Guangzhao Zhang

Nanobubbles are promising in environmental, agricultural, biomedical, and manufacturing settings, but quantitative measurement of the interfacial charge thought to underlie their unusual stability remains difficult. Here, we introduce holographic micro-coulometry (Holo-σ), which combines in-line digital holographic microscopy with microfluidic electrophoresis for in situ analysis of individual nanobubbles. Hologram reconstruction is used to verify that tracked objects are gaseous nanobubbles rather than solid particles and to follow the same object in three dimensions under field-free and applied-field conditions. These trajectories yield hydrodynamic diameter and electrophoretic mobility, from which zeta potential and surface charge density are determined. Benchmarking with Au, polystyrene, and silica standards shows good agreement with commercial electrophoretic light scattering. Applied to confirmed nanobubbles, Holo-σ resolves bubble-to-bubble charge heterogeneity, reveals an inverse relationship between surface charge density and bubble size, and quantifies electrolyte-dependent changes in the surface charge density and zeta potential. Holo-σ thus provides a practical route for single-nanobubble electrokinetic measurements.

Marine biofouling on the surface of underwater equipment severely impairs its operation. Conventional antifouling coatings can prevent biofouling; however, the removal of failed or temporary coatings during equipment repair is difficult and may damage the equipment surface. Herein, we report an antifouling coating consisting of polyaspartic ester-based polyurea modified with secondary amine oligosiloxane nanoclusters (NSs) as a crosslinker and a diisocyanate-terminated reactive amphiphilic polymer (RAP). In the resulting slow-curing polyurea coating, the RAP with low-surface-energy fluorinated side chains and polyethylene glycol (PEG) side chains migrates to the coating surface during drying, allowing PEG to inhibit biofouling. The coating demonstrates satisfactory adhesion strength (2–8 MPa) on diverse substrates, including steel, ceramic, copper, glass, and epoxy panels, as well as >90% reduction in fibrinogen adsorption and relative bacterial adhesion values below 10% against S. aureus, E. coli, and P. sp. In addition, the coating exhibits high cohesive strength and moderate interface adhesion. As a result, it can be readily peeled from various surfaces with a peel strength of 1–9 N·cm–1 without damaging the equipment surface. This polyurea coating demonstrates promising application potential as an antibiofouling coating for marine environments.

Precise control over molar mass and structure of polysiloxane is critical for its applications. Here, we report ring‐opening polymerization (ROP) of cyclotrisiloxane using anionized 1,3‐diphenylurea (UA1) as the catalyst. With a bulky tetra‐ n ‐butylammonium counterion, UA1 shows significantly higher activity than the one with an alkali metal counterion. Almost 100% monomer conversion can be reached in minutes at catalyst loadings of 5–100 ppm (TOF up to 52,000 h ⁻¹ for D ₃ ). The obtained polydimethylsiloxane has well‐defined structure, controlled molar mass (2 to 140 kg mol ⁻¹ ), and low dispersity (1.06–1.18). Calculations reveal that both silanol species and the monomer are hydrogen‐bonded with the catalyst. The dominance of this associative pathway facilitates ring opening and prevents the formation of overly active (dissociated) silanolate anion, thus ensuring high efficiency and selectivity. The catalyst is also applicable to the ROP of non‐strained cyclotetrasiloxane (D ₄ ), with molar mass reaching as high as 1,660 kg mol ⁻¹ . This study paves the route for efficient and controlled synthesis of polysiloxane materials using minimum amount of simple organocatalyst.

Precise control over molar mass and structure of polysiloxane is critical for its applications. Here, we report ring‐opening polymerization (ROP) of cyclotrisiloxane using anionized 1,3‐diphenylurea (UA1) as the catalyst. With a bulky tetra‐ n ‐butylammonium counterion, UA1 shows significantly higher activity than the one with an alkali metal counterion. Almost 100% monomer conversion can be reached in minutes at catalyst loadings of 5–100 ppm (TOF up to 52,000 h ⁻¹ for D ₃ ). The obtained polydimethylsiloxane has well‐defined structure, controlled molar mass (2 to 140 kg mol ⁻¹ ), and low dispersity (1.06–1.18). Calculations reveal that both silanol species and the monomer are hydrogen‐bonded with the catalyst. The dominance of this associative pathway facilitates ring opening and prevents the formation of overly active (dissociated) silanolate anion, thus ensuring high efficiency and selectivity. The catalyst is also applicable to the ROP of non‐strained cyclotetrasiloxane (D ₄ ), with molar mass reaching as high as 1,660 kg mol ⁻¹ . This study paves the route for efficient and controlled synthesis of polysiloxane materials using minimum amount of simple organocatalyst.

Thermoset polymers have found a number of applications. However, their recycling faces a challenge due to their chemically crosslinked structure, which brings environmental pollution. Introduction of dynamic disulfide linkages can overcome this obstacle in principle. Yet, the disulfide compounds used to build the dynamic bonds are very limited and expensive, making their practical applications rather difficult. In this study, we present copolymer of elemental sulfur (S ₈ ) and acrylate with controlled disulfide linkages synthesized via anionic hybrid copolymerization (AHCP). Such a copolymer can serve as a curing agent for conventional thermosetting resins including epoxy, polyurethane, and unsaturated polyester. The resulting thermoset demonstrates remarkable reprocessability, retaining over 86% of its maximum stress and strain at break after five cycles of processing at 120°C and pressure of 10 MPa. It also exhibits strong UV‐blocking capability with zero transmittance in the ultraviolet range. Particularly, the thermoset is recyclable. Namely, it can degrade into oligomers in the presence of S ₈ , which can be reused as curing agents for new thermosets or directly employed as robust adhesives for diverse substrates. The precise synthesis of polymer with controlled disulfide linkages provides a platform to transform conventional thermosets into high‐performance recyclable materials.

Thermoset polymers have found a number of applications. However, their recycling faces a challenge due to their chemically crosslinked structure, which brings environmental pollution. Introduction of dynamic disulfide linkages can overcome this obstacle in principle. Yet, the disulfide compounds used to build the dynamic bonds are very limited and expensive, making their practical applications rather difficult. In this study, we present copolymer of elemental sulfur (S ₈ ) and acrylate with controlled disulfide linkages synthesized via anionic hybrid copolymerization (AHCP). Such a copolymer can serve as a curing agent for conventional thermosetting resins including epoxy, polyurethane, and unsaturated polyester. The resulting thermoset demonstrates remarkable reprocessability, retaining over 86% of its maximum stress and strain at break after five cycles of processing at 120°C and pressure of 10 MPa. It also exhibits strong UV‐blocking capability with zero transmittance in the ultraviolet range. Particularly, the thermoset is recyclable. Namely, it can degrade into oligomers in the presence of S ₈ , which can be reused as curing agents for new thermosets or directly employed as robust adhesives for diverse substrates. The precise synthesis of polymer with controlled disulfide linkages provides a platform to transform conventional thermosets into high‐performance recyclable materials.

Microparticles abundant in marine and aquatic environments can readily deposit on surfaces and influence the biofouling development there. So far, the impacts of micrometer scale particles on bacterial adhesion, including most sediments and cellular debris, remain unclear. By using digital holographic microscopy for real-time 3D bacterial tracking, we have investigated the interaction of Pseudomonas aeruginosa (PAO1) near surface deposited with particles having diameter of 0.5 to 8.0 μm sparsely distributed on the glass substrate. It reveals that the bacterial adhesion is reduced for all the particle-decorated surfaces compared with flat surface and shows size dependence with minimum adhesion on surfaces deposited with 5.0 μm particle. In addition, the near-surface motions of PAO1 are greatly changed by the microparticles. PAO1 speeds up with more continuous climbing and leveling as it approaches the particle. Flow simulation demonstrates that a deposited particle alters the local flow depending on its size, where a 5.0 μm particle has the shortest-range flow disruption. Anyhow, the hydrodynamic interaction between particles and bacteria is responsible for the near-surface bacterial motions. The present study provides a basis for designing marine antifouling materials.

Titanium (Ti) or Ti alloy pipelines have been increasingly used in seawater cooling systems of marine facilities and offshore equipments due to their high corrosion resistance, specific strength, and fatigue resistance. However, their good biocompatibility renders them high susceptibility to marine biofouling, which can block the pipeline system and reduce its cooling efficiency. Self‐fabricated coating is presented based on poly( N ‐isopropylacrylamide) (PNIPAM) to combat marine biofouling in titanium seawater pipeline systems. When PNIPAM solution in seawater is applied onto the Ti surface by flushing, PNIPAM chains would be adsorbed on the inner wall of the pipe and self‐fabricate into a coating due to the coordination interactions between nitrogen in PNIPAM and Ti as well as the hydrophobic interactions from hydrocarbon moieties of PNIPAM. Self‐fabrication is confirmed by quartz crystal microbalance with dissipation, X‐ray photoelectron spectroscopy, and atomic force microscopy. The coating exhibits good anti‐biofouling with ≈99% antibacterial rate, while it does not reduce the corrosion resistance of titanium. The coating can serve more than 10 days at a flow velocity of 0.3 m s ⁻¹ and continue to work once it is regenerated by flushing the PNIPAM solution. This study provides a facile approach to protect the titanium pipeline from marine biofouling.