In this work, 9-mesityl-10-methylacridinium ion (Acr-Mes) is found to act as an effective photocatalyst mimicking the function of oxidase. Upon visible light illumination, the excited Acr-Mes is able to exhibit superior enzymatic catalytic activity for small molecular substrates as well as protein biomacromolecule (cytochrome c). The experiment results demonstrate that the Acr-Mes oxidase mimic shows higher affinity to 3,3',5,5'-tetramethylbenzidine (TMB) than natural horseradish peroxidase or the reported molecule oxidase mimic. The reaction mechanism is ascribed to the strong oxidation property of the long-lived electron-transfer state (Acr-Mes) and the electron transfer from Acr-Mes radical to dissolved oxygen to generate superoxide radicals, which can easily oxidize various substrates. On the basis of these observations, the light-activatable Acr-Mes with an oxidase-like activity as the probe is utilized for cost-effective, sensitive, and highly selective colorimetric detection of two biothiols (L-cysteine and L-glutathione). The lowest detectable concentrations of L-Cys and L-GSH is 100 nM, which is lower than that of most of the reported methods for biothiols. Beyond this, we construct a series of visual molecular logic gates (AND, INH, and NOR) using the oxidase mimic-involved reaction systems.

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Despite some visual colorimetric chemical logic gates having been reported, a complete set of six basic logic gates have not been realized to date. Moreover, the application of the reported logic gates needs to be further extended. Herein, the label-free molybdenum oxide nanomaterials are presented for the construction of a new visual colorimetric molecular computing system. A complete set of six basic colorimetric logic gates (OR, AND, NOR, NAND, XOR, XNOR) and the INH logic gate are realized based on plasmonic switching in MoO nanomaterials. In addition, the rational integration of different logic gates into a 1:2 demultiplexer circuit is also testified.

The traditional nanozymes have low atom/ion utilization efficiency and are easily influenced by the size, morphology, as well as surface composition of nanomaterials. Herein, we report a template-free and valid approach to prepare a ferrous ion (Fe 2+ ) anchored onto the surface of the MoO 3 nanosheet (Fe 2+ /MoO 3 ) through coordination interaction between Fe 2+ and hydroxyl groups of MoO 3 . The resulting Fe 2+ /MoO 3 shows the peroxidase-like activity, and it can be utilized for catalytic decomposition of hydrogen peroxide (H 2 O 2 ) to generate hydroxyl radicals ( • OH) that oxidize various chromogenic substrates, generating distinct color change and strong ultraviolet− visible absorption. The Fe 2+ /MoO 3 peroxidase mimic exhibits a good thermal stability and works well at a high reaction temperature (95 °C) and has higher affinity for substrates than for natural horseradish peroxidase. Theoretical calculation results imply that the strong electrostatic field from the polarization charges between Fe 2+ and the MoO 3 nanosheet improves the reaction activity, which boosts the generation of • OH from H 2 O 2 . Using the Fe 2+ /MoO 3 peroxidase mimic-involved chromogenic system, we construct visual colorimetric assays for H 2 O 2 and triacetone triperoxide (TATP) explosives, which realize the visual detection of H 2 O 2 and TATP at concentrations of 40 and 60 μM, respectively.

We report a molybdenum oxide (MoO) nanomaterial-based three-input logic gate that uses Sn, NO, and H ions as inputs. Under acidic conditions, Sn is able to reduce MoO nanosheets, generating oxygen-vacancy-rich MoO nanomaterials along with strong localized surface plasmon resonance (LSPR) and an intense blue solution as the output signal. When NO is introduced, the redox reaction between the MoO nanosheets and Sn is strongly inhibited because the NO consumes both H and Sn. The three-input logic gate was employed for the visual colorimetric detection of Sn and NO under different input states. The colorimetric assay's limit of detection for Sn and the lowest concentration of NO detectable by the assay were found to be 27.5 nM and 0.1 μM, respectively. The assay permits the visual detection of Sn and NO down to concentrations as low as 2 μM and 25 μM, respectively. The applicability of the logic-gate-based colorimetric assay was demonstrated by using it to detect Sn and NO in several water sources.