Drop-casting and inkjet printing are virtually the most versatile and cost-effective methods for depositing active materials on surfaces. However, drawbacks associated with the coffee-ring effect, as well as uncontrolled aggregation of the coating materials, have impeded the use of these methods for applications requiring high control of film properties. We now report on a simple method based on covalent cross-linking of monodisperse materials that enables the formation of thin films with homogeneous thicknesses and macroscale cohesion. The coffee-ring effect is impeded by triggering gelation of the coating materials via a thioacetate–disulfide transition which counterbalances the capillary forces induced by evaporation. Aggregates are prevented by monodisperse building blocks that ensure that the resulting gel resists sedimentation until complete droplet drying. This combined strategy yields an unprecedented level of homogeneity in the resulting film thickness in the 100 nm to 10 μm range. Moreover, macroscale cohesion is preserved as evidenced by the long-range charge transfer within the matrix. We highlight the impact of this method with bioelectrocatalysts for H₂ and NADPH oxidation. Peak catalytic performances are reached at about 10-fold lower catalyst loading compared to conventional approaches owing to the high control on film cohesion and thickness homogeneity, thus setting new benchmarks in catalyst utilization.

中文翻译：

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通过单分散材料的原位凝胶化防止咖啡环效应和聚集体沉降†

滴铸和喷墨印刷实际上是在表面沉积活性材料的最通用且最具成本效益的方法。然而，与咖啡环效应相关的缺点以及涂层材料不受控制的聚集阻碍了这些方法在需要高度控制薄膜性能的应用中的使用。我们现在报告一种基于单分散材料共价交联的简单方法，该方法能够形成具有均匀厚度和宏观内聚力的薄膜。咖啡环效应通过硫代乙酸盐-二硫化物转变触发涂层材料的凝胶化而受到阻碍，该转变抵消了蒸发引起的毛细管力。单分散结构单元可以防止聚集，确保所得凝胶在液滴完全干燥之前不会沉淀。这种组合策略在 100 nm 至 10 μm 范围内产生的薄膜厚度达到了前所未有的均匀性。此外，矩阵内的长程电荷转移证明了宏观尺度的内聚力得到了保留。_{我们强调了该方法对生物电催化剂对 H 2}和 NADPH 氧化的影响。由于对薄膜内聚力和厚度均匀性的高度控制，与传统方法相比，催化剂负载量降低约 10 倍即可达到峰值催化性能，从而为催化剂利用树立了新的基准。