3D Assembly of Metal Nanoparticles at Oleic Acid/Water Interface via Their Autonomous and Rapid Interfacial Locomotion

Abstract

The assembly of colloidal metal nanoparticles at immiscible liquid interface has attracted considerable attention because of both enhanced physical properties associated with the assembly and controlled mass transfer at the interface for many sensing and catalytic applications. However, rapid production of 3D assembly of metal nanoparticles at liquid interface is still challenging. Here a facile and robust method is proposed to generate 3D assembly of colloidal metal nanoparticles at oleic acid/water interface, which is based on an interesting observation of the autonomous and rapid interfacial locomotion of nanoparticles from air/water to oleic acid/water interface. This interfacial transfer of these particles is completed within a minute considerably owing to electrostatic interaction between positively charged surface molecule of the particle and the negative end of oleic acid, producing up to 20‐fold denser 3D assembly. To realize one of the benefits of the proposed method, 3D assemblies of gold and silver nanoparticles at oleic acid/water interface are successfully exploited for the detection of trace molecules in both oil and water phases via surface‐enhanced Raman spectroscopy. Molecular Raman signals can be increased by our 3D nanoparticle layers by up to 100 times, compared with that measured from nanoparticle monolayers being transferred onto solid substrates.

Water-Wettable Open Plasmonic Nanocavities for Ultrasensitive Molecular Detections in Multiple Phases

“…In all cases, two Raman transitions for 2-NT are observed at 1076 and 1381 cm −1 corresponding to C−H bending and ring stretching, respectively (Figure 4b). 28 To quantitatively compare the signal enhancements of the substrates, we analyzed the peak areas for both Raman transitions (Figure 4c). The peak areas measured from AuNRon-Si wafer (i) and AuNR with site-selectively grown SiO 2 -on-Si wafer (iii) are similar to each other.…”

“…The substrates are immersed in an ethanolic solution, in which 2-NT is dissolved and subsequently washed for the Raman scattering measurements. In all cases, two Raman transitions for 2-NT are observed at 1076 and 1381 cm –1 corresponding to C–H bending and ring stretching, respectively (Figure b) . To quantitatively compare the signal enhancements of the substrates, we analyzed the peak areas for both Raman transitions (Figure c).…”

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

“…Organic semiconductors are the most adapted active materials for OECTs because their performance to transport charge and host ions can be designed at will by molecular structure. OECTs are ideally suited for biological interfacing because of their stability in aqueous electrolytes, cytocompatibility, facile biofunctionalization, and sterilization by autoclaving . OECTs have evidently been used in logic circuits, some also integrating OFETs .…”

Self-assembly of colloidal nanoparticles into 2D arrays at water–oil interfaces: rational construction of stable SERS substrates with accessible enhancing surfaces and tailored plasmonic response

“…Moreover, since the chemical composition of the oil is unimportant, as long as it provides a high energy interface with water for self-assembly, a variety of organic solvents can be used as the oil phase, which provides an extremely versatile SERS platform, especially for studying dipolar analyte molecules with low solubility in water. [69][70][71][72][73][74][75] For example, Liu et al showed that six edible oils can be distinguished using SERS and interfacial 2D Au nanoparticle arrays as enhancing substrates (Figure 6c). [72] Moreover, they showed that oxidation and adulteration of the edible oils could also be detected with the assistance of principle component analysis.…”