Designed Patterning of Mesoporous Metal Films Based on Electrochemical Micelle Assembly Combined with Lithographical Techniques

Abstract

Mesoporous noble metals and their patterning techniques for obtaining unique patterned structures are highly attractive for electrocatalysis, photocatalysis, and optoelectronics device applications owing to their expedient properties such as high level of exposed active locations, cascade electrocatalytic sites, and large surface area. However, patterning techniques for mesoporous substrates are still limited to metal oxide and silica films, although there is growing demand for developing techniques related to patterning mesoporous metals. In this study, the first demonstration of mesoporous metal films on patterned gold (Au) substrates, prefabricated using photolithographic techniques, is reported. First, different growth rates of mesoporous Au metal films on patterned Au substrates are demonstrated by varying deposition times and voltages. In addition, mesoporous Au films are also fabricated on various patterns of Au substrates including stripe and mesh lines. An alternative fabrication method using a photoresist insulating mask also yields growth of mesoporous Au within the patterning. Moreover, patterned mesoporous films of palladium (Pd) and palladium–copper alloy (PdCu) are demonstrated on the same types of substrates to show versatility of this method. Patterned mesoporous Au films (PMGFs) show higher electrochemically active surface area (ECSA) and higher sensitivity toward glucose oxidation than nonpatterned mesoporous Au films (NMGF).

Electroinduced Surfactant Self-Assembly Driven to Vertical Growth of Oriented Mesoporous Films

“…For example, we demonstrated successful electrodeposition of an oriented mesoporous film of a uniform thickness of 80 nm onto a streaked gold electrode originating from a recordable CD (Au CD-trode, with base bands of 1-μm width separated by stripes of 0.5-μm width and 100 nm height), fitting exactly the substrate morphology at the nanometric scale contrary to a similar film prepared by classical spin-coating for which the streaked geometry is almost invisible after deposition (Figure A). This can be also applied to other supports of various sizes and shapes, such as microfibers, microporous inverse opal-like substrates, or even exfoliated graphite supports. , Another attractive feature of EASA is the possibility to form patterned mesoporous silica thin films at the microscale (using an ultramicroelectrode to locally generate the hydroxyl catalyst, see Figure B), offering an alternative to the use of lithographical techniques (otherwise applied to patterning of oriented mesoporous metal films, for instance) . Hierarchical macro-mesoporous films can be also prepared by EASA through polystyrene bead assemblies while maintaining the vertical orientation throughout the membrane (Figure C) …”

“…30,31 Another attractive feature of EASA is the possibility to form patterned mesoporous silica thin films at the microscale (using an ultramicroelectrode to locally generate the hydroxyl catalyst, see Figure 3B), 32 offering an alternative to the use of lithographical techniques (otherwise applied to patterning of oriented mesoporous metal films, for instance). 33 Hierarchical macro-mesoporous films can be also prepared by EASA through polystyrene bead assemblies while maintaining the vertical orientation throughout the membrane (Figure 3C). 34 EASA can be applied to oriented film deposition, either potentiostatically or galvanostatically, 1 on various conducting surfaces of different natures (Au, Pt, Cu, several C materials, indium or fluoride-doped tin oxide electrodes (ITO, FTO), or Si wafers).…”

Synthesis of Uniformly Sized Mesoporous Silver Films and Their SERS Application

“…Still, metal aggregation occurs when the deposition time is extended. 13,27 Until 600 s, no aggregation of Ag was observed (Figure 3c), and a small amount of aggregated Ag grains was observed at 1000 s (Figure 3d). Figure 3e presents the sketch of the MAgF growth by the deposition time.…”

Electrochemical Synthesis of Mesoporous Architectured Ru Films Using Supramolecular Templates

“…Moreover, it is also possible to fabricate patterned substrates by modifying the surface conductivity of the substrates. [ 43 ] Since Ru is a precious metal and not abundant, the usage should be restricted to small‐area applications such as microdevice supercapacitors, which is desirable for our modern society demanding various portable devices. However, traditional powder‐state supercapacitor materials are quite difficult to be loaded on such microscale devices, and preparing mesoporous materials on the pattering is much more challenging.…”