Binding of Lignin Nanoparticles at Oil-Water Interfaces: An Ecofriendly Alternative to Oil Spill Recovery

Building Functional Liquid-Based Interfaces: From Mechanism to Application

Functional liquid-based interfaces, with their inhomogeneous regions that emphasize the functionalized liquids, have attracted much interest as a versatile platform for a broad spectrum of applications, from chemical manufacturing to practical uses. These interfaces leverage the physicochemical characteristics of liquids, alongside dynamic behaviors induced by macroscopic wettability and microscopic molecular exchange balance, to allow for tailored properties within their functional structures. In this Minireview, we provide a foundational overview of these functional interfaces, based on the structural investigations and molecular mechanisms of interaction forces that directly modulate functionalities. Then, we discuss design strategies that have been employed in recent applications, and the crucial aspects that require focus. Finally, we highlight the current challenges in functional liquid-based interfaces and provide a perspective on future research directions.

Microplastics and Co-pollutants in soil and marine environments: Sorption and desorption dynamics in unveiling invisible danger and key to ecotoxicological risk assessment

Microplastics (MPs) and their co-pollutants pose significant threats to soil and marine environments, necessitating understanding of their colonization processes to combat the plastic pandemic and protect ecosystems. MPs can act as invisible carriers, concentrating and transporting pollutants, leading to a more widespread and potentially toxic impact than the presence of either MPs or the pollutants alone. Analyzing the sorption and desorption dynamics of MPs is crucial for understanding pollutants amplification and predicting the fate and transport of pollutants in soil and marine environments. This review provides an in-depth analysis of the sorption and desorption dynamics of MPs, highlighting the importance of considering these dynamics in ecotoxicological risk assessment of MPs pollution. The review identifies limitations of current frameworks that neglect these interactions and proposes incorporating sorption and desorption data into robust frameworks to improve the ability to predict ecological risks posed by MPs and co-pollutants in soil and marine environments. However, failure to address the interplay between sorption and desorption can result in underestimation of the true impact of MPs and co-pollutants, affecting livelihoods and agro-employments, and exacerbate poverty and community disputes (SDGs 1, 2, 3, 8, 9, and 16). It can also affect food production and security (SDG 2), life below water and life on land (DSGs 14 and 15), cultural practices, and natural heritage (SDG 11.4). Hence, it is necessary to develop new approaches to ecotoxicological risk assessment that consider sorption and desorption processes in the interactions between the components in the framework to address the identified limitations.

In Situ Engineering of Conducting Polymer Nanocomposites at Liquid/Liquid Interfaces: A Perspective on Fundamentals to Technological Significance

The conducting polymers have continuously been hybridized with their counterparts to overcome the intrinsic functional limitations compared to the metallic or inorganic analogs. Remarkably, the liquid/liquid interface-assisted methods represent an efficient and facile route for developing fully tunable metamaterials for various applications. The spontaneous adsorption of nanostructures at a quasi-two-dimensional interface is energetically favorable due to the reduction in interfacial tension, interfacial area, and interfacial energy (Helmholtz free energy). This Perspective highlights the fundamentals of nanostructure adsorption leading to hierarchical architecture generation at the interface from an experimentalist's point of view. Thereafter, the essential applications of the conducting polymer/nanocomposites synthesized at the interface emphasize the capability of the interface to tune functional materials. This Perspective also summarizes the future challenges and the use of the known fundamental aspects in overcoming the functional limitations of polymer/nanomaterial composites and also provides some future research directions.

Interfacial Activity and Surface pKa of Perfluoroalkyl Carboxylic Acids (PFCAs)

Perfluoroalkyl carboxylic acids (PFCAs) are widely used synthetic chemicals that are known for their exceptional stability and interfacial activity. Despite their industrial and environmental significance, discrepancies exist in the reported pKa values for PFCAs, often spanning three to four units. These disparities stem from an incomplete understanding of how pH influences the ionized state of PFCA molecules in the bulk solution and at the air-water interface. Using pH titration and surface tension measurements, we show that the pKa values of the PFCAs adsorbed at the air-water interface differ from the bulk. Below the equivalence point, the undissociated and dissociated forms of the PFCAs exist in equilibrium, driving to the spontaneous adsorption and reduced air-water surface tension. Conversely, above the equivalence point, the complete ionization of the headgroup into the carboxylate form renders PFCAs highly hydrophilic, resulting in reduced interfacial activity of the molecules. The distinction in the chemical environments at the interface and bulk results in differences in the pKa of PFCA molecules in the bulk phase and at the air-water interface. We explore the effects of the fluoroalkyl tail length of PFCAs on their surface pKa and interfacial activity across a broad pH range. We further demonstrate the influence of pH-dependent ionized state of PFCAs on their foamability and the rate of microdroplet evaporation, understanding of which is crucial for optimizing their industrial applications and developing effective strategies for their environmental remediation. This study underscores the potential significance of pH in directing the interfacial activity of PFCAs and prompts the inclusion of pH as a key determinant in the predictions of their fate and potential risks in the environment.

Interaction of impinging marangoni fields

HYPOTHESIS

Surface tension gradient driven Marangoni flows originating from multiple sources are important to many industrial and medical applications, but the theoretical literature focuses on single surfactant sources. Understanding how two spreading surfactant sources interact allows insights from single source experiments to be applied to multi-source applications. Two key features of multi-source spreading - source translation and source deformation - can be explained by transport modeling of a two-source system.

MODELING

Numerical simulations of two oleic acid disks placed at varying initial separation distances on a glycerol subphase were performed using COMSOL Multiphysics and compared to spreading of a single surfactant source.

FINDINGS

Interaction of two spreading sources can be split into three regimes: the independent regime - where each source is unaffected by the other, the interaction regime - where the presence of a second source alters one or more features of the spreading dynamics, and the quasi-one disk regime - where the two sources merge together. The translation of the sources, manifested as increasing separation distance between disk centers of mass, is driven by the flow fields within the subphase and the resultant surface deformation, while deformation of the sources occurs only once the surfactant fronts of the two sources meet.

Uptake and release of perfluoroalkyl carboxylic acids (PFCAs) from macro and microplastics

Microplastics and per- and polyfluoroalkyl substances (PFAS) are two of the most notable emerging contaminants reported in the environment. Micron and nanoscale plastics possess a high surface area-to-volume ratio, which could increase their potential to adsorb pollutants such as PFAS. One of the most concerning sub-classes of PFAS are the perfluoroalkyl carboxylic acids (PFCAs). PFCAs are often studied in the same context as other environmental contaminants, but their amphiphilic properties are often overlooked in determining their fate in the environment. This lack of consideration has resulted in a diminished understanding of the environmental mobility of PFCAs, as well as their interactions with environmental media. Here, we investigate the interaction of PFCAs with polyethylene microplastics, and identify the role of environmental weathering in modifying the nature of interactions. Through a series of adsorption-desorption experiments, we delineate the role of the fluoroalkyl tail in the binding of PFCAs to microplastics. As the number of carbon atoms in the fluoroalkyl chain increases, there is a corresponding increase in the adsorption of PFCAs onto microplastics. This relationship can become modified by environmental weathering, where the PFCAs are released from the macro and microplastic surface after exposure to simulated sunlight. This study identifies the fundamental relationship between PFCAs and plastic pollutants, where they can mutually impact their thermodynamic and transport properties.

Synergistic Role of Temperature and Salinity in Aggregation of Nonionic Surfactant-Coated Silica Nanoparticles

The adsorption of nonionic surfactants onto hydrophilic nanoparticles (NPs) is anticipated to increase their stability in aqueous medium. While nonionic surfactants show salinity- and temperature-dependent bulk phase behavior in water, the effects of these two solvent parameters on surfactant adsorption and self-assembly onto NPs are poorly understood. In this study, we combine adsorption isotherms, dispersion transmittance, and small-angle neutron scattering (SANS) to investigate the effects of salinity and temperature on the adsorption of pentaethylene glycol monododecyl ether (C₁₂E₅) surfactant on silica NPs. We find an increase in the amount of surfactant adsorbed onto the NPs with increasing temperature and salinity. Based on SANS measurements and corresponding analysis using computational reverse-engineering analysis of scattering experiments (CREASE), we show that the increase in salinity and temperature results in the aggregation of silica NPs. We further demonstrate the non-monotonic changes in viscosity for the C₁₂E₅-silica NP mixture with increasing temperature and salinity and correlate the observations to the aggregated state of NPs. The study provides a fundamental understanding of the configuration and phase transition of the surfactant-coated NPs and presents a strategy to manipulate the viscosity of such dispersion using temperature as a stimulus.

Probing the Mechanism of Targeted Delivery of Molecular Surfactants Loaded into Nanoparticles after Their Assembly at Oil-Water Interfaces

A targeted and controlled delivery of molecular surfactants at oil-water interfaces using the directed assembly of nanoparticles, NPs, is reported. The mechanism of NP assembly at the interface and the release of molecular surfactants is followed by laser scanning confocal microscopy and surface force spectroscopy. The assembly of positively charged polystyrene NPs at the oil-water interface was facilitated by the introduction of carboxylic acid groups in the oil phase (e.g., by adding 1 wt % stearic acid to hexadecane to produce a model oil). The presence of positively charged NPs consistently lowers the stiffness of the water-oil interface. The effect is lessened, when the NPs are present in a solution of NaCl or deionized water at pH 2, consistent with a less dense monolayer of NPs at the interface in the last two systems. In addition, the NPs reduce the interfacial adhesion (i.e., the "stickiness" of the interface or, put differently, the pull-off force experienced by the atomic force microscopy (AFM) tip during retraction). After the assembly, the NPs can release a previously loaded cargo of surfactant molecules, which then facilitate the formation of a much finer oil-water emulsion. As a proof of concept, we demonstrate the release of octadecyl amine, ODA, that has been incorporated into the NPs prior to the assembly. The release of ODA causes the NPs to detach from the interface altering the interfacial properties and leads to finer oil droplets. This approach can be exploited in applications in several fields ranging from pharmaceutical and cosmetics to hydrocarbon recovery and oil-spill remediation, where a targeted and controlled release of surfactants is wanted.

Adsorptive properties and on-demand magnetic response of lignin@Fe3O4 nanoparticles at castor oil-water interfaces

Lignin@Fe₃O₄ nanoparticles adsorb at oil-water interfaces, form Pickering emulsions, induce on-demand magnetic responses to break emulsions, and can sequester oil from water. Lignin@Fe₃O₄ nanoparticles were prepared using a pH-induced precipitation method and were fully characterized. These were used to prepare Pickering emulsions with castor oil/Sudan red G dye and water at various oil/water volume ratios and nanoparticle concentrations. The stability and demulsification of the emulsions under different magnetic fields generated with permanent magnets (0-540 mT) were investigated using microscopy images and by visual inspection over time. The results showed that the Pickering emulsions were more stable at the castor oil/water ratio of 50/50 and above. Increasing the concentration of lignin@Fe₃O₄ improved the emulsion stability and demulsification rates with 540 mT applied magnetic field strength. The adsorption of lignin@Fe₃O₄ nanoparticles at the oil/water interface using 1-pentanol evaporation through Marangoni effects was demonstrated, and magnetic manipulation of a lignin@Fe₃O₄ stabilized castor oil spill in water was shown. Nanoparticle concentration and applied magnetic field strengths were analyzed for the recovery of spilled oil from water; it was observed that increasing the magnetic strength increased oil spill motion for a lignin@Fe₃O₄ concentration of up to 0.8 mg mL^-1 at 540 mT. Overall, this study demonstrates the potential of lignin-magnetite nanocomposites for rapid on-demand magnetic responses to externally induced stimuli.

Interfacial tension driven adsorption of MnO2 nanoparticles at the liquid/liquid interface to tailor ultra-thin polypyrrole sheets

An emerging aspect of research is designing and developing fully tunable metamaterials for various applications with fluid interfaces. Liquid/liquid interface-assisted methods represent an efficient and facile route for synthesizing two-dimensional (2-D) thin films of potential materials. The underlying mechanism behind thin film formation at the liquid/liquid interface involves the preferential adsorption of nano-sized particles at the interface to minimize high interfacial tension. Here, a water/chloroform interface-assisted method is employed for the one-pot synthesis of highly crystalline polypyrrole/manganese dioxide (PPy/MnO₂) sheets. The temporal evolution in the dynamic interfacial tension (from 32 mN m^-1 to 17 mN m^-1) observed in pendant drop tensiometry proved the preferential adsorption of MnO₂ atttached PPy oligomers at the water/chloroform interface. An ultra-thin sheet-like morphology and uniform distribution of ∼6 nm highly crystalline MnO₂ nanoparticles are evidenced by transmission and atomic force microscopy techniques. The predominance of interfacial polymerization in retaining the electrochemical activity of the PPy/MnO₂ sheets is elucidated for the electrochemical detection of nicotine. This study opens a new avenue for the realization of ultra-thin sheets of polymer-nanomaterial hybrids, enabling applications ranging from new classes of sensors to optics.

From residue to resource: new insights into the synthesis of functionalized lignin micro/nanospheres by self-assembly technology for waste resource utilization

Among the most abundant biopolymers in the biosphere, lignin is a renewable aromatic compound that represents an untapped opportunity to create new biological products. However, the complex interlacing structures of cellulose, hemicellulose and lignin, as well as the unique properties of lignin, limit the utilization of value-added lignin. Lignin-based nanomaterials open the door for lignin applications in environmental pollutant remediation, biofuel production, biomedicine, and other fields. Herein, we present various factors influencing the formation of micro-nanospheres by self-assembly techniques through a review of previous literature, and emphasize the simple and green synthesis of lignin micro/nanospheres (LMNPs) under non-modified conditions. More importantly, we discuss the mechanism of the formation of nanospheres. Considering the heterogeneity of lignin and the polarity of different solvents, we propose that self-assembly techniques should focus more on the influence brought by lignin itself or the solvent, so that the external conditions can be controlled to prepare LMNPs, which can be used in specific fields. A brief overview of the contribution of lignin-based nanomaterials in various fields is also presented. This review could provide insight for the development of lignin-based nanomaterials.

Biopolymer-based nanocarriers for sustained release of agrochemicals: A review on materials and social science perspectives for a sustainable future of agri- and horticulture

Devastating plant diseases and soil depletion rationalize an extensive use of agrochemicals to secure the food production worldwide. The sustained release of fertilizers and pesticides in agriculture is a promising solution to the eco-toxicological impacts and it might reduce the amount and increase the effectiveness of agrochemicals administration in the field. This review article focusses on carriers with diameters below 1 μm, such as capsules, spheres, tubes and micelles that promote the sustained release of actives. Biopolymer nanocarriers represent a potentially environmentally friendly alternative due to their renewable origin and biodegradability, which prevents the formation of microplastics. The social aspects, economic potential, and success of commercialization of biopolymer based nanocarriers are influenced by the controversial nature of nanotechnology and depend on the use case. Nanotechnology's enormous innovative power is only able to unfold its potential to limit the effects of climate change and to counteract current environmental developments if the perceived risks are understood and mitigated.

Recent Developments in the Formulation and Use of Polymers and Particles of Plant-based Origin for Emulsion Stabilizations

The main scope of this Review was the recent progress in the use of plant-based polymers and particles for the stabilization of Pickering and non-Pickering emulsion systems. Due to their availability and promising performance, it was discussed how the source, modification, and formulation of cellulose, starch, protein, and lignin-based polymers and particles would impact their emulsion stabilization. Special attention was given toward the material synthesis in two forms of polymeric surfactants and particles and the corresponding formulated emulsions. Also, the effects of particle size, degree of aggregation, wettability, degree of substitution, and electrical charge in stabilizing oil/water systems and micro- and macro-structures of oil droplets were discussed. The wide range of applications using such plant-based stabilizers in different technologies as well as their challenge and future perspectives were described.

Fluorescent visualization of oil displacement in a microfluidic device for enhanced oil recovery applications

A microfluidic device was developed to mimic the reservoir pore-scale and track the oil/water phases during air flooding. The chip was generated by combining soft-lithography and NOA81 replication. A unique feature of this approach is the inclusion of fluorescent dyes into the oil/water phases, allowing for real-time visualization of oil recovery without altering the phases' surface properties. As a proof of concept, the air was injected into the water/oil-flooded device for enhanced oil recovery applications.

Microplastics through the Lens of Colloid Science

Microplastics are sub-millimeter-sized fragments of plastics and a relatively new class of pollutant increasingly found in the environment. Due to their size and surface area to volume ratio, the physicochemical characteristics of microplastics can diverge from those of their macroscopic counterparts. This is partly why it is challenging to understand their origin, analyze their behavior, and predict their fates in the environment compared to large pollutants. We believe that adopting a view of microplastics as a colloid provides a holistic framework that connects their physical properties and surface chemistries with observations of their dynamics in the environment. In particular, we discuss the role of fundamental principles of colloid science in interpreting phenomena of wetting, adsorption, aggregation, and transport of microplastics. Colloid and interface science can provide the tools to couple or decouple the physicochemical behaviors of microplastics, which may aid in understanding the environmental challenge both from a fundamental perspective and with respect to practical remediation methods.

Tailoring renewable materials via plant biotechnology

Plants inherently display a rich diversity in cell wall chemistry, as they synthesize an array of polysaccharides along with lignin, a polyphenolic that can vary dramatically in subunit composition and interunit linkage complexity. These same cell wall chemical constituents play essential roles in our society, having been isolated by a variety of evolving industrial processes and employed in the production of an array of commodity products to which humans are reliant. However, these polymers are inherently synthesized and intricately packaged into complex structures that facilitate plant survival and adaptation to local biogeoclimatic regions and stresses, not for ease of deconstruction and commercial product development. Herein, we describe evolving techniques and strategies for altering the metabolic pathways related to plant cell wall biosynthesis, and highlight the resulting impact on chemistry, architecture, and polymer interactions. Furthermore, this review illustrates how these unique targeted cell wall modifications could significantly extend the number, diversity, and value of products generated in existing and emerging biorefineries. These modifications can further target the ability for processing of engineered wood into advanced high performance materials. In doing so, we attempt to illuminate the complex connection on how polymer chemistry and structure can be tailored to advance renewable material applications, using all the chemical constituents of plant-derived biopolymers, including pectins, hemicelluloses, cellulose, and lignins.

Lignin Nanoparticles: Promising Sustainable Building Blocks of Photoluminescent and Haze Films for Improving Efficiency of Solar Cells

Films with the capacity for photoluminescence and haze, which can convert UV to visible light and enhance light management, are of great importance for optoelectronic devices. Here, taking advantage of the inherent fluorescence and self-assembly properties of lignin, we have developed a sustainable lignin-derived multifunctional dopant (L-MS-NPs) for fabricating optical films with haze, fluorescence, and room-temperature phosphorescence (RTP) together with poly(vinyl alcohol) (PVA). The optical films are used to improve the light-harvesting efficiency of solar cells. Specifically, attributed to the robust morphology in the film matrix, L-MS-NPs cause a rough morphology in the surface of an L-MS-NPs/PVA composite film, which eventually triggers the great optical haze. Additionally, L-MS-NPs inherit fluorescence properties from lignin and show fluorescence emission when embed in the film matrix. Moreover, the PVA film matrix can stabilize the excited triplet state, which finally induces RTP of L-MS-NPs. The combined haze, fluorescence, and RTP properties of the L-MS-NPs/PVA composite film enhances the power conversion efficiency (PCE) of dye-sensitized solar cells from ∼3.9 to ∼4.1%.

Immediate social and economic impacts of a major oil spill on Brazilian coastal fishing communities

In August 2019, a major oil spill hit nine Brazilian coastal states, affecting marine ecosystems and fishing communities. In this study, we assess the immediate social and economic impacts of this oil spill on fishing communities of the northeast coast. We conducted semi-structured interviews and focal meetings with 381 fishers and shellfish gatherers to understand the perceived socioeconomic impacts on different types of fishing. We also obtained information on fish consumption after the oil spill, which we compared with data prior to the oil spill from the same communities. Sales decreased by more than 50% for all types of fishing, strongly impacting local income generation. These communities, which are already social-ecologically vulnerable, have had their subsistence, food security and cultural maintenance strongly compromised. We argue that there is a clear need for coordinated state interventions to mitigation the impacts, considering it's environmental, social, economic, human health and political dimensions.

Adsorption of Myoglobin and Corona Formation on Silica Nanoparticles

The adsorption of proteins from aqueous medium leads to the formation of protein corona on nanoparticles. The formation of protein corona is governed by a complex interplay of protein-particle and protein-protein interactions, such as electrostatics, van der Waals, hydrophobic, hydrogen bonding, and solvation. The experimental parameters influencing these interactions, and thus governing the protein corona formation on nanoparticles, are currently poorly understood. This lack of understanding is due to the complexity in the surface charge distribution and anisotropic shape of the protein molecules. Here, we investigate the effect of pH and salinity on the characteristics of corona formed by myoglobin on silica nanoparticles. We experimentally measure and theoretically model the adsorption isotherms of myoglobin binding to silica nanoparticles. By combining adsorption studies with surface electrostatic mapping of myoglobin, we demonstrate that a monolayered hard corona is formed in low salinity dispersions, which transforms into a multilayered hard + soft corona upon the addition of salt. We attribute the observed changes in protein adsorption behavior with increasing pH and salinity to the change in electrostatic interactions and surface charge regulation effects. This study provides insights into the mechanism of protein adsorption and corona formation on nanoparticles, which would guide future studies on optimizing nanoparticle design for maximum functional benefits and minimum toxicity.

Plant celluloses, hemicelluloses, lignins, and volatile oils for the synthesis of nanoparticles and nanostructured materials

A huge variety of plants are harvested worldwide and their different constituents can be converted into a broad range of bionanomaterials. In parallel, much research effort in materials science and engineering is focused on the formation of nanoparticles and nanostructured materials originating from agricultural residues. Cellulose (40-50%), hemicellulose (20-40%), and lignin (20-30%) represent major plant ingredients and many techniques have been described that separate the main plant components for the synthesis of nanocelluloses, nano-hemicelluloses, and nanolignins with divergent and controllable properties. The minor components, such as essential oils, could also be used to produce non-toxic metal and metal oxide nanoparticles with high bioavailability, biocompatibility, and/or bioactivity. This review describes the chemical structure, the physical and chemical properties of plant cell constituents, different techniques for the synthesis of nanocelluloses, nanohemicelluloses, and nanolignins from various lignocellulose sources and agricultural residues, and the extraction of volatile oils from plants as well as their use in metal and metal oxide nanoparticle production and emulsion preparation. Furthermore, details about the formation of activated carbon nanomaterials by thermal treatment of lignocellulose materials, a few examples of mineral extraction from agriculture waste for nanoparticle fabrication, and the emerging applications of plant-based nanomaterials in different fields, such as biotechnology and medicine, environment protection, environmental remediation, or energy production and storage, are also included. This review also briefly discusses the recent developments and challenges of obtaining nanomaterials from plant residues, and the issues surrounding toxicity and regulation.

Technological advancement in the synthesis and applications of lignin-based nanoparticles derived from agro-industrial waste residues: A review

Over the years, lignin has drawn a great deal of interest for their potential use as bio-polymers due to the presence of high amount of phenolic compounds, non-polluting feature and cost-competitiveness as compared to synthetic polymers. However, in order to fast-track their development, different attempts are made towards the usage of lignin in nano form since it exhibits some unique properties in nanoscale range. The present review article provides a detail analysis on the recent advancement in the synthesis and applications of lignin nanoparticles (LNPs) derived from agro-industrial waste residues. In view of that, an in-depth morphological analysis was reviewed to assess the structural influence on the characteristics of LNPs. Further, application of LNPs is explored in different fields including bio-medical engineering, pharmaceuticals, skin-care products and food industries. Finally, the paper is concluded discussing various challenges associated with the synthesis, modification and development with an aspiration of futuristic developments. The readers of this review article will be highly benefitted after acquiring a comprehensive knowledge on LNPs and its different synthesis processes along with various applications.

Environmentally friendly rhamnolipid production for petroleum remediation

Biosurfactants have potential applications in the remediation of petroleum-contaminated sites. Several strategies can be used to reduce the production costs of these surfactants and make the process more environmentally friendly. In this study, we combined some of these strategies to produce the rhamnolipid-type biosurfactant, including the use of the genetically modified strain Pseudomonas aeruginosa-estA, an industrial coproduct as a carbon source, a simple and low-cost medium, and a simple downstream process. The process resulted in a high yield (17.6 g L^-1), even using crude glycerin as the carbon source, with substrate in product conversion factor (Y_RML/s) of 0.444. The cell-free supernatant (CFS) was not toxic to Artemia salina and selected mammalian cell lineages, suggesting that it can be used directly in the environment without further purification steps. Qualitative analysis showed that CFS has excellent dispersion in the oil-displacement test, emulsifying (IE₂₄ = 65.5%), and tensoactive properties. When salinity, temperature and pressure were set to seawater conditions, the values for interfacial tension between crude oil and water were below 1.0 mN m^-1. Taken together, these results demonstrate that it is possible to obtain a nontoxic crude rhamnolipid product, with high productivity, to replace petroleum-based surfactants in oil spill cleanups and other environmental applications.

Bio-Based Lignin Nanocarriers Loaded with Fungicides as a Versatile Platform for Drug Delivery in Plants

Lignin-based nano- and microcarriers are a promising biodegradable drug delivery platform inside of plants. Many wood-decaying fungi are capable of degrading the wood component lignin by segregated lignases. These fungi are responsible for severe financial damage in agriculture, and many of these plant diseases cannot be treated today. However, enzymatic degradation is also an attractive handle to achieve a controlled release of drugs from artificial lignin vehicles. Herein, chemically cross-linked lignin nanocarriers (NCs) were prepared by aza-Michael addition in miniemulsion, followed by solvent evaporation. The cross-linking of lignin was achieved with the bio-based amines (spermine and spermidine). Several fungicides-namely, azoxystrobin, pyraclostrobin, tebuconazole, and boscalid-were encapsulated in situ during the miniemulsion polymerization, demonstrating the versatility of the method. Lignin NCs with diameters of 200-300 nm (determined by dynamic light scattering) were obtained, with high encapsulation efficiencies (70-99%, depending on the drug solubility). Lignin NCs successfully inhibited the growth of Phaeomoniella chlamydospora and Phaeoacremonium minimum, which are lignase-producing fungi associated with the worldwide occurring fungal grapevine trunk disease Esca. In planta studies proved their efficiency for at least 4 years after a single injection into Vitis vinifera ("Portugieser") plants on a test vineyard in Germany. The lignin NCs are of high interest as biodegradable delivery vehicles to be applied by trunk injection against the devastating fungal disease Esca but might also be promising against other fungal plant diseases.

Adsorption of Fatty Acid Molecules on Amine-Functionalized Silica Nanoparticles: Surface Organization and Foam Stability

The crucial roles of the ionization state and counterion presence on the phase behavior of fatty acid in aqueous solutions are well-established. However, the effects of counterions on the adsorption and morphological state of fatty acid on nanoparticle surfaces are largely unknown. This knowledge gap exists due to the high complexity of the interactions between nanoparticles, counterions, and fatty acid molecules in aqueous solution. In this study, we use adsorption isotherms, small angle neutron scattering, and all-atom molecular dynamic simulations to investigate the effect of addition of ethanolamine as a counterion on the adsorption and self-assembly of decanoic acid onto aminopropyl-modified silica nanoparticles. We show that the morphology of the fatty acid assemblies on silica nanoparticles changes from discrete surface patches to a continuous bilayer by increasing concentration of the counterion. This morphological behavior of fatty acid on the oppositely charged nanoparticle surface alters the interfacial activity of the fatty acid-nanoparticle complex and thus governs the stability of the foam formed by the mixture. Our study provides new insights into the structure-property relationship of fatty acid-nanoparticle complexes and outlines a framework to program the stability of foams formed by mixtures of nanoparticles and amphiphiles.

Fractionation of alkali lignin by organic solvents for biodegradable microsphere through self-assembly

Here we report a centrifugation-based fractionation methodology that was integrated with three types of organic solvents to fractionate industrial alkali lignin toward the fabrication of lignin microsphere. The Fourier-transform infrared spectroscopy (FT-IR) result showed that the chemical structure of lignin was not changed by solvent fractionation. Soluble lignin in each solvent had lower molecular weight, improved polydispersity index (PDI) and less impurities (S, N), while insoluble lignin had a high bio-char yield and can be utilized as potential carbon source for porous carbon nanosphere materials. In addition, well-shaped lignin microsphere with smooth or anisotropic surface can be prepared by selecting proper lignin fraction without any chemical modification. This work thus provides a new strategy for the derivation of lignin as raw materials for value-added products, which paved a new way to develop a green and sustainable bio-refining industry.