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Molecular logic devices with different functions can perform various tasks in the areas of biological molecule detection, disease diagnosis, multivariate analysis, and bioimaging. Herein, a series of logic circuits based on silver nanoclusters (AgNCs)/graphene oxide (GO) are constructed to execute nonarithmetic functions, including 3-, 4-, and 5-bit odd/even checking. The resulting devices can differentiate between even and odd decimal numbers in the range from 0 to 31. Moreover, the devices can be expanded to operate with wider ranges of numbers when more inputs are added. The signal reporter is structured using AgNCs and GO, preventing laborious modification of biomolecules. The designed DNA-based logic nanodevices share the same DNA platform and a constant threshold value, showing great potential for application in information processing at the molecular level. Additionally, these devices can stably carry out their logic operations in a biological matrix, indicating that the AgNC/GO-based system can operate in a complicated biological environment. Given the biocompatibility and design flexibility of DNA, this study provides novel outcomes towards the development of label-free intelligent nanodevices. This may open a new path for the application of AgNCs/GO in molecular logic circuits and fluorescence imaging.

A silver nanoclusters (AgNCs)/graphene oxide (GO)-based fluorescence sensor was developed for label-free DNA detection through hybridization chain reaction (HCR). A DNA sequence associated with the human immunodeficiency virus (HIV) was selected as a model target. Two DNA probes, hairpin probe 1 (H 1 ) and hairpin probe 2 (H 2 ), were partially complementary. GO was used as an adsorption material to capture the hairpin probes and a selective fluorescence quencher was used to reduce the background signal. Upon addition of AgNO 3 and NaBH 4 , the AgNCs were synthesized at the terminals of the H 1 and H 2 probes. In the absence of target DNA (T HIV ), hybridization chain reaction (HCR) could not be triggered due to the stability of H 1 and H 2 probes. The hairpin probe-protected AgNCs attached to the GO surface, efficiently quenching fluorescence of the AgNCs. Therefore, the system showed very low background. In presence of T HIV , the target triggered the chain-like assembly of H 1 and H 2 through HCR, generating a long chain of H 1 and H 2 complexes. The HCR product (AgNCs nanowires) could not be adsorbed on the surface of GO; hence, it generated a strong fluorescent signal based on the concentration of the target. Under the optimized conditions, the detection limit of the fluorescence sensor was 1.18nM, and hence it can be applied to clinical samples., (Copyright © 2016 Elsevier B.V. All rights reserved.)