplet and SO2 gas have been studied with the use of elastic and inelastic (Raman) light scattering. A single solid NaOH particle was levitated electrodynamically in a reaction chamber and exposed to water vapor. After hydrolysis/deliquescence, the resulting solution droplet was exposed to SO2 gas. Raman spectra and elastic resonance spectra collected during the reactions indicate that low SO2 concentrations in the gas phase yield NaHSO3 while high SO2 concentrations result in Na2SO3 as the product. These results indicate that the reversibility of the key reactions becomes important when the SO2 concentration is low.

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Chandran, Preethi L. "Sequential Extraction of Late Exponentials (SELE): A technique for deconvolving multimodal correlation curves in Dynamic Light Scattering." MRS Advances 5, no. 17 (2020): 865–80. http://dx.doi.org/10.1557/adv.2020.163.

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Abstract:In techniques such as Dynamic Light Scattering (DLS), Fluorescence Correlation Spectroscopy, and image mining, motion is tracked by the autocorrelation of a signal over logarithmic time scales. For instance the tracking signal in DLS is the scattered light intensity; it remains correlated at time scales where scant changes in the arrangement of the scattering particles occur, but decays exponentially at the time scales of their diffusion. When there are multiple time scales of motion (for instance due to scatterers of different sizes), the correlation curve has more than one exponential fall. Extracting the decay constants or hydrodynamic sizes due to each exponential fall in a multi-species field correlation curve becomes an ill-conditioned mathematical problem. We describe a new algorithm to invert a multi-modal correlation curve by Sequential Extraction of the Late Exponentials (SELE). The idea is that while the inversion of a multi-exponential equation may be ill posed, that of a single exponential is not. So we fit data windows towards to base of the correlation curve to extract the largest contribution species, remove the species contribution from the correlation curve, and repeat the process with the remnant curve. The single exponent can be robustly fitted by least-square minimization with initial guesses generated by an adapted cumutant technique (power-series) that includes stretch coefficients (measure of sample dispersity). The proposed algorithm resolves particle sizes separated by 3X, and is reliable against fluctuations in the correlation curve and to localized regions of suboptimal data. The algorithm can be used to track particle dynamics in solution in multi-species problems such as self-assembly.

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Krieger, Ulrich K., and Christian Braun. "Light-scattering intensity fluctuations in single aerosol particles during deliquescence." Journal of Quantitative Spectroscopy and Radiative Transfer 70, no. 4-6 (August 2001): 545–54. http://dx.doi.org/10.1016/s0022-4073(01)00028-0.

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Panetta, R. Lee, Siyao Zhai, and Ping Yang. "Internal electromagnetic waves, energy trapping, and energy release in simple time-domain simulations of single particle scattering." Journal of Quantitative Spectroscopy and Radiative Transfer 228 (May 2019): 27–46. http://dx.doi.org/10.1016/j.jqsrt.2019.01.015.

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Ma, Ying, and Lin-Yue Lanry Yung. "Gold Nanoplate-Based 3D Hierarchical Microparticles: A Single Particle with High Surface-Enhanced Raman Scattering Enhancement." Langmuir 32, no. 31 (July 25, 2016): 7854–59. http://dx.doi.org/10.1021/acs.langmuir.6b01247.

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Sajanlal, P. R., and T. Pradeep. "Bimetallic Mesoflowers: Region-Specific Overgrowth and Substrate Dependent Surface-Enhanced Raman Scattering at Single Particle Level." Langmuir 26, no. 11 (June 2010): 8901–7. http://dx.doi.org/10.1021/la904676u.

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Marcano Olaizola, Aristides. "Photothermal Determination of Absorption and Scattering Spectra of Silver Nanoparticles." Applied Spectroscopy 72, no. 2 (October 25, 2017): 234–40. http://dx.doi.org/10.1177/0003702817738056.

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This work reports on photothermal lens spectra of silver nanoparticles of different dimensions in the spectral region of 370–730 nm performed using an arc-lamp-based photothermal spectrophotometer. We show that the photothermal and extinction cross-section spectra of the samples are similar for nanoparticles of reduced dimensions where scattering effects are small. The results differ substantially for nanoparticles of a diameter larger than 30 nm for which scattering becomes relevant. We demonstrate that the photothermal spectrum corresponds to the absorption component of the particle’s extinction. Photothermal spectra show a clear picture of the plasmonic peaks of the nanoparticle even in the presence of high scattering. By subtracting the photothermal component from the total extinction, we extract the scattering cross-section spectra of the nanoparticles. The technique allows determination of the absorption and scattering components of the extinction providing a better understanding of the particle’s optical properties. The results agree well with the Mie approximation, which is valid for a single spherical nanoparticle. We discuss and demonstrate the application of the method to characterize particles of arbitrary shape and dimensions.

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Polwart, Ewan, Ruth L. Keir, Christine M. Davidson, W. Ewen Smith, and Daran A. Sadler. "Novel SERS-Active Optical Fibers Prepared by the Immobilization of Silver Colloidal Particles." Applied Spectroscopy 54, no. 4 (April 2000): 522–27. http://dx.doi.org/10.1366/0003702001949690.

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A novel sensor based upon surface-enhanced Raman scattering (SERS) has been constructed by immobilizing colloidal silver particles onto the distal end of an optical fiber. This same single fiber was then used to both transport the exciting laser radiation and collect the Raman scattering from analytes sorbed onto the colloidal particles. The colloidal particles were immobilized by functionalization of the end of the optical fiber with (3-aminopropyl)trimethoxysilane prior to immersion of the fiber in silver colloid. Spectra were obtained from both 4-(5′-azobenzotriazol)3,5-dimethoxyphenylamine and crystal violet. The within-batch variation of a set of five fibers has been measured as approximately 10%. Raman imaging experiments demonstrated that the effects due to spatial variations in the intensity of the SERS recorded over the distal end of the fiber are removed by the use of a multimode fiber.

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Li, Yi, Hock Siah Lim, Zhi Kui Wang, Ser Choon Ng, and Meng Hau Kuok. "Micro-Brillouin Study of the Eigenvibrations of Single Isolated Polymer Nanospheres." Journal of Nanoscience and Nanotechnology 8, no. 11 (November 1, 2008): 5869–72. http://dx.doi.org/10.1166/jnn.2008.18365.

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The localized acoustic modes of single isolated polymethyl methacrylate (PMMA) and polystyrene nanospheres have been studied by micro-Brillouin light scattering. The measured mode frequencies are analyzed on the basis of the Lamb theory formulated for a sphere under free boundary conditions. By measuring light scattering from single isolated particles, placed atop a piece of polished silicon wafer, the free-surface conditions are almost experimentally realized. The observed spectral peaks are attributed to localized eigenvibrations whose frequencies scale as inverse sphere diameter, in accordance with Lamb's theory. The Young's moduli and Poisson ratios of the polymer spheres studied have been evaluated from fits to the experimental data. We have demonstrated that micro-Brillouin spectroscopy is a powerful technique for probing the acoustic dynamics and mechanical properties of nanostructures.

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Zelenay, V., R. Mooser, T. Tritscher, A. Křepelová, M. F. Heringa, R. Chirico, A. S. H. Prévôt, et al. "Aging induced changes on NEXAFS fingerprints in individual combustion particles." Atmospheric Chemistry and Physics 11, no. 22 (November 24, 2011): 11777–91. http://dx.doi.org/10.5194/acp-11-11777-2011.

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Abstract. Soot particles can significantly influence the Earth's climate by absorbing and scattering solar radiation as well as by acting as cloud condensation nuclei. However, despite their environmental (as well as economic and political) importance, the way these properties are affected by atmospheric processing of the combustion exhaust gases is still a subject of discussion. In this work, individual soot particles emitted from two different vehicles, a EURO 2 transporter, a EURO 3 passenger car, and a wood stove were investigated on a single-particle basis. The emitted exhaust, including the particulate and the gas phase, was processed in a smog chamber with artificial solar radiation. Single particle specimens of both unprocessed and aged soot were characterized using near edge X-ray absorption fine structure spectroscopy (NEXAFS) and scanning electron microscopy. Comparison of NEXAFS spectra from the unprocessed particles and those resulting from exhaust photooxidation in the chamber revealed changes in the carbon functional group content. For the wood stove emissions, these changes were minor, related to the relatively mild oxidation conditions. For the EURO 2 transporter emissions, the most apparent change was that of carboxylic carbon from oxidized organic compounds condensing on the primary soot particles. For the EURO 3 car emissions oxidation of primary soot particles upon photochemical aging has likely contributed as well. Overall, the changes in the NEXAFS fingerprints were in qualitative agreement with data from an aerosol mass spectrometer. Furthermore, by taking full advantage of our in situ microreactor concept, we show that the soot particles from all three combustion sources changed their ability to take up water under humid conditions upon photochemical aging of the exhaust. Due to the selectivity and sensitivity of the NEXAFS technique for the water mass, also small amounts of water taken up into the internal voids of agglomerated particles could be detected. Because such small amounts of water uptake do not lead to measurable changes in particle diameter, it may remain beyond the limits of volume growth measurements, especially for larger agglomerated particles.

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Journal articles on the topic 'Single particle scattering spectroscopy'

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