The potential toxicity of existing chemical dispersants on the marine environment has motivated the search for environmentally friendly dispersants with excellent dispersion ability. Here, an effective Pickering emulsifier is developed based on the synergy of natural biopolymer, Xanthan Gum (XG), and silica nanoparticles. The oil−in−seawater emulsion stabilized by a combination of XG and silica demonstrates great stability and smaller droplet size, which is favorable for the following natural degradation of oil. The synergistic emulsification mechanism has been investigated systematically. The presence of XG favors the adsorption of silica nanoparticles at the oil−seawater interface and also is considerably effective in enhancing the viscosity of continuous phase. These contributions of XG slow down the droplet coalescence and creaming significantly. Confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM) images of emulsions indicate a thick layer of aggregated XG/silica particles at the oil− water interface. This thick layer provides an effective steric barrier. In this study, the synergy between XG and silica not only enhances the dispersion effectiveness, but also reduces the amount of nanoparticles dramatically. This finding opens up a new path for the development of a novel, high efficiency, ecologically acceptable, and cheaper dispersant for emulsifying crude oil following a spill.

One remediation technique of oil spills is the application of dispersants to oil slicks, which is essentially a process of emulsification. Tetradecane and crude oil-inseawater emulsions formed with silica nanoparticles modified in situ with rhamnolipid produced a longer stability and smaller droplet size. The interactions of silica particles with rhamnolipid were characterized by contact angle, interfacial tension, TEM, and SEM measurements. The images of confocal fluorescence microscopy and SEM showed the oil droplet microstructure and the morphology of nanoparticles at the oil droplet−water interface. The average emulsion droplet size and emulsion index were investigated. These results indicated a synergistic stabilization upon rhamnolipid addition. The synergy was even more efficient in the case of seawater with a high salinity. Here, because of the strong flocculation caused by high salinity, silica nanoparticles alone were not an effective emulsifier in seawater. The modification of silica nanoparticles by rhamnolipid changed the contact angle and promoted their adsorption at the oil−seawater interface, which provided an efficient barrier to droplet coalescence. The emulsification of rhamnolipid-modified silica nanoparticles worked well in crude oil−seawater system. So, this could be a new method to deal with the issue of the marine oil spill by environmentally benign silica particles and rhamnolipid.

Bacterial infection is one of the major problems for human health. To prevent outbreak of bacteria-caused diseases, early diagnosis of bacterial pathogen and effective destruction of pathogenic microorganisms are in urgent need. In this work, we developed a new multifunctional nanocomposite material that can effectively capture and destroy bacteria. Epoxide-modified nanoparticles were synthesized by microemulsion polymerization and precipitation polymerization. The epoxide groups on the particle surface were reacted with polyethylenimine to introduce cationic amine groups. The amine groups on the nanoparticle surface enhanced the colloidal stability of the particles’ suspension and provided multivalent interactions to bind and destroy the bacteria. After further modification with Ag nanoparticles, the final composite nanomaterial was able to not only capture and destroy Gram-negative bacteria but also allow the bacteria’s fingerprint spectra to be obtained through surface-enhanced Raman scattering. The multifunctional nanoparticles developed in this work offer a new approach toward fast capture, detection, and destruction of pathogenic bacteria.

Composite cryogels containing boronic acid ligands are synthesized for effective separation and isolation of bacteria. The large and interconnected pores in cryogels enable fast binding and release of microbial cells. To control bacterial binding, an alkyne-tagged boronic acid ligand is conjugated to azide-functionalized cryogel via the Cu(I)-catalyzed azide–alkyne cycloaddition reaction. The boronic acid-functionalized cryogel binds Gram-positive and Gram-negative bacteria through reversible boronate ester bonds, which can be controlled by pH and simple monosaccharides. To increase the capacity of affinity separation, a new approach is used to couple the alkyne-tagged phenylboronic acid to cryogel via an intermediate polymer layer that provides multiple immobilization sites. The morphology and chemical composition of the composite cryogel are characterized systematically. The capability of the composite cryogel for the separation of Gram-positive and Gram-negative bacteria is investigated. The binding capacities of the composite cryogel for Escherichia coli and Staphylococcus epidermidis are 2.15 × 10 9 and 3.36 × 10 9 cfu/g, respectively. The bacterial binding of the composite cryogel can be controlled by adjusting pH. The results suggest that the composite cryogel may be used as affinity medium for rapid separation and isolation of bacteria from complex samples.

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