Controlled Interfacial Permeation, Nanostructure Formation, Catalytic Efficiency, Signal Enhancement Capability, and Cell Spreading by Adjusting Photochemical Cross-Linking Degrees of Layer-by-Layer Films

A layer-by-layer strategy for the scalable preparation of uniform interfacial electrocatalysts with high structural tunability: a case study of a CoNP/N,P-graphene catalyst complex

Electrocatalysts are important for providing clean energy and have attracted intense research attention. All electrocatalysts must function on electrode surfaces; however, interfacial engineering strategies for electrocatalytic structures remain understudied, and scalable preparation methods are especially rare. In this study, we propose a strategy that employs a layer-by-layer (LbL) assembly, subsequent in-film deposition, and calcination to prepare a complex Co nanoparticle (CoNP)/N,P-graphene catalyst on various 2D and 3D electrode surfaces. We delicately adjusted a variety of parameters and demonstrated that our LbL-based method can finely tune the total amount, the doping fraction, and the electronic structure of the complex catalysts, and provide optimal catalytic performance. When prepared on a large piece of carbon cloth, the catalysts showed a highly uniform catalytic performance, demonstrating the capability of our method for scalable fabrication. Our study emphasizes the delicate nature of the interfacial engineering of electrocatalysts, and promotes functional interface design and mechanism studies.

Using a Graphene-Polyelectrolyte Complex Reducing Agent To Promote Cracking in Single-Crystalline Gold Nanoplates

It is a challenge to produce single-crystalline gold nanoparticles having regular size definition designed for controlled light absorbance and internal structural inhomogeneities to enhance electro-magnetic fields. Here, we report a synthetic strategy to generate large single-crystalline triangular or hexagonal gold nanoplates with multiple cracks within the plates using a graphene-polyelectrolyte complex as both a surface adsorbent and bulk reducing agent. Large-scale gold nanoplates can be synthesized within 48 h. First-principles calculations indicate that the nanoplates have a kinetically limited morphology resulting from prior growth of {111} facets confined by the graphene-polyelectrolyte multilayer. The nanocracks result from the inability of the bulk reducing agent to enter narrow defect spaces during growth that remained permanently. The nanoplates had extraordinary physical-chemical detection sensitivity when used for surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA). The limit of rhodamine 6G (Rh6G) SERS detection is as low as 5 × 10^-13 M. The gold nanoplates also showed a remarkable light-to-heat conversion efficiency (68.5%). The approach described may be applicable to other metals so that tunable nanostructures can be generated by the graphene-polyelectrolyte multilayer strategy.

Oil-Repellent Antifogging Films with Water-Enabled Functional and Structural Healing Ability

Healable oil-repellent antifogging films are fabricated by layer-by-layer assembly of hyaluronic acid (HA) and branched poly(ethylenimine) (bPEI), followed by immersion in the aqueous solutions of perfluorooctanesulfonic acid potassium salt (PFOS). The loading of PFOS endows the HA/bPEI films with oil repellency while maintaining its original hydrophilicity. The resulting films have an excellent antifogging ability, and various organic liquids can easily slide down the slightly tilted films (<10°) without any residue. Through water-assisted migration of PFOS and polyelectrolytes, oil-repellent antifogging films are able to repetitively and autonomously recover their damaged oil repellency and transparency caused by plasma etching, cutting, or scratching, prolonging their life span. The as-developed healable oil-repellent antifogging films have potential application as antifingerprint coatings for touch screens, antigraffiti coatings for signs and shop windows, and antifogging coatings for lenses, mirrors, and windshields.