Template Dissolution Interfacial Patterning of Single Colloids for Nanoelectrochemistry and Nanosensing

Abstract

Deterministic positioning and assembly of colloidal nanoparticles (NPs) onto substrates is a core requirement and a promising alternative to top down lithography to create functional nanostructures and nanodevices with intriguing optical, electrical, and catalytic features. Capillaryassisted particle assembly (CAPA) has emerged as an attractive technique to this end, as it allows controlled and selective assembly of a wide variety of NPs onto predefined topographical templates using capillary forces. One critical issue with CAPA, however, lies in its final printing step, where high printing yields are possible only with the use of an adhesive polymer film. To address this problem, we have developed a template dissolution interfacial patterning (TDIP) technique to assemble and print single colloidal AuNP arrays onto various dielectric and conductive substrates in the absence of any adhesion layer, with printing yields higher than 98%.The TDIP approach grants direct access to the interface between the AuNP and the target surface, enabling the use of colloidal AuNPs as building blocks for practical applications. The versatile applicability of TDIP is demonstrated by the creation of direct electrical junctions for electro-and photoelectrochemistry and nanoparticle-on-mirror geometries for single particle molecular sensing.

Nanoimprint Lithography Facilitated Plasmonic‐Photonic Coupling for Enhanced Photoconductivity and Photocatalysis

“…Further, the technique forbids the system to be influenced by the refractive index of the adhesive layer and provides full access to the colloid surface in contrast to the previous CAPA. [ 33 ] The sphere is a choice of shape because of its minimal surface contact with the substrate. Once adapted for spherical morphology, other isotropic geometries (i.e., nanocubes) thus become more feasible because of their enhanced surface contact area with the target substrate.…”

“…[ 63 ] Here, we show the decomposition of the dye with the visible light photon energies, which is well below the band‐gap of TiO 2. The work‐function of Au, conduction and valance band of bulk TiO 2 , [ 65 ] the redox potential of MO in solution, [ 66 ] and the reaction mechanisms are shown in Figure 4e. To measure the oxidation rate of the dye, we avoided exposure to the ambient light, while the sample was illuminated by the broadband halogen lamp together with the LED sources at fixed angles.…”

“…In a recent article, similar issues have been raised in a different way. [ 33 ] There can be several strategies to tackle this issue; one such solution may be to directly synthesize photoconductive polymer coatings around the plasmonic building block. [ 70 ] Further, in heterogeneous colloidal engineering, [ 71 ] conductive ligands can also be used as an anchor group to attach organic ligands.…”

“…To mitigate some of the issues, a recent method of template dissolution interfacial patterning (TDIP) has been introduced. [ 33 ] Yet, this method is affected by various process parameters such as longer assembly duration, contact angle, humidity, temperature, dew point, and other environmental factors. On the other hand, nanoimprint lithography (NIL) has already shown its potential to overcome most of the contemporary challenges such as commercialization of the technique, on‐chip pattering, lower consumption of stamp material with multiple usages of stamps.…”

Instant interfacial self-assembly for homogeneous nanoparticle monolayer enabled conformal “lift-on” thin film technology

“…Spontaneously, self-assembly of molecules or particles into 2D/3D architectures ( 11 , 12 ) has emerged as an effective thin film process with advantages such as low cost, good compatibility with existing technology, and minimal infrastructure requirements. Recent development of 2D nanoparticle (NP) assemblies with surface tunability ( 13 ) enables promising application opportunities such as skin-like multifunctional wearable systems ( 14 ). Further explorations have focused on improving the efficiency to construct 2D thin films, through destabilization-based assembly ( 15 ), external-force assistance ( 16 ), and chemical linker–induced assembly ( 17 ).…”