3.4.1. Inhibition of *A. niger* Spores in Darkness

The antifungal activity of the original bamboo, TB, AB-10, AB-30, ATB-5, ATB-10, ATB-30, and ATB-200 and their inhibition ability against *A. niger* spores in the dark are shown in Figure 6. A U-shaped glass rod was used to support the test specimens on the mycelia-covered PDA substrates, preventing their direct contact with the spores. Only five days were required for the mycelia to grow over the entire surface of the original bamboo (Figure 6a, left), indicating that the original bamboo had no resistance to *A. niger*. Peculiarly, mycelia could grow well on the bamboo surface of the AB-10 sample after incubation for five days, even though many Ag NPs were coated on the bamboo surface (Figure 6b, left). Although we increased the concentration of [Ag(NH3)2] + ions to prepare more Ag NPs on the bamboo surface, the AB-30 could not inhibit the growth of mycelia completely after incubation for five days (Figure 6c). These results indicate that the AB samples had poor resistance to *A. niger*.

**Figure 6.** Antifungal properties of (**a**,**a1**) original bamboo (left) and TB (right), (**b**,**b1**) AB-10 (left) and ATB-5 (right), (**c**,**c1**) AB-30, (**d,d1**) ATB-10, (**e**,**e1**) ATB-30, and (**f**,**f1**) ATB-200 (left) and original bamboo (right) to inhibit *A. niger* growth in darkness. We can clearly see the mycelia in the red rectangle. Incubation period: (**a**–**f**) 5 days, (**a1**–**f1**) 28 days. TB: TiO2/bamboo, ATB-*x*: the Ag-NP-decorated TiO2/bamboo samples were denoted as ATB-*x*, with *x* representing the solution concentration (5, 10, 30, and 200 mM) of AgNO<sup>3</sup> as one of the raw materials, AB-*x*: the Ag-NP-decorated bamboo samples were denoted as AB-*x*, with *x* representing the solution concentration (10 and 30 mM) of AgNO<sup>3</sup> as one of the raw materials.

Our previous work similarly showed that nanosized Ag-treated bamboo samples have poor resistance to *P. citrinum and T. viride* [35]. In addition, we did not observe any mycelial growth on the surfaces of the TB, ATB-5, ATB-10, ATB-30, and ATB-200 samples after incubation for five days. After incubation for 28 days in the dark (Figure 6(a1–f1)), all samples displayed varying degrees of fungus infection. The surfaces of the original bamboo, AB-10, AB-30, TB, and ATB-200 were almost entirely covered with mycelia in the optical images (Figure 6), indicating that they had no resistance to *A. niger* in the dark. A few mycelia were directly observed on the surfaces of the ATB-5, ATB-10, and ATB-30 samples. Mycelia were mainly found on the side of the samples, especially in ATB-10 and ATB-30

samples. These results indicate that the ATB-5, ATB-10, and ATB-30 samples had a certain degree of resistance to *A. niger* in the dark. These observations suggest that the Ag/TiO<sup>2</sup> composite produces a synergistic antifungal effect that is unrelated to photoactivity.
