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This study investigated a selective and sensitive theragnosis system for the specific targeting of the membrane and nuclei based on visible-light and pH-responsive TiO2-integrated cross-linked carbon dot (C-CD/TiO2) for tumor detection and controllable photothermal therapy. The cross-linking system was formed by boronate ester linkages between the TiO2-immobilized Dopa-decyl (D-CD) and zwitterionic-formed CD (Z-CD) for nuclear targeting, which showed fluorescence “off” at physiological pH. The fluorescence recovered to the “on” state in acidic cancer cells owing to cleavages of the boronate ester bonds, resulting in the disruption of the Förster resonance energy transfer that generated different CDs useful for tumor-selective biosensors and therapy. D-CD, which is hydrophobic, can penetrate the hydrophobic sites of the cell membrane; it caused a loss in the hydrophobicity of these sites after visible-light irradiation. This was achieved by the photocatalytic activity of the TiO2modulating energy bandgap, whereas the Z-CD targeted the nucleus, as confirmed by merged confocal microscopy images. D-CD augmented by photothermal heat also exhibited selective anticancer activity in the acidic tumor condition but showed only minimal effects at a normal site at pH 7.4. After C-CD/TiO2injection to an in vivotumor model, C-CD/TiO2efficiently ablated tumors under NIR light irradiation. The C-CD/TiO2group showed up-regulation of the pro-apoptotic markers such as P53and BAXin tumor. This material exhibited its potential as a theragnostic sensor with excellent biocompatibility, high sensitivity, selective imaging, and direct anticancer activity via photothermal therapy.

As silicon-based metal oxide semiconductor field effect transistors get closer to their scaling limit, the importance of resistive random-access memory devices increases due to their low power consumption, high endurance and retention performance, scalability, and fast switching speed. In the last couple of years, organic–inorganic lead halide perovskites have been used for resistive switching applications, where they outperformed conventional metal oxides in terms of large on/off ratio and low power consumption. However, there were scarce reports on lead-free perovskites for such applications. In this report, we prepared lead-free Au/A3Bi2I9/Pt/Ti/SiO2/Si (A is either Cs+or Rb+) devices and tested their resistive switching characteristics. They showed a forming step prior to repeating switching, low operating voltage (0.09 V for Rb3Bi2I9and 0.1 V for Cs3Bi2I9), large on/off ratio (>107), relatively high endurance (200 cycles for Rb3Bi2I9and 400 cycles for Cs3Bi2I9cycles), and high retention (1000 s). Such low voltage could be explained by grain boundary-modulated ion drift. Difference in endurance was speculated to be due to the difference in the surface roughness of films because Cs3Bi2I9films are smoother. To get rid of the forming step, 10% of the Bi3+cations were substituted with Na+cations. However, this method only worked on Rb-based structures. This phenomenon was explained by the defect formation energy, which can only be negative in a corner-sharing Rb3Bi2I9structure compared to a face-sharing octahedral Cs3Bi2I9structure. As a result, the forming step was removed, and 100 cycles endurance and 1000 s retention performance were obtained. Similarly, the lower endurance is suspected to be due to the poor surface quality of the film.