Au Nanoparticles Immobilized on Honeycomb-Like Polymeric Films for Surface-Enhanced Raman Scattering (SERS) Detection

Abstract

Abstract:We have successfully developed novel surface-enhanced Raman scattering (SERS) substrates with three-dimensional (3D) porous structures for effectively improving the sensitivity and reproducibility of SERS, which can rapidly detect small molecules (rhodamine 6G as an example). Periodical arrays of the honeycomb-like substrates were fabricated by self-assembling polyurethane-co-azetidine-2,4-dione (PU-PAZ) polymers. PU-PAZ comprising amphiphilic dendrons could stabilize the phase separation between the water droplets and polymer solution, and then organize into regular porous structures during the breath figure method. Subsequently, SERS substrates were fabricated by immobilizing gold nanoparticles (AuNPs) onto the honeycomb-like films with various 3D porous structures, controlled by the different PU-PAZ concentrations and relative humidities. Results show that surface enhancement factors of honeycomb-like substrates were 20 times higher than that of flat-film substrates (control group) due to enormous hot-spots resonance effects by the 3D porous structure, verified through Raman mapping at various positions of the z-axis. Furthermore, the particle size effects were evaluated by immobilized 12 and 67 nm of AuNPs on the honeycomb-like substrates, indicating larger AuNPs could induce more pronounced hot-spots effects. The generation of hot-spots resonance to enhance Raman intensity is strongly dependent on the diameter of AuNPs and the pore size of the honeycomb-like and 3D porous substrates for label-free and rapid SERS detection.

In Search of a Green Process: Polymeric Films with Ordered Arrays via a Water Droplet Technique

“…Amphiphilic poly(urea/malonamide) dendritic materials have been developed by Jeng et al since 2006 [25,26,27,28,29,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61]. In the midst of them, the honeycomb-like films were obtained based on PSs covalently bonded with different sizes of dendritic side chains (in chloroform) (Figure 4).…”

“…In recent years, polymeric honeycomb-like films via the BF process have received lots of scientific attention, especially in pursuit of practical applications [4,5,9,10,11,12,13,14,16,63]. These applications are classified in several fields, such as templating [64,65], surface-enhanced Raman scattering (SERS) [49,66,67,68,69,70], biomedical researches [43,71], electronic devices [72,73,74,75,76,77], etc. The ordered array films could serve as the templates to transfer certain patterns for polymers which are not easy to prepare directly by the BF method.…”

Organic Electrochemical Transistors/SERS-Active Hybrid Biosensors Featuring Gold Nanoparticles Immobilized on Thiol-Functionalized PEDOT Films

“…Gold nanoparticles (AuNPs) are particularly attractive nanomaterials for electrochemical biosensing because of their efficient signal amplification, good stability, and outstanding biocompatibility in electrolyte solutions. Although AuNPs can ensure SERS detection with improved signal reproducibility and lower toxicity, AuNP-based SERS-active substrates have lower enhancement factors (EFs) than do those incorporating silver nanoparticles (AgNPs) (Ou et al, 2014; Chiang et al, 2017). To reverse the gap between the SERS signals of AuNP- and AgNP-active substrates, electromagnetic hot spots can be further created through well-controlled AuNP aggregation, resulting in greater EFs from SERS-active substrates (Guerrini and Graham, 2012; Ou et al, 2014; Yang et al, 2016; Chiang et al, 2017).…”

“…Nevertheless, manipulation of the uniform aggregation of AuNPs over large areas remains a key challenge when creating hot spots on SERS-active substrates (Shiohara et al, 2014). In fact, three-dimensional (3D) SERS-active substrates have recently be found to create high-density hot spots under laser illumination; because they possess large specific surface areas for the immobilization of more AuNPs and the absorption of more target analytes, such systems might solve the problem of intrinsically weak Raman signals (Lee et al, 2012; Liu et al, 2014; Chiang et al, 2017).…”

Honeycomb Surface with Shape Memory Behavior Fabricated via Breath Figure Process

“…Poly(urea/malonamide) dendrons have been utilized for fabricating honeycomb‐like structures through the BF process . The hexagonal array of micropores could be achieved by either grafting dendrons onto the side groups of polymers or blending dendrons with polymers.…”