Publications

AN001 Analysis of Polymeric Particle Mixes via SPES Technology

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ABSTRACT: Mixes of polymeric particle dispersions are common in a multitude of applications and products such as pharmaceutical, personal care, food, ceramics, pigments, inks, and cements. A proper dispersion of the particles is necessary to avoid sedimentation, instability, or product failure due to aggregation, oversize, and aging. Bottom-up Quality-by-Design formulation, top-down Safe-by-Design approaches and product manufacturing require a reliable method to analyse the different particulate populations in all the intermediate formulation steps and in the final product.

AN002 Continuous SPES Flow Analysis CFA-SPES

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ABSTRACT: Multiparametric Continuous Flow Analysis (CFA) of submicron and micrometric particles is an analytical approach aimed to the automatic time resolved and continuous measure of particles suspended in a flowing fluid. CFA becomes widely used in many research and quality control processes, eg. for the in-line/on-line monitoring of particles in pilot synthesis reactors or for the particle characterisation using synergic methods on the same flowing complex sample of complex industrial, biological, and environmental interest. This results in a high-resolution data set of particle qualitative and quantitative time resolved information. Three cases of CFA capabilities of EOS Classizer™ ONE and SPES method are exploited and presented for the inline / online characterisation of water-based particle suspensions of general interest in flowing fluids.

AN003 Addressing the Issue of Wetting and Clustering by Means of SPES Technology

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ABSTRACT: A quantitative multiparametric analysis of powders suspended in water is discussed as a case study of typical issues caused by surface activity and wetting properties of grains, with the consequent aging/aggregation processes bringing to irregular, internally mixed clusters that are difficult to be recognised and understood. Classizer™ ONE, through the SPES patented method, allows to get insight into these typical issues when handling dry powders suspended in liquids.

AN004 Addressing the Classification of Non Spherical Particles by Mean of the SPES Technology

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ABSTRACT: A multiparametric analysis of the optical properties of non spherical particles suspended in water is discussed as a case study. Advantages of SPES technology in particle classification are discussed of particle with a non aspect ratio since it can impact the obtainable results with the most common instruments for particle analysis without being observed.

AN005 Batch To Batch Consistency Via Multiparametric SPES Principal Component Analysis (SPES-PCA)

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ABSTRACT: The capability of EOS SPES-PCA software add-on to perform a Principal Component Analysis on a SPES dataset via supervised learning technique has been presented. SPES-PCA provides added value exploratory data analysis and sample classification based on SPES multiparametric data. It speeds up batch to batch processing in a Quality Control production line, detecting small differences between apparently very similar sets of measures. A quantitative PCA classification of data consistency via K-nn algorithm provides quick and effective batch analysis comparing data of novel batches with data libraries and dataset of reference samples.

AN006 Multiparametric Classification of Particles as a Pathway to Oversize Analysis in Complex Fluids via SPES Technology

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ABSTRACT: A quantitative multiparametric analysis of grains in watercolor pigments via Classizer™ ONE and SPES patented method is reported as a case study of a more general approach for multicomponent complex fluids. SPES data for the whole sample particle population are presented first. A PSD is recovered by best fitting refractive index to data and assuming particles as spheres, as commonly done in traditional methods. A preliminary oversize analysis is obtained. Further, the main population is considered in more details, evidencing three subpopulations with different optical properties. By separating them, three PSDs are obtained. The corresponding oversize analysis shows remarkable differences with the former. Moreover, the subpopulations exhibit clear differences in terms of the refractive indexes. A careful analysis of the populations suggests the presence of clustering.

AN011 Quantitative Classification of Particles in BioFluids as human plasma and cell lysate via SPES Technology

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ABSTRACT: A quantitative multiparametric analysis of particles incubated in target biological liquid matrix via Classizer™ ONE and SPES patented method is reported. Two application cases of capital importance are considered: a) drug carriers based on particles. These systems are receiving every day increasing attention as effective tools for the modulation of the pharmacokinetic and the pharmacodynamic profiles of delivered drugs. b) eco-/cito-toxicology studies facing nowadays global problems of particle short and long-term impact on ecosystems and human health. As a reference, nanoplastics (≤1000 nm).

AN012 Monitoring the Fate of a Lipid/ZnO Emulsion in Environmental Waters

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ABSTRACT: The capabilities of EOS Classizer™ ONE and SPES patented method provide unique added value time resolved classification of particles suspended in environmental waters. Thanks to its unique properties, SPES was able to investigate, in a deeper way with respect to traditional light scattering technologies, the sample composition as well as other peculiar behaviors in sample aging and degradation, even in target environmental contexts.

AN013 Analysis of Abrasives via SPES Technology

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ABSTRACT: Abrasives are natural or artificial substances of great hardness used in mechanical processing. In this application note the novel classification and characterization of oxide particles in liquids via patented SPES technology and EOS Classizer™ ONE is presented for key abrasive materials and commercial products, as eg silica particles, silica powders, diamond paste, and ceria slurry.

AN015 Classification of Oil and Oil Mixes Emulsions via SPES Technology

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ABSTRACT: The wide applications of oil-in-water emulsions range from pharmaceuticals to beverages, from paints to specialty chemicals, and more. Particle analysis plays a fundamental role in the design, formulation, and QC of oil-in-water emulsions, enabling the observation of the growth process and the stability of the particles. In this application note the classification and characterization of oil-in-water emulsions via patented SPES and Classizer™ ONE is presented.

AN016 Multiparametric Determination of Yeast Cell Viability via SPES Technology

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ABSTRACT: The EOS Classizer™ ONE provides an accurate estimation of the cell viability regardless the presence of secondary populations and impurities. In this app notes, the Saccharomyces cerevisiae yeast is suspended in ethanol and hydrogen peroxide solutions as examples of stress factors. Monitoring of cell viability over time is performed via CFA-SPES tool. Multiparametric Principal Component Analysis SPES-PCA provides Batch-to-Batch QC analysis.

AN017 SPES Classification of Probiotic Formulations

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ABSTRACT: in this application notes, the classification, the quantification, and the characterization via patented SPES technology and EOS Classizer™ ONE of a commercial probiotic product composed of a mixture of two populations of particles are presented.

AN018 Classification of Inks and Pigments via SPES Technology

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ABSTRACT: Inks, watercolours, and oil pigments are mixture of microscopic and sub-microscopic grains, typically suspended in a liquid that allows the pigment to be applied. Measuring size and refractive index of pigments is of utmost importance for characterizing them and for improving product formulation. The further presence of secondary populations in the formulation, as oil emulsions in suspension, limits and/or precludes the traditional particle sizer to perform an effective and reliable measure. The classification, the quantification, and the characterization via EOS Classizer™ ONE of commercial products and colour/oil emulsion mix are presented.

AN019 SPES Classification of Vinyl Glues

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ABSTRACT: The vinyl glue is one of the most used adhesives with several brands and manufacturers on the market. The most commonly used vinyl synthetic resin is polyvinyl acetate (PVAc) in an aqueous emulsion, which has a variety of applications. In this application note, the classification of two commercial aqueous vinyl glues via EOS Classizer™ ONE and liquid sample manager EOS LMS01™ is presented.

AN020 Multiparametric analysis of particles in toothpastes

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ABSTRACT: Toothpastes are formulated with a variety of components. The three main ones are abrasives, fluoride, and detergents. Abrasives constitute 10-20% of a typical toothpaste. These insoluble particles are designed to help remove plaque from the teeth. In this document, the optical classification and analysis of particles in popular toothpastes using Classizer™ ONE and LMS01™ sample manager is presented.

AN021 SPES Classification of Mayonnaise

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ABSTRACT: The classification and analysis of real, flavoured, and vegan mayonnaises via EOS Classizer™ ONE and liquid sample manager EOS LMS01™ is presented in this app note.

Evidence of Sub-Micrometric Plastic Release When Heating Food Containers Based on Light Scattering Measurements

Pallavera M, Sanvito T, Cremonesi L, Artoni C, Falqui A, Potenza MAC

Part. Part. Syst. Charact. 2400029 (2024)

ABSTRACT: A growing body of literature is raising concerns about the spread of nano- and microplastics and the hazards they pose to the environment and on human health. There is still a limited understanding of their sources and formation mechanisms, making their release and uptake difficult to track and quantify. Among the obstacles to the progress in this field there is the lack of reliable methods for quantitative studies, leading to a potential underestimation of the extent of their release and the related risks. In this paper, the application of an optical method for studying the release of sub-micrometric plastics in water by polypropylene containers certified for alimentary use is described. The results show evidence of negligible release when the temperature of the water is kept below the manufacturer’s specifications, whereas a rampant increase occurs beyond these conditions, irrespective of the thermal history of the sample. Particles with a diameter distribution that spans one order of magnitude are observed, ranging from ≈200 nm to 2 µm, and their refractive index and shape is characterized with light scattering measurements. This work focuses on particle release and does not assess toxicity or effects on living organisms.

An overview of the optical characterization of free microparticles and their radiative properties

Potenza M, Cremonesi L

Toxics 11, 413 (2023)

ABSTRACT: We discuss how the range of information available from microparticle analysis can be extended in a number of applications by measuring a specific set of optical properties of individual particles using light scattering. Central to these measurements are the real and imaginary components of the forward scattered field, the former being equal to the extinction cross-section except for a few particle-independent constants. Although still a niche technique, it has some inherent advantages and great potential for particle characterization, especially in the challenging near-wavelength size range. A selection of cases is covered from an experimental point of view, while some essential models are introduced to illustrate the underlying physical phenomena. We present a benchmark of experimental results from the literature and other examples that support optical diagnostics applied in science and industrial processes. As a key point of this work, we show that by accessing the fundamental properties of scatterers the inversion of light scattering data can be avoided. This provides model-independent results closer to application requirements without the drawbacks of case-specific assumptions.

Light extinction and scattering from aggregates composed of submicron particles

Cremonesi L, Minnai C, Ferri F, Parola A, Paroli B, Sanvito T & Potenza MAC

Journal of Nanoparticle Research volume 22, Article number: 344 (2020)

ABSTRACT: The influence of the internal structure of inhomogeneous particles on their radiative properties is an open issue repeatedly questioned in many fields of science and technology. The importance of a refined description of the particle composition and structure, going beyond mean-field approximations, is generally recognized. Here, we focus on describing internal inhomogeneities from a statistical point of view. We introduce an analytical description based on the two-point density-density correlation function, or the corresponding static structure factor, to calculate the extinction cross sections. The model agrees with numerical predictions and is validated experimentally with colloidal aggregates in the 0.3–6 μm size range, which serve as an inhomogeneous model system that can be characterized enough to work without any free parameters. The model can be tightly compared to measurements with single particle extinction and scattering and spectrophotometry and suggests a simple behavior for 90° scattering from fractal aggregates as a function of extinction, which is also confirmed experimentally and numerically. We also discuss the case of absorbing particles and report the experimental results for water suspensions of black carbon for both the forward and 90° scattering properties. In this case, the total scattering and the extinction cross sections determine the single scattering albedo, which agrees with numerical simulations. The three parameters necessary to feed radiative transfer models, namely, extinction, asymmetry parameter, and single scattering albedo, can all be set by the analytical model, with explicit dependence on a few parameters. Results are applicable to radiative transfer problems in climate, paleoclimate, star and planetary formation, and nanoparticle optical characterization for science and industry, including the intercomparison of different optical methods such as those adopted by ISO standards.

Particle shape accounts for instrumental discrepancy in ice core dust size distributions

Simonsen MF, Cremonesi L, Baccolo G, Bosch S, Delmonte B, Erhardt T, Kjær HA, Potenza M, Svensson A and Vallelonga P

Clim. Past, 14, 601-608 (2018)

ABSTRACT: light obscuration particle counter and coulter based particle counter are both used for measuring the size distribution of insoluble mineral dust particles in ice cores. While the coulter method measures particle volume accurately, the equivalent light obscuration method measurement deviates substantially from the coulter depending on the type of sample. We show that the difference between the light obscuration and the coulter method measurements is mainly caused by the irregular shape of dust particles in ice core samples. The irregular shape leads means that the calibration routine based on standard spheres must be adjusted. This new calibration routine gives an increased accuracy on light obscuration measurements, which may improve future ice core record intercomparisons. We derived an analytical model for extracting the aspect ratio of dust particles from the difference between light obscuration and coulter method data. For verification, we measured the aspect ratio of the same samples directly using a Single Particle Extinction and Scattering Instrument (SPES). The results demonstrate that the model is accurate enough to discern between samples of aspect ratio 0.3 and 0.4 using only the comparison of light obscuration and coulter method data.

In vitro assessment of silver nanoparticles immunotoxicity

Galbiati V, Cornaghi L, Gianazza E, Potenza MAC, Donetti E, Marinovich M, Corsini E

Food and Chemical Toxicology (2018), In press, Accepted Manuscript

ABSTRACT: This study aimed to characterize unwanted immune effects of nanoparticles (NP) using THP-1 cells, human whole blood and enriched peripheral blood monocytes. Commercially available silver NP (AgNP < 100 nm, also confirmed by Single Particle Extinction and Scattering) were used as prototypical NP. Cells were treated with AgNP alone or in combination with classical immune stimuli (i.e. LPS, PHA, PWM) and cytokine assessed; in addition, CD54 and CD86 expression was evaluated in THP-1 cells. AgNP alone induced dose-related IL-8 production in all models, with higher response observed in THP-1 cells, possibly connected to different protein corona formation in bovine versus human serum. AgNP potentiated LPS-induced IL-8 and TNF-α, but not LPS-induced IL-10. AgNP alone induced slight increase in IL-4, and no change in IFN-γ production. While responses to PHA in term of IL-4 and IFN-γ production were not affected, increased PWM-induced IL-4 and IFN-γ production were observed, suggesting potentiation of humoral response. Reduction in PHA-induced IL-10 was observed. Overall, results indicate immunostimulatory effects. THP-1 cells work as well as primary cells, representing a useful and practical alternative, with the awareness that from a physiological point of view the whole blood assay is the one that comes closest to reality.

Single-Particle Extinction and Scattering Method Allows for Detection and Characterization of Aggregates of Aeolian Dust Grains in Ice Cores

Potenza MAC, Cremonesi L, Delmonte B, Sanvito T, Paroli B, Pullia A, Baccolo G and Maggi V

ACS Earth Space Chem. (2017), Article

ABSTRACT: Mineral dust aerosol in ice cores is one of the most important proxies for paleoclimate research. Under certain conditions, in the deeper part of ice cores, the pristine paleoclimate signal can be altered by in situ formation of dust aggregates, following the relocation of the impurities. Thus, aggregate detection is a critical indication for post-depositional processes. Clues for the presence of aggregates have been provided by anomalously large dust size distributions, while small aggregates were basically invisible to conventional dust analysis techniques. In this paper, we propose an optical approach to this problem based on the single-particle extinction and scattering (SPES) method, which allows researchers to distinguish between compact and non-compact particles through the analysis of samples populated by isometric particles contained in the core samples. This method can potentially be used during continuous flow analyses of ice cores. It allows for the detection of even the tiniest aggregates, falling within the typical size interval of aeolian mineral aerosol. This approach will potentially provide key evidence for assessing the integrity of paleoclimate records.

Shape and size constraints on dust optical properties from the Dome C ice core, Antarctica

Potenza MAC, Albani S, Delmonte B, Villa S, Sanvito T, Paroli B, Pullia A, Baccolo G, Mahowald N & Maggi V

Scientific Reports 6 (2016), Article

ABSTRACT: Mineral dust aerosol (dust) is widely recognized as a fundamental component of the climate system and is closely coupled with glacial-interglacial climate oscillations of the Quaternary period. However, the direct impact of dust on the energy balance of the Earth system remains poorly quantified, mainly because of uncertainties in dust radiative properties, which vary greatly over space and time. Here we provide the first direct measurements of the aerosol optical thickness of dust particles windblown to central East Antarctica (Dome C) during the last glacial maximum (LGM) and the Holocene. By applying the Single Particle Extinction and Scattering (SPES) technique and imposing preferential orientation to particles, we derive information on shape from samples of a few thousands of particles. These results highlight that clear shape variations occurring within a few years are hidden to routine measurement techniques. With this novel measurement method the optical properties of airborne dust can be directly measured from ice core samples, and can be used as input into climate model simulations. Based on simulations with an Earth System Model we suggest an effect of particle non-sphericity on dust aerosol optical depth (AOD) of about 30% compared to spheres, and differences in the order of ~10% when considering different combinations of particles shapes.

Optical characterization of particles for industries

Potenza MAC, Sanvito T, Fazio G

KONA Powder and Particle review (2015)

ABSTRACT: In this work we focus on the characterization of micro- and nano-powders typically adopted for chemical mechanical polishing, extensively used whenever the global and local planarization of surfaces is required as in nanoelectronic fabs. We present an innovative method for the accurate characterization of water suspensions of nanoparticles. It relies upon the combination of a new approach to extract light-scattering information from single particles and the recently developed diagnostic tool named Single Particle Extinction and Scattering. It can be used in line. Data interpretation becomes independent of any a-priori assumptions about the samples. The results of accurate measurements performed on ceria as well as aluminium oxide slurries are reported. We show the strong advantages of this method compared with traditional ones by explicitly reporting experimental results on calibrated spheres made of different materials. We discuss possible applications for in-line characterization of ultrapure water, chemicals, slurries for abrasive processes, for example, as well as the detection of any undesired particles – which could be the key for future improvements to advanced process control systems.

Single particle optical extinction and scattering allows real time quantitative characterization of drug payload and degradation of polymeric nanoparticles

Potenza MAC, Sanvito T, Argentiere S, Cella C, Paroli B, Lenardi C, Milani P

Scientific Reports 5 (2015)

ABSTRACT: The behavior of nanoparticles in biological systems is determined by their dimensions, size distribution, shape, surface chemistry, density, drug loading and stability; the characterization of these parameters in realistic conditions and the possibility to follow their evolution in vitro and in vivo are, in most of the cases, far from the capabilities of the standard characterization technologies. Optical techniques such as dynamic light scattering (DLS) are, in principle, well suited for in line characterization of nanoparticle, however their fail in characterizing the evolution of nanoparticle in solution where change in particle dimension and density is present. Here we present an in-line optical technique based on single particle extinction and scattering (SPES) overcoming the limitations typical of DLS and allowing for the efficient characterization of nanoparticle polydispersity, index of refraction and degradation dynamics in solution. Using SPES, we characterized the evolution of PLGA nanoparticles with different structures and drug payloads in solution and we compared the results with DLS. Our results suggest that SPES could be used as a process analytical technology for pharmaceutical nanoparticle production.

Measuring the complex field scattered by single submicron particles

Potenza MAC, Sanvito T, Pullia A

AIP Advances 5 (2015)

ABSTRACT: We describe a method for simultaneous measurements of the real and imaginary parts of the field scattered by single nanoparticles illuminated by a laser beam, exploiting a self-reference interferometric scheme relying on the fundamentals of the Optical Theorem. Results obtained with calibrated spheres of different materials are compared to the expected values obtained through a simplified analytical model without any free parameters, and the method is applied to a highly polydisperse water suspension of Poly(D,L-lactide-co-glycolide) nanoparticles. Advantages with respect to existing methods and possible applications are discussed.

Toxicological Profile of PM from Different Sources in the Bronchial Epithelial Cell Line BEAS-2B

Melzi G, Nozza E, Frezzini MA, Canepari S, Vecchi R, Cremonesi L, Potenza M, Marinovich M and Corsin E

Toxics 11, 413 (2023)

ABSTRACT: The toxicity of particulate matter (PM) is strictly associated with its physical-chemical characteristics, such as size or chemical composition. While these properties depend on the origin of the particles, the study of the toxicological profile of PM from single sources has rarely been highlighted. Hence, the focus of this research was to investigate the biological effects of PM from five relevant sources of atmospheric PM: diesel exhaust particles, coke dust, pellet ashes, incinerator ashes, and brake dust. Cytotoxicity, genotoxicity, oxidative, and inflammatory response were assessed in a bronchial cell line (BEAS-2B). BEAS-2B cells were exposed to different concentrations (25, 50, 100, and 150 μg/mL medium) of particles suspended in water. The exposure lasted 24 h for all the assays performed, except for reactive oxygen species, which were evaluated after 30 min, 1 h, and 4 h of treatment. The results showed a different action of the five types of PM. All the tested samples showed a genotoxic action on BEAS-2B, even in the absence of oxidative stress induction. Pellet ashes seemed to be the only ones able to induce oxidative stress by boosting the formation of reactive oxygen species, while brake dust resulted in the most cytotoxic. In conclusion, the study elucidated the differential response of bronchial cells to PM samples generated by different sources. The comparison could be a starting point for a regulatory intervention since it highlighted the toxic potential of each type of PM tested.

On the quasi-universality of the forward light scattering lobe for micrometric objects

MAC Potenza, Cremonesi L

Journal of Quantitative Spectroscopy and Radiative Transfer, 278, 108028 (2022)

ABSTRACT: A quasi-universality property of Mie scattering was reported in a recent publication by C.M. Sorensen [J. Quant. Spectrosc. Radiat. Transf. (2013) 131, 3]: the authors represent the forward scattered intensity, normalized by the differential Rayleigh cross section, as a function of the coupling parameter. Here we provide clear experimental evidence of this result; the Sorensen plots are produced without any free parameter for pure water droplets suspended in air and oil-in-water emulsions measured by the Single Particle Extinction and Scattering method. In addition, as inferred by Sorensen, we find that non-spherical objects deviate from the quasi-universality behavior of spheres by applying the same approach to mineral dust. Notably, the larger discrepancies occur in the wavelength-scale size range. These plots can widen the field of diagnostics in the critical micrometric size range.

Multiparametric optical characterization of airborne dust with Single Particle Extinction and Scattering

Cremonesi L, Passerini A, Tettamanti A, Paroli B, Delmonte B, Albani S, Cavaliere F, Viganò D, BettegaG , Sanvito T, Pullia A & Potenza MAC

Environment International, 123, 156-163 (2019)

ABSTRACT: We describe a robust, portable, deployable instrument for multiparametric optical characterization of single airborne particles. It is based on the Single Particle Extinction and Scattering method with additional sensors at 45° and 90° angles. Four independent optical parameters are associated to each particle. Basically, it provides a rigorous measurement of the extinction cross section and the complex amplitude of the forward scattered field. Moreover, thanks to the multiparametric single particle approach, it is possible to roughly classify the particles within a size range from a few hundreds of nanometers to some micrometers. By assigning a reasonable single scattering albedo for each population, our data are enough to fit the phase function with acceptable uncertainties. We report here the results of tests performed with water droplets, generating well controlled data without any free parameters. Data analysis is described in detail. We also report measurements performed on urban aerosol collected in the city of Milan by recovering the optical properties and feeding radiative transfer models. The findings reported here support the importance of an accurate measurement of the phase function, as already established by the Community.

Phytotoxicity of wear debris from traditional and innovative brake pads

Maiorana S, Teoldi F, Silvani S, Mancini A, Sanguineti A, Mariani F, Cella C, Lopez A, Potenza MAC, Lodi M, Dupin D, Sanvito T, Bonfanti A, Benfenati E, Baderna D

Environment International, 123, 156-163 (2019)

ABSTRACT: Traffic-related emissions include gas and particles that can alter air quality and affect human and environmental health. Limited studies have demonstrated that particulate debris thrown off from brakes are toxic to higher plants. The acute phytotoxicity of brake pad wear debris (BPWD) investigated using cress seeds grown in soil contaminated with increasing concentrations of debris. Two types of pads were used: a commercially available phenol based pad and an innovative cement-based pad developed within of the LIFE+ COBRA project. The results suggested that even through the BPWD generated by the two pads were similar in and morphology, debris from traditional pads were more phytotoxic than that from cementitious pads, causing significant alterations in terms of root elongation and loss of plasma membrane integrity.

Multiparametric optical characterization of airborne dust with Single Particle Extinction and Scattering

Cremonesi L, Passerini A, Tettamanti A, Paroli B, Delmonte B, Albani S, Cavaliere F, Viganò D, BettegaG , Sanvito T, Pullia A & Potenza MAC

Environment International, 123, 156-163 (2019)

ABSTRACT: We describe a robust, portable, deployable instrument for multiparametric optical characterization of single airborne particles. It is based on the Single Particle Extinction and Scattering method with additional sensors at 45° and 90° angles. Four independent optical parameters are associated to each particle. Basically, it provides a rigorous measurement of the extinction cross section and the complex amplitude of the forward scattered field. Moreover, thanks to the multiparametric single particle approach, it is possible to roughly classify the particles within a size range from a few hundreds of nanometers to some micrometers. By assigning a reasonable single scattering albedo for each population, our data are enough to fit the phase function with acceptable uncertainties. We report here the results of tests performed with water droplets, generating well controlled data without any free parameters. Data analysis is described in detail. We also report measurements performed on urban aerosol collected in the city of Milan by recovering the optical properties and feeding radiative transfer models. The findings reported here support the importance of an accurate measurement of the phase function, as already established by the Community.

Single Particle Extinction and Scattering allows novel optical characterization of aerosols

Mariani F, Bernardoni V, Riccobono F, Vecchi R, Valli G, Sanvito T, Paroli B, Pullia A, Potenza MAC

J Nanopart Res 19 (2017)

ABSTRACT: We apply to aerosols the optical method of Single Particle Extinction and Scattering recently proposed for characterizing liquid suspensions and specifically adapted to the aim. It provides simultaneous measurements of the real and imaginary parts of the field scattered in the forward direction by single airborne particles passing through a tightly focused laser beam. The intensity of transmitted light is collected in the forward direction, thus realizing a self-reference interferometric scheme relying on the fundamentals of the optical theorem. A high frequency (20 MS/s), extended dynamics (12 bits) sampling is performed by a cheap segmented photodiode, and a specific pulse shape analysis is exploited to validate the signals against a precise mathematical model. We show that accessing two independent physical quantities allows to exploit physical models to recover the aerosol size distribution from the measurement of the refractive index, either real or even complex. Laboratory measurements have been performed with polydisperse aerosols made of water droplets and NaCl in the submicron range, and the system has been accurately characterized. Examples of measurements of graphite nanoparticles and Pyrethrum smoke are shown. Limitations are discussed.

Single particle extinction and scattering optical method unveils in real time the influence of the blood components on polymeric nanoparticles

Sanvito T, Bigini P, Cavanna MV, Fiordaliso F, Violatto MB, Talamini L, Salmona M, Milani P, Potenza MAC

Nanomedicine (2017), Article

ABSTRACT: Here we report the quantitative in situ characterization of size distribution evolution of polymeric nanoparticles incubated in murine serum, filtered and unfiltered murine blood. We used an analytical optical approach, named Single Particle Extinction and Scattering (SPES), which relies on the measurements of two independent parameters of single particles. SPES is based on a robust self-reference interference optical scheme which allows a rejection of the spurious signals coming from the background caused by the medium. We employed polystyrene nanoparticles as reference system and polydisperse poly(lactic-co-glycolic acid) nanoparticles. Our results demonstrate that SPES can be used for carrying out ex vivo analysis of nanoparticles to evaluate the modifications that NPs undergo in vivo following different routes of entry. Conversely, Dynamic Light Scattering is not able to provide reliable results for these systems due to the presence of the biological components in solution.

Detecting the Shape of Anisotropic Gold Nanoparticles in Dispersion With Single Particle Extinction and Scattering

Potenza MAC, Krpetic Z, Sanvito T, Cai Q, Monopoli M, de Araújo JM, Cella C, Boselli L, Castagnola V, Milani M and Dawson KA

Nanoscale (2017), Advance Article

ABSTRACT: The shape and size of nanoparticles are important parameters affecting the biodistribution, bioactivity, and toxicity. The high-throughput characterisation of nanoparticle shape in the dispersion is a fundamental prerequisite for realistic in vitro and in vivo evaluation, however, with routinely available bench-top optical characterisation techniques, it remains a challenging task. Herein, we demonstrate the efficacy of Single Particle Extinction and Scattering (SPES) technique for the in situ detection of the shape of nanoparticles in dispersion, applied to a small library of anisotropic gold particles, with potential developments of in-line detection. The use of SPES paves the way to the routine quantitative analysis of nanoparticles dispersed in biologically relevant fluids, which is of importance for the nanosafety assessment and any in vitro and in vivo administration of nanomaterials.

Measuring shape and size of micrometric particles from the analysis of the forward scattered field

Villa S, Sanvito T, Paroli B, Pullia A, Delmonte B, Potenza MAC

J. Appl. Phys. 119 (2016)

ABSTRACT: Characterizing nano- and micro-particles in fluids still proves to be a significant challenge for both science and industry. Here we show how to determine shape and size distributions of polydisperse water suspensions of micron-sized particles by the analysis of the field scattered in the forward direction by single particles illuminated by a laser beam. We exploit the novel Single Particle Extinction and Scattering (SPES) method in connection with shear conditions which give preferred orientations to the particles passing through the scattering volume. Water suspensions of calibrated non-spherical particles, polydisperse standard monophasic mineral samples of quartz and kaolinite, and a mixture of quartz and illite are studied in details. Application and limitation of the method are discussed.

Accurate sizing of ceria oxide nanoparticles in slurries by the analysis of the optical forward-scattered field

Potenza MAC, Sanvito T, Pullia A

J Nanopart Res 17 (2014)

ABSTRACT: We characterize slurries composed of ceria nanoparticles in the range of 100–400 nm by exploiting a new approach which makes the data interpretation independent of any a priori assumption about the sample and provides very accurate and precise measurement of the particle size distribution, irrespectively of the huge polydispersity. The complex field scattered by single particles is determined by simultaneous measurements of the extinction cross section and the forward-scattered field amplitude. Moreover, we show how this approach overcomes typical issues encountered with this kind of suspensions such as the presence of aggregates, spurious components, and gas bubbles, at variance with any other method for measuring single particles. Applications are discussed.

Free nanoparticle characterization by optical scattering field analysis: opportunities and perspectives

Potenza MAC, Milani P

J Nanopart Res 16 (2014)

ABSTRACT: Methods for the facile and in-line characterization of size distribution and physical properties of unsupported nanoparticles are of paramount importance for fundamental research and industrial applications. The state-of-the-art free nanoparticle characterization methods do not provide accuracy, high throughput, and operation easiness to support widespread use for routine characterization. In this perspective paper, we describe and discuss the opportunities provided by approaches for nanoparticle characterization based on optical measurements of the field scattered by particles. In particular, we show how insightful is the measure of both the real and the imaginary parts of the field amplitude, a task that has been considered in the past but never had a widespread exploitation. A number of opportunities are generated by this approach, in view of assessing a more efficient characterization and a better understanding of the properties of nanoparticles. We focus our attention on the capability of characterizing nanoparticles of wide interest for applications, considering cases where traditional approaches are not currently effective. Possible exploitations are both in research and in industrial environments: to validate a synthetic process, for example, or for in-line monitoring of a production plant to generate advanced process control tools, as well as decision-making tools for acting in real time during the production.