Single-Molecule Tunneling Sensors for Nitrobenzene Explosives.

The tunneling current through the single-molecule junctions principally offers the ultimate solution for chemical and biochemical sensing via the interactions between probes and target analytes at the single-molecule level. However, it remains unexplored to achieve the sensitive and selective detection of targeted analytes using single-molecule junction techniques due to the challenge in quantitative evaluation of sensing sensitivity and selectivity. Herein, we demonstrate a single-molecule tunneling sensor for the highly sensitive and selective detection of nitrobenzene explosives using scanning tunneling microscope break junction (STM-BJ). Taking advantage of π-π stacking interactions between the molecular probes and nitrobenzene explosives, we use a spectral clustering algorithm to assign the signal of probes and π-stacked probes for sensitively detecting the targeted analytes and the distinguishable conductance change of probes when interacting with different nitroaromatic explosive compounds for selective detection. We find that pronounced conductance changes up to 0.8 orders of magnitude when the probes interact with TNT. Also, we obtain a sensitivity of up to ∼10 pM for TNT and high sensitivity for eight TNT analogues. Combined with theoretical calculations, we discover that the harness of the destructive quantum interference of the probe M1OH after interacting with TNT leads to high selectivity in sensing with TNT. Our work demonstrates the great potential of the single-molecule tunneling current for environmental sensing molecules with high selectivity and sensitivity.

Three-Dimensional Printing of Polyaniline/Reduced Graphene Oxide Composite for High-Performance Planar Supercapacitor.

We apply direct ink writing for the three-dimensional (3D) printing of polyaniline/reduced graphene oxide (PANI/RGO) composites with PANI/graphene oxide (PANI/GO) gel as printable inks. The PANI/GO gel inks for 3D printing are prepared via self-assembly of PANI and GO in a blend solvent of N-methyl-2-pyrrolidinone and water, and offer both shaping capability, self-sustainability, and electrical conductivity after reduction of GO. PANI/RGO interdigital electrodes are fabricated with 3D printing, and based on these electrodes, a planar solid-state supercapacitor is constructed, which exhibits high performance with an areal specific capacitance of 1329 mF cm-2. The approach developed in this work provides a simple, economic, and effective way to fabricate PANI-based 3D architectures, which leads to promising application in future energy and electric devices at micro-nano scale.