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
Recently, reticular materials, such as metal−organic frameworks and covalent organic frameworks, have been proposed as an active insulating layer in resistive switching memory systems through their chemically tunable porous structure. A resistive random access memory (RRAM) cell, a digital memristor, is one of the most outstanding emergent memory devices that achieves high-density electrical information storage with variable electrical resistance states between two terminals. The overall design of the RRAM devices comprises an insulating layer sandwiched between two metal electrodes (metal/insulator/metal). RRAM devices with fast switching speeds and enhanced storage density have the potential to be manufactured with excellent scalability owing to their relatively simple device architecture. In this review, recent progress on the development of reticular material-based RRAM devices and the study of their operational mechanisms are reviewed, and new challenges and future perspectives related to reticular material-based RRAM are discussed.
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.
Polymorphism control of the titanyl-phthalocyanine (TiOPc) single crystals by molecule-surface interactions and their effects of crystallographic structural differences on photo-electronics.
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