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Surface-enhanced Raman scattering (SERS) technique is a label-free and nondestructive technique that is used to identify fingerprint information of molecules in various fields such as biology, [1] chemistry, [2] and environment. [3] Noble metals such as gold and silver possessing coarse surfaces have been used as efficient and active materials for solid SERS, static liquid SERS, and dynamic liquid SERS substrates. [4-6] However, the detection of analytes with low concentrations in realtime is challenging particularly in the static liquid phase due to a small number of analytes in a close contact with the metallic surface. Recent studies have alternatively focused on dynamic liquid SERS substrates such as SERS-integrated microfluidic systems, where analytes encounter the SERS substrate with a higher frequency than in conventional static liquid systems. [7-10] Therefore, more reliable and reproducible Raman signals can be achieved for analytes with low concentrations. Such microfluidic SERS systems

The water-level time series of a tidal river is influenced by various factors and has a complex structure, which limits its use as hydrological forecast data. This study proposes a methodology for decomposing the water-level time series of a tidal river into various components that influence the water level. To this end, the tide, wave, rainfall-induced runoff and noise components were selected as the main components that affect the water-level time series. The tide component and the wave component were first separated through wavelet analysis and curve fitting and then they were removed from the water-level data. A high-pass filter was then applied to the resulting time series to separate the rainfall-induced runoff component and the noise component. These methods made it possible to determine the rate of influence that each component has on the water level of a tidal river. The results could be used as a basis for calibrating a rainfall-runoff model and issuing flood forecasts and warnings for a tidal river.

Although the unique optical signaling properties of polydiacetylene (PDA) have been exploited in diverse bio-chemosensors, the practical application of most PDA sensor systems is limited by their instability in harsh environments and fluorescence signal weakness. Herein, a universal design principle for a highly stable PDA sensor system with a practical dual signaling capability is developed to detect cyanide (CN) ions, which are commonly found in drinking water. Effective metal intercalation and enhanced hydrophobic intermolecular interactions between PDA–metal supramolecules are used to construct highly stacked PDA–metal nanoplates that feature unusual optical stability upon exposure to strong acids, bases, organic solvents, and thermal/mechanical stresses, and can selectively detect CN anions, concomitantly undergoing a specific supramolecular structure change. To realize the practical dual signaling capability of the PDA sensor system, upconverting nanocrystals (UCNs) are incorporated into highly stacked PDA–metal nanoplates, and practical dual signaling (orthogonal changes in luminescence and visible color) is demonstrated using a portable detection system. The presented universal design principle is expected to be suitable for the development of other highly stable and selective PDA sensor systems with practical dual signaling capability.

The design and fabrication of solar-to-chemical energy conversion devices are enabled through interweaving multiple components with various morphologies and unique functions using a versatile layer-by-layer assembly method. Cationic and anionic polyelectrolytes are used as an electrostatic adhesive to assemble the following functional materials: plasmonic Ag nanoparticles for improved light harvesting, upconversion nanoparticles for utilization of nearinfrared light, and polyoxometalate water oxidation catalysts for enhanced catalytic activity. Polyelectrolytes also have an additional function of passivating the surface recombination centers of the underlying photoelectrode. These functional components are precisely assembled on a model photoanode (e.g., Fe 2 O 3 and BiVO 4 ) in a desired order and various combinations without degradation of their intrinsic properties. As a result, the performance of water oxidation photoanodes is synergistically enhanced. This study can enable the design and fabrication of novel solar-to-chemical energy conversion devices.