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Mesoporous materials could serve as promising thermally insulating materials for window applications due to their low thermal conductivity at ambient conditions. However, they tend to be translucent and hazy due to their nanoscale porous architecture controlling their optical and radiative properties. This dissertation aims to (i) computationally generate and characterize realistic mesoporous materials, (ii) explore how their nanoscale structure affect their light scattering characteristics, and (iii) apply the knowledge gained to understand light transfer through drying mesoporous monoliths and optical characterization of thin films.First, three-dimensional mesoporous materials consisting of a network of touching or overlapping spheres were computationally generated using the diffusion-limited cluster-cluster aggregation (DLCCA) method. A new algorithm was developed to reproduce nitrogen adsorption porosimetry and retrieve their pore size distributions. The numerically computed specific surface areas and pore size distributions were in good agreement with experimental data reported for mesoporous silica. Second, unpolarized electromagnetic wave scattering by the computer-generated mesoporous structures, described as porous fractal aggregates, were investigated using the T-matrix and discrete-dipole approximation (DDA) methods. The transition between the independent and dependent scattering regimes was studied in systems with up to 8 particles. Independent scattering refers to situations when particles are sufficiently distant that some radiation characteristics of the ensemble can be determined by adding the contributions of each particle. When particles are in close proximity, however, dependent scattering prevails and is affected by near-field interactions and far-field interferences among scattered waves from nearby particles. Here, the dimensionless parameters governing the scattering cross-section and asymmetry factor of non-absorbing particle suspensions and aggregates were found to be (i) the particle size parameter, (ii) the relative index of refraction, (iii) the interparticle distance-to-wavelength ratio, and (iv) the number of particles. Different transition criteria were derived for the scattering cross-section and the asymmetry factor. Dependent scattering effects prevailed in all aggregates and increased with decreasing particle size parameter. In addition, particle overlapping had a negligible effect on the scattering cross-section and asymmetry factor. Furthermore, predictions of the integral scattering characteristics of non-absorbing aggregates with relatively small particle size parameter were found to be accurately predicted by the equivalent effective property (EEP) approximation treating the aggregates as homogeneous spheres with the same volume and an effective refractive index. The EEP approximation was then combined with the Monte Carlo method to predict the transmittance and haze of ambiently drying mesoporous monoliths. The temporary decrease in transmittance and increase in haze observed experimentally during drying of the monoliths could be explained by light scattering by growing dry domains forming within the monolith. Finally, optical interferometry was demonstrated as a robust and simple alternative to ellipsometry for measuring the film thickness, effective refractive index, and total porosity of non-absorbing multicomponent mesoporous thin films.

Miscible carbon dioxide (CO2) flooding is a well-established and promising enhanced oil recovery (EOR) technique whereby residual oil is recovered by mixing with injected CO2 gas. However, CO2, being very light and less viscous than reservoir crude oil, results in inefficient sweep efficiency. Extensive research is ongoing to improve CO2 mobility control such as the development and generation of CO2/water foams. The long-term stability of foam during the period of flooding is a known issue and must be considered during the design stage of any CO2 foam flooding project. The foam stability can be improved by adding surfactants as stabilizers, but surfactants generated foams have generally a shorter life because of an unstable interface. Furthermore, surfactants are prone to higher retention and chemical degradation in the porous media, particularly under harsh reservoir conditions. Research has shown that nanoparticles (NPs) can act as an excellent stabilizing agent for CO2/water foams owing to their surface chemistry and high adsorption energy. The foams generated using NPs are more stable and provide better mobility control compared to surfactant-stabilized foams. One limitation of using NPs as foam stabilizers is their colloidal stability which limits the use of low-cost NPs. Combining surfactants and NPs for CO2 foam stabilization is a novel approach and has gained interest among researchers in recent years. Surfactants improve the dispersion of NPs in the aqueous phase and minimize particle aggregation. NPs on the other hand create a stable barrier at the CO2/water interface with the help of surfactants, thus generating highly stable and viscous foams. This paper presents a comprehensive review of the basic principles and applications of stabilized CO2 foams. A brief overview of CO2 foam flooding is discussed first, followed by a review of standalone surfactant-stabilized and NPs-stabilized CO2/water foams. The application of hybrid surfactant-NPs stabilized CO2 foams is then presented and areas requiring further investigation are highlighted. This review provides an insight into a novel approach to stabilize CO2/water foams and the effectiveness of the method as proved by various studies.

ZnTiO3 was supported on quartz microspheres to reduce ZnTiO3 particle aggregation and to enhance the photocatalytic activity of ZnTiO3. The distribution of ilmenite phase ZnTiO3 on quartz microspheres was found to reduce the ZnTiO3 crystallite size from 40.4 nm to 19.9 nm. The commonly large ZnTiO3 particles in pure ZnTiO3 can hardly exist in χZnTiO3/SiO2 composites. The bandgap energy of ZnTiO3 is enlarged after support on quartz microspheres. The bandgap energies of 20ZnTiO3/SiO2, 50ZnTiO3/SiO2, 80ZnTiO3/SiO2 and pure ZnTiO3 were determined to be 3.42, 3.38, 3.08 and 2.93 eV, respectively. The pore volume and the BET surface area of χZnTiO3/SiO2 composites were several times larger than that for both quartz microsphere and ZnTiO3. The hole-electron recombination efficiency is reduced after supporting the ZnTiO3 on quartz microspheres. The photocatalytic activity of χZnTiO3/SiO2 composites is in the sequence 50ZnTiO3/SiO2 > 80ZnTiO3/SiO2 > 20ZnTiO3/SiO2 > ZnTiO3. The RBR X-3B degradation rate constants for ZnTiO3, 20ZnTiO3/SiO2 and 50ZnTiO3/SiO2 were determined to be 0.01016, 0.02271 and 0.02653 min−1, respectively. The RBR X-3B degradation efficiency in the presence of 50ZnTiO3/SiO2 reaches 91.7% after 80 min of reaction.

With the demand for manufacturing large (e.g., 450 mm) wafers, problems arise due to temperature increases associated with the chemical mechanical polishing (CMP) process. Various methods have been employed to stabilize the in-situ polishing temperature. The use of a high-temperature slurry can improve the removal rate, but a degradation in surface morphology occurs during the copper CMP procedure. To explain this mechanism, the effects of temperature on the slurry, CMP pad, and copper wafer were separately investigated. A temperature of approximately 40 °C was demonstrated to be a suitable choice when considering polishing efficiency and quality, thereby facilitating the rapid production of semiconductors. Particle aggregation was also observed with a rise in temperature. The work presented here may allow for a reduction in defects during low-hardness material polishing.

In the flotation of finely disseminated iron ores, fine hematite and gangue minerals (mainly quartz) always co-exist in the pulp, their higher interface energies would cause complex interfacial interactions and aggregations. Thus, particle aggregation characteristics in hematite-quartz systems with sodium oleate (NaOL) were studied in this research. The focused beam reflectance measurement (FBRM) and Zeta potential distribution analyses revealed that quartz and hematite particles formed hetero-aggregates at pH 5.0–7.0, while NaOL would weaken the hetero-aggregation by inducing the aggregate formation of hematite particles. The adsorption and contact angle tests indicated that hetero-aggregation inhibition could be attributed to oleate ion (OL−) adsorption onto hematite surfaces, which changed the surface charge and hydrophobic characteristics. Theoretical calculations demonstrated that the hydrophobic interactions among hematite particles, rendered hydrophobic by NaOL, were the main cause of hematite particles forming large aggregates.

Crystallization experiments performed with highly supercooled solutions produced highly pure (>99 wt %) and highly crystalline mesocrystals of curcumin from impure solutions (∼22% of two structurally similar impurities) in one step. These mesocrystals exhibited a crystallographic hierarchy and were composed of perfectly or imperfectly aligned nanometer-thick crystallites. X-ray diffraction and spectroscopic analysis confirmed that the spherulites are a new solid form of curcumin. A theoretical hypothesis based on particle aggregation, double nucleation, and repeated secondary nucleation is proposed to explain the spherulite formation mechanism. The experimental results provide, for the first time, evidence for an organic molecule to naturally form spherulites without the presence of any stabilizing agents. Control experiments performed with highly supercooled pure solutions produced spherulites, confirming that the formation of spherulites is attributed to the high degree of supercooling and not due to the presence of impurities. Likewise, control experiments performed with a lower degree of supercooling produced impure crystals of curcumin via classical molecular addition mechanisms. Collectively, these experimental observations provide, for the first time, evidence for particle-mediated crystallization as an alternate and efficient method to purify organic compounds.

Evaporation-induced particle aggregation in drying droplets is of significant importance in the prevention of pathogen transfer due to the possibility of indirect fomite transmission of the infectious virus particles. In this study, particle aggregation was directionally controlled using contact line dynamics (pinned or slipping) and geometrical gradients on microstructured surfaces by the systematic investigation of the evaporation process on sessile droplets and sprayed microdroplets laden with virus-simulant nanoparticles. Using this mechanism, we designed robust particle capture surfaces by significantly inhibiting the contact transfer of particles from fomite surfaces. For the proof-of-concept, interconnected hexagonal and inverted pyramidal microwall were fabricated using ultraviolet-based nanoimprint lithography, which is considered to be a promising scalable manufacturing process. We demonstrated the potentials of an engineered microcavity surface to limit the contact transfer of particle aggregates deposited with the evaporation of microdroplets by 93% for hexagonal microwall and by 96% for inverted pyramidal microwall. The particle capture potential of the interconnected microstructures was also investigated using biological particles, including adenoviruses and lung-derived extracellular vesicles. The findings indicate that the proposed microstructured surfaces can reduce the indirect fomite transmission of highly infectious agents, including norovirus, rotavirus, or SARS-CoV-2, via respiratory droplets.

High-performance electrode materials are developed for flexible Li-ion batteries (FLIBs) and multifunctional electronic devices. In order to solve the problem of particle aggregation and large interfacial resistance in graphene/tin oxide (SnO2) flexible electrode, ultrathin SnO2 nanorods (NR) are used to fabricate freestanding graphene/SnO2-NR (GNS/SnO2-NR) paper electrode. Owing to the superior lithium storage behavior, the short diffusion length of Li+, and uniform dispersion of SnO2-NR, the GNS/SnO2-NR exhibits high reversible capacity (940 mAh g−1), excellent rate capability (625 mAh g−1 at 2000 mA g−1), and superior cyclic stability. Moreover, the FLIBs assembled with GNS/SnO2-NR paper electrodes can show high specific capacity and excellent cycle stability even in the state of long-term deformation. The structural design tactics point out a promising direction for the realization of mechanically compliant, ultra-stable FLIBs for the next-generation power hungry flexible/wearable electronic devices.

Providing a suitable method for predicting the effect of particle aggregation on photovoltaic (PV) performance can be one of the best ways to make better use of solar energy. In this study, a mathematical method was used and modified to provide a better prediction of angular losses coefficient ( α r ). The modified coefficient as well as a computational method were used to find the performance of dusty modules equipped with one-axis (East-West (EW), North-South (NS)), and dual-axis (DAT) solar tracking systems. The modified α r , which here is called the degree of surface dirtiness, can be used to estimate the area covered by particles per cm 2 , i.e. A ∗ C ( θ ) . A better prediction of α r causes a better prediction of power loss due to dust settlement. Results showed that A ∗ C ( θ ) is the factor that shows the role of incidence angle in visualizing the type of dust cover, while α r shows the effect of slope angle on dust deposition density. Furthermore, combination of α r with the computational model revealed that the dirty DAT module has the least daily power loss which is 9% of the clean counterpart power. The power losses for the NS and EW dusty modules are 13% and 20.5% lower than the clean counterparts, respectively. It should be noted that the obtained results in this study are in a good compromise with the experimental and computational data available in the literature.

Lipid-based nanoparticles for RNA delivery (LNP-RNA) are revolutionizing the nanomedicine field, with one approved gene therapy formulation and two approved vaccines against COVID-19, as well as multiple ongoing clinical trials. As for other innovative nanopharmaceuticals (NPhs), the advancement of robust methods to assess their quality and safety profiles—in line with regulatory needs—is critical for facilitating their development and clinical translation. Asymmetric-flow field-flow fractionation coupled to multiple online optical detectors (MD-AF4) is considered a very versatile and robust approach for the physical characterisation of nanocarriers, and has been used successfully for measuring particle size, polydispersity and physical stability of lipid-based systems, including liposomes and solid lipid nanoparticles. However, the unique core structure of LNP-RNA, composed of ionizable lipids electrostatically complexed with RNA, and the relatively labile lipid-monolayer coating, is more prone to destabilization during focusing in MD-AF4 than previously characterised nanoparticles, resulting in particle aggregation and sample loss. Hence characterisation of LNP-RNA by MD-AF4 needs significant adaptation of the methods developed for liposomes. To improve the performance of MD-AF4 applied to LNP-RNA in a systematic and comprehensive manner, we have explored the use of the frit-inlet channel where, differently from the standard AF4 channel, the particles are relaxed hydrodynamically as they are injected. The absence of a focusing step minimizes contact between the particle and the membrane, reducing artefacts (e.g. sample loss, particle aggregation). Separation in a frit-inlet channel enables satisfactory reproducibility and acceptable sample recovery in the commercially available MD-AF4 instruments. In addition to slice-by-slice measurements of particle size, MD-AF4 also allows to determine particle concentration and the particle size distribution, demonstrating enhanced versatility beyond standard sizing measurements.

Conversion/alloying type anodes have shown great promise for sodium-ion batteries (SIBs) because of their high theoretical capacity. However, the poor structural stability derived from the large volume expansion and short lifetime impedes their further practical applications. Herein, we report a novel anode with a pomegranate-like nanostructure of SnP₂O₇ particles homogeneously dispersed in the robust N-doped carbon matrix. For the first time, we make use of in situ self-nanocrystallization to generate ultrafine SnP₂O₇ particles with a short pathway of ions and electrons to promote the reaction kinetics. Ex situ transmission electron microscope (TEM) shows that the average particle size of SnP₂O₇ decreases from 66 to 20 nm successfully based on this unique nanoscale-engineering method. Therefore, the nanoparticles together with the N-doped carbon contribute a high pseudocapacitance contribution. Moreover, the N-doped carbon matrix forms strong interaction with the self-nanocrystallization ultrafine SnP₂O₇ particles, leading to a stable nanostructure without any particle aggregation under a long-cycle operation. Benefiting from these synergistic merits, the SnP₂O₇@C anode shows a high specific capacity of 403 mAh g–¹ at 200 mA g–¹ and excellent cycling stability (185 mAh g–¹ after 4000 cycles at 1000 mA g–¹). This work presents a new route for the effective fabrication of advanced conversion/alloying anodes materials for SIBs.

The assembly of colloidal particles into ordered structures is of great importance to a variety of nanoscale applications where the precise control and placement of particles is essential. A fundamental understanding of this assembly mechanism is necessary to not only predict, but also to tune the desired properties of a given system. Here, we use constructal theory to develop a theoretical model to explain this mechanism with respect to van der Waals and double layer interactions. Preliminary results show that the particle aggregation behavior depends on the initial lattice configuration and solvent properties. Ultimately, our model provides the first constructal framework for predicting the self-assembly of particles and could be expanded upon to fit a range of colloidal systems.

The inhalation of nitric oxide (NO), which acts as a selective vasodilator of pulmonary blood vessels, is an established medical treatment. However, its wide adoption has been limited by the lack of a convenient delivery technique of this unstable gas. Here we report that a solid mixture of FeIISO4·7H2O and a layered double hydroxide (LDH) containing nitrite (NO2-) in the interlayer spaces (NLDH) stably generates NO at a therapeutic level (∼40 ppm over 12 h from freshly mixed solids; ∼80 ppm for 5-10 h from premixed solids) under air flow (0.25 L min-1) if the NLDH has been prepared by using a reconstruction method. Mg/Al-type LDH was calcined at 550 °C to remove interlayer CO32- and then treated with NaNO2 in water to reconstruct the NLDH. This one-pot, organic solvent-free process can be performed at large scales and is suitable for mass production. Humid air promotes anion exchange between NO2- and SO42- in the solid mixture, resulting in persistent interactions of NO2- and Fe2+, generating NO. In contrast to the previously reported NLDH prepared using an anion-exchange method, the reconstructed NLDH exhibits stable and persistent generation of NO because of partial deformation of the layered structures (e.g., particle aggregation, reduced crystallinity, and enhanced basicity). Degradation of the solid mixture is suppressed under dry conditions, so that a portable cartridge column that is readily available as an NO source for emergency situations can be prepared. This work demonstrates that the interlayer nanospace of LDH serves as a reaction mediator for excellent controllability of solid-state reactions. This inexpensive and disposable NO generator will facilitate NO inhalation therapy in developing countries and nonhospital locations.

The adsorption and foaming properties of an edible colloidal nanoparticle (EYPNs), self-assembled from the food-derived, amphiphilic egg yolk peptides, were investigated, with the aim of evaluating their potential as efficient particulate stabilizers for development of aqueous food foams. The influence of particle aggregation induced by the changes of environmental conditions (mainly the pH) on these properties of EYPN systems was determined. Our results showed that the EYPNs are a highly pH-responsive system, showing the pH-dependent particle aggregation behavior, which is found to strongly affect the interfacial adsorption and macroscopic foaming behaviors of systems. Compared to high pH (6.0–9.0), the EYPNs at low pH (2.0–5.0) showed higher surface activity with a lower equilibrated surface tension as well as a higher packing density of particles and particle aggregates at the interface, probably due to the reduced electrostatic adsorption barrier. Accordingly, the EYPNs at these low pH values exhibited significantly higher foamability and foam stability. The presence of large particle clusters and/or aggregates formed at low pH in the continuous phase may contribute to the foam stability of EYPNs. These results indicate that our edible peptide-based nanoparticle EYPNs can be used as a new class of Pickering-type foam stabilizer for the design of food foams with controlled material properties, which may have sustainable applications in foods, cosmetics, and personal care products., Graphical abstract Image 1, Highlights • Edible nanoparticle EYPNs are efficient particulate stabilizers for making food foams. • EYPNs have a pH-dependent particle aggregation behavior in aqueous solutions. • The particle aggregation strongly affects the adsorption and foaming properties. • The presence of particle aggregates contributes to the foam stability of EYPNs. • The particle aggregates show higher surface activity and interfacial packing density.

Severe particle aggregation and performance fading hinder the application of Mn-based chalcogenides (MBCs) in sodium-ion batteries, and most modifications focus on complicated structure design. Wit...

The power conversion efficiency of perovskite solar cells, which are next-generation photovoltaic cells, has rapidly increased up to 20% through ongoing research and development. Recently, various methods have been employed to increase the active area of the mesoporous layer in perovskite solar cells. In this study, the particle aggregation of the TiO2 was controlled by adding Ti-diisopropoxide bis to the mesoporous layer solution; thus, the contact area between the mesoporous layer and perovskite layer was increased. The amount of Ti-diisopropoxide bis added to the mesoporous layer solution was adjusted to prevent the inhibition of electron transport caused by separation of particles and instability of mesoporous layer. To evaluate the changes in the characteristics of the perovskite solar cells due to the TiO2 particle aggregation in the mesoporous layer, X-ray diffraction and spectrophotometric absorbance, as well as cross-sectional and surface scanning electron microscopy measurement were performed, and the current density–voltage curve, power conversion efficiency and other properties were evaluated under solar simulator. It was found that the mesoporous layer was improved due to its enlarged contact area, and hence, can be expected to improve the efficiency of perovskite solar cells.

The copper sulfide precipitation is a selective and efficient method for the recovery or removal of metals. However, the suspension behavior, and particularly the aggregation performance of generated precipitates, is still under investigation. In this context, the current work focuses on the assessment of the aggregation size evolution of copper sulfide precipitates at different operational conditions, based on FBRM. This method can measure non-invasive, in-situ and real-time the particle aggregation evolution in a suspension. A copper sulfide precipitation reaction was carried out using an experimental design varying pH, sulfide dosage, and copper concentration in the feed solution. The copper concentration had the most significant effect on the aggregates size, showing a high aggregation behavior above 1000 mg/L Cu, instead 200 mg/L where this tendency was negligible. This study is the first one to use FBRM in copper precipitates and its results can be used to support future studies to improve solid-liquid separation processes.

Drug therapy for vascular disease has been promoted to inhibit angiogenesis in atherosclerotic plaques and prevent restenosis following surgical intervention. This paper investigates the arterial depositions and distribution of PEG-functionalized magnetic nanocomposite clusters (PEG_MNCs) following local delivery in a stented artery model in a uniform magnetic field produced by a regionally positioned external permanent magnet; also, the PEG_MNCs aggregation or chain formation in and around the implanted stent. The central concept is to employ one external permanent magnet system, which produces enough magnetic field to magnetize and guide the magnetic nanoclusters in the stented artery region. At room temperature (25 °C), optical microscopy of the suspension model’s aggregation process was carried out in the external magnetic field. According to the optical microscopy pictures, the PEG_MNC particles form long linear aggregates due to dipolar magnetic interactions when there is an external magnetic field. During magnetic particle targeting, 20 mL of the model suspensions are injected (at a constant flow rate of 39.6 mL/min for the period of 30 s) by the syringe pump in the mean flow (flow velocity is Um = 0.25 m/s, corresponding to the Reynolds number of Re = 232) into the stented artery model. The PEG_MNC clusters are attracted by the magnetic forces (generated by the permanent external magnet) and captured around the stent struts and the bottom artery wall before and inside the implanted stent. The colloidal interaction among the MNC clusters was investigated by calculating the electrostatic repulsion, van der Waals and magnetic dipole-dipole energies. The current work offers essential details about PEG_MNCs aggregation and chain structure development in the presence of an external magnetic field and the process underlying this structure formation.