Quasi-solid-state optical logic devices based on redox polymer nanosheet assembly

We report fabrication of a quasi-solid-state optical logic gate based on a polymer nanosheet photodiode. Two amphiphilic copolymers, p(DDA/Ru) and p(DDA/Fc), which respectively have a ruthenium dipyridyl complex and a ferrocene derivative as a redox molecule, are synthesized to produce redox polymer nanosheets. To construct polymer nanosheet photodiodes, two redox polymer nanosheets were assembled onto an indium-tinoxide (ITO) electrode in a tailor-made manner. The ITO electrode was connected with a counter electrode using an agarose gel electrolyte. The simple two-electrode system performs as a quasi-solid-state polymer nanosheet photodiode (QS-PNP). The photocurrent flow direction of QS-PNP can be controlled to be anodic or be cathodic by changing the deposition order of the redox polymer nanosheets. The anodic and cathodic QS-PNPs were applied to construct optical OR and XOR logic gates. The OR logic gate was fabricated by connecting the anodic and cathodic QS-PNP in a series; XOR logic was fabricated by connecting two anodic QS-PNPs in series. In optical logic gates, excitations of p(DDA/Ru) were used as input signals, and photocurrent was used as an output signal. These optical logic gates operate in a quasi-solid-state in a simple two-electrode configuration, which facilitates integration of the logic elements.

Chemical Approaches to Molecular Logic Elements for Addition and Subtraction

Molecular and supramolecular logic gates are candidates for computation at the nanoscale level. Nowadays all common logic operations can be mimicked with molecular devices based on chemical approaches. One step further towards molecular systems with increased logic capabilities is the addition or subtraction of binary digits. This Minireview describes recent developments to attain this goal, including bioinspired systems based on DNA and enzymes. Furthermore, chemical molecular logic gates are discussed and compared critically with regard to alternative concepts.

Two coupled enzymes perform in parallel the ‘AND’ and ‘InhibAND’ logic gate operations

The coupled activation of two enzymes: glucose dehydrogenase (GDH) and horseradish peroxidase (HRP), is used to construct the parallel-operating AND and InhibAND logic gates. The added substrates for the respective enzymes, glucose and H(2)O(2), act as the gate inputs, while the biocatalytically generated NADH and gluconic acid provide the output signals that follow the operations of the gates. The two gates are generated in the same vial, thus allowing the logic operations to take place in parallel, and the simultaneous readout of the functions of the gates.