Liquid interfacial plasmonic platform is emerging for new sensors, catalysis, and tunable optical devices, but also promises an alternative for practical applications of surface-enhanced Raman spectroscopy (SERS). Here we show that vigorous mixing of chloroform with citrate-capped gold nanorod sols triggers the rapid self-assembly of three-dimensional plasmonic arrays at the chloroform/water (O/W) interface and produces a self-healing metal liquid-like brilliant golden droplet. The O phase itself generates stable SERS fingerprints and is a good homogeneous internal standard for quantitative analysis. This platform presents reversible O/W encasing in a common cuvette determined just by surface wettability of the container. Both O-in-W and W-in-O platforms exhibit excellent SERS sensitivity and reproducibility for different analytes by the use of a portable Raman device. It paves the way toward a practical and quantitative liquid-state SERS analyzer, likened to a simple UV–Vis spectrometer, that is far superior to typical solid substrate-based or nanoparticle sol-based analysis.

Liquid-state interfacial nanoparticle arrays for surface-enhanced Raman scattering (SERS) promises a practical, substrate-free, and rapid analysis but faces a great challenge to develop a batch and uniform fabrication strategy with stable internal standards (IS) because of the difficulties in precisely locating both the IS tags and analytes in the same local structure under the harsh conditions of biphasic liquid interface. Here, we develop a fast batch preparation of self-ordered dense Au nanoparticle (GNP) arrays on cyclohexane/water biphasic interface in 96-well plates with the assist of acetone as the phase-crossing inducer. The acetone can extract the pesticide molecules via a simple dipping sample peels and can rapidly capture and locate the pesticide molecule into the plasmonic hotspots. Meanwhile, this phase-crossing solvent, acetone itself, generates stable SERS signal and is used as the IS tags to calibrate the signal fluctuation. This platform presents an excellent uniformity with a relative standard deviation (RSD) of 5.9% compared to the RSD of 14.5% without the IS's correction and a good sensitivity with a limit of detection (LOD) of 1 nM thiram. This high-throughput strategy for analyzing pesticide residues at fruit peels reached detection levels of nanograms per square centimeter (ng/cm). Combined with the 96-well plates, this platform greatly facilitates the self-assembly and multiplex sampling. The self-ordered arrays at two immiscible phases interface evidenced the detection of both the oil-soluble thiabendazole and the water-soluble thiram molecules and also realized the multiplex and two-phase detection of these two pesticides. This platform offers vast possibilities for on-site sensing of various analytes and paves a new way for the quantitative and high-throughput SERS analyzer just as convenient as the microplate reader.

A stripping procedure was demonstrated to prepare ultra-smooth gate dielectric for flexible and low-voltage organic phototransistors.

Liquid-state interfacial plasmonic systems are emerging as an alternative for the quantitation and practicability of the surface-enhanced Raman scattering (SERS) technique in analytical science, especially for complex liquid-phase systems. Here we show a general strategy for the three-dimensional (3D) self-assembly of gold nanoparticle (GNP) arrays on a spherical oil−water (O−W) interface, denoted as a plasmonic metal liquid (PML). The PML has excellent self-healing and shape-adaptive features; it can be transferred into containers of any shape; and it presents fast, quantitative, and multiplex SERS capability. Accurate control of nanoparticle density (PD) on the 3D interface enables tunable SERS strength. In situ synchrotron radiation small angle X-ray scattering (SR-SAXS) provides evidence that the interfacial PD is quantifiable and can be precisely regulated in the range of 24−216 particles/μm 2 , which produces optimizable Raman enhancement. The strongest SERS signal is achieved at 167 particles/μm 2 with GNP diameters of approximately 64 nm. In particular, the O phase acts not only as the assembly media for spherical PML arrays but also as the extracting agent for targets with different natures in complex media. Moreover, the O phase with continuous-phase features generates inherent and sharp SERS fingerprints and provides an effective internal standard (IS) for calibrating the fluctuation of samples and measuring conditions. By virtue of the triple roles of the O phase, the PML platform exhibits excellent mechanical stability, detection sensitivity, and signal reproducibility. This study demonstrates the concept of a fast and quantitative liquid-state SERS platform in common cuvettes on a portable Raman device that is as simple as a spectrophotometer.

The quality and safety of edible oils is a momentous but formidable challenge, especially regarding identification of oil type, oxidation, and adulteration. Most conventional analytical methods have bottlenecks in sensitivity, specificity, accessibility, or reliability. Surface-enhanced Raman spectroscopy (SERS) is promising as an unlabeled and ultrasensitive technique but limited by modification of inducers or surfactants on metal surfaces for oil analysis. Here, we develop a quantitative SERS analyzer on two-liquid interfacial plasmonic arrays for direct quality classification of edible oils by a portable Raman device. The interfacial plasmonic array is self-assembled through mixing the gold nanoparticle (GNP) sols and oil sample dissolved in chloroform without any surfactants or pretreatments. Different kinds of edible oils dissolved in chloroform directly participate in self-assembly of plasmonic arrays that finally localizes onto a three-dimensional (3D) oil/water interface. The 3D plasmonic array is self-healing, shape adaptive, and can be transferred to any glass containers as a substrate-free SERS analyzer for direct Raman measurements. It produces sensitive responses of SERS on different kinds of edible oils. By virtue of principal component analysis (PCA), this analyzer is able to quickly distinguish six edible oils, oxidized oils, and adulterated oils. Moreover, the solvent chloroform generates unique and stable SERS bands that can utilized as an inherent internal standard (IIS) to calibrate SERS fluctuation and greatly improve quantitation accuracy. Compared to conventional lab methods, this analyzer avoids complex and time-consuming preprocessing and provides significant advantages in cost, speed, and utility. Our study illuminates a facile way to determine edible oil quality and promises great potential in food quality and safety analysis.